16 ft jon boat made from home milled oak boards

Discussion in 'Boat Design' started by l_henderson, Sep 24, 2011.

  1. gonzo
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    gonzo Senior Member

    50HP for a small jon boat is grossly overpowered and will make it a hazard.
     
  2. BATAAN
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    BATAAN Senior Member

    20 hp is plenty to plane it. Had a buddy put a 50 hp on his old heavy wood work skiff that had a 20 hp previously. He fired it up, said 'watch this', gave it full throttle and all that HP ripped the transom out of the boat, did a flip and sank in deep water.
     
  3. l_henderson
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    l_henderson Junior Member

    Thanks, I have started milling boards and with all the input, I feel confident that I can build a good boat. I will have more questions and pictures once I get into the construction phase. This is a great forum. Thanks to all. Larry H.
     
  4. BATAAN
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    BATAAN Senior Member

    Enjoy your boat Larry. That's what it's all about. Oh, and be safe.
     
  5. l_henderson
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    l_henderson Junior Member

    Getting closer to the actual build now. Anyone know how wide batten should be for the bottom and what the attachment screws bolts or nails should be. 2x2 frames @ 15 inch spacing with 5/8 yellow pine planks. Can knees for transom be made of wood?
     
  6. Petros
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    Petros Senior Member

    Knees are usually made from wood, traditionally #8 screws are used for light boat planking, you could also use next size up.

    You might look at the details for the free plans on this site, go down to utility boats, they have a jon boat and boat called "Buddy" that might show how large the frames should be.

    You might also just ckeck out the size of the frame on other boats that have the size engine you have in mind.

    http://www.svensons.com/boat/
     
  7. l_henderson
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    l_henderson Junior Member

    Petros, thank you. It will take me a while to digest. I would like Buddy in a 16 ft. Thanks again.
     
  8. l_henderson
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    l_henderson Junior Member

    The planks that I have are 1 X 14 pine. Some knots. Is that an issue?
     
  9. messabout
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    messabout Senior Member

    Yes, knots may be an issue. Depends on how tight they are and where they occur.

    You can avoid a lot of grief by using good quality plywood for the bottom. You could probably sell those nice 14 inch LLYP planks for more than the cost of the ply, especially if the planks are quarter sawn.

    Bataan; The jon boat in post 14 has a really, really, long bow sprit. That's a puzzling but thoroughly artistic picture.
     
  10. l_henderson
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    l_henderson Junior Member

    Thanks, I am in for the long haul with plank and frame. I have enough knot free for bottom and batten. Also have a nice white oak 2 X 15 to use for transom, but still need good transom design. I know the 15 degree angle but the best way to secure sides and install support that will hold my 50 hp is still in question.
     

  11. alan white
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    alan white Senior Member

    The transom should be made from something besides oak, especially if one wide piece. The problem is that oak that wide exposed to the weather is bound to pull fasteners due to its strength when "moving".
    This will happen whenever the wood isn't completely protected inside and out from sun and moisture.
    Ideally, use plywood (two layers of 3/4", e.g.). Alternately, yellow pine glued up from quarter-sawn narrower pieces will work well.
    White oak has qualities that make it ideal for framing stock (strength and fastener-holding in addition to resistance to rot). However, white oak, and most hardwoods are subject to warping if the wrong conditions occur, conditions that are practically unavoidable with normal usage. Wet-dry cycling must be carefully avoided. Such cycling has less effect on small pieces. Some woods are more stable when reacting to conditions. Mahogany is one. Cedar, much softer, is famous for resistance to warping. Any wood used should be quarter-sawn (this reduces expansion/contraction to about half of what wood cut at 90 degrees to quarter-sawn would move).
    This is why plywood is so great a material for a wide panel of any kind. Save the white oak for things like frames, rub strakes, cleats, etc..
    An exception: My own 15 ft sailboat has white oak coaming fully 8"wide in places. No warping can occur there because the oak is bent to follow the boat's side. Also, sometimes a rudder is made from oak but care must be taken to select really quarter-sawn grain and to protect with paint and to avoid storing the rudder where conditions on each side of the piece are overly different, such as (worst case) laying the rudder down on a wet surface while the upper surface is baking in the sun. If you want to see the extent of this effect, experiment with some samples of various woods, wetting one side only for an extended period.
     
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