The plans for the wheel pants call for the flat-head screws that hold the two halves together to have large countersunk Tinnerman washers under them. I have never cared for the look of those washers, so I pondered whether I could get away without using them. I have seen a few RVs without those washers on the wheel pants, so I'm not the only one with this crazy idea. But I worried about whether the fibreglas would stand up without the additional support that those washers provide.
So, I asked a question on the RV-List, and soon had many responses, both on and off list. Several responses said that they had had problems with the fibreglas wearing around the screw heads, so that idea looked like a non-starter. I want a good looking plane, but more than that I want one that doesn't need any more maintenance than necessary.
But an RV-4 builder sent me a good idea:
On my -4 (10 or so years ago) I used the screws with the Tinnerman washers painted to match the plane.
The only problem is keeping up with the washers along with the screws when you take it apart.
During a rebuild of the pants I did what the composite guys do: glue the Tinnerman washers in place, fill the edges with filler, and glass over the washer and filler. Run a counter sink to clean out the washer, then paint.The result is metal in contact with the screws but the washers are captive and hidden. Structurally, this is a good as it gets.
A little more work but easier down the road - you don't have to worry about losing the washers and then wondering if you have any spares that are painted.
I'm doing the same on my almost finished -6a.
Dave
So, I countersunk the holes for the screws, then assembled the wheel pant halves with screws and Tinnerman washers. I used a fine marker to trace around the washers, then disassembled everything. I used a Kutzall carving burr to remove the gel coat around the holes. Those burrs do a wonderful job carving fibreglas - they don't seem to wear, and they don't clog up.
I roughed up the surface of the Tinnerman washers and mixed up some West Systems epoxy with microfibres. I put some epoxy mix under each washer, and assembled the wheel pants, putting a drop of oil on each screw to be sure the epoxy didn't lock them in place. It seems to have turned out OK so far, with the outer face of the Tinnerman washers just below the surface of the gel coat. I put some filler on them, and we'll see how it turns out after it cures and I sand it.