Which Tow Vehicle

[Bob C]

Which vehicle to tow a glider trailer has been debated
ad nauseum on RAS. I have always been a staunch supporter
of towing with a full-size truck. After the events
of last Thursday, I feel my position is vindicated.

I was towing my sailplane westbound on Interstate 40
near Gallup, NM. I had just come through a nasty rain
& hail storm bad enough that traffic had been stopped
completely for several minutes. The worst part of
the storm passed quickly, but there was still moderate
rain as traffic began moving again. I was up to about
40 MPH when an eastbound GMC Yukon lost control and
spun into my westbound lane. I managed to get nearly
stopped before he spun head-on into me. Despite major
damage to both vehicles, all 7 occupants (me + 6 in
the Yukon) walked away completely unhurt! My sailplane
and trailer suffered absolutely no damage.

My wife arrived about 2 hours later with the backup
truck and I was able to continue to the airshow in
Kingman, AZ. A very thorough inspection of the sailplane
before assembly showed no indication at all of the
crash. The items in the seat pan were undisturbed,
the G-meter still showed the levels from my last aerobatic
flight and there wer no indications of any bumping
or scuffing anywhere on the wings or fuselage.

It was an emergency stop, downhill on very wet pavement.
About the worst possible scenario for a controlled
stop with a trailer. I hate to think what would have
happened if I'd been towing with a VW or Z3.

Here's the link to a photo of the crash (Mine is the
white Dodge, the trailer isn't visible in the photo).

http://www.silentwingsairshows.com/images/wreck.jpg

Despite the fact that he was driving a $40,000 Yukon,
the other driver had no insurance (or job, or phone
number, ...), so my uninsured motorist coverage will
cover the damages, while Mr. Ortega and family walk
away with nothing but a pair of citations for driving
too fast for conditions, and no insurance. I'm already
looking for another truck.

Bob C.

[[email protected]]

On Oct 9, 1:43 am, Bob C >
wrote:
> Which vehicle to tow a glider trailer has been debated
> ad nauseum on RAS. I have always been a staunch supporter
> of towing with a full-size truck. After the events
> of last Thursday, I feel my position is vindicated.
>
> I was towing my sailplane westbound on Interstate 40
> near Gallup, NM. I had just come through a nasty rain
> & hail storm bad enough that traffic had been stopped
> completely for several minutes. The worst part of
> the storm passed quickly, but there was still moderate
> rain as traffic began moving again. I was up to about
> 40 MPH when an eastbound GMC Yukon lost control and
> spun into my westbound lane. I managed to get nearly
> stopped before he spun head-on into me. Despite major
> damage to both vehicles, all 7 occupants (me + 6 in
> the Yukon) walked away completely unhurt! My sailplane
> and trailer suffered absolutely no damage.
>
> My wife arrived about 2 hours later with the backup
> truck and I was able to continue to the airshow in
> Kingman, AZ. A very thorough inspection of the sailplane
> before assembly showed no indication at all of the
> crash. The items in the seat pan were undisturbed,
> the G-meter still showed the levels from my last aerobatic
> flight and there wer no indications of any bumping
> or scuffing anywhere on the wings or fuselage.
>
> It was an emergency stop, downhill on very wet pavement.
> About the worst possible scenario for a controlled
> stop with a trailer. I hate to think what would have
> happened if I'd been towing with a VW or Z3.
>
> Here's the link to a photo of the crash (Mine is the
> white Dodge, the trailer isn't visible in the photo).
>
> http://www.silentwingsairshows.com/images/wreck.jpg
>
> Despite the fact that he was driving a $40,000 Yukon,
> the other driver had no insurance (or job, or phone
> number, ...), so my uninsured motorist coverage will
> cover the damages, while Mr. Ortega and family walk
> away with nothing but a pair of citations for driving
> too fast for conditions, and no insurance. I'm already
> looking for another truck.
>
> Bob C.

Bob glad to see that you are OK. does your trailer have brakes as
well? glad to hear that your glider is OK, that is a recurring
nightmare for me. one moron on the road is all it will take to
destroy my baby.

[Bert Willing[_2_]]

Probably exactly the same thing.

> On Oct 9, 1:43 am, Bob C >
> wrote:
>> It was an emergency stop, downhill on very wet pavement.
>> About the worst possible scenario for a controlled
>> stop with a trailer. I hate to think what would have
>> happened if I'd been towing with a VW or Z3.

[Bob C]

C'mon Bert, Newton says otherwise...Remember F=MA?
I'd bet lots that a VW or Z3 hit by a Yukon wouldn't
have fared so well. Also without the mass ahead of
it, the trailer would have seen a lot more of the energy.
Whatever...

BTW, no, the trailer did not have brakes. The surge
brake has been disabled. Because it's sure to bring
on a severe flaming, I won't go into the dynamics of
a fishtailing trailer and surge brakes, but in many
circumstances, surge brakes can actually make things
worse. PM me if you want to hear this one...

Bob C.


At 14:36 09 October 2007, Bert Willing wrote:
>Probably exactly the same thing.
>
>> On Oct 9, 1:43 am, Bob C
>> wrote:
>>> It was an emergency stop, downhill on very wet pavement.
>>> About the worst possible scenario for a controlled
>>> stop with a trailer. I hate to think what would have
>>> happened if I'd been towing with a VW or Z3.
>
>
>

[Andreas Maurer]

On 9 Oct 2007 14:50:54 GMT, Bob C
> wrote:


>BTW, no, the trailer did not have brakes. The surge
>brake has been disabled. Because it's sure to bring
>on a severe flaming, I won't go into the dynamics of
>a fishtailing trailer and surge brakes, but in many
>circumstances, surge brakes can actually make things
>worse. PM me if you want to hear this one...

Sounds interesting, Bob. How about sharing your experiences with the
group?
I certainly would never tow a trailer without a brake, but I'm always
interested in heraing other point of views. :)



Bye
Andreas

[Dan G]

In Len Deighton's astonishing 1970 novel "Bomber" there is a passage
(which I believe to be true, Deighton researched his novel to an
incredible degree) describing a pilot diving his Lancaster in the hope
that the increased airflow would extinguish the fire in one his
engines. He had been told of this technique by pilots who had
successfully done the same thing. However, the usual outcome was in
fact that the fire became hotter and eventually burned through the
main spar, leading to the seperation of the wing.

Those pilots did not get to report their experiences to their
colleagues.


Dan

[Eric Greenwell]

Bob C wrote:
> C'mon Bert, Newton says otherwise...Remember F=MA?

F=MA isn't so important if the M isn't used efficiently, which is true
of some trucks and SUVs. Sometimes bigger isn't better, it's just
bigger, and if the "M" makes for a high center of gravity, it can be
worse. Crash protection comes from putting the "M" in the right shape
and the right place, along with a good implementation of seat belts and
airbags.

> I'd bet lots that a VW or Z3 hit by a Yukon wouldn't
> have fared so well. Also without the mass ahead of
> it, the trailer would have seen a lot more of the energy.

Sure, but if it's a good trailer, the glider would still be undamaged.

> BTW, no, the trailer did not have brakes. The surge
> brake has been disabled. Because it's sure to bring
> on a severe flaming, I won't go into the dynamics of
> a fishtailing trailer and surge brakes, but in many
> circumstances, surge brakes can actually make things
> worse.

How long is your trailer, how much does it weigh, and why do you think
it might start fishtailing?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Mike the Strike]

Bob:

As a physicist, I am also a great believer in Newton's laws.

I once towed a trailer containing my Jantar-1 (19 meters) with a VW
bug, or rather I should say the trailer propelled my bug down the road
only marginally under control. I terminated that experiment very
quickly!

Since that attempt, I have used larger vehicles (station wagons in the
old days) or SUVs more recently.

I now use the moderately-sized Toyota 4Runner (Prado Land Cruiser to
the rest of the world), which has a V8 gasoline engine as an option
here in the USA. It's the perfect size, weight and power for towing a
single-place sailplane ( I tow a Discus 2). The standard gasoline
engine here or the diesel available in much of the rest of the world
would be OK at sea level, but in my view you need both sufficient mass
and power in the tow vehicle to maintain control and stability.

Yes, I know we'll get posts from the guys who'll tell us they towed
their Duo Discus over the alps using a Fiat 500. That doesn't meant
that it is necessarily a good idea!

Mike

[tommytoyz]

Bob,
You have to remember that your vehicle was badly damaged BECAUSE it
weighs so much. The frame of your vehicle had to absorb your weight. A
lighter vehicle would not have to absorb as much energy to come to s
stop, as it weighs less.

It doesn't matter if the vehicle hits an immovable object or if you
get hit by a moving object from the front. The calculation is the same
for your vehicle to come to s stop or decelerate. The mass your
vehicle plays a very important role and the heavier it is the more
energy needs to be absorbed and the more damage there will be.

So to compare the damage to your truck and say that this would happen
to a lighter vehicle is just plain wrong. A lighter vehicle would
sustain less damage is constructed the same as the truck.

The fact of the matter is though, that lighter newer vehicles can
absorb more energy per pound than heavier vehicles and thus would
sustain far less damage than a heavier vehicle.

I've seen a crash test of a smaller Renault against a Land Rover and
the Land Rover was in worse shape after the head on collision test -
especially the occupants.

So safety design and weight are the biggest factors in survivability.
All things being equal, it's safer to be in a lighter vehicle in a
crash as there is less energy for the frame to absorb.

The Ford F-150 is one example. And can your truck's roof even hold the
weight of the truck should it over turn? Light vehicles don't have
this problem and have a lower CG as well.

Your breaking power is also less than a lighter vehicle's - contrary
to what many may think, again because of the heavier weights. Stopping
distances are less in a lighter vehicle - always.

If the lighter tow vehicle has good breaks, like most modern smaller
cars do and good tires, that are not that much smaller than your truck
tires, say 15-17 inches , then a lighter car will stop much shorter
than your truck.

