how critical is vent in balsa/eps compsand?

I’m about to do the outer glass on my first balsa/eps compsand board. I’ve looked at a lot of boards on Swaylocks, some have a vent hole, some do not. I live in Hawaii, but always store my boards in a relatively cool place. The most time they’ll spend in the sun (out of the water) will be on top of my car on the way to surf. So how critical is a vent plug? I would rather not use one if I can get away with it.

If your using the Pac Allied stuff it gasses alot even at 2# densities. Its better to just take a few minutes and install the vent plug…remember we live in a very warm climate and its summer time


So how critical is a vent plug? I would rather not use one if I can get away with it.

I’d say critical. Everytime I take mine out even though the board is just warm it has a hiss of gas already built up. If you get a water sucking crack then it delaminating is almost sure thing… Vent is very easy to install and is a great conversation piece! Hahaha!

Thanks guys, I’ll definitely put one in then.

Where can I get one of these vents? I have searched briefly online with no success. I’m sure I could get something together buying some odds and ends at a hardware store, is there a better source?


fiberglass supply

chinook vents… get the alum. screw. the plastic ones that come with the vents suck assssssssssssssss, they leak and have caused me huge headache…

20+ boards Lowes and Marko

Never used one

never had a problem

neither did CMP

guess we’ve been lucky

the only delams we ever had

was due to over use of fastnfinal spackle or H20 paint on the foam

(CMP thought we should paint our blanks brown so when you have balsa sand thrus the white doesn’t show so much).

only microballoons and epoxy slur now to seal

I got a bunch of the plastic vents from FH that john said not to use if you want them.

Here’s an interesting followup question…

when we finish our 4-man outrigger balsa compsand canoe made from cheapo Lowes EPS how many vents do we need to use and where?

My answer is zero…

Thanks I just ordered the plug with aluminum screw. Thanks for the offer oneula. I figure I should play it safe like satorisurf with my first eps board.

Yeah, I just got back from Fiberglass Hawaii and they seemed really surprised the vent was for a surfboard, even when I told them it had a 1lb eps core. I picked up one of their plastic vent plugs anyway (hadn’t seen your post yet, JJP). Now I’m not sure if I’m going to use it. I guess that would be a good experiment, I’ll let you guys know if I have any problems. Also, thanks for the offer, Oneula. As usual, you’re too kind.

sorry forgot to add one critical element.

You should be vacuuming under and post curing in temps hotter than what you expect your board to under if you don’t want to use a vent. A heat blanket helps you accomplish this or a black plastic bag in the hot hawaiian sun

you also can pregas your foam by exposing it to high heat prior to glassing and lamming on your skins.

vents are definitely an added insurance

but these are made for personal fun and experiment anyway right?

who cares if they delam

Its so damn easy

just make another one…

then fix and give the delammed one to a poor grom who can’t afford a new board.

oneula is the pro in regards to construction/pricing… his 20 boards is alot compared to the ten of 1000’s of windsurfboards that are build using the same construction that are vented…

also from the boardlady

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!

For long-term storage, keep it in a nice, comfortable place. If you live in a cold climate and have to heat in the winter, keep in mind that the rafters where you store your board may be substantially warmer than the rest of the space. And do not let your board touch the furnace!! (you think I am dreaming up gory scenarios? think again!). Make sure you don’t store anything really heavy on your board, especially not anything heavy with sharp edges. Given enough time, your board will acquire dents that way. especially when it is up in the rafters. where it is warm…"

but then again we must be doing something extremly different anyhow as there is no way i could for a second think "Its so damn easy just make another one… " i guess if your just hacking em out and you don’t care that they delam and end up in the landfill putting in an extra 10mins to install a vent is a hassle…

Hey All,

Since we’re on the subject of vent plugs, how does one install those chinooks? I’m thinking of ordering a couple. but the pic on fiberglass supply has exhausted my imagination of how I’m supposed to install one of these things. Thanks in advance.



i’ll post some photos after i do one tonight or tomorrow…

it is pretty easy… basically no differnt then a leash plug.

tape the bottome of the vent.

drill a hole in the board a tad less deep then the vent thickness…

put in some q cell/epoxy mix… push the vent in being sure no resinmix enters the threads… allow to dry. sand smooth and i always glass over… then freehand router or use a large countersink to reopen the hole and then i use a 5/16th bit and CAREFULLY drill a hole through the bottom of the vent into fresh eps…

ps. i have had some of the plastic plugs work just fine but enough of them leaked that i won’t touch em again. i think the o ring that is supplied with them is too small to seal the slot that is in the threads properly… the alum. ones don’t have the slot and come with an oring that is like twice as beefy…

pps. i have some wood lam surftechs that i have left in the sun that have gotten so hot i burned my hand when i picked them up and they haven’t delamed… i have had a white windsurfboard and a yellow eps fish delam… i have some friends that work at rental/ ding repair shops and they say they see surftechs and all other eps boards in for heat delams all the time.

