Ski Builders Forum

Has anyone used, either successfully or with a catastrophic failure, plastic as the top surface of their mold?

I designing a new mold, as I want some adjustment, and the thin aluminum flashing I used last time didn't cut it. I'm still trying to source aluminum sheeting, but I think the plastic will be around half the price.

I used a 1/8" sheet of UHMW plastic on top (bought from TAP plastics). It makes a very smooth surface and epoxy does not stick to it. It does deform with heat.

-kelvin

Thanks Kelvin.

I must have read your mind, because i was planning on buying a sheet of 1/8" UHMW. From Mcmaster though.

Just got our first ski out using a stainless steel topsheet which we spray with mold release prior to use.

SS is cheaper than Aluminium, but doesn't deform with heat like the plastics...

I would recommend it.

B.

Bambi, Just curious what grade and thickness of stainless did you go with. Trying to make this decision as well.

Not too sure of the exact grade - it was about 0.5mm thick and it was a spring stainless steel. I used it for the top and bottom sheet as I run my press quite hot 100deg C and didn't think that plastic would last.

It worked really well for me - I used no tape on the bottom of my ski, no plastic to wrap everything and just let the epoxy dribble out sideways onto the steel.

Cleanup was easy with a soft scraper to chip the epoxy off the steel because the mold release prevented a proper bond. Mold release from the bottom sheet seemed to prevent any epoxy binding to the bottom of the ski.

B.

Bambi,

Was it a brushed or polished finish on the stainless?

Polished.

When I get home from work tonight I will see if I can dig out the invoice with the exact specs.

Be warned that it was a nightmare to bend / cut the steel to shape!

My master plan was to make a 'casette' with 2 removable sheets so that I could lay up flat before loading into the press, but in the event I decided that for the first time round I would stick with the bottom sheet fixed in order to minimize alignment problems...

B.

Actually I had it on email:

Spring Tempered Type 301 Stainless Steel Coil
0.031" Thick
10" Width
8’ Length

McMaster ref: 90415K58

You could probably go thinner if you wanted, but certainly no thicker - at this thickness you ensure a nice flat surface because the camber in the ski prevents any bending in the metal across the ski width as there is no way the metal is going to allow a 3D bend at this thickness.

B.

Sweet, Thanks Bambi.

Bambi wrote:Actually I had it on email:

Spring Tempered Type 301 Stainless Steel Coil
0.031" Thick
10" Width
8’ Length

McMaster ref: 90415K58

You could probably go thinner if you wanted, but certainly no thicker - at this thickness you ensure a nice flat surface because the camber in the ski prevents any bending in the metal across the ski width as there is no way the metal is going to allow a 3D bend at this thickness.

B.

Holy crap! $118.

This is some comparable aluminum: "8973K13
Alloy 3003 Aluminum Sheet .032" Thick, 36" X 96"
In stock at $74.16 Each"

Here is what i am really liking at the moment.

"8752K151
UHMW Polyethylene Sheet 1/8" Thick, 24" X 96"
In stock at $56.22 Each"


I probably won't have money for a heat blanket anytime soon, or a press for that matter, so this ought to do the trick at a decent price. Now if i can just find some locally, or in a 6' length that can be UPS'd.

krp8128 wrote: This is some comparable aluminum: "8973K13
Alloy 3003 Aluminum Sheet .032" Thick, 36" X 96"
In stock at $74.16 Each"

That's a good deal - I don't think that I saw that, but if you want the thing to stay flat after a pressing then the steel is a better bet I think...

B.

Check out steel shim stock at your local industrial supplier. I have used some in the layup. Comes in sizes from .001 and up to I am not sure, but I think around .020. Can also be used for filling in the trough between the edge tabs, and under foot for binding screw retention. I have .008. .011, and .015. Comes in 100inch rolls between 6-10 inch widths Under 10.00$ a roll. Cheap