Building a Small Boat

Discussion in 'Boat Design' started by mgriffin, Mar 30, 2009.

  1. mgriffin

    mgriffin Previous Member

    I am thinking of building a small boat, as the title says. I have numorous questions about regulations for motor boats though. Would it be illegal to boat on a canal? I am guessing yes, since I don't see any other boats on the canal. How am I supposed to know where I can go in my boat if there are no "Keep out" signs? The boat I am going to build is going to have a shallow draft of maybe 2-3 inches so I could go alot of places that a normal motorboat cannot go. Even over weirs, but I would have to have a rope tied to her and to a tree or something to keep her from going over to fast. I was also thinking about putting some kind of reattachable trailer on her so I could land her and jack her up and attach the trailer and pull her on the bank around rapids. Yes, I said pull her around rapids. She is going to only be 8 feet in length with 4 feet in beam. The trailer will have only two wheels so I could use it kind of like a wheel barrow, instead of pushing, I will be pulling though. And the engine, I was pondering and I got the idea to just get one off of a lawnmower and attach it to a propeller. It will be outboard so I can keep her shallow draft if I run into shallow waters. I would of course put the outboard up for going over weirs and such stuff. I might have to use a pole and push her in shallow water though.
    thank you alot,
  2. apex1

    apex1 Guest

    In dreamland, as I was tought, everything is allowed with no permission needed.
    But if the canal is connecting dreamland with the "unreal" world, a permit might be a issue.
    To get a valuable answer it would help to know which canal we are talking.

  3. mgriffin

    mgriffin Previous Member

    I don't really live in dreamland you know. The canal I want to float my boat in is the virgin river. (I call rivers canals).
    thank you alot,

    Attached Files:

  4. apex1

    apex1 Guest

    ok Ill do that, naturally!! So you should too!
  5. mgriffin

    mgriffin Previous Member

    Thanks :)
    thanks again and btw, I made a rough sketch of the boat on paint. Yes, I am going to buy a cad soon, you do not have to give me one. It is not worth the trouble.
    That is the actual hull shape of the boat. It will have a pointed bow, but it will be flat, not curved. ease of construction....:D

    Attached Files:

  6. mgriffin

    mgriffin Previous Member

    NVM. What do I need a cad for? I already drew a detailed diagram on some graph paper, so it is to scale. And it is not just a pretty picture, it is the plans for it. I am about to draw the cuts I will need to make in the wood, and the amount of 1/4 inch plywood sheeting I will need.
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Mike, the shapes you've drawn will displace 1,380 pounds when floating with 3" submerged.

    This shape will require a lot of power to propel. It will bash through the water like a snow plow and be terribly inefficient, particularly with a modest output inboard.

    A hull like that will steer like a pig, be very difficult to maneuver on a low power inboard and of course it'll pound badly.

    It's not possible to have an inboard and a few inches of draft. Just can't be done without a tunnel hull or other consideration.

    I'm assuming from your drawing that it's 16' long, 6' in beam and has normal standing headroom inside the pilothouse.

    Bending plywood around simple shapes is easy and the water likes it a whole lot better then angles at low speeds. If the sides are perpendicular to the bottom then it's real easy. Reconsider your shapes.

    Assuming my scale from your drawing is correct, you'd need at least 15 sheets of plywood to build a minimum boat. Even the lightest ply will weight 300 pounds, before glue, fasteners, engine, fuel, etc. Frankly, a shape like that will probably be over 500 pounds (raw hull only), so portaging her isn't as likely as you might think, without a truck.

    As far as getting around on local waterways, you can go where ever you like. Restricted areas will be marked on the charts for that area.
  8. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    You might want to recalculate PAR...he said it was 8x4...I'll ditto everything else you said tho.

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  9. erik818
    Joined: Feb 2007
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    Location: Sweden

    erik818 Senior Member

    Double the length and make the shape more canoelike from the middle and forwards to serve as a wavecutter. Adjust the measurements to suit the plywood you are using. Let the sides be e.g. 2 sheets long. Keep the flat bottom you suggest, but with a slight rocker (4" or so) starting 1/4 from the fore. 1/4" plywood should be fine. Whatever superstructure you build should be extremely light or the boat will tip over. I suggest you skip the superstructure for a starter, you can always add it later.

    The weight should end up at 100 kg or less, perfectly possible to move by hand to pass rapids if you arrange so you can attach a pair of bicycle wheels at the sides.

    The draft will be a few inches with you on board. I suggest a small outboard on the reinforced transom (1 - 2 hp) and paddles when the water isn't deep enough.

    You need to use plywood with water proof glue (preferrably marine grade) and epoxy for scarfing and for taping seams. Keep the boat simple and cheap. It won't last forever, but within a few years you will start on your next boat project anyway.

    Good luck,
  10. mgriffin

    mgriffin Previous Member

    Sorry about the 6 x 16 confusion. I drew that on paint, that is not the drawing for the plans. I don't know how to draw scale drawings on paint. And about the outboard, if I made it an inboard, then it would have a better draft. And your right about the sleekness of the hull. I will redesign. It will not be very easy making curves in a boat and keeping the flat bottom though.
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Okay, I missed the size thing, oops.

    An 8' boat is ungodly small. I just mailed off a set of my plans for a dinghy (RYD-8.4). It's 10' over all and it's ridiculously small too.

    You need to climb into a yacht tender and think about your size requirements again. Sit down in it and try to picture where everything will go.
  12. mgriffin

    mgriffin Previous Member

    Your right... How about 12 feet? 4 feet wide?
  13. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    Lots of posts here on conversion of weed eater engines for shallow running with a mud type prop. They mount on a pole so you can lift them out of the water. Lite too. They act as your rudder also.
  14. ancient kayaker
    Joined: Aug 2006
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    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    I think 10' LOA is cute, not ridiculous!
    1 person likes this.

  15. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I'm sorry Terry, I certainly didn't mean to offend you. By the way, your plans went out at the first of the week (as you may have guessed from the last post). You should get them in a few days. I was at a boat show this weekend and sat in a few "little" boats, from a buddy's shop. I guess I'm getting sticky for elbow room as I age.

    At 12', you're getting into the cute little harbor tug range, well okay the very small end of that range, but doable. Normal standing headroom will be difficult to get without it looking like a Winnebago is parked on a barge, but sitting headroom (all you really need) is possible. An inboard will still be very difficult to justify, but possible at the cost of huge chunks of interior space and draft.

    Mud motors are an option, but they are typically tiller steered, you generally don't have reverse or neutral either, making maneuvering around tight spots are chore to say the least. Personally I think all boats should have neutral and reverse gears. You pretty much have to have them, if you'll not employ tiller steering.

    This leaves the outboard (again) as the logical choice. It can be mounted in a well or box so you don't have to hear, see or smell it and you can have a remote helm with gear selection too.

    Several of these types of little harbor tug plans exist, some low cost or free. I toyed with a little tug design (16') a few years ago, but never developed the plans to completion. I considered the market too small to warrant a "spec" job, so I put in a drawer.

    On the other side of the coin there are also "shanty" boats and "micro cruisers" to select from. Most of these are children only a mother could love, but are usually simple to build on a budget. You don't even want to know my opinion of these little floating boxes, but some folks love them. I consider these little more then dressed up concrete mixing tubs, but what do I know.
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