Small boat design

Discussion in 'Boat Design' started by BWD, Sep 11, 2007.

  1. BWD
    Joined: Aug 2006
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    Location: Virginia, US

    BWD Senior Member

    Hi, been a while since I tossed an amateur "plan" up, but I have another.
    On the Chesapeake, I've long admired the bay-built skiffs, deadrise work and buyboats.

    But the flat-bottom skiffs tend to porpoise and pound, and I might occasionally tow a skier or want to cruise sort of fast, while a 40' deadrise is a bit much for me. And I wanted to think up a solution different from the usual popped-out fiberglass skiffs.
    So, I have been looking for shoal draft, chop handling, and ability to cruise comfortably on plane. Looked at many S+G designs, V, dory, Atkins designs, other seabright types, "frogbelly" hulls, boston whalers, sleds, etc.

    Then I started drawing and -surprise- same up with a 20ft skiff (is there a prize for the billionth design?). It keeps a little of the traditional look, and has developable surfaces. I like the near-plumb stem, so kept that in spite of the lightness of the boat, since I'm not looking to go in big water. So I have a wedge hull variation with little v in back, 6'4" beam, 1450#at 8" hull draft, & 2300# at 10," which is more than she'd weigh or carry. Rigged she should float in around 7.5” or less.

    I realize it might not perform better than other S+G designs (at best) but to me the look is better, with a couple extra panels. Maybe needs a touch more flare -tough issue for me ( - I'm from Va but went to school in NC ;) ). Hoping it might run 20-25kts with a 70hp OB, cut small steep chop easily off plane, and if lucky run comfortably at 15 or so. Feel over my head trying to integrate elemants here, but grateful for any constructive feedback. Especially on those waterlines. You’ve got to start somewhere….

    Done in Delftship, here are drawings, comments welcome:
    Edit: added a version with max V without changing lots of other things too much. Moves the CB aft to 6.25' from 7.5'...
     

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  2. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Regardless of what she'll do motoring, I saw nothing in the lines to prevent sailing rather fast with the right rig. Then, you might want an inboard located in the middle. Hmmm.


    Alan
     
  3. Guillermo
    Joined: Mar 2005
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    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    You'll have to keep that forefoot out of the water when planning, or it may induce directional instability, in my opinion. Maybe doable when in flat waters, shifting weights backwards, but when in waves....

    I also think extra panels in the bottom will complicate construction and add extra drag.

    Cheers.
     
  4. BWD
    Joined: Aug 2006
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    Location: Virginia, US

    BWD Senior Member

    Thanks for the replies. You know, Guillermo I think you are probably right. I have a little sentiment that makes me like the shape though. I would round the forefoot a bit, but easier to do in reality than in CAD, so it shows sharp in renderings.
    I have only crude guesses about trim under power at this stage, but with an outboard, it should not be hard to have the bow trim up.
    The waves are an issue. Local conditions can make waves of max steepness (estimate 12 to 14:1 length:height) but rarely more than .75 meter. Feel ambivalent about it. I don't go out for fun, needing to plane fast, in washboard chop over 1 foot. Or this boat in the ocean! Maybe I can accept going 5-10kts when rough.
    To address these problems, I might cut away the forefoot, add that flare, and go on and soften the reverse "keel" chine, plan on stripping instead of sheet construction.
    Then I lose the look, but go a little better on plane in chop.

    Now all I have to do is turn the aft stations to true monohedron and I would have something I could buy on any street corner-the homogenized skiff! :(
    Well I will have a couple of years to think about it until maybe I get a garage...
     

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    Last edited: Sep 13, 2007
  5. kengrome
    Joined: Jul 2006
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    Location: Gulf Coast USA

    kengrome Senior Member

  6. Brands01
    Joined: Nov 2006
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    Location: Sydney

    Brands01 Senior Member

    I think your second design looks much better - no need for that pointed forefoot in the first one, and that wedge did look like the drag would outweight the benefits.

    Does the transom still have a warp in it?
     

  7. BWD
    Joined: Aug 2006
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    Location: Virginia, US

    BWD Senior Member

    The transom is not warped as you can see from the (unfaired) views here. I guess with the cutaway forefoot and other speed/handling mods I'd extend the flat section forward a bit, get 6-8 feet of high speed bottom shape.
    Might as well go fast and save gas if you're going to look modern....
    But I'd like to have a little of the character of the traditional boats, like the "Miss Rappahanock" below. So I was thinking originally if warped it might run flat enough to be good if I stay out of nastier waves. For that I would give up a few gph, but I don't want a boat that is awful in waves, and maybe the 3/4 to 1 ton size is just too light for the shapes I like.

    @KG that slicer is sort of cool in its way. Probably more suited to the narrow waters up in Maryland though. Unfortunately I could never get it in the driveway. Might be nice with a wide beach/private railway though. I think the idea of that boat is in addition to removing the outboard easily, no one would be able to steal it without a custom trailer. And it would stick out like a sore thumb.
     

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