Komet trailer tires

[Robin]

I want to replace the tires on my Komet trailer. The original tire
size is P165/80 R13, which is now hard to find.

The choice seems to be either a Firestone passenger car radial in the
correct size or a slightly taller Towmaster made by Greenball. The
trailer tire will have a taller but stiffer sidewall. It will come a
little closer to the fender, but my mechanic says less than half an
inch closer. The size is 175/80 R13.

I plan to tow about 75 mph most of the time. I really want to avoid
sway.

Any experience with these tires out there?

Thanks,
Robin RF

[T8]

On Feb 22, 5:12*pm, Robin > wrote:
> I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.
>
> The choice seems to be either a Firestone passenger car radial in the
> correct size or a slightly taller Towmaster made by Greenball. *The
> trailer tire will have a taller but stiffer sidewall. It will come a
> little closer to the fender, but my mechanic says less than half an
> inch closer. The size is 175/80 R13.
>
> *I plan to tow about 75 mph most of the time. I really want to avoid
> sway.
>
> Any experience with these tires out there?
>
> Thanks,
> Robin RF

I use 185/70R 13 tires on my Komet. They are the same diameter as
your 165/80R 13 (within 1/4") but 2cm wider.

-T8

[JS]

Truck or trailer tires will be more stable than car tires. If you're
concerned with clearance, then first try sticking 1" blocks of
styrofoam inside the fenders. Drive around with your existing tires
and see if they rub on or damage the blocks.
The trailer tires are only one part of the equation. Keep the proper
weight and balance on the trailer. Maintain the tow vehicle's shock
absorbers, tires and wheel alignment.
Jim

[Mitch Deutsch]

RF

A number of us have switched to Maxxis, which makes a radial trailer tire.
(www.maxxis.com ST8008). All of MGSA's trailers and a number of private
owners have these tires, with no sway issues reported.

Here in Atlanta they are easy to get from their regional warehouse. I
suspect in JAX, they should be readily available.

I switched from a 165/80 14 to 175/80 14 which gave a slightly taller tire
and better ground clearance. I have Maxxis for about six years, and just
replaced my first set last month with a new set, obeying the John Murray
"five year" rule.



"Robin" > wrote in message
...
>I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.
>
> The choice seems to be either a Firestone passenger car radial in the
> correct size or a slightly taller Towmaster made by Greenball. The
> trailer tire will have a taller but stiffer sidewall. It will come a
> little closer to the fender, but my mechanic says less than half an
> inch closer. The size is 175/80 R13.
>
> I plan to tow about 75 mph most of the time. I really want to avoid
> sway.
>
> Any experience with these tires out there?
>
> Thanks,
> Robin RF

[[email protected][_2_]]

On Feb 22, 5:12*pm, Robin > wrote:
> I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.
>
> The choice seems to be either a Firestone passenger car radial in the
> correct size or a slightly taller Towmaster made by Greenball. *The
> trailer tire will have a taller but stiffer sidewall. It will come a
> little closer to the fender, but my mechanic says less than half an
> inch closer. The size is 175/80 R13.
>
> *I plan to tow about 75 mph most of the time. I really want to avoid
> sway.
>
> Any experience with these tires out there?
>
> Thanks,
> Robin RF

Robin,
Bought tires from a trailer repair place on W. Beaver.
Normandy to Chaffee, Chaffee across I10, across rr tracks, turn
right, just down the road on the right.
They mounted them for me. I had the trailer on blocks in Shawns
hangar.
I was advised to stay away from radials because they create sway.

r/Jim
LS-1f/N20GA/1J

[HL Falbaum[_2_]]

Robin---
I'll second Mitch's vote!
I'm happy with the Maxxis.
Sway is more a function of the tow vehicle than anything else. Demonstrated
by towing same trailer, same road, same day, same speed--two different
vehicles, vastly different result. (as closely controlled experiment as we
could). Replaced poor performing vehicle with different vehicle--marked
improvement.
--
Hartley Falbaum
"KF" USA

"Mitch Deutsch" > wrote in message
m...
> RF
>
> A number of us have switched to Maxxis, which makes a radial trailer tire.
> (www.maxxis.com ST8008). All of MGSA's trailers and a number of private
> owners have these tires, with no sway issues reported.
>
> Here in Atlanta they are easy to get from their regional warehouse. I
> suspect in JAX, they should be readily available.
>
> I switched from a 165/80 14 to 175/80 14 which gave a slightly taller tire
> and better ground clearance. I have Maxxis for about six years, and just
> replaced my first set last month with a new set, obeying the John Murray
> "five year" rule.
>
>
>
> "Robin" > wrote in message
> ...
>>I want to replace the tires on my Komet trailer. The original tire
>> size is P165/80 R13, which is now hard to find.
>>
>> The choice seems to be either a Firestone passenger car radial in the
>> correct size or a slightly taller Towmaster made by Greenball. The
>> trailer tire will have a taller but stiffer sidewall. It will come a
>> little closer to the fender, but my mechanic says less than half an
>> inch closer. The size is 175/80 R13.
>>
>> I plan to tow about 75 mph most of the time. I really want to avoid
>> sway.
>>
>> Any experience with these tires out there?
>>
>> Thanks,
>> Robin RF
>
>

[Eric Greenwell]

Robin wrote:
> I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.
>
> The choice seems to be either a Firestone passenger car radial in the
> correct size or a slightly taller Towmaster made by Greenball. The
> trailer tire will have a taller but stiffer sidewall. It will come a
> little closer to the fender, but my mechanic says less than half an
> inch closer. The size is 175/80 R13.
>
> I plan to tow about 75 mph most of the time. I really want to avoid
> sway.
Don't use trailer tires (ST type) if you tow that fast. From an article
I wrote for the ASH 26 E "tech site":

> Commonly available tire types are P (passenger car), LT (light truck)
> and ST (special trailer). While each tire series shares basic
> construction methods, the details vary meaningfully among the three.
>
> There are other differences:
>
> 1. P tires use a load rating system that is different from ST and
> LT tires; generally, you have to discount their rating 10% to
> get the equivalent ST or LT rating.
> 2. ST tires speed rating is 65 mph. The speed rating increases to
> 75 mph IF you increase the tire pressure to 10 psi above the
> pressure required for your load at 65 mph. These are not the
> tires for folks that like to drive 80 mph across the Nevada
> highways in 100 deg F temperatures.
> 3. ST tires come in both bias-belted and radial construction. The
> only advantage to a bias-belted trailer tire is it's cheaper.
> 4. LT tires are a bit "stiffer" than either P or ST tires, and are
> available in speed ratings to at least 118 mph.
>
P tires might work fine, but I don't know what speed and load ratings
would ensure this. If I decided to use P tires, I'd use them at the
pressure that gave a load rating of ~40% more load rating than the load
they has to carry. I'd choose a speed rating at least 20 mph higher than
the speed rating on my tow vehicles tires. Rules of thumb - no real
documented tests.

