Tailcone F-711 ? 7 or 9

[Brockster]

Currently my tailsection is clecoed together but has not been drilled yet. All the bulkheads, tailcone and skins fit perfect except F-711. The right side aft vertical flange (f-711B, 8 rivet holes) are off about half a hole. The left side is fine. F-711A is clecoed both sides. I've believe I have done everything possible but have not had any success getting these eight holes to line up. I called Vans and they said to keep massaging it and that 1/32 off isn't that bad. It is more like 3/64. They didn't have any real words of wisdom. I know the tailcone area is noted for some potential fit problems. Found one person using the search that had the exact same problem and was considering purchasing a knew bulkhead but never updated his thread. Since everything else fits so good I am thinking about putting -4 rivets in place of the -3's in those eight spots to remove the hole misalignment. ( too many rivets in a row for oops rivets) There is plenty of edge distance and bucking the -4's here will not be a problem. I don't like the thought of oblong 3/32 holes. I've tried tightening the radius of the flanges as much as possible without causing stress on the part, squeezing the bulkheads together, but the seam on the bulkhead is tight. I wish Vans would have left the side flanges of F-711B undrilled like F-712B. F-711A would position it and the holes in the side skin would be used to locate the holes in F-711B. Anybody have any suggestions? Thanks.

 

[scard]

Sorry. All I can say is keep after it. That is one of those that you shouldn't rule out completely reforming sections of that part in creative ways. This is where the (mechanical engineer) inspired artist in you must be exercised. Maybe adjust by reforming with wood blocks and a hammer. No kidding. That is what I did. I fully agree that they should have left those holes undrilled.

 

[Paul Eastham]

Hi Paul,
I had the same problem (as has every other 7/9 builder I know) and went for AD4 rivets. All of the holes looked bad to start with, but I was able to make AD3 rivets work in many places except for one stretch of about 6 rivets. Creative drilling and dimpling can make up for some small amount of misalignment.

Whoever I talked to at Van's seemed a bit unimpressed with the idea of using AD4, but there's plenty of edge distance and it's in a fairly concealed area of the airframe. There's not much visible difference between the two anyway once all the rivets are in.

I did consider asking Van's for an undrilled bulkhead -- it seems like it would be within your "rights" since the part is so clearly misdesigned.

Paul

 

[Steve]

Vans said they have a tough time making that part due to the thick material so the replacement part may not be any better.
- Keep rolling the cone until its sides (along the top rivet edge) are close to perpendicular to its bottom as viewed from the front/rear.
- Verify the bulkhead flanges are bent at the correct matching angle.
- The top rear edge gaps won't close until you install the rudder stops.

Steve