New parts arrived, remaking the F-706 bulkhead - 3 hours

Today all of the new parts arrived from Vans, All new F-706 bulkhead parts (Since the bell crank axis hole is not perpendicular to the longitudinal axis of the plane), New horizontal stab attach bars, flap bearings, and new tie down.

I drove straight away into drilling the bushing holes in the F-706B lower bulkhead. Again like last time I opted for smaller bushings than the plans call for to help preserve edge distance. I went with 7/16" diameter as I just need to worry about wiring and not a manual trim cable. The holes cutting came out extremely nice again with excellent edge distance.

I managed to cut both the web flanges and the F-730 reinforcing plate before I went to far, again turned out fantastic.



I set up the assembly to check the perpendicular alignment of the bellcrank axis and it looks to be more favorable than the first F-706 I built. But it is a bit difficult to tell because I haven't drilled the angles yet for those holes.

I cut and drilled the F-729B but this time the 1/8" diameter hole that I drilled per the plans was used to locate the forward most cleco in the F-729A rib as once could reason this is what the plans intend. (Why do you drill that same hole in F-728B, as the only hole it can be is for the lower most cleco in the F-728A rib).

This is where things get a bit dumb and a "Gotcha". If you follow Vans dimension for angle length on F-729B and use the 1/8" hole for the top of the angle where it meets F-729C, you will have edge distance issues on the aft most cleco hole on the F-729B angle...the angle won't be long enough. I had this happen on my first attempt.

If you follow Vans dimension for angle length on F-729B and use the 1/8" hole for the forward most cleco hole to attach you will have proper edge distance on the aft most cleco hole on the F-729B angle, however you will have edge distance issues for the rivet on top of the F-729B angle where it meets F-729C. This is what happened on today's attempt.

I clamped on the F-729C angle and drew a hole before I drilled to make sure all was ok, and sure enough....edge distance issue.


I looked at re-doing the F-729C angle but repositioning the hole that connects F-729C/F-729B. Its tricky, But I could make it work as I can center the hole between the 17/32" distance I have to work with as a centered hole will give good edge distance. I'll think about this for a bit. I'm likely going to just re-do the F-729B angle as per my recommendation below.

I realize now that the best method to ensure proper edge distances is to cut F-729 long enough to fin inside the F-729A rib, and round the ends of the angle to fit the curves on the rib flange. Do not drill a 1/8" hole at this time. clamp the angle to the rib in its entirety and mark the forward most and aft most cleco holes, Then cleco the assembly together, clamp the F-729C angle on and mark that hole.
You know can disassemble and you have all critical holes marked and can identify the minimum required edge distances. Drill the holes needed to attach the angle to the rib. Then vert last step....trim the excess material on each end of the angle, careful to not exceed good edge distances on all three end most holes.