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  #1  
Old 10-15-2019, 08:50 AM
Bruinpilot Bruinpilot is offline
 
Join Date: Jul 2014
Location: The Woodlands, TX
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Default C frame dimpler

I just started working on the practice project number 1 in which you build an airfoil section. Already it seems that I have run into a bit of a roadblock needing to dimple the inner parts of the skin where my squeezer won?t reach.

I don?t know if I want to invest in that c frame thing at this point, there are a lot of cooler tools on my want list ahead of this. (Heck, I?d rather get a tig welder and learn to make my own c frame, but that would take quite a bit.) I was wondering if I can just mount the dimple dies in a couple of wood blocks, line it up and hammer a dimple in? Or could I use a #40 countersink on a bit of mild steel, drill a hole and put a rivet through the skin with the steel as a backup block and just rivet it until the skin dimples? Both seem cheaper and easier, but perhaps I am missing something...
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  #2  
Old 10-15-2019, 09:55 AM
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SeanB SeanB is offline
 
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These work great. See video just below product listing.

http://www.cleavelandtool.com/3_32-C.../#.XaXq9OhKiUk

Also, if/when you get to the point of buying a C Frame, look at the DRDT-2. Many of us love that tool and occasionally one comes up for sale on VAF Classifieds.

http://www.experimentalaero.com/prod...-2/DRDT-2.html
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  #3  
Old 10-15-2019, 10:39 AM
Desert Rat Desert Rat is offline
 
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Can't remember which practice kit it's in, but one of them has you make a tool to deal with this.

Basically a piece of mild steel with the equivalent of a female dimple die countersunk into it. I had a piece of 3/8" Aluminum bar handy so I used that instead of steel and it worked fine.

Slip a small socket over the shaft for the male dimple die and use masking tape (around the shank, not on the die face) so it doesn't fall off. Center everything, whack it with a hammer, done.

It helps if you put the backing plate/female die in a vice, rather than trying to hold everything.
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  #4  
Old 10-15-2019, 01:05 PM
Charles in SC Charles in SC is offline
 
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I am not familiar with the practice kit you are working on but if you can post a picture you will probably get a lot of ideas. There are a lot of ways to dimple.
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  #5  
Old 10-15-2019, 01:28 PM
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wirejock wirejock is offline
 
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Location: Estes Park, CO
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Default C-frame

C-frames come up for sale often and fairly cheap. Personally I prefer them but probably will get flamed for saying it. I think the dimples are more crisp. Basically anything that will support the male die while keeping the female die reasonably square to the male die will work. Even if it's something you hold.
A couple sections of cold rolled steel with 3/16" holes for the dies. Make sure the two are firmly in contact before hitting with a hammer.
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  #6  
Old 10-15-2019, 03:06 PM
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Larco Larco is offline
 
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Location: DVT Phoenix
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A C-frame is absolutely a needed tool or step up to a DRDT-2. If you want to have decent looking dimples you need a good 90 degree strong tool and don't be timid with the hammer! Have an experienced builder get you on the right road. I promise that the project will look only as good as your attitude and the use of proper tools will permit. Wirejock said it first and is right on. Enjoy the build. :-)
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  #7  
Old 10-15-2019, 03:45 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Quote:
Originally Posted by Bruinpilot View Post
Or could I use a #40 countersink on a bit of mild steel, drill a hole and put a rivet through the skin with the steel as a backup block and just rivet it until the skin dimples? Both seem cheaper and easier, but perhaps I am missing something...
This will work, but it’s not quite as nice. Quality dimple dies are ‘springback’ compensated, e.g. the aluminum does not take a perfect set, but springs back a bit. The die is lightly larger than the desired dimple, so the dimple is correct after a small amount of ‘spring back’. The above method requires careful riveting, so the rivet pulls the dimple into proper shape before it expands enough to fill the hole.

Edit added: I’ve previously read the opinion, which I agree with, that the C frame produces the absolutely best dimples - when a real pro is behind the hammer. For all the rest of us, the DRDT-2 is a very close second.

Last edited by BobTurner : 10-15-2019 at 03:49 PM.
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  #8  
Old 10-15-2019, 07:36 PM
Bruinpilot Bruinpilot is offline
 
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Thanks for the good info everyone. I appreciate it.
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  #9  
Old 10-16-2019, 10:59 AM
Mike Hepperlen Mike Hepperlen is offline
 
Join Date: Oct 2010
Location: Crystal Lake, IL
Posts: 25
Default C-Frame

I have a C-Frame for sale. If interested text me @815-353-4705. I am asking
$125, fob the UPS store in Crystal Lake, IL

Mike Hepperlen
Chicago area
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