I'm just making up my ply fins for my first board, so far I've just sealed them with lam resin to make sure I don't get bubbles under the cloth later. I covered the fins with aluminium foil after sealing them so no dust would settle on them before I get on to glassing them, and the resin has lost it's tackiness from the aluminium foil being in contact with them.
Does the resin need to be tacky to bond with the laminating resin that goes on next, is the bond better if it is tacky? If so, will wiping them down with acetone restore the tackiness?
Yes, it’s UV resin, with a bit of MEKP to make sure the stuff that soaked into the wood went off. It’s just lam resin, no wax, just the spots where the foil lay on the fin went smooth and non tacky. As I understand it, the foil has blocked air from reaching the resin, and so done what the wax usually would.
Next time use wax paper instead of foil. It's cheaper and the wax is the sealer the same as a hot coat. Use wax paper on all ding repairs also. Will help greatly with sanding.
OK, thanks for that. I’ll use wax paper from now on, but my lam resin is still going to go non tacky from being in contact with that, right? So I’ll have to sand/styrene after putting the halo in, and again after laminating one of the sides? Part of the fin is always going to be laying down on something.
I’m a little confused with the styrene bit; it’s the stuff added to lam resin to make it sanding resin, no? By applying a little it makes the resin good to go again, or easier to sand?
You don't need styrene if there is no weave showing. When you have sand throughs, the fiber is exposed so it needs to be wetted out to seal. For lack of a better description, the styrene "fluffs" up the fibers to let it absorb resin. When doing this you need to get resin on it immediately. Flush with a very small amount of styrene on the exposed weave and right away wet out and smooth the resin again.Use your finger or spreader/squegee depending the size of the sand through.
Styrene coupled with wax make up your hot coat.
If the resin dries hard just scuff it up again before re-coating. This gives the new coat something to "key" into on the previous surface.
Usually, if you are making wood core fins you encase the wood core in a "block" of glass and resin. This kicks off and then you cut out the profile and grind to the right foil. Your layers/plys are the guide to sanding and maintaining symmetry.
OK, thanks tblank, I’ve got my fins foiled out of ply. Just decided to seal them before glassing, but there’s no glass on them yet. I’m going to be following, more or less, Bert Burger’s method for making fins and just want to make sure the laminate that’s going on next sticks well. Thanks for your help.
Thanks for all the help, ended up sanding and wiping down with acetone, the only styrene I could find locally seemed pricey so I didn’t get it. The fins are pretty much done now apart prom cleaning up the hotcoat. 10" base 5.25" tall.