super simple long puddle duck?

Discussion in 'Boat Design' started by peabody, Jun 15, 2012.

  1. peabody
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    peabody Junior Member

    Hello ....been looking at brockway scows ...and enjoying the puddle duck racers.
    Then? I wondered ...build a scow with hard chines like the pdr?
    Blunt square bow. And flat bottom. Say 20 foot long 48" wide. Straight 18" sides.
    Shoud move pretty good with a yamaha 9.9.
    What you guys think?
    Peabody
     
  2. lewisboats
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    lewisboats Obsessed Member

    [​IMG]

    'bout 7.5-9 knots depending on load and load placement
     

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  3. messabout
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    messabout Senior Member

    Take the rocker out of the aft bottom and you can get it to plane with the 9.9. Well if you don't over load it, that is.
     
  4. SamSam
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    SamSam Senior Member

    If you get it on a plane, you need some strakes to keep it from skidding on a turn. If it starts skidding and then that hard chine catches, you will flip right over or be thrown out of the boat.
     
  5. philSweet
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    philSweet Senior Member

    You'll have a better boat if the sides flare at about 15 degrees. 18" sides are a tad low for a twenty footer unless there are some side decks and coamings. If it's to be an open boat, add three inches or so. I agree with the others that if you plan on using more than about three hp, the transom should be submerged. At around 15hp or so, the aft should be flat- no rocker. A bit narrower at the bow helps when coming along side the dock so you don't stub into things. Helps with trailering also. A twenty footer is a fair amount of boat. Probably 800 pounds or so. Worth refining the shape to conserve materials and lower wetted surface for better performance. You can copy any of the aluminum skiffs of that size range. You'll notice most run 40+ hp on this size boat.

    http://www.youtube.com/watch?NR=1&v=we8uKBEbMLw&feature=endscreen

    http://www.youtube.com/watch?v=24xN3R7G1bw&feature=related
     
  6. lewisboats
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    lewisboats Obsessed Member

  7. peabody
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    peabody Junior Member

    Ok! Looks great! Thanks steve!
    Well then lets see? Im looking for a boat to wrap around this yamaha 9.9.
    Flair the sides ...that sounds like a better ideal than i had. Length? Optional.
    Width? Say 6'
    Open boat.
    im a big guy 290+ and the wife 140.
    So you see what i'ed like to build is something roomy.stable.and fair performance with this motor.
    About all we take is a cooler of ice and lemonade. And sandwich fixings.
    Our pleasure is boat riding.cruising the lake and the osage and sac rivers. Peaceful cruising.
    My motor does have remote controls.
    Thanks guys.
    peabody
     
  8. messabout
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    messabout Senior Member

    "Peaceful cruising" is best done at a liesurely pace and as quietly as is practical. If that is the case, then a non planeing boat may be the better option. In that case rock the aft section up as originally considered. Fuel economy, ride quality, and noise abatement will be improved.

    The down side is that the boat will not be as valuable if you decide to sell it. Almost everyone is speed crazy and a slower boat will not have much appeal for folks that are in too big a hurry to enjoy the scenery.
     
  9. PAR
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    PAR Yacht Designer/Builder

    If you want to be able to steer her reasonably, tuck in the stern chine line a bit (plan view). At that length and available power, you also need to think light, real light. A Garvey hull would be a better approach at that size and volume.
     
  10. peabody
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    peabody Junior Member

    Shucks folks ....i found her ....the boat of my dreams.

    A simply simple ..brockway scow.
    google......
    Student boat building project. BROCKWAY SCOW

    Im truly stuck on this one.
    Peabody
     
  11. Pericles
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    Pericles Senior Member

    Hello Peabody,

    Found this and thought of you. It's from 1982 and about Brockways. I'm not sure about driving 18" of the stem into the ground during construction though.:p

    http://pdf.usaid.gov/pdf_docs/PNAAN485.pdf

    Regards.
     
  12. peabody
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    peabody Junior Member



    Thank you that was excellent reading.

    Enjoyed it and learned a few things.

    Peabody
     
  13. peabody
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    peabody Junior Member

    well now ...
    about have the scow finished .. waiting on warmer weather ....
    then i stumbled upon the handy punt .
    rated for a ten horse motor .
    and also looking at steve lewis ..chugger ..
     
  14. peabody
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    peabody Junior Member



    i am in agreement ... the more i think about what we like to do ... the slower the better .. mr. lewis thinks she'll do almost 9knots .... fast enough for us.. the little yamaha is nice and quiet.

    my thinking ? instead of a 20 foot .. just go 12 or14 or 16 footer ... would fit on my flatbed better.
     

  15. messabout
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    messabout Senior Member

    The 20 footer would have about 18 feet of waterline. If you persuade Mr. Yamaha to drive the boat at 9 MPH you will be pulling a giant wave train which will cause other boaters to curse you. At 6 MPH you will not disturb the water too much.

    Waterline length plays into the practical limits of how fast you will be going. A shorter waterline is slower. You can get a rough idea of what a peaceful speed would be by taking the square root of the waterline in feet. For the 18 foot waterline the sq. root is 4.24.Use that number and multiply by about one and a half and you will get a pretty good estimate of the maximum speed in miles per hour that you would use. In that case, 4.24 x 1.5 = 6.3 MPH. This is a ball park figure but it will be fairly close to what you can expect. Backing off just a little will make things much more serene and economical..

    You will be well advised to make the boat at least 16 feet because you are a pretty big guy. Comfort and safety requires some space. You'll probably get something like 5.5 MPH with that length. But not much more.

    If you need to go faster then make the boat a planeing type. You'd have somewhere around 800 pounds of total displacement and that's about all the 9.9 would be happy with. I'd guess you could get up to 18 ...20 MPH. You'd be flogging the engine and get a bumpier ride accompanied by noise.

    Three or four times the displacement speed could be desireable in certain cases of course. Perhaps the observation of an approaching storm or some other reason to get back home in a shorter length of time.

    The water line length estimates do not apply to planeing boats.
     
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