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Filing down rivets

R

Reilly

Active Member
Hi Guys. I need some advice from the experienced builders here please.

I am busy with the HS. The spar box assembly calls for 12 CS4-4 rivets to be riveted into countersunk holes.

I have done this but the rivets do not sit flush and the concern is that when the skin goes on it will not sit nicely as the rivets will protude under it.

The CS 4-4 rivets have quite big heads in that there is the angled portion of the head and then a verticle top compared to the AD rivets which just have the angled head all the way to the top.

I would just drill them out but I do not have enough of the rivets to replace them so the question is it advisable to file the head down or not? If so, how much could one safely file down without weakening the rivet?
 
CS4-4 are 120 degrees

Reilly,
The control horns cover 8 of those rivets. Try mounting the control horns. If they fit, then you do not have to worry about those 8 rivets. Like BigJohn said, the countersunk holes for CS4-4 need to be 120 degrees. Even if countersunk properly, the rivet heads will still stick up a little. If it is only a few thousandths, I do not think that it will be noticeable. Compare the skin with the spar to see where those rivets will contact. It is better to have a strong airplane than a good looking one, although we all want our projects to look nice. Only an engineer can answer your question. Base your decision on what is the best in the long run, not on what is easiest or convenient. Order extra rivets of each kind. Then the scarcity of rivets will not affect your decision as to whether or not to drill out questionable rivets. Chances are that grinding down a few rivet heads will not affect the strength of the airplane. But why take a chance?
Joe
 
Hi Guys

Thanks for the advice. I did use the 120 degree countersink so that it not it. (I had read the posts on that issue thankfully). I think that I did not countersink deep enough as it is a big head. I was worried about going too deep. Looks like the answer is to order more rivets and drill them out.

cheers
Reilly
 
CS4-4

Reilly,
I just skinned the horizontal stabilator. My CS4-4 rivets were not flush either, sticking up a few thousandths. The control horns fit over 8 of the rivets with no problem. The other 4 rivets were near the edge of the skin. The rivets did not hold the skin up enough to notice. You could cleco the skin in place and see how it looks. Ordering more rivets is a good idea regardless. CS4-4 are used in other places.
Joe
 
Thanks Joe. I drilled them all out yesterday and replaced after countersinking deeper. I found 175 CS4-4 rivets in my wing kit so took from that so long.

They sit much better although still slighyly proud. Should be ok though.

regards
Reilly
 
for a heads up, we just finished our wing kit and used all but a couple of the CS4 rivets that came with it. Good news though, even if you come up short, it won't hold up progress. on the wing kit they are not covered so you could fill every other hole, order more rivets and fill in later.
 
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