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Fuel Tank Attachment Question

dwollen89

Well Known Member
I'm building a 7A. I attached the nutplates to the spars and did the countersinks for the fuel tank attachment screws. Not going to lie, it took me awhile to muster up the courage to countersink those holes :eek:

I followed the instructions and all the countersinks came out really good. However, I noticed that a FEW of the nutplates are not perfectly centered between the rivet holes. I noticed it mostly on the first few holes where the nut plates are mounted at an angle. I'm guessing they shifted ever so slightly when I riveted them on prior to countersinking. My question is, how finicky are the screws for the fuel tank attachments? Should I anticipate issues here getting the screws in?

Typically, I like to put a screw into the nutplate prior to attaching them, but I couldn't do that here. The hole wasn't big enough and I didn't want to enlarge it for fear of causing issues with keeping the cutter centered.
 
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If you think the nutplate rivets may have moved sideways (dumped) than you should drill them out & try again. Offset screws will cause tension in the tank skin which wouldn't be a good thing, also screws that don't bottom out in the dimple are just ugly...
 
Clecos

Is there a good method to keep them centered when riveting? A jig of some kind? I'm going to order the jig to drill the holes.

I found that the clecos will sometimes push the nut plates off center. Make sure the clecos are clear of the center. Often times the clecos can only go in from a certain side. Also sometimes i had to put a screw in to center the nut plate. In fact, most of the time i have an allen screw in the nutplate while riveting. Other times, i will go back after the nut plate is riveted on and drill the hole in the skin a little larger tonavoid pinching the screw YMMV
 
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I found that the clecos will sometimes push the nut plates off center. Make sure the clecos are clear of the center. Often times the clecos can only go in from a certain side. Also sometimes i had to put a screw in to center the nut plate. In fact, most of the time i have an allen screw in the nutplate while riveting. Other times, i will go back after the nut plate is riveted on and drill the hole in the skin a little larger tonavoid pinching the screw YMMV


As PilotJohnS wrote I always have a screw / bolt in place with one cleco to make sure the nut plate is centered.
 
If you think the nutplate rivets may have moved sideways (dumped) than you should drill them out & try again. Offset screws will cause tension in the tank skin which wouldn't be a good thing, also screws that don't bottom out in the dimple are just ugly...

I'm not sure that I can change them now. I attached the nutplate and did the countersinks already. The countersink is perfectly centered over the nutplate screw hole, as the cutter uses the screw hole as a guide. If I were to move the nutplate now and try to countersink more, I think it would oversize the hole. Always something...lol
 
re entries

I'm not sure that I can change them now. I attached the nutplate and did the countersinks already. The countersink is perfectly centered over the nutplate screw hole, as the cutter uses the screw hole as a guide. If I were to move the nutplate now and try to countersink more, I think it would oversize the hole. Always something...lol

Unless you plan to do re entries to thru the atmosphere, I think as long as the screws are flush, you are OK. But even then, probably still Ok with a small protrusion. Build on. I remind myself all the time that this plane is amatuer
built, like the Ark, not professionally built like the titanic.
 
Unless you plan to do re entries to thru the atmosphere, I think as long as the screws are flush, you are OK. But even then, probably still Ok with a small protrusion. Build on. I remind myself all the time that this plane is amatuer
built, like the Ark, not professionally built like the titanic.

That's good advice and a good reminder. My tech advisor keeps reminding me that I'm building a tractor, lol. I'm not planning to win any awards...I just want a solid safe plane. I looked at some other builder logs that I routinely reference, and they look the same.
 
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