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  #11  
Old 09-23-2012, 06:27 AM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by flyingtaran View Post
I'm using a pneumatic squeezer on what i can reach with it and a DRDT-2 cframe for the skins, and i've been extra careful to make sure the die is perpendicular to the flange
Taran, when I look at your dimples I see that the shoulders are rounded. That is typical when using squeezing devices such as a pneumatic squeezer or DRDT-2 which impart a static load and allow for quite a lot of springback.

If you use a deep throat impact dimpler and give the device a decent whack with a computhane hammer you will impart a dynamic load. The end result will be crisp dimples with well defined shoulders and a deep draw. Then your rivets (or mating dimples) will sit low and flush in the dimples.

I had a friend who complained that his rivets were not setting as flush as the rivets on my aircraft (I use a deep throat impact dimpler). He'd tried all sorts of different dimpling dies. I asked him to bring over some sample strips that had been dimpled on his DRDT-2 dimpler. I then did some dimples on the same strip so that he could see the difference.

He then sold the DRDT-2 and bought the cheaper impact dimpler...and now he's a happy camper.

Don't get me wrong. A DRDT-2 or a pneumatic squeezer ( I have one of those too) are very convenient to use and will do a reasonable dimpling job, but they're not the best tools to achieve an optimum result in my opinion. I guess in the end it just comes down to how fussy you want to be.
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Last edited by Captain Avgas : 09-23-2012 at 06:42 AM.
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  #12  
Old 09-23-2012, 07:19 AM
agirard7a's Avatar
agirard7a agirard7a is offline
 
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Location: Newport, RI
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Default Skins

Taran. If your skins have some deflection around
The dimples and do not look flat, try more pressure
This should help a lot. Especially with the new dies.
I can attest to the same issues that where solved.
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Last edited by agirard7a : 09-23-2012 at 07:22 AM.
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  #13  
Old 09-23-2012, 07:29 AM
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Brantel Brantel is offline
 
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Quote:
Originally Posted by Captain Avgas View Post
but they're not the best tools to achieve an optimum result in my opinion. I guess in the end it just comes down to how fussy you want to be.
Everyone is entitled to their opinion....my opinion is that I disagree with the above statement. You can get excellent results with these tools.

Just another data point...everyone can make up their own mind.

Heck there is at least one on here that has built with excellent results using only a pop rivet dimple die.
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  #14  
Old 09-23-2012, 08:57 AM
David-aviator David-aviator is offline
 
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The subject here is interesting, so I did a little test this morning to see how serious the problem is. I've used the hammer method of dimpling but am now committed to the DRDT-2 for reasons explained below.

What Bob says about the difference between a dynamic load and static load in setting the dimple is probably true. The problem I have with the hammer method is consistency. There are over 12,000 rivets in an RV, most require a dimple. I found with the hammer whacking method, my arm got weary and the sets were not consistent. If you are holding a large skin with one hand and attempting to get a good whack with the other, sometime it doesn't work out right. With the DRDT-2 each set is the same if you bring the handle full down through the over center part part of the application.

Anyway, below are 2 sets of dimples with the DRDT-2. (I sold the hammer whacking device so can not make a comparison) The first with .040 material the second with .020 material.

With the .040 material, the #40 dimple was perfect, the #30 almost perfect, and the #8 screw dimple not nearly perfect. (Van's recognizes the problem with #8 dimples, like with the fuel tanks, and recommends cleaning out the dimples with a light counter sink touch)

With the .020 material, both #40 and 30 were perfect and the #8 was almost perfect.

The DRDT-2 has to set right to work right. The final part of the down handle motion has to pass through an over center force so it really squeezes down.

I find greatest problem with getting a good set when riveting is proper alignment of the gun and bucking bar. Sometimes when riveting solo, that is quite a challenge.






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Last edited by David-aviator : 09-23-2012 at 08:16 PM.
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  #15  
Old 09-23-2012, 09:22 AM
aerhed aerhed is offline
 
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Not trying to be a prick, but None of those 6 look perfect. Even the #40 in the .020 looks tall. If its perfect, you should be able to pass over it with a 400 sanding block and not scuff any anodizing off the rivet head. Try it.
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  #16  
Old 09-23-2012, 02:18 PM
Bob'sRV6A Bob'sRV6A is offline
 
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Default Anyone else use the "George Orndorff Method?"

A single twirl of the debur tool knocks off a little of the shoulder and lowers the rivet head a little and does make a difference. Makes the dimple a little more like a countersink.
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  #17  
Old 09-23-2012, 07:56 PM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by Brantel View Post
Heck there is at least one on here that has built with excellent results using only a pop rivet dimple die.
I'm guessing from this statement that YOUR interpretation of "excellent" is simply not the same as MY interpretation of "excellent".
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Last edited by Captain Avgas : 09-23-2012 at 08:54 PM.
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  #18  
Old 09-23-2012, 07:59 PM
David-aviator David-aviator is offline
 
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Quote:
Originally Posted by aerhed View Post
Not trying to be a prick, but None of those 6 look perfect. Even the #40 in the .020 looks tall. If its perfect, you should be able to pass over it with a 400 sanding block and not scuff any anodizing off the rivet head. Try it.
It's an illusion, Dave.

The #8 screws are too high but the rivets are respectable. They are below grade except #30 in the the .040 material, it is just a smidgen above grade.

The shoulder of the dimpled hole is curved and when the rivet sits in there it is not flush, at least not so before being driven. The previous images show the mismatch between the rivet and the dimpled hole edge, but they are below grade except the #30 in the .040 piece.

I suppose there are dimple machines and techniques that make perfect-perfect dimples every time and the perfectionist builder will eventually find a way to get it done - perfectly. But I do believe those of us who would like to fly the airplane sooner than maybe never will be OK with the DRDT-2. At least I hope so.



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  #19  
Old 09-23-2012, 08:14 PM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by Bob'sRV6A View Post
A single twirl of the debur tool knocks off a little of the shoulder and lowers the rivet head a little and does make a difference. Makes the dimple a little more like a countersink.
This is a practice that can be very useful in specific isolated situations, but if you need to adopt it generally it indicates that you are not properly forming the dimples in the first place. It might be better to treat the cause of the problem than treat the symptoms.

The distinct disadvantage of using the deburring tool on dimples (apart from removing critical metal on thin sheets) is that it removes the alclad corrosion protection in exactly the location where you need it most (at the rivet).
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Last edited by Captain Avgas : 09-23-2012 at 08:57 PM.
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  #20  
Old 09-23-2012, 09:18 PM
aerhed aerhed is offline
 
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Ah ha. Sideshot looks mo better. Disregard previous post.
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