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Thread: Flat bottom hull questions

  1. #1
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    Default Flat bottom hull questions

    Hi new to the forum, I have wondered about the idea of a flat bottom hull with a pointed bow 30' long with a 4.5' beam for taking a few friends on weekend trips on canals and calm rivers. Would a boat of that size be too long for the beam and having a flat bottom hull? I have a concept design in mind but don't intend on it being a planing hull but more in mind of a slow shallow really really big square stern canoe capable of carrying 4 or 5 people plus gear. I was going to just put around with a 9.9 tohatsu I have on a 15'L 3.5' beam boat I built of similar dimensions and it performs quite well for me and my wife for being a "homemade" design. I just fear 30' is too long for a flat hull and 4' beam is too narrow for such a length. Any info is appreciated and please no bashing I'm not an expert but if it can be done I would like to build it. Thanks everyone

  2. #2
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    Default Re: Flat bottom hull questions

    Welcome to the Forum!

    As fun as it can be to design your own boat, it can also be a very expensive way to discover your limitations and mistakes. With the amount of money you'll be spending on a boat that size, buying plans from an established modern designer is a good investment.

    I doubt many craft that length are that narrow, but you can certainly find some that are close -- several by Bolger come to mind. His Sneakeasy is a very cool boat and might meet your needs and design specs -


    https://i.pinimg.com/originals/ed/95...1ebcaf6be2.jpg

    Bolger's Tennessee is even closer -
    http://www.duckworksmagazine.com/00/...ding/index.htm


    If that's too sporty / runabout-like, there are a number of canal boat designs that will be beamier (wider) but much more comfortable -- and mostly cabin.
    https://www.duckworksbbs.com/product...venezia-id.htm

    Mic Storer has this 35' beauty that might work -
    https://www.storerboatplans.com/boat...at-canal-boat/
    Or this 23' design -
    https://www.storerboatplans.com/boat...rd-motor-boat/

    If you really must design it all yourself, try looking at existing plans to see what others have done to get a feeling for the design limitations. There are also some good threads on this Forum about flat bottom boats, how they handle various conditions and perform under power.
    https://www.tapatalk.com/groups/cape...ts-t19484.html
    Last edited by Thorne; 12-07-2018 at 01:25 AM.
    "The enemies of reason have a certain blind look."
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  3. #3

    Default Re: Flat bottom hull questions

    Phil bolger designed flat bottomed boat called "naval jelly." It's 31 feet long and about 4 feet wide. It was designed as a human powered vessel for a race where contestants had to paddle (row?) up a river, pick up a bunch of trash and return to the start. Construction is super simple and flimsy, plans are in his book "the folding schooner and other adventures in boat design."

    But why make it so long and narrow? Those proportions are usually reserved for very low power, or human powered vessels.

    Joe Dobler designed a 23 1/2' x 5' flat bottomed rowboat that might more practical for what you want to do. It has a motor mount and plenty of room for passengers and gear (see pic below). Dobler was an aeronautical engineer so you can be assured the hull is optimized for low drag and the structure is efficient. Plans are just $20 at duckworks

    https://www.duckworksbbs.com/product...ttayawl-id.htm

    marietta_yawl.jpg

  4. #4
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    Default Re: Flat bottom hull questions

    Bolger again: He designed exactly the boat you describe. A narrow, long," skiff," that went well with a 9.9 on its transom. The name? Slicer

    Read about it here: https://www.duckworksmagazine.com/05...ib/1/index.htm
    Screen Shot 2018-12-07 at 9.12.05 AM.jpgScreen Shot 2018-12-07 at 9.12.10 AM.jpgScreen Shot 2018-12-07 at 9.12.19 AM.jpg

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  5. #5
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    Default Re: Flat bottom hull questions

    Good call Kevin. A boat like that would take four or so friends and camping gear all over selected lakes and rivers.

  6. #6
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    Default Re: Flat bottom hull questions

    Welcome to the orum and will be interested in your progress. Long and narrow have been traditional for low powered boats. I second the idea of buying plans from a recognized designer. A good way to avoid very expensive mistakes. You might want to take a look at Atkin's Russell R.

