Bladder molding wake surf board internals

We have lots going on here at Flyboy Wakesurf boards and we want to share some wakesurfing pictures and video from the other day with the CMS crew and then also share some fun new wake surf board building projects.

If you’ve been following us you know that we are working through a hollow carbon fiber wake surf board build. We want to introduce a concept referred to as bladder molding, as it’s something that is used frequently when molding hollow items or where extensive voids are included in the final product.

We want to take a moment to talk about molding, all by itself. In surfboard parlance there is a term “popout” which negatively refers to molding surfboards. The concept is that molding, as a construction method, is not good.

In our opinion, a mold and the various methods of molding are just a tool. There is little difference between a plane and a mold in terms of construction, it’s just a different method of shaping or using something to develop a final product. There are also tons of misnomers about molding, things the final product will come out too resin rich, or too heavy. Like after 100 years of molding various products, everything from car bumpers to cell phone covers that all those talented folks look at a surfboard and scratch their heads, man I sure can’t figure out how to make it lighter or use less resin. We can mold space craft parts, but those surfboards MAN just can’t figure those out!

Ok we had fun with that, but you get it. It’s just bull. If the ultimate goal is a lower resin content, extreme light wake surf board, 100 years of industrial molding experience could make it happen in 10 minutes. HOWEVER, if you’ve never molded and don’t understand it, or it threatens your livelihood, sure molding is the DEVIL!

Bladder molding gets it’s name from the concept that the mold itself has a bladder internally that is inflated with air pressure and when that bladder is expanded it presses the laminate layers up against the walls of a female mold surface. here is a visual of the concept

Ok Ok Ok, we get the clown’ish idea. Imagine that the threaded piece is a closed mold and that the balloon is a bladder. You can then easily see that in the inside of the threaded piece had wet fiberglass or carbon fiber, inflating the bladder would force the wet laminate up against the walls of the mold. When the resin cured, the piece would be hollow and would have the exact shape of the mold. We’ll run through a quick demonstration so that you can get a better idea of the process and hopefully see how this method of molding can be used to create hollow objects like a wakesurf board.

Molds, for the most part, can be made from any rigid material depending up the processing. Here we are using a piece of PVC pipe, but of the processing required subastantial heat, then aluminum might be a better choice. Regardless of the molds material, it will need a form of mold release, in this case we use wax. We applied several layers and buffed it out on the inside of the piece of threaded PVC.

We didn’t get a very good picture of it, but we cut a piece of carbon fiber to fit inside the mold and we also cut the piece into two pieces one LONGER than the other. In a production environment, the mold for a hollow carbon fiber wake surf board would have to be two pieces, so that the laminate could be laid in, plus the bladder itself. It’s not real clear in teh example or discussion, but one side of the laminate will need to overlap and adhere to the other side. Similar to rail laps. That will be achieved by leaving some excess material on one side of the mold and then “flopping” that onto the UNinflated bladder so that upon inflation, the excess material is pressed up against the material that is on the other mold surface. In effect, creating a lap, like the rail laps we are familiar with.

Now comes the fun part. With the mold release applied to the molds surface we can do just about anything we want ON that mold release and that “anything” will transfer to the finished part after the resin cures. Want a gloss surface on teh finished part without sanding for days? Spray a clear coat on the molds prepped surface and that’s done. Artwork, or maybe you want a texture? All of that can be applied to the prepped molds surface and it won’t stick to the mold, it will transfer directly to the finished part. We’ll demonstrate that by hitting the molds surface with some green paint.

This is what it looks like! That green, will all transfer to the finish part.

So you’re in a production environment and you want a logo under glass and maybe some color under the laminate and you don’t want to spray anything, just use resins. Lay down a super thin coat of epoxy, torch any bubbles so that the surface is gloss. And it will, if you spend the time to hit any surface bubbles before it gels. BUT you could also use polyester clear. If you’re using epoxy, lay down a layer of fiberglass, and your logo paper with clear epoxy, again torch the bubbles. You could then lay down a printed laminate or resin swirl or solid color before or whatever you wanted. Basically all you are doing is reversing the process, but the key is that the external surface will be a mirror image of the mold’s surface. If it’s polished and glossy, the molded product will be too, within the limits of the material pressed against the surface of the mold.

Ok so next is where we wet out the laminate material, in this case the two pieces of carbon fiber strips. This picture gives a better shot of the two different lengths. Imagine the shorter pieces is cut flush with the surface of one half of the mold and the other has an overlap of maybe 2 inches or something, all the way around.

Hard to see, but we’ve loaded the mold with our wet laminate and overlapped the longer piece ONTO part of the shorter piece.

Once the mold is loaded with wet laminate and closed, the bladder is inflated, pressing the wet laminate against the mold’s surface until cured. High temperature bladders made of silicon can me used so that the molded product can be heat cured, or whatever is needed.

So let’s take a quick look at the finished part. Now realize we didn’t trim any of the flashing, nor did our “mold” have any edges at the ends that would force a finished end. This should just give you an idea of the process and what it’s capable og.

You can see that the weave is visible, we didn’t use a super clear epoxy nor was the interior of the mold polished, so those things are apparent in the finished part. ALso that the shape of the mold is retained and while it’s not really visible, there is an overlap in the material. No pinholes in the cured epoxy and it’s principally finished as if it’s been sanded and polished, without any labor in that regard.

Remember the green spray paint? It fully transfers to the finished part.

That should be fairly clear as to application in a production environment. It’s a little odd in that it must be applied in an inverse manner, but solid base coats or a printed laminate are fairly straight forward. In the picture below you can also see the shape of the product mimics the mold. If we had an actual mold we could have finished the ends, but the point should be cear. Hollow structure in the shape of the mold, with the exterior mimicing the molds surface.

Close up of the interior of the part, it’s hollow and retains the same basic shape as the exterior. It’s also now a solid singular piece made from two pieces of fabric.

You can see that if we can design the laminate stack appropriately that bladder molding would make the construction of a hollow wake surf board, fairly easy.

Thanks so much for following along, we really appreciate it.  We also are starting to see some pictures rolling in from the Koocanusa Wakesurf challenge, plus we want to share some from the sessions with Mitch and Chris.  Please be sure to check back soon!

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