Ski Builders Forum

What are you doing with the squeezed epoxy during pressing?
Do you remove it immediately or you wait for it to cure completely?

It makes big mess around...

I line my cassette with baking paper that is a little bit wider than the cassette and I fold the edges up so it catches all the epoxy that squeezes out.

I lay a big plastic drop cloth thing under the mold, then once everything is in the press I pull the sides up over the press so it catches the epoxy. Over time you'll figure out how much epoxy you really need so you won't have quite so much squeeze out.

are you guys using squeegees?

I have been typically using a roller. my lady and i built a pygmy boat (mostly her), and pygmy always recommended using a squeegee and getting the fiberglass wetted out and then throwing away the extra resin. but this was just a wet layup without any pressure from a vacuum bag or anything.

i was figuring that the pressure of the ski-press really squeezes the extra epoxy out and the resin to fiber ratio is really dependent on the pressure of the press.

if you have too high of a pressure like 100 psi then you could have a resin poor ratio, and if you have too low of a pressure then the skis would have extra resin and be heavier.

should i be using a squeegee to instead?

Balkan,
I'm not clear how much 'flow' you are getting, but if it is hitting the floor, then that's too much ...

Do you have a defined resin ratio? Calculate this and you will then be able to quantify whether this is natural loss or not.

http://www.netcomposites.com/calculator ... -fractions

Too much resin not only leads to waste - and less money for beer, but it means your fabric is free to float about in the resin leading to poor alignment. When you do define your resin ratio, remember to include an element of waste (tooling) and saturation into the core.

If its not simply a matter of too much resin, then viscosity, pressure and ramp (temperature increase per unit time) are all factors.

If viscosity is too low, you will end up with a resin starved fabric, so the laminate will be weak - evident over time ) If the resin is marginally too low, then you will need to speak to your supplier about whether you can apply the pressure in two phases, increasing the pressure just before the epoxy begins to gel. The nature of epoxy is such that this is a critical moment within the press, so it not an ideal approach.

Pete,
letting the press define the resin ratio is not ideal. Too much resin in the press and the fabric is free to float around, mis-align and crimp. Increasing pressure reduces the void content ... so if you have a big I-beam press and it is bolted and welded together and the viscosity of your resin can take it, happy days, you've reduced your void content by 1 or 2 percent. When applying the epoxy to the fabric, it is more about ensuring that you deliver a consistent amount of resin down the length of the fabric. So a paper cup with a lid and a hole is an improvement on just a cup. If you can quickly spread two or three lines of epoxy onto the fabric and quickly spread them out using a piece of base material or a roller - happy days. If you can limit your tooling of the fabric to a minimum, then all the better.

Thanks for the detail answers, guys.

Richuk, the resin is not hitting the floor. Actually, there is very small amount, squeezing out of the cassette, but it is liquid and it is flowing into the mold.

We use entropy resin. When we press a board, first we hit the pressure up to 4 bars and then we ramp the temp up to 90 C degrees.

When the temp raises about 70, the resin becomes more liquid and small amount is going out of the press.

May be, the resin was too much.. Next time, we will use a bit less.