Re: Trailer weight distribution demonstration

[[email protected]]

On Tuesday, October 4, 2016 at 8:22:12 PM UTC-4, waremark wrote:
> So what is the message? We are normally told not to have much weight on the nose of the trailer, which presumably would adversely affect the balance of the car. To achieve that I have to put luggage etc at the back of my trailer (I tow an Arcus M in a Cobra trailer). What should I do? How much weight should I have on the hook?

The video is a good illustration of the effect of adding mass far away from the pivot point. Anything that adds to the polar moment about the pivot point reduces stability.
The concept of having enough tongue weight is mostly a result of experience that shows tail heavy trailers tow worse than ones that are not.
Consider adding and using a center drawer to stow some heavier stuff near the axle.
Maybe put a few heavy things in the vehicle between the axles.
Also look at what is in the trailer that may not really be needed.
I move the tail weight(13lb for fatty) from the tail to the cockpit when towing my '29. Even that adds a small amount of added stability.
FWIW
UH

[Charlie M. (UH & 002 owner/pilot)]

I've wondered if adding a small (1/4" - 3/8") anti sway bar to the trailer axle would help in most situations. Granted, proper weight is best, but the anti sway bar may widen the margin.
Thoughts?

[Don Johnstone[_4_]]

At 14:59 05 October 2016, Charlie M. UH & 002 owner/pilot wrote:
>I've wondered if adding a small (1/4" - 3/8") anti sway bar to the
trailer
>axle would help in most situations. Granted, proper weight is best, but
the
>anti sway bar may widen the margin.
>Thoughts?

Weighting is important, no doubt. Reducing the weight and therefore the
inertia on the anchored end of the trailer does reduce the possibility of
any swing increasing by increasing the ability of the towing vehicle to
damp the oscillations. The trigger for these oscillations is aerodynamic
caused by the low pressure area between two vehicles as they overtake/are
overtaken. The situation is made worse if the vertical surface is the same
or more than the area in front of the axle. Cobras and Komets are designed
to reduce the side area behind the axle.
I towed a trailer, containing a Grob 103 back from Holland. The nose weight
was close to the maximum limit allowed for my car, theoretically the best
situation to improve stability, however it swayed readily. I have just
towed the same combination over 300miles. Before leaving I increased the
tyre pressures on the trailer from 35psi to 55psi (Max 65psi). The trailer
now tows with no swaying up to the maximum speed limit in the UK (70mph).
It does allow towing at just below 60mph which means I can avoid being
overtaken by large trucks, the condition which is most likely to trigger
swaying. Tyre pressure appears to have a large influence on the stability
of the trailer, greater than loading. Vertical instability is now the major
problem, easily fixed by a stabiliser.

[[email protected]]

In the early 1970s, my father and I loaded our damaged 201 Libelle into a tall, straight-topped, corrugated-aluminum-and-steel-tube trailer meant for a 16.5M Diamant. Almost unbelievably given the weight of the Diamant wing, it was set up to load wingtips first from the rear. So that's how we loaded the Libelle wings: i.e., spars aft. The fuselage we just rolled into the trailer and tied it down as best we could using the tail tiedown bracket that was in place.

As you can imagine with our short-span bird sitting well aft of where the Diamant would be, the trailer was somewhat tail heavy. Off we went in the family Chevy station wagon (read: heavy, full-size American car from that era) from Cincinnati to the Gehrleins' repair facility in Erie, PA, a 350 mile journey that should have taken about 5 hours.

I have long since suppressed most memories of that terrifying trip but not the lessons of that masters-level, crash course (no pun intended, fortunately) in trailer control. Everything I know about keeping uncooperative trailers in line I learned that day. I almost had to pry my fingers off the steering wheel when we arrived.

I learned how to slow going uphill so I could avoid slowing (not good) or braking (really bad!), and even accelerate slightly if needed on the way down the hill. How to accelerate slightly when being passed by a large truck. Or anything larger than a motorcycle, for that matter. How to watch in the mirror to make certain there were no large trucks overtaking as we reached the top of a hill.

How never to touch the brakes going around a curve. How to hit the throttle to straighten out an incipient tail wag, including when going downhill being passed by a large truck (see "how to slow going uphill", above).

