Towing stability studies

[Dan G]

You may remember be talking about research carried out by Bath
University and the Caravan Club of the UK -- well, after 20 years of
research(!), something has finally been published on the web.

http://towingstabilitystudies.co.uk/index.htm

There's not a whole lot there, but that reflects the fact that
stability is pretty simple: have at least 7% of the trailer weight on
the hitch (up to the towcar's limit), and concentrate mass low down
around the axle.

[noel.wade]

Just to throw a little wild hair response in, imagine the convergence
of these technologies:

Sonex e-Flight Initiative: http://aeroconversions.com/e-flight/
(DC Electric Motor for aircraft)
--or, if you prefer AC power--
http://www.teslamotors.com
(AC electric motor, could be adopted for aircraft)

AND

http://news-service.stanford.edu/news/2008/january9/nanowire-010908.html
(New Nano-Wire Battery Technology)

In the near-term, we're probably looking at smaller (80 - 150hp
equivalent) motors running for a few hours at a time. But in 10 - 15
years I think that battery and electric-motor technology will be at a
point where towing would be possible... Here's hoping, at least!

Take care,

--Noel
P.S. My Dad's a Nuclear Engineer at a power-plant (former Navy
Submariner on nuclear-powered subs); but I don't see that process
fitting inside an engine cowling anytime soon! *chuckle* I know I'm
asking for some strange responses by saying this, but I hope folks
will soon realize that the small amount of long-term nuclear waste is
FAR less damaging to the environment than all of the bad side-effects
of fossil/bio-fuels. Europe got it right in switching to more Nuclear
power (and now with photovoltaics and other good stuff), unlike our
good ol' USA... If we ever want to have Hydrogen Fuel Cells, large-
scale electric power for vehicles, or large-scale electrolysis
(desalination of sea-water to produce clean drinking water), Nuclear
Power is the most efficient system; and the only economically-viable
way to do so with current technology...

[Kloudy via AviationKB.com]

noel.wade wrote:
>Just to throw a little wild hair response in, imagine the convergence
>of these technologies:
>
>Sonex e-Flight Initiative: http://aeroconversions.com/e-flight/
>(DC Electric Motor for aircraft)
>--or, if you prefer AC power--
>http://www.teslamotors.com
>(AC electric motor, could be adopted for aircraft)
>
>AND
>
>http://news-service.stanford.edu/news/2008/january9/nanowire-010908.html
>(New Nano-Wire Battery Technology)

I was thinking about how one might hook up a similar motor or generator to
the trailer wheels and charge your flight batteries on the way back from a
retrieve.

or something like that.

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/soaring/200801/1

[Martin Gregorie[_1_]]

Dan G wrote:
> You may remember be talking about research carried out by Bath
> University and the Caravan Club of the UK -- well, after 20 years of
> research(!), something has finally been published on the web.
>
> http://towingstabilitystudies.co.uk/index.htm
>
> There's not a whole lot there, but that reflects the fact that
> stability is pretty simple: have at least 7% of the trailer weight on
> the hitch (up to the towcar's limit), and concentrate mass low down
> around the axle.
>
Its not obvious that studies on caravans are directly applicable to
glider trailers because:

- A caravan has much more frontal area than a glider trailer (at
least 3 times at a guess), so it will produce proportionally
more drag at the same speed. Glider trailers and caravans are near
enough to the same shape for this to be a valid comparison, i.e. both
are flat sided bricks.

- a caravan is at least twice the height, so its center of pressure
when being towed will be much higher than for a glider trailer. In
reality that difference should be even larger because almost the
whole front of a glider trailer is shielded by the tow vehicle, while
almost half of a caravan sticks up above the tow vehicle. This will
tend to move its center of pressure further up. Lets estimate the
caravan's CP as being at twice the height of a trailer.

- the distance between a caravan's axle and tow hitch is a lot less
than for a glider trailer. Again I'd guess 9 m for a 15m glider
trailer and 4m for a 6m trailer, a factor of 2.25.

