EPS and Vents Question

     I am just glassing my first couple EPS boards and I was wondering about vents. I am using 2 lb. EPS that I cut out of a block of foam, and glassing with RR Kwik Kick. I have read that vents are necessary in all EPS boards, but then I have read conflicting views saying you don’t really need them, or that you don’t need them unless it’s lighter weight EPS. One post (which I can’t seem to find right now) said you might only need a vent if your board goes through a very extreme temperature change in a very short amount of time (I think this example was from Australia).

     I would be using a vented leash plug, so it’s not like it would affect the looks of the board or add any extra work, but at $12 a plug it adds considerably to the cost of the board, especially since I’m making the blanks for much cheaper than they would cost normally and trying to keep costs at a minimum (a small part of the reason I started making my own boards was because it was cheaper than buying new. But then add tools. Then a shop. Then supplies. Then mistakes. Then more tools. Then more mistakes. Then more supplies. And making more boards than you would have bought normally. Cheaper, right?). So what do you think? I’d especially like to hear from people from the Northeast who deal with the same kind of air and water temperature fluctuations I do, but anyone’s input would be greatly appreciated.

Chris

I’d like to know how others feel about this scenario. I’m using the same exact materials.

Around here the only EPS-core boards I see with vents are the ones with Wood or D-cell composite skins.   Other than that most builders don’t use vents.  The boards seem to hold up fine without them.  With that said, I also don’t let my boards get super hot, either.  

We have 4  Epoxy boards from assorted sizes and manufacturers in our shop for repair Not a single one is vented…

Only if you use 1# foam and even then it’s still not that nessasary.  

The only delamn I’ve ever had was on  1#eps with glass on fins.The board had a goretex vent similar to the firewire vents and I had left the board in the boardbag laying in the back of my truck for a few hours in Florida heat. Pulled up to shoulder high glassy surf and when I got my board out of the bag the fin area had blown up like a balloon the skin was about 1" from the foam. Now I only use 2# eps and try not to keep the board in a bag in the heat because they are like ovens. I dont use vents any more because they can just as easily fail causing a leak or a delamn. I’ve found it easier to just keep my board out of the sun.

It happens.  This isn't the first one I've seen either...

 

There are several different types of Gore-tex membrane vents:  The Firewire type, the Hobie “Wavvy” type, and the actual Gore-made vent that is sold by Foam EZ, Fiberglass Hawaii, etc.  Any membrane that is mechanically clamped around it’s edges is prone to water leakage based on the 5 years or so these have been on the market.  All high-end SUP manufacturers use some sort of vent, and through their experience, it’s a lot cheaper to spend $15 on a vent rather than a warranty replacement for a $2K SUP.  Regardless of how you tell customers to take precautions on not getting the board hot,  it happens.  As with most eps/epoxy problems, customers are shocked to find out repair costs, how long it takes to dry it out, how much airbrushing the painted imports cost, or that it can’t be in the sun for very long.  Unless you offer them some sort of satisfaction for these issues, they’ll never buy another board from you again.  The delam returns I’ve seen from various manufacturers always come with the same story: " I just left it on my car (or on the sand) for less than an hour".  So, go see for yourself if you need a vent or not.  Put it on the car roof or on the beach in the sun and time it.  If it doesn’t happen, then you’ve saved $15/board and can tell everyone that I’m full of shit.  Also let the hollow-core and windsurf guys know that they don’t need a vent either. Too late for FCS, they already tooled up a vented SUP handle.  However, if your testing fails you can still get a open/close type vent for about $3 and add about $10 to your margin.

