What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

fuel tank dimple dies

bill v

Well Known Member
do you use the fuel tank dimple die for both the rib and the skin or would it be wise to use the deeper fuel tank die on the rib and a normal die on the skin? somplace i read that clevland sugests using a deeper die on under skins when you stack three items together so that the top skins set better in the stack of dimples? thanks in advance.
 
Use the tank dies on both the skin and substructure when building the tanks. This allows the proseal to sit under the rivet head without the rivet sitting too high.

On the rest of the airframe you can use the tank dies on the substructure only to allow the normal dimples in the skin to nest better.
 
Tank Dies?? i didnt realize a specific set were needed?

Is there a special die required for this? I thought to use a standard 3/32 die?


do you use the fuel tank dimple die for both the rib and the skin or would it be wise to use the deeper fuel tank die on the rib and a normal die on the skin? somplace i read that clevland sugests using a deeper die on under skins when you stack three items together so that the top skins set better in the stack of dimples? thanks in advance.
 
Is there a special die required for this?...

With the standard dies the rivets will sit about 0.007" above the surface. This is enough to look bad, catch rags... so we designed the tank dies to eliminate this problem. They are .007" deeper allowing for the proseal that won't squeeze out from under a rivet head. Since builders that do the tanks already have the tank dies, we suggest using them on the entire substructure as well, as it eliminates most of the .011" gap between the skin and the substructure.

Links:
http://www.cleavelandtoolstore.com/prodinfo.asp?number=DIE4263T

http://www.cleavelandtoolstore.com/prodinfo.asp?number=DIE4263ss
-
 
What's the difference between the substructure dies and the tank dies?

And is there any reason not to use the tank dies generally?

Why were the regular dies designed so that the rivet head would stand proud .007?

Thanks!

Dave
 
With the standard dies the rivets will sit about 0.007" above the surface. This is enough to look bad, catch rags... so we designed the tank dies to eliminate this problem. They are .007" deeper allowing for the proseal that won't squeeze out from under a rivet head.

Let's kick a sacred cow.....

Making the dimple 0.007" deeper also increases the dimple's major and minor diameter. For example, a major diameter to match the rivet spec would be 0.1790", while the 0.007" deeper dimple would have a diameter of 0.1957". The geometry means the outer edge of the rivet head is unsupported when squeezed. The edges of the rivet are forced downward as the rivet shank is compressed.

pxbes.jpg


Don't believe it? Take a look at this sectioned rivet taken from a tank made with tank dies. Look close at the shape of the 0.007" "sealant space" under the the rivet head. Now look close at the upper surface...it's not flat. Yep, you won't catch rags on it....not with the edges bent down.

dnfxww.jpg


If the rivet is soft and ductile it may be fine. However, we know rivets are not always as ductile as we would like....:

f54zn.jpg


The above photo was taken in my shop at 10x magnification. My own tanks had dozens of rivets like this. As a leak path (or part of a leak path) the crack completely bypasses the sealant under the head. Leak or no leak, it's certainly not good structure.

BTW, go back to the picture of the cutaway rivet again. Note the nested dimples don't have the nice crisp bends of a CAD illustration. It's not the fault of the dimple die, but it does illustrate that the operator is a big factor in dimple QC. A special dimple die doesn't guarantee anything.
 
Last edited:
Interesting. Do you have cutaways of the normal dies with and without proseal for comparison. The dimples in this cutaway do not look as crisp as what I would expect from properly formed dimples with good quality dies.
 
What's the difference between the substructure dies and the tank dies?

And is there any reason not to use the tank dies generally?

Why were the regular dies designed so that the rivet head would stand proud .007?

Thanks!

Dave

Substructure are .011" deeper than standard, tank are .007" deeper.

By generally do you mean everywhere? All the rivets would have spaces around (and under) them because they don't fit the dimple.

Regular dies were designed so the rivet sits flush with the surface. The proseal is what holds the rivet proud of the surface.
 
The dimples in this cutaway do not look as crisp as what I would expect from properly formed dimples with good quality dies.

Agree. Not enough die pressure on the bottom sheet, in this case a rib flange. But that's a distraction, an aside to the real issue.