Both a trailer and a caravan's force setups are such that as you go
faster the aerodynamics will generate a lifting force at the tow hitch.
If we assume the figures I used above, the caravan's aerodynamic
up-force on the hitch will be 3 x 2 x 2.25 = 13.5 times greater than for
a glider trailer. This suggests that a glider trailer should need less
weight on the tow ball than a caravan.

Comparison point: my trailer, which is 15m with a small frontal area
tows very stably at up to 65 mph behind a Focus Estate with no more load
on the hitch than I can easily hold up with one hand.


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

[BB]

>
> Both a trailer and a caravan's force setups are such that as you go
> faster the aerodynamics will generate a lifting force at the tow hitch.


In all the endless posts on trailers, this is a new and intriguing
idea. Perhaps the mysterious reason some car/trailer combinations
snake wildly while others that seem similar are much more solid.

So who will try mounting a F1 style inverted wing on the top front of
the trailer?

John Cochrane

[tommytoyz]

> So who will try mounting a F1 style inverted wing on the top front of
> the trailer?
>
> John Cochrane

My thoughts exactly. Also perhaps ensuring that aerodynamically, side
wind gusts only affect the trailer in a neutral way as to yaw motion.
That is, make it insensitive to turning on its yaw axis on a wind side
load. I guess surface areas of the trailer before and aft of the axle
would have to be similar.

[1LK]

Not so simple actually. There are other variables than hitch weight:

1. A glider trailer with a foil-shaped dog house.
2. Independant suspension with variable geometry as seen on many
smaller tow vehicles. This matters
a great deal if the rear suspension compresses unevenly or
rebounds unpredictably after bottoming.
3. The weight distribution of the tow vehicle itself.
4. The distance from the tow ball to the rear axle of the tow
vehicle AND the trailer.
5. How well side to side motion of the tow vehicle rear axle is
limited.
. 6. Side-wall stiffness of the tires.

I could go on. Even if the trailer weight on the hitch is proper at
rest, it may change radically over bumps, under cornering loads or
during heavy acceleration or braking,especially if there's a lot of
weight at the ends of a long trailer (think spare tire, rigging stuff,
tools, etc.) A trailer which is well behaved with no traffic may do
strange things when passing a line of tractor-trailers. Unequal side-
to-side tire inflation ON ANY AXLE OF THE COMBINATION can provide real
adventure.

Some suggestions:

Don't load the hitch anywhere near the tow vehicle weight limit.
You want to set things up so 7-10% of the trailer weight is on the
hitch and the suspension doesn't bottom when you bounce on it. If the
standard suspension bottoms, add helpers. Add aftermarket sway bars
if the rear suspension allows side to side movement.

Check your tire pressures often, at least every fuel stop. While
you're at it, touch the bearing caps with the BACK of your hand to
check for overheating.

Good tires and shock absorbers are still cheap compared to gliders and
trailers.

A good place to work out the kinks is a big empty parking lot on a
weekend. Accelerate in a straight line, tug the steering wheel
sharply to one side or the other and release it. Start slowly and
increase speed in small increments.

If you can stand the size and poor gas milage, it's hard to go wrong
with a pickup or commercial van with a solid axle and a factory tow
package, BTW

My suggestions/opinions only; your milage may vary.

Ray Warshaw
1LK


> There's not a whole lot there, but that reflects the fact that
> stability is pretty simple: have at least 7% of the trailer weight on
> the hitch (up to the towcar's limit), and concentrate mass low down
> around the axle.

[[email protected]]

>If you can stand the size and poor gas milage, it's hard to go wrong
> with a pickup or commercial van with a solid axle and a factory tow
> package, BTW
>
> My suggestions/opinions only; your milage may vary.
>
> Ray Warshaw
> 1LK

I'm hoping for a solution to trailer sway in the Acura MDX that I am
waiting for delivery next week. The MDX has a Trailer Stability Assist
program included in the Vehicle Stability Assist system. Of course,
TSA doesn't fix whatever is causing the sway in the first place but at
least it should eliminate the effects. I've tried various solutions on
my trailer and the one with the greatest positive effect was inflating
the tires to max rated pressure. I think the fundamental problem on my
trailer is the wimpy torsion bar suspension.
Steve

[nimbusgb]

