Any carbon fiber experts out there?

Discussion in 'Recumbent bicycles' started by tyler_derden, Nov 10, 2004.

  1. tyler_derden

    tyler_derden New Member

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    I've been drooling over Velocraft's and a bunch of other carbon fiber low racers I've seen on the web for a while now and I'm starting to get that old familiar itch to try to put something together. First I'm interested in building a front-wheel-drive, low, but semi-upright seat commuter/touring bike with a u-joint above the steerer tube to decouple the steering and propulsion.

    Does anyone out there know anything about carbon fiber construction techniques as they would apply to recumbent bike frames? I'm also looking for any literature or web sites that explain the hows and whys and whats of carbon fiber construction.

    I have been to this site many times: carbon! and it has been a big inspiration and source of info, but I need MORE!

    Thanks,

    TD
     
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  2. Johnny NoCom

    Johnny NoCom New Member

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    The best CF construction method to date is bladder construction with a female mold formed from a male plug to control the amount of epoxy resin in the CF.

    Buy some books to learn. You will need woodworking tools to create the wooden plug and mold, a vacuum bagging system and assorted slow set resin, kevlar with CF for lay-up and an oven to cure the resin.

    Don't bother with wrapping CF over foam. That is a weak construction method that produces a uncontrolled surface with too much resin.

    Cheers,
    Johnny NoCom

     
  3. skydive69

    skydive69 New Member

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    Do you happen to know what the best way of touching up carbon fiber is? I have some scratches on one of my forks. My frame is not clearcoated - it is dull CF.
     
  4. Johnny NoCom

    Johnny NoCom New Member

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    Once a dull or glossy surface is scratched it is not easy to bring it back to the original quality. Here is a suggestion.

    For a dull finish you can use a simple method like spraying a matte finish sealer over the scratches in VERY light coats. Too heavy of a coat and the spray will pool up on the surface. Craft an hobby stores sell cans of matte finish sealer.

    Cheers,
    Johnny NoCom



     
  5. skydive69

    skydive69 New Member

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    Thanks for the info Johnny!

    Sandy
     
  6. PaPa

    PaPa New Member

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    "the best" is clearly subjective. Ease of construction and cost effective designs such as the Calfee Stiletto, and Lug-and-glue df's like the high-end Merlin Cielo, are examples of efficient cf construction. For homebuilders and one-off prototypes, molds and "bladder construction" is usually cost prohibitive and time consuming.
     
  7. Johnny NoCom

    Johnny NoCom New Member

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    The following recumbents do not use lug-and-glue construction

    M5 CLR
    Birk Comet
    Merlin LR
    Cobra Splitter
    RazFaz
    VK NoCom Splitter

    The Comet, Merlin, RazFazz and VK all incorporate bladder construction and have the highest strength ratio as a result. Bladder construction is time consuming and provides the best result for a complete CF with low weight.

    If the goal is quick and cheap it is best to bend a muffler pipe for the frame, weld 2nd hand bicycle frames or do a lug and glue construction with carbon. The end result will never be the same as a bladder construction frame.

    Cheers,
    Johnny NoCom




     
  8. Johnny NoCom

    Johnny NoCom New Member

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    This HPV racer & builder works with carbon fiber add ons made with foam and CF. He also has some CF bikes built from scratch

    http://community.webshots.com/album/215777603vAaGEk

    This latest bike is a speed missile and faster than a Stiletto with baloney bubble fairing or old school design Baron.


    Cheers,
    Johnny NoCom
     
  9. PaPa

    PaPa New Member

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    By what pool, does your vast wisdom speak? Your a builder.. or... a structural engineer perhaps? And therefor qualified to say what is "the best" cf construction method for ALL designs? YES.. or NO? If not, your words are nothing more than personal speculation... and "pass the buck" links.

    Oh really?... So tell me, what construction technique did the fastest bike on the planet employ for its cf frame?
     
  10. Johnny NoCom

    Johnny NoCom New Member

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    PePe,
    The fastest bike on the planet is the Varna which incorporated the male and female mold build system. No hack builder lug junk on that beauty. George Georgiev did not do the quick, cheap and easy build that most benters are satisfied with.

    Cheers,
    Johnny NoCom

     
  11. PaPa

    PaPa New Member

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    Where's your bio?

