Weird organic base depressions

grace ski · Post by **grace ski** » Fri Jan 13, 2012 2:57 pm

http://weskigrace.blogspot.com/2012/01/ ... -back.html

Not sure how to post pics but I have one in the above blog..

We have a weird organic crater like thing happening. Has anyone seen or experienced this? Doesn't happen every time or consistently. As you can see in the picture one ski came out fine.

Our cassettes are clean, smooth etc. bases are clean before pressing, so it isn't debris.

We figure epoxy cured in the first layer during layup?? bad epoxy mixture??
Our press is heated to 90F so it usually sits around 104-120F as it adjusts etc

if you have seen this let us know...
Thanks in advance [/url]

MontuckyMadman · Post by **MontuckyMadman** » Fri Jan 13, 2012 3:02 pm

your gonna get a better ski if you cook your shit hotter with an epoxy that can do it.

grace ski · Post by **grace ski** » Fri Jan 13, 2012 3:12 pm

Just tested the heat last week. Plan on going much hotter.. MAS EPOXY is what we use.

Richuk · Post by **Richuk** » Fri Jan 13, 2012 3:26 pm

I think we have seen this on the forum before - as a result of over-heating, so its worth checking the heat map being created when you are pressing.

Both skis suggest you have an excess of epoxy leaking onto your base? Just the picture perhaps? It's worth considering how you shape your core and to what tolerance.

grace ski · Post by **grace ski** » Fri Jan 13, 2012 3:39 pm

We have very little epoxy leaking during press. i was thinking we didnt use enough? for a 186 ski we use approx 100 grams/50grams. 150 total of epoxy resin mix 2:1. per ski in each layer.

never had the problem till we heated and used fast curing resin...

Richuk · Post by **Richuk** » Fri Jan 13, 2012 3:57 pm

Do the photo's show epoxy on the base?

I've read that if epoxy over-heats, it will produce gas. So ... I'm thinking you're overheating the epoxy and perhaps, if there is epoxy on the base and the core isn't super flat, the epoxy exploits these nominal pressure voids.

grace ski · Post by **grace ski** » Fri Jan 13, 2012 4:34 pm

No epoxy is never on the base, the cassettes are clean when the skis come out. A bit flows out during press but never gets under the base. The cores are flat. Very tight tolerance. It must be a resin temperature issue. I am going to press the next ski with no heat.. See if it happens

twizzstyle · Post by **twizzstyle** » Fri Jan 13, 2012 5:52 pm

Wow that looks crazy. You're not using anything weird in your cores are you? Foam or anything like that that could be melting?

I say cut one of these skis open and figure out what's going on inside.

What pressure are you pressing at?

strangesnowboarding · Post by **strangesnowboarding** » Fri Jan 13, 2012 8:20 pm

i have gotten bubbles like this only with a lack of pressure.
related mostly to the size of the cavity that the firehose has to fill, if the cavity is too large or too small then the pressure gets funky and we begin to see bubbles in the base.
we always heat to over 80C for resin flow, i dont think that that is too hot to turn into a gas and create bubbles.
i generally pull out one effed up snowboard for every 3-4 mold/size changes due to not properly checking distances within the press cavity. sucks for me but i have been getting better at understanding how pressure works inside a curved press.

another possibility is that the two skis were not quite the same thickness (core probably) and thus the cattrack only pressed one ski flat and the the other as left with not enough pressure to flatten the base.
in this case the heat from the pressing would cause the base to ripple within the void of the press and create those organic shapes you see.

grind it down! haha, i have ridden on a base as bad as that, jsut throw in some ptex and call it a day!

good luck!
tom

grace ski · Post by **grace ski** » Fri Jan 13, 2012 10:59 pm

We pressed at 42-45 psi. 120f max temp. Cores were the same as we cnc them at the same time. Cat track didn't appear to be off or not flat. The mold is getting beat up this could be the issue. We are making new camber molds next week out of luster board. Should be an improvement over mdf. Especially with an adjustable mold. The blistering or depressions are only in the middle of one ski, tip and tails are perfect.

Answer:
Build new mold, increase pressure, increase epoxy, heat to epoxy specs...
None of this happened before heat was introduced to the equation....

Richuk · Post by **Richuk** » Sat Jan 14, 2012 4:14 am

My thought on excessive gas emission (not turning epoxy into a gas) from curing epoxy doesn't fly - there is no epoxy on the base.

If you are working with trashed cassettes ... increase the thickness of the cassette. I'm using 3mm - it will reduce the stress on the mold. I'm not sure how increased epoxy is going to help with the issue you are having - it's not a filler.

Strange, I don't understand 80 degrees for resin flow? What temp does your epoxy gel at?

Brazen · Post by **Brazen** » Sat Jan 14, 2012 9:43 am

It looks to me like you are WAY overheating the materials. Check your TC.

COsurfer · Post by **COsurfer** » Sun Jan 15, 2012 11:08 am

IMO its lack of uniform pressure. I have the same problem at the tips and tail. Without full uniform pressure applied to the entire ski you get hot air voids that bubble up and then shrink to an indent. Its not necessarily about increasing your pressure but making sure your ski is getting pressed uniformly. I press at 80 PSI and still get voids occasionally.

jellyfish · Post by **jellyfish** » Sun Jan 15, 2012 12:03 pm

You are using mass epoxy with a fast hardener and then putting it in a hot press, I'd say you boiled it off it's gone crystallized and gassed off ,cut it open and see, I would press cold the only add heat after its gelled to finish the cure and reduce the press time,these marine resins work at room temps by elevating the temps you are exceeding its range.
Why one and not the other? it happens fast when it goes it could be how you did your layup and what order it was done in.

Cheers
Jim

grace ski · Post by **grace ski** » Sun Jan 15, 2012 1:01 pm

here is the plan..

Our MDF mold is getting worked so, build a new mold out of lusterboard, increase pressure, decrease heat.

We checked the TC and it is reliable. We had it in the cat track. it never read higher then 125F. That being said the bottom of the ski was much higher. We will have the TC on the cassette instead to get a more accurate
reading and cut off the heat sooner. We have a call into MAS epoxy and they will set us straight with the cure times and heat etc.

We never had the issue untill we introduced heat...

Thanks all.

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Weird organic base depressions

Weird organic base depressions