The focus here is on the oversize dimple immediately under the rivet head, 0.007" deeper and 0.0167" wider at the major diameter. Assume it to be perfectly formed as would be the case with a Cleaveland die and a skilled operator. Let's assume the use of a substructure dimple (0.011" deeper) and perfect nesting. Further assume the rivet head neither bent or cracked, and illustrations of such are mere anomalies. As intended, the tank die would result in a space under the rivet head. The space would, in theory, be filled with sealant.

Being rubber, the sealant would be roughly 10,000 times less stiff than aluminum (10,000,000/1,000). In the context of structure the rubber contributes only a tiny bit more than nothing, or about the same as air.

So, consider this question: Having purposely left a space under the rivet head, what happens when a structural load is applied to the joint?

m7vck.jpg
 
Remember, I am not a builder...yet

A little off topic, but looking at the pictures, I can see the "load bearing" part of the factory head. It is also obvious where the load bearing strength comes from the shop head. Right underneath the factory head, on the top sheet, it looks like there is a "sharp" corner that would concentrate stress into the shank of the rivet with side load. Is this just part of the game? Is this one reason why you deburr? Was the debarring not done properly....
 
Hydraulic Movement?

I would think the obvious separation between the two skins in the microphotograph would result in rivet movement during stress, resulting in the rivet head unseating some small amount.
 
O.K. Dan...let me be the first to say THANKS for the very cool photo illustration!!! It's always easier for a non-tech guy to follow these discussions with great visual examples like this.

The education continues thanks to posts and discussions like this.

All Best

Jeremy Constant
 
<snip>But that's a distraction, an aside to the real issue.
<snip>
As intended, the tank die would result in a space under the rivet head. The space would, in theory, be filled with sealant. <snip>
So, consider this question: Having purposely left a space under the rivet head, what happens when a structural load is applied to the joint?
m7vck.jpg

I understand your concern, but unless you purposely clean the proseal out of the dimple there will be a thickness of proseal in there (and that is what you want). This thickness will result in the rivet sitting high with regular dies, and flush with the tank dies. Either way the sealant is there, either way the rivet should form the same way. This has been done for 20 years on thousands of RV's with no known trouble.

As for the cracking in the rivets, we always go back and use the proseal that has squeezed out from between the sheets and smear it on the back of all of the rivet tails so they are completely covered.

The issues that you bring up do peak my curiosity though. I am headed out to create some samples using different methods to section and compare the results.

-
 
What about the paint bubbles?

Does these cracks have something to do with the paint bubbles many of us see on our tanks? Just wondering. Yes I am following the other thread as well.
 
....but unless you purposely clean the proseal out of the dimple there will be a thickness of proseal in there (and that is what you want).

Ahh, a different sacred cow. We'll come back to that one. For now, let's try to concentrate on the structural aspects of a rivet with a head not in contact with the surface. And remember, the proseal is not structural.

So again, how does the joint behave when the two sheets are pulled in opposite directions, the classic single shear?

Just for illustration, here's the AN470 equivalent with the same gap under the head. Would we consider it acceptable?

14m8cbd.jpg


As for the cracking in the rivets, we always go back and use the proseal that has squeezed out from between the sheets and smear it on the back of all of the rivet tails so they are completely covered.

Hmmm. Apparently not the first time you've seen this kind of cracked rivet head.
 
Last edited:
Apples to oranges.

Dan:

It looks like your first picture (grey sideview) of the sectioned rivet is of a rivet in a dimpled tank skin with proseal. Looks like a good seal except the proseal wasn't slathered over the top of the shop head as instructed. Was it leaking?

The second picture (orange overhead) looks like a picture of a rivet set in a skin without proseal that has been set in a hole that has been countersunk too deep. Note the sharp edges of the oblong hole. Are these pictures of the same rivet? If so, did you or the builder use a deburring tool on the hole after it was dimpled? Was it leaking? Did you slather proseal over the shop heads of your tank rivets?
 
Next Cow please....

