Carbon/graphite, Kevlar or Glass

Discussion in 'Boat Design' started by BobBill, May 14, 2012.

  1. BobBill
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    BobBill Senior Member

    Two questions...

    What would be best to stiffen a windsurfing mast, (which will be inserted into Force 5 bottom section) carbon, a mix of carbon and glass or Kevlar or Kevlar Carbon mix?


    What would be best material to use to beef up gudgeon area of transom...?


    I have checked the WWW but I do trust the mentors here more than all others.
     
  2. Paul B

    Paul B Previous Member

    Carbon Unis will give you a greater increase in longitudinal stiffness than any of your other choices.
     
  3. garydierking
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    garydierking Senior Member

    Carbon would be the best for sure, but the bigger problem is the resin. Windsurf masts are post cured at elevated temperatures to become as stiff as they are. Repairs I have done with room temperature resin do not last. You'll need the right epoxy and a way to heat it up for a full cure.
     
  4. BobBill
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    BobBill Senior Member

    Hey, thanks. I bought your book on construction of three outriggers...love it, learned lots. It sits atop all books in my loo...place of daily research and so on. In fact, it is sitting next to me now but I am not in loo:] .


    Project is a redo to the venerable Malibu Outrigger...but in the meantime, using the carbon to redo the w-surfing spars on refurbished Kite Class Dinghy, so I can use current Force 5 and Laser sleeve sails...way cheaper and more efficient...

    Now, your above observation is interesting. I figured my plain old goo would do it...now I have to search out a specialized epoxy...suggestions?


    I was leaning toward glass, afraid carbon would be easily damaged...have to rethink...

    The heating would be easy with a bank of incandescent lights...or sun lamp bulbs.

    Appreciate the advice and the fact it came before the fact...
     
  5. messabout
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    messabout Senior Member

    I wanted to stiffen a windsurfer mast to be more appropriate for the non windsurfer sail that it was to carry. The sail, a sprit boomed 60 square footer did not want all that bend, particularly at the snotter location. Yeah I know that the combination of modern mast and nineteenth century sail was/is incongruent....It works however.

    I had no problem at all with ordinary epoxy and ambient temperature cure. I did sand the recieving surface carefully but that was all the special prep that I did. No problem with adhesion so far.

    Seems to me that if you plan to use a Laser sail, it would be good to use a standard Laser mast and avoid all the hassel with inventing your own stick.
     
  6. BobBill
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    BobBill Senior Member

    Am leaning toward using normal epoxy etc. as you noted.

    I had thought about it just the way you did, but ran across a deal on a Force 5 spar set and took it...

    Now I can use the refurbished wood mast ($1k new) but the orig sail is shot, so I can use the aluminum Force 5 set or the carbon combo, which is sort of experiment, using just the base of the 5 set with either Force 5 or Laser sails.

    BTW, I stayed away from the Laser spars as they are renowned for taking a set, the 5 deal notwithstanding.

    All I really had to do as raise the bottom a bit so the vang would clear the iron that hold the mast in the step...which I did by laminating some white oak and then shaping to fit into the base. Pic is not my boat, to give idea...

    All I really have to do to the spars is add the graphite spine, plug the tip and maybe foam the end, add the rubber rings and set it in place. No holes etc, as they are all in the 5 metal base...the boom might be trickier, but not bad.
     

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  7. BobBill
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    BobBill Senior Member

    I have acquired two slightly used and base damaged 100 percent carbon windsurfer masts...North Platinum...so it take it uni tape up the length should do the trick?
     
  8. m3mm0s rib
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    m3mm0s rib Senior Member

    Carbon no doubt. Is the best
     
  9. BobBill
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    BobBill Senior Member

    Bow-side or stern-side. Uni-directional or omni? Thinking the latter, using on both.
     
  10. PAR
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    PAR Yacht Designer/Builder

  11. JRD
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    JRD Senior Member

    BB, you can get biaxial carbon sock. That way you can get the spiral wrap that goes both ways and it will be nice and even. Do you have access to a vacuum pump to bag it on? If not I sugest wrapping it in peel ply then using packaging tape to bind it, then you can be sure of proper consolidation and any excess resin will be soaked up by the peel ply. You dont want dry spots or voids with a mast, even if you are only reinforcing it. I have just beefed up a carbon fibre/glass tube for a mast post, using the vacuum bag method, though I didnt have the sleeve material so I made do with a layer each of uni and cloth.

    http://www.solarcomposites.com/composites/carbon fiber sleeves.html
     

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  12. BobBill
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    BobBill Senior Member

    I new about sleeves and forgot about it...maybe roll up like a sock and unroll on mast...have not planned to vacuum, though. I just need to stiffen the spar a bit.

    It will be split where the upper/lower section ferrule.
     
  13. PAR
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    PAR Yacht Designer/Builder

    Socks are hard to work with, I'd just use a unidi in both directions (spiral wrap) or a biax. The peel ply, wrapped with shrink wrap or polyethylene sheeting will do a good job of mashing down the goo and fabric, saving the need for a pump.
     
  14. JRD
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    JRD Senior Member

    I have used it in short lengths and it was Ok but I can appreciate it would take some care for longer applications.

    BB - The important thing to stress is the consolidation (Mashing as described by PAR). Being the outer fibres they will be the most stressed and will undergo the most movement in tension and compression. Even if you are just using it to stiffen things up, the carbon you apply will assume most of the load, particularly if the existing mast has a high % of fibreglass in its laminate.
     

  15. BobBill
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    BobBill Senior Member

    Par, thanks as always. Will likely do as suggested.

    I have no idea how each layer would affect mast bent, so was planning to do strips up one side and the other, depending on deflection (using original mast as guide, weighted with 50 lbs of something.

    Then add as needed, starting a bit below where the bend is too much.

    Spiral would work as well...
     
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