A very small trolling boat

Discussion in 'Boat Design' started by Lurvio, Feb 18, 2010.

  1. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    Hello

    (the metric measures are correct, not sure about the US ones :) )
    (I posted this originally on the GlenL forums, so there night be some goofs left in the text)

    Bit of background first. I'm an artisan carpenter by education and hopefully in the future by profession. I have been fiddling with wood, steel and lots of other materials in the past, so the technical part of building a small boat or pretty anything comparable should not be a problem. I have very limited boating experience despite living near lakes all of my life.

    I live by a small lake (4 miles long, half of the lenght is basically river, under ½ mile wide). In the summertime I've been trolling with a rowboat, but its a bit difficult to handle both the boat and fishing pole for one person. So I've got an idea of making myself a smaller, pedal powered boat.

    I've been reading the Pedal Powered Boats-thread, but my use for the boat is quite different, so I think its better to open a new thread for this.

    The demands for the design are:

    1 Boat for one person
    2 Hands free operation
    3 Small and light enough for me to carry some distance over dry land
    4 Doesn't need to be fast (small lakes and slow trolling speed) but somewhat economical
    5 Shallow water and beaching ability
    6 Easily accessible storage for fishing gear and caught fish
    7 The look (I don't want a kayak-look for this boat)

    I like the look of the small boats like GlenL Squirt. I found a sections-drawing for their Tiny Might-design from the Glen-L-site and started tinkering with them in a cad-program I have. I scaled the drawing down to total lenght of 2 meters(6' 7'') and beam of 0.85 meters(33½''), but had to ad a bit of depth, which is now 0.47 m (18½''). By comparison the original measures of Tiny Might are 12' by 5'-1'' by 24''. I desided to go with four frames instead of six, so had to draw two frames anew, which wasn't all that hard with cad.

    Here be pictures
    Side & top view
    Frames
    Image quality aint all that good.

    The pictures give a pretty good idea of where I am at the moment. I am probably going to use spruce in the building of the boat, as I have plenty of it around. It is light enough and its been used locally in rowboats for a long time. The planking is going to be 4mm ply, probably also spruce and fiberglassed at least in the bottom. The boat will be stored dry and indoors at least most of the time.

    For steering I am thinking of a device that would attach to one of the pedals and has a strap around the pedallers calf. From that there would be a cable connection to rudder.So pushing your toe forward results in the boat turning left and with your heel would turn right.

    And then the questions:

    1 Possible stability issues. I'm 180 cm (6') long and 85 kg (190 lb).
    2 Propulsion. I'm thinking bicycle pedals, chain, 90 decrees angle gear, alum. shaft and propeller in upside-down U-shaped tunnel. (tunnel and prop shown in the pics)
    3 Propeller. I want it above the keel for beaching and shallow water. The problem is the small size, in the drawing the propeller is only 98mm (bit under 4'') in diameter and the center tube/cone is 20mm (3/4''). Is it anyway plausible to use prop this small, I think I can get the prop rpm up 5x to 10x that of pedalling rpm.

    I think thats all for now, hope to get some input on the thing from you guys. :)

    Lurvio
     
  2. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Try experimenting with model airplane propeller for slow speed. It may be right for your needs.
     
  3. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Here is a commercial product with a different design that will do just about everything on your list:

    http://www.castlecraft.com/water_bike.htm

    Scroll down to the picture what shows hinged hulls. Steering is accomplished by tilting your body to one side or another. The hand levers can be removed for 2 hands completely free fishing. The prop kicks up when beaching. Some kind of trampoline mesh platform could be worked out for the fishing accessories and handling fish.

    There also the quickfin, but it doesn't have much power:

    http://www.prophish.com/quickfin.html

    I use a 2 hands free boat similar to the quickfin powered by a small electric motor/prop for my trolling, about 30 lbs weight fully rigged.

    Hope this helps.

    Porta





     
  4. ancient kayaker
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    ancient kayaker aka Terry Haines

    I think your boat will have serious stability problems. Using a quick rule of thumb calculation it will have less than 10% of the stability of the TM. Scaling down the boat requires scaling down the crew.
     
  5. Guest625101138

    Guest625101138 Previous Member

    The tiny prop will be next to useless. It would need to spin at about 1500rpm to get you moving. Efficiency will be under 50%. You really do not want to go under 150mm.

    If low draft is a continuous requirement then paddlewheels should be a serious consideration. If shallow draft is an intermittent requirement then a folding prop on a flexible shaft gives good protection against damage. A paddlewheel of reasonable proportions will get efficiency over 70%.

    A catamaran style hull will give much better stability and be easier to move than what you propose. You can have a full desck between the hulls if you want storage. Two small sealed hulls will be strong and light. 4mm ply will be ample.

    It may be possible to steer a catamaran with a wheel on each side by setting a slight roll with body weight. Other way for more positive steering is to de-clutch one wheel but this will require some other input probably from hands. If both hands a free most of the time you can do two things at once with the hands.

    Rick W
     
  6. Lurvio
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    Lurvio Mad scientist

    Thank you for the replys so far.

    Portacruise
    Yes those designs would probably fit the bill otherwise, but to me their awfully unattractive looking. :rolleyes:

    Ancient kayaker
    I had a feel it might be tippy, but would it be too hard to keep it upright? I've done some kayaking some years ago, including going down some rapids and somehow managed to keep that boat upright. :)

    Rick Willoughby
    I kind of feared that. I think I could fit that design with an 8'' prop, going 1/3 of the height under keel and 2/3 inside the tunnel, with folding blades if I hit something. I had not considered the paddle wheel, it might fit in a tunnel hull kind of design? It would also be easier to fit a drivetrain in.
    ___

    I am probably a bit hard headed with this, but I don't want to abandon the single hull design just yet. What difference would a flat bottom make, or even a bit concave? The catamaran-designs have a common feature that the seating is going to be a bit high for my liking. I would like to get my hand in the water without too much of trouble. The shallow water issue is not going to be very important in fishing, but I'm sure I'll be doing lots of shoreline surveys in it, so it cannot be forgotten.