Dan,

I'm impressed by this thread and the illustrations it contains. I've wondered whether tank dies create superior rivets or just more aesthetically pleasing rivets over the standard dies, and feel that the majority of "sealing" is done on the inside of the tank. I am curious about your "second sacred cow." I can only assume you will be writing about wet-setting the rivets at all... Popcorn in hand... Lights. camera. action!:)
 
Last edited:
I always attributed the rivet standing proud to there being a bit of proseal on the mushroom set not under the rivet head itself. I would insert the rivet wet with proseal and then wipe the manu head clean with MEK. I also would make sure no proseal from the last setting was still on the mushroom. This produced rivets that were not standing proud.
 
Ahh, a different sacred cow. We'll come back to that one.

Dan, I know that you post here often, but I don't know your experience. Could you provide some justification for your implications, or are you just theorizing? We have received multiple calls today from builders worried about their completed tanks and if they are structurally sound. I would also like you to clearly define your argument rather than 'sacred cow' as I, and apparently at least one other reader, have no idea what you are talking about. As far as the 'standard' of using a regular dimple die and wet setting rivets, virtually all RVs have been done this way. How was yours done? Have you had any problems? Has anyone else had any problems with the standard? If it is agreed that the standard is acceptable, then we can talk about the difference in the standard die and the tank die.

To answer the question about shear, in your example and using your term direct shear, there is no difference in your drawing if the rivet did not even have a head or a tail on it, the rivet would fill the hole and the shear would be based on the material and the cross sectional area of the rivet. Of course the rivet is not in simple shear which complicates things. I am just asking that you provide a basis for your concerns and your experience level for those not educated in structures.

As for my background, I have been testing dies and rivets for over 20 years as we first started experimenting with them in 1992. I received my Bachelors Degree in Civil Engineering from Iowa State University with classes including Structural Steel Design (of which Aluminum, wood or any other material can be applied) and Mechanics of Materials (dealing specifically with testing materials to elastic, yield, and failure limits). Structures classes and many others deal with forces in static and dynamic situations applicable to the area that we are talking about. I have also worked with Materials, and Aerospace PHDs at Iowa State to work on testing procedures for numerous tools and products that we have designed, some to actual destruction, and some using non-destructional analysis. I KNOW that there are Mechanical and Aerospace engineers on this forum that have far more education and experience than I do in these areas, and I hope in order to ensure accurate information rather than the proliferation of mis-information and panic, that others that are knowledgeable state their opinions.

-
 
I always attributed the rivet standing proud to there being a bit of proseal on the mushroom set not under the rivet head itself. I would insert the rivet wet with proseal and then wipe the manu head clean with MEK. I also would make sure no proseal from the last setting was still on the mushroom. This produced rivets that were not standing proud.

Very interesting Sid! As I work up my test coupon I will be sure to try this both ways as well.

-
 
I like the tank dies

I can't comment on the validity of Dan's sketches and opinions (I can, however, vouch for how firmly he holds his opinions :) ) and I don't know the engineering answers to the questions raised.

But I can relate my experience. I constructed the first tank on my RV-6 in 1998 with standard dies, then when introduced to the tank dies built the second tank with them. I like the way the rivets set with the tank dies and there was definitely a difference. I even liked them enough to write a little article about them:

http://thervjournal.com/tankdies.html

The tanks now have 13 years of flawless service (~1100 hrs) with no leaks and the tanks or wings haven't departed the aircraft in flight. I have absolutely no concern about the structural integrity of the tanks and expect them to last for many more years.

Good tanks can be built with either type of die, it is builder's choice.
 
Last edited:
Gang,

I'm enjoying this discussion. I did order a set of tank dimple dies and substructure dies yesterday from Cleveland. I'm excited to make some test samples myself prior to starting on my tanks. I have worked in tool design for several years. It only makes sense to provide room for the proseal. However, proof is in the pudding. I will post some photos of my findings as well since this is such an important topic.

Chuck
 
....your first picture (grey sideview) of the sectioned rivet...
....is there to illustrate a the wedge-shaped space between rivet head and dimple. The skin dimple is very close to 100 degrees as it should be. The unsupported rivet head bent to something more than 100 degrees, thus the wedge.

11sck80.jpg


The second picture (orange overhead) ...

...was photographed down through a diameter sizing gauge, thus the appearance of a deep, sharp edged hole.

29lhj4l.jpg


No, they are not the same rivet, just suitable illustrations.
 
