vent plugs

Most people just loosen them after a sail to let out presure and what not i think. Your defently meant to when the boards left in the sun for a while, traveling in an aeroplane and i'm not sure if your meant to when you drive with them.

I take it completely after every sail on every board. Some find this risky because if you forget to put them back in it can cost you. However i just keep them with the fin screws and i won't be sailing off with no fin. So i wont forget that way i don't reckon.

Others may be able to tell you a bit more. The idea i think to to stop a heap of presure building up inside the board.

Bubs

They are for venting. When you are good and angry you open them up and go and sail til your board's full of water and sinks. Then you feel better.

No. I lie.

What they do is allow the air inside the board to go through pressure cycles without stressing the board. Styrene foam is piss weak stuff. The rule is - keep them open when off the water and closed when on the water.

Pressure cycles come from the daily change in temperature (minor), change in altitude (air travel is the big one) and the biggest one - if there does happen to be a bit of water in the board, and you put it in the car on a hot day with the vent closed, well suicide bombers have been known to do that.

Bub's right JP, the inner core of most modern boards isn't "closed cell" in other words, there's free passage of from any part of the board to anywhere else. So you only need 1 little weak spot in the laminate and any +ve difference between inside and outside pressure, can have all the extra air inside expand that weak spot into a big delam.
You'll find boards with "closed cell" foam don't have plugs.

If the board's built well there shouldn't be any leakage, after all there is the internal layer of cloth, 3m to 6mm of closed cell sandwich foam, then another layer of cloth. Each of those 3 layers should be water proof.

My impression of the Philippines is that it's always hot, so unless you leave a board in the sun or in a hot vehicle, or transport it in a plane's cargo hold, you're probably OK.
I like Bubs, leave my vents open, unless I'm actually sailing, just have to have some system of ensuring they do get closed before they hit the water!!!!
Well worth the effort if it stops a big delam!

As far as I can work out, the pressure changes are much bigger when there's some moisture inside the board. If all the air inside is dry, then the pressure change is minimal.

My new board doesn't hiss when you undo the plug, which probably means that the air inside is nice and dry.

An old board that I'm borrowing at the moment has a definite hiss when you undo the plug, which probably means that there's a bit of moisture inside.

When I see people undoing the bung as soon as they get their board onto dry land, I always think it's a bit strange... because if there's less pressure in the board than on land, the board will take a big gulp of seawater that's collected around the vent screw. Do this a couple of dozen times and you'll definitely have water in your board.

So for new boards I keep the bung done up tight, unless the board is totally dry and I'm leaving it in a hot car. Old boards I undo it.

Other people have different ideas, I'm sure

Well I certainly wouldn't be happy, unless you can keep it at a constant temp and pressure.

Saying that, I've been borrowing some ancient "Styrotech" NZ slalom boards, they're definitely open cell foam and have no bung, but they are painted plain white, although they've certainly traveled in a plane's cargo hold. No sign of damage.

To quote Eva the Boardlady
www.boardlady.com/faqs.htm

Q: my board has a vent plug. Should I open it when I'm not sailing?

A: YES!!

The difference between external air pressure and internal board pressure determines the exact thickness of the board. As the external pressure fluctuates every day (typically cool early mornings with high pressure, then thermal low mid-afternoons), the board will first compress, then expand as the day wears on. In a thick, high-volume board, this change can amount to 1/4" or more. Picture such cycling going on once a day, 365 days a year. Picture the EPS foam core fatiguing and slowly separating into chunks.

Much better to open the vent between sessions, to eliminate this cycling!


And also:
boardlady.com/maintenance.htm

make sure you never put it away wet and zip up the bag!! The moisture contained in padz and straps, as well as attached to the board itself, will create water vapor in the bag when exposed to higher temperatures (substantial in a closed, dark car!). This water vapor can penetrate into paints, causing blisters.

How bad can it be? a sailboard with padz and straps typically holds about half a pound of water, or about one cup. That will make a lot of vapor when it heats up in the greenhouse that is your closed bag.

Always leave the bag open, until the board is totally dry!

