Drift pins and wing bolts...

idleup · #1 06-03-2006, 10:14 AM

I have been making my drift pins and scrap bolts for test fitting my wings. The holes on the bottom of the spar seem slightly smaller than the ones on the top, is that normal? My drift pin fits well in the two top holes on each side but doesnt even go in 1/2" on the bottom holes. Even though all the holes are the same size, it seems they really arent. Has anyone else experienced this and should I just make the drift pins and test bolts smaller for the bottom holes?

- Matt

ge9a · #2 06-03-2006, 11:41 AM

The holes on my 9A were the same top and bottom. I used the 'test' bolts as called out in the instructions, ground the threads off on the grinder and applied a little grease to the bolts. I had my wife on the end of the wing moving it up and down a little to assist with sliding the bolts in, and they went right in, top and bottom, with just a little assistance tapping them with a rubber mallet. They came right out the same way. All in all, very easy.

For what it's worth, I only used the 'larger' bolts for test-fitting purposes.

idleup · #3 06-03-2006, 12:52 PM

I am able to get the test bolts in all four upper holes okay with a little persuasion from the rubber mallet, the bottom holes I can get the threaded part through but as soon as it gets to the shaft it stops completely (so much so I wouldnt want to try to force it because its not going). I am not sure what to do... I am wondering if either there is annodizing build up in there or if the holes on the triangle piece in front of the spar is slightly offset. It doe seem close enough (since the threads go through) to suggest it IS the same size hole as the top, just something making it a little too small. I do not want to dremel the hole at all. So nobody has had this same experience?

- Matt

idleup · #4 06-03-2006, 01:33 PM

Okay, I resolved the problem, maybe someone can tell me if I did something bad. I used the dremel to lightly sand the inside of the F704C hole. The F704C is the triangle peice that goes on both sides of the center spar. The bolts are still pretty tight but not so bad now that I feel like I am pounding too hard with the mallet.

- Matt

Captain Avgas · #5 06-03-2006, 08:12 PM

Quote:

Originally Posted by idleup

I have been making my drift pins and scrap bolts for test fitting my wings. The holes on the bottom of the spar seem slightly smaller than the ones on the top, is that normal? My drift pin fits well in the two top holes on each side but doesnt even go in 1/2" on the bottom holes. Even though all the holes are the same size, it seems they really arent. Has anyone else experienced this and should I just make the drift pins and test bolts smaller for the bottom holes?

- Matt

Matt, my understanding is that it is good practice to make the drift pins and insert them before you rivet on the F704C plate. That way you will have perfect alignment. It seems as though you did not do this and therefore the holes in F704C are not in perfect alignment with the hole in the wing spar. Because these are close tolerance engagements even the slightest misalignment will give you the problem you describe.

I don't think you have any option other than a very slight sanding of the F704C holes. Personally I do not think it could be a problem. Just make sure you don't sand the spar holes as well.

However this is the type of question you should address to Vans. It's a critical structural area and you could get false information from an Email forum (however well intentioned).

idleup · #6 06-03-2006, 11:04 PM

Bob, it is a QB fuse so I did not assemble the F-704.

Jeff Vaughan · #7 06-04-2006, 02:13 PM

Matt,

I have a QB and had the same problem and have found others that have had this issue as well. I had a number of discussions with the Vans folks. The conclusion is that when they riveted on the outer plate is was slightly misaligned.
My first call to Vans they told me that it was impossible and that there must be primmer in the hole or something. I called back after measuring the holes with a ball guage and got Vans attention. I concluded that the inner hole was fine and that it was at the openning where the problem was.They had me file about 1/8" into the hole to make it round.

This took quite awhile. Have not mated wings yet so I am not sure how my filing job was. The holes are tight.

You may want to check with Vans for piece of mind but it sounds as though you had the sme problem as me and solved it per Vans suggestion.

Good luck

Jeff Vaughan
RV7A
West Chester pa

Captain Avgas · #8 06-05-2006, 02:24 AM

Quote:

Originally Posted by idleup

Bob, it is a QB fuse so I did not assemble the F-704.

Matt, it therefore sounds like the QB factory did not use tight tolerance pins when they rivetted on the F704C components.

Of course when you contact Vans about these sort of things they always say: "Fancy that...we've never heard of that happening before". Yeh, right !!!

The QBs are generally held in high regard but I have seen workmanship on a number of them that was very sloppy in areas.

lrfrey · #9 06-05-2006, 05:53 AM

In the "for what it's worth dept" I had the same problem and mine is a slow build, and I had the close tolerance bolts installed when I assembled the 704.

It appears that even though everything is done the correct way there is room for slight mis-alignment especially after the side skin is installed (causing the verticals to be slightly toe'd in or out).

I do know this, .002 inch is enough to cause heartburn with these bolts. I had 10 hardware store bolts, 8 of which would go in with a little persuaiion, 2 would not, these 2 were .002 larger than the others. and are .001 smaller then the close tolerance bolts so it remains to be seem what happene at final mating!

Larry

Steve · #10 06-05-2006, 06:54 AM

Your hardware store bolts may be bent and/or oversize. I used higher quality socket head cap bolts with the threads ground way undersize and a point ground on the end.
Steve