Poling Platform on small boat

Discussion in 'Stability' started by ddrdan, Mar 28, 2009.

  1. ddrdan
    Joined: Mar 2009
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    Location: Raleigh NC

    ddrdan Junior Member

    I want to put a poling platform on a 12’ flat bottom boat. I’m convinced there is a way! With this economy I’m forced to give up on the big flats boat and design a 1 man, or possibly, 2 man boat.

    I have no experience in boat design. I’ve been self educating myself for about a month now from web based information. I believe I have a grip on the basics. The balance from fore to aft is ok. The poling platform weighs 28# and I’ve compensated with the weight of a deck forward of the platform

    To achieve the height I need, it will require outriggers. I have designed retractable outrigger arms but I need help in determining how far out they need to go and the volume required in the pontoon to counteract the tipping while I’m on the platform.

    The pontoon can not exceed 24” in length. I would also like the minimial extension distance required. The retractable arm area is limited. Because they will not be used when under power; what hull or shape would displace / stabilize the best?

    In reviewing outriggers for kayaks & canoes it looks like the rigs don’t stay in the water and they tip back and forth. I am assuming my requirements will need the rigs to produce constant lift from both sides when extended??

    Below are the general specs on the project. Any help you can give will be greatly appreciated.

    [​IMG]
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    [​IMG]
     
  2. alan white
    Joined: Mar 2007
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    alan white Senior Member

    Pole from a low base. Your high platform will be a bit hairy in practice. Your pontoon floats really would need to be orders of magnitude larger to provide adaquate bouyancy.
    You appear to show about a 5 1/2 ft beam with floats out. This is absolutely too narrow to pole at the height shown even if the floats were a full 12 ft long and 18" diameter and the boat was a catamaran.
    Consider a catamaran 8 ft wide with at least 12 ft x 12" floats if you want to stay dry.
     
  3. ddrdan
    Joined: Mar 2009
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    ddrdan Junior Member

    Thanks for the help Alan. Can I bother you again with a few more questions?

    I can find any data or formulas on the web for the ratio of height to beam? Also, I will be in calm waters when poling, will that make a difference as to taking the high side of a calculation when determining the height?

    My problem is the location of the seat for tiller steering. The platform needs to be as close to aft as possible. Even lowering it and putting it over the motor area would put the weight too far back, wouldn't it?

    I can't use the seat without 34" of clear above it. Any ideas on a location change with a lower height and still have access to the tiller? I've seen some platforms attached to the gunwale? Wouldn't that create rotation in rocking?

    Then it would be a barge and not a backwater flats boat. :D :D LOL
     
  4. ddrdan
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    Location: Raleigh NC

    ddrdan Junior Member

    NOTE: Sorry for the large pics in my post. I just noticed everyone uses a thumbnail. Just read the help files and I will do this in the future.

    Sorry
     
  5. alan white
    Joined: Mar 2007
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    alan white Senior Member

    To be honest with you, I don't think your problem is as simple that a formula might solve it.
    So many interlacing factors must be taken into account---- especially tendancy to roll, which can be initiated by small movements aboard when there is a weight high up. Just as a trailer can whip back and forth if it is carrying a pendulum-like object (this happened to me carrying a rolled up carpet and it threw the truck off the road!).
    You would have to analyze all weights and underwater shapes according to their location so it would be far easier to approach the problem from a more practical POV.
    I suggest you do a mock-up in a safe place, where falling overboard is no big deal. Get a friend to move around the boat while you attempt to pole from various heights.
    You asked if the platform could be attached at gunwale height. Whether attached there or on a walk-around pedestal of the same height, the rocking you mentioned will be exactly the same.
    I think your only clear option is to decide what choices you have for poling positions and cobble up a prototype.
    If you already own this boat, stay very low. Some canoes have a wider waterline beam. If you would consider a new, wider boat, go wide and long (say, 5 x 16) and flat-bottomed hull and then mock up your ideal poling platform and see if that works.
     
  6. ddrdan
    Joined: Mar 2009
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    ddrdan Junior Member

    Thanks again Alan for your time & info. Just read your post.

    I had the same thought as you on a prototype. I fabricated a wooden leged table of sorts with different stops for the top height. I found the best location was over the area between the first and second seat. I was able to get 12" above the gunwale without any serious roll.

    I found positioning the legs on the bottom of the boat in lieu of gunwale height did help.
     