i have rented windsurfboards on Maui where the shop has taken quick stick epoxy and filled the vent hole… once i was standing next to with windsurfboads packed on the roof, it was blazing hot and sunny and all of the sudden this crazy poping sound started, a guys brand spankin’ new board completly popped the bottem skin off, he didn’t lossen the vent after the second use…

anything goes i guess…

Dammit, JJP, now you’ve got me feeling indecisive again! :slight_smile:

The only reason I would rather not put in a vent is for appearance. I know its not a big deal to install it. But like Carve Nalu said, the vent is a good conversation piece, if nothing else!

I know Oneula and his brother have got a system down, and they’re kicking out boards left and right, but it does take me a significant amount of time and effort to make a board.

Just out of curiosity, your trusty 9’6", is it a conventional pu/pe board, or a balsa/eps compsand you made yourself? Just wondering if every board, regardless of construction materials and methods experiences similar outgassing issues…

Satori asked a question

and I just stated what we’re doing.

But we’re not in this to make money

just learning the technique to make our own as we need to

(But we recently quit drinking the koolaid and stopped for now click below to see why, Greg’s got 2-3 other great designs he wants us to test out, you just can’t beat 35 years of design understanding)

Vents are a very good idea no doubt

but CMP who’s made more balsacompsandos and longer than anyone here on this BB other than Bert never does and that’s what he told us but he agrees it’s a good idea.

I would say if you’re looking at going pro then you’d better go with a vent expecially since you have a client paying you good money. If you’re just experimenting like us trying to learn what works and what doesn’t it may or may not be needed.

Jarrod (Shwuz) never put a vent in any of his compsandos either and he lives in texas.

A balsa covered piece of EPS shouldn’t take you any longer than a week 5-7 days straight to finish from a flat piece of foam to something you can ride.

And by the way you can buy a really nice shaped piece of urethane and cover that in epoxy/balsa too and not have as bad a delam issue as you do with EPS.

A balsa skinned Arakawa, Tokoro, Kashiwai, and any of a hundred other shapes are a good thing too…

I also have a 6’9" Surflight minigun which is urethane over polyprop over xps which doesn’t have a vent. So I wonder why Jim Richardson doesn’t used them on his composites which are way more prone to delams due to their blue foam XPS core.

But again vents are good preventative measures against any possibility of a delam.

the boards that really have the problem are the super light eps foams… becasue there is so much more air for the same volume… the problem is the air expanding… i think it was johnmallor who did the vac test on the piece of 1lb. i put his vac at one end and pulled air throught from the other… so ther are pathways through out the foam as well. that is why a vent works…

the 9’6" that i have baked in the sun was a surftech… but like i said i have seen other surftechs bubble…

i had a killer 10’6" erine tanaka clark foam and left it in the sun and came back to find the black “blue hawaii” lam was a perfect bubble… big big big bummer on that one… since it was the best longboard i have ever owned period. so dam funny it said ASP pro model on it… 10’6"x23"x4??? i didn’t know Erine but i like to think it was a joke…

when i was working as a glasser in Cal. we did a bunch of crazy fabric boards for a hippy fellow, clark and uv poly we dropped them off one nice Febuary? day and while we were shooting the shit we looked over and one of the boards had bubbles all over it, every place the fabric was black…

but on the flip side i had about 6 of those cheapo plastic chinook screws leak… one of the boards filled up with about 5 cups of H2o on the guys first session and left a nice black stain on the balsa directly under the screw… we worked it out but it was deffiently a losse loose…

so leaking vs. delam vs. looks vs. ego… fast and loose you might say.

i am also building a rig that will use the vent screw hole as a way to susspend the board for spray finishing, but that is another vs.


JJP…I’ll be waiting for your pics tomorrow…

a vent is very useful to get water out when fixing dings(by hooking up compresed air)

also allows board to breath when fixing dings so the ding resin doesnt bubble

vents are good

also for travel i think in depressurised aircraft holds

vent are good to test for leaks or pinholes in the lam or around finbox plugs

1# core you need a vent if you live in hotter climes

2# core might be okay


Paul Jensen puts manual vents in his HWS.

He does it all custom and drills a hole through the bolt before installing an O-ring to seal it. They seem to work but only Paul has the focus and concentration to remember to open and close it every time.

On a surf trip last year, I saw his board sitting in the sun and thought I’d better double check the vent… why bother? Of course it was already unscrewed!

I’d be better off with one of those Gore-Tex vents if I could find one.

Lots of great info and experience talking on this thread. I really appreciate all the input. I’ll sleep on it and decide what to do tomorrow when I finish doing the outer glass.

Mahalo, everyone!