Testing Criteria

The following is what I was thinking for testing. If there are any thoughts or other combinations please let me know.

tankdietestcriteria.jpg


-
 
Testing

Sounds like good test criteria to me. I am very interested to see the results of such a test. I am about to start my tanks, so this information would be great!
 
Mike, I have no noteworthy diplomas. I am familiar with the mechanics of materials. This is not about resumes.

There are two closely related sacred cows up for review. An entire recent generation of builders has embraced the dogma. One dares not question lest one be set upon by the faithful.

First is that sealant is necessary in the dimple under a rivet head to obtain a sealed tank.

Second is that a space is required under a rivet head or the sealant won't allow the rivet head to set flush.

These beliefs will not cause airplanes to fall from the sky....but they are not without unanticipated compromises.
 
Last edited:
First is that sealant is necessary in the dimple under a rivet head to obtain a sealed tank.

Second is that a space is required under a rivet head or the sealant won't allow the rivet head to set flush.

Out of curiosity in this discussion, do you see any issues with using the tank dies on the substructure (and normal dies on the skin) of the normal building of non-tank parts?

I hadn't seen that really addressed here, but I like the results, and thought we might as well include it since it is somewhat related to the tank discussion...

Very interesting thread, in any case.
 
Mike, I'd suggest a test with the tank dies on the top skin and the substructure dies on the substructure skin with Proseal. I'd hope that you'd do at least two samples of each that you've got on the list, one for pulling on a pull-testing machine to verify shear strength, and the other to section and photograph.

All - Looking at Dan's photo of the section through the rivet, and ignoring the various potential imperfections, there seems to be three places where sealing is likely:

1. With the sealant around the shop head of the rivet,

2. The sealant around the shank of the rivet between the skins, and here there's less sealing with the procedure of letting the Proseal cure first and then riveting than there will be with a wet riveting job,

3. Any sealant trapped under the head of the rivet.

Any one of these can prevent a leaking rivet. Thus, the joint is redundantly sealed.

Finally, when a shear joint is loaded to failure, there is usually enough deformation in the material and at the hole and in the fastener that the fastener tends to load up in a combination of tension, shear and bending . But that's at failure and a little before failure. The joint will leak long before that.

At load levels that are well within the elastic load range, the shear stiffness is primarily determined by the fasteners and the dimples. Trapped sealant will act somewhat incompressibly, and I think that might give it significantly more shear stiffness than if it had free edges. It might be more significant than the 1/10,000 that Dan suggested, which is based upon the relative modulus of elasticity. Perhaps someone with more elastomer experience that I have might want to comment.

In any event, there's probably normally enough shear stiffness in the design to prevent sealant failure

Dave
 
At load levels that are well within the elastic load range, the shear stiffness is primarily determined by the fasteners and the dimples. Trapped sealant will act somewhat incompressibly, and I think that might give it significantly more shear stiffness than if it had free edges. It might be more significant than the 1/10,000 that Dan suggested, which is based upon the relative modulus of elasticity. Perhaps someone with more elastomer experience that I have might want to comment.

Thanks Dave. Two useful notes on sealant.

Mixed/cured sealant is a closed cell sponge, not a monolithic rubber block. The voids have two sources, air entrained in the mixing process and and to a lesser degree solvent vapor (mostly toluene). The solvent evaporates out during cure (much like the solvent in paint), leaving the voids.

This at 10x, best I can photograph in my shop. I'm told that at greater magnification you would see many more smaller voids

2aaa3qq.jpg


A rubber solid (just like hydraulic fluid) may in fact be relatively incompressible if fully encapsulated without the possibility of extrusion. That's not the case here. The air voids are compressible (like air bubbles in hydraulic fluid, to use the same example), and all parts of the joint are open at some edge.

In any event, there's probably normally enough shear stiffness in the design to prevent sealant failure

To prevent fay and fastener seal failure (but luckily not fillet seal failure) the joint would need to be very stiff indeed.

Here are typical measured results from a sealant qualification test:

2wdx1dt.jpg


The first column, tensile strength, is noteworthy because so many folks think of sealant as some kind of high strength adhesive.