Currently, I'm using Michelin LT tires on my Cobra, 105 mph rating.

If avoiding sway is really important to you, you should drive slower.
It's very effective.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

[Eric Greenwell]

Robin wrote:
> I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.
>
> The choice seems to be either a Firestone passenger car radial in the
> correct size or a slightly taller Towmaster made by Greenball. The
> trailer tire will have a taller but stiffer sidewall. It will come a
> little closer to the fender, but my mechanic says less than half an
> inch closer. The size is 175/80 R13.
>
> I plan to tow about 75 mph most of the time. I really want to avoid
> sway.
Don't use trailer tires (ST type) if you tow that fast. From an article
I wrote for the ASH 26 E "tech site":

> Commonly available tire types are P (passenger car), LT (light truck)
> and ST (special trailer). While each tire series shares basic
> construction methods, the details vary meaningfully among the three.
>
> There are other differences:
>
> 1. P tires use a load rating system that is different from ST and
> LT tires; generally, you have to discount their rating 10% to
> get the equivalent ST or LT rating.
> 2. ST tires speed rating is 65 mph. The speed rating increases to
> 75 mph IF you increase the tire pressure to 10 psi above the
> pressure required for your load at 65 mph. These are not the
> tires for folks that like to drive 80 mph across the Nevada
> highways in 100 deg F temperatures.
> 3. ST tires come in both bias-belted and radial construction. The
> only advantage to a bias-belted trailer tire is it's cheaper.
> 4. LT tires are a bit "stiffer" than either P or ST tires, and are
> available in speed ratings to at least 118 mph.
>
P tires might work fine, but I don't know what speed and load ratings
would ensure this. If I decided to use P tires, I'd use them at the
pressure that gave a load rating of ~40% more load rating than the load
they has to carry. I'd choose a speed rating at least 20 mph higher than
the speed rating on my tow vehicles tires. Rules of thumb - no real
documented tests.

Currently, I'm using Michelin LT tires on my Cobra, 105 mph rating.

If avoiding sway is really important to you, you should drive slower.
It's very effective.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

[Eric Greenwell]

wrote:
> Robin,
> Bought tires from a trailer repair place on W. Beaver.
> Normandy to Chaffee, Chaffee across I10, across rr tracks, turn
> right, just down the road on the right.
> They mounted them for me. I had the trailer on blocks in Shawns
> hangar.
> I was advised to stay away from radials because they create sway.

Bad advice. ST tires come in both bias-belted and radial construction.
The only advantage to a bias-belted trailer tire is it's cheaper. Cobra
trailers have come with radials for decades; also, wander through a new
travel trailer lot, and notice how they all have radials. Also, last
time I looked, there was very little choice in non-radial sizes. Some
major companies don't even sell them.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

[Morgans[_2_]]

"Robin" > wrote

>I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.

> I plan to tow about 75 mph most of the time. I really want to avoid
> sway.

Yes, add another axle behind the one there, then use any tire you want, and
it will never sway again.
--
Jim in NC

[Morgans[_2_]]

"HL Falbaum" > wrote

> Sway is more a function of the tow vehicle than anything else.
> Demonstrated by towing same trailer, same road, same day, same speed--two
> different vehicles, vastly different result.

If you don't believe that, try towing ANY trailer with an uber short
wheelbase, low overhang vehicle, like a Jeep. A Jeep CJ vehicle will make
ANY trailer sway, with any trailer weight and balance.
--
Jim in NC

[Bruce]

Morgans wrote:
> "Robin" > wrote
>
>> I want to replace the tires on my Komet trailer. The original tire
>> size is P165/80 R13, which is now hard to find.
>
>> I plan to tow about 75 mph most of the time. I really want to avoid
>> sway.
>
> Yes, add another axle behind the one there, then use any tire you want, and
> it will never sway again.
Not true.

Double axle trailers do sway, and are in general more unwieldy than
single axle trailers. A poorly designed trailer will sway at lower
speed, adding an axle seems to increase the speed at which it goes wrong
at the expense of making the transition from stable to out of control
much sharper.

If you want demonstration try towing just about any poorly designed twin
axle trailer fast enough that you get vortex shedding. A light crosswind
is "ideal" for making this exciting.

Use a tyre rated for the job at hand. Stiffer sidewalls help. Lower
profiles help at the expense of being rougher on the glider. Correct
inflation helps.

Learn what a tyre is designed for by reading the sidewall - to
understand the sidewall code look at -

http://www.etyres.co.uk/consumer-information/tyres-sidewall-code.htm

Radials are generally better than crossplies which are generally limited
to "cheap and nasty" applications around here. If you want a durable
trailer tyre for your tractor trailer they make a good choice. At speed
on the highway I would be/am much happier with a tyre rated for the
speed, and with similar compound to the towing vehicle. That means you
should look at the traction grade indication too. It would be
embarassing to have your trailer break traction on a fast sweeping turn
that is not even making your tow vehicles tyre work...

For what it is worth - I have two trailers.

15m std class - streamlined enclosed trailer.
Single axle running on LT. (couple of extra plies in the sidewall)
LT175/70R13S
So a less compliant casing radial, with speed rating of 116. Tows stable
at 120km/h and is reasonably good at not transmitting shocks to the
trailer.

The 19m Kestrel is in a poorly streamlined twin axle trailer.
Both axles have P175/70R13R tyres.
This is unstable at any speed above 100km/h, pushes the tow vehicle
around and is generally unpleasant. Too much compliance in the sidewalls
lets the tyre develop big slip angles which then try to steer the tow
car. In tight turns one of the axles has to scrub, grabbing and releasing.
This winter's project is to convert it to a decent single axle...

Of course the bottom line is to drive a little slower - as well as
having the right tyres on the trailer.

--- news://freenews.netfront.net/ - complaints: ---

[Burt Compton - Marfa]

> Of course the bottom line is to drive a little slower - as well as
> having the right tyres on the trailer.
>

I just checked with my friend in Germany and confirmed that 80 km/hour
is their max legal glider trailer towing speed.
If we had the same law, that would be a max speed of only 50 MPH in
the USA.

So as much as the Germans like to drive fast in their cars, they
apparently tow their glider trailers at a reasonable speed.

My strategy is to maintain good tires, a tight hitch, start driving
early and try not to stop (like not stopping to thermal on a cross
country.)
60 MPH gets you there. Save gas / save your glider.