And for you windsurfers who listen to my preaching about opening the vent plug when not on the water: if you open the plug, then stick the wet board into a bag and zip it shut, the moisture from padz and straps will find its way into the EPS foam core. Don't go there!
And speaking of vent plugs: opening yours whenever you are off the water is the single most effective thing you can do to prolong the life of your board. Leaving it closed will cause the EPS foam core to expand and contract at least once a day. You take any substance, no matter how stout, and you push and pull it continually, at least 365 times a year, and it will fail. Guaranteed!

It's not that much, you say? I just measured my Trusty Old 9'-4": typical summer day, near sea level, early morning, cool 60 degrees, it was 4 15/16" thick. Then the day warmed to 89 degrees, a thermal low developed, and the board expanded to 5 3/16". That is a whopping 1/4" change, or 5%!!

Get into a routine, where you tighten the vent screw just before you put on your harness, or some such thing, and it will become second nature, and you will not forget. But DO IT!

Is anyone else thinking what I'm thinking?

Let's make a BOARD BONG!!!!!!!!!!!!!

over the years i have had 2 boards delam from failure to remove the bung..i guess i am a slow learner
may be the respected shaper in gero is building nice structurally strong, double sandwich wave boards and as such they are stronger than the run of the mill slalom/free ride builds,that may have a lighter lay up.
the fact remains if you, for example, screw your bung in to the board when the temperature is 20deg and you leave it in and the temp goes up to 40 then the volume of air within the board will double thus creating a lot of expansion force inside the board.
and the oppsite would be true also if the temp drops then the air will contract within the board thus creating a small vacumn which could suck water if there are any slight pin holes.
i guess the temp in the phillipines is typically constant so these forces may not come in to play as much. here in oz its not unheard of to have the conditions as i described above.
i have a ouple of carbon art boards and these have goretex vents which allow free movement of air while keeping the water out....perfect!

And if the temperature ever hits 0 then you get a division by zero error and the universe explodes... let alone negative temperatures

The real physics is as follows:

PV = nRT (en.wikipedia.org/wiki/Ideal_gas_law)
Pressure x volume = number of gas molecules x Some constant x temperature

Temperature is in kelvin.

So the difference in pressure between 20 degrees C and 40 degrees C is around 6.4%, assuming your board doesn't expand due to temperature (which it will, so the difference in pressure will be less)

This may change when water and steam is involved though...

Think that's what snides is talking about with his carbon art goretex vents.

Nup, well I'm sure he's using strong wave sty;e construction but that's not why he's not using bungs
As I said he's using closed cell foam, (super light urethane), I'm sure if he was using open cell polystyrenestyrene, he'd put real bungs in. No matter how good the construction is, I'd still include a bung with open cell foam.

If the air can't move about in the foam, a bung is pointless!!!!!
Be interesting to know what the expansion contraction effect is with these boards, anybody know?????

hmmm..really interesting scientific views..coming from up here in the tropics it tends to get hot real hot and humid and am used to leaving the boards under the sun and stuffing it inside bags after use..i have a spare plug hidden somewhere in the extra's kit just in case but never bothered to
unplug it since am as forgetfull as a drunk if excited..i've done stupid things like going zipping along the water only to forget the fin cover was still attached(my mate did this one stunt too) and the usual something's missing-where's my harness?!?but i should start doing that by taping the vent with a colored tape once in a while to remind me to close..yep i understand the logic of pressure since it's a hot environment and then suddenly on water or vice-versa might as wellyou know what for some reason wetwilly i have a 5% bet that boards sweat minutelynow that you mates mentioned about delam am thinking twice but a fellow sailor told me once hardly a delam on carbon wrapped boards

somebody mentioned putting your board in it's bag and closing the zip. Anyone have a board bag with a zip that works

The use of O'rings is not flawed.

The use of the wrong sized ones is.

Most Orings used are 1.25mm - 1.5mm cross section do not cover the thread entry properly.

It's not a tough issue to resolve.

ok nobody picked up on it!
note the use of the word VOLUME no mention of the word 'pressure' see
'charles law'......