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Flap assembly is vexing me

ScottK

Active Member
I'm working on flaps, I have the skeleton done and ready to start skinning. Is there a trick to getting the nose skins into position? I'm clecoing the top into place, then trying to maneuver the bottom into position, but it's not wanting to go. Applying force is just twisting the spar, warping the top skin and creating oilcan dents in the nose skin. Ultimately not in a very visible spot, but very frustrating.

These nose skins (along with others) are underbent for where they need to go. Are they really intended to be installed with so much spring tension in them? If I was meant to finish bending them so they relax into their final position, I must have missed that part of the handbook, and I'm clueless as to how I'd do it anyway. I feel a bit lost today.
 
I ran into a similar problem with my aileron skins, but not on the flaps. My aileron skins were slightly underbent on the leading edge, and the resulting heavy spring force was causing a bow in the spar and causing the trailing edge to wave like a snake. I solved it ulitimately by adding a couple more nose ribs and some doublers, to add support to keep the main spar straight. The spring-open force causes the spar to want to move forward in the center and aft at the ends, so I put some extra noseribs into compression in the center 1/3 and 2/3 position, and a pair in tension on the outside edges. That was enough to hold them square.

You may find a similar approach helps on the flaps.
 
I had way more trouble with the tank and front of the wing ribs fitting right. Lucky I had a friend who helped me bend and use the 3m wheel to get them to fit better. I dont remember the flaps being as bad but Im not sure what I had for breakfast either so..

I will look for some pictures and see if I can find something that will help.
 
I just finished the flap leading edges, and ended up using 5 small ratchet straps spread across the skin and under the table to slowly pull each to the correct position. There was absolutely no way I was going to be able to do it by hand. Doing this with the clecos installed in the bottom protruding through the table was important to keep it from sliding around while tightening the straps.

I also got one oil can by trying to force it and had to massage it for a bit make it disappear. :rolleyes:
 
I just finished the flap leading edges, and ended up using 5 small ratchet straps spread across the skin and under the table to slowly pull each to the correct position. There was absolutely no way I was going to be able to do it by hand. Doing this with the clecos installed in the bottom protruding through the table was important to keep it from sliding around while tightening the straps.

I arrived at the ratchet strap method too, doing ailerons. Works great when I cleco the bottom first, then use straps to pull the top into position. It does not work for me if I cleco the top first, the angles are wrong and the flatter bottom isn't stiff enough to resist oilcanning.

I'm pondering a change in assembly sequence. I thought the ailerons went together well enough, but those have stiffeners riveted earlier. For the flaps we need access to rivet the ribs. I wonder if I should do the top skin to rib rivets first, then cleco on the bottom and nose skins (bottom then top, so I can use those straps), run the top spar rivets in the cradle, then go back to the book sequence for the bottom spar rivets. I think it makes sense. Whole lotta drilling if I'm wrong though.

I also got one oil can by trying to force it and had to massage it for a bit make it disappear. :rolleyes:

Three oilcans so far for me. :mad: Trying my best to avoid a fourth. Small consolation that they'll only be visible if you crawl under a wing.
 
I don't recall getting any oil-canning into my flaps, but I do remember that the leading edges were trick to get into place. I think I had the flaps clecoed down securely on the bench (like the plans say) with the spar just off the edge, and I installed the LE skins from the bottom then wrapped around the top starting at the forward cleco and working back. There was a fair bit of tension, but with enough hands and legs pushing in the right places I got the cleco's in and all was good.
 
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