Burt
Marfa, west Texas

[jcarlyle]

Robin,

The greatest enemy of tires is heat. Heat comes from over loading,
under inflation, high speed, and tire design. To help yourself out,
first select a radial tire, because its design inherently creates less
heat than a bias ply tire. Second, regularly check the tire pressure
before and during the trip. It also doesn't hurt to feel the tire and
the hub for heat after the first 50 miles and at each stop, just to be
proactive about any developing problems.

Sway is a function of tow vehicle, but it also has to do with the tire
design. My Cobra came with P radial tires (for cars), and it became
much more stable (with the same car and load) when I put on ST radial
tires (for trailers). As Eric pointed out, ST tires have a speed limit
of 65 mph. But manufacturers say that you can bump that to 75 mph by
(1) running 10% less than the maximum tire pressure stamped on the
side of the tire and (2) derating the maximum load on the side of the
tire by 10%.

I would guess your Komet and glider probably weigh about 1800 pounds.
A load range C tire handles 1800 pounds, so it has double the load
capacity you need - thus a 10% reduction in pressure and load should
work at 75 mph just fine. I personally wouldn't drive that fast,
although I too have a lead foot. The handling and braking of the car/
trailer combination isn't what you're used to, and you can get into
trouble very quickly because of it.

As to tire make, I found that Duro, Maxxis and Denman were recommended
(in that order) most highly by owners. Goodyear Marathons were
variable. Carlisle and Titan were not recommended. The recommendations
came from multiple internet chat groups on boats and travel trailers.
I certainly have been happy with the Duro tires that I've put on both
my Cobra trailers. By the way, I had the 165/80R13 tire size, too, and
the 175/80R13 fit under/inside my Cobra fenders just fine.

-John

On Feb 22, 5:12 pm, Robin > wrote:
> I want to replace the tires on my Komet trailer. The original tire
> size is P165/80 R13, which is now hard to find.
>
> The choice seems to be either a Firestone passenger car radial in the
> correct size or a slightly taller Towmaster made by Greenball. The
> trailer tire will have a taller but stiffer sidewall. It will come a
> little closer to the fender, but my mechanic says less than half an
> inch closer. The size is 175/80 R13.
>
> I plan to tow about 75 mph most of the time. I really want to avoid
> sway.
>
> Any experience with these tires out there?
>
> Thanks,
> Robin RF

[jcarlyle]

I just noticed a serious problem with my previous post - if you want
to drive faster than the rated speed limit on a tire, for each 10 mph
above the rated speed limit you need to simultaneously (1) <reduce>
the maximum load limit on the tire sidewall by 10%, and (2) <increase>
the tire pressure by 10%, but not to more than the limit on the
sidewall.

Also, while sway is a function of the tow vehicle and tire design,
there are other things that cause sway. Some are distance from hitch
ball to tow vehicle rear axle, amount of weight on the trailer tongue,
aerodynamic effects cause by the tail housing fin, and rear suspension
of the tow vehicle.

Sorry for the errors - I wish I could edit the previous post.

-John

On Feb 23, 9:51 am, jcarlyle > wrote:
> Robin,
>
> The greatest enemy of tires is heat. Heat comes from over loading,
> under inflation, high speed, and tire design. To help yourself out,
> first select a radial tire, because its design inherently creates less
> heat than a bias ply tire. Second, regularly check the tire pressure
> before and during the trip. It also doesn't hurt to feel the tire and
> the hub for heat after the first 50 miles and at each stop, just to be
> proactive about any developing problems.
>
> Sway is a function of tow vehicle, but it also has to do with the tire
> design. My Cobra came with P radial tires (for cars), and it became
> much more stable (with the same car and load) when I put on ST radial
> tires (for trailers). As Eric pointed out, ST tires have a speed limit
> of 65 mph. But manufacturers say that you can bump that to 75 mph by
> (1) running 10% less than the maximum tire pressure stamped on the
> side of the tire and (2) derating the maximum load on the side of the
> tire by 10%.
>
> I would guess your Komet and glider probably weigh about 1800 pounds.
> A load range C tire handles 1800 pounds, so it has double the load
> capacity you need - thus a 10% reduction in pressure and load should
> work at 75 mph just fine. I personally wouldn't drive that fast,
> although I too have a lead foot. The handling and braking of the car/
> trailer combination isn't what you're used to, and you can get into
> trouble very quickly because of it.
>
> As to tire make, I found that Duro, Maxxis and Denman were recommended
> (in that order) most highly by owners. Goodyear Marathons were
> variable. Carlisle and Titan were not recommended. The recommendations
> came from multiple internet chat groups on boats and travel trailers.
> I certainly have been happy with the Duro tires that I've put on both
> my Cobra trailers. By the way, I had the 165/80R13 tire size, too, and
> the 175/80R13 fit under/inside my Cobra fenders just fine.

[Peter Wyld[_2_]]

The 80kph in Germany is a generalisation. If the trailer meets the
requirements it can be placarded to be towed at 100kph (subject to official
DoT inspection). This is certainly true of modern Cobra trailers which (I
believe) have shock absorbers and towball clamp. The downside is that the
trailer now carries a 100kph sticker, so cannot be towed faster in France
(where the towing limit is the same as a car, 110 or 130 kph, depending on
the road)


"Burt Compton - Marfa" > wrote in message
...
>
>> Of course the bottom line is to drive a little slower - as well as
>> having the right tyres on the trailer.
>>
>
> I just checked with my friend in Germany and confirmed that 80 km/hour
> is their max legal glider trailer towing speed.
> If we had the same law, that would be a max speed of only 50 MPH in
> the USA.
>
> So as much as the Germans like to drive fast in their cars, they
> apparently tow their glider trailers at a reasonable speed.
>
> My strategy is to maintain good tires, a tight hitch, start driving
> early and try not to stop (like not stopping to thermal on a cross
> country.)
> 60 MPH gets you there. Save gas / save your glider.
>
> Burt
> Marfa, west Texas
>

[Morgans[_2_]]

"Bruce" > wrote
>
> Double axle trailers do sway, and are in general more unwieldy than single
> axle trailers. A poorly designed trailer will sway at lower speed, adding
> an axle seems to increase the speed at which it goes wrong

Wow, does that go against everything I know to be true about trailers.

That same tire scrubbing you talked about while going around a corner is
exactly what makes the dual axle trailer more stable, if ALL other factors
were equal. Vortex shedding can certainly be a big issue, as is percentage
of tongue weight to overall trailer weight.

Many dual axle trailers do not carry enough tongue weight. Some also do
not have both springs mounted on a common pivot, which is not the correct
way to rig 2 axles.