On 26 Jan, 18:20, wrote:
> >If you can stand the size and poor gas milage, it's hard to go wrong
> > with a pickup or commercial van with a solid axle and a factory tow
> > package, BTW
>
> > My suggestions/opinions only; your milage may vary.
>
> > Ray Warshaw
> > 1LK
>
> I'm hoping for a solution to trailer sway in the Acura MDX that I am
> waiting for delivery next week. The MDX has a Trailer Stability Assist
> program included in the Vehicle Stability Assist system. Of course,
> TSA doesn't fix whatever is causing the sway in the first place but at
> least it should eliminate the effects. I've tried various solutions on
> my trailer and the one with the greatest positive effect was inflating
> the tires to max rated pressure. I think the fundamental problem on my
> trailer is the wimpy torsion bar suspension.
> Steve

If you have an airfoil shaped fin box on the trailer try fitting a
'spoiler strip' to either side of the finbox!

I had a ventus B Turbo in a Komet II trailer that used to quietly
dance behind what was normally a perfect tow vehicle. The sway was
usually kicked off by a passing car or when overtaking a big rig or
bus on the motorway. Taping 2 25 mm aluminium right angles about 1m
long, vertically about 100mm behind the leading edge of the fin box
killed the horizontal lift on the box and transformed the handling.

I often got some very strange looks from other club members about it
but I swear it worked a treat.

[[email protected]]

After all of normal fixes failed to improve handling behind my Toyota
4-Runner a Al-Ko AKS 1300 ball stabilizer solved it totally. Not cheap
and requires a special ball but less cost than fixing a tumbled
trailer/glider.
http://tinyurl.com/3yne64

[chris]

On Jan 27, 7:37 am, nimbusgb > wrote:
> On 26 Jan, 18:20, wrote:
>
>
>
> > >If you can stand the size and poor gas milage, it's hard to go wrong
> > > with a pickup or commercial van with a solid axle and a factory tow
> > > package, BTW
>
> > > My suggestions/opinions only; your milage may vary.
>
> > > Ray Warshaw
> > > 1LK
>
> > I'm hoping for a solution to trailer sway in the Acura MDX that I am
> > waiting for delivery next week. The MDX has a Trailer Stability Assist
> > program included in the Vehicle Stability Assist system. Of course,
> > TSA doesn't fix whatever is causing the sway in the first place but at
> > least it should eliminate the effects. I've tried various solutions on
> > my trailer and the one with the greatest positive effect was inflating
> > the tires to max rated pressure. I think the fundamental problem on my
> > trailer is the wimpy torsion bar suspension.
> > Steve
>
> If you have an airfoil shaped fin box on the trailer try fitting a
> 'spoiler strip' to either side of the finbox!
>
> I had a ventus B Turbo in a Komet II trailer that used to quietly
> dance behind what was normally a perfect tow vehicle. The sway was
> usually kicked off by a passing car or when overtaking a big rig or
> bus on the motorway. Taping 2 25 mm aluminium right angles about 1m
> long, vertically about 100mm behind the leading edge of the fin box
> killed the horizontal lift on the box and transformed the handling.
>
> I often got some very strange looks from other club members about it
> but I swear it worked a treat.

I'll second your comment. I have a Komet trailer with a symmetrical
airfoil tailfin. Gusts from passing large trucks would cause it to
sway. I think the curling air caused just the right angle of attack,
and an ugly harmonic say until out of the wake of the truck. I also
added the right angle aluminum bars just as you described. These
spoilers really added 5-15mph more safe speed to the trailer, very
dramatic change.

As far as mechanical side sway [not the aerodynamic type] changing to
stiff sidewall tires "V-rated" and keeping them inflated solved the
issue for me. Factory tires/ones you get when you buy a car can be
terrible.
Instead of 32psi I keep the front tires inflated to 35psi and the
rears at 40psi. Also helps gas mileage.
Chris

[[email protected]]