I don't know why we didn't just stop and move things forward, or pile a bunch of stuff in the front of the trailer to get some tongue load. I guess we didn't know any better. Or assumed it was some fundamental flaw in trailer stability. The empty trailer towed fine on the way home, unsurprisingly. If I recall correctly, the subsequent owner of that glider moved the axle back to get some more weight on the tongue even with the heavier, longer-span Diamant in the box, and it towed fine.

To this day, almost 45 years later, I'm still wary of the little twitch in the steering wheel that signals the trailer is moving around and could get squirrelly.

Chip Bearden

[[email protected]]

On Wednesday, October 5, 2016 at 4:50:51 PM UTC-4, wrote:
> In the early 1970s, my father and I loaded our damaged 201 Libelle into a tall, straight-topped, corrugated-aluminum-and-steel-tube trailer meant for a 16.5M Diamant. Almost unbelievably given the weight of the Diamant wing, it was set up to load wingtips first from the rear. So that's how we loaded the Libelle wings: i.e., spars aft. The fuselage we just rolled into the trailer and tied it down as best we could using the tail tiedown bracket that was in place.
>
> As you can imagine with our short-span bird sitting well aft of where the Diamant would be, the trailer was somewhat tail heavy. Off we went in the family Chevy station wagon (read: heavy, full-size American car from that era) from Cincinnati to the Gehrleins' repair facility in Erie, PA, a 350 mile journey that should have taken about 5 hours.
>
> I have long since suppressed most memories of that terrifying trip but not the lessons of that masters-level, crash course (no pun intended, fortunately) in trailer control. Everything I know about keeping uncooperative trailers in line I learned that day. I almost had to pry my fingers off the steering wheel when we arrived.
>
> I learned how to slow going uphill so I could avoid slowing (not good) or braking (really bad!), and even accelerate slightly if needed on the way down the hill. How to accelerate slightly when being passed by a large truck.. Or anything larger than a motorcycle, for that matter. How to watch in the mirror to make certain there were no large trucks overtaking as we reached the top of a hill.
>
> How never to touch the brakes going around a curve. How to hit the throttle to straighten out an incipient tail wag, including when going downhill being passed by a large truck (see "how to slow going uphill", above).
>
> I don't know why we didn't just stop and move things forward, or pile a bunch of stuff in the front of the trailer to get some tongue load. I guess we didn't know any better. Or assumed it was some fundamental flaw in trailer stability. The empty trailer towed fine on the way home, unsurprisingly. If I recall correctly, the subsequent owner of that glider moved the axle back to get some more weight on the tongue even with the heavier, longer-span Diamant in the box, and it towed fine.
>
> To this day, almost 45 years later, I'm still wary of the little twitch in the steering wheel that signals the trailer is moving around and could get squirrelly.
>
> Chip Bearden

My PIK trailer was a bit wiggly when pulling with my little Triumph TR7. It did get rolled when we got run off the road by a truck and ended up with an uncontrollable divergent oscillation.
The glider did not get hurt and flew in my first Nationals 2 days later(another story).
When repairing the trailer I replaced the front frame members with one size larger tubing and extended the tongue area about 8 inches. It was like a different trailer and never wiggled again. Tongue weight was almost exactly the same so my theory was that the longer arm from the tow ball to the oscillation dampers(wheels) was enough to entirely change the dynamics.
FWIW
UH

[Bob Whelan[_3_]]

On 10/5/2016 2:50 PM, wrote:
> In the early 1970s...
<Snip...>
> I have long since suppressed most memories of that terrifying trip but not
> the lessons of that masters-level, crash course (no pun intended,
> fortunately) in trailer control. Everything I know about keeping
> uncooperative trailers in line I learned that day.

> I learned how to slow going uphill so I could avoid slowing (not good) or
> braking (really bad!), and even accelerate slightly if needed on the way
> down the hill. How to accelerate slightly when being passed by a large
> truck. Or anything larger than a motorcycle, for that matter. How to watch
> in the mirror to make certain there were no large trucks overtaking as we
> reached the top of a hill.
>
> How never to touch the brakes going around a curve. How to hit the throttle
> to straighten out an incipient tail wag, including when going downhill
> being passed by a large truck (see "how to slow going uphill", above).

For readers not yet personally acquainted with the need "to hit the throttle
to straighten out an incipient tail wag, including going downhill..." well,
you ain't yet lived life to its fullest. (BTDT!) Kinda like being over VNE and
concluding it would be faster to stop airframe flutter by INcreasing speed
rather than slowing down. Really bad place to be.