    Thanks again

    Lurvio
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    With a single hull you got excess drag compared to multihull alternative. If you really want to sit lower then consider a canoe hull with ama..
     
  8. Lurvio
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    Lurvio Mad scientist

    How much of a factor is the drag going to be, when the trolling speed is around 1 km/h? Some numbers would be nice. :)

    Lurvio
     
  9. portacruise
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    portacruise Senior Member

    Depends on conditions for your Lake. My top speed is about 5Km/hr and it is not enough for a small protected lake at times. Wind is the biggest factor and is unpredictable so trolling on a line can be an issue. Mostly I go to narrow rivers with high banks for that reason because shade is plentiful and wind is blocked off. My trolling speed can vary from 2-5Km/hr for the type of fish I go for. Your boat would be much heavier and not moved by wind so much, but still you might have trouble with consistent speed.

    The links I sent were just for ideas on NO HANDS steering, you can make some beautiful catamarans with recumbent seating like Ricks.

    I spent 6 months trying to make paddlewheels work. Tried every form of steering using the paddlewheels including leaning and slip clutches without success. Any variation seemed to change the level of immersion so that control was not achieved. But there are better men out there that might be able to figure a way to do it.

    Porta

     
  10. Lurvio
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    Lurvio Mad scientist

    I don't think wind is going to be all that big a problem, because I can pick the weather I'll be going to the lake. Evenings mostly.

    I'll take a look at the drawings and see what I can do with them. I'd like to at least keep some of the profile untouched, so tunnel hull is going to be the next try. Even if I go for the paddle wheel, I'd use a rudder for steering, its so much simpler than clutches and the kind. :cool:

    Lurvio
     
  11. ancient kayaker
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    ancient kayaker aka Terry Haines

    My first design was a Vee-bottom canoe. It was pretty but quite unusable, far too tippy for anyone larger than a small child. In such a small boat, the vee-bottom created bouyancy below the CoG which de-stabilized the boat.

    Then came a flat-bottomed canoe; I reasoned that the flat bottom was the most stable hull configuration. it was awful, never actually tossed me into the water but I never felt safe in it and it was slow and cranky.

    By this time I had realised a couple of things:
    1) small boat design was a lot more subtle than I had expected
    2) Center of gravity height must be kept low in a narrow boat

    My next design was a 5-planker, with a narrower flat bottom which seems counter-intuitive but it lowered the CoG. From the bottom the bilge planks slope up to meet gently flared sheers at the waterline where there is still less beam than the flatty. This is a lovely canoe, stable enough for a careful beginner, effortless to paddle, handles waves and wash with ease fast and tracks like a train. The first paddle was a true Ahah! moment.

    I think Teddy's idea of a cat might be the way to go, but it might be simpler to forget about human-power and buy a cheap electric trolling motor.
     
  12. portacruise
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    portacruise Senior Member

    Wind is not the only consideration for swamping. There are wakes from power boats, and handling fish where you stand or lean over to untangle. I once caught a 20 kg fish trolling with my 14Kg, 2m boat, which was a 30 min ride, and landing meant running to shore where I could stand up for stability.

    I couldn't get a rudder to work with paddlewheels because turning alters the amount of dip for the slats and accentuates the whole balance in the direction in which you turn. Also you have to work out the hands free rudder. My paddlewheels were mounted at the front end of the catamaran so that might have made things worse. There have been some excellent racing catamaran versions with center mounted wheels, so that might be the answer.

    Porta

     
  13. TeddyDiver
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    TeddyDiver Gollywobbler

    The problem with light small boat with a wide beam is the lack of inertia compared to drag. So when rowing it will almost stop btw your strokes. Another problem is the lack of directional stability.. Thou some fish may find irregular swimming pattern of the lures quite attractive :)
     
  14. Lurvio
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    Lurvio Mad scientist

    I did some calculations for the original design and it looks like I'd be sitting (bench surface) within an inch of the surrounding water surface, probably a bit below. I don't have enough knowledge to calculate the vertical CoG, longitual is about 75 cm forth of transom. I don't know it these help any. :rolleyes:

    Portacruise
    As far as the paddle wheel in my design, there would be one wheel in the stern, with rudder close behind. I don't see why that setup would have problems working. Is there a reason the ankle movement system I described in my first post wouldn't work for steering?

    TeddyDiver
    I can imagine that happening, if I were to row that little bucket of mine. :D Shouldn't be so much of a problem with pedals thou. 30 to 40 meters of fishing line between the boat and a bait will kind of ruin the nice swimming patterns. :p
    ___

    Here's a bit more information of my lake. There are three fast boats on the whole lake (did a trip around the lake last summer), none of them are very active. The biggest waves around here are about 30 cm and the only way I would get in those is swimming. :) The fish aint big either, 10 kg tops. My best one last summer was a 2,2kg pike.

    Lurvio

    edit: smileys
     

  15. Guest625101138

    Guest625101138 Previous Member

    The paddle wheel has the same area requirements as a propeller if you want to get acceptable efficiency.

    The size you need to be considering is two wheels at least 600mm diameter with blades no less than than 200mm wide and immersed to 100mm. Smaller blade area will result in a lot of wasted effort.

    An 200mm diameter folding prop will be tolerable.

    Rick W
     
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