As the first US supplier of Gore-tex vents in 2005, I’ve been accused here of creating paranoia that eps/epoxy boards are prone to delamination under typical conditions if treated like a poly board.  The rationale I hear most often is that “it has never happened to my boards”, or “I’ve never seen it happen”, or “it’s a function of the eps density”.  I’ve never heard or seen any engineering data to back any of that up.  The fact is that ALL eps has a coefficient of thermal expansion which is ridiculous, and critical at very low temperature (<120F). Ever had your wax melt?  That takes a surface temp of about 120F, so heating like this isn’t unusual.  Eps is only about 3-5% polystyrene by weight, the rest is air between the beads and the gas in the beads themselves which both expand (as a cubic function) very easily when heated. For thermal expansion purposes, it IS a hollow board.   Note that many import eps cores that use plywood or D-cell sub-skins can contain expansion to a higher degree than a simple glassed blank, but it only takes a bit longer or higher heat to delam/inflate/whatever.  Once a delam happens, the expanding air in the board goes directly there since it’s the path of least resistance (rather than start a new delam) and it inflates and starts peeling the lamination around it like John’s photo. The vents work also in this same way.   Basically the beads are sealed and when they expand,  the air spaces between them are allowed to reduce (crush actually) and the air flows out the vent since it’s the path of least resistance.  This is the steady stream of bubbles that are seen when a hot vented board is put in cold water.  With no vent, the air expands along with the beads and the whole core increases in volume.  And this doesn’t even require heat.  Glass a board at sea level then take it to about 7,000 ft elevation and see what happens.  The guys who first took early SUP’s from LA to Lake Tahoe found out.

John. That looks like the hind end of one of those hot mamma’s wearing purple stretch track pants at Wallmart…:wink:

  “Blooody  sexy”

 

I don’t like the idea of leash cup vents as i’m sure they sit too deep in the water at times being at the tail and also have to put up with leg rope stress.

I like the old chinook windsurf style of vent, as long as you remember to tighten it up before entering the water and  and releasing it when you get out again.

 

…first: EPS is a crappy material; that only belongs to a surfboard due to weight ratio.

second: you can put a vent but what happen if the owner do not use the vent…

3: around mid 80s a boardbuilder here made a big batch of EPS, vinyl glue instead of epoxy and polyester resin, I had one also,

lots delam in the deck ONLY, I never saw one with the bottom delaminated. In that time I was thinking about that the vinyl glue was the offender.

These boards did not had vents.

 

G’day John , was that board hand laminated or vacuumed ?..seems like a bonding issue , rather than a problem with an unvented eps core…

I take exception to EPS being called crappy material.  It's excellent if made right and if you know how to use it correctly.  IMHO anyone selling a board using 1# density foam is an idiot.  Make one for yourself or for your buddy, fine.  Sell one, no way.  

I had the same opinion of many low weight PU foams as well.  There comes a point in every foam technology where the stuff is just not stable.  EPS will melt, delaminate, break, just fall apart if your using 1#.  PU will shrink, delaminate, break and just fall apart at around 2# density.

 The photo above of EPS delaminating is from the color.  The color made this board heat too much.  The heat melted the foam.  The builder shouldn't have used that color of that blank. A very light PU would have shrunk if done the same way. 

 Taking an EPS on a plane is no issue either unless it's 1# density.  Then perhaps an issue.

 Bottom line is, no matter what the foam, when you deal with densities that are on the cutting edge s#=t happens.  Venting doesn't solve that, a bit higher density does.

The constant quest for lightness is another sidetrack , that continually provides its own problems to solve…we should all know by now , what the correct weight should be for a desired performance of a given design  , and an  individual surfer…one big advantage of eps , is that it allowes more durability to be built into a board and still meet weight targets for HP surfboards , without compromising strength…

hi greg

 cant say i disagre with any of that   you are so right.

 

 cheers huie

…but a good close tolerance P/U blank will always be prefered by tradesman shapers !!!..huie!!!..whens the boomarang box comin’ back ?

