Glued Lapstrake for larger high power boat

Discussion in 'Boat Design' started by graywolf, Aug 10, 2017.

  1. PAR
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    PAR Yacht Designer/Builder

    I've seen the old MFG lap copies of the Lyman and it was a pale comparison to anyone that knows lapstrake. They likely used a few gallons of fillers to radius all the laps, the gains looked awful and the lapped edges were so rounded, it didn't make much of the usual sounds laps make underway. Hideous if side by side to a real lapstrake, fake looking to most and generally difficult as hell to do in a mold.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    That was the difficulty, sharp edges are not suited to GRP. Plenty of aluminium boats have at least the appearance of clinker, but again, smooth edges and corners, so not quite the same, but both the GRP and "tin" clinker has useful stiffening properties, breaks up a slab-sided appearance, and not without merit. The tumblehome in the old wooden boats would have deterred attempts to replicate them in glass. I can remember an old-timer telling me that lapstrake damped rolling motions, which might have been true to some extent.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Probably the nearest thing to a clinker-build skiff in appearance, but GRP, and it was clinker topsides and bottom, was this Stebercraft, which were reasonably popular in Australia back in the 70's and 80's. Graywolf may have liked it ! No distinct chine, just a fairly hard turn of the bilge, clinker all the way, but a full planing boat.

    1985-STEBERCRAFT-Runabout-55m-White-FIBREGLASS-Boat-with.jpg
     
  4. PAR
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    PAR Yacht Designer/Builder

    Let's say you have a 1/2" wide lap exposed, along the length of a plank. A 24' long plank is the same as a 12" square of something mounted opposing a rolling moment. Now multiply by the number of planks and you can see why laps do offer some resistance to heel and rolling moments. There's also a good debate that the bubbles created as the laps move in the flow, act like little ball bearings, decreasing resistance.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Another one being advertised as a Stebercraft, around 22', never seen one. Deep-footed boat that one. Whatever it is, has the clinker look in spades.

    $_20.jpg
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    It is just a matter of the extent of it, I'd guess. You would really need to compare two near-identical shaped hulls, one with, one without the clinker.
     
  7. PAR
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    PAR Yacht Designer/Builder

    They have designs that can be molded, stripped or carvel, as well as lapped, so the comparisons have been done.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    OK, and to get the best effect, I suppose the edges and corners ought not be radiused, as they would be in a GRP knock-off.
     
  9. graywolf
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    graywolf Junior Member

    Somewhere there is a write up about the Friendship Sloop in carvel and clinker. Apparently, in very light airs the carvel was faster, in all other conditions the clinker built one was faster. If I remember correctly they even swapped sails between them to see if the rig was the difference, it was not.

    About that tumble home and stuff, it just requires a split mold. On the MFG's I imagine the inner mold was removed by lifting the bow and sliding it forward. The transom was apparently added afterward.

    Nasty smelly stuff fiberglass, and getting rid of it at the end of its life is very difficult. Wood boats can be burned, metal boats can have the metal recycled, GRP?
     
  10. gonzo
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    gonzo Senior Member

    GRP can be burned too. There are power plants doing it. The same as wood, the temperature control is important.
     

  11. ned L
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    ned L Junior Member

    About 1970 Bayhead boat works of Bayhead NJ splashed a mold off of one of their 31 ft sea skiff hulls and produced a small number of glass versions. Very attractive boats with their nice tumble home. At least couple of them are still around.
     
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