On Jan 27, 7:12 am, chris > wrote:
> On Jan 27, 7:37 am, nimbusgb > wrote:
>
>
>
> > On 26 Jan, 18:20, wrote:
>
> > > >If you can stand the size and poor gas milage, it's hard to go wrong
> > > > with a pickup or commercial van with a solid axle and a factory tow
> > > > package, BTW
>
> > > > My suggestions/opinions only; your milage may vary.
>
> > > > Ray Warshaw
> > > > 1LK
>
> > > I'm hoping for a solution to trailer sway in the Acura MDX that I am
> > > waiting for delivery next week. The MDX has a Trailer Stability Assist
> > > program included in the Vehicle Stability Assist system. Of course,
> > > TSA doesn't fix whatever is causing the sway in the first place but at
> > > least it should eliminate the effects. I've tried various solutions on
> > > my trailer and the one with the greatest positive effect was inflating
> > > the tires to max rated pressure. I think the fundamental problem on my
> > > trailer is the wimpy torsion bar suspension.
> > > Steve
>
> > If you have an airfoil shaped fin box on the trailer try fitting a
> > 'spoiler strip' to either side of the finbox!
>
> > I had a ventus B Turbo in a Komet II trailer that used to quietly
> > dance behind what was normally a perfect tow vehicle. The sway was
> > usually kicked off by a passing car or when overtaking a big rig or
> > bus on the motorway. Taping 2 25 mm aluminium right angles about 1m
> > long, vertically about 100mm behind the leading edge of the fin box
> > killed the horizontal lift on the box and transformed the handling.
>
> > I often got some very strange looks from other club members about it
> > but I swear it worked a treat.
>
> I'll second your comment. I have a Komet trailer with a symmetrical
> airfoil tailfin. Gusts from passing large trucks would cause it to
> sway. I think the curling air caused just the right angle of attack,
> and an ugly harmonic say until out of the wake of the truck. I also
> added the right angle aluminum bars just as you described. These
> spoilers really added 5-15mph more safe speed to the trailer, very
> dramatic change.
>
> As far as mechanical side sway [not the aerodynamic type] changing to
> stiff sidewall tires "V-rated" and keeping them inflated solved the
> issue for me. Factory tires/ones you get when you buy a car can be
> terrible.
> Instead of 32psi I keep the front tires inflated to 35psi and the
> rears at 40psi. Also helps gas mileage.
> Chris

I've heard about the spoiler fix but never tried it. I was told to put
the spoilers at the trailing edge of the fin. I also talked to a Komet
factory rep at an SSA Convention a few years back and he told me the
cause of sway was absolutely not aerodynamic!
Steve

[nimbusgb]

Have you noticed how the boxes on new trailers are now square :)

[John Galloway[_1_]]

At 17:48 27 January 2008, Nimbusgb wrote:
>Have you noticed how the boxes on new trailers are
>now square :)

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

[Bruce]

Indeed Ian

However, I think a lot of swaying trailer diseases is caused by vortex shedding.
Which is why architects tend not to make too symmetrical buildings.

This is usually triggered by a disturbance to the streamline flow - such as
passing a large vehicle.

Having a turbulator about 30% forward of the back of the trailer works very well
on mine. Don't know who fitted it - but there is a little (about 8mm high)
aluminium profile just ahead of the opening section. Probably fitted to deflect
water past the gap. Mine is a 1971 Anschou trailer with the little wing shaped
doghouse for the fin, but it tows very well.

nimbusgb wrote:
> Have you noticed how the boxes on new trailers are now square :)

[John Galloway[_1_]]

At 17:48 27 January 2008, Nimbusgb wrote:
>Have you noticed how the boxes on new trailers are
>now square :)

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

[1LK]

I did almost the same with my LAK trailer but used pop rivits and
sealer when I was towing with a Chevy Blazer. Without them, the rig
was dicy over 60 mph; after they were added it was rock-steady at
Arizona highway speeds (75 mph). The P/U I replaced the Blazer with
probably wouldn't have needed them, though.

Ray Warshaw
1LK

>
> I had a ventus B Turbo in a Komet II trailer that used to quietly
> dance behind what was normally a perfect tow vehicle. The sway was
> usually kicked off by a passing car or when overtaking a big rig or
> bus on the motorway. Taping 2 25 mm aluminium right angles about 1m
> long, vertically about 100mm behind the leading edge of the fin box
> killed the horizontal lift on the box and transformed the handling.
>
> I often got some very strange looks from other club members about it
> but I swear it worked a treat.