Another factor against many glider trailers is that too much mass is too far
behind the axles. Any weight put further out behind the axle contributes to
dynamic instability, even if the tongue weight is correct.

I know having the axles further back makes cornering a more difficult issue,
but it really does help with stability, on the whole.

If you disagree with what I just posted, you and I will have to agree to
disagree, I guess.

Sunny skies!
--
Jim in NC
--
Jim in NC

[GM]

On Feb 23, 5:57*am, "Morgans" > wrote:
> "HL Falbaum" > wrote
>
> > Sway is more a function of the tow vehicle than anything else.
> > Demonstrated by towing same trailer, same road, same day, same speed--two
> > different vehicles, vastly different result.
>
> If you don't believe that, try towing ANY trailer with an uber short
> wheelbase, low overhang vehicle, like a Jeep. *A Jeep CJ vehicle will make
> ANY trailer sway, with any trailer weight and balance.
> --
> Jim in NC

That may be true for the CJ but I owned a 2-door Dodge 'Raider' aka
Mitsubishi 'Pajero'. This car had about the same dimensions as the CJ
but I towed my trailer from PA to CA and back without any sway
whatsoever. Good trailer tires and a good weight distribution in the
trailer plus the proper tounge weight are the key to happy trailering.
Uli

[Eric Greenwell]

Burt Compton - Marfa wrote:
>> Of course the bottom line is to drive a little slower - as well as
>> having the right tyres on the trailer.
>>
>>
>
> I just checked with my friend in Germany and confirmed that 80 km/hour
> is their max legal glider trailer towing speed.
> If we had the same law, that would be a max speed of only 50 MPH in
> the USA.
>
> So as much as the Germans like to drive fast in their cars, they
> apparently tow their glider trailers at a reasonable speed.
>
> My strategy is to maintain good tires, a tight hitch, start driving
> early and try not to stop (like not stopping to thermal on a cross
> country.)
> 60 MPH gets you there. Save gas / save your glider.
>
You save so much time when you don't have stop to change tires, and back
track to find the fender, then stop in town to get another tire. And if
you have find help to roll everything back up on to the tires .... well,
makes 60 seem OK!

One of my favorite trailer anecdotes is a friend that drove from Florida
to New Mexico for contest, buying 4 new tires along the way. Made good
time at 90 mph in between, though.

Lots of pilots do have tow vehicles and trailers that can tow safely at
75. The real problem is determining you have that combination without a
disaster if you are wrong.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

[Bruce]

Morgans wrote:
> "Bruce" > wrote
>> Double axle trailers do sway, and are in general more unwieldy than single
>> axle trailers. A poorly designed trailer will sway at lower speed, adding
>> an axle seems to increase the speed at which it goes wrong
>
> Wow, does that go against everything I know to be true about trailers.
>
> That same tire scrubbing you talked about while going around a corner is
> exactly what makes the dual axle trailer more stable, if ALL other factors
> were equal. Vortex shedding can certainly be a big issue, as is percentage
> of tongue weight to overall trailer weight.
>
> Many dual axle trailers do not carry enough tongue weight. Some also do
> not have both springs mounted on a common pivot, which is not the correct
> way to rig 2 axles.
>
> Another factor against many glider trailers is that too much mass is too far
> behind the axles. Any weight put further out behind the axle contributes to
> dynamic instability, even if the tongue weight is correct.
>
> I know having the axles further back makes cornering a more difficult issue,
> but it really does help with stability, on the whole.
>
> If you disagree with what I just posted, you and I will have to agree to
> disagree, I guess.
>
> Sunny skies!
Hi Jim

I agree with you - no need to agree to disagree. A correctly designed
common pivot double axle will be more directionally stable than an
equally well designed single axle. But the statement that just adding
another axle will invariably improve things is false.

A poor design on a double axle often makes things worse rather than
better. Some genius added an afterthought axle to my Kestrel's trailer.
Now it has two different design axles, both suspended with cart (leaf)
springs) with different lateral stiffness and compliance. The fixed
front/pivoting rear shackle design on the axles allow - and in fact
force the two axles to move out of parallel when the wheels move over an
obstacle affecting only one side. Result is lots of steering from the
trailer. If the trailer rocks from side to side (as in vortex shedding)
there are modes when the axle steer amplifies the movement. That's a
recipe for disaster.

So again - there is no substitute for good design, and if you don't have
the resources for that, rather stick to a simpler single axle design.
Unless you can analyse the suspension geometry simpler is better.

That said - as has previously been posted - the tow vehicle and
tow/trailer compatibility is probably more important. Even the Kestrel
franken trailer is relatively easy to tow with a volvo XC70 as long as
you stay below 100km/h but wildly unstable behind a 1 ton pickup at 80.

There is one unequivocal advantage to double axle setups, in that the
ride is more consistent for the glider - the horisontal difference
between wheels tends to make the ride smoother on rough surfaces.

Bruce

--- news://freenews.netfront.net/ - complaints: ---

[HL Falbaum[_2_]]

"GM" > wrote in message
...
On Feb 23, 5:57 am, "Morgans" > wrote:
> "HL Falbaum" > wrote
>
> > Sway is more a function of the tow vehicle than anything else.
> > Demonstrated by towing same trailer, same road, same day, same
> > speed--two
> > different vehicles, vastly different result.
>
> If you don't believe that, try towing ANY trailer with an uber short
> wheelbase, low overhang vehicle, like a Jeep. A Jeep CJ vehicle will make
> ANY trailer sway, with any trailer weight and balance.
> --
> Jim in NC

That may be true for the CJ but I owned a 2-door Dodge 'Raider' aka
Mitsubishi 'Pajero'. This car had about the same dimensions as the CJ
but I towed my trailer from PA to CA and back without any sway
whatsoever. Good trailer tires and a good weight distribution in the
trailer plus the proper tounge weight are the key to happy trailering.
Uli

Not to belabor the point, but the two vehicles in my experiment were similar
size, weight, overhang. The real difference was suspension stiffness. A soft
'98 Chevrolet Tahoe, and a (about same year) Ford Expedition. The Ford had a
stiffer suspension and more precise steering. The Chev was soft and more
"loose", the sway always started at about 70mph. The Tahoe was replaced with
a '03 Avalanche---stiffer suspension, tighter steering. Same trailer was
then towed without sway at any speed.

Hartley Falbaum
"KF" USA

[mattm[_2_]]

OK, so a proper fit between the hitch and ball is important, too.
What do I do with
my Cobra trailer that fits a 50mm ball? I actually *do* have a 50mm
ball but it has a
1" shank. However, my car has a 1.25" hitch receiver (factory
installed), and I can't
find any fittings that will take a 1" shank. For the moment I'm just
using a 1 7/8"
ball (47.6mm) since the trailer just goes from the tiedown to the end
of the runway,
and I've heard the horror stories of using a 2" ball (50.8mm). Any
ideas that don't
cost an arm and a leg (such as "buy a new car")?

