Repair on a fiberglass hull

Discussion in 'Multihulls' started by Troyboi08, Oct 17, 2017.

  1. Troyboi08
    Joined: Oct 2017
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    Location: Texas

    Troyboi08 Junior Member

    My thing is I've seen what our river does to fiber glass hulls over time and would like to not Crack them open 8 miles from the ramp, or have to keep reapplying fiberglass patches to the hulls for the life of the boat.
  2. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    You can add glass to the inside or outside, other than that there's not much you can do to prevent damage.
  3. Troyboi08
    Joined: Oct 2017
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    Location: Texas

    Troyboi08 Junior Member

    Is there a glass product you recommend?
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I'm not sure what you're looking to accomplish, but there's no magic goo in a can that will solve your concerns. Gluvit is a "rebadged" product, which is another way of saying someone else makes it and they simply put a different label on it and charge more for it.

    'Glass is a fairly flexible and tough product, as used on most production boats. It does tend to get brittle with time and UV exposure. If you want it to be stiffer and stronger, you need more fabric, resin and likely more structure as well. There's no shortcut around this. You have choices in resins, fabrics and the engineering involved in reinforcements that will work, yet also keep weight down, which should be you biggest concern. The reason is, the hulls you're thinking about don't support much weight and if depressed much more than intended into the water, than their stock LWL, they'll be pretty darn draggy. This extra drag equates to needing a lot more power and reinforcement.

    Typical production hulls are designed to tolerate a specific amount of loading and impact. Beach cat hulls are designed to be light, not very heavily loaded, so they're thin and not heavily reinforced, say for slamming loads for example, as they'd really never see this in normal use. If you change their use, you need to address the appropriate things associated with this performance profile change. This means more longitudinal and athwart stiffness and strength, more fabrics, resin (of course) and a light superstructure.

    Fabric and resin choices abound, each having good and bad things to consider. You'd be best advised to access what you want from the boat, make up a reasonable weight study, so you know how much you need to support in a worst case scenario and work up from there. Next, once resin choices are made, you'll need to make up a laminate schedule to get the strength and stiffness desired, plus the superstructure. This can be all 'glass, all aluminum or just about any combination of materials you can think of. If you're on the cheap, wood and 'glass sheathing is likely the least expensive way to go. If you can afford it, selecting higher modulus materials can help, though you have to pay for it. For example, you can bulk up seams and the bottom of the keels with more 'glass and maybe a metal rub strip, which is a lot of work and several laminating secessions. Conversely, you could just use a strip of kevlar, down the centerline, but one layer of this will cost several times what the same thickness of regular 'glass does. Make a list of what you want the finished product to do and estimate (as accurately as practical) how much this might weigh full up. With this, you can address the options.
  5. Troyboi08
    Joined: Oct 2017
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    Location: Texas

    Troyboi08 Junior Member

    Ok, thank you for a comprehensive answer. That makes more sense now the way you put it
  6. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I would cut out the soft spots and see what you have; repair with suitable materials. Tricky. You can use the other hull as a mold if you make sure it will release. Then you take your molded pieces over to the repair and inset them. Someone here might have better tips on repairing sections this way.

    Then I would probably sand it all with 36 grit and glass it all with 6 oz and epoxy as long as it was fair enough to glass w/o bubbles. I might get some flack for epoxy over the gelcoat, but for some old hulls; I wouldn't start scraping gelcoat. It isn't a Riva or something special that will ever return money.

  7. guzzis3
    Joined: Nov 2009
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    Location: Brisbane

    guzzis3 Senior Member

    Are they really that soft ? Those old hobies were built like battleships, they were designed for people to thrash them though surf. I've got a pile of bits off them and you would expect to find the rudders and rigging on an 8-9 meter cruising cat.

    The problem with hobie hulls is no buoyancy. A H14 is designed to carry 2 light or 1 heavy person and a 16 maybe 3/2. I think it will sink before it breaks...

    I don't suppose there are any cheap bigger cats where you are ? Here you can pick up 18' and 20' beach cats with rotten tramps and sails for next to nothing, probably what you will spend on materials let alone labor...

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