Kelvin just made a pair of skis where the core material is foam. they are impressively light. we'll have photos up soon, and Kelvin will spill the beans...
stay tuned.
foam-core skis
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Sounds great! Good work!
About the foam cores, I heard a lot of people complaining about foam-core skis that these were losing camber and stiffness after a while. What is your opinion on this? Or is this, if this is really the case no big drawback because of the weight reduction you obtain using foam?
Buuk
About the foam cores, I heard a lot of people complaining about foam-core skis that these were losing camber and stiffness after a while. What is your opinion on this? Or is this, if this is really the case no big drawback because of the weight reduction you obtain using foam?
Buuk
I would like to make a foam core myself.
There are some things to keap in mind however.
Foam microcells or easier to collapse and therefore if the ski bends extremely it will damage some microcells. I presume the result will be some camber and stiffness loss in that case.
In my eyes foam cores are more for hardpack than off-piste or how do you call that.
My question is however how bendable is such a core compared to a wood core before lamination.
Geoff
There are some things to keap in mind however.
Foam microcells or easier to collapse and therefore if the ski bends extremely it will damage some microcells. I presume the result will be some camber and stiffness loss in that case.
In my eyes foam cores are more for hardpack than off-piste or how do you call that.
My question is however how bendable is such a core compared to a wood core before lamination.
Geoff
And what about a hybrid wood-foam ski... this gives a light and durable ski. But I don't know what technical problems this brings along.BigG wrote: Foam microcells or easier to collapse and therefore if the ski bends extremely it will damage some microcells. I presume the result will be some camber and stiffness loss in that case.
And how do you mount the binding to a foam ski? Is there a kind of metal plate or something simular?
Buuk
A Hybrid core could be done but the same problem will occur in the foam.
The result is probably better but you have to keep in mind both parts will have quite different results under stress and what will happen on the contact surface between both?
Most of the time a small kind of aluminum alloy plate is incorporated into the foam or resin is injected into the foam near the mounting places.
Geoff
The result is probably better but you have to keep in mind both parts will have quite different results under stress and what will happen on the contact surface between both?
Most of the time a small kind of aluminum alloy plate is incorporated into the foam or resin is injected into the foam near the mounting places.
Geoff
I have built plenty of foam core longboards and I have found that as long as you use a high quality foam (pvc foam, not pu foam) the final stiffness and shape retention is fantastic. we have lost any curvature over time, plus you can pre shape the pvc foam (ie. Divinycell) with some heat. another reason to make sure that you use a good foam, not a cheaper pu foam, is that the cell strength comes from its compression strength. the compression strength on cheaper foams can become low enough to be crushed by some ski presses. high end pvc foams have compression strengths over 200psi. this is how end grain balsa becomes so impressive...it crushes at 1800psi!!!!
Airex is another example of PVC foam.
Airex is made by Baltek which is also making high quality end grain balsa.
I know Davide has been playing around with balsa. His first test wasn't very successful because the balsa wasn't very homogenic. He planned to order some at Baltek but until now I didn't get any feedback about that.
http://files.alcancomposites.com:8080/d ... _sheet.pdf
http://files.alcancomposites.com:8080/d ... _sheet.pdf
Geoff
Airex is made by Baltek which is also making high quality end grain balsa.
I know Davide has been playing around with balsa. His first test wasn't very successful because the balsa wasn't very homogenic. He planned to order some at Baltek but until now I didn't get any feedback about that.
http://files.alcancomposites.com:8080/d ... _sheet.pdf
http://files.alcancomposites.com:8080/d ... _sheet.pdf
Geoff
I use airex c 70.75 in the shovel area (first 20cm) of my current ski. It shows no signs of fatigue yet (after about 20 days hard skiing).
You can see the airex here (green part):
Airex has very small closed cells so it is not sucking a lot of epoxi.
With an airex core you definitely have to use sidewalls or alternatively a cap construction (as i do) - the foam is way to soft.
You can see the airex here (green part):
Airex has very small closed cells so it is not sucking a lot of epoxi.
With an airex core you definitely have to use sidewalls or alternatively a cap construction (as i do) - the foam is way to soft.