-- Matt

[HL Falbaum[_2_]]

Matt;

It is a good idea to have options. So, if someone else has to come get you
with their car, they are likely to have a 1 7/8" or a 2" ball.

It would be easy to replace the hitch on the trailer with either a 2" or 1
7/8" . These are commonly available, just bolt on. Then sell the 50mm ball.

For little money, a welding shop could make a custom mount---50mm ball with
1" shank into 2"x 1/4"x 1/4" square tube, welded onto 1 1/4 " tubing stub
and insert into your receiver.

50mm hitch on 1 7/8" ball is just a little sloppy--probably a minor factor,
but best to change something.

--
Hartley Falbaum

"mattm" > wrote in message
...
> OK, so a proper fit between the hitch and ball is important, too.
> What do I do with
> my Cobra trailer that fits a 50mm ball? I actually *do* have a 50mm
> ball but it has a
> 1" shank. However, my car has a 1.25" hitch receiver (factory
> installed), and I can't
> find any fittings that will take a 1" shank. For the moment I'm just
> using a 1 7/8"
> ball (47.6mm) since the trailer just goes from the tiedown to the end
> of the runway,
> and I've heard the horror stories of using a 2" ball (50.8mm). Any
> ideas that don't
> cost an arm and a leg (such as "buy a new car")?
>
> -- Matt

[Morgans[_2_]]

"HL Falbaum" > wrote

> Not to belabor the point, but the two vehicles in my experiment were
> similar size, weight, overhang. The real difference was suspension
> stiffness. A soft '98 Chevrolet Tahoe, and a (about same year) Ford
> Expedition. The Ford had a stiffer suspension and more precise steering.
> The Chev was soft and more "loose", the sway always started at about
> 70mph. The Tahoe was replaced with a '03 Avalanche---stiffer suspension,
> tighter steering. Same trailer was then towed without sway at any speed.

Interesting. In my case, a Chevy Citation vs a CJ, and the CJ certainly had
the stiffer suspension, and it was worse. I think the tighness of the
steering may be playing a bigger factor than we are giving it credit for.
--
Jim in NC

[Morgans[_2_]]

"HL Falbaum" > wrote

> It is a good idea to have options. So, if someone else has to come get you
> with their car, they are likely to have a 1 7/8" or a 2" ball.
>
> It would be easy to replace the hitch on the trailer with either a 2" or 1
> 7/8" . These are commonly available, just bolt on. Then sell the 50mm
> ball.
>
> For little money, a welding shop could make a custom mount---50mm ball
> with 1" shank into 2"x 1/4"x 1/4" square tube, welded onto 1 1/4 " tubing
> stub and insert into your receiver.
>
> 50mm hitch on 1 7/8" ball is just a little sloppy--probably a minor
> factor, but best to change something.

I agree. Get a welding shop (if you are not able to do it yourself) to
change out the trailer hitch for a standard size like 2". (standard in this
area, anyway) Also, custom fit the 1 1/4" stub to your receiver. I have
usually found they fit loose as crap, unless you do something to make it fit
right.

I had good luck doing this by running two beads of weld down the length of
the hitch stub on two adjacent sides of the stub, then grind it down to a
"just right - slide in, but no wobble" fit. It is amazing how that can
reduce sway, and quiet down the ride down the road.

Anyone else with a sway problem have a sloppy fitting hitch - receiver fit?
Anyone do something to tighten up the fit?
--
Jim in NC

[vontresc]

On Feb 25, 12:03*am, "Morgans" > wrote:
> "HL Falbaum" > wrote
>
> > It is a good idea to have options. So, if someone else has to come get you
> > with their car, they are likely to have a 1 7/8" or a 2" ball.
>
> > It would be easy to replace the hitch on the trailer with either a 2" or 1
> > 7/8" . These are commonly available, just bolt on. Then sell the 50mm
> > ball.
>
> > For little money, a welding shop could make a custom mount---50mm ball
> > with 1" shank into 2"x 1/4"x 1/4" square tube, welded onto 1 1/4 " tubing
> > stub and insert into your receiver.
>
> > 50mm hitch on 1 7/8" ball is just a little sloppy--probably a minor
> > factor, but best to change something.
>
> *I agree. *Get a welding shop (if you are not able to do it yourself) to
> change out the trailer hitch for a standard size like 2". *(standard in this
> area, anyway) *Also, custom fit the 1 1/4" stub to your receiver. *I have
> usually found they fit loose as crap, unless you do something to make it fit
> right.
>
> I had good luck doing this by running two beads of weld down the length of
> the hitch stub on two adjacent sides of the stub, then grind it down to a
> "just right - slide in, but no wobble" fit. *It is amazing how that can
> reduce sway, and quiet down the ride down the road.
>
> Anyone else with a sway problem have a sloppy fitting hitch - receiver fit?
> Anyone do something to tighten up the fit?
> --
> Jim in NC

Ok there seems to be a lot of OWT, and other imprecise anecdotal
evidence about trailers and towing floating out there. Has anyone like
an AKAFLIEG group ever done some trailer dynamocs studies????

Peter

[Burt Compton - Marfa]

>
> I had good luck doing this by running two beads of weld down the length of
> the hitch stub on two adjacent sides of the stub, then grind it down to a
> "just right - slide in, but no wobble" fit. *It is amazing how that can
> reduce sway, and quiet down the ride down the road.
>
> Anyone else with a sway problem have a sloppy fitting hitch - receiver fit?
> Anyone do something to tighten up the fit?


Yes, get an "anti-rattle" J bolt device for your receiver for about
$23. from Redtrailers.com

See it at http://www.redtrailers.com/ShowItem.asp?id=63201

You may need a shop to drill an extra hole in the side of your steel
hitch.
Includes a lock device.

A fellow Texas glider pilot suggested it. It tightens up nicely and
stops the rattling.
This must help with sway -- but I really don't have much sway because
I don't drive my glider trailers (5) over 60 MPH.


