Panther Sport Aircraft Forums

Lowrider wrote:I've used the tip of a unibit to "countersink" rivets into CM. 0.035 CM is plenty thick to get an 3/32 or 1/8" seated properly. I've also bucked 426 rivets on flat stock chromemoly when you can access the back side. Just a thought for you.

Joe,

It's not a rivet that has to seat in the countersunk hole, it's the dimpled skin. The dimensions of the dimple are larger than those of the rivet head.

Tony

I've used the tip of a unibit to "countersink" rivets into CM. 0.035 CM is plenty thick to get an 3/32 or 1/8" seated properly. I've also bucked 426 rivets on flat stock chromemoly when you can access the back side. Just a thought for you.

Jinkers wrote:Just been reading over the this thread as I am getting ready to start actual work and had a question. Not about the tail section but later when I get to the square tubes on the main fuselage... As I understand it the DIENQ dimple dies actually stretch the hole some as it creates the dimple. This seems ok on thin aluminum sheets but would it work on the steel tubing? Seems like that would be a problem and you would need to use a normal 120 degree dimple die after updrilling to #30.

Any thoughts?

Thanks,

Scott,

Because it's impossible to use a female die, it's also impossible to get a true dimple in the square tube. A depression is the best you can do. The walls of the depression are at a shallower angle than the dimple in the skin, so the skin dimple will only make point contact at the bottom of the depression. Issues down the road? Maybe, or maybe not. After testing, I chose to use CCP rivets. Barely noticeable after painting. Buy a 1' piece of .035 wall square tube and do your own testing.

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Tony

Just been reading over the this thread as I am getting ready to start actual work and had a question. Not about the tail section but later when I get to the square tubes on the main fuselage... As I understand it the DIENQ dimple dies actually stretch the hole some as it creates the dimple. This seems ok on thin aluminum sheets but would it work on the steel tubing? Seems like that would be a problem and you would need to use a normal 120 degree dimple die after updrilling to #30.

Any thoughts?

Thanks,

I had an e-mail conversation with Mike from Cleaveland regarding the dimpling process with DIENQ, since the product description has a different process from the Panther build manual.

Per Mike, the correct process with the Cleaveland DIENQ is:

1) Drill with #40 Jobber drill bit & Cleco as you go along (with proper size Cleco)
2) Disassemble
3) Deburr
4) Dimple with DIENQ
5) Use #30 reamer to enlarge hole. (Feed the reamer slowly to eliminate the need to deburr again.)

Both the skin and substructure should be dimpled with this method using DIENQ. A C-Frame should be used for the skin while a squeezer should be used for the substructure.

Cleaveland doesn't currently have a close-quarters version of this die. Mike mentioned they wouldn't be able to make them before Q2 of next year.

Sonex has 120 degree dimple die that should work for the spots you can't reach otherwise. I went ahead and ordered one:
http://www.sonexaircraft.com/eshop/cart ... ory_id=260

I recently posted that I had gotten perfect results using the DIENQ to dimple, then up drilling to #30, on the entire wing. And, I did. However, I have discovered that it is possible for the DIENQ to NOT get the dimple deep enough, thus, not allowing the rivet to completely seat below the skin surface. I am sure this is because of something I did or did not do, but, to keep it simple, going forward with this, my plan is to stick with the -43C rivets where -42C are called for on surfaces that are clearly visible, until I run out of the -42. After that, I will NOT order any more of the -42. The -42 also have other issues, like not wanting to be used by the same nose piece on the tool as should be used for that size mandrel.

Making good progress, almost finished with the second ( left ) wing, less fuel tanks.

A perfectly round hole is not 100% necessary when working with rivets, as rivets do swell to fill the hole. Where round holes are most needed is with bolts, specifically bolts in high shear load areas like the wing spars. Since bolts don't swell, a close tolerance round hole gives the most bearing surface against the bolt, and there is less chance of failure. One of the reasons I pointed out the triangular hole is so people can see what a drill bit will do while drilling. And that the dimpling and reamers will usually make the hole more round.

Having said that a hole that is too large or out of shape, a rivet may not swell enough to fit. So, it is usually best to have a decent hole that the rivet will slip fit into. Making a hole so that rivets won't spin is not a design criteria. The main thing is to have a hole that the rivet will swell to fill evenly in the entire stack-up so nothing is loose. Best way to assure that is fairly round holes of consistent diameter between the different items in the stack-up. Which is one of the reasons it is best to upsize the hole through the entire stack-up instead of doing it piece by piece.

As to the use of Burr-aways, they have good points and bad points. One thing they can do, that nothing else can is deburr inside a blind hole (fuselage tubes for example), and do both sides of the hole in one operation. One bad thing is they do tend to act like a drill bit and remove more material (which actually helped some in this case). The amount of material they remove is a function of the rpm they are used at, and the tension of the tab that does the deburring. The tension can be adjusted with loosening the set screw and moving the pilot up or down. But it takes some effort to get it right.

Actually, you need the 3/32 ( #40) Burraway for this method as you should be deburring before you use the DIENQ for dimpling. I used the method described here, where I could access the hole without having to use the "Nail Dimpler", on the entire Right wing with NO proud stems. Where I cannot use this process, I use the -43 rivet.

I would like to pose a question about the need for the hole to be perfectly round, referring to Paul's analysis. Would you be more likely to have a rivet that could not spin, with a hole that is NOT perfectly round?

Sounds like if you are going spend the $50 on the DIENQ die you also may as well cough up the $75 for a 1/8" burraway also.

Rick H