Friday, January 25, 2013

Preventing RV intersection fairing calamity

A few days ago, I posted this picture:

The lower intersection fairing -- the back half -- on the right side had ripped away from the wheel pant fairing. It was a fairly violent destruction because further inspection revealed it didn't rip off along the bonded portion -- that is: a delamination -- it ripped clean across the fairing (these are the fairings sold by Cleaveland Tools).

What caused it? My RV friend, Ted Chang, figured it out and it makes perfect sense. The rear half sits up slightly from front half (it's pushed out a little by the shape of the gear leg fairing) and the 170 mph breeze caught it and ripped it. That makes perfect sense, though I'm surprised it didn't happen on the left side first because that side was set up worse than the right side.

See, the problem is you can't secure the fairing to the gear leg fairing. I'd actually put a nutplate in the gear leg fairing to screw the intersection fairing down to keep this from happening. But then I realized that the gear leg fairing needs to move inside the intersection fairing because the gear leg fairing is clamped at the top of the gear leg and with the flex of the leg on takeoffs and landings, attaching it at the bottom puts pressure on the top. So the clamp would either break the fairing or -- more likely -- it would pull down and chafe against the gear leg. The gear leg fairing has to be allowed to move.

What to do? Ted provided the perfect solution with this drawing he sent me on Facebook.

His "slot" will hold the front and back together.

So I've attached the wheel pants together, put some packing tape along the inside of the front part of the fairing, and laid up several layers of fiberglass.

When the epoxy cures (it cured enough to allow me to take the front half of the wheelpant off), I'll trim the "clip" (basically, a beveled edge, similar to how the wheelpants are held together) to about 1/4 to 1/2 inches. I don't think I'll need to do the same thing to the top of the fairing because (a) it mates much better as is and (b) the top of the fairing -- because it's shorter -- is much more rigid than the bottom.

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