• 7th July 2005 - By greg

    July 7

    July 7, 2005

    Carbon sandwich board frame fabrication begins

    Let me briefly explain again how this frame is going to be built. I am going to build a sandwich board using a 1.5″ thick slab of styrofoam covered with two layers of 5.8 oz twill weave carbon fiber fabric. After the carbon is dully cured, I am going to trace the outline of the frame then cut it out with a jig saw. Then I will add more carbon to the exposed foam edges, and additional carbon layers around areas where the components bolt on, and areas that required extra structure.

    This is the basic frame shape:

    These are the areas that will require additional carbon laminations (aside from components):

    My good friend and carbon frame expert Eric Krueger from BenderBikes has been guiding me through this somewhat strange new territory.

    The carbon sandwich board is finished and it looks GREAT! I can’t believe how strong it seems and it doesn’t even have any of the additional carbon laminate layers yet. I can set this 1.5″ thick piece of styrofoam up on two sets of blocks and STAND in the middle of it (like a bridge) and it barely flexes at all!!

    John Mackay pulling off the breather blanket after vacuum bagging

    Here are the details of the process so far:

    1. IĀ built a 3 foot x 12 foot table top that is completely FLAT and level to build the carbon board on to ensure that the frame is perfectly flat.My helpers for two days were John Mackay and Ben Eadie. I could not have finished this without their help, as this definitely was a 3 man job!!
    2. Since styrofoam only comes in 8 foot sheets, I had to cut and join two sheets together to form a 30″ x 120″ board. I used epoxy resin with quick cure catalyst to bond them together and it worked really good.Krista is pin-pricking the edges of the foam slabs the resin used to join them together is absorbed a bit by the foam.
    3. John and Ben squeegee the epoxy resin over the double layer of 5.8 oz carbon twill.We decided to only do one side at a time – that is, to layup one side only, then bag it and let it fully sure before doing the other side.
    4. I decided to use some heavy poly as the vacuum bag material rather than the way more expensive vacuum bag film. We had built the bag before hand, but realized that we had better test the bag to be sure that the poly could hold a vacuum before proceeding.I shoved a spare piece of foam into the bag and sealed it up only to realize that I had forgotten the breather blanket. So I crawled back into the bag to push the blanket all the way to the top.

    The poly worked fine.

    5. Here is the foam board in the bad ready to be sealed.
    6. To keep the sandwich board flat while under vacuum, we placed this 3/4″ thick plywood sheet on top.
    7. This shows the vacuum tube entering the bag through a hole we drilled in the plywood top.
    8. The plywood top was covered with weights to ensure that it stayed flat.
    9. The next morning we pulled it out of the bag, and pulled off the peel ply / breather blanket layer revealing a very flat and hard carbon surface.Then we repeated the process for the other side.
    10. When the other side had cured, I let the board sit out in the sun all day for a post cure. Within a minute of exposure to the sun, the surface of the carbon was almost too hot to touch!

    Now I will wait until the MDF mold is finished before tracing the frame outline just to be doubly certain that the frame is EXACTLY the same shape as the fairing.

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