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F-623 fitment issue

Desert Rat

Well Known Member
Hey all.

Per print, these are supposed to be flush with the edge of the associated skin. All well and good, except they aren't exactly the same angle. If I have the front edge aligned, the aft side is off by about 1/8" The deviation is the same on both sides.

What did you guys do here? Align the front side, aft side? split the difference?

Enquiring minds want to know
 

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From the perspective of a 6A builder... we have to trim the skin to fit and then drill... but otherwise they are much the same.

I think I would align the forward edges, like you have it in the picture, because of the 90 degree intersection with the fwd side skins f-670.
The rear edges of f-623 make a different type of joint with f-673, where this skin is curved/rolled over the belly, and it does not matter so much where is the aft side flange for f-623, so long as there is adequate clearance to set the shop heads.
 
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Not a problem for me

I don't recall having a problem here. Might I recommend you put the brace on the plans and make sure the brace is bent to the proper angles? I would not trim the skin because there is a lot fitting together in this area. You might have to flute the brace slightly thou.
 
Thanks for the replies. After sleeping on this and looking at some builders logs I think I see what needs to happen here.

I was picturing the F-770 side skins being on the top of the stackup between the red arrows in the picture below, but I now see that it is sandwiched between the F-776 center bottom skin and the F-623 in that area. That means that it's all good as long as the belly skin doesn't stick out so far that it won't lay down after riveting, or that I run into ED issues when match drilling the skins to the F-623.

Have I got that about right?
 

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remembering yesterday

if I remember right, one side of that brace has the side skin attached and the other has the conical section. I think I made sure the side with the side skin was perfect, and didnt worry about the other too much.

One important point, on the aft end, this gets a small bracket to the bulkhead. My bracket was not even close to being large enough and had edge distance problems. I had to make a special, larger one. I think the details are in my blog or on here.
 
Yes that sounds right. There are edge distance and clearance considerations for two
areas where F-770 meets F-776, and F-623.

1) Under the wing root, which is the location of the fwd flange of F-623, where the skins meet at a right angle. The default for the older kits is a 90 degree butt joint that is secured by F-623. Some builders bend a flange in F-770 along this edge and tuck it between F-776 and F-623. The flange needs to be notched in 4 or 5 places so as to follow the slight curvature of F-623. I'm not sure what is the default for this joint in the newer kits, but the extra flange seems like a good idea because it neatens up the joint and helps the belly skin to lay flat.

2) The conical curved part of F-770, between the rear side skin and the wing root. There is a lap joint for F-776 over F-770 and F-623. There needs to be enough rivet hole/flange clearance inside F-623 to be able to dimple and then buck the shop heads in the skinny tapered ends of F-623.

Hope that makes sense! It's a bit fiddly getting these parts to meet up properly.
 
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if I remember right, one side of that brace has the side skin attached and the other has the conical section. I think I made sure the side with the side skin was perfect, and didnt worry about the other too much.

One important point, on the aft end, this gets a small bracket to the bulkhead. My bracket was not even close to being large enough and had edge distance problems. I had to make a special, larger one. I think the details are in my blog or on here.

Same here. I made the small part bigger to span more rivets.
 
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