Pressing Skis with Titanal

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Cadman
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Pressing Skis with Titanal

Post by Cadman »

We recently pressed some skis with .6mm Titanal aluminum on top and bottom. We were using wood formblocks with bolster tubes and airbags.
The skis came out with no camber. We did have some delamination issues but I am confident that the Titanal had been sitting around for awhile and had oxidized. Bonding aluminum to composites is no easy task. We found
some phospheric acid and treated the aluminum after sanding it with 120 grit to rough up the surface. We also added a very thin polyester vail between the metal and glass to form a bond line incase we had too much pressure. The combination of the treatment and the vail seemed to improve the bonding quite a bit.
I am still perplexed as to why we had no camber. It was actually reverse rocker. We planned on 5mm camber and it looks like a Volkl Mantra. It actually skied allright.
We pressed the skis at 175 Degrees for 30 minutes using two part resins from Advanced Polymetrics Inc. It is good resin. We have had minimum issues on all the glass skis.
The layup from bottom to top is
ptex
22 0z triaxial fiberglass
.6mm Titanal
wood core
.6mm Titanal
22oz triaxial fiberglass
.6mm TPU sublimated top sheet
Isosport ABS tip/tail/sidewalls
The normal good rubber strips over the edges

I am wondering if the aluminum has some kind of spring back.

Any ideas here?

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MontuckyMadman
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Post by MontuckyMadman »

I know this has been an issue before with other larger makers when metal is added.
I would only do one layer with an asym layup and .6mm sounds mighty thick but I dont really know.
sammer wrote: I'm still a tang on top guy.

skidesmond
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Post by skidesmond »

I haven't tried AL or titanal yet, but plan to soon. From research I've done, .6mm and .8mm are normal thicknesses for alpine/racing skis. AL may have sprung back. I wonder if putting a slight bend into the AL before pressing would help. How did the tips come out? Did the curve in the tip relax much or stay true to the form?

chrislandy
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Post by chrislandy »

My gut is telling me that there won't be significant springback with 0.6mm ali, I'm swaying towards differential expansion of the top and btm layers or ali. My thinking behind this? With only 30mins cure time, the heat will not have permeated through the base at the same speed as the topsheet. Might not be much but ali has quite a high coefficient of thermal expansion so the small difference over a long length i.e. a ski; may be enough to remove any camber (top contracting upon cooling, pulling out the camber)

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MontuckyMadman
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Post by MontuckyMadman »

That might make sense but then why do my carbon skis have twice the camber as my glass skis. I have to cook top heavy by 25 degrees f to get normal camber in my carbons.
sammer wrote: I'm still a tang on top guy.

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Dr. Delam
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Post by Dr. Delam »

You mentioned 175 degree heating but is this top and bottom?

chrislandy
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Post by chrislandy »

MontuckyMadman wrote:That might make sense but then why do my carbon skis have twice the camber as my glass skis. I have to cook top heavy by 25 degrees f to get normal camber in my carbons.
Interesting...

I'm looking to build my first press this year for the wakeboards so I would be interested to find out why! - I currently cook each board for 8-12hrs in an oven so never really have differential temperature/expansion/contraction or springback issues

OAC
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Post by OAC »

MontuckyMadman wrote:That might make sense but then why do my carbon skis have twice the camber as my glass skis....
My experience as well. CF, not my best friend.
I made a pair of "lightweight" skis last year with CF. I got hold of a piece of titan around 800mm long. Perfect for binding reinforcement...I thought. Bad idea! The CF did it's thing(as above) and the titan another thing. The skis came out with a wave form!! Like 2 - 3 waves over the length. And they weren't light either...
...just for pushing it, I have a pair of CF skis in the making right now. No waveform atleast, but larger camber as excpected. More on that in journal section.

chrislandy
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Post by chrislandy »

When you say larger camber, is it the same, less or more than the former?

I can understand why glass and carbon ski's/boards can end up with different camber off the same mould, purely due to the elastic modulus of the fibres and the springback force from the wooden core.

Don't forget also that some carbon fibres can have a negative co-efficient of thermal expansion so in theory they could shrink when heated - most have a very very low positive coefficient though - still approx 1/6 - 1/10th of glass fibres though

OAC
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Post by OAC »

chrislandy wrote:When you say larger camber, is it the same, less or more than the former?
Ok, more camber than with FG.
Not to mention the extra epoxi it "drinks"! I haven't focus that much on theory here, it's more of observations from my side. Interesting if it has a shrinking potential also...I thought that was all on the epoxi side?

I will try one more pair with CF in the near future. I will try the infusion method for right amount of epoxi/fiber ratio. Maybe a win, maybe a loss. :)

Cadman
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Post by Cadman »

MontuckyMadman wrote:I know this has been an issue before with other larger makers when metal is added.
I would only do one layer with an asym layup and .6mm sounds mighty thick but I dont really know.
If you do only one layer of metal, you end up with a bi-metal spring effect.
When the ski gets on the snow, the temperature change will cause the ski
to change shape so that is why they put two layers of metal to make a symetrical layup if I am not mistaken.

AMAG in europe produces the Titanal. The website is a bit hard to find
real specific thicknesses. I found one area where it mentions material thicknesses from .5mm-1.2mm. I am guessing that this material is used in other industrial applications.

Cadman
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Post by Cadman »

Dr. Delam wrote:You mentioned 175 degree heating but is this top and bottom?
That was the plan but I am guessing that the lower formblock is not a hot as the top.

I forgot the theory of changing the temperatures betwen the top and bottom and what lowers or raises the camber. If I recall a higher temperature on the bottom would give you more camber but I am not sure.

Cadman
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Post by Cadman »

We made a formblock with 12mm camber to see what happened and ended up with about 5mm camber after pressing another pair. I also noticed that the running surface shortened up also. We designed the ski to have 1310mm
running surface length and now it is around 1250mm. Scratching my head here.

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MontuckyMadman
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Post by MontuckyMadman »

So the ski had less camber and more rocker.
From my experience its more about what side reaches the resins glass trans temp first. If its the bottom, more camber if its the top, more rocker.
The carbon is definaetly a shinkage deal. Always the most rocker and camber, thats why you have to cure it top heavy.
I know its an amag product but .6 sounds heavy. I was closer to .4 in my estimates. I dont believe this product has other uses. Per piece its actually cheap compared to other non treated 7075 t6 al stateside but the moq is insane.
if the bottom was cooler or behind during the ramp then theres the answer. My resin glas trans temp is around 155f.
sammer wrote: I'm still a tang on top guy.

Cadman
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Location: Crystal Mountain, Washington

Post by Cadman »

The skis came out with rocker. The formblocks had 5mm of camber designed into the shape.

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