Flat bottom fishing/bowfishing boat

Discussion in 'Boat Design' started by Birdsofprey, Mar 17, 2021.

  1. Birdsofprey
    Joined: Mar 2021
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    Birdsofprey New Member

    So I am going to build a small boat to fish and bowfish off of. We went out this last weekend in one that I want to copy. It was bigger but the design is the same. My design is 16 feet. 10 of it flat bottom the last 6 sloped up to the bow. 17” sides. 5 foot beam. Then an 8x8 flat deck on the front. I intend to use 10 gauge sheet metal and 2x2 for the framing. I’ve added the weight of the whole thing up to be about 1010 pounds. It appears that it will have a draft slightly below 4”. Then another 3” loaded with people and gear. It will be driven by a small outboard motor and a trolling motor up front to fish with.

    I considered aluminum but the added cost of aluminum didn’t seem worth while. I intend to epoxy paint the hull inside and out.

    I’m curious if anyone has tried something similar or if plans exist that I could use. Also concerning the sides most I’ve looked at online were 17 or 24 inches. I don’t know if it’s needed to be 24? Seems like we would never be more than 8” draft.
    I also considered in the front where the flat angles up to the bow making a small enclosure across the boat and maybe a few inches deep to fill with flotation foam. My thinking is when everyone is on the deck fishing it will help keep the boat level?

    Any thoughts or recommendations? I’m looking at the welding and don’t think it will take me that long to complete.
    Thanks
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Sheet metal, as in, what, steel ?
     
  3. Birdsofprey
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    Birdsofprey New Member

    Yes 10 gauge sheet.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't think anyone will advise that, mainly because of maintenance, but also weight. That is a lot of weight for a 16 foot x 5 foot boat. What size outboard were you thinking ?
     
  5. Birdsofprey
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    Birdsofprey New Member

    Was hoping 15-20 hp. One of the lakes we fish has a 25 hp limit.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    25hp would be insufficient to comfortably plane that boat with people aboard. 25hp is probably marginal even for a lighter 16 foot boat, that is loaded up, even a flat bottom. But steel boats like this are a rarity, and an especial rarity as a planing powerboat, largely because the need for reasonably heavy gauge material that allows some latitude for rust before perforation, makes the boats too heavy, the surface area of a hull increases by the square of the length, the displacement of the boat by the cube of the length, so small boats end up with more surface area proportionally. And if there is a minimum practicable steel gauge, it makes small steel boats too heavy. Ply seems the most likely choice.
     
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  7. Mr Efficiency
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    Mr Efficiency Senior Member

    What was the one you went out in, that you want to copy, made out of ?
     
  8. Birdsofprey
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    Birdsofprey New Member

    It was about 26 foot and al aluminum. Completely seam welded.
     
  9. RAraujo
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    RAraujo Senior Member - Naval Architect

    I could not understand:

    QUOTE
    upload_2021-3-18_9-33-55.png
    UNQUOTE

    Is this foam inside the boat? If so how will it contribute to the flotation and trim?
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    26 feet ? That's a lot of boat for lake fishing, how many people aboard do you want to be able to handle ?
     
  11. bajansailor
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    bajansailor Marine Surveyor

    This puzzles (and worries) me a bit.
    5' of beam is not a lot for a 16' boat. A few extra inches (or more) would probably make a big difference re stability.
    And if you have an 8' x 8' flat deck on the front, then the deck is overhanging each side by 18"?

    10 gauge steel is about 3 mm / 1/8" thick - about the minimum needed so that you don't have to worry (too much) about corrosion, but 1,000 lbs hull weight for a 16' boat is a lot!
    And you will have to spend a fair bit on paint.
    I am sure it would be much easier, simpler, and even cheaper in the long run, to just buy a suitable plan for a well proven plywood boat of similar size, and build that instead.
    Have a look at the Spira Boats website - and do some googling, there are many more excellent designs out there.
    Spira Boats - Easy to Build Boat Plans https://spirainternational.com/
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    I missed the 8x8 platform, a bad miss to be sure, yikes, that is a wild card.
     
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  13. Mr Efficiency
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    Mr Efficiency Senior Member

    If you are talking two people on board, 15' with a 20hp motor will be enough.
     
  14. cracked_ribs
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    cracked_ribs Senior Member

    That's a little smaller, and double the weight, of a plywood and glass boat I'm currently building, just as a frame of reference regarding the materials.
     
    Last edited: Mar 18, 2021
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  15. kapnD
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    kapnD Senior Member

    Are we talking about a Jon boat here?
    They are Commercially available at very reasonable prices and very low weight in aluminum.
     
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