Oversized holes: AN5? CCP-52? Cherry Max?

[samiam]

I've got a half dozen or so holes on my FF side panel that I'm not happy with, and would like to updrill for a larger rivet. I don't really know what best practice is here. I have plenty of AN5 rivets handy, so that would be my preference. I could also order a bunch of CCP-52's. I don't have any experience with Cherry Max rivets / sizing. Just wondering what everyone else's oversized fastener of choice is.

[Bryan Cotton]

I've done both. AN5's work great in the longerons. Hard to get them set without denting the skins a bit if you are riveting the light duty channels on. Oversize Cherry max rivets are great but not cheap.

[petep]

I think the problem may have been the brittleness of the stainless steel bolts verses a regular AN bolt.

[Sonex1243]

I had to fix all my over-deburring on my flaps and ailerons. I went with oversized dome head cherry rivets. Used a #27 reamer, if my memory is correct, and bought the oversized cherry rivets from aircraft spruce. Reaming the holes took out the countersinking I induced and worked great for oversizing versus going the next size up in nominal. If your holes aren't really bad, oversized rivets may be the first best choice, plus, you wouldn't need to buy as many as I did. All you need is a cherry rivet gauge to determine the length you would need.

I also seem to remember from researching cherry's website that the rivet was a "structural" rivet designed for slightly buggered holes since it is a locking collar type rivet.

[SP1]

Well timed. I was looking at the same thing. When punching out rivets after removing the tops, I noticed that some holes looked bigger. I found this thread that references a mil manual

http://www.vansairforce.com/community/s ... hp?t=91311

Appreciate thoughts on which to purchase to replace CCP-42 and CCP-44 for oversized applications

[samiam]

Short answer: according to Kerry, any of these methods is satisfactory, so do whatever is best for your situation.

I spent a long time examining the strength of the relative types of rivets. As we know, the shear strength of a CCP-4X rivet (about 420) is greater than a corresponding size solid rivet (AN470-AD-4), making them unsuitable as a direct replacement. However, the shear strength of -AD-5 rivets is greater, so they can be substituted without weakening the structure. Similarly, CCP-54 rivets have greater strength and can be substituted. CherryMax rivets are nice because they are not as large as the next full size up; however, they do come at quite a cost.

For my own uses, I ordered 100 CCP-54 rivets to have on hand ($27). I also have a bunch of solid rivets and will use whichever suits the application.

[racaldwell]

I am using AD4 rivets where I can for multiple reasons. I pinned a dimpled hole and it is slightly larger than spec for CCC rivets. The AD rivet swells and fills the hole totally. This is another way to rivet 0.133 or so size holes. As far as strength, they do the job. My RV has lots of AD3 & AD4 rivets and have not been able to break one rivet yet in 18 yrs of acro in it.

Rick
Xenos 0057

[samiam]

As far as strength, they do the job. My RV has lots of AD3 & AD4 rivets and have not been able to break one rivet yet in 18 yrs of acro in it.

While that may be true, it is irrelevant as the two airplanes were engineered around different rivet styles.

A CCP-4X rivet has shear strength of 420, while AN470-AD-4 rivets have a shear strength of 389, making them structurally inferior. You did mention dimpling, which increases the shear strength, so in that case it is likely okay (I haven't looked at the numbers though). I just think it's important to note the effects of deviating from the manufacturer's plans. YMMV.

[Bryan Cotton]

I would not fear using solid rivets in the Waiex. Look at rivet spacings in much heavier Cessnas, Pipers, or RVs. Pretty similar.

I don't know what criteria Sonex used to assess their rivet spacing requirements. One airframer I worked for assumed 10% of the rivets were bad, essentially not there. Workmanship in the industrial production setting is not always equal to our homebuilts.

[peter anson]

As far as strength, they do the job. My RV has lots of AD3 & AD4 rivets and have not been able to break one rivet yet in 18 yrs of acro in it.

While that may be true, it is irrelevant as the two airplanes were engineered around different rivet styles.

A CCP-4X rivet has shear strength of 420, while AN470-AD-4 rivets have a shear strength of 389, making them structurally inferior. You did mention dimpling, which increases the shear strength, so in that case it is likely okay (I haven't looked at the numbers though). I just think it's important to note the effects of deviating from the manufacturer's plans. YMMV.

Years ago I did some joint strength tests using different types of rivets in 0.025" 6061-T6. The test pieces were a bit simple - just a lap joint held together by a rivet, so not representative of all parts of an aircraft, but the joints made with AD rivets were easily the strongest; about 30% stronger than the best of the pulled rivets. The mode of failure of the solid rivet joint was for the rivet to tear through the 6061 - the rivet was stronger than the material it was holding together so the slightly lower shear strength of the solid rivet compared with the SS pulled rivet didn't matter. The joint will never be stronger than the bearing strength of the material being riveted.

Peter