[Jeremy Zawodny]

nimbusgb wrote:
>
> If you have an airfoil shaped fin box on the trailer try fitting a
> 'spoiler strip' to either side of the finbox!
>
> I had a ventus B Turbo in a Komet II trailer that used to quietly
> dance behind what was normally a perfect tow vehicle. The sway was
> usually kicked off by a passing car or when overtaking a big rig or
> bus on the motorway. Taping 2 25 mm aluminium right angles about 1m
> long, vertically about 100mm behind the leading edge of the fin box
> killed the horizontal lift on the box and transformed the handling.
>
> I often got some very strange looks from other club members about it
> but I swear it worked a treat.

Do you have any photos of this installation? I'm wondering if it'll
help settle down my Komet.

Jeremy

[Martin Gregorie[_1_]]

Jeremy Zawodny wrote:
>
> Do you have any photos of this installation? I'm wondering if it'll
> help settle down my Komet.
>
Try it!

Use some scrap 25mm (1") square scrap wood, steel tubing, etc. Anything
that presents a 25mm flat surface at right angles to the fin box skin
will do. Put it on temporarily with Gaffer, Duct or even parcel tape. Do
a short tow. Try moving the strips to sere what works best.

If/when it works well enough, spend the time and money to get 25 mm
alloy angle strip and attach it properly.


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

[nimbusgb]

On 27 Jan, 19:20, John Galloway > wrote:
> At 17:48 27 January 2008, Nimbusgb wrote:
>
> >Have you noticed how the boxes on new trailers are
> >now square :)
>
> If we're talking Cobra, isn't it just metal top - square,
> grp top - curvy?

The latest square finbox I saw was on a GRP top.

[nimbusgb]

..
>
> Do you have any photos of this installation? I'm wondering if it'll
> help settle down my Komet.
>
> Jeremy

All my photos are of the gliders not the trailer ! :)

I taped a couple of pieces piece of angle, parallel to the leading
edge of the finbox, 4 inches or so behind the L/E and about 75% of the
height of the fin box.
I pop-riveted them on once I was convinced it all worked.

I'll sketch something if you want and mail it

[scooter]

On Jan 31, 12:15*am, nimbusgb > wrote:
> On 27 Jan, 19:20, John Galloway > wrote:
>
> > At 17:48 27 January 2008, Nimbusgb wrote:
>
> > >Have you noticed how the boxes on new trailers are
> > >now square :)
>
> > If we're talking Cobra, isn't it just metal top - square,
> > grp top - curvy?
>
> The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. I am currently towing with a short wheelbase Volvo
SUV. This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. I have never had to play with
weights etc. The wheel placement is different than the Cobras which
seem to be more centered.

Picture at http://www.illunis.com/Files/trailer.jpg

Scott

[scooter]

On Jan 31, 3:45*pm, scooter > wrote:
> On Jan 31, 12:15*am, nimbusgb > wrote:
>
> > On 27 Jan, 19:20, John Galloway > wrote:
>
> > > At 17:48 27 January 2008, Nimbusgb wrote:
>
> > > >Have you noticed how the boxes on new trailers are
> > > >now square :)
>
> > > If we're talking Cobra, isn't it just metal top - square,
> > > grp top - curvy?
>
> > The latest square finbox I saw was on a GRP top.
>
> I have a trailer that happily tows at 80mph and has behind a number of
> tow vehicles. *I am currently towing with a short wheelbase Volvo
> SUV. *This trailer is uniquely low, but seems to self damp when a semi
> passes or the wind gusts and has an aerodynamic fin. *I have always
> suspected it has something to do with the fin to trailer wheel moment
> vs trailer wheel to hitch moment. *I have never had to play with
> weights etc. *The wheel placement is different than the Cobras which
> seem to be more centered.
>
> Picture athttp://www.illunis.com/Files/trailer.jpg
>
> Scott

Link should be Picture at http://www.illunis.com/Files/Trailer.jpg

Sorry

Scott

[Eric Greenwell]

scooter wrote:

