Vacuum bagging AND pressing for cap construction?

[MontuckyMadman]

Pretty sure they are using a high durometer or hard, silicon or RTV. 80 or above, if memory serves on those scales.

I have used products from smooth-on an industry leader in rtv's. I have used some other silicon and rtv that is simpler to calculate but has less flexibility in terms of initial viscosity for getting detail, It was in TX and I can't remember the name.
There are a bunch of company's they will send you samples in different durmeters and you can choose and test.

[CFO]

Thanks MontuckyMadman,

If you dont mind, I will pick you brain a little. To make a urethane mold, can I just use a laser cut template, or do I need to use a shaped ski?

[MontuckyMadman]

I worked in a metal art foundry doing sculpture molds. I also worked in the ceramic industry and used mold making there as well.

To clarify from earlier the manufacturer of the rtv was in TX not me.

Not really clear on your Q. If you want to mold something you better have a shape of exactly what you want molded. So you will want a shape of your ski cap and profile. You also may need to calculate for mold shrinkage. maybe ~1%-3% depending on your rtv mix. Silicon shrinks less in some instances- um from memory not sure

I have not made that type of molding in the ski industry but I have watched those videos and pics and it is what that looks like to me. You may want to look at aerospace and mold application there. I am just speculateing on what I see.

Epoxy like to stick to RTV even with appropriate mold release agents. You will want to look at silicon or perhaps another substance more suited for use proprietary to this industry.

Thats about all I got other than search making damn or block and pour mold t6echniques. Tap plastics is always good. Smooth on also has some tutorials. You can also do the paint on method but is harder to get even. My gues is you will want to make it as even as possible.

The way 333skis does his cap seems to be the easiest. Its just in the routing like greg was talking about.

[MontuckyMadman]

wow that's tough to understand.

I should edit tah when solber

[CFO]

Hey Madman,

Thanks for the explanation and the vid. It is actually clear enough. So I will look at silicone then. In terms of molding question, I meant that do I need to make a cambered mold, or would a flat one be good enough. In the end the press should press it to camber. I hope...

[MontuckyMadman]

basemold and/or heat make the camber. I might try badder conformation if pneumatic before making silicon molds. Or like 333 if vacuum.
good luck

[twizzstyle]

Update...

A few months ago I did some small test pieces, and they worked out great. Finally today I pressed a real ski, and it didn't turn out so good.

I'm still convinced this would work out great, you're just really relying on the vacuum bag to stay sucked down perfect the whole time. When I got the ski in the bag, it looked perfect, top sheet was nicely wrapped on the sidewalls. Got the ski in the press and let it cook at 185 deg for an hour.

When I took it out the top sheet looks awesome, no wrinkles or anything. But its not fully bonded to the sides of the ski, so there is quite a bit of fiberglass and wood exposed down most of the length of the ski. Oh well.

I'll try again on the 2nd ski for this pair, see if I can't get it a little better, but then I'll leave this idea alone. I think the next pair I'm just going to do treated wood sidewalls. I've now done two pairs with p-tex sidewalls, and one failed "cap" ski.

Some pictures...







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[nate]

At first I thought that was a really skinny snowboard.
Haha, nice work though. I like your graphics. Where'd you get them, if I might ask?

[twizzstyle]

At first I thought that was a really skinny snowboard.
Haha, nice work though. I like your graphics. Where'd you get them, if I might ask?

hahaha! Dimensions are 160cm, 150/130/140, reverse camber, and quite soft (I made the same skis last spring and they were a blast on groomed runs... haven't had them in powder yet)

I drew up the graphics in Adobe Illustrator, and had them sublimated by SnowboardMaterials.com. $42 I think for a sheet long enough for two skis, less than $20 more than if you just got a clear top sheet from them, so not too bad at all.

[KevyWevy]

are you going to inform them on why you think the topsheet didn't bond to the sides?

[twizzstyle]

Well I don't actually know, I only have guesses.

I had the vacuum hose near the tip, which got squished once it was in the press. I think there might have been a small vacuum leak and it couldn't get more vacuum with the hose clamped off.

The 2nd ski I'm going to put the vacuum hose at the center, and do one on both sides so that if the fire hose cuts off the breather from getting good vacuum, at least I'm covered on both sides. Hoping to press the 2nd ski tomorrow, will post results from that.

If the 2nd ski miraculously turns out perfect, then I'll re-do the 1st one. If it turns out the same, I'll leave them as is and ski with the exposed sides.

[ngrundl]

How did the 2nd pair turn out? I'm about to use a similar layup and am curious?

[twizzstyle]

Ha, wow that was a while ago.

The second ski turned out ok, I was able to keep the vacuum hose from getting squished and it held the whole time. If I had a cattrack back then, I wouldn't have had these problems, but I didn't back then.

So it sorta worked, but wasn't worth it, and I've done sidewalls (be it plastic or wood) ever since.

[Greg]

To wake a dead thread. Last year I worked a little more with the 'wrap cap' process and have had pretty good results.

To protect the sidewalls, I cut the bottom layer of fiberglass extra wide and during the layup process I wrapped the extra width of the bottom layer of glass around the sidewalls and pressed it onto the top. This way the same piece of fiberglass wrapped around the entire core. The tips are made of three layers of fiberglass, and I pressed in a vacuum press without a topsheet. The topsheet is just epoxy/fiberglass.

The only real issue I had was that it was difficult to keep everything lined up when I wrapped the glass around the core, so one ski is shifted a centimeter, but it still skis fine.

Last summer I pressed a teleboard using this method, but I haven't had a chance to do the cleanup work on the teleboard. Hopefully I will get a test day this year at some point.