Newbie with jon boat questions

Discussion in 'Boat Design' started by Jaxom, Mar 8, 2010.

  1. Jaxom
    Joined: Mar 2010
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Berwyn

    Jaxom New Member

    I'm tired of shore fishing! I'd like to build a jon boat for going to local small lakes or shallow river fishing. Before I started this post, I did do a search on jon boats and read everything I could before I ask more questions.

    I've seen many plans online for plywood jons. But many of them involve tools I don't have or get into complex cuts that I'm not certain I can do correctly.

    Simply put, I looking to build box with a bow... :) Now one of my questions was going to be what angle the bow needs to be. But then I read how easily plywood bends. So instead I would need to determine where I begin the curve for the bow of my propsed boat.

    Proposed specs are...

    24" sides
    16' length
    48" width at transom, beam and bow
    butt joints where ply meets with cleat/rib for support
    3/8" ply for hull and sides
    3/4" doubled up for transom
    need suggestions on what to use for gunwal and ribs to stiffen craft
    bow will also have decking creating storage area and additional stiffening

    I do realize that if I were to tapper the hull (48" at transom then narrow to 40" at bow) it would make the craft easier to manuver. But I want to keep my cuts simple as possible. Where I intend to use the craft I'm restricted to trolling motors only. For river fishing a 5hp would befine as I'll just be using it to run from hole to hole. So I realy don't need something really responsive.

    Suggestions? Comments?

    Thanks,
    Jax
     
  2. lewisboats
    Joined: Oct 2002
    Posts: 2,329
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    Location: Iowa

    lewisboats Obsessed Member

    Start your curve 1/3rd-2/5ths back from the bow, take it up about 9-11 inches in a gradual arc. I think 24" is gonna be a bit tall...I would suggest 20". That way you can use a long legged motor without having to cut the transom down. You can use 3/8" for the bottom but expect some flexing. This isn't detrimental...just a little disconcerting at first. Make sure you angle the transom back by 15 degrees. This is the angle that is needed for most outboards. For a 5 hp, a single layer of 3/4" with a doubler at the motor mount and a triangular knee from transom to floor in the middle is sufficient. This will save you some weight aft. When you attach the sides to the transom make sure that you tape the outside corners with 'glass and epoxy and either fillet the inside or glue and screw a framework of solid wood to securely attach the side panels to the transom. Screwing into plywood edge grain will not hold and may provide an ingress for water to get into the plies. You can use standard 1x2s for the stringers, gunwale and outwale or rub rail. For best results...cut the ends at an angle and glue them together to get the right length...or rip them from a 16' 1x . You could probably build the whole thing with nothing more than a Jig saw a drill/driver and a tape measure. A 4' level/straight edge would be a nice addition though. Don't expect it to last more than 5 or 6 years without some rebuilding and probably not more than 10 all up. It will need to have the paint touched up regularly and any nicks will have to be repainted immediately after the hull dries out and before you use it again. It will have to be dry stored...either in a garage or under a decent cover that is spaced off of it by a couple of inches to allow air to circulate. Don't let water, wet leaves or other crud collect in it or it will rot quickly.
     
  3. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    24" high is way too tall! I'd go 14"-16" myself, but if you expect rough water, go more. The penalty is weight and windage.
    You'll also have more stability if the sides are lower, given the beam remaining the same, as the bottom will be wider (if the sides are flared, which they should be, to gain volume when pressed down into the water).
    A flat bottom requires a good, stiff framing structure to prevent oil-canning the bottom. There are several ways to accomplish this. Simplest, but heaviest, is a thick bottom. However, a lot of weight can be saved by having a thinner bottom, and more transverse (side to side) frames. Transverse frames allow a sole, or floor to be added, keeping the feet and cargo dry. The sole can be removable. A good dimension for those frames, given your design "brief" would be 2" x 3"s spaced every 24" with a 3/8" to 1/2" plywood bottom. The limber holes (to prevent water being trapped between the frames) should be out close to the sides, and not centered, which would weaken the frames.
     
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