Burt
"The Turtle", just easin' on down the road
from Marfa, in southwest Texas, USA

[HL Falbaum[_2_]]

"Morgans" > wrote in message
...
>
> "HL Falbaum" > wrote
>
>> It is a good idea to have options. So, if someone else has to come get
>> you with their car, they are likely to have a 1 7/8" or a 2" ball.
>>
> I agree. Get a welding shop (if you are not able to do it yourself) to
> change out the trailer hitch for a standard size like 2". (standard in
> this area, anyway) Also, custom fit the 1 1/4" stub to your receiver. I
> have usually found they fit loose as crap, unless you do something to make
> it fit right.
>
> I had good luck doing this by running two beads of weld down the length of
> the hitch stub on two adjacent sides of the stub, then grind it down to a
> "just right - slide in, but no wobble" fit. It is amazing how that can
> reduce sway, and quiet down the ride down the road.
>
> Anyone else with a sway problem have a sloppy fitting hitch - receiver
> fit? Anyone do something to tighten up the fit?
> --
> Jim in NC
>

At the suggestion of someone else, I drove large nails into the gap between
stub and receiver, to remove the "slop". Made absolutely no difference with
sway in the Tahoe.

As to driving slowly, I had to do that with the Tahoe. Sway started anyway
when I was passed by 75mph Semis.

Hartley Falbaum

[Morgans[_2_]]

"Burt Compton - Marfa" > wrote

Yes, get an "anti-rattle" J bolt device for your receiver for about
$23. from Redtrailers.com

I had not seen that product, but my method is cheaper, and faster! ;-)

I change hitches frequently, (different height trailer hitches required) so
quick no fuss solutions are valuable to me.
--
Jim in NC

[Burt Compton - Marfa]

Jim,
You asked if "anyone do something to tighten up the fit?"
so I offered readers the off-the-shelf J-Bolt idea as an additional
method.

I have 5 glider trailers and several other equipment trailers.
I use a variable hitch ball unit that I can quickly move up or down
with a "quickie" pin.
The anti-rattle J-bolt stays in place underneath in the main 2"
receiver.

Your Do It Yourself welding method works as well. Indeed, it is
brilliant!
Hartley's nails in the receiver idea didn't sound so appealing if they
worked loose and fell on the road, but it's yet another good and fast
DIY idea!


Burt
Marfa Gliders Soaring Center, west Texas USA

PS A student of mine decided to "air up" all my pneumatic tires on
my aircraft, trailers, bikes, cars, hand-trucks, O2 carts, etc.
We lost count after 110 as we were laughing so hard about the amazing
number. Thank goodness for "slime"!

[Craig[_2_]]

On Feb 25, 5:49*am, vontresc > wrote:
> On Feb 25, 12:03*am, "Morgans" > wrote:
>
>
>
> > "HL Falbaum" > wrote
>
> > > It is a good idea to have options. So, if someone else has to come get you
> > > with their car, they are likely to have a 1 7/8" or a 2" ball.
>
> > > It would be easy to replace the hitch on the trailer with either a 2" or 1
> > > 7/8" . These are commonly available, just bolt on. Then sell the 50mm
> > > ball.
>
> > > For little money, a welding shop could make a custom mount---50mm ball
> > > with 1" shank into 2"x 1/4"x 1/4" square tube, welded onto 1 1/4 " tubing
> > > stub and insert into your receiver.
>
> > > 50mm hitch on 1 7/8" ball is just a little sloppy--probably a minor
> > > factor, but best to change something.
>
> > *I agree. *Get a welding shop (if you are not able to do it yourself) to
> > change out the trailer hitch for a standard size like 2". *(standard in this
> > area, anyway) *Also, custom fit the 1 1/4" stub to your receiver. *I have
> > usually found they fit loose as crap, unless you do something to make it fit
> > right.
>
> > I had good luck doing this by running two beads of weld down the length of
> > the hitch stub on two adjacent sides of the stub, then grind it down to a
> > "just right - slide in, but no wobble" fit. *It is amazing how that can
> > reduce sway, and quiet down the ride down the road.
>
> > Anyone else with a sway problem have a sloppy fitting hitch - receiver fit?
> > Anyone do something to tighten up the fit?
> > --
> > Jim in NC
>
> Ok there seems to be a lot of OWT, and other imprecise anecdotal
> evidence about trailers and towing floating out there. Has anyone like
> an AKAFLIEG group ever done some trailer dynamocs studies????
>
> Peter

This is a favorite wintertime thread & is as regular as the leaves
turning colors.
Rigorous engineering work has been done on this subject. See article
by Funston in Technical Soaring July 1989, p90-95.

Can't wait for flying to start.

Craig

[Eric Greenwell]

Morgans wrote:
>> 50mm hitch on 1 7/8" ball is just a little sloppy--probably a minor
>> factor, but best to change something.
>>
>
> I agree. Get a welding shop (if you are not able to do it yourself) to
> change out the trailer hitch for a standard size like 2". (standard in this
> area, anyway) Also, custom fit the 1 1/4" stub to your receiver. I have
> usually found they fit loose as crap, unless you do something to make it fit
> right.
>
> I had good luck doing this by running two beads of weld down the length of
> the hitch stub on two adjacent sides of the stub, then grind it down to a
> "just right - slide in, but no wobble" fit. It is amazing how that can
> reduce sway, and quiet down the ride down the road.
>
> Anyone else with a sway problem have a sloppy fitting hitch - receiver fit?
> Anyone do something to tighten up the fit?
>
It seems remarkable and counter-intuitive that even 1/8" (a lot more
than my hitches) of total slop at one end of a 30 foot long trailer
could have any influence at all. Since the tires are approximately in
the middle, that'd be only an 1/8" at the tail. My trailer is stable,
yet I can still see the tail wagging 1 to 3 inches at times as I'm
driving, far more than a loose hitch would cause.

Perhaps there were some other changes made at the same time, like
changing tire pressures, moving stuff around in the trailer?

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

[Morgans[_2_]]

"Burt Compton - Marfa" > wrote

> You asked if "anyone do something to tighten up the fit?"
> so I offered readers the off-the-shelf J-Bolt idea as an additional
> method.

Yep, and I like it. I think it is likely a good product, but pricey, and
possibly too much hassle for some. Ideal for those who can leave the same
hitch in nearly all of the time, I would think.
--
Jim in NC

[Morgans[_2_]]

"Eric Greenwell" > wrote
> It seems remarkable and counter-intuitive that even 1/8" (a lot more
> than my hitches) of total slop at one end of a 30 foot long trailer could
> have any influence at all. Since the tires are approximately in the
> middle, that'd be only an 1/8" at the tail. My trailer is stable, yet I
> can still see the tail wagging 1 to 3 inches at times as I'm driving, far
> more than a loose hitch would cause.

Probably true. I stated that a bit strongly, perhaps. The loose hitch
probably does not do much to cause a sway.

If a trailer was verging on unstable, it could be conceiveable that it would
only take a small factor to start exciting the system, and then the trailer
allows the oscillations to amplify and build on their own.

Sway is like a harmonic vibration. If it starts to vibrate, or sway, it can
self excite and built on the small wiggle that got it started.

