We wanted to touch briefly on the concept of open and closed cell foams and also try and tie it in the potential to use 3D printers to create a “foam”.
We hope that this will be sort of informative, we’ve become rather jaded at all of the advertising going on, on social media sites and various forum based websites. It seems like everything is an advertisement at this moment, spammy videos and facebook also, everyone is a freakin business! #buymystuff! Lordy, it’s exhausting.
Anyway, this post isn’t trying to sell you anything! What we want to talk about is the concept of open and closed cell foams. You’re familiar with them even if you don’t know the terms.
The iconic example of an open cell foam is the sponge in your kitchen. A little background, a foam is created when air or some other gas is trapped inside a solid or liquid. So like we stated earlier, your kitchen sink sponge is a foam, but also so is the foam on the top of your beer. The gas bubbles are trapped in that liquid at the top.
In a closed cell foam, the gas forms discrete pockets, each completely surrounded by solid material. In an open cell foam, the gas pockets connect with each other.
Here is a wonderful graphic representation that we did for just this purpose!
You get the idea, closed cell foams are basically solid chunks of “stuff” with air bubbles trapped inside, whereas open cell foams are solid chucks of stuff with pathways that are interconnected here and there.
This is important from a wakesurf standpoint if we ever get a ding. In a closed cell foam, if the ding intersects a trapped air pocket, we might get some water in that one air pocket, but it’s sealed off from all the rest of the air pockets, so we don’t really need to worry ALL that much about a ding.
What about open cell foams? That’s not true is it? It’s possible that a large number of the trapped air bubbles are interconnected, so a ding that allows water to enter one of the trapped air bubbles, could very possibly allow water to enter a large number of those interconnected air bubbles.
The most common type of foam used in wakesurf board construction, today, is EPS. As we mentioned in a previous post it’s a plastic made from Polystyrene. In an oversimplification, EPS foam is made by creating thousands of tiny beads which individually have a single pocket of gas trapped inside. It’s possible to term a single EPS bead as a closed cell foam. The problem is that it’s maybe 1/8″ in diameter. So while THAT is a closed cell foam, it’s not very practical for use in anything.
So, EPS foam boards are made by MOLDING (hot damn!) thousands of tiny EPS beads into some shape. The EPS beads are expanded with heat and then “fused” together to make a final finished shape, like a coffee cup or something…or a wakesurf board!
So we know that EPS can be used to make coffee cups and they hold steaming hot liquid, so they must be CLOSED CELL!
Technically it’s still an open cell foam, BECAUSE there are often microscopic little pathways in between all of the squished beads of EPS, BUT practically speaking those pathways are often smaller than the individual molecules of the liquid that are used by the foam. So in our coffee cup example, there are actually little tiny pathways all in between the squished beads of EPS, but they are so small that water can’t get through them. This is true of epoxy and polyester resins also. They aren’t a solid barrier, but the little tiny holes are so small that water can’t migrate through them.
So we’ve talked about closed cell foams although we failed to mention any, divinycell is one and it is used in the construction of most skim style boards. Open cell foams like your kitchen sponge and then open cell foams that are, practically speaking, closed cell like EPS foam.
Remember that we talked about plastics a few posts ago and then we basically said virtually ALL of your wakesurf board is made from plastic? The one misconception that folks typically have is that the interior foam of their board ISN’T plastic, but polystyrene is a plastic.
EPS foam is really interesting in that while it’s a plastic it’s principally all air or gas. Inside those little beads are trapped gas and that is the largest part of the bead itself. LOL! It just struck us that what we should be saying is that our wakesurf boards are mostly GASEOUS!
The EPS beads are sort of randomly oriented, but if you could look at the structure on the interior of the board, the plastic walls of all of the beads form this intricate, if random, honeycomb. That is to say, there are all these walls made of plastic and then inside of those walls is trapped air.
The key point is that it’s PLASTIC and AIR.
That got us thinking (more) about the concept of a 3D printed board. We know that current technology prints plastic easily and it would be very easy to print some geometric shape in which thousands of little…we don’t know, sort of “tetris” like shapes that fit together, but inside was trapped air. So rather than solid geometric shapes, they are hollow geometric shapes. Guess what?
That’s a plastic foam isn’t it? We have no idea how long that would take to print, or if the cost would be prohibitive, but it’s possible to 3D print a wakesurf board with the basic identical structural makeup as one that uses EPS foam as it’s core.
Thanks so much for following along, we really appreciate it!