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Gear leg fairing questions.

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00Dan

Well Known Member
I’m retrofitting the fiberglass leg fairings on my -4 and have some questions about the plans. Section 10 along with drawing C3 for those following at home; I believe this part is the same for all the round rod gear RVs.

First question I have is regarding the “no twist” condition that is checked with a square. Using the one end and clamping as the plans describe results in a slightly misaligned trailing edge in a couple places and eye-balling the fairing makes it seem ever so slightly off. Is there a trick to this or is the square at one end only an approximation?

Second, the trim template has trim lines for both ends and the trailing edge, however the initial trim instructions say not to trim the trailing edge. Problem is, I’ve read the entire section and I’m not seeing where the trailing edge is ever trimmed. Is the trim marking used for the piano hinge alignment but not actually cut?

Third, the plans were written back when the fiberglass parts were transparent. They describe marking the piano hinge and then match drilling. Now that the parts are shipped with the opaque gel coat, is there a best practice on achieving this? Would drilling the hinge on the bench then using the magnets to hole locate be the best path forward?
 
Laser level?

00Dan said:
I’m retrofitting the fiberglass leg fairings on my -4 and have some questions about the plans. Section 10 along with drawing C3 for those following at home; I believe this part is the same for all the round rod gear RVs.

First question I have is regarding the “no twist” condition that is checked with a square. Using the one end and clamping as the plans describe results in a slightly misaligned trailing edge in a couple places and eye-balling the fairing makes it seem ever so slightly off. Is there a trick to this or is the square at one end only an approximation?

Second, the trim template has trim lines for both ends and the trailing edge, however the initial trim instructions say not to trim the trailing edge. Problem is, I’ve read the entire section and I’m not seeing where the trailing edge is ever trimmed. Is the trim marking used for the piano hinge alignment but not actually cut?

Third, the plans were written back when the fiberglass parts were transparent. They describe marking the piano hinge and then match drilling. Now that the parts are shipped with the opaque gel coat, is there a best practice on achieving this? Would drilling the hinge on the bench then using the magnets to hole locate be the best path forward?
Click to expand...

I hung mine on the bench with a couple of threads and set up a laser level using the vertical to ensure it hit the TE and the LE in the center. It worked for both at the same time in the right position from the large end. Surely someone has a better way!?!?
 
I got some answers from the Mothership on items two and three today, for anyone reading this thread in the future.

The hinge is riveted in place and then the trailing edge is trimmed. The plans for the newer RV models are much clearer in this regard. As for match drilling the fairing, sanding the gel coat off was recommended as the easiest way forward.


Now another question I have having worked on these fairings more. I overdid a countersink on one position and now the -3 rivet is set but the head does not fill the countersink. With this thin fiberglass, I’m brainstorming two possible options.
The first is to upsize that one hole to -4. The second, considering the non-structural nature of the part, and the fact that the rivets aren’t even set fully per the plans, is to leave the rivet in place and use flox to fill the oversized countersink around the manufactured head. Any thoughts on this?
 
Fill with resin, let dry, re-countersink.
Or just set the rivet.

Note that the manual calls for a rivet squeezer and to not fully set the rivet to avoid cracking the fiberglass.

Oh, and if you anyway have the resin handy, nothing to prevent you from roughing up the hinge and inside of the fairing and putting resin between hinge and fiberglass. Not unlike installing hinges on the cowling.

Finn
 
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FinnFlyer said:
Fill with resin, let dry, re-countersink.
Or just set the rivet.

Note that the manual calls for a rivet squeezer and to not fully set the rivet to avoid cracking the fiberglass.

Oh, and if you anyway have the resin handy, nothing to prevent you from roughing up the hinge and inside of the fairing and putting resin between hinge and fiberglass. Not unlike installing hinges on the cowling.

Finn
Click to expand...

I don’t have a picture right now but the hole in question already has a partially set rivet in it, per the plans. To clarify, I’m wondering if just using resin or flox to fill the rest of the countersink around the existing rivet is viable compared to drilling out the rivet, putting down resin, and re-drilling/countersinking.
 
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