Should it happen to you, if you have any sense at all it'll be the sort of
"getting religion" experience that'll stick with you for the rest of your
life! Thanks for sharing, Chip. Yeow!

Bob W.

P.S. Another poster mentioned the good success he obtained by simply
increasing his trailer tire pressures. FWIW, unless you're sufficiently into
higher-performance vehicle handling so's to benefit from
tire-temperature-taking probe technology (and interpretation), another
"sensible rule of thumb" regarding towing glider trailers behind passenger
vehicles is simply to start out by ensuring every tire in contact with the
road is at its recommended (tire, not vehicle) maximum...and *screw* any
misplaced concern about "abbienormal tread wear" or "violating the vehicle's
owner's manual's recommendations." You won't get the former (in the absence of
running "bicycle-width" or "gumball" tires, of course), and no manual writer
can see into a vehicle's future, insofar as what sort of tires with which
it'll eventually be shod. Given today's tires, I'll wager Big Money far more
accidents are contributed to by "too low" tire pressures than "too high." As
always, YMMV...

[[email protected]]

Bob, I can't tell whether you're questioning my sanity or confessing to having a similar experience. :) Obviously you can get yourself in a world of trouble very quickly. But we had 350 miles with a barely controllable trailer to try every possible technique and, once the swings passed a certain point, the only thing that worked was to ease on the accelerator. That meant topping the hills quite slowly, keeping a sharp eye for trucks to avoid being overtaken on the downhills, and not using this technique if a lot of downhill remained ahead (the alternative being trundling down the hill much slower than prevailing traffic, which caused other problems, including being overtaken much more often. I should have been more careful in relating the story.

Plus because the trailer was so unstable, all of the excitement began at slower speeds than usual, giving us a little more time to react.

Yeah, it was exciting at times. Kind of like when I was easing down a hill in the snow many years ago and the rear end of my small, rear-wheel-drive car swung out. I wasn't on the brakes but the deceleration from holding it in a lower gear was enough to trigger the skid. I steered into it but that didn't help a bit, even at full lock. I had to gently feather the throttle to straighten it out, at which point I was moving downhill a LOT faster. Fortunately I was almost at the bottom and was able to steer straight and slow it down safely on level ground.

We should have just stopped and redistributed the load that day. Not to be repeated. I will say that some years later, a crew member driving my trailer home was overtaken by a big rig while going downhill on the freeway. When the trailer started oscillating, she didn't hit the brakes but just got off the throttle. That was enough to exacerbate the swings and she ended up jack knifing and sliding off the road, fortunately with no injury and very minor damage.

I'm not sure this posting is going to sound any less crazy than my first one. But, hey, it works for me, although my Cobra trailer with the right tire pressures is hardly felt behind my full-size van.

Chip Bearden

[[email protected]]

Funny.
I find when my trailers (2 Cobras and a Solaire) starts to oscillate that a quick hard jab on the brakes stops all the bad motions. Doesn't make any difference whether the oscillations are started by an 18 wheeler passing me or by my increasing my speed too much. Acceleration just seems to amplify the swings.

I do find that making sure the trailer is very tongue heavy makes it stable and that tongue light makes it unpredictable.

[danlj]

Technical information for only $26
http://papers.sae.org/2008-01-1228/
Stability and Control Considerations of Vehicle-Trailer Combination.
Hac, A., Fulk, D., and Chen, H., "Stability and Control Considerations of Vehicle-Trailer Combination," SAE Int. J. Passeng. Cars - Mech. Syst. 1(1):925-937, 2009, doi:10.4271/2008-01-1228.

