Topsheet airbubbles underneath

Toddh77 · Post by **Toddh77** » Wed Aug 15, 2012 8:41 am

Anyone have a good cure for the bubbles that I am getting under the topsheet when I press skis ? They are small, but not nice looking. I am using clear p-tex topsheets. I thought about buying a small silicone blanket to put over top of the skis in the press to get some more pressure in the tiny voids. Any help would be appreciated.
thanks

vinman · Post by **vinman** » Wed Aug 15, 2012 8:54 am

What kind of press and how much pressure are you using?

How big are the bubbles, pin head, pea, dime, quarter, bigger?

What kind of layering do you currently use in your cassette?

twizzstyle · Post by **twizzstyle** » Wed Aug 15, 2012 9:33 am

"More pressure in the tiny voids" - what voids? You shouldn't have any voids.

Are there bubbles under the top sheet prior to sticking it in the press? You can use a hard roller of some kind to roll the air bubbles out from underneath the top sheet before sticking it in the press.

Toddh77 · Post by **Toddh77** » Wed Aug 15, 2012 9:58 am

The bubbles are small size of a dime or less. They just made the color look dull in those spots like the topsheet wasn't pressed completely to the ski. I'm pressing at 55psi in a pneumatic press with airbags, cattrack and .032 aluminum cassette. I used a roller, but the SuperSap Resin was still in a very liquid form and not very tacky.

MontuckyMadman · Post by **MontuckyMadman** » Wed Aug 15, 2012 10:52 am

so you have a graphic layer in there like fabric or wood veneer OR are you seeing the air trapped on the glass it self?
If #2 is the case, then you may have a resin poor laminate.
Try calculating you glass to resin final ratio.

vinman · Post by **vinman** » Wed Aug 15, 2012 11:18 am

My experience with supersap is that it gets very bubbly/foamy looking when mixed. If allowed to sit for a few minutes it starts to clear up.

I wonder if it is just gassing out after you apply it?

Also if your epoxy is getting foamy when you work it you are overworking it and you need to use more epoxy instead of trying to spread it too thin.

Toddh77 · Post by **Toddh77** » Thu Aug 16, 2012 1:14 am

I have paper graphics underneath. I tested it without ink as well to make sure the ink didn't have anything to do with it. After hearing your comments, I'm thinking maybe I need to use a bit more resin and work it less, the Super Sap was a bit foamy from working it in to make sure the paper was completely wet. I'll give it another go and see what happens.
thanks for all the help, and please continue to post any other ideas. If i find a solution, I'll be sure to let you know.

amidnightproject · Post by **amidnightproject** » Sat Aug 18, 2012 5:51 am

Toddh77 wrote:I have paper graphics underneath. I tested it without ink as well to make sure the ink didn't have anything to do with it. After hearing your comments, I'm thinking maybe I need to use a bit more resin and work it less, the Super Sap was a bit foamy from working it in to make sure the paper was completely wet. I'll give it another go and see what happens.
thanks for all the help, and please continue to post any other ideas. If i find a solution, I'll be sure to let you know.

How long are you letting your graphics sit after printed?

And when I was using the room cure entropy i could never get rid of all the bubbles. You can get close but it'll never completely escape.

doughboyshredder · Post by **doughboyshredder** » Sun Aug 19, 2012 6:29 pm

I have never had this problem, and I think it's due to a single step that I have always done.

I use a serrated spatula to spread the epoxy on the top sheet before applying the top sheet to the layup. I do not use any sort of a roller. My theory is that this creates an even application of epoxy, and that it allows gas to escape before that magical moment when the epoxy achieves maximum viscosity, which in a perfect world is after your press has achieved your intended pressure.

Also, is 55 psi, what you are seeing at the laminate, or what your bags are reading?

Depending on your setup 55 psi at your bladder could be as low as 20 at your laminate, which, of course, is really low.

Toddh77 · Post by **Toddh77** » Tue Aug 21, 2012 12:07 am

55 psi is what my gauge reads on my compressor leading to the bags. Not sure how to measure the pressure to the laminate. I will definitely try more pressure as well as the technique using the serrated spatula.
thanks for the ideas.
I'll probably give it another go next week and post the results.

doughboyshredder · Post by **doughboyshredder** » Tue Aug 21, 2012 9:43 am

Toddh77 wrote:55 psi is what my gauge reads on my compressor leading to the bags. Not sure how to measure the pressure to the laminate. I will definitely try more pressure as well as the technique using the serrated spatula.
thanks for the ideas.
I'll probably give it another go next week and post the results.

Figure the square inches of your laminate.
Figure the square inches of your bladder that is actually making contact with the cat track when fully inflated.
If you have 100 square inches of bladder contact that is 5,000-6,000 lbs of pressure. Divide that by the square inches of your laminate. The resulting figure is your psi at the laminate. Pressing at 50 psi, if your laminate has less surface area than your bladder the pressure at the laminate is higher than 50psi, if it has more surface area than your bladder the pressure at the laminate is lower.

A lot of presses have a significantly lower psi at the laminate than in the hose.

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Topsheet airbubbles underneath

Topsheet airbubbles underneath