UV cure not curing

General Discussion
1

First time build … i got some UV cure resin from a local pro shaper and ding repairer that he swears by, not sure exactly what brand … I laminated the bottom deck on the weekend, no pigment, stuck it in the sun and expected it to go pretty hard in minutes from everything i have read. It took an hour to go even touch dry.

Well its a few days later and its hard but still just a little tacky in parts - such that i get gummy bits on the sandpaper. Its winter here but still fairly sunny, after a couple of hours outside under weak full sun and partly cloud i thought it would be fully baked.

No-one else seems to have this problem that i can see. Maybe I got the bottom of the barrell that hadnt been stirred properly or something …

I have left it out again today and I expect today or tomorrow it will be hard enough to finish sanding.

3 questions:
(1) Any ideas what went wrong?
(2) To recover from this i just keep sunning it til it gets hard enough?
(3) For the next lam and hotcoat, after reading some posts by kokua and others (howzit btw) i will add some MEKP as well … do u recommend 0.5% and sun?

Thanks!

2

If you used laminating resin it will remain sticky to some extent, UV cure or not. Lam resin always gums up sandpaper.

“Sanding resin” is called by that name for a reason.

 

3

Sounds like you used the correct resin to laminate the board. As Sammy insinuated, you need sanding resin for the hotcoat. Or, mix your own sanding resin by adding surfacing agent to your laminating resin. Add some catalyst in the sanding resin even if it is sun cure(learned from kokua I believe). Mike

4

Thanks rooster and sammy, appreciate your help.

I’m still in 2 minds about whether the UV cure behaviour was normal or not … I’ve done ding repairs before with mekp and without SA and never had it anywhere near this tacky, where if i press my finger against it for a few seconds it grabs on. Board had spent several hours in the sun, its done several more today and now seems sandable. I defer to your experience tho.

Thanks for your advice and I’ll go with the mekp as well - belt and braces. I’ll do 0.5% for the deck lam unless you want to advise me differently, and maybe same or 1% for hotcoat. Cheers

5

I recently used FGH UV Cure Epoxy and it cured in 10-20 minutes. This was in Southern California in early June, so the UV rays on the board were pretty strong. Where in the world are you and what season is it? I know very little about how UV Cure actually works, but it’s an interesting thing to speculate on. Lots of factors can effect the strength of UV rays: http://www.epa.gov/sunwise/doc/uvradiation.html

Also, when I say it “cured”, it was still a bit tacky. I wasn’t concerned about setting it back on the shaping stand, but I certainly wouldn’t’ve risked hitting it with sandpaper. I put Polyester sanding resin over that as my hot coat and then sanded that instead. Seemed to work out ok, but it was my first board, so what do I know? :slight_smile:

 

6

Use UV cure FGH lam for everything.

Warm days the flourescent lights seem to semi kick it

Cooler days a drop or two of MEKP.

In both instances out in the sun @ 5 min a side.

and wait a day or two to grind laps and hot coat.

In your case knock the bumps off and hot coat.

Very hard to say what happened.

Old resin?

Mix up.

Don’t give up on UV

After hot coat out in the sun again.

Bake, rotate.

you’ll find that it helps in cure up time.

 

7

Have to give it a good mix.  I found that out the hard way when a lam just didnt want to kick.  mixed it up and the other side kicked in minutes in the sun.