  7. #7
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    Default Re: Flat bottom hull questions

    Quote Originally Posted by Breakaway View Post
    Bolger again: He designed exactly the boat you describe. A narrow, long," skiff," that went well with a 9.9 on its transom. The name? Slicer

    Read about it here: https://www.duckworksmagazine.com/05...ib/1/index.htm
    Screen Shot 2018-12-07 at 9.12.05 AM.jpgScreen Shot 2018-12-07 at 9.12.10 AM.jpgScreen Shot 2018-12-07 at 9.12.19 AM.jpg

    Kevin
    Yes that is kinda exactly what I had in mind and I agree on using proven plans for a boat of this size. I just wasn't sure about the existence of such boat plans and how large a flat bottom hull can be made with practical handling and stability in mind, as for being long and narrow the rivers I will be using it on are semi shallow (3 feet to 9 feet on average) and is very calm most of the year other than the rainy season. Im an adventurer who likes to go low and slow to take it all in so low power is my route, im looking for something that can be large enough to take several people onboard plus gear for a few days, allow for some shallows where cruisers and cuddys can't navigate, some amenities such as radio, lights, charging station for devices such as phones, cameras, go pro, etc (were always within service) a berth would be nice but not necessary. Now as to why "so" long is the gear we carry takes up decent space and wanted something to give us extra room so we don't feel so cramped. We've done it before in my 15' boat and 2 we no nah canoes but we didn't like having to remove everything from the water setting up then tear down, clean up, the works and then during the day your crowded and paddling fully loaded. It kinda puts a burden on the relaxing aspect ....so there's where a boat comes in mind where we can keep pretty much everything except tents and a cooler for nights. My concern is the stability of a flatbottom being that narrow for it's length if a person wants to stand up and move around a little, and how hard it would be to turn in confined spaces given that I would be using a trolling motor as a bow thruster.

  8. #8
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    Default Re: Flat bottom hull questions

    Take a look at the Sharptown Barge, which should be about the easiest to build. Our hosts here sell plans through the WoodenBoat Store.

    Easier to build in plywood than cross planked, of course.

  9. #9
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    Default Re: Flat bottom hull questions

    I can think of one long and narrow, flat bottom boat, that was, maybe, discussed on the WB Magazine years ago. I think it was called a ".......War Canoe" and the owner used it as a commuter boat. It was a narrow, flat bottom, double ended, plywood (?) boat about 50 ft LOA. It had an open cabin amidships and that also housed a three cylinder, low speed gas engine.

    That is a bit bigger than you want perhaps, but could serve as an inspiration.

  10. #10
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    Default Re: Flat bottom hull questions

    Quote Originally Posted by ahp View Post
    I can think of one long and narrow, flat bottom boat, that was, maybe, discussed on the WB Magazine years ago. I think it was called a ".......War Canoe" and the owner used it as a commuter boat. It was a narrow, flat bottom, double ended, plywood (?) boat about 50 ft LOA. It had an open cabin amidships and that also housed a three cylinder, low speed gas engine.

    That is a bit bigger than you want perhaps, but could serve as an inspiration.
    Absolutely I just wanted to know if a flat bottom boat can get 30 ft long be narrow and be stable. Canal narrowboats in the UK have flat bottoms but they act as displacement hulls for slow canal speeds, my question is can the same apply to a non planing flatbottom that has less draft than a narrowboat. I'm trying to steer clear of a v bottom for river purposes

  11. #11
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    Default Re: Flat bottom hull questions

    It's a popular form all over Asia. Longtails, for example.

    49458097longtale-boat.jpg
    -Dave

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    Default Re: Flat bottom hull questions

    Quote Originally Posted by Woxbox View Post
    It's a popular form all over Asia. Longtails, for example.

    49458097longtale-boat.jpg
    Great example, but I'm wondering let say stretch a jon boat but point the bow so it can cut through the water rather than try to ride up on top of it

  13. #13
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    Default Re: Flat bottom hull questions

    These slipper launches were originally flat bottomed with a bit of rocker, slender, easily driven and elegant.


    It really is quite difficult to build an ugly wooden boat.

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  14. #14
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    Default Re: Flat bottom hull questions

    Quote Originally Posted by TheRiverGrimm View Post
    Great example, but I'm wondering let say stretch a jon boat but point the bow so it can cut through the water rather than try to ride up on top of it
    The "bow out of the water" element depends on the design - some like Bolger's Sneakeasy and Slicer, and Welsford's Navigator & Pathfinder are designed to have the bow out of the water.

