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Counter Sink Wing Flange for #8 Screws?

JVolkober

Well Known Member
I am prepring to counter sink my RV-9 wing flanges for #8 screws. Working on scrap of similar thickness as the wing flang, I found that to get the #8 screw head to fit flush the counter sunk hole had to go well beyond the depth of the material enlarging the hole well beyond #19. I suspect this is ok, since the platenut will server at the attachment point, not the flang itself. Is my understanding correct?

Also, to assure the counter sink does not wander, the instructions suggest to rivet on the platenutes and us them to guide a #30 counter sink. I have read elsewhere that some builders make a jig/guide and use a #19 counter sink instead. Recommendations?
 
Take a scrap piece of 032 Al and dimple it (for #8 screw).. then countersink so the dimple seats flush into the flange.

Using platenuts as c/s guides works... making jigs is not necessary (IMHO).
 
Yes, you are correct that the finished hole will be larger than #19 and I agree with Radomir that the platenut method works just fine. Look in RVator from about a year ago. Van's had specific suggestions about countersinking and warned against using a dimpled piece test because some people tended to countersink too far using this method. They gave some outside diameter sizes to shoot for and some pictures of what a screw should look like in the countersink. They also gave a recommended fix for those who countersunk too far. The remedy didn't look fun, so you might look for this issue before you start. Search the archives and you'll find more information on this topic and the recommended sizes.
 
Different isntructions? That sucks!

I clamped a peace of MDF behind the flange, drilled the holes to the correct size and used the MDF as a guide for countersinking. That worked fine.

By the way, the holes did look big, but I used a dimpled piece of scrap material (as suggested in the manual) and the dimple fitted right in, so if I countersunk them less deep, the skin would not lay flat. If there is different instructions than the ones in the manual, how are we to know which ones are the right ones ?
My wings are finished now, the tanks are permanently installed and everything looks fine from the outside.

Can anybody post a copy of these instructions? I do not seem to have that RVater.

Regards, PilotTonny.

 
Here's the article, Tonny. Hope it helps. Many builders did it the way you did before Van's published this RVator, so I wouldn't worry about it too much.
 
Thank you for your assitance

Thank you all for your input. I have decided to rivet the platenuts in place first to use as a guilde for counter sinking the #8 screw holes using a #30 counter sink per the instructions. My test counter sink, that I mentioned in the opening note, fits the specs in the article sent in the previous note.

An additional question, the instructions, some steps after this process, say to prime all counter sunk holes. I am assuming that means all including the holes for attaching the platenutes?

John
 
JVolkober said:
An additional question, the instructions, some steps after this process, say to prime all counter sunk holes. I am assuming that means all including the holes for attaching the platenutes?
Makes sense to do so. If I did this again, I'd just use NAS rivets to hold the platenuts on... this would leave more material in the spar and therefore less to prime--it would also speed up the rivet countersinking process!
 
Platenuts work great

I recently finished this task. I used Van's method of using the platenuts as the guide. It worked great. Here's a shot of my work in progress.

dsc1072tp5.jpg
 
You could also take a piece of scrap that will fit under the flange and clamp it in place with side clamps, drill the hole through it, then countersink. The thicker the scrap piece the better.
You can quickly move the scrap from one hole to the other. If the hole doesn't line up on the scrap for the next hole, reposition and drill a new hole.
 
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