Or http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1645010
The Effect of Longitudinal Center of Gravity Position on the Sway Stability of a Small Cargo Trailer
Michael G. Gilbert, Daniel A. Godrick and Richard H. Klein
Paper No. IMECE2008-66022, pp. 295-305; 11 pages
doi:10.1115/IMECE2008-66022

Or http://www.scientific.net/AMM.29-32.1420
Study on High-Speed Lateral Stability of Car-Trailer Combination

And many more, courtesy of scholar.Google.com (exclude patents at first)

[danlj]

Oh, and at no cost, there's Nelson Funston's classic OSTIV article
http://journals.sfu.ca/ts/index.php/ts/article/view/779/737
The Influence of Design Parameters on Glider Trailer Towing Behavior

[Bob Whelan[_3_]]

On 10/5/2016 8:04 PM, wrote:
> Bob, I can't tell whether you're questioning my sanity or confessing to
> having a similar experience. :) <Snip...>

Heh - sorry, I was "confessing." Like you, my real-world introduction(s) to
"the instability aspect" of glider trailer towing occurred early-on in my
glider-towing "career." Happily, all (but one, exciting, otherwise minor,
self-inflicted foot shot) has always ended well, though once or twice I
could've opened an adrenaline retail store afterward. All my incidents were
considerably shorter in time than your extended education. None ever to be
forgotten...

And that's how I changed "book knowledge" of "proper trailer tongue weight"
into "practical experience..."

> Yeah, it was exciting at times. Kind of like when I was easing down a hill
> in the snow many years ago and the rear end of my small, rear-wheel-drive
> car swung out. I wasn't on the brakes but the deceleration from holding it
> in a lower gear was enough to trigger the skid. <Snip...>

BTDT, too, except I was fortunate enough to have it happen on the level and
without nearby traffic...nor was I "intentionally experimenting" in any way.
Driving to work on a rare (in the west) sleeting morning, I was "alarmedly
aware" how slick it was and how dismal were the handling aspects of the
vehicle I was driving, had had numerous prior warnings almost any throttle
applications at all resulted in wheel spin (and often, an extended slide),
thought it likely I'd have to park the car and walk the last few miles up a
gentle grade to my workplace, and was otherwise fully engaged in
simultaneously developing an "approach plan" while dealing with the
low-traction-issue-of-the-moment. I'd'a turned around and gone home but
couldn't find a place to safely do so until about 3/4 of the way to work.
(Happily, the ice was gone by noon.)

While simply doing nothing but trying to maintain an even throttle pressure in
high gear (minimizing engine braking effects) at the lowest speed that didn't
lug the engine (more wheel spin!), a momentary feather of the throttle
resulted in the rear end lazily easing sideways. Flooring the clutch pedal and
countersteering eventually - slowly, and after several increasing-amplitude
over-corrections - resulted in my doing a low-rotational-speed 180 and sliding
(rolling?) backward in my lane, looking through the windshield at a few other
commuters formerly behind me, with time to check the mirror for oncoming
traffic (none) my state might incite into the dreaded chain reaction, and to
gauge/"somewhat select" the (very shallow) angle at which I'd slide off the
road. The instant the left rear wheel contacted the slightly rougher shoulder
gravel, it "bit" and the vehicle completed a near-180 to its right and parked
itself neatly on the shoulder, facing the proper direction - almost as if I'd
planned it.

The car and I made it all the way to work without further excitement...

Bob W.

[[email protected]]

On Thursday, October 6, 2016 at 8:46:14 AM UTC-4, wrote:
> Funny.
> I find when my trailers (2 Cobras and a Solaire) starts to oscillate that a quick hard jab on the brakes stops all the bad motions. Doesn't make any difference whether the oscillations are started by an 18 wheeler passing me or by my increasing my speed too much. Acceleration just seems to amplify the swings.
>
> I do find that making sure the trailer is very tongue heavy makes it stable and that tongue light makes it unpredictable.

How do you go about making the tongue light as you describe?
UH

[son_of_flubber]

Ironic that there is zilch about loading-towing a glider trailer on the PPL-Glider written test, but there're a bunch of questions about VOR.

[Tony[_5_]]

I always thought that part of the practical test should be being presented with a mystery trailer light problem to solve, with a time limit.

Ok not realistic for the FAA test but could be a good addition to the Bronze Badge test :)

[Dave Martin[_3_]]

