Carbon Fiber Longboard

General Composites Discussions Composites Talk
#1

I have posted this question also on a longboard building site. Any help would be appreciated:

I want to fabricate a CF / foam core 46" pintail for my 16 y/o 105# daughter. I have some basic experience with CF wet lay up and vacuum bagging. I’ve previously made a BB core CR/Kevlar pintail and a full CF foam core skateboard off a gelcoat mold made from a bare skateboard. I used coremat foam which is a mistake as it is a resin sponge. I now have good double cut 1/4" Corecell 500 foam

I’m familiar with the basic techniques. I need advice from experienced CF fabricators.

(No, a 16 y/o does not need a CF composite board. It is a hobby. I like doing it and I want to make it for my daughter. )

I have a number of different fabrics available and she has her specific requests so some of the material choices (she likes texalium)will not make sense from a structural standpoint.

I want to fabricate a Texalium/3k towCF/Corecell 500 pintail, West systems 105/207 resin, wet lay up and vacuum bagged. The pintail “donor” board which I will make the gelcoat mold is moderate concave; neutral with regards to camber/rocker. In the area where the trucks are mounted the foam core will be cut out and replaced with a “forged composite” plate of the same thickness as the removed foam (“forged composite” of chopped CR and resin pressed and vacuumed.)

Questions:

  1. Is this board too long for her 5’4" 105 # frame. She is a relative novice.

  2. Should I use one layer of foam or stack two.? If I stack two should I put CF between the two? I’m concerned that one layer will be too thin and lose the stiffening effect of wider spaced CF. I’m equally concerned that two layes of 1/4’ foam will be too thick and therefore too stff. I have no other size foam available. This leads to question 3, number of layers and foam core:

  3. Foam and layers, options A, B, C

A. Tex
CF
0.25" Corecell
CF
Tex

B. Tex
CF
0.5" Corecell
CF
Tex

C.Tex
CF
0.25" corecell
CF
0.25" corecell
CF
Tex

C is thickest and stongest. But pretty thick overall compared to a wood board.

  1. I have researched many foam cores. Is Corecell a good choice?
  2. How much does concavity add to board stiffness?
  3. Do i need to reinforce the truck region with forged composite as I have noted above? I’m concerned that the corecell will deform or delaminate at these stress risers.
  4. Is this a enough CF considering I’m using texalium? (only four or five total layers)
  5. Will texalium conform to the mold with vacuum bagging? It is super stiff even before lay up. The corecell is stiff as well. If I cut the corecell well enough, can it function similar to a caul plate and aid in reducing voids?

I appreciate any suggestions.

Thanks

#2

I happen to run a carbon longboard company (www.sandwichtechboards.com) and you are off to a good start.

  1. A 46" deck is big…but what matters most is the wheelbase. Look at a Loaded Pintail (a very popular brand) for a good starting point for size/shape design.
  2. 2 ply of 1/4" is actually handy in that you can mold the core to pre-fit your mold’s concavity. You could probably use a resin slurry between the two, but I would use a really light glass ply for a good bond line.
  3. With a really long board the 1/2" will still be flexy, but if you shorten it a 3/8" core would be better. If you have a planer, just plane one sheet to 1/8" before laminating the core.
  4. Corecell is a great choice for a board that you want to have some flex because it has a high shear strain (the foam can bounce without failing at the surface).
  5. Not much because a cruiser deck doesnt have a whole lot of concave.
  6. We use stainless threaded inserts for all of our truck mounts (that is unusual though). Some foam core decks drill straight through the foam, then require truss head hardware to prevent crushing. A better solution is either lining the core holes with a metal or plastic, or using a piece of plywood in the core (many companies do this including LBL and 313).
  7. As for your layup, it really depends what weight & orientation the CF layer is. Save some $ on your first one and just use 19 or 22oz triax glass (its the industry standard and you wont see it anyway because of the Tex).
  8. A couple years ago we used black Tex on a line of boards and it capped fine. The trick is to design your board without any sharp corners and bevel your sides generously (we did 45deg on that design). Finally, break the obtuse edge on the bevel with some sandpaper to make the fabric’s job easy. If you corecell is pre-formed due to it being 2-ply, it will compress your lower layers fine.

For more info check out silverfish’s forums. It is longboard building central.

#3

Wow. Great advice. Thanks

#4

I actually have build a “wood” board with a corecell core. I’ve used the core in boatbuilding so I know the properties, but I was really amazed on how much it can handle after using it in a longboard(in combination with some of my heavier friends who flex the board a lot more than me)
Concave does add stiffnes, even a little bit is enough the notice it. the amount of stiffnes does offcourse depend on how much, at wich point, and the shape of the board. I would glue an insert in the core, foam doesn’t like compression. you can use wood, metal, or just drill some big holes and fill them with epoxy. In my board I didn’t use an insert, the 3 mm wood skins take the pressure fine.