Titanal is Al-7068T6 with phosphoric acid anodization

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patrickjchase
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Titanal is Al-7068T6 with phosphoric acid anodization

Post by patrickjchase »

I'm a lurker who's considering taking up ski building as a hobby, but I have a long-standing preference for metal skis. Being able to procure Titanal or an acceptable substitute is therefore a "must" for me. After searching through a bunch of threads I've noticed that a lot of people are in the same predicament. As noted in the subject I believe that 7068T6511 is basically the same material.

Here's a brief explanation of how I got there. I started with AMAG's brochure from 2009 entitled "AMAG Titanal for Sports" (I can't post URLs as I'm a new user, so bear with me).

The brochure contains 3 useful pieces of information:

1. An incomplete formulation in table 1. I say "incomplete" because Aluminum alloys contain Iron and Silicon in some amount, and real formulations invariably specify upper limits on those elements and often a few others.

2. The yield and tensile strengths in T6 temper.

3. The fact that Titanal came into being "some 25 years ago" (the brochure is from 2009, so that would put it in the mid 80s).

The last one is the most useful because we can use it to find the corresponding invention patent. AMAG's competitors employ smart metallurgists with access to mass spectroscopy, so keeping the formulation a trade secret wouldn't be a viable defense against reverse-engineering. There has to be a patent.

A quick search in the relevant date range yields European patent EP0233858 from 1987. (There's almost certainly a matching US patent but I haven't bothered to track it down). The composition specified in the patent agrees with the partial formulation in the marketing PDF above, so this patent covers Titanal. The description also lists the same set of applications as for Titanal. An invention patent (EU or US) that was filed in 1987 would have expired in 2007, so all we need to do is find a recently introduced Aluminum alloy with matching composition and mechanical properties.

Without further ado, the answer is 7068. The composition is almost identical, and the mechanical properties (modulus, yield strength, tensile strength) in T6511 temper match AMAG's stated properties for Titanal in T6.

The relatively recent loss of patent protection also explains the rumors that AMAG may be exiting the Titanal market.

On a related note, AMG's newer brochure explicitly states that Titanal for skis is prepared via phosphoric acid anodization (PAA). That's a fairly standard treatment for aerospace applications and shouldn't be difficult to obtain/reproduce. See page 9 of the AMAG brochure entitled "High performance aluminum alloys for sports and special applications" (once again, I can't post the link due to new-user limitations).
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Post by skidesmond »

Are you able to purchase the other alloys? As you know trying to buy titanal is (near) impossible. That's of goal of mine also this winter is to make a race ski using AL alloy. I've found some perforated AL online, I think the perforations will aid in bonding. It's not cheap so the search continues.
patrickjchase
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Post by patrickjchase »

skidesmond wrote:Are you able to purchase the other alloys? As you know trying to buy titanal is (near) impossible. That's of goal of mine also this winter is to make a race ski using AL alloy. I've found some perforated AL online, I think the perforations will aid in bonding. It's not cheap so the search continues.
I'm not sure yet as I haven't tried, but it looks a lot more promising than Titanal.

Titanal isn't available on the open market, period. 7068 is commonly available in extruded form. What I have not yet found is a reputable US source that sells 7068 in sheet form. Changjin Metal Product Co. advertises 7068T6 sheet on Alibaba, but I'm not sure how much I trust that
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MontuckyMadman
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Post by MontuckyMadman »

I spent three weeks on this last year. I visited countless aeronautics forums learned all about chromate and PAA treatment as well as some others.
I found a aeronautics supplier company in socal but coming up with the right thickness is tough. I think they had 2 that fit the bill but that's speculation on my part.
It would be $600 for a 5x10 sheet cut to spec and shipped.
Then you have to prep the material.
Then you really have to adjust your cores for the thickness of metal you have. Better have a cnc and do at least 5 pairs all the same to get the flex dialed and then there's the ride to consider.
When its all said and done you are talking thousands of dollars and a hundred or more man hours.
There's a good thread on tgr right now about metal.
A few small european manufacturers have chimed in saying when it was all said and done after more than 20 protos with metal they went back to good wood cores and the right blend of resins and composites yielded a better ski that they were looking for.