  7. guinue
    Joined: May 2009
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    Location: merritt island florida

    guinue New Member

    im here with you

    hi, my names austin scott
    and i was wondering if it would be possible to but a poling platform on my boat i have a 14ft guinue (american eagle) with 2 seats the with is about 3ft in the middle and the back is about 2ft wide
    if any 1 can help me find out if i can put a poling platform on and were and wat size i'd be very greatful.
    please and thank you.
     
  8. ThomD
    Joined: Mar 2009
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    Location: TO

    ThomD Senior Member

    I built myself a fishing cat. It can be, and has been poled. It doesn't have the high position you want, but it could very easily. I don't live in South Florida, but if I did I would campaign it on the flats. I built mine to be a green efficient, bass fly fishing machine. And I use it these days for carp fishing, for the most part. That is flat fishing in my area. If I wanted it to carry a more powerful motor, it would benefit from straighter lines aft. Even light motors nearly require the flatter run aft.

    This is a pretty light boat, two people can lift it. I have had 4 adult and 6 children on it, and it is always stable and works nicely.

    http://www.duckworksmagazine.com/01/projects/bassackwards/index.htm
     
  9. guinue
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    guinue New Member

    thank you
    my boat only fits 2 people 3 people max its exactly like a canoe but with a flat back were me 40 lb thrust minnacota trolling moter goes
    i'd just like to know if a poling platform can go on it the dimensions are....
    back= 2ft wide
    middle= 3.5 ft wide
    the coping is 3inch
    i believe its possible but i want some 1 elses word on it.
    thanks
     
  10. ThomD
    Joined: Mar 2009
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    ThomD Senior Member

    Should work. If you already have the boat, then get it in a safe place and put some large box or small step ladder back there so that you body will be at the correct height and position. Get a few people around the boat and climb up and see how unstable it is .

    If you think you need ouriggers, set a piece of wood across the boat to the correct width, and attach it. Take a fish scale or even a bathoroom scale could be used under the stick, and while holding onto something tip the boat and see how much force is brought to bear, now compare that to displacement of the floats you plan to use. Another alternative would be to use those big bottles they sell for water coolers, or square ice boxes, fenders, etc... for a mock up.

    It is faster and far more reliable to do a test than to chat away on this kind of subject. World class designers get stability wrong on famous boats when the situation is novel. It will be a custom situation based on your wind and wave conditions, your weight, and how much you move around while poling, how active you are jumping up and down, etc... But a few minutes of testing. Even some folks holding the beam and judging the load by hand will tell you a lot more than speculation. Your basic idea is sound. I would guess a scow shaped ama would be better, square crossections harden off better per inch immersions, and can function better on motor type applications.

    I think there could be some problems with the fisherman position person moving around and tipping you off.

    Another problem is that one the flats boats the platform is over the motor, and the great weight of the boat counterballances that position, But in your case you have the platform inboard. Will you be able to get to the motor?
     
  11. guinue
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    guinue New Member

    Will you be able to get to the motor?


    thank you for all your help

    and ill be poling in the flats but yes i should be able to reach my trolling motor with my extension piece i have for it.

    i appreciate it ill be doing some tests soon
    lol when i eat **** ill be shure to have it on video =]
     
  12. messabout
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    Location: Lakeland Fl USA

    messabout Senior Member

    Guinue: Careful man, there are big sharks in th Banana River.
     
  13. guinue
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    guinue New Member

    yea ive cought a few at night usualy black tips:)
     
  14. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    if you have the boat why not take some domestic fold out steps and try puttting them in different positons and climbing up ....will give you a simple quick idea of whats possible ..
     

  15. srimes
    Joined: Sep 2008
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    srimes Senior Member

    I think for something simple non-critical like this I would just guess-and-test for a solution. It's not like the stability is needed for safety in adverse conditions, it's needed when fishing calm shallow water. And it's not like you'll be on a big platform with your buddies and moving around, it'll just be 1 person confined to a small area.

    2 basic design concepts:

    1: the floats provide lift based on how much water they displace, so look at how the displacement changes as they become immersed. A narrow, deep-v bottomed float will enter the water gently and slowly gain displacement and therefore lift. Great for a soft ride a speed, but not the best for maximizing initial stability. Wide floats will have a greater displacement change, so at rest the floats should be at maximum width. If they're round they should be immersed half way. This may mean they're deeper than the boat, so you may want to consider flat-bottom floats.

    2: the resistance to tipping is a function of lifting force times distance from the center of the boat. A small float on a long arm can help more than a large float right next to the boat. How wide can it practically be? Pick a comfortable distance and try it. If it isn't stable enough increase the width or the size of the floats.

    Let us know what you come up with.
     
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