Carbon mast repair

Discussion in 'Sailboats' started by Tiny, Aug 9, 2009.

  1. Tiny
    Joined: Jan 2009
    Posts: 10
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: UK

    Tiny Junior Member

    The question is, is my carbon dinghy mast repairable?

    I dont plan to win the nationals. I cant afford a new one.

    It 4.5m long, 52mm ID, 56mm OD. It carries a main, jib and symmetric spinnaker, no trapeze.

    The mast's construction is:
    200g Twill
    160g Plain weave
    400 g Uni spiral
    160g Plainweave
    400g Uni spiral
    400 g Uni, longitudinal + 1" wide longitudinal uni at leading edge
    200g twill

    Two clean breaks, one at the jib halyard, one about half way up, about two meters apart. At this point I thought, yeah no problem. However, I found another fracture in between at the spreaders. 0.8 meters from one break, 1.2 from the other.

    Repair method was to be:
    Machine ends square.
    Machine back one layer at a time, so that we have in effect a stepped scarf over about 150 mm on each side of the break, i.e each layer exposed for about 30mm. Like this rubbish diagram below.

    _____
    TW__|__
    UD_____|__
    UD________|__
    PW__________|__
    UD_____________|___
    PW________________|
    TW________________|

    Align the two bit ins a big, straight piece of aluminium angle
    Wrap some wetted 600g quad glass around an inflatable bag, then blow the bag up inside the mast, to effectively tack the two halves together inside with something bendier than carbon. Let this cure.
    Lay up exactly the same carbon over the scarf as was removed. Using peel ply, bleed film, bleeder cloth and shrink tape to consolidate. Apply heat.

    Do this for each of three breaks.

    Re varnish the mast.

    Go sailing and hope for the best.

    Am I kidding myself that this will work?
     
  2. gggGuest
    Joined: Feb 2005
    Posts: 808
    Likes: 17, Points: 18, Legacy Rep: 76
    Location: UK

    gggGuest ...

    Probably easier to sleeve it with some tube of the same wall thickness or better still marginally more.. Carbon sticks are repaired regularly, its not that unusual.
     
  3. fng
    Joined: Feb 2009
    Posts: 57
    Likes: 3, Points: 8, Legacy Rep: 46
    Location: new zealand

    fng Junior Member

    If you are going to glass patch the mast as you have discribed you could sleave the mast internally with a thinner wall tube than you current section.

    basically glue the tubes together, when dry machine or grind you tapers for the repair laninates and glass it. use a minumin lap of 30mmfor each layer.

    shrink tape or vaccum bagged would be ideal, but if you don,t have access to these you could wrap the repair tightly with an over length strip of peel ply and possibly masking tape on top of that.

    you will need to be carefull you glass job isn't to wet with resin or it to will spiral with the wrapping process
     

  4. Tiny
    Joined: Jan 2009
    Posts: 10
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: UK

    Tiny Junior Member

    Just to clarify, I was only planning to glass on the inside of the mast, where there was originally no carbon, making the section slightly thicker in that area. The idea being, some additional strength, something to layup replacement material on, but without making it locally appreciably stiffer.

    Elsewhere, to replace carbon with carbon, as exactly as possible to the original layup. I am slightly worried about discontinuity when effectively butt joining layers of uni carbon which were originally continuous fibers. I'm hoping that my
    additional layer of glass quad-axial glass on the inside sufficiently compensates for this. But I dont know.??

    I have already machined each layer back by 30mm, successively, except the inner two, which flex too much to grind back to a single layer.
     
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