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59348Water Ballasted Chebacco

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  • mcdennyw
    Jan 8, 2009
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      In casting about for a sail boat that two (geezerish) people could
      weekend on and I could tow comfortable behind my RAV4 (like to stay
      below 2000# incl trailer, lighter is better) I first spent a lot of
      Freeship time massaging Garden's "Eel" to make it bigger but finally
      decided I ought to find a larger, simpler (no boomkin or bowsprit)
      boat. Most designs are ballasted, making them too heavy for me to
      trailer. Irens' Romilly is a beauty but has an 1150# lead shoe

      Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
      and 25' glued lapstrake versions. No ballast so the weight on the
      trailer for the 19'er is about 1100#, about 1350# for the 25. (all
      according to Freeship). There is a nice Chebacco website with lots of
      good pics to keep me surfing the net instead of shoveling snow.

      Since I can't leave well enough alone, I'd like to improve two things-
      1) Get rid of the flat bottom. It must be a carry over from the
      sheet ply version. Building lapstrake, it wouldn't be much extra work
      to carry the strakes down to the keel. This would improve the looks
      IMHO and avoid the chance for ripples to slap against the bottom at
      anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
      no hiking straps).

      Hey - how about filling the extra volume created by the round instead
      of flat bottom with water? Now the boat will float on its designed
      waterline, no extra weight on trailer and considerably stiffer. Turns
      out there is room for 500# of water under the sole. Wetted surface
      only goes up 2%

      Using water ballast adds weight and righting moment without making
      the boat more "sinkable" or more difficult to trailer. It does add 3
      inches to board up draft but I can live with that. Righting moment at
      20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
      1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
      degrees I create a righting moment of 390 ft-lbs sitting on the
      windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
      having 4 extra people sitting to windward when it's getting hairy.

      Negatives: the exra 500# will reduce the speed by about 10% unless
      sail area is increased and there is some added construction
      complexity.


      What do you think? This seems like such an obviously good idea I must
      be missing something. I'd be especially interested in hearing from
      actual Chebacco owners

      This notion is also posted on the WoodenBoat Forum at
      http://www.woodenboat.com/forum/showthread.php?
      p=2060781&posted=1#post2060781


      There you can see Freeship renderings of the two hulls and the
      righting moment curves.
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