Last night I was seized by an idea. This is that idea. Thoughts?

Discussion in 'Boat Design' started by David L. Dodd II, Jun 21, 2020.

  1. David L. Dodd II
    Joined: Jun 2020
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    Location: New York

    David L. Dodd II Junior Member

    I couldn't sleep once this idea lodged itself in my head, and so I sketched it out in Delft Ship. The idea is for a sailing micro cruiser that can plane, without drowning the crew. I live on Lake Ontario and am interested in building a boat for use on the Great Lakes. High enough wind speeds to permitted planing generally come with short stiff chop. The weather can get really rough. I was working on a design for a small Tancook Island Whaler ideal for these conditions when this idea came to me. I usually am attracted to very traditional hulls so this idea is completely new to me. I would love any feedback on the idea. These are the early design stages, so it is easist to fix problems here rather than try to fix them when the design is more advanced.

    The hull is deltoid in shape, with a minimum of rocker. The buttock angle is between two and three percent to facilitate planing. It is fully developable and designed for construction using marine ply and stitch and glue methods. I haven't worked out the rig entirely yet, but envision a high aspect ratio fin keel protruding three to four feet beneath the hull. The hull is broad with considerable initial stability so the need for ballast should be small, allowing the design to have an ultra low displacement. The boat is intended to sail partly heeled over in order to decrease surface area and cut down on skin friction. The beam is wider aft to facilitate planing in a heeled position. The rig will be a sloop with a windsurfer type wishbone mainsail on a wing shaped main mast. The jib will be thirty percent overlapping and mounted on a roller reefing stay. I will also have to rig an asymmetric spinnaker to maximize downwind sailing. I haven't worked out the details yet for that. I intend to place a spade type rudder under the cockpit. I haven't worked out the steering gear yet, but suspect that an offset tiller with a pulley system may be needed to keep the small cockpit uncluttered. Batteries will be placed along the midship chine on either side to keep them out of the way.

    Given the small size, about 25 feet, there is no way to get full headroom, so the internal arrangement wil be a V berth forward, small cartridge head under the highest point in the cabin and a small electric burner for cooking. Bench chairs behind the v berth will give a sitting space. The cockpit is small and self draining to avoid being swamped. The spine of the top of the cabin will be a rubber non skid surface to facilitate walking froward, though movement forward will be minimized by roller reefing the jib. The slope along side the spine of the cabin will have solar panels mounted on it. The slope between the solar panels and sheer line will be peirced by plexiglass windows with UV protective coatings.

    I am attaching the lines plan and two images of the hull below. I am also including the delft ship file if anyone would like to look at the model so far. Any ideas and feedback would be much appreciated. This is a one night idea, so far, and isn't well developed. I have no experience whatsoever with planig hulls, besides reading a description of Uffa Fox's planing hulls online many years ago. If I have made any glaring errors, please point them out.

    Attached Files:

    Last edited: Jun 21, 2020
  2. messabout
    Joined: Jan 2006
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    messabout Senior Member

    To promote planing you will do better to arrange the afterplane so that there is wet surface all the way to the transom. Your view 8 makes the waterline look pretty good for a displacement boat. The boat as pictured could be made to plane given enough thrust. Enough thrust will be hard to create with a sail rig while the boat is right side up.

    Keep working on the design features, you just might create a versatile boat.
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The bottom shape looks pretty antiquated. It looks like a typical tabloid design from 80 years ago. The beam is not farthest aft like on a hull designed to operate in planing mode, but barely aft of midships. Also, the rig is not very modern or powerful. You need to get back to the drawing board.
  4. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Protection from the elements is an important feature, you may want to consider retractable PVC awnings built into the cockpit gunwhales. The semi circular frames are added bracing and the aft one may also double as the mainsheet track and something to hang on to.
    Oh and you will notice that hulls with very wide sterns often use two rudders.. a pendulum action single would be a [tricky] design solution.
    good luck with your project David.
    Last edited: Jun 23, 2020
  5. David L. Dodd II
    Joined: Jun 2020
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    Location: New York

    David L. Dodd II Junior Member

    Dear Messabout,

    Thanks for the advice. I was thinking that as the boat healed, the after waterlines would shift to leeward and the flat section on the leeward side would become immersed producing a plane rising at two degrees from the deepest part of the hull just foreward of center. Is it neccasary to have the transom immersed when on even keel in a vessel intended to sail heeled? If I extend the wetted surface all the way back to the transom, would it be best to do this by submerging the v, causing the boat to drag transom when not planing, or would it be better to pull the chine down even with the bottom of the V and producing a flat after body? It seems to me that a perfectly flat afterbody would be less efficient when heeled under sail, but perhaps I am wrong. Thank you in advance for any further assistance.
  6. David L. Dodd II
    Joined: Jun 2020
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    Location: New York

    David L. Dodd II Junior Member

    Dear Trip The Light Fandango,

    Thank you very much for the idea. I will start working on something like that.
  7. David L. Dodd II
    Joined: Jun 2020
    Posts: 9
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    Location: New York

    David L. Dodd II Junior Member

    Dear Gonzo,

    Thank you very much for your comment.

    I am a bit confused by it, since I cannot figure out how a wingsail is not modern. Perhaps my description was not clear enough. See the attached photo. I am hoping to add a jib to this and a spinnaker. I have been working on the engineering all day. I think I will use an aluminum mast, with a bearing mounted on the top, a bearing mounted two thirds of the way up, and bearing mounted one third of the way up. The wing sail will be mounted to the mast and allowed to swing through 180 degrees on the three bearings. Two narrow horizontal slots will be cut in the front of the wing so that bars can be extended forward to support the jib attachment without interfering with the ability of the sail to rotate. Another bar will extend forward to allow attachment of the spinnaker. The wishbone will be used to control the sail shape so that in forms an airfoil section.

    Attached Files:

  8. ziper1221
    Joined: May 2018
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    Location: florida

    ziper1221 Junior Member

    whose moth is that?
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