Dear Rolf
You are up against the basic fact that the weight distribution with such two
seater trailers can be really terrible with regard to forcing excessive rear
overhang. Yes the configuration with fuselage and wing roots to the front
produces the best ease of rigging, but with a serious compromise in towing
stability in that the axle(s) are further forward than desirable. There is
nothing better that you can do than get the axle(s) well back, but too far
and then of course the tongue weight goes up unacceptably. You may still be
able to get some weight out of the front of the trailer and redistribute it
to the rear. The more you can do this the more you can move the axle(s)
back maintaining a constant drawbar weight. Just because a spare wheel
seems not important at 15 to 18 kg, it is actually useful if you can
relocate it from the front end to the rear end somehow, or at least to the
side and rear of the trailer wheel mudguard. Can you fit a stowage tray/box,
sideways pullout on rails, behind the axle and underfloor? This may get
some of the miscellaneous stuff out of the front of the trailer and help get
weight to the rear such that you can then relocate the axle(s) aftwards.

You do not say whether your trailer is single axle or dual axle. If single
axle then you can fit dual axles which, even if the centre position of the
axle set is the same as for single axle, will get some rubber contact with
the road at further back distance than before. I know of so much hassle
with two seaters towed on a single axle, I would never go down that path.
Always double axle for me. Yes the trailer quote to me for such a Cobra
German trailer three years included the suggestion that the dual axle axle
requirement I included was unnecessary. Rubbish I say.

Getting the axles back also helps reduce side area aft of the wheels. To
understand this issue better, go to the rear of your trailer when attached
to your car. Push sideways against the rear end and feel how soft it is in
comparison to when you go to the front end and do the same. Pushing at the
rear causes sway, whereas when you push sideways against the front you feel
the lateral resistance of all the tyres, car plus trailer. So the bow wave
from the passing truck or cross wind through the trees can cause large
trailer sway angles because of the low resistance at the rear to side force.
Side area and rear overhang are tails that wag the dog.

I have had good results with a Hayman Reese sway stabiliser. I have looked
at the ALKO product as on the face of it potentially better. Someone has
commented on this list on the sway stabiliser from Alko and noted the need
to anchor the tow ball. I seem to recollect that on the ALKO website here
in Australia I recently saw this device (which I have seen also in the real
world) AND also shown was the additional ALKO part required to hold the ball
to the tow tongue and prevent the ball being turned by the sway stabiliser.

Fit tyres with stiffer sidewalls.

See also article by Funston in Technical Soaring July 1989, p90-95. If you
want it and can't get it closer to home send me a direct email with a real
world address.

Cheers
Roger Druce
Australia

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