>> I have a trailer that happily tows at 80mph and has behind a number of
>> tow vehicles. I am currently towing with a short wheelbase Volvo
>> SUV. This trailer is uniquely low, but seems to self damp when a semi
>> passes or the wind gusts and has an aerodynamic fin. I have always
>> suspected it has something to do with the fin to trailer wheel moment
>> vs trailer wheel to hitch moment. I have never had to play with
>> weights etc. The wheel placement is different than the Cobras which
>> seem to be more centered.
>>
>> Picture athttp://www.illunis.com/Files/trailer.jpg
>>
>> Scott
>
> Link should be Picture at http://www.illunis.com/Files/Trailer.jpg

How much does the trailer and glider weigh? I suspect it's quite light,
as the forward wheel placement generally works against stability. I'm
reminded of a couple trailers Roger Frank built years ago.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

On Jan 31, 1:45*pm, scooter > wrote:
> On Jan 31, 12:15*am, nimbusgb > wrote:
>
> > On 27 Jan, 19:20, John Galloway > wrote:
>
> > > At 17:48 27 January 2008, Nimbusgb wrote:
>
> > > >Have you noticed how the boxes on new trailers are
> > > >now square :)
>
> > > If we're talking Cobra, isn't it just metal top - square,
> > > grp top - curvy?
>
> > The latest square finbox I saw was on a GRP top.
>
> I have a trailer that happily tows at 80mph and has behind a number of
> tow vehicles. *I am currently towing with a short wheelbase Volvo
> SUV. *This trailer is uniquely low, but seems to self damp when a semi
> passes or the wind gusts and has an aerodynamic fin. *I have always
> suspected it has something to do with the fin to trailer wheel moment
> vs trailer wheel to hitch moment. *I have never had to play with
> weights etc. *The wheel placement is different than the Cobras which
> seem to be more centered.
>
> Picture athttp://www.illunis.com/Files/trailer.jpg
>
> Scott

My expeience is the right tow vehicle makes more of a difference than
anything I've ever been able to do with loading I've not played with
aerodynamic fixes - but my instincts are that most of these have minor
effects except in special circumstances.

In my estimation the thing that causes stability problems is the
influence the trailer exerts on the yawing motion of the tow vehicle
itself. It does this by exerting lateral force at the tow ball. That
lateral force gets translated into yawing moment based on the weight
of the tow vehicle and the distance between the tow ball and the
natural "pivot point", which is the rear wheels. I would think better
tow vehicles combine adequate weight with a short distance between the
ball and the rear wheels, plus good tire contact area to resist side
loads. I also suspect having adequate weight distribution on the front
wheels helps (that is, loading up the trunk probably doesn't help).

I've been towing for 4 years now with a VW Touareg and find it is rock
steady at any speed under any wind or passing traffic condition. The
vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
the ball and the center of the rear wheels. In a sort of ad hoc
stability test on a very straight and smooth 100 mile stretch of
Nevada highway I've towed at speeds up to 100 mph with no swaying.
Needless to say I didn't stay there long out of concern over trailer
tire ratings and a desire to stay out of jail.

9B

[[email protected]]

