Wheel Pant Damage

[Skippydiesel]

Hi All,
My Sonex has only 130 hrs total air time.
In the above time my wheel pants have developed a vertical crack on the outside (single mounting point).
I have repaired the cracks but am at a loss as how to prevent a recurrence.
When I first saw a small crack starting, I replaced all my Philips head securing screws, with button head Allen keys for higher tightening torque AND used stainless steel extra large "fender" washers under each to improve security.
From non scientific observation, it seems the likly cause is the horizontal "whipping" motion of the undercarriage, during ground opps, .
Anyone have a solution that includes keeping the wheel pants on the aircraft????

[WaiexN143NM]

Hi all, skippy,

It sounds like to me you need to put some stiffners on your gear legs. We got the wood stiffners
from flyboy accessories, and wrapped with a few layers of fiberglass. The rv guys do this too.
Some sonex people posted they just used some band clamps and a sq. strip of oak wood.This should stop the shimmy of the gear leg while taxi.
Let us know of your solution that works. Ive seen videos of rv’s and sonex’s taxi, and you would be suprised
at the leg shimmy. Other things we did, pump tires to 50 psi. also added glass dynabeads into tires to help balance them.

best,


michael.

[Skippydiesel]

Hi all, skippy,
It sounds like to me you need to put some stiffners on your gear legs. We got the wood stiffners
from flyboy accessories, and wrapped with a few layers of fiberglass. The rv guys do this too.
Some sonex people posted they just used some band clamps and a sq. strip of oak wood.This should stop the shimmy of the gear leg while taxi.
Let us know of your solution that works. Ive seen videos of rv’s and sonex’s taxi, and you would be suprised
at the leg shimmy. Other things we did, pump tires to 50 psi. also added glass dynabeads into tires to help balance them.
best,
michael.

Thanks for the reply Michael.
I am reassured that the problem is not unique to my aircraft but a bit perplexed as to how the wood "stiffeners" work.
I can see how the stiffener would remove/reduce the "springiness" of the leg but would this not also impact negatively on the shock absorbtion of the landing gear?
If possible - please post photos/plans of this modification.
Thanks

[Skippydiesel]

After your post I did some internet searches - there is a lot of information on using wood stiffeners on RV's.
Interestingly the wood used varies from Oak, Poplar, to engine crate reused (probably pine) and laminated - so I guess almost any wood will be suitable.
Some of the users report good results to 500 hrs - One with the laminated & jointed wood, had only a few hours before the stiffeners cracked at about the halfway mark.
The latter stiffener, interests me as it demonstrates that the legs are bending over the whole length ie between wheel axle & engine frame.
If a relativly stiff stiffener is used, I would speculate that the loads (particularly landing) are then concentrated at the axle & engine frame mounting point - could this lead to fatigue/failure of the undercarriage leg??

[Skippydiesel]

Further;
Have been doing some research into flexible timber, that would follow, rather than hinder, the flex of the undercarriage.

Some Australian contenders;

Laminated bamboo.
Spotted Gum (Corymbia maculata)
Mulga (acacia aneura)
Jitta (Halfordia scleroxyla)

[Skippydiesel]

Got another idea:

What of composite batten, rods, or tube.

Come in a wide range of dimensions & shapes.
The battens are used extensively in sailing. These can be chosen with reference to a flex chart.
Rods/pipes may be hard to secure, although a bundle of 3 would likly be easier than one, to keep in position.
A series of "saddles" could be made to secure to the length of the undercarriage leg?

[Skippydiesel]

I am surprised at the lack of interest in, what seemed to be, a not uncommon problem.

Do most Sonex owners just leave the wheel pant/fairings off??