Just adding metal is not the answer. You have to have the right blend of rubber, wood , plastic and resin to make a metal ski damp but lively and smooth.
Good luck. Ill dig up my metal company and quote info when I have time

I forgot to mention I was going to buy some titanal from sean at donek and the guys at prior in bc and it was going to be cheap, really cheap, like 4 bucks a meter and it was 170mm wide.
.3mm and .4mm thick.
But then amag announced they were discontinuing the supply of titanal in certain thicknesses. so they couldn't sell it to me.
I think .2mm would be better and the english standard equivalent is somewhere in between in inches.
The cost for the sheet from the aeronautics supplier and the cost to treat the material was going to be double that at least.
Just didnt make sense unless you have all your protos in line and you are going into production.
that being said there are a few people on here who have made metal skis and have had good results using the chromate treatment but its super dirty and messy and a PITA.
and another thing in my opinion you have to press the shit out of a metal laminate to get it to bond solid. Like 90psi or higher.
anytime I put al on the tail of a ski it lasted for a few weeks and then fell off but no acid treatment just abrade and clean with mek.
PM gear uses al in teh tip and tail but they are at like 90 psi. so thats my experience.
sammer wrote: I'm still a tang on top guy.
patrickjchase
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Post by patrickjchase »

MontuckyMadman wrote:I spent three weeks on this last year. I visited countless aeronautics forums learned all about chromate and PAA treatment as well as some others.
I found a aeronautics supplier company in socal but coming up with the right thickness is tough. I think they had 2 that fit the bill but that's speculation on my part.
It would be $600 for a 5x10 sheet cut to spec and shipped.
Then you have to prep the material.
Then you really have to adjust your cores for the thickness of metal you have. Better have a cnc and do at least 5 pairs all the same to get the flex dialed and then there's the ride to consider.
When its all said and done you are talking thousands of dollars and a hundred or more man hours.
Out of curiosity, did you arrive at the same replacement material as I did (7068T6) or were you pricing a more standard alloy like 7075? I searched for 7068 in the forums and didn't find any references, so I wasn't aware that anybody else had identified it as Titanal.

I'm in the process of building a fairly robust CNC router (linear guides in all axes, ballscrew + rotating nut drive, VFD spindle), so if I take up ski building I'll be using CNCed cores and moulds. The router is designed to mill aluminum alloys with reasonable precision, so I'm leaning towards doing a proper "enclosed" mould and pre-cutting the metal, glass, and sidewalls to shape.

If I do a proper mould then I think I can get 100 psi at the topsheet even with a 50 psi firehose (the key is to design the mould "pusher" such that it applies all of the force from the firehose to the topsheet).
MontuckyMadman wrote: I forgot to mention I was going to buy some titanal from sean at donek and the guys at prior in bc and it was going to be cheap, really cheap, like 4 bucks a meter and it was 170mm wide.
.3mm and .4mm thick.
But then amag announced they were discontinuing the supply of titanal in certain thicknesses. so they couldn't sell it to me.
I suspect that AMAG is discontinuing some Titanal products because they've lost patent protection and are facing competition. The quoted bulk prices for Chinese-made 7068 are surprisingly low (a small fraction of what you cite above).
patrickjchase
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Post by patrickjchase »

Sorry about the double reply, but...
MontuckyMadman wrote: Then you really have to adjust your cores for the thickness of metal you have. Better have a cnc and do at least 5 pairs all the same to get the flex dialed and then there's the ride to consider.
When its all said and done you are talking thousands of dollars and a hundred or more man hours.
Before I address this I should probably mention that I'm trained as a mechanical engineer but work as a software/systems architect. My approach is embarrassingly analytical.

I have the ability to measure piecewise longitudinal and torsional flex, and some limited ability to measure damping/dynamics. I've already characterized the flex of a couple skis that I want to use as starting points (i.e. "like this but 20% stiffer"), and have also sectioned them (don't worry, they were already dead) and characterized their construction. With that as a starting point, I plan to do the following:

1. Build a rough finite-element model of the core, glass, and metal. This is actually fairly easy to do if it doesn't have to be "intrinsically accurate".

2. Manufacture a series of small (15" long or less) test sections with a range of constructions and core thicknesses, and use those to tune the model from (1) via fudge factors. This is also where I would fine-tune the mould design to address the pressure issue you raised.

3. Use the tuned model to design the final construction.

This approach doesn't need to cost all that much money. It will take a LOT of time, but that's sort of the point of a "hobby" in the first place, right?
MontuckyMadman wrote: I forgot to mention I was going to buy some titanal from sean at donek and the guys at prior in bc and it was going to be cheap, really cheap, like 4 bucks a meter and it was 170mm wide.
.3mm and .4mm thick.
.3-.4 mm is 11-15 mils, which sounds really thin. Some back-of-the-envelope math suggests that a metal layer that thin wouldn't do much to ski flex. The skis that I've sectioned so far have had metal layers in the 20-30 mil range. Even my wife's old Bandit XXs had a pair of ~20 mil layers...
MontuckyMadman wrote: anytime I put al on the tail of a ski it lasted for a few weeks and then fell off but no acid treatment just abrade and clean with mek.
I don't think that would help much unless you were somehow able to protect the sheet from oxygen in the time between removing the MEK and applying resin. Aluminum oxidizes *fast* IIRC.
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MontuckyMadman
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Post by MontuckyMadman »

sound slike you got it all figured out then!
sammer wrote: I'm still a tang on top guy.
Richuk
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Post by Richuk »

Nice bit of research!

