Ski Builders Forum

I am at the stage of my board building journey where I need to figure out how thick the sheet metal needs to be that will be used to cover the lower mold, and to sandwich my silicone heat blanket. I like to think that I am on a budget, but I don't want to skimp too much and have inferior results to any popular board builders.

I am guessing that 16 gauge (a little thinner than 1/16" inch) is the way to go. Any thoughts?

Esscher

.060" thick metal is what I used on my first press form. I screwed it down in five places along each edge, it was an inch wider overall than my heater.

I made a second press form to achieve a different camber and tip curve profile and this time used .050" thick aluminum. Saved a few bucks and found it easier to bend to match the form profile. Still using five screws along each edge to attach it to the wood below. I filed longetudinal slots for the fasteners which allows for thermal expansion of the metal. The center pair of screw holes are not slotted.

Aluminum alloy 5052-H32 is what I used for the job. It's formable but not dead soft.

If I didn't have machine shop access, I'd probably buy it on line here:
http://www.onlinemetals.com/merchant.cf ... top_cat=60

Hope this helps..

-S

Did you use the bladder to form the alum. sheet to the mold?

I use a very technical method to form my aluminum sheets... I roll them around an old one gallon paint can. Works great.

G-man

esscher wrote:Did you use the bladder to form the alum. sheet to the mold?

No. I rolled the first sheet over the edge of my work table and worked it by hand into a curve at the tips. The second time I did not pre-bend it at all. I let the fasteners hold it against the bladder. In use, the air pressure presses it perfectly tight against the bladder anyway so no need to try to pre-shape the aluminum. In fact, the reason I couldn't reuse my original piece is because it got a slight kink where the tip curve starts. I think this happened when I tried to pre-shape it. This kink transfers into the finished ski ever so slightly. Using the thinner material with no pre-bending assures this won't happen again.

-S

It seems like you could just let the bladder press the aluminum to the right shape, why doesn't this work?

you have to over bend it a little, it will relax if you simply try to press it.

my idea is that if an overbent cassette or mold lining is used, the airbag will flatten it a little, it will relax into all the gaps as its being squeezed.

an underbent sheet/sheets will have issues with pushing down into the curve as it is pinched off at the bag ends


exact is always a bonus, but i would want to err on the side of overbent a pinch. even if it makes layup/loading more difficult. Thoughts?