I’ve built boards before using epoxy and never had an issue. Decided to move over to poly for quicker turn around time and I’ve been into a few huge hiccups on my current project.
the resin doesn’t fucking cure! It kicks within 30 minutes and then stays sticky and non tunable for 2 days. This is obviously the most frustrating thing when I moved away from epoxy to speed up my build time and have ended up slowing it down 3 fold
Poly seems to not wet out anywhere near as well as epoxy, is this just a resin temperature problem?
grinding down the laps has become an absolute nightmare, I’ve been told to baste the laps (another frustrating step that doesn’t exist with epoxy) but if I’m waiting 2 days for the resin to cure then this is going to slow my process even more.
What the hell am I doing wrong? I’m ready to sell this Poly and go back to epoxy, but I want to learn
Poly Lam resin never fully sets or hardens. It stays tacky. I didn’t read anything in your post about a hotcoat. If a properly catalyzed hotcoat is applied to a lam coat; It will set hard and is then sandable. I grind laps all the time with a Die Grinder and a 50# Roloc disk before I hotcoat. . I usually get around the lap with one disk before it is too gummy. Sometimes not. I drop the disk in acetone. The resin soaks off and the disk is reusable. I don’t baste unless I am doing color and only do it to protect the color from sanding. There is no need to baste if you get the lap down hard and lightly grind… there is nothing that tricky about it. If a lam doesn’t set, it is because you didn’t use enough MEK or laminated in a room that was too cold. If you are tinting or using pigment, extra MEK . 70 degree temp is ideal. Having said all that; Epoxy is just as easy if not easier.
Editted: McDing answered most of it while I was typing.
I’ll go ahead and try to answer some of your questions until a smarter more experienced member comes along. Again I am by no means an expert, but I would consider myself proficient at this point.
As far as the resin still being tacky that is a property of polyester laminating resin. Again not a chemist, but laminating resin lacks surfacing agent or styrene and wax which prevents the surface of the resin from meeting the air. Something in air prevents the resin from fully curing. This property is desireable in laminating resin because the bond between different resin layers can bond chemically instead of mechanically making a stronger bond. Most glassers will use either gloves or wax paper on hands to hold/move/flip boards while lam resin is tacky. Gloves also prevent oils and junk from dirty hands contaminating the glass in between layers of resin. I would suggest you do some searching or googling about polyester resins types before you give up on them. Cost alone is more than enough reason for me to learn and continue using it.
As far as wetting out, I’ve always had better luck with poly over epoxy. I also live in Hawaii and the temperature is mostly warm, in the 80s F, so never had to worry about it. I would guess if you are having trouble wetting it out it is either too cool or your actual cloth. Again never had experience with it, but I know some cloths and cloth weights play nicer with resins than others.
Grinding laps isn’t that bad. I was told recently to use a vixen file, sometimes called a body file. They are usually for auto body repair, but work like a dream for laps. If it is a free lap you really only need to get it flat enough for the other side to lay nicely. Basting laps isn’t actually that bad either. It takes minutes and makes life easier when you start sanding.
What brand of polyester resin are you using? Do you know how old it is? How old is the catalyst? What method are you using to measure proportions? Is any leftover resin curing solid in your bucket? Temperature and humidity within range?
Some poly resins need to be ‘kicked’ with an accelerator chemical before mixing MEKP catalyst. If you are buying a brand name resin formulated for glassing surfboards this shouldn’t be an issue. If it’s kicking in 30 minutes then your proportions are probably OK and you shouldn’t have to add accelerator.
It may just be the usual tacky surface that allows subsequent layers to be applied without sanding. As mentioned, a sanding coat (hot coat) applied over your lamination should cure to a tack-free/sandable surface. Epoxy cures to a tack-free surface regardless but you need to sand between layers if you wait too long.
you don’t add wax in styrene in mix for sandable layer (bast lap, hotcoat, gloss coat)
i am an epoxy guy too, only use poly for easy to sand finish coat. i buy sanding resin, with wax in, when i can or i do my one mix. 1 time i think wax was in…but not, stay tacky have to coat again…
stay with epoxy, build a simple oven with bathroom fan radiator, up to 45°C, speed epoxy kick a lot give a stronger shell safer to sand and always surf a cured board. if you don’t care spider gloss when dinged you can do finish coat with poly resin, cheap, fast cured and easy to sand.
it seems that people who used to work with epoxy find it easier than poly and those that used to work with poly find it easier than poly… So both are easy to work with when they are well used.
I’m more of an epoxy guy, but have done both. You need to add wax solution to the fill-coat / hot-coat / whatever you want to call it. Do this right and it’ll sand like butter. Hard to beat the sandability of poly.
if you haven’t done so already, try UV cure poly. It makes life so easy it’s ridiculous. You can literally do a whole board in a day.
Are you using surfboard laminating resin such as Silmar? Poly should wet out cloth easier than epoxy. Ideally, using MEKP, you’re setting off your lam so that by the time you’ve got your laps tucked, the resin is kicking. Usually 7 minutes or so. Obviously, with UV cured resin, you have more work time, but faster overall kick once you expose it to UV.
Also, if you want to go back to epoxy, Resin Research’s “Kwik Kick” epoxy is great for speedy turnaround. I’ve glassed a board in one evening to deck fill coat stage, leaving bottom fill coat for morning. Cn do it all in one night if I stay up a little later.
phillipjohnw touches on what I believe to be the problem in your case. Poly resin is known as an “air inhibited” type. It will never cure totally hard unless there is an air barrier introduced. This is the function of the wax in styrene additive, aka surfacing agent. Without that barrier it will never harden completely.
Since you are new to poly and your past experience is with epoxy I think you are missing the main difference between the two. Epoxy acts the same in every step. Your lam coat has the same properties as the hot coat so sanding is less of an issue. Poly requires a different approach since it needs an additive to cure tack free. Also be aware that poly resin with the wax additive should never be over brushed. Once the wax floats to the surface if you disturb it by continued brushing you will get sticky spots that never harden. This is a common rookie mistake with poly. When doing a hot coat work fast, get it brushed out, and walk away.
problem is RR KK don’t wet out cloth easily, RR 2000 too. I have other local brand that wet out cloth realy well by soaking in fast but take a bit more time to set but i use to do filer coat on tacky lam so more or less 1 hour after i prep resin for lam. with epoxy you can do other side lam while first coat is set tacky, no lap prep needed but lap must be lam clean. With my hot box, when i am hurry, i lam and fill coat both side same day and sand next day a cured board.
