Drilling F-675 (Top Rear Fuse Skin)

I'm getting ready to drill the F-675 and was curious about what technique other have used.

Have others strapped the skin one and traced the outline of the bulk heads/stringers then drilled the skins first? Or, have others pre-drilled the bulk heads/stringers then back drilled the skins?

I'm leaning towards back drilling even though it requires more time on my back but I'd be interested to hear how others have done it.

Backdrilling is the way I did it. As you said, if you want to get it right spend a little more time on your back. I used a long (12"+) #40 drill bit, makes it a little easier. Get a helper to cleco as you drill.

backdrill

I backdrilled after pre-drilling the bulkhead flanges so the long drill bit had a "pilot" hole to guide it. My wife and kids took turns helping me out with inserting the clecos from the outside and when I couldn't get their help, I cleco'd from inside and occasionally transferred them back outside.

Lay some thin plywood down over some cushions or blankets in the back to give yourself a flat surface to lay on. It's not so bad!




A few other pictures of this stage of the build are at:

http://rv6aproject.ckhand.com/Fuselage/FuselagePage16.htm

and:

http://rv6aproject.ckhand.com/Fuselage/FuselagePage17.htm

I backdrilled as well.
A few other things:
1. As you tighten the skin down with straps, the pressure will tend to distort and shift the bulkheads. I made plywood reinforcements that I clamped to the bulkheads (cut and fit so you can still backdrill). Also, to prevent the bulkheads shifting forward, I fit horizontal sticks (1x1 or 1x2) between the bulkheads so that they could not shift as the skin was pulled tight;
2. at the junction of each rib and the upper and lower skins at the longeron you will probably find that you need a shim between the rib and skin to fill a gap - otherwise you will have a pucker when riveting;
3. No need to rivet the skin on until after completing everything in the tail.
Bill Brooks
Ottawa Canada
RV-6A finishing

Like Bill said, the most important thing is to make sure you have the flimsy frames well supported. Once you start straping the skins in place they will have a tendancy to shift forward. If you have access to a roller it's best to roll the skins to conform to the shape of the frames. If not when the sides are pulled into place the top will want to rise. When I did mine I layed out the pattern on the frames, marked the centerline on the skins, and began back drilling starting at the top center. Once I got a few clecos on the top I worked down one side at a time leaving the other side open so I could reach thru to drill. I drilled small holes (#50) on the extreme edge of the skin (that will eventually be trimmed off) and hung heavy bucking bars from safety wire to help pull the skin down as I drilled. There are as many ways to do it as there are people to do it. This way worked for me and mine turned out fine.

Excellent tips, thanks.