The thermal expansion coefficient is the same for all eps densities:  0.000035 in/in (degree F) linear, and 0.001/cubic inch/degree F volumetric.  As a typical SUP has a volume of 16K cu inches, this means internal volume will increase by 16 cu in. for every degree increase in temperature.  Bouyancy is also the same between 1-3 lb density; 50 lbs /cu ft.  The only differences when density changes upwards from 1 lb/cu ft to even 10 lb/cu ft are the insulating properties (not applicable),  strength properties (not applicable after glassing),  and moisture penetration (not applicable).   These are the ASTM 578-92 material spec's that 98% of all eps is made to.   http://northwestfoam.com/fact-specs.htm

So the only difference is  the finished weight (design attributes like flex and such excluded).  However, this assumes that the glassing or shell construction is far stronger than the eps core strength properties.  With plain glassing this isn't the case, and the core contributes to the total strength.  Compression, shear, and flex strength for 2 lb is almost twice that of 1 lb.   Experience does show that 2 lb is acceptable with plain glassing, but 1 lb isn't.  However, the use of carbon fiber, sandwich construction, etc. to increase the shell strength makes 1 lb a viable option. The trick is to maximize the shell strength to weight ratio to take advantage of the 1 lb core.  In 14+ ft  SUP's, 1 lb is a huge difference over 2 lb.   Keep in mind that spec'd density is really the average density over an enormous block; so most "2 lb" foam is actually about 1.75 lb and "1 lb" about 0.80 lb.

In terms of eps characteristics, bead size doesn't matter nor any other geometric factors in terms of density.  You basically have X amount of air + Y amount of bead gas + Z amount of polystyrene in whatever shape.  To get different densities, Y and Z are varied and X fills in the total.  The real story is rather complex and unecessary since all we need to know is what is available in eps densities and the strength properties relative to how we're going to glass it.

Taking an eps/epoxy board on a plane is irrelevant since all cargo holds are pressurized like the cabin.  Hell they put pets in cargo.  So unless your airline has roof racks, this isn't an issue.  It is a simple fact that if you seal 14.7 psi in a container and take it up to 7000 ft where the air pressure is 11.34 psi, the internal container pressure is now 3.36 psi higher than ambient.  That's no different than heating the container at sea level so that pressure increases to 18.06 psi; if the container can take it then everything is OK. Solar radiation is also stronger at altitude, so you can have a double whammy effect.

I must agree with Greg that eps is not a "crappy" material, and that it adds a new, big dimension to design.  Ask any of the major industry players where they would be today without SUP sales, and this wouldn't have happened without eps/epoxy technology and Greg himself.   As with anything new, we have to first understand the processes needed to work with it, and in parallel understand what happens to the finished product after the average dumb ass buys it.  To obtain this understanding, you can:  (1) Guess, (2) Copy somebody else, (3) Figure it out analytically, (4) Or like some import manufacturers, copy somebody who already did figure it out analytically.  However, you will not truly have the understanding unless you pay the dues and find out for yourself.   This knowledge is what leads to the cutting edge.

 

 

 

 

  uh i just got it haa’’

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cheers huie

eps make fantastic surfboards. havent vented for ages. molded eps is the one. ditch the stringer on shorties. i just got a bandsaw.

…hello Loehr; yes, you re right about the density, but I maintain that polystyrene have a place only for the weight ratios, so my comment was based on the in famous #1 or so density aka the hardware store thingy

in other densities the PU can compete in a good way with less hassles and better looking board; no need to hide the PU

A vent plug properly installed is the cheapest board insurance you can buy.  PeteC makes the best vent plugs.  I have been making epoxy boards since the early eighties, working for or with epoxy experts, like Clyde Beatty, and Greg Mungall, shaping for them, and at Paradise.  Seen quite a few pufferfish, all without vents, a few that I made, even one that Greg Loehr made, whom I totally admire for all his contributions, (it was his board, so it was probably one pound).  A vent plug isn’t necessary, but it sure helps, at least from my years of observations.  I guess that’s a plug for PeteC.  Oh RESIN RESEARCH is the best epoxy for surfboards by far, and I don’t get paid to endorse these products- they’re simply the best…