Layup recomendations 8' dinghy

Discussion in 'Fiberglass and Composite Boat Building' started by dan catalyst, Aug 7, 2013.

  1. dan catalyst
    Joined: Aug 2012
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    dan catalyst Junior Member

    I just aquired the mold for a 8' rowing dinghy, and i dont have much experience laying up glass. what would you guess the layup scedule might be as in number of gallons and yards of mat and cloth? also is mat required on the gelcoat layer to not show through? or just the arreas without gelcoat ? would a single layer of 24 oz roving doubled up on the sides and bottom w/ 12'' 24 oz tape and 1.5 oz csm work? or would two layers of 1808 be better or three 1708? also what would the polyester resin requirements be per boat? i was guessing 2-3 gallons, but like i said im not sure at all.thanks for your input![​IMG]
     
  2. michael pierzga
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    michael pierzga Senior Member

    Dont know the layup. you might inquire about coremat for bulking the lam.

    A dingy bottom and keel gets abused. Chafe.

    Two years ago the bottom of my tender..keel and transon corners...were wearing so badly from pulling it over delrin skids to store, that I had to flip her over and repair.

    The local glass guy gave me a few meters of 6 oz tight weave Sglass cloth. The sglass was set in epoxy and the weave fill coat was mixed with graphite powder

    The sglass graphite powder combo is Incredibly tough stuff !!!

    This tender gets pulled over delrin skids, in anger, 3 or 4 hundred times per year. I see no damage, no wear. 2 years service.

    If you need to ruggedize your keel give it a try.
     
  3. tunnels

    tunnels Previous Member

    they may be little but have to be built really strong !!

    The smaller the boat the more abuse they get so need to be build like a brick loo almost .
    Core matt is ok but keep it in the top sides of the hull only not in the bottom . Anything less than 4 mm thick is a waste of time !!
    Yes core matt will add stiffness but is not good if there's any twisting and flexing anywhere as it will shear and separate over time believe me !!!!
    The usual 3 or 4 layers of 450gram csm and a 820 gram woven roving in the bottom coming a little way up the sides and completely covering the transom and round onto the topsides 100 mm and as mentioned a solid glass filled Keel and wearing trips on the sides of the bottom , don't use wood at all in the bottom , only in the transom so you can clamp a small outboard on the back !!,9 mm ply bedded completely on wet glass and needs to be two or three times as thick in the middle where the outboard could get clamped on and all glassed over and fit a decent thickness aluminium pad where the bracket clamps are !! . its saves them digging into the glass and wrecking the surface !!.
    The gunnel is really important on small dinghy's and need to be a good thickness and size so Rowlocks can be fitted !! the wood needs to encase the top edge of the glass hull 1/3 outside and 2/3 inside and glued and screwed together right through the wood and the glass . These wee boats get banged ,dropped ,left laying against things for long periods of time !! get sandwiched between other boats and wharfs and squashed !! any ordinary boat would never survive what these wee boats get done to them ,so never use crappy materials any where . :eek::confused:
     
  4. dan catalyst
    Joined: Aug 2012
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    dan catalyst Junior Member

    i just found a great deal on epoxy, so can i use two layers of 1808 biaxial and run overlaps down the keel, so the keel and transom would be four laminates and the rest of the boat only two? thanks for your help!!!
     
  5. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    As I said in the other thread you can always add more if an area seems too flimsy. You can't practically take any glass off. You could try your suggested layup and then take the dingy out and abuse it and see what's needed or not.

    Just don't finish the inside until you're sure you're not going to do any more laminating. You might have to add some more FG tape around the gunnels (or wood gunnels) and you can also use it here and there where it will act as a rib.

    You'll have to add plywood or something to the transom if you plan to clamp a motor on there and you'll have to provide some reinforced oarlock holes or something. Plus reinforcement for cleats, u-bolts, etc.

    All your inside stuff will add a lot of strength-seats with incorporated storage, thwarts, mast holder contraption. Some glassed in foam around the gunnels will stiffen them up considerably and provide flotation which you will definitely need as you will in all likelihood tip that round little thing over a lot, especially with a sail on it.

    When the inside is ready to be finished you might try latex porch and floor enamel- it's cheap, comes in all kinds of colors and weighs less than gelcoat or similar stuff.
     
  6. FibrSupplyDepot
    Joined: Sep 2013
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    FibrSupplyDepot Fiberglass Supply Depot

    To me this seems like the plug and not the mold, could be top cap with shinny inside finished part when pulled off, then where is the hull mold which should be shinny on the inside and not the outside like the picture above. If you build a part from that mold or plug which ever it is. You will have a rough exterior and smooth interior. You need to build a mold off of the pictured plug to get a part that is smooth and shinny on the outside when you pull it out of the mold.
     
    1 person likes this.
  7. Yobarnacle
    Joined: Nov 2011
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    Yobarnacle Senior Member holding true course

    Fiberglass Supply Depot has a good point.
    Are you planning to produce more than one of these?
    If only one is wanted, you got it. The plug. Just reinforce and finish it.
     
  8. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member


  9. Yobarnacle
    Joined: Nov 2011
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    Location: Mexico, Florida

    Yobarnacle Senior Member holding true course

    The thread you show is more informative samsam.
    :)
     
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