We’ve built about 30 boards and only two have been “oops” we forgot to tighten the vent plug. What a mess to fix, thanks to good waterproof glues, the boards comeback to about 97% original shape. We’re thinking about using surbject venting but seems all vent sells say to use two. Question: are there HWS builders who use two or is one sufficent? Also what kind of replacemtn life does the membrain have?
Thanks for your thoughts.
Dan
Blind Dog Surfboards
I don't know the answer - air volume wise, I think I'd feel pretty comfortable with one on a sub-7'er, but I'd go with two for anything over. It probably depends on the temperature swings the board will be subject to.
I only used a goretex leash plug / vent once, on my first board. I didn't keep it masked off while wet-sanding, and my slurry permanently plugged the fabric. Ever since then, I haven't wanted to try again, although I have heard of guys who use them with good results. (I've got a couple sitting around the shop, I keep thinking about putting into a board sometime, but always change my mind at the last minute.)
What is "surbject venting "?
Hi Huck,
Subject. Sloppy typing.
Yes guess two will have to work on long boards. I will hide one in DOG. The O an am ok with one in back. Heard about junk getting onto screen problem. Thanks for your conr back.
The number of vents needed is indeed relative to the size of the board. Expanding air inside a LB or SUP needs to have a short distance exit point, so having one about 18" from the nose AND tail is the best arrangement. The further away the vent is from the heated area, the hotter the area will get in order to push the air over the distance and maintain energy balance. Or the greater the resistance to flow, proportionately more energy is needed. The average 1/2" diameter Gore-Tex membrane flows 450 ml/min, but moving air through 6+ feet of eps is a much greater resistance compared to an outlet restriction. With a hollow board, there’s no resistance to airflow inside, so outlet restriction is the main factor there. So, with a hollow LB or SUP it doesn’t matter where you put the vents but they will exhaust fast and need more flow than 450 ml/min so you’re back to using two.
The life of a Gore-Tex membrane is effectively the life of the board provided that sand, salt crystals, etc are rinsed each time it’s used. The main failure mode is the sealing around the edges of the membrane. Wax, improper installation, or anything that will block it means replacement. On hollow boards, the inside must be free of sanding dust and debris as this will collect on the membrane when air is exhausting.
Got it. I can understand with eps that air is difficult to transverse to vents, hence the need for two. Just wondering, if it’s 450 ml that’s about 2 cups of air, when i vent release my other non-goretex vented boards, its a shallow wosh of air comeing out. Granted if i leave it in the sun all bets are off and I’m probably pushing over 10 psi and board will do nasty things to glue joints. But wouldn’t a goretex vent be working all the time, meaning if i’m heading to water, board is getting warm, air is venting, in water air is venting as board cools. I thinking keeping the vent towards nose, away from water make sense, I’m wondering if two vents in a hws is an overkill. Hate having two black bumps on our wood boards. guess I could hide one in the “O” on Blind Dog decal.
…hello PeteC, man, 2? there s plenty of chambered Balsas out there without any and performing right and you talk about 2?
too much man if you do not take planes or like that,; even in Ecuador you do not see any…
Hi Dan, yes the Gore-Tex is always breathing so there’s no pressure build up unless very rapid heating occurs. There’s no need to be concerned about the vent in the water, if it’s a crappy design and susceptible to leakage around the edges, then nothing is going to help it. Please re-read my previous post on hollow boards; you still need 2 because outlet restriction is an issue. If you’ve ever seen hollow wood “inflate” when heated, any cosmetic concerns will be quickly dispensed. The term “log” is very fitting.
Reverb, you’re quite right about chambered balsa boards. The reason that these don’t often have problems is because it’s a pretty thick insulation wall before you get to air inside, and it takes a lot of heat and a long time to reach the interior. However, with the thin skin on hollow wood, hollow CF, or just the epoxy on an eps core, internal heating occurs very quickly. How quickly depends on a lot of factors like humidity, solar position, elevation, etc. In SoCal it’s pretty much the desert; very low humidity, not much clouds or wind, perfect for a solar panel and the worst for board heating. There’s a lot of data published for solar collectors in various world regions based on how hot a 1 foot square metal plate will get at different solar times. The SUP’s used at Lake Tahoe (7,000 ft) are very susceptible, as well as in NZ where just going across the island to surf will take you higher than that. The low air density at high altitudes causes heat to transfer very fast. Problems with heat expansion on single vented boards in both these places is why I recommend two vents. Even in mild conditions, people will leave their boards on roof racks all day long in blazing sun, so it’s always better to be somewhat overkill since you never know how customers will take care of the board.
…ok, received
So it shall be: two by board. would a fish or something else HWS under 7’ be ok with one vent?
So it shall be: two by board. would a fish or something else HWS under 7’ be ok with one vent?
Yes, only one will be OK for under 7’.