Hi everyone!

As a product designer, I have always been interested in building with carbon fiber. I recently purchased a 3D printer and me and my friend came up with the idea to print molds and use them to make carbon fiber parts. We came up with the idea to make a cruiser skateboard using hand lay-up and vacuumbagging. (Similar to this video: https://www.youtube.com/watch?v=scvXKij1hQ0) 
A cruiser rides like a longboard. But in contrast to longboards, skateboard cruisers are shorter and more maneuverable. There are usually made out of plastic and very flexibel which provides an easy and surfy ride.


Since this is the first time we try this, I prefer some feedback on what we have planned. I still have some open questions. Please let me know if you have any comments, tips & tricks or links to usefull literature or videos. Anything is welcome!
I have the following in mind:

1. Mold making
I use my Prusa i3 MK3S to make a mold out of PLA filament. The mold will be printed in 3-4 pieces because the printbed is not big enough. I will glue/bolt the pieces together and use a filler and sanding-paper to make the inside smooth. (any recommendation for the filler?)

2. Reinforcement
I would like the board to have a nice flexibility to it. You should be able to jump on the board with your full weight and nearly hit the ground. Also bend it pretty hard in sharp turns which results in high torsional forces. There are a lot of parameters which can influence the flexibility. I hope you can help me choosing the right epoxy and reinforcement layers to help me in the right direction. After that I can still play with other parameters like the thickness of the foam inlay or adding ribs on the bottom to fine-tune the flexibility. 

I did some research and came up with the following lay-up:

1st layer  - 210g 2x2 Twill 3k Carbon Fibre
2nd layer - 300g /- 45 Biaxial 3k Carbon Fibre
3rd layer - Foam inlay 
4th layer - 300g /- 45 Biaxial 3k Carbon Fibre
5th layer - 210g 2x2 Twill 3k Carbon Fibre

I was planning to add unidirectional fiber in the length of the board between layer 1&2 + 4&5 but I'm afraid the board will get too stiff, any suggestions?

3. Epoxy
I'm not sure which epoxy I should choose. EL2 Epoxy Laminating Resin or XCR Epoxy Coating Resin? Which one would be more preferable to achieve the flexibility I want. 

4. Vacuumbagging
I'm planning to use the Vacuum Bagging Starter Kit provided by Easycomposites

Please let me know what you think!

Kind regards

Hi,

Looks like a fun project; happy to chip in a few suggestions from the EC side:

One thing I'm not sure on, from your description, is exactly which part of the board shape you will be forming with the mould? - Looking at the example deck you included a picture of it has moulded detail on the top (the cross-crossed grip pattern) and moulded detail on the bottom. When you say you plan to 3D print the mould, could you elaborate on that a bit? - For example:
1. Is it definitely the mould that you'll be printing, not a pattern which you'll then take a mould off?
2. Will you be making a mould for the top or the bottom, or both?

I'll make a couple of assumptions on the above that your plan is to 3D print the mould (not a pattern) and that you'll be printing the top face and not the bottom. On that basis, the first thing I would suggest would be for you to 3D print a pattern (i.e. the shape of the top deck) and not the 'negative' mould. 3D prints can be quite flimsy and since you're printing in at least 3 sections and then fitting them together (and filling) then you've got a bit of work to do to turn your 3D print into something worthy of moulding from. My experience is that you would find it easier in the long run to print the male, glue the sections together, fill, fettle and finish (Pattern-Coat Primer) that pattern and then bead it down (filleting wax) to a flat board (polypropylene sheet) and then take a proper mould off that upper deck pattern (chemical release agent, something like the Uni-Mould system for the mould). By doing do you can get a really good finish on the pattern and you'll also have a really flat, solid mould (that you can improve further if needed) with good flanges on. Because the top mould stays the same no matter what layup or bottom ribs etc. you go for you can keep using that same top mould to make hundreds of different boards if you want, all with quite different behaviour, all using that same mould.

When it comes to making the deck itself, whilst you absolutely could use the vacuum bagging process, my personal recommendation would be to use the resin infusion process. You've probably already seen our resin infused longboard deck video tutorial. Once you have the mould for your top deck, most of the rest of my recommended process would be the same as that tutorial. Resin infusion will give you more reliably good results than vacuum bagging will, and also opens up some interesting core options, like 3D core.

You're absolutely right about the different reinforcements and layups changing the handling and flex of the board, they really will. Thankfully, the material cost in a skateboard deck is quite modest and once you have a good mould you will be able to experiment with a few different layups until you find the combination of reinforcements and core that you like the best. It sounds like you already know the basics:

• UD down the length of the board will give you less longitudinal flex (make it belly-out less)
• +/- 45 Biaxial will give you torsional stiffness (stop the board from twisting)
• Woven cloth oriented at 0,90 will give you 50/50 between longitudinal stiffness and lateral stiffness.
• Core materials will have a huge impact, particularly the thickness of the core. Adding a few extra millimetres of core will make the reinforcements either side work so much harder and add a lot more stiffness to the board than extra reinforcement will.

For your core materials, I would think about: plywood, balsa, 3D core, closed cell foam. There are also lots of others that would work too.

If you wanted a 'get me started' layup, you could go with:

• 210g 2x2 twill 3k carbon fibre
• 250g undirectional carbon fibre
• 5mm birch plywood (drilled and grooved or slotted to allow infusion)
• 250g undirectional carbon fibre
• 210g 2x2 twill 3k carbon fibre

Infused using IN2 Epoxy Infusion Resin

After that, give it a ride, see how you like it. You've got a million different levers you can then pull to adjust the ride (change the core, add more reinforcement, add ribs to the bottom etc.)

I hope this helps and that you have fun with the project. I know that making a proper mould sounds like extra work but because you need the same mould no matter what layup you go for I think it's well worth getting that bit right from the start; you'll find the rest of the project so much easier (and more successful) if you have a good, solid mould to work with.

All the best, Matt


Matt Statham
Easy Composites / Carbon Mods - Technical Sales

5mm birch plywood with ud and 0/90 weave on both sides will definitely not result in anything "with a nice flex". At least not for such a small board. If you want to use a core and want the board to be so flexible that you almost can touch the ground (and want it to made out of carbon fibre), I would recommend to not use any fibres at 0°. So no ud and no woven cloth at 0/90. I would start with 500-600 g/m^2 cloth at 45/-45 on each side of the core. Theresin will be several tries to find the right layup.