[Bill Daniels]

"Mike the Strike" > wrote in message
oups.com...
> Bob:
>
> As a physicist, I am also a great believer in Newton's laws.
>
> I once towed a trailer containing my Jantar-1 (19 meters) with a VW
> bug, or rather I should say the trailer propelled my bug down the road
> only marginally under control. I terminated that experiment very
> quickly!
>
> Since that attempt, I have used larger vehicles (station wagons in the
> old days) or SUVs more recently.
>
> I now use the moderately-sized Toyota 4Runner (Prado Land Cruiser to
> the rest of the world), which has a V8 gasoline engine as an option
> here in the USA. It's the perfect size, weight and power for towing a
> single-place sailplane ( I tow a Discus 2). The standard gasoline
> engine here or the diesel available in much of the rest of the world
> would be OK at sea level, but in my view you need both sufficient mass
> and power in the tow vehicle to maintain control and stability.
>
> Yes, I know we'll get posts from the guys who'll tell us they towed
> their Duo Discus over the alps using a Fiat 500. That doesn't meant
> that it is necessarily a good idea!
>
> Mike
>
My experience exactly. I started towing glider trailers with a 85hp Volvo
544 with drum brakes - really bad idea since the car self-destructed under
the stress of towing a trailer. My next car was a '66 Shelby 350 Mustang
with disk brakes. The 'stang worked OK but it was still way too light. It
made for FAST retrieves though.

In the early days a V8 Chevy BelAire station wagon was the ticket but
limited cooling capacity meant that on long uphill grades in the desert it
required shutting off the air conditioner, turning on the heater and
everybody leaning as far out the windows as possible to avoid being cooked.
On the downhill grades, you used the air conditioner as added compression to
save the brakes.

The long term experience in the western USA is that anything with a V8, disk
brakes and a BIG radiator works but anything less leads a short, ugly life.
Modern SUV's are politically incorrect but they sure work a lot better than
what we used to have.

Bill Daniels

[[email protected]]

On Oct 8, 11:43 pm, Bob C
> wrote:
> Which vehicle to tow a glider trailer has been debated
> ad nauseum on RAS. I have always been a staunch supporter
> of towing with a full-size truck. After the events
> of last Thursday, I feel my position is vindicated.
>
> I was towing my sailplane westbound on Interstate 40
> near Gallup, NM. I had just come through a nasty rain
> & hail storm bad enough that traffic had been stopped
> completely for several minutes. The worst part of
> the storm passed quickly, but there was still moderate
> rain as traffic began moving again. I was up to about
> 40 MPH when an eastbound GMC Yukon lost control and
> spun into my westbound lane. I managed to get nearly
> stopped before he spun head-on into me. Despite major
> damage to both vehicles, all 7 occupants (me + 6 in
> the Yukon) walked away completely unhurt! My sailplane
> and trailer suffered absolutely no damage.
>
> My wife arrived about 2 hours later with the backup
> truck and I was able to continue to the airshow in
> Kingman, AZ. A very thorough inspection of the sailplane
> before assembly showed no indication at all of the
> crash. The items in the seat pan were undisturbed,
> the G-meter still showed the levels from my last aerobatic
> flight and there wer no indications of any bumping
> or scuffing anywhere on the wings or fuselage.
>
> It was an emergency stop, downhill on very wet pavement.
> About the worst possible scenario for a controlled
> stop with a trailer. I hate to think what would have
> happened if I'd been towing with a VW or Z3.
>
> Here's the link to a photo of the crash (Mine is the
> white Dodge, the trailer isn't visible in the photo).
>
> http://www.silentwingsairshows.com/images/wreck.jpg
>
> Despite the fact that he was driving a $40,000 Yukon,
> the other driver had no insurance (or job, or phone
> number, ...), so my uninsured motorist coverage will
> cover the damages, while Mr. Ortega and family walk
> away with nothing but a pair of citations for driving
> too fast for conditions, and no insurance. I'm already
> looking for another truck.
>
> Bob C.

Bob, Glad you're okay. That must have been pretty scary. (in any
vehicle)

Bob

[Tom Gardner]

On Oct 9, 11:00 pm, tommytoyz > wrote:
> Bob,
> You have to remember that your vehicle was badly damaged BECAUSE it
> weighs so much. The frame of your vehicle had to absorb your weight. A
> lighter vehicle would not have to absorb as much energy to come to s
> stop, as it weighs less.

And absorbing energy the principal reason why, in a crash, it is
better to be in a steel vehicle than aluminium, and GRP or composites
are worst of all. After all, we sit on energy absorbing cushions for a
very good reason.

> It doesn't matter if the vehicle hits an immovable object or if you
> get hit by a moving object from the front. The calculation is the same
> for your vehicle to come to s stop or decelerate. The mass your
> vehicle plays a very important role and the heavier it is the more
> energy needs to be absorbed and the more damage there will be.

While true, that's only half the story. If you remember you schoolboy/
girl physics, you will realise that in a collision kinetic energy is
*not* conserved whereas momentum *is* conserved. (The "missing" energy
appears as heat and sound :)

So what?

Well, if you think through what happens in a collision between
vehicles with different mass, and use conservation of momentum, then
the lighter vehicle will experience a greater delta-v than a heavier
vehicle. And consequently the lighter vehicle will also experience a
larger acceleration than the heavier vehicle. That's rather important
to the occupants, since it is principally the acceleration that
determines how much brain damage they sustain.


> So to compare the damage to your truck and say that this would happen
> to a lighter vehicle is just plain wrong. A lighter vehicle would
> sustain less damage is constructed the same as the truck.

Yes, but what about the occupants?

> The fact of the matter is though, that lighter newer vehicles can
> absorb more energy per pound than heavier vehicles and thus would
> sustain far less damage than a heavier vehicle.

Why is that? I've no reason to doubt you, but why?

> I've seen a crash test of a smaller Renault against a Land Rover and
> the Land Rover was in worse shape after the head on collision test -
> especially the occupants.
>
> So safety design and weight are the biggest factors in survivability.
> All things being equal, it's safer to be in a lighter vehicle in a
> crash as there is less energy for the frame to absorb.

That's the first time I have seen that statement.

> The Ford F-150 is one example. And can your truck's roof even hold the
> weight of the truck should it over turn? Light vehicles don't have
> this problem and have a lower CG as well.

Probably true, and important in some cases.

> Your breaking power is also less than a lighter vehicle's - contrary
> to what many may think, again because of the heavier weights. Stopping
> distances are less in a lighter vehicle - always.
>
> If the lighter tow vehicle has good breaks,

Highly ambiguous in this context :) I think you mean "brakes"!

> like most modern smaller
> cars do and good tires, that are not that much smaller than your truck
> tires, say 15-17 inches , then a lighter car will stop much shorter
> than your truck.

Maybe true, but the car's stopping distance isn't the only
consideration.

[tommytoyz]

There are many crash instances where a light lower vehicle will be
fatal where a higher sitting one wouldn't. But there are also
situations where a large top heavy one weighing a lot will be worse.
It all just depends on the crash situation.

Bill, your experiences are with much older vehicles and not with
modern compact tow cars. I'd much rather hit a wall, tree, ditch or
whatever in a smaller tow vehicle than in a big SUV.

As to engine cooling capacity, I've towed for thousands of miles
including in the desert in summer and up grades in NM in summer with a
Honda Accord 5 speed and have never had to even shut the AC off.

It's relative colling capacity that matters. Smaller engines just
don't need huge V-8 radiators to cool just as well. Maybe better as
they pull a lot less weight.

The crash test comparison between a Mini Cooper and an F-150 pretty
well says it all for me. I especially feel safer on tight downhill
grades in a smaller vehicle as it is easier to control. Though I
wouldn't want an SUV or Semi to fall over on top of me. That would be
bad and make me wish for the SUV in that scenario.

[BT]

I had a Ford Ranger 4L V6 auto, ext cab, it was marginal for a heavy factory
Grob trailer
My new 07 Toyota Tundra 5.7L Double Cab does not even notice the LS-4 in the
trailer

BT

"Mike the Strike" > wrote in message
oups.com...
> Bob:
>
> As a physicist, I am also a great believer in Newton's laws.
>
> I once towed a trailer containing my Jantar-1 (19 meters) with a VW
> bug, or rather I should say the trailer propelled my bug down the road
> only marginally under control. I terminated that experiment very
> quickly!
>
> Since that attempt, I have used larger vehicles (station wagons in the
> old days) or SUVs more recently.
>
> I now use the moderately-sized Toyota 4Runner (Prado Land Cruiser to
> the rest of the world), which has a V8 gasoline engine as an option
> here in the USA. It's the perfect size, weight and power for towing a
> single-place sailplane ( I tow a Discus 2). The standard gasoline
> engine here or the diesel available in much of the rest of the world
> would be OK at sea level, but in my view you need both sufficient mass
> and power in the tow vehicle to maintain control and stability.
>
> Yes, I know we'll get posts from the guys who'll tell us they towed
> their Duo Discus over the alps using a Fiat 500. That doesn't meant
> that it is necessarily a good idea!
>
> Mike
>
>

[tommytoyz]

Tom,
You are correct about the higher deceleration forces of a lighter
vehicle when it crashes head on with a heavier vehicle, due to the
larger inertia of the heavier one.

But it does not mean that the occupants of the heavier are safer, as
their structure may experience more damage, so it's hard to really
tell what would happen and I would say one would have to examine the
overall safety and design of each vehicle, like we compare the sink
measurements of each glider. An ASW 17 for instance is not necessarily
better than an 18 Meter ship, etc....or even perhaps a 15m Diana -2 at
certain speeds.

http://www.bridger.us/2002/12/16/CrashTestingMINICooperVsFordF150

Size is not all that matters but design. And yes, I meant
brakes.........my bad......

[Tom Gardner[_1_]]

tommytoyz > wrote in
ups.com:

> You are correct about the higher deceleration forces of a lighter
> vehicle when it crashes head on with a heavier vehicle, due to the
> larger inertia of the heavier one.

The deceleration forces are an extremely important
factor in the survivability of any accident. Consider
that the brain has the consistency of blancmange, and
imagine how easy it is to disrupt internal connections.
Or get an animal's brain from the butchers (if that's
possible any more :), and just play around with it.

> But it does not mean that the occupants of the heavier are safer, as
> their structure may experience more damage,

To some extent more damage to the structure leads
to less damage to the occupants: energy is required
to deform the structure, and that energy then can't
be dissipated in the occupants. That's one essential
reason why car's "crumple zones" are so important.