The second column, percent elongation, is of specific interest here.

For this test sample freshly cured sealant never exposed to heat or hydrocarbons had an elongation of 460%. What it means in practical application is this; assume a joint with a 0.001" gap between two surfaces, said gap filled with sealant. When the joint is placed in shear, the sealant will suffer cohesive or adhesive failure at 0.0046" relative movement between the parts.

Note elongation values drop significantly after exposure to heat and hydrocarbons. The available joint elongation before sealant rupture has become very short.

One additional note. The "AMS 2629" fluid you see here is a standard test hydrocarbon which approximates jet fuel. You may be surprised to learn the standards for our sealant do not include any requirement to test with gasoline.

As noted elsewhere, the blister database suggests both service time and elevated temperatures are required before blister formation.
 
Last edited:
When the joint is placed in shear, the sealant will suffer cohesive or adhesive failure at 0.0046" relative movement between the parts.

Note elongation values drop significantly after exposure to heat and hydrocarbons. The available joint elongation before sealant rupture has become very short.

Very enlightening! Seems "fillet vs. faying" should be next...?
 
Out of curiosity in this discussion, do you see any issues with using the tank dies on the substructure (and normal dies on the skin) of the normal building of non-tank parts?

I hadn't seen that really addressed here, but I like the results, and thought we might as well include it since it is somewhat related to the tank discussion...

Very interesting thread, in any case.

Rick,

That is why I put in sample 2 in the testing criteria. We will see this one later this afternoon.
 
Mike, I have no noteworthy diplomas. I am familiar with the mechanics of materials. This is not about resumes.

It's not about diplomas, but perhaps is about resumes. If you have been trained in fuel tank assembly and testing, you possess a whole different level of skill than someone with a ton of free time and an active imagination who may think 'hmm I think I can draw something up in CAD and get people to start questioning what has been the standard (thus proven) for years. Dogma is not the same as standard, and I personally feel that the learning that is done from this thread, and from the forum in general is a good thing. Unfortunately the internet has in itself created dogma in that answers are Googled and accepted without qualifying the contributor. In the old days if you were hanging out at the local builders hangar and he had an idea (good or bad) you were there in person, you could get a feel for the guy, now we are in a sea of experts. Don't we all know people that we go to and ask these questions, and don't we all know people that we avoid doing the same?

Again, classifying your experience is important because as like DR this is my full time job, my only source of income and the same for my three employees. To spend a day answering a theory that challenges a standard practice is educational and entertaining but does not help move forward the stack of bills on my desk. And unanswered, threatens my companies credibility and thus sales.

--I am replying to these in order so I apologize if anything has already been addressed --

-
 
....For this test sample freshly cured sealant never exposed to heat or hydrocarbons had an elongation of 460%. What it means in practical application is this; assume a joint with a 0.001" gap between two surfaces, said gap filled with sealant. When the joint is placed in shear, the sealant will suffer cohesive or adhesive failure at 0.0046" relative movement between the parts.....

This is why a well-riveted joint is necessary. The riveted joint is sufficiently stiff that it carries its design load without anywhere near that much relative movement. That's why the RV fuel tanks last.

Tight joints are difficult to seal effectively exactly because as Dan shows, a very small strain can have important consequences. Unfortunately, while a thicker joint will be more robust for sealing, it's much less robust for the flight loads.

Also, the trapped sealant I had in mind was the sealant under the head of the rivet and between the dimples and the shank of the rivet. But point taken - I hadn't known about the voids. Good catch.

Dave
 
....what has been the standard (thus proven) for years.

I understand your position Mike.

Speaking of which, a question please. About what year would you say tank dies became the standard, replacing ordinary dimple dies in the majority of tank construction?
 
dnfxww.jpg


BTW, go back to the picture of the cutaway rivet again. Note the nested dimples don't have the nice crisp bends of a CAD illustration. It's not the fault of the dimple die, but it does illustrate that the operator is a big factor in dimple QC. A special dimple die doesn't guarantee anything.

