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Newbie Dimpling Question

Foam-the-runway

Foam-the-runway

Active Member
Hello to all and thanks in advance for answering my question.
I'm currently doing a practice kit in preparation for a real build later.
I have experience in metal fabrication but never with anything this thin.
When dimpling the skin are the same size dies used for the surfaces that it will mate to such as ribs and spars? For example will a 100deg dimpled skin mate to a 100deg dimpled rib or spar or do you have to change dies in order for them to mate?
 
Substructure dies

I started my project using the same dies for the skin as well as the substructure. About the time I got to the horizontal stabilizer I changed over to the substructure dies. The mating parts seem to fit a bit better with the substructure dies. This is a somewhat similar philosophy to the additional depth of countersinking for thicker substructure members.

YMMV, but I like the substructure dies.
 
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Be careful when using substructure/tank dimple dies. They enlarge the hole more. If you then do under-riveting (not enough diameter of the shop head) then the structure will not hold equally. Also with the rivet-length selection Vans does, the rivets are a bit on the short side, but now you need more material for a bigger hole and shop-head!

Test well before you go over to airplane structure!

Nearly 11'000 RV's are flying ... mostly done with just the same dimple dies used on skins and under-structure ... and they do not fall from the sky like a Mayfly's!
 
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Different Die Angles - Old School

In 1942 the Disney Studios made a manufacturer's training film for the Lockheed Aircraft Company, titled - Four Methods of Flush Riveting (YouTube).

At the 4:39 "mark" you will see the intro for the "Pre Dimple Method" - which illustrates the system we are using. You will note that the aircraft manufacturers of the day did use different die angles depending on which face was being processed. That distinction in die faces has passed on as far as our little airplanes go - same dies (generally) give a good enough result as to be acceptable. (Don't know about the Big Boys now).

So, early on, to be precise - there were different die angles when dimpling thinner materials (i.e. top sheet less than .040" - per the film).

Take this "history" lesson for what you paid for it.

HFS
 
What about (where possible) dimpling both pieces at the same time? Shouldn't the lower piece then match the upper one?
 
swisseagle said:
Be careful when using substructure/tank dimple dies. They enlarge the hole more. If you then do under-riveting (not enough diameter of the shop head) then the structure will not hold equally. Also with the rivet-length selection Vans does, the rivets are a bit on the short side, but now you need more material for a bigger hole and shop-head!

Test well before you go over to airplane structure!

Nearly 11'000 RV's are flying ... mostly done with just the same dimple dies used on skins and under-structure ... and they do not fall from the sky like a Mayfly's!
Click to expand...



^^^^^^^^^^^^^^^

I couldn't have written a better answer my self
 
okdonn said:
What about (where possible) dimpling both pieces at the same time? Shouldn't the lower piece then match the upper one?
Click to expand...

Mike Patey mentioned in his recent video that he does this. He believes it makes the two layers fit and lock together better.

I disagree.

It always results in an inferior dimple compared to doing the two layers individually.
In his example, it doesn't matter because the dimples and rivets wont be visible. So if it results in a level of flatness that is acceptable, there is nothing structurally wrong with it but my opinion is that it is of no benefit either.

I prefer to have riveted parts totally flat.
 
HFS said:
In 1942 the Disney Studios made a manufacturer's training film for the Lockheed Aircraft Company, titled - Four Methods of Flush Riveting (YouTube).

At the 4:39 "mark" you will see the intro for the "Pre Dimple Method" - which illustrates the system we are using. You will note that the aircraft manufacturers of the day did use different die angles depending on which face was being processed. That distinction in die faces has passed on as far as our little airplanes go - same dies (generally) give a good enough result as to be acceptable. (Don't know about the Big Boys now).

So, early on, to be precise - there were different die angles when dimpling thinner materials (i.e. top sheet less than .040" - per the film).

Take this "history" lesson for what you paid for it.

HFS
Click to expand...

It's also possible that these different die faces were developed prior to some of the research done on "springback" that is typically incorporated into modern dies. I would also guess that a lot of the sheet thickness on these WWII era combat aircraft were somewhat thicker than those typically used on RVs, albeit I'm not at all knowledgeable about Warbird material specifications and am just speculating.
 
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