May 20

Venting low density EPS, the final installment

We wanted to chat briefly about the 0.75 EPS wrapped in Carbon Fiber test panel for venting purposes. If you’ve just joined in we wanted to put to rest this concept that lower density EPS needs venting while higher density EPS doesn’t. ALL densities of EPS expand at the same rate. The concept that lower density EPS needs venting but not others is BULL and is most indicative of the folks not understanding the material properties of the foam they are working with.

So we stuck the test panel in the sun all day yesterday starting at around 7 am until close to sunset. Nothing. No bubbling, no delamination. It got warm alright, a shade over 100 degrees on the surface, but nothing more than that.


So we got a little impatient and took a hair dryer too it. We placed a meat thermometer onto the surface and held it in place, then used the hair dryer to bring the temperature up to around 170 degrees F.


Now we’ll talk a little more about the physical properties of EPS after this next photo, but suffice it to say that after about 5 minutes of exposure to 170 degree heat…


Still nothing. It’s just like it was when we finished laminating it. No bubbles no delamination. It’s just the same brick we started with.

As we’ve mentioned, EPS is amazing foam and Polystyrene is one of the most amazing plastics ever. One of the physical properties of EPS is that it liquifies at 212 degrees F. It completely melts and changes states. As you can see, 212 isn’t all that hot. If we can get to 170 out of a hair dryer, another 42 dgrees won’t be hard. But that change isn’t instanteous. It’s not like the polystyrene is perfectly fine until it reaches 212 and then POOF turns to liquid. At 158 degrees F, it starts to get soft and then progressively more so until it reaches 212 F and liquifies.

So will a vent help at 212 degrees? No! Unless you want a non-drip spout for pouring out the contents of your wakesurf board. Will a vent help at 158 degrees? Delmaination at that temperature isn’t due to off-gassing or an expansion of the underlying foam, it’s because it’s MELTING and changing states from solid to liquid. It might allow some of the pentane gas that was trapped in the EPS beads to escape, but that’s not the cause of the delamination, it’s because folks melted their boards!!!!! If there is gas that escaped from ruptured EPS beads, that have MELTED, guess what? That board is already damaged. The polystyrene in that area has deformed and collapsed. Venting won’t fix that. Also recognize that 3 pound or 1 pound, still melts at the same temperature, because it’s all the same stuff!

Maybe that’s the biggest misnomer here. It’s plastic. EPS foam is an extremely soft plastic and when it gets to hair dryer temperatures it’s starting to melt. Can it get that hot on the boat? Oh easily. Leave a dark board flat out in the sun when it’s 110 and it’ll reach 158 at the surface without too much effort.

Anyway…Melting the core of your wakesurf board is NOT a good thing and venting it won’t help it if it’s melted.

Remember that link we provided for the Coefficient of Thermal Expansion of EPS, where it was the same for all densities of EPS? Directly below that is a maximum working temperature for each of the densities. 180 is the point where EPS begins deformation due to changing states and quess what that max temperature is for ALL densities of EPS? Yeppers, 180 for short term exposure. So 3 pound or 1 pound beyond 180, it’s damaged. Period. As you saw, at 170, there is no delamination or expansion to destruction.

Bag it and shade it is a simple rule of thumb for an EPS and epoxy board and here is a another point to ponder. You’ll remember the concept that was introduced in the spammers and misinformers forum, that heat treating foam prevented delamination. Ok, not true, it’s post curing epoxy. Obviously it’s not post cured at 180, because the internal foam would melt. Know what happens to epoxy that is heated above it’s post cure temperature? It starts getting soft. So, if the wakesurf board is post cured at 130 and then it gets to 150 can you guess what’s happening to the epoxy? That’s right, it’s working on turning to a liquid!!!!!

If you want to see delamination really quickly, turn your laminating resin to a liquid and forget about the core. Liquified epoxy doesn’t retain it’s shape or really stick to much of anything! 🙂

So maybe that is the takeaway. If the person you’re buying your board from doesn’t understand the material properties of the stuff they are working with, that product may not be built adequately. Certainly, spammers and misinformation forums are not authorities but are typically great sources of advertising copy.

Thanks so much for following along, we really appreciate it!  We got out on the boat this weekend, in the crazy wind.  So we’ll have some wakesurfing pictures and also we’ve started work on that new wakesurfer.

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