On Feb 21, 10:29*am, wrote:
> On Jan 31, 1:45*pm, scooter > wrote:
>
>
>
>
>
> > On Jan 31, 12:15*am, nimbusgb > wrote:
>
> > > On 27 Jan, 19:20, John Galloway > wrote:
>
> > > > At 17:48 27 January 2008, Nimbusgb wrote:
>
> > > > >Have you noticed how the boxes on new trailers are
> > > > >now square :)
>
> > > > If we're talking Cobra, isn't it just metal top - square,
> > > > grp top - curvy?
>
> > > The latest square finbox I saw was on a GRP top.
>
> > I have a trailer that happily tows at 80mph and has behind a number of
> > tow vehicles. *I am currently towing with a short wheelbase Volvo
> > SUV. *This trailer is uniquely low, but seems to self damp when a semi
> > passes or the wind gusts and has an aerodynamic fin. *I have always
> > suspected it has something to do with the fin to trailer wheel moment
> > vs trailer wheel to hitch moment. *I have never had to play with
> > weights etc. *The wheel placement is different than the Cobras which
> > seem to be more centered.
>
> > Picture athttp://www.illunis.com/Files/trailer.jpg
>
> > Scott
>
> My expeience is the right tow vehicle makes more of a difference than
> anything I've ever been able to do with loading I've not played with
> aerodynamic fixes - but my instincts are that most of these have minor
> effects except in special circumstances.
>
> In my estimation the thing that causes stability problems is the
> influence the trailer exerts on the yawing motion of the tow vehicle
> itself. It does this by exerting lateral force at the tow ball. That
> lateral force gets translated into yawing moment based on the weight
> of the tow vehicle and the distance between the tow ball and the
> natural "pivot point", which is the rear wheels. I would think better
> tow vehicles combine adequate weight with a short distance between the
> ball and the rear wheels, plus good tire contact area to resist side
> loads. I also suspect having adequate weight distribution on the front
> wheels helps (that is, loading up the trunk probably doesn't help).
>
> I've been towing for 4 years now with a VW Touareg and find it is rock
> steady at any speed under any wind or passing traffic condition. The
> vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
> the ball and the center of the rear wheels. In a sort of ad hoc
> stability test on a very straight and smooth 100 mile stretch of
> Nevada highway I've towed at speeds up to 100 mph with no swaying.
> Needless to say I didn't stay there long out of concern over trailer
> tire ratings and a desire to stay out of jail.
>
> 9B- Hide quoted text -
>
> - Show quoted text -

Replacing the tires on the tow vehicle with stiffer sidewalls does an
amazing job of stabilizing the rig. The trade-off is a bit harsher
ride, but much, much safer.

[Udo]

On Feb 21, 11:29*am, wrote:
> On Jan 31, 1:45*pm, scooter > wrote:
>
>
>
>
>
> > On Jan 31, 12:15*am, nimbusgb > wrote:
>
> > > On 27 Jan, 19:20, John Galloway > wrote:
>
> > > > At 17:48 27 January 2008, Nimbusgb wrote:
>
> > > > >Have you noticed how the boxes on new trailers are
> > > > >now square :)
>
> > > > If we're talking Cobra, isn't it just metal top - square,
> > > > grp top - curvy?
>
> > > The latest square finbox I saw was on a GRP top.
>
> > I have a trailer that happily tows at 80mph and has behind a number of
> > tow vehicles. *I am currently towing with a short wheelbase Volvo
> > SUV. *This trailer is uniquely low, but seems to self damp when a semi
> > passes or the wind gusts and has an aerodynamic fin. *I have always
> > suspected it has something to do with the fin to trailer wheel moment
> > vs trailer wheel to hitch moment. *I have never had to play with
> > weights etc. *The wheel placement is different than the Cobras which
> > seem to be more centered.
>
> > Picture athttp://www.illunis.com/Files/trailer.jpg
>
> > Scott
>
> My expeience is the right tow vehicle makes more of a difference than
> anything I've ever been able to do with loading I've not played with
> aerodynamic fixes - but my instincts are that most of these have minor
> effects except in special circumstances.
>
> In my estimation the thing that causes stability problems is the
> influence the trailer exerts on the yawing motion of the tow vehicle
> itself. It does this by exerting lateral force at the tow ball. That
> lateral force gets translated into yawing moment based on the weight
> of the tow vehicle and the distance between the tow ball and the
> natural "pivot point", which is the rear wheels. I would think better
> tow vehicles combine adequate weight with a short distance between the
> ball and the rear wheels, plus good tire contact area to resist side
> loads. I also suspect having adequate weight distribution on the front
> wheels helps (that is, loading up the trunk probably doesn't help).
>
> I've been towing for 4 years now with a VW Touareg and find it is rock
> steady at any speed under any wind or passing traffic condition. The
> vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
> the ball and the center of the rear wheels. In a sort of ad hoc
> stability test on a very straight and smooth 100 mile stretch of
> Nevada highway I've towed at speeds up to 100 mph with no swaying.
> Needless to say I didn't stay there long out of concern over trailer
> tire ratings and a desire to stay out of jail.
>
> 9B- Hide quoted text -
>
> - Show quoted text -

I agree,
I have been towing for the last 12 years and averaging 12000km a year.
During that time I have towed with two different Mini Vans.