Don.
You need to update your driving knowledge - the UK speed limits for towing
a trailer is 60mph

https://www.gov.uk/speed-limits

At 17:13 05 October 2016, Don Johnstone wrote:
>At 14:59 05 October 2016, Charlie M. UH & 002 owner/pilot wrote:
>>I've wondered if adding a small (1/4" - 3/8") anti sway bar to th
>trailer
>>axle would help in most situations. Granted, proper weight is best, bu
>the
>>anti sway bar may widen the margin.
>>Thoughts?
>
>Weighting is important, no doubt. Reducing the weight and therefore th
>inertia on the anchored end of the trailer does reduce the possibility o
>any swing increasing by increasing the ability of the towing vehicle t
>damp the oscillations. The trigger for these oscillations is aerodynami
>caused by the low pressure area between two vehicles as they overtake/ar
>overtaken. The situation is made worse if the vertical surface is the sam
>or more than the area in front of the axle. Cobras and Komets are designe
>to reduce the side area behind the axle.
>I towed a trailer, containing a Grob 103 back from Holland. The nose
weigh
>was close to the maximum limit allowed for my car, theoretically the bes
>situation to improve stability, however it swayed readily. I have jus
>towed the same combination over 300miles. Before leaving I increased th
>tyre pressures on the trailer from 35psi to 55psi (Max 65psi). The traile
>now tows with no swaying up to the maximum speed limit in the UK (70mph)
>It does allow towing at just below 60mph which means I can avoid bein
>overtaken by large trucks, the condition which is most likely to trigge
>swaying. Tyre pressure appears to have a large influence on the stabilit
>of the trailer, greater than loading. Vertical instability is now the
majo
>problem, easily fixed by a stabiliser.
>
>

[Charlie M. (UH & 002 owner/pilot)]

Still waiting for feedback from "ME" types on this.

Tire pressures have a bit on this.

Had a large reply earlier (got lost for whatever reason) that is not here. Most recent glad to not read through it.

Basically, high trailer tire pressures may limit swaying, it also intrudes shock loads to mechanical instruments.

"Fix one thing, FUBAR another thing.....".

[Don Johnstone[_4_]]

At 13:57 07 October 2016, Dave Martin wrote:
>Don.
>You need to update your driving knowledge - the UK speed limits
for towin
>a trailer is 60mph
>
>https://www.gov.uk/speed-limits

I know that, as I should. My point was that adding 20psi to the tyre
pressure changed the handling of the trailer from unstable at
50mph to steady at 20mph faster. I suspect that a faster speed
would be possible but it was unnecessary to test as a 10mph
excess over the limit of 60mph was enough to show that just
increasing the tyre pressure was a partial answer to the problem we
had, and give a reasonable margin.
Being able to tow at 60mph means that I was able to avoid being
overtaken by large Artics governed to 56mph, avoiding the main
condition that triggers swaying, being restricted to 50mph did not
allow that.
Police generally ignore excess speed less than 10mph on
motorway/dual carriageways in the UK anyway, which is why most
traffic on those roads is doing 80mph.

>At 17:13 05 October 2016, Don Johnstone wrote:
>>At 14:59 05 October 2016, Charlie M. UH & 002 owner/pilot
wrote:
>>>I've wondered if adding a small (1/4" - 3/8") anti sway bar to
th
>>trailer
>>>axle would help in most situations. Granted, proper weight is
best, bu
>>the
>>>anti sway bar may widen the margin.
>>>Thoughts?
>>
>>Weighting is important, no doubt. Reducing the weight and
therefore th
>>inertia on the anchored end of the trailer does reduce the
possibility o
>>any swing increasing by increasing the ability of the towing
vehicle t
>>damp the oscillations. The trigger for these oscillations is
aerodynami
>>caused by the low pressure area between two vehicles as they
overtake/ar
>>overtaken. The situation is made worse if the vertical surface is
the sam
>>or more than the area in front of the axle. Cobras and Komets
are designe
>>to reduce the side area behind the axle.
>>I towed a trailer, containing a Grob 103 back from Holland. The
nos
>weigh
>>was close to the maximum limit allowed for my car, theoretically
the bes
>>situation to improve stability, however it swayed readily. I have
jus
>>towed the same combination over 300miles. Before leaving I
increased th
>>tyre pressures on the trailer from 35psi to 55psi (Max 65psi).
The traile
>>now tows with no swaying up to the maximum speed limit in the
UK (70mph)
>>It does allow towing at just below 60mph which means I can
avoid bein
>>overtaken by large trucks, the condition which is most likely to
trigge
>>swaying. Tyre pressure appears to have a large influence on the
stabilit
>>of the trailer, greater than loading. Vertical instability is now th
>majo
>>problem, easily fixed by a stabiliser.
>>
>>
>
>

[Eric Greenwell[_4_]]

Charlie M. (UH & 002 owner/pilot) wrote on 10/5/2016 7:59 AM:
> I've wondered if adding a small (1/4" - 3/8") anti sway bar to the
> trailer axle would help in most situations. Granted, proper weight is
> best, but the anti sway bar may widen the margin. Thoughts?