The worst case would be a light vehicle that
didn't crumple or otherwise absorb energy in
a smooth fashion.

> so it's hard to really
> tell what would happen and I would say one would have to examine the
> overall safety and design of each vehicle,

I certainly agree with that, and I'm sure we both
acknowledge that it is a very difficult topic.

> like we compare the sink
> measurements of each glider. An ASW 17 for instance is not necessarily
> better than an 18 Meter ship, etc....or even perhaps a 15m Diana -2 at
> certain speeds.
>
> http://www.bridger.us/2002/12/16/CrashTestingMINICooperVsFordF150

Interesting article. Shows the crumple zone
quite nicely. I'd still looks like that, on
balance, smaller cars fare worse. But there
are notable exceptions - see you next statement.

> Size is not all that matters but design.

When size is constant, design matters. When
design is constant, size matters. Which is
more important? I wouldn't like to say. But
all other things being equal (ha!), I'd rather
be in a larger vehicle than a smaller one
(so long as it doesn't roll :)

Having said that, I drive a "subcompact" car ;)

> And yes, I meant brakes.........my bad......

I've never made such a mistake. Never. Oh no. :)

[Martin Gregorie[_1_]]

tommytoyz wrote:
>
> I've seen a crash test of a smaller Renault against a Land Rover and
> the Land Rover was in worse shape after the head on collision test -
> especially the occupants.
>
If that was a series 1,2 or 3 Landrover its not at all surprising
because these models had almost no energy absorbing capability: that
beam across the rear is the rear chassis member and the front bumper may
look strong, but its bolted directly onto the main chassis box members.
I owned a series 2a long wheelbase model and was told that, if I had to
hit anything, to make sure I hit it square on because anything else
would twist the chassis. As a result, Landrovers are not as tough as
they look.

The same would apply to all vehicles with similar construction, i.e. it
probably applies to most of the earlier jeeps too.

I don't know how the later Landrover chassis is built, but wouldn't be
surprised if this also applied to the series 4 and Defender models. I
think Rangies and Freeloaders have enough additional fancy stuff round
the front end to absorb at least some energy.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Tom Gardner]

On Oct 10, 9:47 pm, Martin Gregorie >
wrote:
> tommytoyz wrote:
> > I've seen a crash test of a smaller Renault against a Land Rover and
> > the Land Rover was in worse shape after the head on collision test -
> > especially the occupants.
>
> If that was a series 1,2 or 3 Landrover its not at all surprising
> because these models had almost no energy absorbing capability: that
> beam across the rear is the rear chassis member and the front bumper may
> look strong, but its bolted directly onto the main chassis box members.

They had a neat simple and foolproof design principle for
minimising the damage to the car when travelling over rough
terrain. The stiff suspension caused the occupants to
bounce around so much that they would voluntarily keep the speed
below that at which the car would be damaged. Well, I'm sure
there's an element of truth to that anyway, particularly without
seatbelts.

The Land Rover's crumple zone was built into the other
vehicle, of course.

> I owned a series 2a long wheelbase model and was told that, if I had to
> hit anything, to make sure I hit it square on because anything else
> would twist the chassis. As a result, Landrovers are not as tough as
> they look.

Yes, but they would still get you home even with a twisted chassis.
And the chassis could be repaired by the local blacksmith.

[Tom Gardner]

On Oct 10, 9:47 pm, Martin Gregorie >
wrote:
> tommytoyz wrote:
> > I've seen a crash test of a smaller Renault against a Land Rover and
> > the Land Rover was in worse shape after the head on collision test -
> > especially the occupants.
>
> If that was a series 1,2 or 3 Landrover its not at all surprising
> because these models had almost no energy absorbing capability: that
> beam across the rear is the rear chassis member and the front bumper may
> look strong, but its bolted directly onto the main chassis box members.

They used a simple design principle to limit damage to the vehicle
when travelling over rough terrain. A stiff suspension ensured the
occupants realised they were more fragile than the vehicle, so they
instinctively kept the speed down. It is especially effective if the
driver is tall and there aren't any seatbelts.

Of course the Land Rover's crumple zone was built into the other
vehicle.

> I owned a series 2a long wheelbase model and was told that, if I had to
> hit anything, to make sure I hit it square on because anything else
> would twist the chassis. As a result, Landrovers are not as tough as
> they look.

Yes, but they would get you home even with a twisted chassis, and the
local blacksmith could bend it back into shape.

There was quite a lot of controversy, IIRC, about the decision for the
later models to have coil springs instead of leaf springs. It is much
easier to repair/replace a leaf spring after it has broken.

[Martin Gregorie[_1_]]

Tom Gardner wrote:
>
> They had a neat simple and foolproof design principle for
> minimising the damage to the car when travelling over rough
> terrain. The stiff suspension caused the occupants to
> bounce around so much that they would voluntarily keep the speed
> below that at which the car would be damaged. Well, I'm sure
> there's an element of truth to that anyway, particularly without
> seatbelts.
>
My Rover xc manual advised always wearing a seat belt when going off
road "because it stops your head from hitting the roof so often".

In any case, any one thinking of serious off-road in a long wheel-base
machine replaced the rear springs with the HD units.

> The Land Rover's crumple zone was built into the other
> vehicle, of course.
>
Too true.

> Yes, but they would still get you home even with a twisted chassis.
> And the chassis could be repaired by the local blacksmith.
>
I'd never knock the series II or III. Mine did a London-India out and
return in 10 months without any problems apart from a tendency to
consume speedometers that I never got to the bottom of, a clutch change
in Mysore and a clutch slave cylinder replacement in Turkey.

It was a simple machine and easy to maintain with relatively few tools:
almost everything could be removed and reinstalled with only 3 or 4
different ring spanners and a screwdriver.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[[email protected]]

On Oct 9, 5:30 pm, Mike the Strike > wrote:
> Bob:
>
> As a physicist, I am also a great believer in Newton's laws.
>
> I once towed a trailer containing my Jantar-1 (19 meters) with a VW
> bug, or rather I should say the trailer propelled my bug down the road
> only marginally under control. I terminated that experiment very
> quickly!
>
> Since that attempt, I have used larger vehicles (station wagons in the
> old days) or SUVs more recently.
>
> I now use the moderately-sized Toyota 4Runner (Prado Land Cruiser to
> the rest of the world), which has a V8 gasoline engine as an option
> here in the USA. It's the perfect size, weight and power for towing a
> single-place sailplane ( I tow a Discus 2). The standard gasoline
> engine here or the diesel available in much of the rest of the world
> would be OK at sea level, but in my view you need both sufficient mass
> and power in the tow vehicle to maintain control and stability.
>
> Yes, I know we'll get posts from the guys who'll tell us they towed
> their Duo Discus over the alps using a Fiat 500. That doesn't meant
> that it is necessarily a good idea!
>
> Mike

Sadly, some of us remember what a Fiat 500 is (I even owned one)...
See ya, Dave "YO"

[Marc Ramsey[_2_]]

wrote:
> Sadly, some of us remember what a Fiat 500 is (I even owned one)...
> See ya, Dave "YO"

Cheer up! Fiat has started making them again, there is even talk of
bringing them to the US to compete with the Mini. Should be perfect for
towing around an Antares...

[Dan G]

On Oct 9, 10:30 pm, Mike the Strike > wrote:
> Yes, I know we'll get posts from the guys who'll tell us they towed
> their Duo Discus over the alps using a Fiat 500. That doesn't meant
> that it is necessarily a good idea!

Nobody has ever suggested that - I believe that is a "strawman"
argument.

Towing is simple. Follow these rules, and your rig will be stable in
all conditions and not need stabiliser hitch.

*Make sure that the laden mass of the trailer does not exceed 85% of
the laden mass of the tow car, and preferably less.

*Have 7% of the trailer's actual mass on the hitch. Measure with some
bathroom scales and a length of wood cut to the correct height to fit
between hitch and the scales. It's important to get this number right
- no more, no less. If the 7% value is more than the car's noseweight
limit, you'll just have to keep within that limit and accept a less
than optimum noseweight.

*Carry heavy items in the car, not the trailer, but make sure you
don't exceed the maximum axle load (or end up with your car dragging
its arse along the road). I often put the heaviest
items in the passenger footwell if I'm travelling alone.

*Look after your tyres on both car and trailer. Blow-outs can really
ruin your trip (and your glider!). Trailer tyres should be replaced
every five years and definitely every seven - rubber ages naturally,
whether you use them or not. In winter ideally take the wheels off
and
store them level in a cool dry place wrapped in hessian (not
plastic),
or at least wrap the tyres in hessian on the trailer to keep the UV
off.

*Make sure you run the correct tyre pressures all round. Check before
you set off on every trip. A tyre with low pressure will run hot and
could blow.

Now, I didn't want to mention this earlier as it sounds like willy-
waving, but I once performed a maximum-effort stop from 70 mph in a
light Euro car with an Astir on the back in pretty old trailer (no
Cobra). The car and trailer were well maintained and pulled-up very
quickly in a perfectly straight line. I could have probably let go of
the wheel.


Dan

[Dan G]

On Oct 10, 12:01 am, Tom Gardner > wrote:
> And absorbing energy the principal reason why, in a crash, it is
> better to be in a steel vehicle than aluminium, and GRP or composites
> are worst of all. After all, we sit on energy absorbing cushions for a
> very good reason.

NO. That's utter rubbish (and sounds a little like Airbus's anti-787
FUD!). Safest cars in the world are Formula 1 cars - 100% carbon
fibre.

Crash-worthiness and energy absorbtion is ENTIRELY down to design, not
material.


Dan

[Dan G]

On Oct 10, 12:01 am, Tom Gardner > wrote:
> Well, if you think through what happens in a collision between
> vehicles with different mass, and use conservation of momentum, then
> the lighter vehicle will experience a greater delta-v than a heavier
> vehicle. And consequently the lighter vehicle will also experience a
> larger acceleration than the heavier vehicle. That's rather important
> to the occupants, since it is principally the acceleration that
> determines how much brain damage they sustain.

That's not correct either. The human body can survive an instant peak
G of about 150 (the known record is 180, David Purely in a F1 car in
1977, who did 108-0 mph in 26"). What kills you in crash is the
collapse of your "survival space", i.e. broken bones, crushing
injuries, smashing your head on the wheel etc.

