My wing skin was still on the bench from the other day, and since I need the bench space, I figured I should just finish the pitot mast mount. The mast is from Dynon and was designed for the RV7 wing, which apparently has different wing spar rivet spacing. That throws the "just follow the template" approach out the window. The template assumes you can grab 4 rivets from the spar flange, which sets the base of the mast up against the rib (they provide a small piece of angle to attach it to the rib). On the RV9, the spar rivets are spaced further apart, so I can only catch 3 of them. In order to get 3, the mast has to be moved away from the rib, which means I have to fabricate a different way of connecting it. Anyway, first things first - the template is correct otherwise, so I centered it over the spar rivet holes and laid out the other rivet hole locations as well as the centers of the circles that make up the fore and aft curves. With that done, it was just a matter of cutting out the big hole for the mast to slide through. I took the meat of it out with the Dremel cutoff wheel and cutting bit, then hand filed until I had a nice fit.
The base of the mast sets too far away from the rib for a piece of aluminum angle to tie them together. I needed to extend the angle another inch, so I riveted a piece of thick aluminum to it from the scrap pile. I put the wing skin in place to pull the rib into position, then very awkwardly reached inside and held the angle in place while I marked the location.
I riveted the angle to the rib web. I won't drill the face of it that gets riveted to the mast base until the skin is in place and riveted. There's too much movement in the parts without the skin, so drilling holes now would for sure end up being off (the hole that's already in the part is just a hole that was in the scrap piece - I consider it weight savings).
The instructions say to move on to fitting the canopy bubble now, but I don't like the idea of the frame just being clecoed to the skin when I do that. Not only can things move around, but the clecos sticking up would make scratching the canopy way too easy. I looked through the plans and couldn't find a reason not to just rivet the skin on first, so that's what I'm going to do. I started with the forward rivets. Most of them went in fairly easily, but there are a couple where the rivets butt up against the hinge brackets. I'm not sure I'll be able to get a bucking bar on those, so I may have to go with a few blind rivets there. I didn't finish the outer edges of the front. I have to think about what I might have for a bucking bar that will let me get into some of the tight spaces around the flanges of the side pieces. I was a little worried about how the counter sunk pop rivets would work on the aft portion where the skin goes over the small tube, but it ended up working out fine. You can see where instead of continuing the pop rivets to the outside, I just filled the holes in the skin. These are the holes were the space in between the skin and the tube means there's nothing for the rivets to grab onto anyway.
I think I'm going to fight with the fit of the front skin gap for a while. It still needs to be opened up a bit in the center - it catches the top fuselage skin and keeps the canopy from being able to open. The skin doesn't lie even with the fuselage skin in all areas either. This is a huge complaint of nearly every builder I've ever talked to. It's mostly a problem on the curved portions, and really just on the left side. I think with some gentle bending of the edge of the skin and maybe some scarfing of the edge I can get it close enough to be mostly unnoticeable. I'm not going to mess with the final gap fit until the canopy is finished though. Things just move around too much still.
Yesterday when I primed, I went ahead and shot some primer over the general area where the glare shield will be painted black. I may have to redo it, but I had the primer in the gun, so why not.
Here's a shot of underneath. You can see the filler I put on top of the outer portion of the tube to take up the space between it and the skin (it goes all of the way to the outside, but you can't see that). You can also see the filler that I used to smooth out the long strip of aluminum epoxy I had done earlier. After being primed and painted, I think it all ended up pretty decent. You can't see it in normal light, but with the camera flash you can see the small strip of cardboard that stuck to the top of the tube in the center after I had painted it and laid it out to dry. I thought it was drier than it was. I could have tried to sand it off (the carboard was stiff, not something I could soak in water and rub off) but I didn't want to destroy paint.
