spring back question

mikic1 · Post by **mikic1** » Thu Oct 04, 2012 7:27 am

I am about to design a ski bottom mold which will be a rocker ski.

I got experience from other projects with symmetric layup, but with rocker, that the finish product has less rocker then the mold, due to spring back/tensions pulling it back. Typically I would get 10-15%. I guess if not symmetrical layup, then it would be even more?

Does anyone here has same experience with skis and would you recommend me to do a 10-15% more aggressive rocker on the mold?

Thanks in advance,
Cheers
M

twizzstyle · Post by **twizzstyle** » Thu Oct 04, 2012 7:59 am

Will you be using heat?

mikic1 · Post by **mikic1** » Thu Oct 04, 2012 8:34 am

Yeah. Up to 180F with 2 heat blankets, one on each side is the plan.

troublemaker · Post by **troublemaker** » Thu Oct 04, 2012 9:23 am

More heat on the top.

mikic1 · Post by **mikic1** » Thu Oct 04, 2012 9:35 am

More heat in top or bottom is doable. Would this make it better, in what way?

I do not use a cat track but a custom made wide bladder, so not much heat is dissipated by the top.

chrismp · Post by **chrismp** » Thu Oct 04, 2012 10:20 am

more heat on top increases rocker. i would reccomend a temperature difference of around 10 degree C to achieve the rocker profile you want.

may i ask where you bought your custom made bladder and how much you paid for it?

mikic1 · Post by **mikic1** » Thu Oct 04, 2012 10:29 am

Ok, thanks.

And if I use same heat top and bottom, does anyone know how much spring back I could get if any?

The custom bladder was made by ATLinc. Price is very much dependent on dimensions and material, mine was 2k+ USD.

Cheers

twizzstyle · Post by **twizzstyle** » Thu Oct 04, 2012 10:44 am

mikic1 wrote: And if I use same heat top and bottom, does anyone know how much spring back I could get if any?

There are way too many variables to come up with a theoretical answer. Its one of those cases of "build it and see". Once you do one pair, you'll have a good feel for how much spring back you'll get (I think it's mostly a function of your core material).

mikic1 · Post by **mikic1** » Thu Oct 04, 2012 10:47 am

Thanks Twizz,

thats my experience from before as well. I guess this time will be no different

.

More · Post by **More** » Thu Oct 04, 2012 2:28 pm

Having just gone through this myself, I can tell you that with my reasonably burly bamboo cores, I got about a mm of fall in camber underfoot, and almost perfect representation of the tips, tails, and early rise. Equal power top and bottom.

I was baby sitting the ramp to ensure that the bottom blanket didn't run away from the top one - which has the cat track as a great big heat sink. I had to dial down the bottom blanket to a 60% duty cycle to keep them in the same ballpark. Next pair I might just ramp both hard to see how far apart they get.

doughboyshredder · Post by **doughboyshredder** » Sun Oct 07, 2012 5:57 pm

I get none.

I expected more, but I get none.

Heat top and bottom. About 80 psi. Symmetric material layup.

Ski Builders Forum

Ski Builders Forum

spring back question

spring back question