As the link to the Mini vs. F150 test shows, design is paramount, and
that's something most large US SUVs are all too lacking.


Dan

[Tom Gardner]

Dan G wrote:
> On Oct 10, 12:01 am, Tom Gardner > wrote:
> > And absorbing energy the principal reason why, in a crash, it is
> > better to be in a steel vehicle than aluminium, and GRP or composites
> > are worst of all. After all, we sit on energy absorbing cushions for a
> > very good reason.
>
> NO. That's utter rubbish (and sounds a little like Airbus's anti-787
> FUD!).

Well, I'm not going to discuss your strawman point and attempt to
justify an Airbus statement

> Safest cars in the world are Formula 1 cars - 100% carbon
> fibre.

That's a great soundbite, but I'm sure it is both true and false
depending on what is meant by "safest" and whether or not all the
other factors in an accident are included.

> Crash-worthiness and energy absorbtion is ENTIRELY down to design, not
> material.

Well, if design includes the choice of material (as it should) then we
can agree. But to claim that materials are irrelevant is, how shall I
put it, over-egging the cake a bit.

[Tom Gardner]

Dan G wrote:
> On Oct 10, 12:01 am, Tom Gardner > wrote:
> > Well, if you think through what happens in a collision between
> > vehicles with different mass, and use conservation of momentum, then
> > the lighter vehicle will experience a greater delta-v than a heavier
> > vehicle. And consequently the lighter vehicle will also experience a
> > larger acceleration than the heavier vehicle. That's rather important
> > to the occupants, since it is principally the acceleration that
> > determines how much brain damage they sustain.
>
> That's not correct either. The human body can survive an instant peak
> G of about 150 (the known record is 180, David Purely in a F1 car in
> 1977, who did 108-0 mph in 26").

It is always possible to find an exceptional case to prove or disprove
any contention.

Exceptional cases are not a good basis on which to make designs (or
legislation for that matter). It is better to concentrate on the
common circumstances first.

> What kills you in crash is the
> collapse of your "survival space", i.e. broken bones, crushing
> injuries, smashing your head on the wheel etc.

If that is the case then crumple zones are a waste of time and all
that is necessary is ensure that the cabin is so strong it won't
deform. And since motor cyclists aren't in any confined survival
space, their accidents are clearly more survivable.

> As the link to the Mini vs. F150 test shows, design is paramount, and
> that's something most large US SUVs are all too lacking.

Materials are part of design. And I've no intention of defending any
SUV's design.

[Eric Greenwell]

Dan G wrote:
> Crash-worthiness and energy absorbtion is ENTIRELY down to design, not
> material.

The major glider manufacturers don't agree with this: take look at the
cockpit of a Schleicher glider, for example, and see how little of it is
carbon fiber. Aramids and glass fiber absorb energy better than carbon
fiber, and so a designer will use them if it is possible.

Nonetheless, it is wrong to claim (as did Tom G) that a steel structure
is always better than one of aluminum or composite, as the design can
compensate for properties of the other materials.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

Tom Gardner wrote:

> And absorbing energy the principal reason why, in a crash, it is
> better to be in a steel vehicle than aluminium, and GRP or composites
> are worst of all.

Design of the structure is extremely important, as are the other safety
devices, so a blanket statement like this is wrong. Take a look at the
large variations in crash protection provided by similar all-steel
vehicles - if it were primarily materials used, there wouldn't be such
differences.

> After all, we sit on energy absorbing cushions for a
> very good reason.

The reason is the very limited crush space available below the seat, not
the materials used. The manufacturers work to improve this situation by
providing taller landing gear designed to collapse in a controlled
fashion, to absorb as much energy as possible. This one reason why most
(maybe all - I don't know of an exception) flight manuals tell you to
never land gear down.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Paul Hanson]

>(maybe all - I don't know of an exception) flight manuals
>tell you to
>never land gear down.
>
Uhh, gear up you mean? : ) There are exceptions however,
like in a water landing for instance. You don't want
the gear down as it causes the glider to violently
pitch down and submarine on touch...err-splashdown,
greatly increasing the risk of smashing into the lake/river/ocean
bottom and/or drowning.
Uncle Hank where are you?
Another exception is my Sisu 1a. It has a shock absorbing
oak skid with a steel shoe, in addition to a retractable
main. If the field looks to cloddy or the grass too
tall it is recommended not to lower the gear. AJ Smith
gave it it's first wheel up (unintentional however)
and Johnson the second, both without damage to them
or the ship. But landing gear up is generally a bad
habit, for many reasons, including having a crumple
zone.

Paul Hanson
"Do the usual, unusually well"--Len Niemi

[bumper]

"Tom Gardner" > wrote in message
ups.com...
>

>>
>> That's not correct either. The human body can survive an instant peak
>> G of about 150 (the known record is 180, David Purely in a F1 car in
>> 1977, who did 108-0 mph in 26").
>
> It is always possible to find an exceptional case to prove or disprove
> any contention.



All this talk about big vs. little (g). Here's a short clip that pretty much
proves something or another . . .

bumper

http://www.youtube.com/watch?v=lAfZ1N56qjY

[John Galloway[_1_]]

Just for interest:

http://www.youtube.com/watch?v=86M_fV-1yKY

[John Smith]

bumper wrote:

> All this talk about big vs. little (g). Here's a short clip that pretty much
> proves something or another . . .

> http://www.youtube.com/watch?v=lAfZ1N56qjY

And here's what happens when you try to make an evasive maneuvre with a
SUV...

http://www.youtube.com/watch?v=dIEnQFpMj2Q&NR=1

[tommytoyz]

Another interesting series of tests with SUVs. In my opinion, large
doors and large "soft" spots in large SUV's do not make them safer.
Look at the pictures and the results, especially in side impact.

http://www.msnbc.msn.com/id/21228894/

The fact that SUVs are also heavier and thus, due to their higher
inertia and mass, will incur even more damage than a smaller car -
which will bounce somewhat and in any case have to absorb less energy
from its own mass, speaks against the safety of the larger vehicles in
a side impact. If the SUV flips as well, it's all over for the
occupants in most SUVs, thoufg not in cars.

My main point here, is that SUVs are not safer nor better as tow
vehicles. They may feel safer, but are they really? The tests show
that it is not always the case.

[Nyal Williams]

At 17:54 11 October 2007, John Smith wrote:
>bumper wrote:
>
>> All this talk about big vs. little (g). Here's a short
>>clip that pretty much
>> proves something or another . . .
>
>> http://www.youtube.com/watch?v=lAfZ1N56qjY
>
>And here's what happens when you try to make an evasive
>maneuvre with a
>SUV...
>
>http://www.youtube.com/watch?v=dIEnQFpMj2Q&NR=1

Short wheel base, high center of gravity. Wonder how
this vehicle compares to the Renault in that respect.
>

[Bill Daniels]

It is said that one of the Naderite early advocates of air bag technology
remarked that, "Given the fact that the death rate did not drop nearly as
much as we had expected because drivers adjusted their driving style to be
more aggressive in the belief that they were totally protected by air bags,
it might have been more effective to have mounted a bayonet on the steering
column aimed at their hearts." "That way, knowing that instant death would
follow any collision, they would have been more careful."
Bill Daniels



"Nyal Williams" > wrote in message
...
> At 17:54 11 October 2007, John Smith wrote:
>>bumper wrote:
>>
>>> All this talk about big vs. little (g). Here's a short
>>>clip that pretty much
>>> proves something or another . . .
>>
>>> http://www.youtube.com/watch?v=lAfZ1N56qjY
>>
>>And here's what happens when you try to make an evasive
>>maneuvre with a
>>SUV...
>>
>>http://www.youtube.com/watch?v=dIEnQFpMj2Q&NR=1
>
> Short wheel base, high center of gravity. Wonder how
> this vehicle compares to the Renault in that respect.
>>
>
>
>

[Eric Greenwell]

Dan G wrote:

>
> *Have 7% of the trailer's actual mass on the hitch. Measure with some
> bathroom scales and a length of wood cut to the correct height to fit
> between hitch and the scales. It's important to get this number right
> - no more, no less. If the 7% value is more than the car's noseweight
> limit, you'll just have to keep within that limit and accept a less
> than optimum noseweight.

We've discussed this one before, and there is no evidence suggesting 7%
is appropriate for glider trailers, as the number comes from a study of
caravans (travel trailers). The more common numbers are 10%-15%, also
with the requirement to stay within the vehicle and hitch load
specifications.

The list does not include the most important factor: speed. Every tow
vehicle and trailer is stable below some speed; unfortunately, there
isn't any safe and easy way to determine this that I know of. I do
suspect most trailer accidents from loss of control could be avoided if
the driver had paid attention to signs of instability in the past, and
drove more slowly as a result.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

Paul Hanson wrote:
>> (maybe all - I don't know of an exception) flight manuals
>> tell you to
>> never land gear down.
>>
> Uhh, gear up you mean? : )

Oops!

> There are exceptions however,
> like in a water landing for instance. You don't want
> the gear down as it causes the glider to violently
> pitch down and submarine on touch...err-splashdown,
> greatly increasing the risk of smashing into the lake/river/ocean
> bottom and/or drowning.

The opposite is actually true; for example, my 12 year old ASH 26 E
manual specifically states a water landing requires the gear down for
maximum safety. Tests show the typical glider fuselage will submarine
with the gear up; with the gear down, it does not submerge as much, and
the gear protects the pilot from any impact with the bottom.

It is possible that flight manuals from older gliders (older than 20
years, say) might suggest landing in water with the gear up - I can't
recall when the water landing research was done.

> Uncle Hank where are you?
> Another exception is my Sisu 1a. It has a shock absorbing
> oak skid with a steel shoe, in addition to a retractable
> main. If the field looks to cloddy or the grass too
> tall it is recommended not to lower the gear. AJ Smith
> gave it it's first wheel up (unintentional however)
> and Johnson the second, both without damage to them
> or the ship. But landing gear up is generally a bad
> habit, for many reasons, including having a crumple
> zone.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[01-- Zero One]

Hmmm... where to begin in response to this, Dan. First you claim that a
previous poster was using a "strawman" argument and then you immediately
begin to use the Reductive Fallacy (oversimplification) argument.



