my current new (ish) board has a valve screw, can anyne pls tell me ,do they need to be unscrewed at the end of the day ,or just when travelling or ,or ?

If the pressure inside is greater than that outside, all it needs is for one very small weak spot where the skin joins the internal foam and it will start to delaminate, once started it rapidly spreads.
So it there's any chance of inside pressure eceeding outside, undo the bung!

I always unscrew mine (maybe sometimes not in winter). I blow the water out from around valve before releasing. Not sure if this does anything. May save a drip from getting into board each time breather is unscrewed

Pugs

The hiss dosent occur on all boards though, the 2 off the boards i have now hiss but none I have had in the past did and none had leaks.

If you leave it in you should remember that the board will go through a cyclic stress every day just with the change in temp. If its a tough old board it probably wont make any difference but if its light and sexy you're probably losing some service life.

So if you do get water in, how do you get it out? I had a mate who undid the screw when he got back to the beach then started packing up and came back to his board and started hosing it down. @#$%!!! He said it wasn't major but when he stores the board he puts it upside down and a drop of water comes out over time. Can you suck it out? Will it dry up if you leave the board in the sun?

i got some water in my board, i just stuck it out in the sun with the bung undone for a couple of days, the inside of the boat will get quite hot and everything will move towards the open bung, and the water will come out. U can also remove water by setting up a vacuum. This lowers the internal pressure of the board to below the vapour pressure of the water causing it to evaporate inside the board and its then sucked out.

I havent tried this but u can also use a fish tank pump, and drill 2 holes in your board one at either end
then blow the fish tank pump through the board. U have to use that dehydrating stuff which should suck all the moisture out of the air before it goes into the board. Dry air means more can evaporate. :D U will never get all the water out. And if its only a little bit of water no biggy. Every board gets a little bit of water in it (atleast in my experience), whether its taking the bung in and out, getting a small ding, or having a small leak. You can prolly get water in your board just by taking the bung in and out. If you have a hot humid day and the bung is out. Then u decide to go for a sail. The humid air inside your board is gonna cool down when u put the board in the water. This could cause some water to condense inside your board... eek. So anyway you go, your screwed my friend, best not to worry about it too much.

seriously though, if you stick your board in the car, take out the bung... otherwise it will get ****ed

ummm! chris lockwood just pulled an ave speed of 45kn+ on his water logged,8.5kg (speed) board!!!! maybe water in the board isn't a bad thing after all??? then again he may of cracked 50 if it was water tight!!........food for thought?

Cansyd:

that is ok advice in "normal" places (thought i doubt the cold "suck" will do much damage as the 2 min in the water after damaging the board will soak in enough water)

however, for hotter parts of WA, a car gets up to 80deg with windows up, lets say if gear is in the car while ur at work and going for an after work sail. Epoxy boards have gone pop before, i'd rather chance it that IF i put a hole in the board it sucks in 10% more water, than chance it that i never undo the screw and then on a hot day she delam's.
Easier to get water out than fix a delam on a $2500 new board.

How does a new board with its plug permanently closed handle the heat compared to a polyester board?

quote:

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Originally posted by wendell

How does a new board with its plug permanently closed handle the heat compared to a polyester board?

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Apples and oranges, polyester boards (guess you mean closed cell urethane foam boards) don't have plugs, air doesn't travel thru the foam so a weak point can't "blow out".
Unlike open cell foam, where all the air inside the foam can travel to a weak spot and cause a great big bubble. That's why the valve is there!!!!

quote:

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Originally posted by Harrow

Decrepit,

Why don't epoxy boards used the closed cell urethane foam? Then we wouldn't have all this worry about water take-up, would we?

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Good question Harrow,
Basically I think it's density and price, traditional urethane foam blanks are around 30kg/M3, wheras most sandwich board's foam is under 20kg/M3. It's possible to make the foam lighter, Stone surfboards in Geraldton is making sandwich construction boards with it, but still using polyester esin. (think he's worried about epoxy's toxicity).
The problem I have with this is fixed blank size, limits shaping options somewhat, especially for bigger boards.
There's also a closed cell styrene foam, I've made a couple of boards from that and BlueJuice was making custom boards from it. Unfortunately they've increased it's density, so a light board is no longer possible with it. Blue Juice was looking for a substitute, don't think he's had any luck.
I'm sure if the big companies really wanted to they could come up with a process to use closed cell foam of some description, us little guys can only go with what's available.

Very much the same, damage doesn't start to occur to either of them until the foam inside starts to melt!! Well a bit before then probably you'll get some degradation of the resins and the foams before they actually melt.
At about 50C if the boards haven't been heat cured, the resins will shrink a bit on cooling, making the cloth pattern stand out, but that shouldn't affect strength or perfomance to any degree.

The other difference could be the prescence/absense of a stringer, with a lot of heat (about 100C) foam gets soft and flexible, depending how the boards are supported, without a stringer, there could be rocker distortion.

Of course it is, below 100C the damage is done by the expanding air inside the board trying to get out.
If it can't get out, and there's a small weak point, that weak point will grow into a big delam!
a 0 to 25 increase is a bigger percentage change than 25 to 50, although I don't have the phsyics to make any pronouncment about any difference in expansion. In practical terms I don't think there's much difference.

Therefore I assume the percentage difference is relative to -273C, so when decrepit says 0 to 25 is a bigger change than 25 to 50, it's only about a 10% difference (between those two ranges, not to be confused with the increase in pressure within either of the ranges.