Still, I guess what I was meaning to ask was if people had a sloppy fit that
rattled back and forth that they had to deal with. I can not stand to hear
something like a loose hitch rattle as I head on down the road. Something
had to be done, and the welds are what I came up with. I tried the metal
shims (like the nails that someone mentioned) and they eventually fell out.
I put my gray matter to the problem and the welds building the fit tighter
is what I ended up going with.
--
Jim in NC
>
> Perhaps there were some other changes made at the same time, like changing
> tire pressures, moving stuff around in the trailer?
>
> --
> Eric Greenwell - Washington State, USA (netto to net to email me)
>
> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
> http://tinyurl.com/yb3xywl
>
> - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
> you need to know tinyurl.com/yfs7tnz

[jcarlyle]

I'd love to read this article. Got a link? Or can you send me an
electronic copy? Thanks!

-John


On Feb 25, 9:59 pm, Craig > wrote:
> This is a favorite wintertime thread & is as regular as the leaves
> turning colors.
> Rigorous engineering work has been done on this subject. See article
> by Funston in Technical Soaring July 1989, p90-95.

[Craig[_2_]]

On Feb 26, 4:57*am, jcarlyle > wrote:
> I'd love to read this article. Got a link? Or can you send me an
> electronic copy? Thanks!
>
> -John
>
> On Feb 25, 9:59 pm, Craig > wrote:
>
> > This is a favorite wintertime thread & is as regular as the leaves
> > turning colors.
> > Rigorous engineering work has been done on this subject. See article
> > by Funston in Technical Soaring July 1989, p90-95.

I went searching last night for a copy and was unable to find
anything. Hopefully the Technical Soaring series will be included in
SSA's scanning project. I can get you in touch with the Author if you
want to contact me by email. You can find a number of threads that
include some of the results if you put "funston trailer sway" into the
group search.

The primary conclusion is to have the axle(s) as far back as possible
while maintaining a reasonable tongue weight. Reducing the polar
moment of inertia of the trailer + glider is useful, but there isn't
much we can do about the mass distribution of the sailplane. From a
towing standpoint the most effective solution is to turn the trailer
around so the wing roots are at the back of the trailer. This allows
moving the axle rearward while maintaining very reasonable tongue
weight. It does have the disadvantage of requiring assembly over the
tongue of the trailer. Spindleberger is a very knowledgeable trailer
manufacturer, but their decisions have to be driven by what they can
sell and loading over the tongue doesn't sell. The speed limits for
trailers in Germany is also slower than we tend to drive in the US so
the stability issues don't show up. My Komet - minivan combination is
fine up to 100 kph, but is a handful over 115 kph. I've had a tongue
loading trailer in the past and it was rock solid as fast as I wanted
to go. Most times I'd forget it was even behind. Anyways there's
lots of historical discussion on the archive and it's an entertaining
diversion.

Cheers,
Craig

[[email protected]]

On Feb 26, 1:16*pm, Craig > wrote:
> On Feb 26, 4:57*am, jcarlyle > wrote:
>
> > I'd love to read this article. Got a link? Or can you send me an
> > electronic copy? Thanks!
>
> > -John
>
> > On Feb 25, 9:59 pm, Craig > wrote:
>
> > > This is a favorite wintertime thread & is as regular as the leaves
> > > turning colors.
> > > Rigorous engineering work has been done on this subject. See article
> > > by Funston in Technical Soaring July 1989, p90-95.
>
> I went searching last night for a copy and was unable to find
> anything. *Hopefully the Technical Soaring series will be included in
> SSA's scanning project. *I can get you in touch with the Author if you
> want to contact me by email. *You can find a number of threads that
> include some of the results if you put "funston trailer sway" into the
> group search.
>
> The primary conclusion is to have the axle(s) as far back as possible
> while maintaining a reasonable tongue weight. *Reducing the polar
> moment of inertia of the trailer + glider is useful, but there isn't
> much we can do about the mass distribution of the sailplane. *From a
> towing standpoint the most effective solution is to turn the trailer
> around so the wing roots are at the back of the trailer. *This allows
> moving the axle rearward while maintaining very reasonable tongue
> weight. *It does have the disadvantage of requiring assembly over the
> tongue of the trailer. Spindleberger is a very knowledgeable trailer
> manufacturer, but their decisions have to be driven by what they can
> sell and loading over the tongue doesn't sell. The speed limits for
> trailers in Germany is also slower than we tend to drive in the US so
> the stability issues don't show up. *My Komet - minivan combination is
> fine up to 100 kph, but is a handful over 115 kph. *I've had a tongue
> loading trailer in the past and it was rock solid as fast as I wanted
> to go. *Most times I'd forget it was even behind. *Anyways there's
> lots of historical discussion on the archive and it's an entertaining
> diversion.
>
> Cheers,
> Craig

Lots of variables: A few I have learned about:
Flexible tongue. My old PIK trailer had a fairly flexible tongue/
frame. After I rolled it over(another story), I rebuilt with about a 8
inch longer tongue(entend distance between pivot and wheels and one
size larger tubing in frame. Result- trailer that liked to sway then
towed straight as an arrow.
Aft weight in trailer. Take the extra ramp, tail ballast weight, and
other stuff out and move to the front. I have found a perceptible
improvement. This is about polar moment obviously.
From my experience, slightly loose fitting tow adaptors don't mean
squat. If the whole "system" is damped properly, that won't mean a
thing- except for clanky annoying noise.
Snow/ice on trailer - TAKE IT OFF!
Tire inflation- High end of mfr's suggested stiffens sidewalls and
reduces sway.
Tire inflation- car. Pump 'em up. Stiffer helps sway and fuel economy.
Hitch overhang- keep to a minimum, especially on short wheelbase
vehicles.
Put heavy extra stuff in the vehicle between the wheels. Making the
trailer heavier than needed in front upsets the natuarl suspension
setup in the car.
FWIW
UH

[jcarlyle]

Thank you, Craig! I did a search of RAS, and found some of the threads
you mentioned.

Interesting, your coonclusion about moving the trailer axle back. My
1983 Cobra (with an ASW-19 in it) was an extremely stable trailer. The
2000 Cobra holding my LS8-18 is not nearly as stable. Same car (BMW
530), same tongue weight (100 lbs), same tires (Duro ST175/80R13).
However, the axle for the 2000 Cobra is about 6 feet closer to the
hitch ball (factory positioning). The new trailer is also taller than
the old one, and doesn't have the lowered front that the old trailer
did, either. I'm sure that Herr Spindelberger had a reason for the
axle placement (maybe the 18 m tips being carried at the top rear?),
but I'm thinking about moving the axle back a few feet.

