Barge shaped pontoons for houseboat

Discussion in 'Boat Design' started by ALM, May 5, 2019.

  1. ALM
    Joined: Aug 2016
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    Location: Richmond Va

    ALM Junior Member

    I'm in the preliminary stages of planning to build a lightweight simple pontoon houseboat around 26'x12' with a 16x12'x7' structure on it.

    I plan to power it with something around a 20hp motor so I have no intention of this being a fast moving boat. To keep the design simple and easy to build I was hoping to build 2 barge or scow shaped hulls probably around 30" wide and 30" tall which would give me more than enough floatation for the weight I've calculated.

    How ineffective would this be over something like the glen L super huck? The boat will mainly be used at anchor for camping swimming and fishing on a medium sized lake.. can't imagine it ever going more than a couple miles each way on any outings.
     
  2. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    I presume you are planning to build this with plywood. The thing you need to worry about is the skin on the bottom of the floats sagging upward. you will probably need some kind of frame structure to keep this from happening. Such may require only frames every few feet, which can be made of plywood, along with a single keelson down the middle. There are a few other tricks you can use. One, would be to put some rocker in the bottom (which would make the hull more efficient at low speeds). Two, would be having the outer grain of the plywood crosswise. This would require a number of butt joints, which will further stiffen the structure. It is probably best to keep them as close to midway between the frames as possible.
     
  3. ALM
    Joined: Aug 2016
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    ALM Junior Member

    My plan was to start with building the deck with 2x4's I make with 1x4's and two layers of 3/8 ply epoxied together alternating with regular 2x4's, then do plywood bulkheads connected to the deck with 1x2" framing to make the shape of the hulls with a 2x2" running down the middle for extra strength, use 3/8" ply for the sides and 1/2" ply for the bottom. Cut large holes in most of bulkheads to bring down weight with every 4th one sealed in case there is ever a leak. Glass the exterior of the hulls and coat the inside with epoxy. I'm thinking if the interior framing is strong enough glassing the inside won't be that important.

    What do you mean when you say you would add some rocker? Like a slight rounded curve so the bottom isn't totally flat?
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Immersion at the stern creates quite a bit of drag, which might become a nuisance if also battling headwinds.
     
  5. ALM
    Joined: Aug 2016
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    ALM Junior Member

    I'm thinking something kind of along the lines of this.
     

    Attached Files:

  6. Mr Efficiency
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    Mr Efficiency Senior Member

    What is it ?
     
  7. ALM
    Joined: Aug 2016
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    Location: Richmond Va

    ALM Junior Member

  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The picture came up OK, just wondered if you knew what the make of it was. If you know, might be the one for you.
     

  9. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    "Rocker" is is fore and aft curvature of the bottom just like the rockers on a rocking chair. The idea is to direct the water flow under the vessel then back up to the surface. Here is an example:

    cc12a.png

    The advantages are:

    1.) Far less turbulent flow. The hull should be able to reach displacement speed (about 7.5 mph in your case) with less hp.
    2.) Far easier turning. Since the ends are shallower than the middle, they offer far less turning resistance.
    3.) Lower placement of ballast if applicable (due to deeper hull draft in the middle.)

    The disadvantages are:

    1.) Far less buoyancy at the ends. In my example, the ends are clean out of the water
    2.) Very limited speed potential. A rockered bottom will never plane. Instead it will pull the vessel down deeper as its speed increases.
    3.) Greater hull draft per displacement, up to 50% or more.

    Another advantage I didn't mention above, because it wasn't performance related, is that a rockered bottom adds stiffness to the bottom sheeting, as it puts a fore and aft curve in it. Sheet material, such as plywood or metal, does not like to bend in more than one plane.
     
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