Fiber orientation on hull?

Discussion in 'Boat Design' started by bntii, Sep 24, 2006.

  1. bntii
    Joined: Jun 2006
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    bntii Senior Member

    I am laying up some 1708 biax on a sailboat hull. Long story but for a repair the hull will get 100% coverage of one layer.
    I want to buy all the hull stiffening I can out of the fabric & am guessing that 45 degree fiber orientation from sheer is about right. This sound correct?

    Thanks
     
  2. frosh
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    frosh Senior Member

    Tell us more info!

    Hi, It sounds as if you are on the right track laying up the biaxial, however I would like to know the hull size, and the material and thickness of the hull skin, to enable me to give you more specific advice. :)
     
  3. bntii
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    bntii Senior Member

    Ah yes- an opportunity to talk about my boat:)

    She is any older 41' hull. Solid glass of about 3/8" at the sheer. I do not know how she is lain up but heavy roving is visible inside the hull. Deep keel, attached rudder, long overhangs, cutaway forefoot. Slab sided up high with no tumblehome.
    I need to peel the hull of all gel-coat, lay-up the 1708, fair and do a spray job w/Awlgrip. My position is just that if I am putting on glass, I would like to use to advantage as far as possible- hence the interest in fiber orientation to appose stress in hull.

    Thanks
     
  4. jonsailor
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    jonsailor Boat designer/builder

    Cloth styles

    If you have a Biax cloth (0-90) and you wish to lay it up at 45-45, why not buy a double bias cloth and this way, you can drape it from the shear down in one foull swoop and hey presto, no laps above the waterline and less fairing. We use a lot of Biax clothes as they test better for ABS 0-90 testing.
    However, we often interlay a double bias somewhere to help torsional loading.
    In your case, lay it where you like for the least amount of work and effort. You already have the primary hull strength in the original lay-up. Double Bias cloths are generally a flatter, better cloth and have less drainage than Biax clothes which seem to be more bunched in the piles so try to pick a good flat cloth and talk to someone about covering over your laminate with peel ply which helps drainage, eliminates pin holes and helps micro-cracking not to mention a better prepared surface for your next coat of whatever...

    My 2cents worth...happy glassing
     
  5. bntii
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    bntii Senior Member

    Thanks much,

    The cloth I am thinking of using is a double which is layed up like this on bolt:

    lXl

    The peel ply sounds like a good ideal as I have had to grind off the stitching thread other times I have used this cloth. Perhaps the peel ply would force the threads to lay flush?
    I keep picturing wearing big sheets of this epoxy soaked cloth like a hat as I fight to get it up on the hull :)

    T
     
  6. jonsailor
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    jonsailor Boat designer/builder

    Double Bias ahoy

    Well done, by chance, you have what I consider a better cloth being double bias (45-45) for drapability and flatness.
    you can tape it along your hull edge with masking tape on the edge and when you have almost wet it out by gentle roller and squeege, then remove the tape and wet out the remainder.....trust me it will stay there.
     
  7. frosh
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    frosh Senior Member

    I agree

    Hi, definitely go with double bias, at least 17 oz. It is the ideal orientation, and drapes very well, and you will need few joins.
     
  8. tom28571
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    tom28571 Senior Member

    And definitely use peelply or one of the synthetic cloths that work as well. Any slick finish, finely woven, synthetic material should work well. Takes a lot of work out of the leveling and finishing job.
     

  9. bntii
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    bntii Senior Member

    What says the collective mind on cloth weight?

    I am repairing gelcoat cracking.

    The boat has thick gelcoat in two layers and what looks like a thick layer of resin before you hit any glass on the hull. I took a look and the lay-up is just lots of heavy roving. The thick gelcoat and resin has lots of crazing. I am using a gelcoat peeler to cut off all the junk.

    I fought this battle once and lost. :mad:
    The first time a painter said I could bury the cracking under product and it would not print thru. So two coats of epoxy resin heat gunned into cracks, two coats of Awlgrip highbuild, two of 545 and topcoat.
    Looked great but a bit of sailing and the cracks printed thru.

    This time I'll cut down to get all the junk off and want a full cover of cloth for insurance that nothing will print thru. I was thinking of 1708 with 3oz mat over so 28oz total?? Most likely overkill... if I step down to 1208 & 3 oz over I have 22oz/yd total.

    Also Jonsailer- you would do all the wet out on the fabric taped to hull?

    I have done plenty of glass work but none of this sheeting fabric over whole hull stuff. I was thinking that I would wet out the fabric pieces on a sheet of plywood set on saw horses next to the hull. Pick up the weted out fabric and stick to hull, roll out etc??

    Thanks much all
     
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