Fuselage too open?

[claycookiemonster]

I'm approaching the finishing of the Fuselage. It's a Showplanes Fastback Mod, but I don't think that matters in this case.

The WD-808 front seatback support has been bolted in. There is the F-856 reinforcing shim that goes beneath the canopy rail and above the seatback support.

I'm finding that the holes in the F-856 do not align easily with the holes in the canopy rail unless the canopy rail is pulled inward by a large wood working clamp. At rest, the holes are about one full diameter too wide, so perhaps one half diameter too wide on each side.

I can pull the sides inward to match the holes, and in doing so the sides still seem to be straight. After the AN-426-4-6's and 4-7's and CS-4-4's and AN 509-8R8's connect the canopy rail to the seatback support and rollbar, this should be as solid as a bank vault.

Just a tiny bit concerned about having to pull the sides in to match the holes, and the resultant built in strain in the structure. Comments?

 

[PhatRV]

I found the alignment of the cockpit rail to the longeron at this point is critical to get everything fitted since the support bracket doesn't leave much room for drilling. I remember using C-clamps to tighten everything in place instead of relying solely on clecos. In my RV8, I had to replace the longeron and the cockpit rail because of the initial edge aligment issue. Didn't cost much in my case since Aircraft Spruce is 1/2 hour away and the L angle is cheap, save a bunch of shipping from Vans. The 2nd time around everything was good

 

[PhatRV]

Drawing in the question:

 

[claycookiemonster]

Yes, that drawing and that area.
The skin in that area has actually reflexed away from the overall convex curve it has coming up to the canopy rail. Right in the area of the front seat shoulder harness bar, the skin actually curves out fractionally at the top. So pulling it in slightly to match the holes seems to be called for. I'm just concerned about the shear pre-load if I put a large clamp across the whole canopy opening to pull both edges in by perhaps 1/8" overall to get the holes to match up.

 

[PhatRV]

I don't remember that I had problems fitting the F586 fitting underneath the rail. The longeron in this section should be straight so the skin should also be straight instead of being convex like you said. At this point most of the cabin fuselage skin should have been riveted right? including all the stiffer ribs. So any flexing is of concern. Have you fit the longeron yet?

You may want to annotate in a picture the location where you are having a fitment issue so we can see. The fitment of the cockpit rail to the longeron must be edge-dead-on or else there won't be any room to fit the F586.

 

[claycookiemonster]

All is well. The F-856 along with the canopy rail was pulled inward by about 1/16" of an inch on each side, or about 1/2 of the diameter of the 1/8" holes on each side. I checked with Van's first, and they ok'd it.