I was wondering what FEA platform you intend to model within. Have you taken a look at e-fea. It has a ski model within the program.

Are you thinking DMTA testing. I hear its a cheap and accurate method and would give an insight into model you have already sectioned.
patrickjchase
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Post by patrickjchase »

Richuk wrote:Nice bit of research!

I was wondering what FEA platform you intend to model within. Have you taken a look at e-fea. It has a ski model within the program.

Are you thinking DMTA testing. I hear its a cheap and accurate method and would give an insight into model you have already sectioned.
I have no idea which FEA platform. I haven't gotten there yet E-FEA does indeed look like a very nice option, particularly for somebody who's software-literate to start. I actually developed some FEA SW back in the 90s so working from source is tempting.

I was indeed thinking of something along the lines of a free-resonance DMA (I don't care so much about "T" for a number of reasons).
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Re: Titanal is Al-7068T6 with phosphoric acid anodization

Post by knightsofnii »

patrickjchase wrote:I'm a lurker who's considering taking up ski building as a hobby,
rad man! its an amazing time

patrickjchase wrote:but I have a long-standing preference for metal skis. Being able to procure Titanal or an acceptable substitute is therefore a "must" for me.
Sounds rad, but unless you have a trust fund somewhere burning a hole in your pocket, i'd suggest getting a solid year of ski building under your belt before even bothering to mess around with materials.

Many of us here are mechanical engineers. I'm here to say very little of that schooling and engineering experience in the field has translated into better boards... of course every bit of knowlege helps... but the biggest contributor has been trial and error and lots of physical R&D.

Not to discourage you, go for the titanal! but master the basics of sticking layers... because that takes a ton of work!
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Post by skidesmond »

Most skis specs that I've looked at use .5mm or .8mm thick titinal. Finding AL alloy that thin in length for skis is difficult and pricey.

And as mentioned chemically treating it for good bonding is messy/hazardous.
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MontuckyMadman
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Post by MontuckyMadman »

The metal in skinny slalom skis might be .8 but the stuff in fat skis is definitely thinnner.
Look at the new bodacious or the line mother ship. Depend if its one layer or 2.
sammer wrote: I'm still a tang on top guy.
patrickjchase
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Re: Titanal is Al-7068T6 with phosphoric acid anodization

Post by patrickjchase »

knightsofnii wrote:
patrickjchase wrote:but I have a long-standing preference for metal skis. Being able to procure Titanal or an acceptable substitute is therefore a "must" for me.
Sounds rad, but unless you have a trust fund somewhere burning a hole in your pocket, i'd suggest getting a solid year of ski building under your belt before even bothering to mess around with materials.

Many of us here are mechanical engineers. I'm here to say very little of that schooling and engineering experience in the field has translated into better boards... of course every bit of knowlege helps... but the biggest contributor has been trial and error and lots of physical R&D.
I don't have a trust fund, but I do have a reasonably successful 2-decade career as an engineer and then as a systems architect. I have a profound appreciation for the gap between book and practical knowledge (though I've also come to believe that some of those gaps come from misunderstanding the underlying physics, and that those constitute opportunities...). I also know how to take "targeted" risks - If I take risk in one area then I'll offset it by being conservative in others so that I can focus my efforts appropriately. I've also done composites and laminates before, though with vacuum bagging and autoclaves rather than a press - I'm admittedly naive there. Metal and pressing are my chosen risks.

Money isn't infinite, but it's not a tight constraint either
Not to discourage you, go for the titanal! but master the basics of sticking layers... because that takes a ton of work!
Yep. I probably should have been explicit that there are 2 reasons why I want to press a bunch of small (15-18" long) test specimens

1. To calibrate my models as I said

2. To do deflection and pull/peel testing in conjunction with water immersion and thermal cycling.

The general idea is to trade time (the effort required to iterate through a bunch of test specimens that don't actually do anything useful on snow) for cost ("throwaway pairs" cost a lot more)
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Post by vinman »

or you can actually build something and enjoy skiing it
Fighting gravity on a daily basis
www.Whiteroomcustomskis.com
patrickjchase
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Post by patrickjchase »

Vinman wrote:or you can actually build something and enjoy skiing it
Sigh... I think it should be reasonably obvious that different people have different objectives. If that's yours then more power to you. It isn't mine.

If I just want something to enjoy skiing then I can walk into a ski store and grab whatever I want. It's a heck of a lot cheaper (as in: more than an order of magnitude) at the going rate for my time. For me the challenge that comes from setting a high bar is what drives the enjoyment. Clear enough?
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