4263cutx10dim.jpg


Just to make sure it would work I 'sectioned' a rivet by sanding down on a belt sander to the center of the rivet mark. These dimples were made by using a standard die in both the top sheet and the bottom. The gap filled with debris, so I wiggled the rivet and removed it (note the tool marks). Using my fingernail I cleaned the debris and pushed any burr away from the gap and over the edge. Then I re-assembled and took this photo. Imported into CAD as reference then lines drawn and dimensioned. I did not bother to scale it as it was so close to 10x.

I realize that this is not the prosealed version yet, but you can see when you compare it to the photo above that die quality and operator skill IS important.

If anyone has a better way to section these when the proseal cures, let me know.

-
 
Last edited:
I understand your position Mike.

Speaking of which, a question please. About what year would you say tank dies became the standard, replacing ordinary dimple dies in the majority of tank construction?

Understand, but unwilling to share relevant experiences?

By standard I meant the wet setting of rivets, I apologize if I was unclear. The tank dies were designed before 1995 as they were not in our 1994 catalog but were in the 1995 catalog. It could be that we were selling them before that. However judging by the number that we sell yearly, the tanks assembled with the tank dies are still a minority. The reason I refer to wet setting as a standard is because, if your argument of unsupported rivet head is true, then it's true whether or not you are using the tank die. The rivet head will still have proseal holding it up, and if your plastic deformation of the rivet head theory is correct, it will do that either way. Thus you are challenging the standard.
 
.... judging by the number that we sell yearly, the tanks assembled with the tank dies are still a minority.

Did they seem to catch on at some point in time? Seems like a high percentage of builders are using them, as well as the QB facility.

The reason I refer to wet setting as a standard is because, if your argument of unsupported rivet head is true, then it's true whether or not you are using the tank die.

Installing fasteners wet is the standard, officially (SAE AIR4069a, Flamemaster's Sealant Application Guide, etc) and in practice.

Installing fasteners wet in an oversize dimple seems to be unique to homebuilding. Is there a published work or aerospace industry standard for it?
 
Where there is smoke...

Dan-

Thank you for all of your posts on this forum. I appreciate your experimentation, challenging of the status quo, and the results you share with the group. I believe that you are trying to contribute to the overall improvement of the building community and the elevation of homebuilding standards. Please keep it up!



Mike-

Like you, I too have some expensive pieces of paper hanging on my wall. However, I have long learned some important principles that they neglect to teach us in those lofty ivory towers that spit out expensive pieces of paper:
1) Singularly I know very little, but collectively we know a lot.
2) Listen to people who make valid arguments through sound logic and evidence because?
3) Be suspicious of people who backup their position by sheer experience, organizational rank, or by touting a piece of paper from some educational institution.
4) Doing things ?because that?s the way we?ve always done it? will only end badly.


Some of the most insightful people I've ever met don't have a high school diploma nor much experience to cloud their curiosity with. My 3 year old nephew is an amazing example.


So, what established specification did you design your dies to? What examples of established military or commercial aviation maintenance or fabrication practices can you cite that allow for the dimpling technique you promote? What structural testing have you performed to validate the fatigue life of the dimples your product creates?

Straight forward facts would be appreciated.
 
Cracks in rivet head

Gents,

I believe the cracks shown on the rivet head are cracks in the anodization not the base material. The aluminum is very malleable, if it wasn't you couldn't form the shop head.
 
Thanks to everyone who is posting on this topic. The information is invaluable. I am getting ready to assemble my fuel tanks and am experimenting with different combinations of dimple dies and assembly techniques before I do it for real.

So far, the combination that has produce the best looking results is spring back dimple dies on the skin and tank dies on the substructure.

I also sliced some of the samples to see what is going on under the rivets and was surprised by what I found. Here's a typical picture:

Fuel-Tank-Rivet.jpg


The porous structure of the sealant is evident, and it is very easy to see how leaks are going to develop if the shop head of the rivet is not sealed properly. After looking at this, I'm not sure how much added leak protection is provided by the sealant that is under the rivet.

In fact, it looks like the added sealant under the rivet may just temporarily mask a faulty shop head / fillet job that will end up leaking after a few hours service.

Please share any observations, insight, and experience you have. I'm trying to do this right.
 
Dimple Dies

Let me preface these images a bit:

0.032" tank skin material was used for the top skin.
0.025" rib thickness was used for the bottom skin to simulate rib thickness.

