trailer sway

Howdy -

I know this topic has come up before, but we're searching for the
latest theories:
We're towing a DG-500M in a Cobra trailer, and it has a definite sway,
fortunately it usually damps fairly well. Life was worse with a strong
crosswind. We had 2 thoughts:
1. tonuge weight - are we shooting for tongue weight about 10% of the
total trailer weight?
2. Hitch height - any thoughts?

Thanks!
Rolf

try the following -
1 - 5 gallon can of water in the front of the trailer - if that doesn't
work try 2
max pressure in the trailer tires - read the label and do max pressure
for that tire
max pressure in the rear tires of the tow vehicle
normal pressure in the front tires of the tow vehicle
Good luck - this should solve your problem

wrote:
Howdy -

I know this topic has come up before, but we're searching for the
latest theories:
We're towing a DG-500M in a Cobra trailer, and it has a definite sway,
fortunately it usually damps fairly well. Life was worse with a strong
crosswind. We had 2 thoughts:
1. tonuge weight - are we shooting for tongue weight about 10% of the
total trailer weight?
2. Hitch height - any thoughts?

Thanks!
Rolf

Rolf,
Try a longer wheelbase vehicle to tow with such as a Suburban or a full
size extended cab p/u. Cobra trailers are balanced really well, hitch
height-trailer should look fairly level, nose high or low shouldn't
have much effect on sway. My Cobra single axle weighs 2000 lbs with
glider in it, my tongue weighs less than 100 lbs, tracks great swings
little but I pull it with a fullsize p/u.

The 5 gal water can in the front of the trailer worked well for me, but
the better long-term solution was a new set of *trailer* tires for my
Cobra trailer.

2NO

wrote in message
oups.com...
Howdy -

I know this topic has come up before, but we're searching for the
latest theories:
We're towing a DG-500M in a Cobra trailer, and it has a definite sway,
fortunately it usually damps fairly well. Life was worse with a strong
crosswind. We had 2 thoughts:
1. tonuge weight - are we shooting for tongue weight about 10% of the
total trailer weight?
2. Hitch height - any thoughts?

Thanks!
Rolf


My experience is that more tongue weight is better - up to the limits of
your hitch, of course. The usual recommendation is 10%, but if your hitch
will take more...

Think of it as a taildragger vs nosedragger - if the trailer balances on the
wheels, it's more like a taildragger (which balances just behind the mains),
with the weight well forward, it 's more like having trycicle gear - stable
on the ground, let your feet go to sleep.

I had a boat on a homade trailer that was just about balanced (near zero
tongue weight)- I was never sure that it wasn't going to pass me as we went
down the road. I never took it over 45mph or so it was so bad. After I moved
the boat forward to give me a couple hunded pounds on the tongue and it
settled right down. 70? No problem. Like it wasn't there.

Geoff.

Rolf,

With a glider trailer there are two centers you need to worry about,
the CG is your weight distribution. In general the minimum weight on
the tongue should be 10%, more is better. The second is the
aerodynamic center of gravity as related to your wheels. If the
aerodynamic center of gravity is behind the wheels your trailer will
tend to be unstable as well. Think about this as surface area in front
and behind the wheels. You want more area in front than behind if
possible. Rather than just adding weight to the tongue by adding
ballast it is better to move the wheels back. This will lengthen the
amount of trailer in front of the wheels and have less behind, i.e.
shifting the aerodynamic center forward as well. Most modern glider
trailers have the wheels on a sliding frame that allows you to move the
wheels back, if not it may be worth it in the long run to have someone
move them back for you.

Tim

wrote:
Howdy -

I know this topic has come up before, but we're searching for the
latest theories:
We're towing a DG-500M in a Cobra trailer, and it has a definite sway,
fortunately it usually damps fairly well. Life was worse with a strong
crosswind. We had 2 thoughts:
1. tonuge weight - are we shooting for tongue weight about 10% of the
total trailer weight?
2. Hitch height - any thoughts?

Thanks!
Rolf

If your tow vehicle uses leaf springs to suspent the rear axel, then a
sway bar will likely stop the problem. Next time you tow, see if you
can feel the tow vehicle moving side to side on it's leaf springs as
you sway. The mass of a big trailer will "rubber band" your leaf
springs side to side, with nothing to damp that motion. Like taking the
shocks off your car and riding on the springs, except sideways.

-Dan

I agree with Tim. I have been thru the whole rigamarole of tire
pressure, weight in the front of the trailer, all the suggestions short
of welding the insert into the reciever. The only thing that worked
for me was moving the axle aft. Stand back from the trailer and
eyeball where the axle is-most are around 50%. Then eyeball other
trailers and you'll see the axle is farther aft. I could not get my
trailer to tow behind a 3/4 ton, extra cab, long bed turbo diesel Dodge
pickup. If there is a better tow vehicle for pulling trailers, I've
yet to see it. Ford and Chevy are just as good. Travel trailer, boat
trailers, utitlity trailers and motorcycle trailers do not have the
problems that the sailplane people have. If a trailer is designed
properly, you can pull it at 70mph behind a golf cart.....
Bill

wrote in message
oups.com...
.. If a trailer is designed
properly, you can pull it at 70mph behind a golf cart.....
Bill

Where can you get these golf carts - might speed up the occassional round!
8-)

Keith

On Mon, 13 Jun 2005 08:15:23 -0700, rolfh wrote:

We're towing a DG-500M in a Cobra trailer, and it has a definite sway,
fortunately it usually damps fairly well. Life was worse with a strong
crosswind. We had 2 thoughts:
1. tonuge weight - are we shooting for tongue weight about 10% of the
total trailer weight?
2. Hitch height - any thoughts?

I used to own a half share in a Nimbus 2. My partner and I had both
previously rolled a glider trailer, writing off the car, in separate
incidents with different trailers. So when we discovered the home built
Nimbus trailer could not be towed over 80km/hr we were determined to fix
it.

Our solution was:

1) We moved the trailer axle back to increase the tow ball weight. We
aimed for 50kg but ended up with close to 60kg. Up from about 20kg. 50kg
is near the limit of most cars, above this and you will need to tow with a
truck.

2) We bought a "Trapezium" towbar stablizer. This is a device which
bolts onto the towbar. It has a mechanism which moves the tow ball from
side to side as the trailer rotates around the tow ball. The effect
of this is to move the pivot point well forward of the tow ball, close to
the rear axle of the tow vehicle. This changes the geometry of the system
and radically reduces the tendency to sway. Google found a writeup on this
device on the bottom of this page.

http://www.swift-owners-club.co.uk/s...abilisers.html

It is a South African invention, originally developed by a glider pilot.
It is VERY effective with a glider trailer due to the length of the
trailer. I don't know whether they are still available, but if you find
one, be sure to know they work.

These two in combination resulted in a trailer which was stable at speeds
over 120 km/hr. I was never brave enough to try towing any faster.

Double axle trailers are also much more stable. If the mod is done
carefully, adding a second axle to a trailer can often provide a permanent
fix.

Of course you must have an appropriate tow car. Beware, modern cars are
lighter, but old glider trailers remain the same.

Many pilots only discover that the car they own is not suitable for towing
the glider that they fly after they have successfully completed their
first outlanding. Worst still, the discovery is often made with an
inexperienced friend driving the car ...

Have fun.

Ian