Spring back dimple vs Normal Dimple

Hey,

So here's a good question for you fellow builders, I was in the process of dimpling my RV-9A vstab skin today and I had some Aircraft Spruce regular dimple and so I decided to give those a try since I don't have the spring back...

Anyway, here is a picture of the finished dimpled hole with one rivet in... rivets seems to be perfectly sitting flat in the dimple and there is no deformation of the skin...




What do you think, do you see anything wrong with using these? Is it worth to buy another set of dimple dies, and is there a big difference with the spring back? Anyone has any experience with the aircraft spruce dimples?

Thanks

I used reg/tank/springback...I could not tell much difference just looking. The tank appeared to be slightly deeper. Whatever you have looks good.

I think the difference is what they call "marketing".
As long as the head sits flush to the skin, you are good. The tank dimple dies are just a bit deeper.

A little hard to tell from the picture, but the rivet looks like it's sitting deeper than flush ? The next open hole looks like the hole is on a slight angle too. Do you have a picture of the other side of the skins dimple ? It should be symmetrical and straight/even all the way around. Again, it could be the angle of the photo.

What was used to dimple with ? A hand squeezer ? I've heard of some "Matco" squeezers that don't work very well. Avery's has a good quality one.

Yes the picture is tricky sorry... the camera dind't want to focus correctly on shiny aluminium! I will try to take another one today...

As for the slight angle, I saw it too when I downloaded the picture on the computer so I went in the shop to check...it's only a optical illusion because on the skin it's perfectly straight, weird!!

As for the dimple, the rivets does seem to sit a little slightly deeper than flush, but really nothing u could ever notice if you don't really zoom on the head and pass your hand over it... over dimpling with a hand squeezer is possible!?

As for what I used, I have an ATS Super Duty Stainless Squeezer...
http://www.aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=ATSRS-1SD

Thanks

The real question is whether you want to save $38 on a $70K project on something that you will use around 10,000 times. I don't think this is marketing hype, the springback dimples will produce a better dimple, and a better looking airplane at the end of the day. It will not be any stronger, but when you see it parked in a line of RVs no-one will be asking why your rivets aren't quite so flush as the others.

There are places to save money, but (in my opinion) having the right tool for a task to be done 10,000 is probably not one of them. It's your airplane, so make your own decision, but I used the spring back dimples.

Pete

penguin said:

The real question is whether you want to save $38 on a $70K project on something that you will use around 10,000 times. I don't think this is marketing hype, the springback dimples will produce a better dimple, and a better looking airplane at the end of the day. It will not be any stronger, but when you see it parked in a line of RVs no-one will be asking why your rivets aren't quite so flush as the others.

Pete

Click to expand...

Hey Pete,

I know what you mean, but for right now I am on a really tight budget being still a student not always fun.... As soon as I finish school I will be able to buy all the tools I want...

As for the spring back dimple, I still believe too it's a marketing hype because I worked for a small aircraft structure company for a while before and I am at school for A&P on my last year now and never heard of spring back dimples before starting the RV....
Still my perfectionist mind wanted me to make sure those I had were good....

Anyway, here's a couple new pictures I tried...








Thanks!

Spring back dimple dies

Most of the major tool companies sell spring back dimple dies. Aircraft Spruce typically doesn't make their own tools, they purchase them from the other tool companies. You can call Aircraft Spruce and ask them who manufactures their dies. It wouldn't surprise me if they are actually spring back dies.

I used an old set of regular dies (1980's) on some of my early R-7A skins then switched to spring back dies further in the project. Sure wished I had the spring back dies when I started the project.

Set a few rivets and see if the head sits flush. That is really the best test of the dies.

CMBAero said:

Hey Pete,
Anyway, here's a couple new pictures I tried...

Click to expand...

The other pictures protruding side, looked nice and even and good, however, the new picture of the rivet sitting inside the dimpled hole, reminds me of a countersunk hole gone slightly too deep as you can clearly see in the picture above some of the dimple area outside the rivet and that's what had me concerned the rivet was sunken inside it.

If you use a flat/flush rivet set when bucking, there's a possibility that when bucking the rivet it may buck slightly raised up and away from the dimpled hole leaving a gap between it and the skin, but it will be flush with the surface. It really looks like your using a "fuel tank" dimple die set in the picture.

I too highly recommend a set of spring back dimple dies from Avery along with their squeezer. I prefer their hand squeezer as the yokes are interchangeable with their pneumatic squeezers. I started out with the Avery Hand Squeezer, and after borrowing a friends pneumatic squeezer I quickly found there was going to be a huge time savings using a pneumatic squeezer to squeeze the rivets over the hand version. So by the time I had the tail done, I had saved up enough to by a pneumatic squeezer for the rest of the plane and I'm soooo glad I did. I kept a no-hole yoke in the hand squeezer and C-yoke and 4" yoke in the pneumatic. Not to mention having the adjustable shaft is also a huge time saver over having to put shims in every time you want to set something of different thickness, or switch from dimpling to squeezing.

