Raising the Sheer

Discussion in 'Boat Design' started by Dane Allen, Jul 24, 2008.

  1. Dane Allen
    Joined: Jul 2008
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    Dane Allen Junior Member

    Is there any reason that raising the level of the sheer without increasing the beam would be a bad idea? I'm looking at plans for a Dory but it is a little shallow inside for my comfort so before I take the plunge (yes, pun intended) I want to know what modifications I can safely make.
     
  2. Grant Nelson
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    Grant Nelson Senior Member

    Might affect the overall beauty of the boat - if it was so to start.
    Technically its not a problem on a smaller boat. One risk on a larger boat is you raise also the deck, and any weights that might come on it (like people), and then your boat is more likely to capsize once it starts heeling.
    The other technical risk is you have larger surfaces but still the same beams, etc supporting it so technically you boat will be weaker. Again, assuming your boat is smallish, this should not be a problem.
    Also, you oars, if you have them, will be mounted higher and with that comes issues of length, right height for the rower, etc. Ditto any other long things that move around on the boat.
     
  3. Bob E
    Joined: Jul 2008
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    Bob E some day

    I agree with Grant.

    1) If you raise the sheer, you will increase the beam as this type of boat has a flared hull.

    2) If you reduce the angle of the flare, in order to keep the beam the same, then boat would be somewhat more unstable.

    3) If you kept the amount of flare the same, and the beam the same, you will then be making the bottom of the boat narrower.

    Were I to do this, I would go with 1. The boat would be slightly wider (and longer).

    Bob
     
  4. eponodyne
    Joined: Aug 2007
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    eponodyne Senior Member

    Read and pay attention to the answers you got over at Woodenboat. you werren't being lied to. Your answers here won't be any different.
     
  5. alan white
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    alan white Senior Member

    I thought at first you were adding a sheer strake which, being vertical, didn't increase the beam. Then I thought maybe you were decreasing the angle of the sides so that the beam didn't increase.
    The first, adding a sheer strake and perhaps tapering it to the ends of the boat, seems like a harmless modification. In fact, while a lot of dory buffs might not like the change, it must be recognized that the dory design was developed for fishing, i.e., getting nets over the side, and like many period working boats, could stand a bit of increase in sheer height.
    As with all things, restraint will get the best result. I'd recommend no more than three inches, and tapering to zero at the ends. The boat will be more seaworthy and still retain those dory lines.
    If you simply made the sides higher at the same angle, the beam would be several inches wider, ruining the looks. Changing the angle of the sides would make the boat unstable.
    It should be possible to support added sheer strakes with the same frames by extending them to catch at least two inches of the strakes. Cosmetically, a rub rail at both top and bottom of the strake will look better.
    Your seating position in the middle should be raised to accomodate the higher sides, or the oars lengthened, or both. Best to favor lengthening the oars rather than raise the center of gravity too much.

    Alan
     
  6. diwebb
    Joined: Jun 2008
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    diwebb Senior Member

    Hi,
    I agree with Alan White that the best solution is to leave the hull as designed and add a wash strake inside the existing inwale. This will give the added feeboard you are looking for and will not compromise the design of the hull. You may need to raise the rowing thwart by an equivalent amount and increase the oar length to make rowing easier but these are easily accomplished. Alternatively you could cut holes in the wash starke for the oars and use plugs when not in use ( at least you could not lose these oarlocks overboard!). If the hull is painted and the added wash strake varnished then the appearance of the finished boat will be very attractive. I used the same approach on my design of a 14 foot rowing and sailing boat when I found she needed additional freeboard and it worked extremly well.
     

  7. Dane Allen
    Joined: Jul 2008
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    Dane Allen Junior Member

    Great, thanks for the input. My ultimate goal is to get more vertical space (sitting space?) inside the cabin. I would prefer my wife not have to crawl around on hands and knees to move about the cabin as she goes about her activites.
     
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