It would be nice if we could apply a few simple rules to any problem and
have it solved. However, a vehicle towing a trailer is a _very_ complex
system requiring much more than a few "shoulds" or "Do these x things
and everything will be fine" approaches. In addition to the obvious
things that have been written about in this thread (vehicle weights,
tongue weights, tires and tire pressures, etc.) there are _many_ other
significant factors in play. To name a few (very incomplete list):



--moment arm of the hitch ball to rear axle of the car (one of the most
significant from my experience)

--suspension dynamics of tow vehicle

--aerodynamic shape of the trailer

--combined aerodynamic interactions between tow vehicle and trailer

--environmental considerations where you tow ( prevailing wind, etc.)

--proximity to field effects of passing vehicles, etc.

--necessary or desired speed for trip

-- on and on.......



So to say that "Towing is simple. Follow these rules, and your rig will
be stable in all conditions and not need stabiliser hitch." is in my
experience a gross oversimplification.



Larry

"zero one"

USA















"Dan G" > wrote in message
ups.com:

> On Oct 9, 10:30 pm, Mike the Strike > wrote:
> > Yes, I know we'll get posts from the guys who'll tell us they towed
> > their Duo Discus over the alps using a Fiat 500. That doesn't meant
> > that it is necessarily a good idea!
>
> Nobody has ever suggested that - I believe that is a "strawman"
> argument.
>
> Towing is simple. Follow these rules, and your rig will be stable in
> all conditions and not need stabiliser hitch.
>
> *Make sure that the laden mass of the trailer does not exceed 85% of
> the laden mass of the tow car, and preferably less.
>
> *Have 7% of the trailer's actual mass on the hitch. Measure with some
> bathroom scales and a length of wood cut to the correct height to fit
> between hitch and the scales. It's important to get this number right
> - no more, no less. If the 7% value is more than the car's noseweight
> limit, you'll just have to keep within that limit and accept a less
> than optimum noseweight.
>
> *Carry heavy items in the car, not the trailer, but make sure you
> don't exceed the maximum axle load (or end up with your car dragging
> its arse along the road). I often put the heaviest
> items in the passenger footwell if I'm travelling alone.
>
> *Look after your tyres on both car and trailer. Blow-outs can really
> ruin your trip (and your glider!). Trailer tyres should be replaced
> every five years and definitely every seven - rubber ages naturally,
> whether you use them or not. In winter ideally take the wheels off
> and
> store them level in a cool dry place wrapped in hessian (not
> plastic),
> or at least wrap the tyres in hessian on the trailer to keep the UV
> off.
>
> *Make sure you run the correct tyre pressures all round. Check before
> you set off on every trip. A tyre with low pressure will run hot and
> could blow.
>
> Now, I didn't want to mention this earlier as it sounds like willy-
> waving, but I once performed a maximum-effort stop from 70 mph in a
> light Euro car with an Astir on the back in pretty old trailer (no
> Cobra). The car and trailer were well maintained and pulled-up very
> quickly in a perfectly straight line. I could have probably let go of
> the wheel.
>
>
> Dan

[Tom Gardner[_1_]]

Martin Gregorie > wrote in news:kg50u4-
:

> I'd never knock the series II or III. Mine did a London-India out and
> return in 10 months without any problems apart from a tendency to
> consume speedometers that I never got to the bottom of, a clutch change
> in Mysore and a clutch slave cylinder replacement in Turkey.

I had a series II with a 4litre perkins diesel engine.
Yes, it would pull the skin off custard, and yes the
engine mountings and transmission spiders were problematical.
Never had any problem with the speedo, but the fuel guage
was calibrated in Roentgens per hour (that being the best
one I could lay my hands on at the time :)

> It was a simple machine and easy to maintain with relatively few tools:
> almost everything could be removed and reinstalled with only 3 or 4
> different ring spanners and a screwdriver.

Mine seemed to have a lot of parts in common with Minis,
e.g. rear lights and driver's seat.

[Udo]

Larry, I agree.
I drove at one point an extended version of the old Aero Star. This
combination was good for about 60m/h max no wind, with the same sort
of trailers I am towing now. This was ok for the odd retrieve and
contest.


The points you raised were also the things I was looking for in a new
Mini Van. But only one Mini Van met those criteria, the Honda Odyssey.
Low C of G, short coupled between ball hitch and rear independent
suspension. Powerful and fun to drive, comfortable and reasonably good
on gas. In any case I found it handled the Schreder trailer as well as
a Cobra unit, The Schreder trailer Van combination use more gas then
the cobra trailer combo.

With the currant cobra trailer I noted a difference, even though this
one is newer and has shocks. It was not as stable as the other cobra
trailer. Lucky for me I marked my drive way for my first cobra
trailer wheels. I noticed that the trailer was to close to the
garage door. It turns out the wheels are to far forward by at least
10". Also the trailer hitch would not stay down when the trailer is
empty, which all other trailers did with about 15 lb down force
empty. I think that would explain the slightly less stable set-up
In time I will move the axle.

Udo


> and everything will be fine" approaches. In addition to the obvious
> things that have been written about in this thread (vehicle weights,
> tongue weights, tires and tire pressures, etc.) there are _many_ other
> significant factors in play. To name a few (very incomplete list):
>
> --moment arm of the hitch ball to rear axle of the car (one of the most
> significant from my experience)
>
> --suspension dynamics of tow vehicle
>
> --aerodynamic shape of the trailer
>
> --combined aerodynamic interactions between tow vehicle and trailer
>
> --environmental considerations where you tow ( prevailing wind, etc.)
>
> --proximity to field effects of passing vehicles, etc.
>
> --necessary or desired speed for trip
>
> -- on and on.......
>
> So to say that "Towing is simple. Follow these rules, and your rig will
> be stable in all conditions and not need stabiliser hitch." is in my
> experience a gross oversimplification.
>
> Larry
-

[Martin Gregorie[_1_]]

Tom Gardner wrote:
> Martin Gregorie > wrote in news:kg50u4-
> :
>
>> I'd never knock the series II or III. Mine did a London-India out and
>> return in 10 months without any problems apart from a tendency to
>> consume speedometers that I never got to the bottom of, a clutch change
>> in Mysore and a clutch slave cylinder replacement in Turkey.
>
> I had a series II with a 4litre perkins diesel engine.
> Yes, it would pull the skin off custard, and yes the
> engine mountings and transmission spiders were problematical.
>
Mine had the trad. 4 cyl 2.25 litre petrol engine and it would happily
pull skin off custard, but slowly. However, the engine mountings and
transmission were plenty strong enough for that small donk.

The standard diesel was a dog (a diesel version of the four potter,
gutless and noisy). The other standard engine, the 2.6 litre petrol
straight six was also bad news. It was all revs and no torque and very
thirsty with it.

However, when we hit Asia I did rather wish I had the diesel because
that was never more than half the price of petrol from the Bosphorus
east and at that time [1] in Iran it was 1/5 the price of petrol. I had
at least fitted an electronic ignition that moved the beast up from 16
mpg to 18 mpg.

> Mine seemed to have a lot of parts in common with Minis,
> e.g. rear lights and driver's seat.
>
Mine was the 10-12 seat wagon version with up-market seating for five. I
don't recall any Mini parts but it was a long time ago.

[1] 1977/78 when the ******* Shah and his nasty Savak were still there.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Dan G]

On Oct 12, 3:57 pm, "01-- Zero One" > wrote:
> So to say that "Towing is simple. Follow these rules, and your rig will
> be stable in all conditions and not need stabiliser hitch." is in my
> experience a gross oversimplification.

Think we'll have to agree to disagree - but I'd like to know of
examples where these guidelines were met, but the rig was still
unstable.

One thing I don't mention which could be called an
"oversimplification" is weight distribution within the trailer, mass
should be concentrated low and over the axle. However you don't
usually have much choice about that with a glider.


Dan

[Dan G]

On Oct 11, 9:51 pm, Eric Greenwell > wrote:
> Dan G wrote:
> We've discussed this one before, and there is no evidence suggesting 7%
> is appropriate for glider trailers, as the number comes from a study of
> caravans (travel trailers). The more common numbers are 10%-15%, also
> with the requirement to stay within the vehicle and hitch load
> specifications.

I won't disagree, though I'm not sure glider trailers and caravans are
*that* different. I guess the real "rule" is simply having plenty of
weight on the hitch, but not more than the tow vehicle is rated for.

>
> The list does not include the most important factor: speed. Every tow
> vehicle and trailer is stable below some speed; unfortunately, there
> isn't any safe and easy way to determine this that I know of. I do
> suspect most trailer accidents from loss of control could be avoided if
> the driver had paid attention to signs of instability in the past, and
> drove more slowly as a result.

Isn't that common sense, really?


Dan

[Dan G]

On Oct 11, 3:41 pm, Eric Greenwell > wrote:
> Dan G wrote:
>
> > Crash-worthiness and energy absorbtion is ENTIRELY down to design, not
>
> > material.
>
> The major glider manufacturers don't agree with this: take look at the
> cockpit of a Schleicher glider, for example, and see how little of it is
> carbon fiber. Aramids and glass fiber absorb energy better than carbon
> fiber, and so a designer will use them if it is possible.

Didn't I say it's design, not material? :-) However Shleicher do
actually use carbon fibre reinforcements on at least some of their
cockpits - check their website:

http://www.alexander-schleicher.de/produkte/asg29/asg29_main_e.htm

Lange might do too - they say they use "F1 materials" for the cockpit
of the Antares.

The underlying point is that you want the safety cell - whether car,
glider or even train cab - to be extremely strong to resist collapse,
with deformable parts elsewhere to absorb energy and hence lower peak
G on the occupant.


Dan

[Eric Greenwell]

Dan G wrote:
> On Oct 11, 9:51 pm, Eric Greenwell > wrote:
>> Dan G wrote:
>> We've discussed this one before, and there is no evidence suggesting 7%
>> is appropriate for glider trailers, as the number comes from a study of
>> caravans (travel trailers). The more common numbers are 10%-15%, also
>> with the requirement to stay within the vehicle and hitch load
>> specifications.
>
> I won't disagree, though I'm not sure glider trailers and caravans are
> *that* different.

