Ski Builders Forum

pull teh skis at like 140 instead of cooling in teh press.

I have basically the same setup, and just did a pair. I pulled them out hot and popped them out of the cassette. That was a week ago . just finished them today and they were flat.
I've been pulling them hot and they've been coming out fine. Camber and early rise are exactly the same as my mold.
Could it be something with your layup?

So many variables.

+1 for pull them hot at 120-140f. A buddy the snowboard biz told me to pull the hot and place them on edge so gravity can't effect the camber to cool.

I keep the lam. Less than 5 deg different top-bottom during ramp up.

Seems to work for me. Camber and rise are fairly consistent between pairs.

I let them cool like this torpor temp then flash them out.

I tried, unsuccessfully, create camber with heat. I'm not saying it doesn't work at all, it just didn't work for me. My mold have zero camber. I took skis out of the press iirc at 150f while pressing kept controllers 10° difference. when removed from press skis has zero camber. I put 1"wood block under center and waits on tips and tales. Left to cool overnight in the morning about 6 to 8 mm camber.
Don't know how consistently this method will be in the future but I really like zero camber mold from it simplicity

Cook the skis at 180 on the bottom and 155 on top for most of the cycle and finish it off at 180. You will get camber.

MontuckyMadman wrote:Cook the skis at 180 on the bottom and 155 on top for most of the cycle and finish it off at 180. You will get camber.

I'm very happy with my results.

30° differential .... we not make an longbow

What results did you get?
I am going to press a splitboard soon and want to induce a bit more camber .
Was your 30 degrees c or f?

i also just got super convex bases. pulled them out at 60ºC (140ºF), which was maybe a bit too hot, then immediately moved them through -2ºC outside temp for about 5mins... obviously that was stupid, but I'm hoping that the snappy temp change was the only reason they turned out that way, as it's an easy fix...

One other thing that affects camber / base shape is your lay up.
If you don't have the same amount of fibre on both sides of the core you will bend the core.
Say you add one extra layer glass on the bottom, then the bottom layer will shrink more after cool down than the top. So you will end up with more camber / a concave base.
The same thing applies to a ski with to much camfer on the sidewalls as you will end up with less glass on the top.

If you build with carbon fibre the statement above is true in reverse..
If you add one layer of CF to the bottom and non to the top you will make a fine canoe and the other way around will make a nice longbow.

Every thing above is dependent on fibre direction..

Next you have the steel edge.. One main reason to use rubber foil ( vds) on the steel edge is to keep it's shrinkage as independent to the fibre layer and core as much as possible. (no vds makes a more concave ski)

About ramping time, In my experience I'd say its a to imprecise tool to use to make a predictable change in camber but it can be done, better to try to keep both sides as close as possible and adjust your mold.

Hi,

am trying something on the heat topic at the moment (well, in the next 2 weeks, when the vacuum table is finished and the next ski will be pressed).

So far we have been using epoxy with a working time of 45 minutes (but stays liquid much longer in room temp), then put the whole press in the sauna to heat it up.
As there is much wood below the skis, the heat mainly comes from above of course. (wood insulates quite well).

The form of the last pair I pressed had 20mm of camber, so I expected to have about 10mm of camber. Well, the result is about 1.5mm of camber ;)
As the layup was completely symmetric, the only reason I can think of is the heat difference when the epoxy cured (top curing at higher temp, so contracting more).

Finally getting to the point:
Now I have a different hardener for the epoxy which has a working time of 300 minutes. this should be enough time for the whole ski to warm quite evenly before epoxy really cures, thus giving more predictable camber results.
As long as there is an uncontrolled heat difference when pressing, results wont be really predictable - thicker woodcore, bigger difference and so on.

Will post results here when finished, is it works using a hardener with a longer curing time can be a nice solution for those that can only heat from one side.

That sounds like a very unpredictable way to heat the job. As such you will more than likely struggle to pin down a method that works every time.
I pull camber with heat (20°c hotter on the bottom) and have noticed that a thicker core will have less camber as it will resist the pulling effect of the resin.
There are lots of variables at play here and you really need a systematic approach to get reliable results.

Hi gozaimaas,

that's exactly why I want to try the long curing hardener, to give everything more time to heat (more) evenly.
As we have a very adjustable mold system I don't want any heat differences at the moment, hope it will work.
If not I really have to get into heat blanket building - wanted to avoid it because it sounds like a damn lot of work ;)

And yes, of course a thicker core will pull back more, but in my case it even increases the effect because it insulates the bottom layers better from the heat.

One day you will convert to heat blankets and all the knowledge you gained with the slow cure resin will be wasted. That day might aswell be today.
Bite the bullet man, get blankets ;-)
My lay up goes in the press for 25 minutes with the heat on. After 45 mins its out of the press with reliable results, you just cant beat it

Guess how many times in the last 2 days I had exactly this thought ;)

Will read into building heat blankets,.. The ones I found that can be bought are $$$! Like 500€ for 2 that would fit.

On the other hand: A box for heating stuff up a bit is quite nice, e.g. for waxing skis ;)

Hi,

pressed my first ski with long curing epoxy and top heat only (a heat box, not a blanket).
First impression is that it worked well, ski has about 50% of the camber of the mould. The last quite similar ski pressed with normal epoxy lost all of its camber.
So I will use long curing epoxy for now - lets see, someday heat blankets might be found in my workshop as well ;)

Regards
Philipp