    But if the main goal is to have the boat handle well in very shallow rivers, it sure seems to me that the length will be an issue. When you cross a riffle that pushes the bow up, the stern will go down -- and vice versa. There's a very good reason why driftboats (designed for shallow rocky rivers) are relatively short and beamy. Much depends on the rivers and water conditions, so you may have to build it and find out.
    "The enemies of reason have a certain blind look."
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  15. #15
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    Default Re: Flat bottom hull questions

    I've still been searching for existing plans but cannot find what I am looking for. I'll explain the best I can. I kinda have in mind a narrowboat type hull that's of wood construction (I'm not a steel worker) with less draft say around 8 to 12 inches with a square stern for outboard rather than inboard for weight purposes and practicality. And eliminate the cabin on it whilst shortening the length of a traditional 50' narrowboat to a 30' to be trailerd as I want to keep it covered at my house when not in use. I am unaware of any boat types like this any help is appreciated

  16. #16
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    Default Re: Flat bottom hull questions

    Quote Originally Posted by TheRiverGrimm View Post
    I've still been searching for existing plans but cannot find what I am looking for. I'll explain the best I can. I kinda have in mind a narrowboat type hull that's of wood construction (I'm not a steel worker) with less draft say around 8 to 12 inches with a square stern for outboard rather than inboard for weight purposes and practicality. And eliminate the cabin on it whilst shortening the length of a traditional 50' narrowboat to a 30' to be trailerd as I want to keep it covered at my house when not in use. I am unaware of any boat types like this any help is appreciated
    The reason there aren't any plans is that, as far as I know, nobody uses long boats like those in shallow rocky rivers. Long ago fur trappers and traders used long canoes and bateaus, but I suspect they portaged when they hit shallows -- or avoided them altogether. If you look up the average depth of water in the canals used by narrowboats you'll find it runs from 2.5 - 4' and very flat --- so that's the type of waterway those boats are designed to operate in.


    For **really** shallow water you may need a jet drive outboard as seen on some rivers out here.

    But the big issue that I see is the laws of physics -- taking something that long over uneven rocky shallows will probably result in quite a bit of impact and scraping if not outright damage or capsizing. From years of boat camping I can say that 30' is an excessive length for 4 people and gear! If you want to build it and find out, great -- be sure to let us know how it works out.



    https://yamahaoutboards.com/en-us/ho...rust/jet-drive
    Last edited by Thorne; 12-09-2018 at 11:32 AM.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  17. #17
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    Default Re: Flat bottom hull questions

    There is this



    From https://archive.org/details/fishingb...78mbp/page/n13 If you open the website link and flip through there are several simple to build flat bottom craft of different sizes.
    Another sample


    It really is quite difficult to build an ugly wooden boat.

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  18. #18
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    Default Re: Flat bottom hull questions

    Quote Originally Posted by Peerie Maa View Post
    There is this



    From https://archive.org/details/fishingb...78mbp/page/n13 If you open the website link and flip through there are several simple to build flat bottom craft of different sizes.
    Another sample


    Now that's more like what I have in mind

  19. #19
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    Default Re: Flat bottom hull questions

    Let me put in another plug for the Russel R. This boat would be much more manoeverable and perhaps suit your needs.
    http://www.atkinboatplans.com/Oar/RussellR.html

  20. #20
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    Default Re: Flat bottom hull questions

    Although it isn't a flat bottom, another Atkin design, Sergeant Faunce.
    http://www.atkinboatplans.com/Utilit...antFaunce.html

  21. #21
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    Default Re: Flat bottom hull questions

    Hi TheRiverGrimm,
    I joined this forum for precisely this reason - community involvement. Those of us that are committing ourselves to designing/personalizing/building a wooden boat need this type of input. That said. . .

    We've (better half and I) committed to building and modifying a flat bottomed boat because as you, TheRiverGrimm, live on a canal where draft is a big issue. We live on a canal that connects to the pristine Myakka River, in North Port, Florida. We began our search for a suitable vessel many months ago after our "fixer-upper" experience came to an end [if it ever does???].

    Peerie Maaposted a number of plans for boats that the UN made available for those wanting to build durable fishing flat bottoms. A super effort no doubt. We perused these too, as well as those offered by a dozen or so websites that offered good designs at very reasonable costs. We knew what we wanted but did not want to complicate our lives with a design that would consume hundreds of hours even though we have the time - we're retired. As avid sailors - we sailed the Pacific for 5 years from San Diego, Ca, to Chile, South America - we knew what we wanted in a boat for our new environment.

    We settled on a simple design and easy construction vessel when we chose our Spira Albion 19 foot flat bottom Dory. Please be assured that we do not endorse or promote any designer or their products and have no connection at all with this company. We mention this design because as you, we wanted a canal/river boat that can be easily built, be rugged and can take a few modifications to "personalize" it for our particular use. Also, 19/20 feet is manageable in a canal and river - we've already been down that route, or is it stream (?)

    We plan on starting our build after the start of the new year as we must clear an area between two pine trees next to the canal's seawall. We plan on posting to this forum as we begin the effort.

    Hope this gives you a few more ideas. . . or at least food for thought. Good luck in your search.

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