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Carbon Fiber

Discussion in 'Tech' started by prm, Jun 29, 2022.

  1. prm

    prm Well-Known Member

    I have an extra seat for my 890 and I want to make it into a race seat. Using the base and building up a shape to then adhere race seat foam is my initial plan. If I use something like foam to create the shape, how many layers of carbon fiber would be required to make it solid enough? Is this a viable plan, are there better methods?
     
  2. prm

    prm Well-Known Member

    Roughed in the shape. Plan to add a 3mm thick carbon fiber sheet to the base (shaped to yellow outline), then start applying regular layers of CF to build the curves and wrap around the edges. Will secure CF sheet to base with a few rivets. Maybe some epoxy too, but not sure the epoxy will bond to that plastic very well. I’ll add some 10mm seat foam to the top once its shaped. The foam will generally follow the yellow outline as well. 20191601-DA36-411B-B7DC-D0E6F3DA511C.jpeg
    8BE51780-628F-4522-82D8-0CB947AEBDAB.jpeg
     
    Phl218 likes this.
  3. metricdevilmoto

    metricdevilmoto Just forking around

    There's a ridiculously expensive race seat available from KTM Power parts that was previously backordered into oblivion we just got in for a build.
     
  4. prm

    prm Well-Known Member

    I waited for a long time for them to be available and got tired of waiting. And yes, ridiculously expensive for the few (in Europe) I could find. After looking at pics of bikes I decided to use the extra seat I had for a test. No idea if it will work out, but I hope to get rid of the squishy feeling of a street seat and get a lower seat height too. Short legs …
     
  5. Somewhat of a loaded question as it depends. Personally I’d not use carbon sheets but make a proper one off pan. Since this is just a pan you can get away with doing a simple wet layup in carbon. You could even get away with covering the base (something like this vinyl wrap works well but masking tape will work too). This will make it “flat enough” then just do a wet layup over that. This will probably be same cost if not less than your plan and give you what you want. Or go next level and make a plug, then a mold and use infusion to make a nice one. Or go the pre preg route and have a seat pan that cost more than your bike by the time you get all the stuff together :)
     
  6. I don’t understand the need for the carbon sheet though if you are laying carbon on it. You are actually making a weaker seat as you won’t have as good of a bond with carbon you are laying over plus the main thing of the strength of the carbon itself. More I think about this you could use the base as a “mold” of sorts. Lay a couple layers to use the grooves to locate it. Have some strips of foam ready to fill in the ups and downs and then lay carbon on top. Balsa or a light wood would work too. If I had time this would be a cool project I’d way overdue and spend too much time on but would have a bad ass seat pan. I did something very similar last year for a buddies sons hand cycle. He has no legs so we had to make a semi custom pan based off existing and above it what I did. The seat had to be covered with foam (jet ski foam was used) because of abrasion to his skin. If it was to be raw exposed carbon I’d have either added a couple layers over too and infused it or make a plug and mold to make it look pretty. We’ve actually modified this a couple times as more he cycles more tweaks we make to get him more comfortable.
     
    prm likes this.
  7. prm

    prm Well-Known Member

    The carbon sheet is just to build up the center area which is slightly lower. I considered other materials but thought a sheet, only 3mm thick, would be both light and stiff. I plan to do the wet layup over that. Once the layup is complete, I will have five bolts, ~flush on top, through pan to hold it all solid.

    In hindsight, I probably don’t need to build up the center as the seat foam would just sit in that lower area and be tall enough to be above sides. The sheet will make that entire area smooth though.

    Making a new pan is way above my skill level! I need simple!

    In your experience, how thick (layers) does the carbon fiber need to be for a seat pan? There will be a few unsupported gaps under the layup where it curves down on the sides.
     
  8. prm

    prm Well-Known Member

  9. TLR67

    TLR67 Well-Known Member

  10. -Eric-

    -Eric- Well-Known Member

    Do a search on YouTube for a channel called Easy Composites. They have a lot of tutorial videos with all kinds of projects including lots of ways to get good results at home without an autoclave. They sell kits too with all the materials you'd need but being based in the UK shipping gets expensive.
     
    tophyr, Phl218 and backho like this.
  11. backho

    backho Well-Known Member

    Their tutorial videos are great!
     
  12. prm

    prm Well-Known Member

    Coming along… Definitely a learning process, but it’s going to work. This is after the first two layers. Pieces I had were not big enough to cover it all at once, so two across and two lengthwise. Ordered bigger section to add a single layer. Wrapping tightly around bottom edge is the hardest part. Have some ideas of how to do better with final layer. For now, I’ll cut off excess, sand, new layer of resin, sand, repeat until smooth, then add top layer.

    C4221252-FCF3-46FC-8575-87B582134FDA.jpeg
     
    MachineR1 likes this.
  13. Busdriver02

    Busdriver02 Well-Known Member

    I'm not really sure how thick you plan to make this thing, and this is about to be some late info for you:

    Get a sheet of pink insulation board. Chop it into pieces that you can glue together to get the right volume. Shape that block of foam to fill in the area of the seat, and get to your final shape, fitted to the pan. Then use some plastic spreaders and put down a thin layer of resin (or bondo if you have that laying around). Sand to key it up after curing. That first layer is just to keep the wet lay up from soaking into the foam, which will use up extra resin. Then spread on a layer of resin. Drop a layer of cloth. Use the spreader (a small plastic roller is better) to push the resin up from the underside of the cloth layer. Then another layer of resin, then cloth and repeat. Four layers should be plenty.

    Based on what you've already done, you can key up what you have, add the foam to get to desired thickness, then add the top layers of cloth to finish.

    Alternatively, if that minicell foam is similar to an EVA yoga block, that foam is very dense. You could glue on a 2 inch thick layer of that and be good.
     
  14. prm

    prm Well-Known Member

    Thanks, definitely taking notes for the future. This one is essentially as built up as it will get. I will add a couple more coats of resin sanding in between just to get is smoothed out. Then one more layer of carbon fiber. I have a 12mm foam pad on the way. I want this seat low.
    First look after trimming some excess and rough sanding.

    C0C479E9-96D2-407A-B571-58E0671B0B73.jpeg
     
    Sudowoodo likes this.
  15. Loaded question as it depends on how good you lay it up. If doing simple with some support under maybe 5-6 layed properly direction and resin wise. I always go a bit overkill though. I’d seriously lay down a few layers of carbon, foam core the “grooves” and lay 4-7 layers on top. This is assuming it’s not a massive resin dump and layed properly.
     
  16. Ok didn’t scroll down enough. Looks good and you’ll learn more every time, as said above by someone else, foam is a lifesaver and let it fill,the gap and the carbon do the work.
     
  17. prm

    prm Well-Known Member

    372711E0-0FB7-48B0-8EA1-E8F8907EA7A0.jpeg Well, I’m pleased for a first attempt. Perfectly functional, with just some minor cosmetic issues. Look forward to trying at the track. Quite a bit narrower and lower. F978D036-67B0-47FB-9804-AF65E21E32A3.jpeg
     
    IL8APEX, sdg, Sudowoodo and 1 other person like this.
  18. Nice work for relatively first time, gets easier more you do it.
     
    prm likes this.
  19. prm

    prm Well-Known Member

    Slight mod. Not sure I’ll stick with this thicker pad.
    3AEA28B9-E49D-4931-9E5A-D987AD5D8559.jpeg
     
    sdg likes this.

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