J-Channel stiffeners too short

[rotoiti]

Building the tailcone, page 10-5 in the plans.

We have measured some of the J-Channel stiffeners a bit too short. The plans say 50 5/8 but we have cut them at 50 5/16. The part numbers affected are F-1047-F and F-1047-B. As they are, they'll just miss the first hole in the skin.

From what I have read here the stiffeners don't bear much load, they are there to make sure the skin stays in shape.

Should we reorder and remake them, should we try to double the remaining 5/16 with a small piece of j-channel or should we leave them as is?

My opinion is that since the front end of those stiffeners isn't anchored anywhere (the front end just rivets to the skin from what I see in Figure 1 on page 10-9), the cut, as we made it should be fine.

Opinions?

 

[paul330]

My preference would be to redo them. If you decide to splice, I would cut them back a bit so you have, say, 3 rivet holes short. Then cut a piece 6 holes long so you have a lap of 3 holes. The plans show a lap like this in the wings when you get that far.

As always, ask VANS support. Contrary to what you say, I believe the stiffeners carry a significant load - it's the bulkheads that are there more to keep the shape.

A friend has helped me a lot from the start of my build. The first piece of angle I gave him to cut he got it short - he was mortified! You are not alone......

 

[aerhed]

The uppers tie to tabs on the baggage bulkhead. The bottoms stub off so you can do the join. I'd splice one or two if I'd already match drilled. Otherwise I'd replace the bunch. To splice, go back 4-5 inches and cut a correct length extender piece. Butt join those and top them with another piece of stringer over both (inside). Then you have to flush rivet from underside, you can 470 rivet the J web. Only way I know that doesn't mess the skin or rivet pattern.

 

[rotoiti]

Thanks for the replies.

My opinion was based on the "j-channel stiffener doesn't carry significant load because skins do". I read it here on VAF. Quoting the post by drewhottub: Ken made it very clear that the skin is what bears most of the loads, and that the flimsy j-channels are just there to make sure that the skin holds
it's shape.

Edited to add: the stiffeners are not match-drilled yet. I just tried to fit them and they were a bit too short.

 

[mcencula]

Sort of...

Thanks for the replies.

My opinion was based on the "j-channel stiffener doesn't carry significant load because skins do". I read it here on VAF. Quoting the post by drewhottub: Ken made it very clear that the skin is what bears most of the loads, and that the flimsy j-channels are just there to make sure that the skin holds
it's shape.

Edited to add: the stiffeners are not match-drilled yet. I just tried to fit them and they were a bit too short.

While it's true that the stiffeners don't bear too much of the load, they do keep the skin from deflecting (buckling) out of position. If the skin buckles out of it's normal shape, it's compressive load capability will be a small fraction of the normal load capability. I would replace them.

 

[rotoiti]

Thanks! Ordering new ones.

 

[Janekom]

I had the same some time ago. Vans reply was that it is OK to splice them.
I have cut them shorter and then made the splice long enough to take about 4 rivets each side of the joint. I actually sent a photo to Vans and they were happy.

 

[rotoiti]

So I called Vans this morning and spoke to Ken. He said the shorter stiffeners were fine. They need to be anchored at the back bulkhead but they can be a bit shorter in the front.

He also said to save the stiffener cut-offs and rivet a doubler on top of the shorter ones when joining the fuselage to the tailcone.