Even glider trailers can differ markedly from one another, so it's no
stretch to imagine caravans (less than half the length, 30% wider, and
twice as tall as a glider trailer of the same weight) might act very
differently behind the same tow vehicle.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

Dan G wrote:
> On Oct 11, 3:41 pm, Eric Greenwell > wrote:
>> Dan G wrote:
>>
>> > Crash-worthiness and energy absorbtion is ENTIRELY down to design, not
>>
>>> material.
>> The major glider manufacturers don't agree with this: take look at the
>> cockpit of a Schleicher glider, for example, and see how little of it is
>> carbon fiber. Aramids and glass fiber absorb energy better than carbon
>> fiber, and so a designer will use them if it is possible.
>
> Didn't I say it's design, not material? :-) However Shleicher do
> actually use carbon fibre reinforcements on at least some of their
> cockpits - check their website:
>
> http://www.alexander-schleicher.de/produkte/asg29/asg29_main_e.htm

All Schleicher gliders, beginning with the ASW 24, use carbon fiber
rails on the cockpit sill, but even on the ASG 29, most of the cockpit
structure is still glass fiber and aramid composite. Gerhard Waibel had
an excellent article describing the design of the ASW 24 cockpit,
considered the first of the modern "safety cockpits", in Soaring
Magazine about 20 years ago, and also more recent articles in Technical
Soaring. Those articles can explain the design of an improved cockpit
much better than I can here.

>
> Lange might do too - they say they use "F1 materials" for the cockpit
> of the Antares.
>
> The underlying point is that you want the safety cell - whether car,
> glider or even train cab - to be extremely strong to resist collapse,
> with deformable parts elsewhere to absorb energy and hence lower peak
> G on the occupant.

To the contrary, Schleicher and the others have chosen not to use a
"safety cell" design. The nose would have to extend several feet beyond
were it does now to have sufficient crush distance, and they do not
believe pilots will buy such a glider.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

> > Lange might do too - they say they use "F1 materials" for the cockpit
> > of the Antares.
>
> > The underlying point is that you want the safety cell - whether car,
> > glider or even train cab - to be extremely strong to resist collapse,
> > with deformable parts elsewhere to absorb energy and hence lower peak
> > G on the occupant.
>
> To the contrary, Schleicher and the others have chosen not to use a
> "safety cell" design. The nose would have to extend several feet beyond
> were it does now to have sufficient crush distance, and they do not
> believe pilots will buy such a glider.

Lange does use a crush zone, and it certainly did not
require "several feet longer fuselage" for Antares. See:
http://www.lange-flugzeugbau.de/htm/english/products/antares_20e/safety.html
The crushable nose-cone is a separate part from the
remainder of the safety cockpit, attached late in the
manufacturing. I'll try get some pictures on my
web site...

See ya, Dave "YO"

[Andor Holtsmark]

Just to clear some things up:
The Antares family of gliders has been designed with
a safety cell and energy absorbing nosecone. In order
to facilitate this, the cockpit was extended forward
at approximately zero aerodynamic loss. The whole cockpit
is using a special carbon-carbon technology (no kevlar
or dyneema), and was designed mainly by a F1 crash
structure designer. The safety cell has been design
to fail only after there is nothing left to save inside
(due to extreme g-loads).

Fitting the lower part of the pilot into the crumble-zone
is, in my personal opinion, not the best of ideas,
as damage to the feet tend to take extremely long to
heal.

Andor



At 02:18 13 October 2007, Eric Greenwell wrote:
>Dan G wrote:
>> On Oct 11, 3:41 pm, Eric Greenwell wrote:
>>> Dan G wrote:
>>>
>>> > Crash-worthiness and energy absorbtion is ENTIRELY
>>>>down to design, not
>>>
>>>> material.
>>> The major glider manufacturers don't agree with this:
>>>take look at the
>>> cockpit of a Schleicher glider, for example, and see
>>>how little of it is
>>> carbon fiber. Aramids and glass fiber absorb energy
>>>better than carbon
>>> fiber, and so a designer will use them if it is possible.
>>
>> Didn't I say it's design, not material? :-) However
>>Shleicher do
>> actually use carbon fibre reinforcements on at least
>>some of their
>> cockpits - check their website:
>>
>> http://www.alexander-schleicher.de/produkte/asg29/asg29_main_e.ht
>>>m
>
>All Schleicher gliders, beginning with the ASW 24,
>use carbon fiber
>rails on the cockpit sill, but even on the ASG 29,
>most of the cockpit
>structure is still glass fiber and aramid composite.
>Gerhard Waibel had
>an excellent article describing the design of the ASW
>24 cockpit,
>considered the first of the modern 'safety cockpits',
>in Soaring
>Magazine about 20 years ago, and also more recent articles
>in Technical
>Soaring. Those articles can explain the design of an
>improved cockpit
>much better than I can here.
>
>>
>> Lange might do too - they say they use 'F1 materials'
>>for the cockpit
>> of the Antares.
>>
>> The underlying point is that you want the safety cell
>>- whether car,
>> glider or even train cab - to be extremely strong
>>to resist collapse,
>> with deformable parts elsewhere to absorb energy and
>>hence lower peak
>> G on the occupant.
>
>To the contrary, Schleicher and the others have chosen
>not to use a
>'safety cell' design. The nose would have to extend
>several feet beyond
>were it does now to have sufficient crush distance,
>and they do not
>believe pilots will buy such a glider.
>
>--
>Eric Greenwell - Washington State, USA
>* Change 'netto' to 'net' to email me directly
>* 'Transponders in Sailplanes' http://tinyurl.com/y739x4
>* 'A Guide to Self-launching Sailplane Operation' at
>www.motorglider.org
>

[Eric Greenwell]

wrote:

>> To the contrary, Schleicher and the others have chosen not to use a
>> "safety cell" design. The nose would have to extend several feet beyond
>> were it does now to have sufficient crush distance, and they do not
>> believe pilots will buy such a glider.
>
> Lange does use a crush zone, and it certainly did not
> require "several feet longer fuselage" for Antares. See:
> http://www.lange-flugzeugbau.de/htm/english/products/antares_20e/safety.html
> The crushable nose-cone is a separate part from the
> remainder of the safety cockpit, attached late in the
> manufacturing.

It looks like a good design; still, an additional 4" over a "normal"
fuselage is not much compared to the several feet of crush zone
available in an automobile. Is it intended that the cockpit function in
the "safety cell" manner that Dan G was describing, or is it designed to
crumple progressively to absorb energy, like the Schleicher cockpits?

I wish there indpendent tests of glider crash protection that were
released to the public, because it is very difficult for us to determine
the effectiveness of a design, especially new designs that have not had
any crashes yet.

I'll try get some pictures on my
> web site...

I'd love to see those.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

Andor Holtsmark wrote:
> Just to clear some things up:
> The Antares family of gliders has been designed with
> a safety cell and energy absorbing nosecone. In order
> to facilitate this, the cockpit was extended forward
> at approximately zero aerodynamic loss. The whole cockpit
> is using a special carbon-carbon technology (no kevlar
> or dyneema), and was designed mainly by a F1 crash
> structure designer.

This is really very interesting. Are there test results that you can
share with us, or perhaps videos of crash tests? Is there an article on
the use of carbon-carbon technology in crash structure design you can
recommend? I'd like to know more about that technology.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Dan G]

On Oct 12, 11:09 pm, Eric Greenwell > wrote:
> Even glider trailers can differ markedly from one another, so it's no
> stretch to imagine caravans (less than half the length, 30% wider, and
> twice as tall as a glider trailer of the same weight) might act very
> differently behind the same tow vehicle.

One of the findings I remember from the Bath University study was that
aerodynamics had little effect on stability - it was all about weight
distribution. Shame the research is "pre-internet" - though maybe it
got published in some engineering journal somewhere.

However it doesn't really matter what shape, size or weight your
trailer is, the basic rules always apply. You could never recommend
having a negative noseweight or towing with a vehicle lighter than the
trailer, for example.


Dan

[Dan G]

On Oct 13, 3:14 am, Eric Greenwell > wrote:
> To the contrary, Schleicher and the others have chosen not to use a
> "safety cell" design.

No, the ASW safety cockpit is a "safety cell" design, but your legs
occupy the crumple zone. The idea was it was better that you broke
your legs than died. Reinforcements - material irrelevant - in the
cockpit walls and canopy frame stops the cell from collapsing into the
space your torso occupies.

> The nose would have to extend several feet beyond
> were it does now to have sufficient crush distance, and they do not
> believe pilots will buy such a glider.

Research has shown that only a modest - less than 50 cm - extension of
the nose is sufficient to absorb enough energy that a safety cell in a
glider can be effective up to at least 25 g:

http://www.ostiv.fai.org/CkptRoeg.pdf

As has been pointed out by others in this thread, Lange have used this
research and so developed the extended collapsing nose-cone of the
Antares.

On Oct 13, 5:32 pm, Eric Greenwell > wrote:
> It looks like a good design; still, an additional 4" over a "normal"
> fuselage is not much compared to the several feet of crush zone
> available in an automobile.

The human body can easily survive 45 g with a good harness:

http://csel.eng.ohio-state.edu/voshell/gforce.pdf

So only a few tens of centimetres are required to reduce the
acceleration in a glider crash to survivable levels.

> Is it intended that the [Antares] cockpit function in
> the "safety cell" manner that Dan G was describing...?

Yes:

http://www.lange-flugzeugbau.com/htm/english/products/antares_20e/safety.html

> I wish there indpendent tests of glider crash protection that were
> released to the public, because it is very difficult for us to determine
> the effectiveness of a design, especially new designs that have not had
> any crashes yet.

There has been lots, see the link I posted above and also the DG
website for some overviews. Tony Head first conducted crash testing in
1988 and did lots more. TUV Rhineland did testing throughout the
1990s.


