Narrow, Multi-Purpose Skiff

Discussion in 'Boat Design' started by SaltOntheBrain, Jun 12, 2015.

  1. SaltOntheBrain
    Joined: Feb 2007
    Posts: 123
    Likes: 7, Points: 18, Legacy Rep: 87
    Location: crosbyton, TX

    SaltOntheBrain Senior Member

    I've been looking at a lot of low horsepower planing boats including Uffa Fox's "Ankle Deep" and I noticed that the transom is just barely submerged, even at rest. Same with Bolger's "Sneakeasy".
    And John Bartlett's "Loon" based on "Sneakeasy", which claims about 20 mph on a 9.9hp outboard.
    What I'd like is a long skinny skiff, flat bottomed for shallow draft and easy ply or aluminum comstruction, that will plane easily with 9.9 to 15hp and a 600lb load. (Really want the 9.9 to work)
    Here's the kicker: I also want to be able to strip the motor off of it and drop in a plate between the transom extensions and drop in two Hobie Mirage Drives and have it perform acceptably like Mack Horton's "Matchstick".
    To do this, the transom will have to be at or slightly above the waterline with about a 500lb load.
    In order to plane well on such low power, I can't have any rocker in the aft end, so I'll have to rely on burying the sharp bow a little to keep the stern where I need it.
    I'm looking at a length of 22' or so and a beam of only 3' or 4'.
    I think it's doable.
    Am I missing anything?

    LF
     
  2. messabout
    Joined: Jan 2006
    Posts: 2,966
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    Location: Lakeland Fl USA

    messabout Senior Member

    A 22 foot boat with 4 foot beam and 500 pounds displacement will draw so little water that you need not be much concerned with transom drag. When level it would draw only a little more than two inches.

    If you want the 9.9 to plane the boat just do it pretty much like Sneakeasy, and keep it as light as you can within structural limitations. It will be an achievement if you can keep the boat under 250 pounds, that'll be without much decking, using Okumee ply, and being stingey with everything that weighs anything.

    The boat is likely to have more than 60 square feet of wetted area. That implies that human power will move the boat, but slowly, without regard to the minor transom drag.

    I think that you'd do better with a long, stripper, square backed, canoe, like Cinnamon, an 18 footer with 4 foot beam. You could stretch it a little if you wanted to. (plans from Canoe and Kayak magazine) They claim that it will go 9 to 10 mph with a 2 HP outboard. I am skeptical about that, even though my 16 foot, narrow, sharpie will plane at 13 mph with a 2.3 HP Mercury. However, the sharpie is carrying a light load of only 320 pounds all up.
     
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