I have been glassing a board with Resin Research Kwik Kick epoxy. I have done the finboxes, deck and bottom lams, and they have all turned out fine. I have been using a 2:1 ratio using pumps on the containers and doing 2:1 pumps. My problem is that I must have screwed up the ratios on the deck hotcoat somehow. It took way too long to kick, and then was very tacky for a while, and now (this is a few days later) the resin is still slightly tacky. Not so much where I can’t handle it or flip it, but soft, so a fingernail leaves a mark in it.
So my question is: will this eventually harden, especially if I bake it in the shop with heaters on, or would it be better to try to sand the resin down to glass and re-hotcoat? My concern with the latter is that I’ll inevitably hit the weave and weaken the board, not to mention the sanding discs I think I’ll go through sanding slightly soft epoxy off of a board.
Thanks in advance. I appreciate any help anyone can give.
If it's been a few days and it isn't hard, it's likely done it's thing as far as curing. I'd say your ratios were off a bit.
Epoxy proportions are critical to successful cure. I don't trust the pumps. There are calibrated mixing cups that some guys use but the most accurate way is with a scale. Weigh it by the gram and follow the manufacturer's ratios for weight, not volume.
For your present problem, I would suggest that you go ahead and sacrifice a few sanding discs, grind it smooth with a coarse (60-80 grit) disc and recoat with a properly proportioned mix. It might add a little extra weight but with two fillcoats you can skip the gloss coat. Just wet/dry the second fillcoat to 1200 and buff if you want it shiny. Wet/dry to 600 or so if you want a sanded finish.
It may not have optimum strength properties or be the ideal bonding set-up but with a coarse prep grind, you should be OK.
Yeah, I was afraid that was going to be the case. Oh well, lesson learned: I don’t trust the pumps now either. The weird thing is it worked fine for the first couple of times. Who knows, maybe I didn’t push one of the pumps all the way down or something. If I had to guess, user error is more than likely the case.
I appreciate the advice. Thanks for responding so quickly.
@ S.F. If it’s not tacky but soft to finger nail pressure, try elevated heat in your shop, or a makeshift post cure box that should finish the cure for you.
I’d try warming it up for a while before I started sanding it all off. Dont go over 120F. to be safe though.
Edit: Post curing the board will strengthen the laminate under your messed up hotcoat anyway, so it’s worth the effort . It might also fix the problem…
Yeah, I thought of that, but I’m about 99.9% sure I pumped the right amount out of the right container. Maybe I’ll try to heat it tonight for a bit before I start to sand it off this weekend, especially since, like you said, it will strengthen the laminate, so it’s not like it’ll be a complete waste of electricity and time. I’ll post back here with results in a couple days. Thanks again.
Hot coats aren’t all they’re cracked up to be anyway. If anything, hotcoating is one of the true remnants of the "40 yr. cocoon " mentioned here and elsewhere. The wasted effort , materials and excess weight required for hot and gloss coats are definitely 50’s to 60’s technology. Imho.
99% of the current fiberglass based boat manufacturers spray the “gell coat / hotcoat / gloss coat” into a mold prior to skin / core molding.
Typical surfboard hot coating is the equivilent of using drywall fairing spackle on the drywall in your house. Slap it on, and sand most of it off. Again, just mho.
Btw. I once potted some finboxes in with a very slow hardener combined with colder winter shop temps.
I freaked the next morning when the resin and fiberglass sticking out of the box holes was quite rubbery to say the least…
I thought I’d have to route out the boxes and start all over. Turns out it was just the fact that I used my slow hardener in colder than normal shop conditions.
I heated the room up to arround 85F. and also carefully heated the box area with a hairdryer and the next day the epoxy was rock solid.
If you mixed it right, it has to cure. Sometimes weird shit happens.
I use graduated mixing cups from automotive paint stores and a scale.
When I pour my resin and hardener I watch both the scale and the cup to
make sure my math isn’t off. scales are great for measuring tiny batches
of resin also,use the little medicine cups and a popsicle stick. With
RR you take the total amount of resin and divide it by 3.22 and this
tells you how much hardener to use.Pour the hardener into the cup, then top off with the original amount of resin.
Just get a scale, $20 at harbor freight http://www.harborfreight.com/digital-scale-95364.html. Get some calculators at the dollar store (the keys will eventually get glued down). Zero the container, multiply the resin weight by .45 and add this number to the original resin weight. With the container still on the scale, pour in the hardener until you hit the total number. Don’t forget to mix well; 99% of the problems with incomplete curing is incomplete mixing.
Hi pete,I have that scale and it does not measure in 0.grams to weigh epoxy properly. Was wondering if you have used that scale with success and maybe I’m doing something wrong? It works great for weighing shortboards though.
Also know your scales max,nothing worse than pouring resin into the bucket and your scale tops out and goes blank,thats the reason to use graduated cups and know your marks then you can still get it close enough in case of electronic failure.
Been using that HF scale for a couple of years with no problems. It will handle 11 lbs, and I haven’t had an accuracy problem with it. I periodically check it with calibrated weights and test to 6 lbs. Viscosity changes drastically with temp (that’s why you microwave it) and the volume will be somewhat effected. The weight will never change regardless of viscosity. Even if you recycle the measuring cups, you’ll spend as much on these as the scale costs so why not just do it right.
I used a scale for years, now I use the PPG cups from auto paint stores. Mixing resin is by volume not weight....But epoxy resin a and b parts are different weights. So using a auto paint cup gives you and exact 2 to 1 mix ratio. No more of this 55 to 45% ratios etc. You just pour to the lines on the cup.
And I haven't had is screw up yet.....epoxy always kicks off.
So, after the board sat for about four days in 75-80 degree temps, then it baked for about a total of six hours at ~100 degrees, with no change in the hardness (I could still indent it with my fingernail), I decided to sand it off. I sanded pretty far down, enough to get it thin and expose weave in a number of places, but not much more than that, because I didn’t want to weaken the cloth. After I did that, I cleaned the board with denatured alcohol, and did another hotcoat on it, using a scale and using the .45 method recommended above, with the following results:
After I did the final brushing, it started to develop ripples in it, and then as it hardened, it looked like this, ripples with little scale-like things all over. After I did this, I did the hotcoat on the bottom in the same exact way (cleaned with denatured alcohol, weighed on scale, stir for just as long, etc.), in the same exact conditions (same temps, same humidity, etc.) except for in the deck hotcoat (the one that rippled) I put about a capful of Additive F. The bottom hotcoat came out perfect (as perfect I’m gonna get it at this stage). Could the Add. F have caused the ripples? Does anyone know what happened? As it is, I’m probably going to have to sand the rippley coat off and do another hotcoat, and since the bottom came out nice I’m not really worried, I’d just like to know if anyone has every experienced the above.
I never wipe my boards down with anything between glassing/finish coat stages. After sanding I blow the dust off with filtered compressed air and use an automotive tack cloth if needed. Too much additive F can cause a bit of an F in a finish coat. Follow the instructions,1-2 cc per ounce of resin I think is close enough. Epoxy finish coats always seem to have some sort of drama your not alone.