    Here we go again.... All talk and *appearently*... NO personal *hands-on* experience or design qualifications.
     
  12. Johnny NoCom

    Johnny NoCom New Member

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    PePe,
    I suggest you go to this site to learn something.
    http://www.kreuzotter.de/

    Obviously you are in a coma and you have no clue to bladder construction or what builders have been using the bladder system. My guess is you ride some lugged TourEasy for the easy lifestyle of slow riding.

    Cheers,
    Johnny NoCom

     
  13. PaPa

    PaPa New Member

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    More LINKS.... and no substance. All you *obviously* possess is a keyboard and the ability to cut'n paste.

    Where's the beef Johnny NoCome?
     
  14. Johnny NoCom

    Johnny NoCom New Member

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    Like it or not PePe I know quite a bit about construction techniques. All building procedures have pros and cons. If a builder is going to do it right and design/build a frame that takes advantage of smooth complex surface and light weight, the bladder construction process is the best system to date.

    On the other hand if the goal is to build something ordinary or copied that is used for for slow paced recreational riding any build method will work.

    Cheers,
    Johnny NoCom




     
  15. PaPa

    PaPa New Member

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    And I know the difference between a digitally, self-taught phoney, and someone with last nights epoxy under his/her finger nails.

    Cheers
     
  16. Johnny NoCom

    Johnny NoCom New Member

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    PePe,
    Have you welded any dumpster frames lately? Lot of spare lugs on those things. Maybe you can wrap some CF around one of your hack builds and post some photos at http://www.liegerad.de/

    BTW, I suggest you read the first post in this thread:
    "I've been drooling over Velocraft's and a bunch of other carbon fiber low racers I've seen on the web for a while now and I'm starting to get that old familiar itch to try to put something together."

    FWIW PePe, VeloKraft recumbents are bladder constructed. If the goal is to build something similar the builder has to put the time in and learn how to build with the same process. VKs are not lugged like DF frames.


    Cheers,
    Johnny NoCom

     
  17. tyler_derden

    tyler_derden New Member

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    Getting back to the subject of this thread, I have some questions for anyone EXPERIENCED with vacuum bagging of composite lay-ups.

    I have a small diaphragm-type vacuum pump that I plan to use. I selected it over a rotary vane type pump for quiet operation and apparently adequate vacuum draw (22 inHg). The capacity is small, but for small stuff like bike frames I think it will be OK.

    Questions:
    1) does the pump need to run continuously or can it be turned off after the air has been drawn from the bag?
    2) do I need to use a vapor/fume trap at the input side of the pump to protect it from epoxy vapors or is it generally not a problem?
    3) what other little pneumatic stuff should I accumulate- valves? gauges, regulators, etc.?
    4) can a pressure regulator be used in reverse to regulate vacuum?
    5) I will try using a blue foam core at least initially. How does that stuff hold up under vacuum, or does it?

    Finally, I was originally thinking that summer would be a better time to work on this stuff, but then I realized that the epoxy won't cure very quickly in cold temperatures, giving more working time. I plan to make a curing "oven" from either blue foam or cardboard boxes and put a heater inside. I figure once the lay-up is done and the bag pumped down and sealed properly I can then put it into the oven to cure. Is this a reasonable approach or am I missing something?

    That's all for now...

    Thanks,

    TD
     
  18. Johnny NoCom

    Johnny NoCom New Member

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    1) The pump runs continuously with the vacuum bag under a heat source till the epoxy resin is cured.

    2) No. You will need to work in a ventilated work space.

    3) A regulator to know the appropriate PSI for the weight/strength ratio.

    4) There are vacuum pumps made specifically for bagging that include a regulator.

    5) Blue foam will get crushed by the vacuum bag. Hence the reason for sculpting a hard surface plug and making a mold.

    You will have better luck curing CF in warm temps. If you work with the bladder method you will not have to use a compressor as the bladder pressure will compress the CF into the mold. Both bagging and bladder are used for some CF recumbent frame production.

    Have a fire extinguisher on hand if you intend to use a cardboard oven.

    Cheers,
    Johnny NoCom


     
  19. PaPa

    PaPa New Member

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  20. Johnny NoCom

    Johnny NoCom New Member

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