Dan

[Eric Greenwell]

Dan G wrote:
> On Oct 12, 11:09 pm, Eric Greenwell > wrote:
>> Even glider trailers can differ markedly from one another, so it's no
>> stretch to imagine caravans (less than half the length, 30% wider, and
>> twice as tall as a glider trailer of the same weight) might act very
>> differently behind the same tow vehicle.
>
> One of the findings I remember from the Bath University study was that
> aerodynamics had little effect on stability

That would be my guess for a caravan, as it's area is relatively close
to it's axle. My guess for glider trailers is their relatively greater
length would make it a factor. The "tail fin", since it is mounted far
from the axle (much farther than the end of a small caravan is from it's
axle), seems like it could have a noticeable effect. A number of pilots
have reported putting spoilers on the trailer fin improved the stability.


> - it was all about weight
> distribution.

That is what I was thinking about when I mentioned the big differences
in shape between a caravan and a glider trailer. In addition to weight
distribution, geometry is very important (such as distance from the tow
vehicle's axle to the hitch), as are tires.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

Dan G wrote:
> Research has shown that only a modest - less than 50 cm - extension of
> the nose is sufficient to absorb enough energy that a safety cell in a
> glider can be effective up to at least 25 g:
>
> http://www.ostiv.fai.org/CkptRoeg.pdf

A very interesting report! I'm pleased to see cockpit design has
progressed this much.
>
> As has been pointed out by others in this thread, Lange have used this
> research and so developed the extended collapsing nose-cone of the
> Antares.

I was impressed by the design before; now, even more so.

> On Oct 13, 5:32 pm, Eric Greenwell > wrote:
>> It looks like a good design; still, an additional 4" over a "normal"
>> fuselage is not much compared to the several feet of crush zone
>> available in an automobile.
>
> The human body can easily survive 45 g with a good harness:
>
> http://csel.eng.ohio-state.edu/voshell/gforce.pdf
>
> So only a few tens of centimetres are required to reduce the
> acceleration in a glider crash to survivable levels.

This was surprising to me. Also surprising was the statistic that 76% of
the accidents have impacts less 101 kph. I would have guessed much
higher, and I know much higher impact speeds were part of the "several
feet of crush zone" discussion that took place about 15+ years ago.
>
>> Is it intended that the [Antares] cockpit function in
>> the "safety cell" manner that Dan G was describing...?
>
> Yes:
>
> http://www.lange-flugzeugbau.com/htm/english/products/antares_20e/safety.html
>
>> I wish there indpendent tests of glider crash protection that were
>> released to the public, because it is very difficult for us to determine
>> the effectiveness of a design, especially new designs that have not had
>> any crashes yet.
>
> There has been lots, see the link I posted above and also the DG
> website for some overviews. Tony Head first conducted crash testing in
> 1988 and did lots more. TUV Rhineland did testing throughout the
> 1990s.

And also by a group at MIT:

R. John Hannsman, Edward F. Crawley, and Karl-Peter Kampf, Experimental
investigation of the Crash-Worthiness of Scaled Composite Sailplane
Fuselages, Technical Soaring, volume 14, number 4, 1990, page 111

But, what I was wishing for was standardized testing of production
sailplanes, similar to what is done for automobiles. An expensive wish,
I know, but perhaps soon standardized computer calculations could
replace full scale testing sufficiently well to make safety comparisons.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[HL Falbaum]

OK--I'll supply one.

1999 Chev Tahoe
1999 ASW27 + Cobra
Tongue weight about 9%
all tires new

Begins sway at 68mph--diverging oscillation above 70 mph.
Tried spoilers on vertical fin--no help
Used nails as wedges to stabilize hitch in the receiver--no help.

Attached same setup to a Ford Expedition--stable at up to 110 mph!

Bought 2003 Chev Avalanche
Stable at any speed traffic allowed!

The difference---The 1999 Tahoe had a soft suspension and "vague" steering.
The Avalance and the Expedition are much more stiffly suspended and the
steering more precise. All three vehicles are massive compared to the
Cobra+'27

The answer--IMO the "natural frequency" of the suspension no longer
resonated with the trailer suspension "natural frequency" at highway speed.

--
Hartley Falbaum
"KF" USA


"Dan G" > wrote in message
ps.com...
> On Oct 12, 3:57 pm, "01-- Zero One" > wrote:
>> So to say that "Towing is simple. Follow these rules, and your rig will
>> be stable in all conditions and not need stabiliser hitch." is in my
>> experience a gross oversimplification.
>
> Think we'll have to agree to disagree - but I'd like to know of
> examples where these guidelines were met, but the rig was still
> unstable.
>
> One thing I don't mention which could be called an
> "oversimplification" is weight distribution within the trailer, mass
> should be concentrated low and over the axle. However you don't
> usually have much choice about that with a glider.
>
>
> Dan
>

[Eric Greenwell]

Dan G wrote:
> On Oct 12, 3:57 pm, "01-- Zero One" > wrote:
>> So to say that "Towing is simple. Follow these rules, and your rig will
>> be stable in all conditions and not need stabiliser hitch." is in my
>> experience a gross oversimplification.
>
> Think we'll have to agree to disagree - but I'd like to know of
> examples where these guidelines were met, but the rig was still
> unstable.

My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is
stable at 60 mph. At 70 mph, it's starting to quiver, and I've never
dared go faster. So, is the rig "stable" or "unstable"?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[tommytoyz]

Dan,
Indeed, from reading many posts on the stability issue, it seems that
a precise, stiff suspension is what makes the rig stable. I recall one
poster saying his rig was not very stable till he fixed a somewhat
worn and loose joint in the front suspension that was barely
noticeable when driving normally, but it improved the stability of the
rig enormously.

I suspect that when the tow vehicle itself is heavily loaded, making
it less stable, it can have the same effect and cause the rig to be
less stable than when the tow vehicle is more lightly loaded.

The Honda Accord I used to tow had a Iow cg and a fairly stiff
suspension compared to many large tow vehicles. The Astir CS and heavy
trailer were clearly stable to 80MPH, which is as fast as I ever
went. Never tried faster as I never trusted the small tires on the
trailer too much.

I doubt stability is about the weight of the tow vehicle.

[John Smith]

tommytoyz wrote:

> Indeed, from reading many posts on the stability issue, it seems that
> a precise, stiff suspension is what makes the rig stable.

And this explains partly why Americans tend to think they use trucks to
tow. US cars have had a reputation for poor suspensions. Poor suspension
means poor towing stability. Imagine someone towing with a large V8 with
poor suspension. The tow will be unstable. Now try to tell that guy that
towing with a smaller car will yield more stable results! No way, his
logic will tell him he needs an even bigger car, i.e. a truck.

As my girlfriend always said: It's not the size, it's the stiffness
which matters.

[Dan G]

On Oct 16, 3:35 am, "HL Falbaum" > wrote:
> OK--I'll supply one.
>
> 1999 Chev Tahoe
> 1999 ASW27 + Cobra
> Tongue weight about 9%
> all tires new
>
> Begins sway at 68mph--diverging oscillation above 70 mph.
> Tried spoilers on vertical fin--no help
> Used nails as wedges to stabilize hitch in the receiver--no help.
>
> Attached same setup to a Ford Expedition--stable at up to 110 mph!
>
> Bought 2003 Chev Avalanche
> Stable at any speed traffic allowed!
>
> The difference---The 1999 Tahoe had a soft suspension and "vague" steering.
> The Avalance and the Expedition are much more stiffly suspended and the
> steering more precise. All three vehicles are massive compared to the
> Cobra+'27
>
> The answer--IMO the "natural frequency" of the suspension no longer
> resonated with the trailer suspension "natural frequency" at highway speed.

Of course different tow vehicles will tow differently, particularly
with SUVs, many of which use suspension which can only be described
politely as being "agricultural". My point (which I did not explain
clearly) was that I doubt that if you had, for example, tried a
negative noseweight or stuck a bunch of lead acid batteries in the end
of the trailer your Tahoe would have towed at high-speed with
stability.


Dan

[Dan G]

On Oct 16, 4:46 am, Eric Greenwell > wrote:
> Dan G wrote:
> > On Oct 12, 3:57 pm, "01-- Zero One" > wrote:
> >> So to say that "Towing is simple. Follow these rules, and your rig will
> >> be stable in all conditions and not need stabiliser hitch." is in my
> >> experience a gross oversimplification.
>
> > Think we'll have to agree to disagree - but I'd like to know of
> > examples where these guidelines were met, but the rig was still
> > unstable.
>
> My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is
> stable at 60 mph. At 70 mph, it's starting to quiver, and I've never
> dared go faster. So, is the rig "stable" or "unstable"?

What's the speed limit for a towing vehicle in the US? In the UK it's
60, so your rig would be "stable", though of course it would be
preferable to have a higher safety margin in the event of cross-winds
etc.

Let me try and explain this another way:

*if your trailer is trying to lift the rear of your tow vehicle when
hitched, it will have reduced stability than if it's pressing down.

*If your trailer has a heavy mass at the far end, it will have reduced
stability compared to if it had that mass in low down over the axle.

*If your trailer has underinflated tyres, it will have reduced
stability compared to if it had correctly inflated tyres (and they
might go "bang", too)

*If your trailer weighs more than your towcar, it will have reduced
stability compared to if the towcar was heavier than the trailer.

I hope that's clearer. The Bath University guidelines were also
developed using average Euro cars - I would not expect an tall,
unstable American SUV or pickup with ancient suspension to be
particularly stable in many circumstances, even when not towing. More
recent models with relatively modern suspension should, of course,
fare better.


