Quick question,I have been making my own fins and have fabricated molds for them.I put the cloth in the mold,close it,clamp it shut,then pour Polyester resin in through the top where the fin tab is(they are fcs).The fins come out great but when I clean them up and sand them little pits form from air bubbles that were in the resin.I’m mixing the resin normal(1cc of hardener per 3oz of resin) so its neither hot or cold.Does anybody have any advice on how to be rid of these pesky air bubbles?
Quick question,I have been making my own fins and have fabricated molds for them.I put the cloth in the mold,close it,clamp it shut,then pour Polyester resin in through the top where the fin tab is(they are fcs).The fins come out great but when I clean them up and sand them little pits form from air bubbles that were in the resin.I'm mixing the resin normal(1cc of hardener per 3oz of resin) so its neither hot or cold.Does anybody have any advice on how to be rid of these pesky air bubbles?
Thanks in advance!
place them in a bell jar under vacuum
infuse resin under vacuum
Use uv resin, microwave for best viscosity, and in addition only add half the hardener, put fin molds on a contunually vibrating stand with pour holes up. When you take out of mold apply uv source.
Go to a surf shop and buy a set of FCS fins
Start a thread how air bubbles are friendly and not pesky. They keep the fins light and add performance only a Ph.D. in hydrodynamics could explain
As has been said, go lighter on the catalyst: that mix was figured for thin laminations but when the stuff is thicker the heat generated by the resin going off kinda accumulates and not only makes the reaction faster but it also tends to make air bubbles trapped in there even larger, as the heated air expands. You’re probably finding that the stuff hardens pretty quick, no?
Now, if you were to cut down on the catalyst, you’d still have the air bubbles. A partial vacuum will draw them out, as has been mentioned. Doesn’t have to be a real serious vacuum pump, a small shop-vac will do just fine for producing the vacuum. Just that they’re awfully noisy.
Another thing you might try is to vibrate your mold a little, say by using an orbital sander ( not a random orbit sander, without sandpaper, just the pad on the bottom of the sander ) to jiggle the wee bubbles loose. Similar to how they vibrate concrete in forms to get air bubbles out and make sure the concrete gets into all the crevices of the form.
With both of the above approaches, it may mess with the setup you’re using to clamp the mold together. I’d keep an eye on it.
Quick question,I have been making my own fins and have fabricated molds for them.I put the cloth in the mold,close it,clamp it shut,then pour Polyester resin in through the top where the fin tab is(they are fcs).The fins come out great but when I clean them up and sand them little pits form from air bubbles that were in the resin.I’m mixing the resin normal(1cc of hardener per 3oz of resin) so its neither hot or cold.Does anybody have any advice on how to be rid of these pesky air bubbles?
Thanks in advance!
place them in a bell jar under vacuum
infuse resin under vacuum
Use uv resin, microwave for best viscosity, and in addition only add half the hardener, put fin molds on a contunually vibrating stand with pour holes up. When you take out of mold apply uv source.
Go to a surf shop and buy a set of FCS fins
Start a thread how air bubbles are friendly and not pesky. They keep the fins light and add performance only a Ph.D. in hydrodynamics could explain
I’ve thought about that also,but I’m trying to minimize the steps used for production.Thanks,I will more than likely start hotcoating them,it will probably make finish sanding easier.
The hotcoat worked good but it did add a good bit of sanding but no more than I was already having to do.I made a set using less catalyst (1/8 of a cc per oz of resin) and still had the same problem,tiny air bubbles and parts of unsaturated cloth…requiring them to need a hotcoat and they took 3 times as long to cure.I’m gonna try vacuum bagging next…do you guys think the vacuum will suck the resin out of the mold?The resin is poured into the top of the mold through the tips of 2 fcs tabs so those are the only 2 openings in the mold.
Sorry to jump in so late, but here’s another idea. When you pour the resin from the top the resin becomes aerated - little bubbles form from the splashing. you need to place the resin from the bottom . Get a squirt bottle or syringe with a thin tube that goes to the bottom of the mould. Withdraw the hose as you fill the mould.
Care should be used when mixing the resin. Fast mixing will get bubbles is the resin. Slow churning wont. Keep the stirring stick at the bottom of the bucket. Again, keep the bubbles out when mixing. The vibrating probably won’t help much, because resin is too thick. The thinner the resin the better. By thin I mean less syruppy, not thinned with acetone. Casting resin might be better, but more brittle.
Start a thread how air bubbles are friendly and not pesky. They keep the fins light and add performance only a Ph.D. in hydrodynamics could explain
Both helpful and funny! Thanks.
Golf ball dimples!!! - I will argue (and have in the past) that they may actually help on fins…
Put your mold in a vacuum, that should do the trick. Actually I would stick your cup of resin in a vacuum after mixing to suck out mixing air bubbles and then again once you have poured into the mold (may be overkill). Depending on the extent of the air bubbles you may need to repour more resin after removing air bubbles. Got any pics to share?
Try adding styrene to your resin. It will thin it out a bit and allow the bubbles to reach the surface quicker. Also you can try attaching a vacuum to the top of your mold and a resin injection point at the bottom of the mold. Then drawing the resin from the bottom of the fin to the top through a tube. Dip one end of the tube into a cup of resin and the other to your injection point.
