Glued Lapstrake for larger high power boat

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

  1. graywolf
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    graywolf Junior Member

    I have been wondering if Glued Lap with laminated ribs might be viable for boats in the 20-30 foot range with modern high powered engines.

    The reason I am asking here is that the designs I see are for row boats or small sail boats.
     
  2. gonzo
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    gonzo Senior Member

    Lapstrake powerboats used to be popular, but fell out of style. They usually had reverse planking to the turn of the bilge and then regular planking. The bottom planks acted like steps or lifting strakes.
     
  3. graywolf
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    graywolf Junior Member

    Lapstrake power boats are still popular with people who are into wood boats.

    However, I see that Par answered my question in the ill fated "Planking" thread in another section. For those who do not care to search for it, the answer was basically "yes".
     
  4. ned L
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    ned L Junior Member

    I hope the construction method works, my 33ft lapstrake Jersey sea skiff is 60 this year. I'd hate to find out it won't work. lol
     
  5. graywolf
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    graywolf Junior Member

    HA! Actually, the question was about glued lapstrake for bigger boats, as the ones I have seen were rather small 16'.
     
  6. gonzo
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    gonzo Senior Member

    For small boats, the planking and framing can be lighter than a carvel construction. As the size increases, that difference disappears. The difficulty of lapstrake planking can then only be justified other characteristics. One of the principal ones is aesthetics. The other, is for boats that stay out of the water but need to be deployed quickly, like lifeboats and surfboats.
     
  7. graywolf
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    graywolf Junior Member

    Oh? You mean like trailer boats?

    And, of course, the Vikings did not make 100+ foot long lapstrake boats, or did they? Lapstrake is always lighter than carvel for the same strength. In the traditional construction, it is also bottom up rather than top down and actually simpler to build. However, before modern plastic seam compounds lapstrake tended to seep a bit. In fact, before those compounds lapstrake boats need to get wet for awhile before they stopped leaking quite a bit; take it out of the garage in the spring and launch it and it was likely to sink. Next day it would stay afloat and it a week it would hardly leak at all. Smart guys would take the garden hose and put about a foot of water into the boat before taking it to the lake the next day, that way it did not sink.

    Oh, maybe this old man actually has had experience with those boats...
     
  8. gonzo
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    gonzo Senior Member

    Lapstrake is definitely not always lighter than carvel. Also, you will have to define what you mean by strength before we can compare apples to apples. The vikings didn't know the saw; all their woodwork was done by splitting and carving. It wouldn't really lend itself to carvel construction like in Southern Europe. I don't know how you can build any planked boat from the top up. That means to build a deck and put a hull under. Traditional construction starts by the bottom: laying down the keel.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Traditional build types rely heavily on "interference fits" of the planking, regardless of type. Before modern goos came to be, heavy shellac was common, though more often than not, cotton or simply tight interfaces on the faying surfaces was all that was used, each with mixed blessings. Carvels and lapstrakes typically were placed in the slings to "suck up" and this was just commonplace commissioning duties. All the modern goos did, except for epoxy was to accommodate the fit, until the planks swelled up sufficiently to tighten up the hull. Now each build approuch used slightly different approuch to this interference fit thing, but they all required some level of moisture gain, including the Vikings efforts. Simply put, that planking fasteners did all the work, assuming the seam fits were tight. If there were not, the fasteners would experience shear loads, egging out their holes, with the resulting leaks and fastener sickness to follow. Modern goos have eliminated the need for the majority, if not all of the planking fasteners and much if not all, of the internal framing as well. Which is why you can save weight, with modern living through chemistry.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    Beats me why anyone would want to re-visit old methods of construction that have watertightness dramas, high maintenance requirements etc. Clinker had eye appeal, and stiffened the boat lengthways, allowed a freedom of shapes not available in sheet ply, but GRP could create the same look without all the upkeep, though tumblehome might have to be eliminated. Did any of these old "classics" make the transition to glass ? Very few boats today have the mock clinker, I imagine it is not ideal to be rolling out glass round a host of corners. Or the "look" just went out of fashion.
     
  11. Steve W
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    Steve W Senior Member

    For gods sake the guy is asking about GLUED lapstrake, ie, plywood and epoxy, not traditional lapstrake. Peter Spronk built large plywood lapstrake sailing catamarans up to about 75ft back in the 1970's and 80's, many of which are still sailing today. I can't say for sure they were glued laps but I would assume so. They were exceedingly beautiful boats and quite light for their size.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Lapstrake ply, leave me out of that, with all that end-grain. There has to be better ways in 2017.
     
  13. PAR
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    PAR Yacht Designer/Builder

    Plywood planking, even with the exposed end grain has 3/4's plus of a century, to have easily proven it's durable, with even modest care. You can't make a 'glass boat look right in a lapstrake. I suppose you could quadruple the planking costs with Cossa or other material, but why. I just got rid of a lapstrake built in 1960, with the exception of garboards and broads, still had its origional planking.
     
  14. Steve W
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    Steve W Senior Member

    Agreed, I have worked on a few old Thompsons with problems where the planks meet the transom but generally in good shape elsewhere. With well epoxy sealed edges I see no problem with longevity.
     

  15. graywolf
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    graywolf Junior Member

    Actually, it is reported that MFG, the company that did the original Corvette bodies, built a copy of the Lymans using inside/outside double molds. They supposedly used actual Lyman hulls for plugs. They reportedly were very good boats. I bid on one on eBay a couple of years back but got outbid by $5. They sold off the boat business sometime in the 1960's I think. In the 1950'sand 60's they were probably the most advanced fiberglass manufacturing company around.

    Here is a link to my blog article about it. Unfortunately, I am not going to renew my web host so this link will be dead in a couple of months:

    The Christmas Present I Am Not Getting http://graywolfphoto.com/journal/2014/12/22/the-christmas-present-i-am-not-getting/
     
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