Ski Builders Forum

I have had a few customers bring up the problem of bubbles under clear top materials. We do not build boards, so we cannot give good advice on this.

Hopefully this will start a discussion that will help anyone that has run into this problem.

Thanks to all that reply. I will direct my customers looking for suggestions to this thread.

ive never made a board before either, but in my research it seems to be that everyone uses a hard roller to work the air out. an idea i had was that you could roll the topsheet out on the board/ski rather than placing it flat(roll it out like a sleeping bag) and use the roller to push air out as you go rather than dealing with all the air at once

Poor resin from an elevated position to deliver a thin stream free of air. Use a batch of resin just for the topsheet.
dbs says use a toothed scraper to lay down thin lines after substrate has been thoughely coated which alows air to escape with pressing. A j roller to try and sqeegee it out helps. Vacuume may always have this problem.

We are one of the companies Vince is referring to who can't get all the bubbles out. We have tried everything. Rollers don't work because the top sheet lifts in certain spots. We have loaded it with resin and then rolled the top sheet over. We have poured the resin down the middle. We have let the resin sit for 15 minutes prior to pouring. We have tried to warm the resin first. We have tried to press first than turn on heat. For reference we are trying to put the 8210 over wood veneer. We are so close and only get a few 3mm sized bubbles. I wonder if the heat is creating gas that is getting trapped and solidified. We use Entropy which has a set time of 20-30 minutes under heat. Due to product delivery deadlines I had to give up until I have more time to experiment. With Skis it is much easier because you have less of an area to squeeze bubbles from. I know it is possible because Arbor does it unless they are using a different top sheet product or press style.

From a vacuum perspective adding a lot more resin helps.
Try buttering your top sheet before putting in on.
Also rolling your top sheet up backwards so it lays flatter helps.
I use a J roller after I pull vacuum to push out the bubbles, this sometimes backfires as I'll push up a pile of resin that I don't see until I take it out of the bag. (getting better at watching for this)
I think buttering your topsheet is probably your best bet with a pneumatic press.

I've had some pretty ugly skis from air bubbles and it's something I struggle with every time. thought it was just a vacuum problem but I guess not.

Hope this helps!

sam

Arbor has a whole vid about the topsheet they use, it a specially made laminate structure wood composite, not really wood but a wood product.
We do a prefinish technic to our veneers prior to the addition of the 8210.
we make skis but we do not get bubbles like that.
Perhaps you are not evacuating enough resin prior to cure?
perhaps you have small pressure voids between bladders or cattrack?
denty cassetts?
have you tried a veil between you cassetts like rubber or somthin?
Have you calculated you composite to resin finished content at all?
try the serated scraper like dbs touts?

Perhaps you are not evacuating enough resin prior to cure?

We have tried running thin and running thick, same problems. We have tried squeegees, rollers, pouring thick down the middle same problems.

perhaps you have small pressure voids between bladders or cattrack? denty cassetts?

We tried using brand new cassetts, no help.

have you tried a veil between you cassetts like rubber or somthin?

Not yet, good idea.

Have you calculated you composite to resin finished content at all?

We have experimented with numerous resin quantities and all produce same small bubble issue

try the serated scraper like dbs touts?

Need to test this out.

Anyone out there who builds snowboards that doesn't have this problem let me know. I have a feeling we are going to have to come up with a method of applying and curing the 8210 pre-layup or post layup. to solve this problem. If the Elan factory (aka arbor) can't make it work in the layup we wont be able to.

I have done this layup and had the same issues described above. What works for me is using a composite veneer (bamboo is a common one). If your veneer is wavy, it will lift the top sheet prior to pressing exposing air between the clear and veneer regardless of what you try. You'd think the press would force the air out, but it doesn't. Increased pressure makes it worse, using a J roller makes it worse. I even tried pressing the veneers beforehand to flatten them, didn't work. I think one of the biggest issues with veneers is they are not a consistent thickness. The burls, knots, and grain all react differently when they are cut and there are minute differences in thickness that allow for a place for air to settle.
The composite veneer is flat and I butter the backside of the veneer, flip it in the layup and add more resin. This way the resin can saturate through the veneer. I then pour a heavy flow of resin down the center before laying the topsheet. Do not squeegee. Put in the press and apply pressure slowly. This gives the air a chance to be pushed outward without getting trapped from the heavy pour of resin down the center.
This method only works for me with composite veneers. Check Certainly Wood. They have a few.
I can envision a rubber or silicone layer helping if one were to put it on top of the clear in the layup. You'd obviously need a mold relaese on this and the aluminum cassette on top of the rubber. The rubber would form into the pockets and remove air, but the downside is the topsheet is not perfectly flat and the top cassette would be ruined on every pair due to it flexing over the sides. Adds a lot of cost.
Im glad Vince started this thread. I have spend a lot of time and money through trial and error before settling in with composites.

If it's off gassing from the wood what about curing a thin skim coat on your veneer before layup?
This would stop the bubbles from migrating to your top sheet.

sam

Perhaps its that we come up to pressure slowly and temp slowly as well. Increasing the release time of air.
No one got my one fixit hint.
Oh well.
Good luck.

I saw it

Would a light seal coat of epoxy on the top of the core before layup do much??

Is it anything to do with the way the triax we use is oriented. My triax has quite large bundles of longitudinal fibres and I always have these facing away from the core. Effectively there ends up being furrows running lengthwise that may act as a place that air gets trapped in (?). This would be more a problem for clear topsheet over the glass layer rather than over the wood veneer layer though.

Those furrows will show through on veneer sometimes

I am using 8210 on snowboards. I have just pressed 2 with no bubbles. Im a rookie, so I consider myself lucky. I have not tryed ontop of veneer, but this is probably an issue with flat to flat suface. nowhere for the air to escape. If it was me, and thats not saying much with my amount of expierience, I would use doughboys type of serated scraper. I would then do a super thin skimcoat ontop of the veneer prior to layup with horizontal strokes across the board veneer. when the resin cures you would hopfully have abunch of lines for air to escape. then in the layup coat the underside of the 8210 and put it down on the venner. this might work, but with the precured skimcoat, it will add some wieght.