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Why Fill Gear Leg Fairings with Foam?
- Thread starter donmtt
- Start date
Ah! So that was an attempt to deal with wheel shake on landing? Interesting. It will be interesting to see if the shimmy in my RV-7 (which is sometimes pretty bad and other times non-existent) is any different now that I've cleaned out the foam....
Welcome to -7 world; Please download a set of the plans and instruction manual asap. They'll really help you in the long run.
Just one of many ways to skin that feline.
Gear leg "shimmy" is solved by attaching another mass to the gear leg -- much like a tuning fork that you want to dampen its response. Van's describes this in DWG C3, Zones F-G x 5-6.
Internal fixation for the gear leg fairings -- a little "Great stuff" or 2-part pour foam at the top and the bottom 1.5 - 2" and things stay put...sort of.
Just one of many ways to skin that feline.
Gear leg "shimmy" is solved by attaching another mass to the gear leg -- much like a tuning fork that you want to dampen its response. Van's describes this in DWG C3, Zones F-G x 5-6.
That always solves it for me, but with tires + tubes coming in at $600+, it would be nice to find a solution that didn't leave a fair amount of tread on the throw-away's...
As time went on there were other approaches. Bonding wood to the gearleg, and then mounting the fiberglass fairing over it (but not bonding the fairing to the leg). Certainly is easier to get the leg fairing aligned with the airstream that way. A misaligned gearleg fairing can appear as a "heavy wing".
Be careful with foam if you choose that path. Several reporting's (I've seen the pictures), where the foam trapping moisture leads to severe gear leg corrosion. Only if the legs are properly prepared and primed/painted prior to foaming. I bonded wood stiffeners with proseal and fiberglass tape wrapped mine on my RV-4. One piece fiberglass fairings, no shimmy ever. Tires balance as others mentioned is important.
The foam was in the gear leg fairing, not the wheel pant.
And I wouldn't do it. It was an old and now discarded idea.
Drowosek
Member
I see what you mean. It all comes down to the near-total absence of hysteresis in metals, especially in hardened steel. For this reason, we used only fiberglass landing gear springs on our aircraft. The micro-movements of the plastic layers significantly dampen the energy of the vibrations, converting it into heat.