It's unlikely it will change the dynamics of a single axle trailer.
Ante-sway bars are used on cars and similar to change the roll stiffness
about each axle: generally, an anti-sway bar on the front axle increases
"understeer" and makes the vehicle more stable. A rear bar does the
opposite.

The place to change anti-sway bars is on the tow vehicle. I suspect a
bigger front bar would increase the towing stability, but I think it's
better to get the trailer balance and tire pressures right (ditto for
the tow vehicles tire pressures).

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[2G]

On Monday, October 10, 2016 at 9:53:59 PM UTC-7, Eric Greenwell wrote:
> Charlie M. (UH & 002 owner/pilot) wrote on 10/5/2016 7:59 AM:
> > I've wondered if adding a small (1/4" - 3/8") anti sway bar to the
> > trailer axle would help in most situations. Granted, proper weight is
> > best, but the anti sway bar may widen the margin. Thoughts?
>
> It's unlikely it will change the dynamics of a single axle trailer.
> Ante-sway bars are used on cars and similar to change the roll stiffness
> about each axle: generally, an anti-sway bar on the front axle increases
> "understeer" and makes the vehicle more stable. A rear bar does the
> opposite.
>
> The place to change anti-sway bars is on the tow vehicle. I suspect a
> bigger front bar would increase the towing stability, but I think it's
> better to get the trailer balance and tire pressures right (ditto for
> the tow vehicles tire pressures).
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
> email me)
> - "A Guide to Self-Launching Sailplane Operation"
>
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> - "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm
>
> http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

The most stable trailer configuration is a semi where about half the trailer weight is on the tongue. This is not possible for autos which can't support that kind of tongue weight. Even fifth wheels don't put the trailer wheels in that position, and they are accepted to be the most stable trailer configuration.

I have come to realize that there are two moment of inertia of interest; one referenced to the trailer axle and the other referenced to the hitch. Why is MOI important? The answer is if you have an oscillating body it will be harder to stop the larger the MOI. This is why engines have flywheels. If you want to minimize axle MOI you would put as much weight as possible near the axle, which may decrease tongue weight. If you want to minimize hitch MOI you move weight forward, which increases axle MOI. Clearly there is something contradictory about these two MOIs. All trailer towing guides I have seen emphasize maintaining a tongue weight that is 7 to 10% of the total trailer weight. Remember that MOI is calculated as the sum of the weight times the radius SQUARED, so any weight is a long distance from the reference point has a major influence on MOI. If the trailer's tires are maintaining traction with the road the axle MOI is of interest, but if the tires loose traction then the hitch MOI dominates. For certain, putting weight at the rear of the trailer aggravates both MOIs, but increases the hitch MOI four times as much as the axle MOI.

The moral of the story is to manage the hitch weight properly. Merely adding weight to the front of the trailer is not the solution: you should adjust the axle position to get the proper tongue weight. I have done this on one trailer and experimented with trailer transient response as a function of tongue weight. More tongue weight was better.

Tom

[Jonathan St. Cloud]

Not adding anything to the conversation, but I had purchased a Nimbus 4 that had a Pfister (spelling?) tube trailer. The tongue weight was so heavy it could only be moved by a jack. Soon after getting the bird I purchased a double axle Cobra trailer for the glider and sold the other trailer. The new cobra had a tongue weight much less than the former trailer and could be moved by hand and towed marvelously. Of course back then I was towing with a 2500 chevy Suburban and I had to put a post it on the dash to remind me that I was towing a trailer. While not an expert in any field of this particular discussion, it seems tow vehicle has much to do with the stability as the trailer. My ASw-24 towed towed great behind my little four banger Toyota pick up and horrible behind my next car a Jeep Grand Cherokee. The Suburban was my favorite tow vehicle but I had to keep reminding myself of the trailer. I am currently towing an ASG-29E with a ML 350 diesel and it tows great, but I do have a double exile trailer.

