Tailcone Longeron a bit high?

[CharlieWaffles]

I just got done drilling the longeron in the tailcone. Per the plans, the apex of the angle is level with the skin all along the side except as I was drilling the last hole near the forward bulkhead (1006) it curved a bit as I was drilling it. So now there is a very slight raise in the longeron along the 5 holes. In the picture I measured it and it seems to be about a maximum of 2/32" raised in the front. The rest of the skin is even and I believe the critical part is the deck, but will this cause any problems down the road? The other side was drilled ok the entire length.

 

[Auburntsts]

It's been awhile, but I think you're going to have a problem leaving it as is. The issue is getting the aft deck (which sits on top of the longerons), the rear bulkheads, associated brackets and side skin holes all to align when the aftdeck is riding too high in relation to those other parts due to the longeron being too high. Does that make sense? To be sure, before doing anything else, I'd cleoco the aft deck and one of the rear bulkheads in-place and see how things line up. If they don't, then you're either going to have to replace the longeron or fix it somehow.

 

[CharlieWaffles]

Thats the thing, this is at the forward portion of the tailcone. The rest of the length of the longeron from the aft deck all the way forward is indeed even per the plans. Its just before the front most bulkhead (1006) that it is up like this.

 

[Wayne Gillispie]

That is the worst place to be off

as it attaches to the fuselage longerons with 4 AN3 bolts on each side. As you bolt it up it will pull them together but may put some undue stress in that area. When you slide the tailcone onto fuselage later it is a very snug fit...unbelievable sometimes how perfect these pre-punched parts line up. If you are ever off more than 1/4 hole on anything you know something is wrong. The bolts are tightened before the fuse side skins are drilled into the fuse longerons. Also the top fwd tailcone skin is attached after tailcone and cabin top...so it may throw your holes off a little there too. Get Van's and others opinion. It is always something...but keep on going.

 

[Auburntsts]

Oops!

Oops --my bad. Interpreted the picture the wrong way. Unfortunately, the same problem applies. On the forward end, longerons from the fuse sit on top of and overlap the tailcone longerons by about 3 inches and get joined by 4 bolts per side in the overlap area when the the fuse and tailcone mate together. Because the tailcone longerons are riding high, this will cause a fuse side skin to tailcone side skin hole mismatch. If the longerons were riding low, you could probably just shim it, but I have no idea of what to do with them riding high, other than replacement. Hopefully someone here has a better solution than that.

 

[flion]

It may mess things up when you do the attachment to the forward fuselage. That longeron ties to the mid-fuselage longeron, which rests on top of it. I would suggest removing the cleco there, dropping the longeron and clamping it in its proper location and then re-drilling #30 for oops rivets back to where the creep started. I suspect the first hole or two will be too far out of line to re-drill without creating an oblong hole but you can fill the old hole (first, before drilling) with liquid aluminum or structural adhesive like hysol. Smooth the faces after the adhesive sets and then re-drill (even #40 would be fine at this point). Create a thin doubler plate to go on the inside of the longeron; its purpose is to prevent the filler from cracking out or the rivets from pulling through, so your repaired and re-drilled longeron will be sandwiched between the doubler and skin.

 

[CharlieWaffles]

Thanks all. I took the easy(er) approach and just ran down to Vans and picked up a new Longeron blank and will just make a new one since there is indeed an issue with the current one.

 

[Phil]

I don't like it.

Since this is the front of the tailcone, you're going to be twisting the tail to the left when you're join the two halves of the fuselage. 1/16" twist of the tailcone gets exaggerated at the extreme tips of the Horizontal stab.

By my quick math, the delta between your right and left HS tips could be 6-8".

Phil

 

[Phil]

Thanks all. I took the easy(er) approach and just ran down to Vans and picked up a new Longeron blank and will just make a new one since there is indeed an issue with the current one.

Good call. I typed the previous response about the same time you were typing your solution.

Phil