I know the feeling of being on a tight budget, but what others have said about saving $30 on a tool for an $80,000+ airplane is not a good idea. The completed airplane may lose it's value by thousands based on the sub-par quality of the workmanship.

Wicked Stick said:

If you use a flat/flush rivet set when bucking, there's a possibility that when bucking the rivet it may buck slightly raised up and away from the dimpled hole leaving a gap between it and the skin, but it will be flush with the surface. It really looks like your using a "fuel tank" dimple die set in the picture.

I too highly recommend a set of spring back dimple dies from Avery along with their squeezer. I prefer their hand squeezer as the yokes are interchangeable with their pneumatic squeezers. I started out with the Avery Hand Squeezer, and after borrowing a friends pneumatic squeezer I quickly found there was going to be a huge time savings using a pneumatic squeezer to squeeze the rivets over the hand version. So by the time I had the tail done, I had saved up enough to by a pneumatic squeezer for the rest of the plane and I'm soooo glad I did. I kept a no-hole yoke in the hand squeezer and C-yoke and 4" yoke in the pneumatic. Not to mention having the adjustable shaft is also a huge time saver over having to put shims in every time you want to set something of different thickness, or switch from dimpling to squeezing.

I know the feeling of being on a tight budget, but what others have said about saving $30 on a tool for an $80,000+ airplane is not a good idea. The completed airplane may lose it's value by thousands based on the sub-par quality of the workmanship.

Click to expand...

Thanks for the reply...

I tried squeezing a couple of rivets on a different skin with the same dies and the set rivet looks perfect! I'll try to grab a picture... anyway, I decided to buy a set of spring back dimple dies from ATS at the same time as I will pass my order for my rivet gun just to be sure and compare! Is the quality of the spring back dies from ATS good?

As for the squeezer, I wish I had bough the squeezer from Avery but now I have an ATS Super Duty Stainless Steel Squeezer, it works perfectly... the only downside is that they have their own set of yoke!

Spring back dies - what is the difference

Hi,

Could someone tell me the difference between the spring back dimple dies that Avery, P.A.R.T and the Yard Store sell is ?

Avery and P.A.R.T are ALOT more expensive than the Yard Stores spring back dimple dies and I am wondering what i am missing ?

Thanks
David

Can't speak to the others, but since I live in the same city as the Yard Store that's where my dies came from. I did buy Cleaveland's tank dies for my tanks, and there's absolutely no difference that I can tell between the quality and flushness of the set heads. The tanks look great, and so does the rest of the plane.

I do think the tank dies are a great tool for the tanks, where some extra proseal thickness may reside under the set rivet head.

After much talk about the dimple dies on this thread... I did order a set of Spring back dimple die from cleaveland tools for my 3/32 holes to replace my regular one from Aircraft Spruce...
Did a test on some left over sheet... and apart from being a little bit more sharp the dimple created by the spring back was almost the same! Once riveted, I couldn't tell the difference between the two different dies that were used!

Just my experience...may be different for the others!

krw5927 said:

...

I do think the tank dies are a great tool for the tanks, where some extra proseal thickness may reside under the set rivet head.

Click to expand...

I also use the tank dies for substructure like ribs and spars, while using the "normal" dies for the skins. Using a dimpled coupon made of scrap material the same thickness as a skin, I can actually see that the skin dimples "nest" better in substructure dimpled with "tank" dies.

Just my hypothesis (that I've never bothered to verify), but I think a "springback" die is just one that is cut to a steeper angle than the rivet's 100 deg. so that when the dimple "springs back", it ends up at 100 deg (just like you have to "over roll" a control surface leading edge, or bend an angle slightly past the desired finished angle). Its my guess that all dies which make a dimple that fits the rivet are springback dies; otherwise the dimples would end up too shallow.

Springback Dies


At Cleaveland we perfected the 1942 springback dimple die design. The term springback refers to the angle of the 'faces' of the dies rather than the angle of the 'funnel'. The male die has a concave face of a couple degrees where the female has a convex face. These angles as well as some of the other diameters and angles are critical as to how they fit the rivet, and how flat the material ends up after dimpling. Most of our competitors now have attempted to copy our 1992 die geometry, some with more success than others, but they still don't measure up to what a Cleaveland Dimple Die can do. To read more about exactly how our dies were perfected and how we keep them that way you can read the following page that I have put together to answer this question.

http://www.cleavelandtoolstore.com/custompages/springback-dimple-dies.html

As some builders don't know what to look for I will create a short tutorial on how to evaluate the dimpled skin and post it here shortly.

The statement about the tank dies for the substructure is certainly correct. The tank dies are about .007" deeper than standard to account for proseal under the rivet head. They work better for nesting than two dimples from the same die. Most builders don't want to buy another set for the substructure, but for those discerning builders we do carry a "substructure" die (DIE4263SS) that is .011" deeper so that the dimples will nest perfectly.

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Scratch One Hypothesis...

Thanks for the clarification, Milke!

Add me to the list ...

... Of people who have used both spring back and regular dies and cannot see a difference.