[2G]

On Friday, October 14, 2016 at 7:24:24 AM UTC-7, Jonathan St. Cloud wrote:
> Not adding anything to the conversation, but I had purchased a Nimbus 4 that had a Pfister (spelling?) tube trailer. The tongue weight was so heavy it could only be moved by a jack. Soon after getting the bird I purchased a double axle Cobra trailer for the glider and sold the other trailer. The new cobra had a tongue weight much less than the former trailer and could be moved by hand and towed marvelously. Of course back then I was towing with a 2500 chevy Suburban and I had to put a post it on the dash to remind me that I was towing a trailer. While not an expert in any field of this particular discussion, it seems tow vehicle has much to do with the stability as the trailer. My ASw-24 towed towed great behind my little four banger Toyota pick up and horrible behind my next car a Jeep Grand Cherokee. The Suburban was my favorite tow vehicle but I had to keep reminding myself of the trailer. I am currently towing an ASG-29E with a ML 350 diesel and it tows great, but I do have a double exile trailer.

The Jeep Grand Cherokee has a bad reputation as a tow vehicle. I personally saw one (attempting to) towing a small travel trailer. It was not stable and I witnessed severe swaying at a relatively slow speed (50 mph). The driver would slow down when it went unstable, and then creep back up to the speed that it would go unstable again. It was disturbing to watch - the driver had his family in the car and they were all at risk. I think the problem was the short wheel base in combination with the suspension and the tires. If they are too soft there isn't sufficient damping to stop swaying. This is further aggravated by the length of glider trailers. Yet they are rated to tow pretty hefty trailers. The moral of the story is just because the drive train can handle the trailer weight doesn't mean that it will be stable at highway speeds.

Tom

[JS]

On Saturday, October 15, 2016 at 11:05:40 PM UTC-7, 2G wrote:
> On Friday, October 14, 2016 at 7:24:24 AM UTC-7, Jonathan St. Cloud wrote:
> > Not adding anything to the conversation, but I had purchased a Nimbus 4 that had a Pfister (spelling?) tube trailer. The tongue weight was so heavy it could only be moved by a jack. Soon after getting the bird I purchased a double axle Cobra trailer for the glider and sold the other trailer. The new cobra had a tongue weight much less than the former trailer and could be moved by hand and towed marvelously. Of course back then I was towing with a 2500 chevy Suburban and I had to put a post it on the dash to remind me that I was towing a trailer. While not an expert in any field of this particular discussion, it seems tow vehicle has much to do with the stability as the trailer. My ASw-24 towed towed great behind my little four banger Toyota pick up and horrible behind my next car a Jeep Grand Cherokee. The Suburban was my favorite tow vehicle but I had to keep reminding myself of the trailer. I am currently towing an ASG-29E with a ML 350 diesel and it tows great, but I do have a double exile trailer.
>
> The Jeep Grand Cherokee has a bad reputation as a tow vehicle. I personally saw one (attempting to) towing a small travel trailer. It was not stable and I witnessed severe swaying at a relatively slow speed (50 mph). The driver would slow down when it went unstable, and then creep back up to the speed that it would go unstable again. It was disturbing to watch - the driver had his family in the car and they were all at risk. I think the problem was the short wheel base in combination with the suspension and the tires. If they are too soft there isn't sufficient damping to stop swaying. This is further aggravated by the length of glider trailers. Yet they are rated to tow pretty hefty trailers. The moral of the story is just because the drive train can handle the trailer weight doesn't mean that it will be stable at highway speeds.
>
> Tom

The older Jeep Cherokee was the same, especially when low on fuel. Install better shocks and it's fine.
Jim

[Charlie M. (UH & 002 owner/pilot)]

Higher mileage Jeeps are also know for the "Jeep death shake/weave" on their own, even without a trailer. Not a good choice unless worn suspension bits are replaced.
Yes, we owned a 1998 Cherokee Sport for a couple years, lots of bottom bits were replaced.
High CG, tall tires, worn bits, shortish wheel base for its height.

A good tow vehicle should be sorta heavy, long, low (think 60's & 70's US station wagons). Yes, other vehicles can tow (I crewed, about 1979, driving a VW Beetle towing a plywood ASW-15 trailer, it had a hard time doing 55MPH on flat ground.....empty!), but some vehicles have an easier time with ANY trailer.

