Multi-density foam composite sandwich blanks

We’ve been bombarded of late with lots of hype. Have you heard the rhetorical expression “Lipstick on a pig”?

The superficial crap doesn’t change it from it’s true form, as a pig. Nothing wrong with pigs, mind you. But there is something wrong with trying to sell a pig as something other than what it is; a pig. We work hard at presenting only factual and truthful information about wakesurfing and our products and the equipment and products we use. That’s why we don’t edit our videos. We want you to see the action just as it happens. Sans lipstick. We just think it’s more respectful and honest, you know when you’re being hyped about the quality of a boat or it’s wake or a wakesurf board.

We’ve been working on a Lighter, stiffer, shorter wakesurf model that would allow us to use vacuum infusion. A few pictures and then some background discussion.

Here is the deck side of the board, or really a blank a multi-density foam composite sandwich blank, it’s not laminated on the exterior yet.

Here is a picture of the rail of the multi-density foam composite sandwich blank. There is still 1/2″ of material that needs to be glued on and shaped, so don’t worry about the SHARP shape.

Now, you know from following the Flyboy Wakesurf blog that all of our wakesurf boards are made from a composite sandwich. That is there is a core of a low density foam and then skins that are stiffer and stronger, at times we’ve used hogh density divinycell, as you can see in the pictures above of the multi-density foam composite sandwich blank.

Now infusion is an interesting process. It allows the builder to place all of the reinforcement material on the project dry and arrange it so that it’s perfectly placed before allowing any resin to touch it. Basically this gives the laminator unlimited time to arrange the reinforcement. Also, there is one additional thing. When the reinforcement is finally wet out, it’s already compacted or consolidated. That is, it’s pressed down and is thinner than when it comes off the roll. So when the resin is applied, less is needed than with a hand lamination or even with a vacuum bag.

The down side though is that in our sandwich construction, how the heck do you get to the inside layers of reinforcement!!!!

One way is the skins have perforations and thin vertical slices in a grid to aid the flow of resin between the core and skins. The issue with that is the the holes and slices then fill with resin, adding unneccessary weight. So you save some on the weight with the compressed reinforcement and just transfer that weight to the holes and slices! We’re still working with the idea, because we love the idea of adding more reinforcement material for the same weight, but we aren’t quite there yet! See no lipstick on a pig! We just tell you what it is and what we’re working on.  What we were hoping in this build, was that by omitting the extra rail material, we could gain access to the layers of reinforcement under the skins and that the infusion process would pull resin UNDER the skin and through that reinforcement layer.  We’re not sure if that will actually work, but we were able to expose the layer of reinforcement, by omitting the last few layers of rail material.  It doesn’t really allow us to fully laminate the exterior AND interior, but it’s a start!

BUT, as we looked at this structure, we decided to lay up two layers of 3 oz Carbon Fiber and a patch of 3 oz Kevlar. It is under the deck skin, and man is that structure stiff! So then we started thinking about a multi-density blank. We’d still have a composite sandwich, but rather than using the 3 layers of reinforcement under the deck skin, we started thinking of a core that had a higher density foam on the deck side, say about 3/8″ deep. Not a full 5 pound density, but say a 3 pound density on top of the 1 pound density. It would offer a level of increased stiffness and also help resist compression forces.

There is one more concept we want to talk about and it is the neutral axis. It’s an imaginary line in the center of the core of a composite sandwich where the forces switch from compression to tension. That is to say that the deck side of a wakesurf board is in compression, but the bottom is in tension. Somewhere in the middle it changes from compression to tension and that point of change is the neutral axis.

What would be the very best arrangement for the thickness and location of this deckside higher density foam core is from the bottom of the deck skin to the very tippy-top of the neutral axis. Where is that point? We don’t know! Anyway, that will lead us to some testing and test panels!  Not as exciting as landing a surf style big spin, but still fun!

Thanks so much for following along, we do appreciate it.

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