Dan

[HL Falbaum]

"Dan G" > wrote in message
ups.com...
> On Oct 16, 4:46 am, Eric Greenwell > wrote:
>> Dan G wrote:
>> > On Oct 12, 3:57 pm, "01-- Zero One" > wrote:
>> >> So to say that "Towing is simple. Follow these rules, and your rig
>> >> will
>> >> be stable in all conditions and not need stabiliser hitch." is in my
>> >> experience a gross oversimplification.
>>
>> > Think we'll have to agree to disagree - but I'd like to know of
>> > examples where these guidelines were met, but the rig was still
>> > unstable.
>>
>> My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is
>> stable at 60 mph. At 70 mph, it's starting to quiver, and I've never
>> dared go faster. So, is the rig "stable" or "unstable"?
>
> What's the speed limit for a towing vehicle in the US? In the UK it's
> 60, so your rig would be "stable", though of course it would be
> preferable to have a higher safety margin in the event of cross-winds
> etc.
>
> Let me try and explain this another way:
>
> *if your trailer is trying to lift the rear of your tow vehicle when
> hitched, it will have reduced stability than if it's pressing down.
>
> *If your trailer has a heavy mass at the far end, it will have reduced
> stability compared to if it had that mass in low down over the axle.
>
> *If your trailer has underinflated tyres, it will have reduced
> stability compared to if it had correctly inflated tyres (and they
> might go "bang", too)
>
> *If your trailer weighs more than your towcar, it will have reduced
> stability compared to if the towcar was heavier than the trailer.
>
> I hope that's clearer. The Bath University guidelines were also
> developed using average Euro cars - I would not expect an tall,
> unstable American SUV or pickup with ancient suspension to be
> particularly stable in many circumstances, even when not towing. More
> recent models with relatively modern suspension should, of course,
> fare better.
>
>
> Dan
>

On our USA Interstate Highways, speeds tend to average 75mph. Speed limits
are lower, but not usually enforced until above 80 mph or more. Even the
Semi trailers (18 Wheel trucks) are doing 70-75 or more. If you drive 65,
you are continually passed by these trucks, each producing "bow waves" that
induce more sway. So stability up to 80 mph is highly desirable.

The above noted points all contribute to stability, but I tried them all,
and then some, one at a time, and in combinations. There was no dramatic
improvement until I changed vehicles. The Tahoe and the Avalanche weigh
about the same. The Avalanche has a longer wheelbase. They both have live
rear axles and use the same tires.

IMO the best way to improve a tow vehichle is with "helper springs" to
stiffen the rear, and if needed, the front, suspension. These are easy to
add, relatively inexpensive, and can improve the handling even without the
trailer. Of course, this is after bringing the suspension up to "specs"
first. Shortening the distance between the hitch and the rear axle, where
possible, helps too. Two inches can make a difference.


Hartley Falbaum
"KF" USA

[tommytoyz]

Regarding safety in collisions:

Linked bellow is a report from the institute for Highway safety that
shows that a car colliding with a heavy SUV favors the occupants of
the SUV enormously. These are death statistics.

However, in Solo acciddents, like spin outs and collisions with
immovable objects, the car is far better and the statistics support
this.

Because in cars, 42% of deaths are in solo accidents. In SUVs, 63% of
deaths are in solo accidents. So basically, don't loose control of an
SUV or hit anything. In cars, only 27% of deaths occur when cars are
involved with something bigger than themselves, including buses.

The report concludes that by far, the most deaths occur in solo
crashes in both cars and SUVs. This speaks against SUVs being safer
overall.

Overall, except for slow city driving, I doubt the SUV is safer and I
personally don't feel safer in one cruising on a country road or
freeway, especially towing something.

Report:
http://www.iihs.org/sr/pdfs/sr4005.pdf

[Eric Greenwell]

Dan G wrote:

>> My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is
>> stable at 60 mph. At 70 mph, it's starting to quiver, and I've never
>> dared go faster. So, is the rig "stable" or "unstable"?
>
> What's the speed limit for a towing vehicle in the US?

The highest speeds are on the Interstates. In California, it's 55 mph;
in Montana, it's 75 mph. Other states are between these two.

> In the UK it's
> 60, so your rig would be "stable", though of course it would be
> preferable to have a higher safety margin in the event of cross-winds
> etc.

So, the study investigated relatively short, wide, and tall trailers
towed no faster than 60 mph. It doesn't seem likely to have much to
offer the typical glider pilot!

The point I'm trying to make is most of the glider towing combinations
can go fast enough to become unstable, and following the "rules" doesn't
ensure stability at even legal speeds, much less at the speeds many
pilots want to tow.


>
> Let me try and explain this another way:
>
> *if your trailer is trying to lift the rear of your tow vehicle when
> hitched, it will have reduced stability than if it's pressing down.
>
> *If your trailer has a heavy mass at the far end, it will have reduced
> stability compared to if it had that mass in low down over the axle.
>
> *If your trailer has underinflated tyres, it will have reduced
> stability compared to if it had correctly inflated tyres (and they
> might go "bang", too)
>
> *If your trailer weighs more than your towcar, it will have reduced
> stability compared to if the towcar was heavier than the trailer.

I think we all agreed from the start that the "rules" were sensible;
what some of us have pointed out is they are not sufficient. If pilots
never towed over 60 mph, we'd have far fewer trailer towing discussions!
And a lot fewer accidents, too.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

I tow with a Toyota 4-Runner which is a mid sized SUV. While it would
appear to be a good choice for towing I found 60 to be the limit
before sway would start. I believe the problem is that even though it
has fairly heavy suspension you can still induce sideways movement by
pushing with one finger on the rear of the vehicle. After trying every
solution I could think of I finally changed the trailer connector to
Al-Ko AKS 1300 Stabilizer, which works by pad pressure to the ball.

http://tinyurl.com/yvjhve


Towing is now stable up to the max speed of the vehicle, which with a
6 cylinder engine and trailer in tow is 85. While pricey at $250 for
the connector and special ball coupler it is cheaper than unwrapping
the car/trailer from a tree.

[Eric Greenwell]

wrote:
> After trying every
> solution I could think of I finally changed the trailer connector to
> Al-Ko AKS 1300 Stabilizer, which works by pad pressure to the ball.
>
> http://tinyurl.com/yvjhve
>
>
> Towing is now stable up to the max speed of the vehicle, which with a
> 6 cylinder engine and trailer in tow is 85. While pricey at $250 for
> the connector and special ball coupler it is cheaper than unwrapping
> the car/trailer from a tree.

Still cheaper than changing tires and wheels on the trailer or the
4-Runner, buying a new vehicle, or moving the axle back on trailer! And,
as I recall from your article, quite compact and easy to use compared to
the chains and springs of the load distribution solutions.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

You guys are leaving out a very important part of the equation when it
comes to stability and the ability to prevent sway. That would be
tires and the stiffness of their sidewalls. This makes a huge
difference. This can have as much of an impact as suspension.

Case in point; My brother and I at one time both had Dodge Ram trucks.
I had "E" rated tires, and he had really low rated tires (can't
remember which load designation). One of my trailers is a large 4-
place enclosed snowmobile trailer. We hitched it up to his truck to
head north for some snowmobiling and that rig was all over the place.
Glad the trailer had electric brakes because he had to apply them a
number of times to get the sway under control. Well, it wasn't very
many miles of this adventure before we turned back to switch to my
truck. When we got back from the trip, he replaced all of his tires
with a higher load range (don't remember if he went all the way to
"E") and we took a test drive with the trailer. The difference was
night and day. Problem solved!

Some of you guys with sway issues should see your tire dealer and
inquire about stiffer tires. Granted, the ride is not quite as soft,
but it's a lot safer. Even when you're not towing.


Cheers,
Dave

[Papa3]

On Oct 17, 3:02 pm, wrote:
> You guys are leaving out a very important part of the equation when it
> comes to stability and the ability to prevent sway. That would be
> tires and the stiffness of their sidewalls. This makes a huge
> difference. This can have as much of an impact as suspension.
>
> Case in point; My brother and I at one time both had Dodge Ram trucks.
> I had "E" rated tires, and he had really low rated tires (can't
> remember which load designation). One of my trailers is a large 4-
> place enclosed snowmobile trailer. We hitched it up to his truck to
> head north for some snowmobiling and that rig was all over the place.
> Glad the trailer had electric brakes because he had to apply them a
> number of times to get the sway under control. Well, it wasn't very
> many miles of this adventure before we turned back to switch to my
> truck. When we got back from the trip, he replaced all of his tires
> with a higher load range (don't remember if he went all the way to
> "E") and we took a test drive with the trailer. The difference was
> night and day. Problem solved!
>
> Some of you guys with sway issues should see your tire dealer and
> inquire about stiffer tires. Granted, the ride is not quite as soft,
> but it's a lot safer. Even when you're not towing.
>
> Cheers,
> Dave

Absolutely. Look back to an earlier post on towing. When I switched
to a cheaper, lower speed rated tire to save some money on my tow
vehicle (VW Passat wagon), the tow stability was noticably worse.
Upgrading to better tires (similar to the OEM values) immediately got
me back to where I used to be, which was a stable tow at up to about
70 mph.

P3

[[email protected]]

I agree with Dave. Heavier sidewalls, which are higher load rated not
higher speed rated, will help since they are more resistant to lateral
movement. Problem is that after an expensive tire change you may still
end up with some sway but in addition a car that rides like a gravel
truck.

[[email protected]]

I agree with Dave. Heavier sidewalls, which are higher load rated not
higher speed rated, will help since they are more resistant to lateral
movement. Problem is that after an expensive tire change you may still
end up with some sway but in addition a car that rides like a gravel
truck.

[Dave Doe]

In article om>,
says...
> You guys are leaving out a very important part of the equation when it
> comes to stability and the ability to prevent sway. That would be
> tires and the stiffness of their sidewalls. This makes a huge
> difference. This can have as much of an impact as suspension.
>
> Case in point; My brother and I at one time both had Dodge Ram trucks.
> I had "E" rated tires, and he had really low rated tires (can't
> remember which load designation). One of my trailers is a large 4-
> place enclosed snowmobile trailer. We hitched it up to his truck to
> head north for some snowmobiling and that rig was all over the place.
> Glad the trailer had electric brakes because he had to apply them a
> number of times to get the sway under control. Well, it wasn't very
> many miles of this adventure before we turned back to switch to my
> truck. When we got back from the trip, he replaced all of his tires
> with a higher load range (don't remember if he went all the way to
> "E") and we took a test drive with the trailer. The difference was
> night and day. Problem solved!
>
> Some of you guys with sway issues should see your tire dealer and
> inquire about stiffer tires. Granted, the ride is not quite as soft,
> but it's a lot safer. Even when you're not towing.

Some good points. I run LT tires (light truck) on my tandem trailer.
These have stiffer sidewalls, and are not rated for speeds over about
100km/hr I believe. Having stiffer sidewalls seems to get the tires to
the right temp when towing (warm to the touch), where "standard" tires
would undoubtably be a lot warmer.

--
Duncan