Outboard Dory Project

Discussion in 'Boat Design' started by Nordski, Jan 26, 2020.

  1. Nordski
    Joined: Feb 2019
    Posts: 27
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    Location: California

    Nordski Junior Member

    I’m working on a new project and looking for insight regarding several details. 1) I’d like to build this boat with a flat clean deck, no center frames, taking the idea from Tom Hill’s “Long Point”. I have shown the max. span of the open deck to be about 47”x 131”. This may be accomplished with a 1” or 1.5” laminated bottom, not sure, I would like some feedback on this. I have shown 2 different options for side framing, looking for feedback on this as well. The sides are 3/8”, bulkheads are 1/2”, I have shown some detail for the keel and bottom runners. 2) The outboard engine will be approx. 220 lbs I’m thinking of installing a 15 gallon bow fuel tank to balance the boat. 3) I believe the hull weight will be approx. 800 and estimating a 25hp outboard to power the boat. Thank you.
     

    Attached Files:

  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Nordski, what will you do with the boat? Where and in what kind of weather will you use the boat.? Is this a gunkholer or an offshore fisherman? How fast do you want to go?....more questions.......etc.

    Before anyone here can give you any relevant comments we will need more information. Boats can be thought of as horses in which cases there are "horses for courses". It is the conventional, and wholly necessary, proposition to create an SOR (statement of requirements) . Post your SOR and you will get some feedback that may be helpful.
     
  3. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I like it.

    But, I don't like bow tanks.
    Do you have to?
     
  4. Nordski
    Joined: Feb 2019
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    Location: California

    Nordski Junior Member

    Messabout, thank you for the reply. The boat will be used in my local fresh water lakes and harbors, my offshore days are behind me, I am now a fair weather boater. This boat is for gunkholing, bird watching, photography, sightseeing, napping etc. The boat will likely be used by 2 people, sometimes 4. I’ll pick my days if I do go offshore for a few photos but that would be seldom and never far from the harbor entrance. I’d would be happy to travel at 15 knots if moving from place to place.
     
  5. Nordski
    Joined: Feb 2019
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    Location: California

    Nordski Junior Member

    I don't think so but not sure......just trying to keep the weight off the stern. I've never built a boat with a bow tank so I'm not familiar with them. I have build boats with too much weight in the stern and it can be a fight to fix the problem.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Bow tanks have the problem that they affect trim too much, when full, or getting low. As for wanting a clear space, and getting rid of frames, what is the issue with having frames, and ply on top, as your clear space ? Raising the height too much ?
     
  7. Nordski
    Joined: Feb 2019
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    Location: California

    Nordski Junior Member

    Yes, I would like to keep the deck low and it simplifies the building a bit. I like what Tom Hill did and the results seem to be good from the builder reviews. It keeps the weight low and adds a few pounds low in the boat to help with stability. It seems to me that the boat would function well and be nice and stiff but I have made mistakes thinking and building something that isn't accurate. Trying not to make the same mistakes again.
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The key to that idea would be how you connect the topsides to your frameless bottom. Maybe you can arrange for the outside plies to be in the athwartship direction, on your bottom panel, to stiffen it on that axis. Deepen the rubbing strips on the bottom to stiffen the long axis.
     
  9. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Here is a link to Tom Hill's plans for 'The Long Point'.
    "The Long Point" Boat Plans https://tomhillboatdesigns.bigcartel.com/product/the-long-point-boat-plans

    They cost the princely sum of $75 - Nordski, if you have not yet purchased a set of plans, please do - even if you just use these for reference in determining scantlings etc for the design of your boat.

    Some comments from the webpage re your queries -
    Re a 1" or 1.5" bottom, Tom says "I designed her to be rugged with 1 1/2" thick bottom. I wanted a bottom that wouldn't oil-can when pounded into a chop. The bottom also had to be strong enough on its own - without floor frames - so she would be easy to clean and refinish. The flat bottom allows her to be beached bold upright for picnics or clamming."

    You are estimating a 25 hp outboard motor that weighs 220 lbs - Tom says :
    "This boat was designed around the Honda 15 hp long shaft. I wanted a quiet, throaty sounding engine that would push her over 20 mph and cruise all day on less than 3 gallons of gas. This boat does not need more horsepower!"

    Google suggests that the 15 hp four stroke Honda weighs 101 lbs.

    Tom also notes that the hull weight is 400 lbs (approx). I am assuming that this includes the centre console, but not the engine.
    Re your estimated hull weight of 800 lbs, what are you including in this - are you including engine, fuel and yourself as well?
    I see that you have drawn a small cuddy cabin up forward, but this is not going to weigh a lot relatively.

    Here is a thread on the Wooden Boat Forum about the Long Point skiff, with a few photos.
    Tom Hill's Long Point Skiff- Anybody used one? http://forum.woodenboat.com/showthread.php?104684-Tom-Hill-s-Long-Point-Skiff-Anybody-used-one

    And a video about a Long Point, showing it underway as well. The boat in this video does not have a centre console - rather, the skipper is steering with an extension tiller on the outboard motor.
     
    Last edited: Jan 26, 2020
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  10. Nordski
    Joined: Feb 2019
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    Location: California

    Nordski Junior Member

    That sounds reasonable to laminate the outer layer as you suggested, I can easily do that along with deepening the rubbing strips. Thank you
     
  11. Nordski
    Joined: Feb 2019
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    Location: California

    Nordski Junior Member

    Thank you for the input. I have Tom Hill's book and several sets of his plans. The boat design I am proposing is 23' so it seems to me that a 25hp outboard would be appropriate for its use. My weight estimates for the outboard are likely conservative. The estimated hull weight is a bare hull with a small cuddy, the finished hull weight may be less but I threw that number out there for discussion.
     
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  12. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Ooops, my apologies - I just saw a little 23' at the bottom of your side profile sketch which I hadn't noticed before.
    That makes more sense re the increased hull weight and the larger engine required.
    Your boat will be more slender - the length is increased by 7', and the maximum beam by about 4".
     
  13. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I like it even more.
     
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  14. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Yes, all else being equal she should have a more efficient hull shape.
    Nordski, re your several sets of Tom Hill's plans, are any of similar size / shape to the Long Point?
    If yes, then they would be useful to follow for guidance.
     

  15. Nordski
    Joined: Feb 2019
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    Location: California

    Nordski Junior Member

    I don't have the "Long Point" plans but it is built much like his other designs (glue lapstrake) over a frame. He does have 3 thwarts that likely add to the stiffness of the hull. The attached files reveal an open clean hull bottom.
    LongpointBow.jpg
    LongpointStern.jpg
     
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