Dimpling, need advice...

lShadowl · #1 07-31-2016, 11:02 AM

Hello guys,

I started riveting the left HS skin and noticed something on my dimpling.
I've always done countersinking and not used to dimpling.

So, when I'm using the squeeze for dimpling, the installed rivets looks way better and sits perfectly on the skin. (2 first rivets on the left)
When I use the C-Frame, with the same die, it looks under done and the rivets are not perfectly flush.

Not very clear on the pictures but trust me, it doesn't look that good.

Any advice on how to do the dimpling with the C-Frame?
What's the tolerance according to flushness?

Thanks a lot!
Here's the pic :
http://projetrv7.com/blog/wp-content...pg?i=981065958

Raymo · #2 07-31-2016, 11:32 AM

Counter sinking should only used when the skin thick enough to avoid leaving a knife edge in the whole. This is why most of the airplane requires dimpling.

Lionclaw · #3 07-31-2016, 11:58 AM

Are you sure you're whacking the c-frame hard enough with the mallet? Perhaps try on some scrap to get a feel for it. When I was still using the c-frame my whacking was done with a 5lb plastic mallet. I know there's a vocal micro-minority here that does not like the drdt-2, but that is what I use for dimpling now and rarely use the c-frame for dimpling anymore.

David Paule · #4 07-31-2016, 12:19 PM

I use the C-frame dimpling tool and a 2 lb. hammer, not a soft one. One good whack gives one good consistent dimple.

A friend has the DRDT-2 and it's okay, but I this way. This is certainly easier on my wrist.

Dave

az_gila · #5 07-31-2016, 01:17 PM

Quote:

Originally Posted by sahrens

....

As for dimpling versus countersinking, 0.040 is the minimum thickness for countersinking. Some would rather dimple 0.040 than run the risk of a knife edge. As most of the skins are thinner you will want to ensure your dimpling technique is well developed so you get the finish you want.

Actually the FAA uses a 0.032 minimum thickness countersink for a 3/32 rivet in AC 43.13, as does Vans instructions Section 5.

However the mil spec uses the 0.040 you mention.

I have seen an Art Chard RV-6 fuselage that had countersunk rivets in the 0.032 skin section and it was great. For the rest of us dimpling is easier...

maniago · #6 07-31-2016, 04:25 PM

I use a 5lb steel sledge hammer. I was told that you want to shock the metal into form when using the c-frame. I doubt that's actually true but I have no doubt that you do need a BFH to impart the same force that a squeezer can. In anycase, my dimples are the same with either tool. But one needs ear and eye protection when using the c-frame.

Z-EDD · #7 07-31-2016, 04:46 PM

You are right, those are under done. +1 on using a steel hammer, not plastic or rubber. Mine is not that big, 13 oz I think, but it does the trick. If you are already doing this then you may need to consider better dies.

bret · #8 07-31-2016, 06:08 PM

Are you going to polish or paint? I can see where a C frame would give a moore even dimple for the award winning polished plane, but I went the other way and painted.

kdedmunds · #9 07-31-2016, 06:19 PM

Recommend getting a DRDT 2. I started out using the C-Frame and was very unhappy with the results. I was able to get my hands on a DRDT as well as a set of Cleveland dies. The dimples are very consistent as well as it is must faster to set them. I'm sure it's the combination of the two. Cleveland makes a great set of dies.

bhester · #10 07-31-2016, 06:53 PM

My dimples where not forming correctly when I first started. I had a pocket in my table that the c-frame was in. I also had a 2x4 leg directly under it to the floor, but that was not enough. I took it out put it on the concrete floor, and made perfect dimples. I got a 1/4" steel plate, put it in the table pocket under the c-frame and made perfect dimples using my table. Problem solved. Hope this helps.