Repair Advice Needed

[777drvr]

Hi Guys,

I'm working through a snag list on my recently purchase RV-4 and could use some advise on a structural repair .

At F410 the .025 skin has worked past the AN426 AD3 rivets in a few places . It appears as if the .025 skin was CS instead of dimpled and it eventually worked through . The skins and former flanges appear to be OK otherwise .

I'm pretty sure any countersunk solution is out the window so I was thinking of replacing the 7 bottom rivets with AN470 AD4's or Cherrymax rivets. The size of the pulled out AN426 AD3 heads is larger than the shank of the AD4's but I think it would overlap enough and would certainly be better than what I have now ! Or should I go AN5 ?

Any advise would be appreciated !

Marc

[Mel]

This is a pretty heavily loaded portion on the -4.
I would go on up to -5 rivets.

[N941WR]

Marc,

When I built my -9 I used AD4's to hold the aft most bottom skin in place because of the pounding I figured that area would take, being a tail dragger and all. I called Van's and they didn't have a problem with that minor change.

Your challenge will be dimpling through all that structure. A pop-rivet dimpler might work but I don't really know.

[777drvr]

I don't think dimpling or CS'ing is an option right now . I'm willing to take a hit on the cosmetics and go with the universal head AN470's or Cherrymax rivets . If I go with solid rivets I'll have to bribe one of my skinnier friends with beer to shimmy down the tail !

Marc

[Rick6a]

Originally Posted by 777drvr

I don't think dimpling...is an option right now . Marc

Marc,

A dimpling solution is NOT necessarily out the window. Where is it written in stone that you have to use round head rivets?
Think of the flush screws that attach RV fuel tanks.

If it were my airplane, I'd likely ream the holes up to .160, then redimple the holes to accept 8-32 screws and install
structural NAS 1202 or similar:

http://www.aircraftspruce.com/catalo...es/nas1202.php

The dimpling process itself is not very hard to accomplish, but because of the location, would require that skinny helper's
assistance for a few minutes:

http://www.vansairforce.com/communit...ad.php?t=18391

As an alternative to shooting AD5 rivets, there would be little chance of dinging or denting the skin either.
If in doubt, feel free to contact Van's and run the idea by them.

[Steve Barnes]

It looks like those rivets were preloaded pretty heavily. I would consider adding a shim in the opened up area to reduce future preloading. Since its a hidden from view area, put in AN470 4 rivets or 5's if the holes are too big, like Mel suggested.
Steve Barnes The Builders Coach

[Andrew M]

My concern is that you won't have edge distance with number 5 rivets. I would look at using dimpled AN960D4 washer to replace the material chaffed out from under the head of the original fastener. Use an NAS 1097AD-4 rivet in a #3 dimpled washer. Good luck.
Andrew

[777drvr]

Hi Guys,

You'll have to bear with me because I'm not a builder but have been learning quickly about how these airplanes are built by reading books, the plan set , talking to local experts and spending way too much time on these forums soaking it all in !

I thought dimpling was out of the question because all the pieces are in place right now . I didn't think that you could dimple 3 layers in one shot . The .025" outer skin overlapping the .040" aft skin and the .032" bulkhead flange . In total .097" . A little thick I thought .

I just found some oversize shank CherryMax rivets that have a shank diameter of .140" . That's a bit closer to the head diameter of the AN426-3 that was originally in the skin . May be the easiest solution ....

Steve,

I'll see how preloaded the skin is when I drill out all the rivets I'm going to replace.

Marc

[777drvr]

Andrew,

Another interesting idea but probably the biggest hit on the looks .

I'm thinking that any repair is better than it is now . The airplane has 600 hrs on it right now but I don't know how long it took for this to happen.

Marc

[Beancounter]

Marc
I just noticed your ac registration marks.