[JS]

Is there much point in comparing worn out cars? In my case the boxy '87 Cherokee was bought new, and its first road trip was a 4-day drive to pick up an LS4.
Took a lot of messing around with the trailer and car to find the real fix.
Jim

[Giaco]

On Wednesday, October 5, 2016 at 5:20:36 PM UTC-4, wrote:
> On Wednesday, October 5, 2016 at 4:50:51 PM UTC-4, wrote:
> > In the early 1970s, my father and I loaded our damaged 201 Libelle into a tall, straight-topped, corrugated-aluminum-and-steel-tube trailer meant for a 16.5M Diamant. Almost unbelievably given the weight of the Diamant wing, it was set up to load wingtips first from the rear. So that's how we loaded the Libelle wings: i.e., spars aft. The fuselage we just rolled into the trailer and tied it down as best we could using the tail tiedown bracket that was in place.
> >
> > As you can imagine with our short-span bird sitting well aft of where the Diamant would be, the trailer was somewhat tail heavy. Off we went in the family Chevy station wagon (read: heavy, full-size American car from that era) from Cincinnati to the Gehrleins' repair facility in Erie, PA, a 350 mile journey that should have taken about 5 hours.
> >
> > I have long since suppressed most memories of that terrifying trip but not the lessons of that masters-level, crash course (no pun intended, fortunately) in trailer control. Everything I know about keeping uncooperative trailers in line I learned that day. I almost had to pry my fingers off the steering wheel when we arrived.
> >
> > I learned how to slow going uphill so I could avoid slowing (not good) or braking (really bad!), and even accelerate slightly if needed on the way down the hill. How to accelerate slightly when being passed by a large truck. Or anything larger than a motorcycle, for that matter. How to watch in the mirror to make certain there were no large trucks overtaking as we reached the top of a hill.
> >
> > How never to touch the brakes going around a curve. How to hit the throttle to straighten out an incipient tail wag, including when going downhill being passed by a large truck (see "how to slow going uphill", above).
> >
> > I don't know why we didn't just stop and move things forward, or pile a bunch of stuff in the front of the trailer to get some tongue load. I guess we didn't know any better. Or assumed it was some fundamental flaw in trailer stability. The empty trailer towed fine on the way home, unsurprisingly. If I recall correctly, the subsequent owner of that glider moved the axle back to get some more weight on the tongue even with the heavier, longer-span Diamant in the box, and it towed fine.
> >
> > To this day, almost 45 years later, I'm still wary of the little twitch in the steering wheel that signals the trailer is moving around and could get squirrelly.
> >
> > Chip Bearden
>
> My PIK trailer was a bit wiggly when pulling with my little Triumph TR7. It did get rolled when we got run off the road by a truck and ended up with an uncontrollable divergent oscillation.
> The glider did not get hurt and flew in my first Nationals 2 days later(another story).
> When repairing the trailer I replaced the front frame members with one size larger tubing and extended the tongue area about 8 inches. It was like a different trailer and never wiggled again. Tongue weight was almost exactly the same so my theory was that the longer arm from the tow ball to the oscillation dampers(wheels) was enough to entirely change the dynamics.
> FWIW
> UH

Just Catching up now... As the previous owner (first car) of a Triumph Spitfire and the current owner of a Pik, i really hope you have a photo of that setup, and if so, would love to see it!
G7

[kirk.stant]

On Sunday, October 16, 2016 at 9:33:32 AM UTC-5, Charlie M. (UH & 002 owner/pilot) wrote:
> Higher mileage Jeeps are also know for the "Jeep death shake/weave" on their own, even without a trailer. Not a good choice unless worn suspension bits are replaced.
> Yes, we owned a 1998 Cherokee Sport for a couple years, lots of bottom bits were replaced.
> High CG, tall tires, worn bits, shortish wheel base for its height.

You can tow with a Jeep Cherokee, but you have to have everything setup correctly: upmarket tires at max PSI, air shocks on rear axle, proper tongue weight, trailer tires at correct pressure and type. With that, my old 1997 Cherokee Sport with 230K miles tows fine up to 70 mph (15m Cobra with trailer tires). But it took a while to sort it out! (and the brakes are marginal going down long hills...)

But a longbed pickup - or an RV? Can't even tell there is a trailer behind....

Now when you have to pull that trailer out of the middle of a huge disced field in the middle of nowhere at 2 AM - that 4WD Cherokee is nice to have around, warts and all. Which is why it's still in my garage.

Horses for courses, is the saying I believe.

Kirk
66