If the trailers are set up right, as in weight distribution and tires,
the limitation is the indeed the vehicle when it comes max save speed.
In the first case an Aero Star, with the extended box.
The comfort limit was/is 115 km/h no wind, no truck passing.
This would drop to 100km/h with cross wind and trucks passing.
In the second case, a Honda Mini Van low C of G, short coupled to the
tow ball, plenty of power, relative good in fuel consumption, same
conditions 130km plus (tested to over 160km) out west) No drop in
speed needed below 120 in any condition, but snow ice and wet
conditions. My normal speed in the US is 125km/h on smooth 4 lane high
way when traffic and weather conditions allow. Trucks passing is a
none issue as no trucks pass.
I would think that most, if not all modern Mini Van's of that class
make good tow vehicle. In case of smaller cars like a VW Jetta
and similar cars, they do a fine job as well, just dive slower and get
an anti sway set up. My friend has a set up like that and he trailers
his glider happily anywhere with half the gas consumption, (its a
diesel)
I could Iove that too.
Udo

[Bill Daniels]

> wrote in message
...
On Jan 31, 1:45 pm, scooter > wrote:
> On Jan 31, 12:15 am, nimbusgb > wrote:
>
> > On 27 Jan, 19:20, John Galloway > wrote:
>
> > > At 17:48 27 January 2008, Nimbusgb wrote:
>
> > > >Have you noticed how the boxes on new trailers are
> > > >now square :)
>
> > > If we're talking Cobra, isn't it just metal top - square,
> > > grp top - curvy?
>
> > The latest square finbox I saw was on a GRP top.
>
> I have a trailer that happily tows at 80mph and has behind a number of
> tow vehicles. I am currently towing with a short wheelbase Volvo
> SUV. This trailer is uniquely low, but seems to self damp when a semi
> passes or the wind gusts and has an aerodynamic fin. I have always
> suspected it has something to do with the fin to trailer wheel moment
> vs trailer wheel to hitch moment. I have never had to play with
> weights etc. The wheel placement is different than the Cobras which
> seem to be more centered.
>
> Picture athttp://www.illunis.com/Files/trailer.jpg
>
> Scott

My expeience is the right tow vehicle makes more of a difference than
anything I've ever been able to do with loading I've not played with
aerodynamic fixes - but my instincts are that most of these have minor
effects except in special circumstances.

In my estimation the thing that causes stability problems is the
influence the trailer exerts on the yawing motion of the tow vehicle
itself. It does this by exerting lateral force at the tow ball. That
lateral force gets translated into yawing moment based on the weight
of the tow vehicle and the distance between the tow ball and the
natural "pivot point", which is the rear wheels. I would think better
tow vehicles combine adequate weight with a short distance between the
ball and the rear wheels, plus good tire contact area to resist side
loads. I also suspect having adequate weight distribution on the front
wheels helps (that is, loading up the trunk probably doesn't help).

I've been towing for 4 years now with a VW Touareg and find it is rock
steady at any speed under any wind or passing traffic condition. The
vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
the ball and the center of the rear wheels. In a sort of ad hoc
stability test on a very straight and smooth 100 mile stretch of
Nevada highway I've towed at speeds up to 100 mph with no swaying.
Needless to say I didn't stay there long out of concern over trailer
tire ratings and a desire to stay out of jail.

9B

Tow vehicle, definitely.

Most US made SUV's have a resonance about the vertical axis that roughly
matches the trailers sway frequency. You can demonstrate this by pushing
rythmicaly with one finger on a rear quarter panel. When you find the
resonant frequency, the vehicle will wiggle 2 - 3 inches side to side. This
is not roll , it's pure undamped yaw. If this resonance exactly matches the
trailer, you're in for an 'interesting' ride. Most of this is tire sidewall
motion.

I've actually been chased out of dealer showrooms for demonstrating this.

Most SUV's with off road pretensions have tires with high sidewalls in order
to get more ground clearance. You can replace the wheels and use low
sidewall tires but then your vehicle looks like an East LA "low rider" and
you'd have to buy the big fuzzy dice to hang from the mirror and the chrome
welded chain steering wheel so the cuffs and collars matched ;)

Bill D