To vent or not to vent? I’m building epoxy/eps boards with wood veneer decks and fabric bottoms and curious to know if vents are really needed. Firewire doesnt use them, Surftechs dont use them and many others dont. Is this due to the fact that shortboards dont need them because of less eps foam used compared to the big SUP? If so, at what size is it good to start using vent plugs? Planned on making my own instead of buying the big gortex ones because they’re too big. Maybe something like pics below where i make a colored resin dam with brass threaded insert so screw is flush with board and not big and stupid looking.
How long do you want it to last? Short boards aren’t usually meant to last a long time so you dont need them. A board built to last should have one in case it sits in the sun or travels to high altitude. You have to decide. Lighter foam on the inside means more air space. 1 lb foam has alot more air than 2 lb. You learn the hard way when you open the board bag of your favorite board and suddenly it has a bubble. I have some 2.75 in. thick 7’ boards with 1 lb foam that haven’t had an issue, yet. I haven’t had any problems with the goretex vents leaking, yet.
EPS is full of both air and the closed-cell blowing gas (about 95%), doesn’t matter how tightly packed the cells are nor their size. Any gas is highly reactive to heat, so therefore any EPS will expand (and contract) with changes in temperature (or pressure). Board volume doesn’t effect the expansion, however surface area and color does if exposed to solar loading.
EPS boards with vac’d D-cell sub skins then glassed over (like Boardworks) can contain EPS core expansion to a certain extent (if the temperature doesn’t get too high or for a long time). And, some people never have any problems because they take precautions to not get their boards hot. With that said, I’ve seen major delam bubbles in both Firewire and Boardworks stuff. Some it just happened while on a roof rack, or a board was stored outside (in sun) all the time. So, vents can be viewed as insurance if you’ve never had problems, and necessities if you did. Everyone usually agrees that for hollow-core they are a necessity, but really those are only +5% more gas than EPS.
If you choose to use a vent, I would not recommend some valve or open/close set up. These will invariably leak at some point or you may forget to close the valve and put it in the water. Once you have water-logged EPS, it’s a far worst problem than what heat will do.