Well, I’ve had some downtime in the progress of my board. Because of the trade show Rainbow is a bit delayed shipping me my Lokbox jig (non-vacuum model), something about a new design or model thats available after the show. I hope its worth waiting for…any opinion on that JJR? Anyway, its allowed me time to second guess my current glassing schedule.
I’m shaping a 5’10" fish, 2lb Marko EPS, RR Epoxy tint/swirl bottom and clear deck, and currently 6 oz bottom 6+6 oz deck. The laminate is done and ready for fin boxes and hotcoat. If I push on the deck with my thumb it feels somewhat soft still. It doesnt permanently leave a dent, but it feels softer then my PU boards I have albeit not by much.
I’m not overly concerned about weight, so should I put a 6 oz deck patch on it just for my piece of mind? Is it nessesary or will my current 6+6 be fine? Also, for the fin boxes, are the football patches ok or is it recommended to do an entire tail patch?
the epoxy has probably not yet reached its complete stiffness. Most epoxies available through retail will reach their full strength for up to a week. Most 2/1’s get to 90% in 3 days or so. So dont judge it until its been a few days.
Epoxy has a much longer elongation vs. Polyester. Some epoxies are more high performance than others and can be post cured (heated up) for more stiffness and better technical performance (higher heat deflection, higher tensile strength, etc…)
I have a similar board, double 6 on the deck over eps. The thing is really strong now, It did take about a week for full strength to be reached. I would wait to see how it turns out.
I’m just second guessing myself because I have all this extra time now. If the jig was in it would already be done and I would be surfing on it now. I think I’m just going to leave it be. I’m a lightweight myself at only 155lbs so it should be good. Its my first board and it might not surf like I am hoping it will. I just wanted to make sure a 6+6 wasn’t too lightweight. Thanks.
My recommended glassing schedule for 2 lb EPS is 6/4 bottom. 6/6 top with a 4 oz tail stomp. The bord is still really light & it’s really strong.
6/6 top with a 6 oz bottom will buckle in heavier waves. Plus it will skelator out around the stringer & fin boxes from all the foot stomping.
You also need to let the Epoxy cure out, either bake it in your car at 120 degrees all day,…don’t let it get hotter than that, or let it sit for 4-6 weeks in the garage.
Buckling is the result of shear failure between the lamination and the immediately underlying foam. More glass won’t change the shear strength of EPS, though it will make a stiffer board, and a stiffer board may resist shear a little better… maybe your response has merit but not for the reason you thought. And it still doesn’t address the weakness of EPS in shear.
The classic example of shear: bend a deck of cards and note that each card slides against the next. That’s shear, and the greatest shear happens at the “deck” and “bottom” cards. If one could devise a simple way to increase shear strength between the lam and immediately underlying foam, you’d really have a board that would be very resistant to buckling.
This has been discussed before, though no great noise has been made about it. I suspect that BB and Thrailkill have made some contributions to the shear failure situation, in line with the above.
All shapers/glassers need to get their minds around a few materials mechanics concepts. Shear is just about the first of those concepts. It is old mush to simply “throw more glass on it” though that may crudely achieve some positive result.
As long as you measured the resin and hardener accurately, you’ll be OK with your glass sched. I’ve had that happen to be before… where it seemed to just not get hard. Turns out when I got to the bottom of the jugs of resin and hardener, I had some hardener left… somehow, I screwed up the measurement. And another layer of glass really did not help. About 6 weeks later, it was harder, but still not has hard as it should be.