The top skin was formed with Cleveland's "Tank Die". The bottom skin was formed with Cleveland's "Sub-Structure Die". I used a red high temp sealant for contrast in the photos. You guys can be the judge. Multiple die combinations were tested and photographed. It appears that this combination provides support for the rivet head as well as room for the proseal. Also, the tank die did a good job in providing a sub flush rivet in the top skin. The combination of using a tank die for the top skin and the tank die for the bottom skin provided a pleasing result as well.

I hope this helps,

Chuck

001.jpg

003.jpg

002.jpg
 
Last edited:
Thanks!

Chuck,

Thanks for posting the pictures and information. I ordered a set of substructure dies from Cleaveland and will give the tank die / substructure die combination a try. It looks like part of the secret sauce is to use a combination of dies that allows parts to nest better. Thanks again for the info.
 
Now we need the pratical load and cyclic reversal testing .....

I need an aspirin. :rolleyes: Motoring along happy with my tank die dimpled tanks. I don't think they will be falling off the airframe anytime soon. Neat pictures really show what a dimple sandwich looks like. Cool!
 
Now we need the pratical load and cyclic reversal testing .....

I need an aspirin. :rolleyes: Motoring along happy with my tank die dimpled tanks. I don't think they will be falling off the airframe anytime soon. Neat pictures really show what a dimple sandwich looks like. Cool!

Yeah...really.....experienced builders exploring esoteric stuff just for entertainment (or ego inflation :rolleyes: ) is ok, but we have to consider the anxiety a prospective or novice builder is feeling when they read about joints failing or not developing sufficient strength because the "wrong" dies were used. I can also sympathize with Mike Lauritson (Cleaveland Tools) who sees business income jeopardized in a tough economy due to idle chatter tossed around on internet forums.

Thousands of tanks have been built with both types of dies and no evidence of problems due to standard or tank dies has been circulated in the vast RV community. Both types of dies can make good tanks. If there was an actual safety issue with tank dies we would have known about it years ago.
 
Last edited:
Yeah...really.....experienced builders exploring esoteric stuff just for entertainment (or ego inflation :rolleyes: )..... If there was an actual safety issue with tank dies we would have known about it years ago.

Sam, cut the personal stuff....you know better. And anyway, who said there was a safety-of-flight issue?

In Key West since last Friday. I'm currently stuck south of TS Debby and away from my home computers (this is an FBO machine). More later.
 
Last edited:
Sam, cut the personal stuff....you know better. And anyway, who said there was a safety-of-flight issue?

In Key West since last Friday. I'm currently stuck south of TS Debby and away from my home computers (this is an FBO machine). More later.

Dan, I realize you aren't on your computer, but please don't use selective editing of my post. You chopped off my sentence where I stated "experienced builders exploring esoteric stuff just for entertainment (or ego inflation ) is ok, but we have to consider the anxiety a prospective or novice builder is feeling when they read about joints failing or not developing sufficient strength because the "wrong" dies were used.".

(Hope Debby is just an irritating memory soon and you can head homeward.)

And if there are no safety concerns about the tank dies, and if it is indeed just cosmetic concerns....then why all the fuss about joints not reaching design strength? The builders calling Mike aren't concerned about cosmetics, they are worried about structural issues.

Raising questions about structural strength may not have been the intention when this thread started (but there were the photos showing poor dimples and cracked rivets??), but that is certainly where it has resided for the past several pages.
 
Last edited:
I am not at all worried about my tanks that I made with thank dies I bought from Cleveland - True I am not flying yet .. :-( ... But as Sam has pointed out ... thousands and thousands of miles have been flown with tanks made using this type dies.

I remember when the discussion was about anodised spars and fatigue life being cut in half due to the process of anodising. I also remember as a novice builder I worried about lots of things during the early build. Then over time you get more and more confident and you read and see a lot. I agree with Sam that it is a shame if Mike has to spend time answering calls from worried builders who has bought his dies, that is time that could be better spent designing new and better tools! After all, if tanks are not falling out of the sky, whats the problem ? Looking at pretty pictures of rivets cut in halves from tanks that has not failed ... what does that really tell us ?
 
Back
Top