Full displacement, sail capable trailer trawler

Discussion in 'Boat Design' started by kdhorton, Dec 28, 2010.

  1. kdhorton
    Joined: Jun 2010
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    Location: El Paso

    kdhorton HM Small Boat Designer

    Hello all,

    After some months scouring the options of boats, little ships, etc, to build I started sketching up a 23' LOA full displacement tug type yacht.

    I understand I am not a naval architect and should, if I were a solely logical person, leave the design to a professional. My goal is to get the basics of what I want on paper, then when I get those basics done to take it to a naval architect. So I will keep my intro questions simple as possible.

    First, my construction method is marine ply, preferably a single hard chine using stitch and glue (I know Devlin, who's $800k tug yacht was one of the dream boats I will never be able to afford, is a champion of this method) construction. In my sketch I stole the idea of twin bilge keels off of Kasten Marine (http://www.kastenmarine.com/bilge_keels.htm) as I had already designed but had no idea if something similar would work. It also keeps the draft more shallow than a full keel.

    My first major question is this: I have designed it with an engine room below the pilot house for a diesel inboard; however, for a 23' LOA, 8' beam would a outboard in an engine well be suitable if the HP was high and the RPM speed lower than a speed boat? I also allowed for that possibility in the far rear of the fan stern.

    I have attached my prelim sketch without any of the CAD modifications, only a proposed waterline. My notes on it are:

    1) 1 graph square=1'x1'.

    2) The sides seem to be more flat then any design I have seen. Will this present a problem? At any rate I intend to curve them slightly more although I am looking for as much volume as I can get without going over an 8' beam.

    3) I have not yet done the calcs for sail area, and while I am well aware this is not the optimum hull type for a sailing craft several Tug style yachts employ sails somewhat effectively. I am going to insert a mast at the front of the cockpit that doubles as a support column for the cockpit roof and another at the rear of the salon; the intent will be a type of yawl rig. Any input on this is helpful.

    4) The forward deck will house a hatchway to a cargo area instead of berths. This will be used by my brother and I and need only two berths, which I am trying on my interior layout to put in the salon and along the port side of the cockpit with a double as a nav desk in daytime. I figure with a forward cargo hold I can use the craft to deliver almost 100 cubic feet of medical supplies, freshwater, or something of a humanitarian nature to justify my longed for open water cruise. I am also designing an insert for the hold to carry fish, with the appropriate plumbing, to perhaps help pay for one of these excursions on the return trip.

    5) Lastly, I am working on innovating several longevity/cost ratio raising items such as desalination works, that along with the hopeful effectiveness of adding sail auxiliary will be somewhat cost effective in the future.

    Now, tear it apart if you are so inclined...
     

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  2. kdhorton
    Joined: Jun 2010
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    Location: El Paso

    kdhorton HM Small Boat Designer

    I should also note that the illustration I uploaded was not the initial sketch as I thought it was, but the one with the blocks showing the two possible engine locations in gray.
     
  3. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    Nice boat in your drawing. Looks a bit like a Lord Nelson.
    I'd use sawn frames. No ob. Props too likely to come out of the water in rough going. Sails will add expense, weight and lots of head wind windege not to mention vertical clearance problems. Most power boat are better off w/o sails.
    Ten to 20hp will be plenty of power. Here is a 23' full disp cruiser you may like.
     

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  4. kdhorton
    Joined: Jun 2010
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    Location: El Paso

    kdhorton HM Small Boat Designer

    Thanks easy rider for the input and advice. The outboard is out.

    That is a pretty nice looking boat, is it for sale? Not exactly what I was looking for but close.
     
  5. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    We've seen it in Bar Harbor in Ketchikan Alaska (45 mi from us) when we go there (several times a year). It's a Puget Pocket Cruiser built on Vashon Island in the 60s (I think). Don't know what they were powered w but most manufacturers over power ...sells boats to automotive oriented people. Four to 5hp per ton is my rule of thumb. If you really like it search Yachtworld ect.
    There should be one (or so) for sale in Puget Sound or BC mainland. I've seen more of them in BC than Puget Sound. Saw this one in Nanaimo BC.
     

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  6. kdhorton
    Joined: Jun 2010
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    Location: El Paso

    kdhorton HM Small Boat Designer

    I have finally gotten to where I can somewhat competently use Delft and Free!Ship. By that I mean I have some of the basic mechanics down. I have been reading John Teale's "How to Design a Boat" for light reading and E. C. Tupper's 4th Ed. "Introduction to Naval Architecture" for my heavier evening reads. The flaws in this design and several others I doodled are becoming very apparent, but it's fun as an exercise in using the drafting program to draw some of these "storybook" designs.

    I still have to figure out how to get the decks and cabin houses put in using the Delft or Free!ship software... however, if transposed over the hand drafted version you'll notice the hull is identical.

    Everything else aside- what I'm most excited about is the fantail stern. I really enjoy those and being able to draft them is pretty exciting. It took some patience to get down.
     

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  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The whole design is not appropriate for plywood. You need a chine and curves that can be accomplished with plywood.
     
  8. kdhorton
    Joined: Jun 2010
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    Location: El Paso

    kdhorton HM Small Boat Designer

    Ah yes, it's been a while since I posted the first post. In delftship, this model was done as 1/4" steel plates and a hard chine version for plywood. The drafting of the fantail was the main purpose of the exercise though, as I'm not too sure the base design is worth salvaging.
     
  9. gonzo
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    gonzo Senior Member

    You may need to post the new specifications to get answers that make sense.
     
  10. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    for a 23' LOA, 8' beam would a outboard in an engine well be suitable if the HP was high and the RPM speed lower than a speed boat?

    A boat of this type and speed regime will usually operate at 2 to 3 HP per ton (2240) of actual weight.

    For a good looking boat with all these curves Foam core would be a longer lasting choice.

    In the total cost of the project , I would spend big on a hull, and marinize a small diesel, to save bucks.

    A Kubota or Yanmar from a truck reefer repair shop , $300-$500,rebuilt Twin Disc tranny , $1500 and you have a better longer lasting power system than a factory new "marine engine".

    Spend on what cant be replaced, like the hull construction.Then do some "sweat equity" for the insane priced Marine items.

    FF
     

  11. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    For $1500 there are a lot of use marine engines in the 10Hp range. That is plenty for a displacement boat in that size.
     
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