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#8 Screw Holes in Wing Flange for Fuel Tank

StressedOut

Well Known Member
Section 13, page 13-03 has a note preceding Step 4 that says "Use a temporary screw in the nutplates to ensure proper alignment." Looking forward in the plans where the fuel tanks are attached, it calls out an AN509-8R8 screw. However, that screw will not fit in the hole as it's just a little bit undersized. Without opening up that hole I can't use a screw to hold the nutplate.

Elsewhere in the plans I see that the proper size drill for a #8 screw is a #19 drill. I'm scanning the plans to see if a #19 hole is drilled later on but it's a bit of a slog even using PDF find. There doesn't appear to be a step in Section 13 that calls out final drilling the #8 screw holes (or for that matter the #6 screw holes for the access panels).

Am I correct is assuming that this final drill of the #8 screws is done later in the plans? If so, am I going to mess something up if I do the final drill earlier than the plans state?

One alternative I can think of for alignment of the screw hole is to use a awl. I'm a bit concerned that if you final drill the screw hole with the nutplate already installed you run the risk of damaging the nutplate.

So to summarize here are my questions:

1. Should I final drill the #8 screw holes to #19 at Section 13?
2. Is there a reason the screw hole final drill is done later?
 
I can’t answer exactly because I countersunk mine before installing the nutplates, but those holes don’t get drilled to #19 because they end up becoming a bit larger once you countersink to the final dimension in figure 3. They get knife edged.

A #19 drill is 0.1660 and the max inner dimension from figure 3 is 0.220 so I would think it’s fine to open the up to #19 before countersinking? But I didn’t do it that way so YMMV!
 
There's a bunch of notes on page 13-03 including a reference to your question. you might want to check the wiki.
 
IMHO that note is a total red herring and unnecessary.
It’s never been there for any RVs from the very beginning.
Who knows why it’s turned up in the 14. The more verbiage, the more people seem to get confused.
This is perennially over analyzed and people always try and reinvent the wheel unnecessarily.

Countersink the nut plate attach holes.
Rivet the nutplates on.
Countersink the screw holes with a #30pilot countersink using the now installed nutplate as a pilot. Practise this step on some scrap to get your depths right.
Job done
 
Thread

Art,

They are asking you to use a #8 screw to temporarily hold the nut plate when you install it, if you don’t have a nut plate jig. Before you set the nut plate rivets after countersinking them the screw hole is taken care of.

My 2 cents

RV 14A 140507 flying
Paid
 
The nutplates self align using the pre-drilled rivet holes so I don't see the point here either. I did use a small 4-40 bolt/nut combo as a clamp to hold the nutplate in place while riveting though.
 
Thanks everybody for your input. I called Vans this morning and they confirmed using a #19 drill to open the #8 screw holes as required. #27 drill for a #6 screw.
 
Drill

#8 screw is .160, so the proper drill size is #20 at .161. This is confirmed by measuring the pilot on countersink which measures .160. Countersink came in a plastic bag labeled #20 pilot.
 
#8 screw is .160, so the proper drill size is #20 at .161. This is confirmed by measuring the pilot on countersink which measures .160. Countersink came in a plastic bag labeled #20 pilot.

Depends in where you buy your tools....

All of the major suppliers of RV specific tool kits that I am familiar with supply a #19 piloted countersink to match what we specify in our build manuals.
 
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