Regards,
John

On Feb 26, 1:16 pm, Craig > wrote:
> I went searching last night for a copy and was unable to find
> anything. Hopefully the Technical Soaring series will be included in
> SSA's scanning project. I can get you in touch with the Author if you
> want to contact me by email. You can find a number of threads that
> include some of the results if you put "funston trailer sway" into the
> group search.
>
> The primary conclusion is to have the axle(s) as far back as possible
> while maintaining a reasonable tongue weight. Reducing the polar
> moment of inertia of the trailer + glider is useful, but there isn't
> much we can do about the mass distribution of the sailplane. From a
> towing standpoint the most effective solution is to turn the trailer
> around so the wing roots are at the back of the trailer. This allows
> moving the axle rearward while maintaining very reasonable tongue
> weight. It does have the disadvantage of requiring assembly over the
> tongue of the trailer. Spindleberger is a very knowledgeable trailer
> manufacturer, but their decisions have to be driven by what they can
> sell and loading over the tongue doesn't sell. The speed limits for
> trailers in Germany is also slower than we tend to drive in the US so
> the stability issues don't show up. My Komet - minivan combination is
> fine up to 100 kph, but is a handful over 115 kph. I've had a tongue
> loading trailer in the past and it was rock solid as fast as I wanted
> to go. Most times I'd forget it was even behind. Anyways there's
> lots of historical discussion on the archive and it's an entertaining
> diversion.

[Craig[_2_]]

On Feb 26, 11:56*am, jcarlyle > wrote:
> Thank you, Craig! I did a search of RAS, and found some of the threads
> you mentioned.
>
> Interesting, your coonclusion about moving the trailer axle back. My
> 1983 Cobra (with an ASW-19 in it) was an extremely stable trailer. The
> 2000 Cobra holding my LS8-18 is not nearly as stable. Same car (BMW
> 530), same tongue weight (100 lbs), same tires (Duro ST175/80R13).
> However, the axle for the 2000 Cobra is about 6 feet closer to the
> hitch ball (factory positioning). The new trailer is also taller than
> the old one, and doesn't have the lowered front that the old trailer
> did, either. *I'm sure that Herr Spindelberger had a reason for the
> axle placement (maybe the 18 m tips being carried at the top rear?),
> but I'm thinking about moving the axle back a few feet.
>
> Regards,
> John
>
> On Feb 26, 1:16 pm, Craig > wrote:
>
> > I went searching last night for a copy and was unable to find
> > anything. *Hopefully the Technical Soaring series will be included in
> > SSA's scanning project. *I can get you in touch with the Author if you
> > want to contact me by email. *You can find a number of threads that
> > include some of the results if you put "funston trailer sway" into the
> > group search.
>
> > The primary conclusion is to have the axle(s) as far back as possible
> > while maintaining a reasonable tongue weight. *Reducing the polar
> > moment of inertia of the trailer + glider is useful, but there isn't
> > much we can do about the mass distribution of the sailplane. *From a
> > towing standpoint the most effective solution is to turn the trailer
> > around so the wing roots are at the back of the trailer. *This allows
> > moving the axle rearward while maintaining very reasonable tongue
> > weight. *It does have the disadvantage of requiring assembly over the
> > tongue of the trailer. Spindleberger is a very knowledgeable trailer
> > manufacturer, but their decisions have to be driven by what they can
> > sell and loading over the tongue doesn't sell. The speed limits for
> > trailers in Germany is also slower than we tend to drive in the US so
> > the stability issues don't show up. *My Komet - minivan combination is
> > fine up to 100 kph, but is a handful over 115 kph. *I've had a tongue
> > loading trailer in the past and it was rock solid as fast as I wanted
> > to go. *Most times I'd forget it was even behind. *Anyways there's
> > lots of historical discussion on the archive and it's an entertaining
> > diversion.

Interesting comparison of the two trailers. Moving the axle back even
a fraction of a foot can sometimes be enough to make a noticeable
difference. Hank's comment about longer tongues is also a good one.
I've pulled a Schreder trailer with a 15m ship that had a custom
extended tongue made of aluminum to keep the weight down. That
trailer also towed very well.

Craig

[Morgans[_2_]]

"jcarlyle" > wrote

> same tongue weight (100 lbs)

Wow, that seems light. What is the overall weight of the trailer?
--
Jim in NC

[Eric Greenwell]

Craig wrote:
> On Feb 26, 4:57 am, jcarlyle > wrote:
>
>> I'd love to read this article. Got a link? Or can you send me an
>> electronic copy? Thanks!
>>
>> -John
>>
>> On Feb 25, 9:59 pm, Craig > wrote:
>>
>>
>>> This is a favorite wintertime thread & is as regular as the leaves
>>> turning colors.
>>> Rigorous engineering work has been done on this subject. See article
>>> by Funston in Technical Soaring July 1989, p90-95.
>>>
>
> I went searching last night for a copy and was unable to find
> anything. Hopefully the Technical Soaring series will be included in
> SSA's scanning project. I can get you in touch with the Author if you
> want to contact me by email. You can find a number of threads that
> include some of the results if you put "funston trailer sway" into the
> group search.
I thought (at least some of) Technical Soaring was online at the OSTIV
website, but I haven't tried to find them. The SSA website might say
where they are. It would be great to have them on the SSA site like Soaring.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

[Craig[_2_]]

On Feb 26, 7:10*pm, Eric Greenwell > wrote:
> Craig wrote:
> > On Feb 26, 4:57 am, jcarlyle > wrote:
>
> >> I'd love to read this article. Got a link? Or can you send me an
> >> electronic copy? Thanks!
>
> >> -John
>
> >> On Feb 25, 9:59 pm, Craig > wrote:
>
> >>> This is a favorite wintertime thread & is as regular as the leaves
> >>> turning colors.
> >>> Rigorous engineering work has been done on this subject. See article
> >>> by Funston in Technical Soaring July 1989, p90-95.
>
> > I went searching last night for a copy and was unable to find
> > anything. *Hopefully the Technical Soaring series will be included in
> > SSA's scanning project. *I can get you in touch with the Author if you
> > want to contact me by email. *You can find a number of threads that
> > include some of the results if you put "funston trailer sway" into the
> > group search.
>
> I thought (at least some of) Technical Soaring was online at the OSTIV
> website, but I haven't tried to find them. The SSA website might say
> where they are. It would be great to have them on the SSA site like Soaring.
>
> --
> Eric Greenwell - Washington State, USA (netto to net to email me)
>
> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl
>
> - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

I took a look through OSTIV, but wasn't able to find anything. There
may be a members area that has some of that available. Does anyone
know?

Craig