A kayak, kinda?

Discussion in 'Boat Design' started by charlief1, Oct 25, 2015.

  1. charlief1
    Joined: Oct 2015
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    Location: Texas

    charlief1 Junior Member

    Several years ago I got the bug to build my own boat, and should've gotten my head examined instead.:D I ended up looking at a lot of designs and settled on a pirogue since this was my first and it was simple. Did a lot of reading and even used autocad to design it. It turned out ok and I used it for a while but noticed some design issues I didn't like, especially in windy situations. It was damaged and instead of fixing it right away I let it sit so it's not worth repairing at this point.

    I decided to make something a little more versatile to replace it now and I think I've got a good solution for a basic fishing/pleasure boat with a few twists. I'm not an engineer but I've done quite a bit of fabrication in the automotive field since I'm an automotive tech and deal with race cars with some of the stuff I do.

    What I came up with I call a canyak since I'll be sitting high, but not on top. OAL is 13.25' with a beam at between 40 and 42". This is a multi-chine design with a base width of 32" and a slight V shape on the bottom. It's primary propulsion is by kayak paddle but I'm thinking about adding a small sail just in case I want to get across some of the lakes in the area easier. Yes, it's wider than a kayak should be, I know. I always like to do design models so I can get a better idea of the shape of what I'm building and this model is made out of luan paneling that I had laying around. I reduced the measurements x10 and then made it's twice that size so I could work on it easier. The top front has a slight curve to it and the top back is flat but angled to the back to help shed water easier, as well as give me a standing surface if I want to stand for casting or something else.

    This is the model I've been working on and I like the way she looks so far. The opening in the center ended up being 4.5' long and 30" wide so that will allow for equipment and I think there'll be enough displacement for 2 if I'm not in choppy water. The height works out to around 1.2' and I should be at 10-11" sitting, but the seat can be taken out for sailing. I haven't worked out all the details yet but I thought I'd show it off and get some feedback to see what others thing. I'm looking for stability more than speed in this design since it will be used in backwater areas more than open water spots. The square stern is for the rudder when and if I add one for the sailing idea.
     

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  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The reverse curve on the chine (top center photo) will create a lot of drag.
     
  3. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Gonzo spotted a problem right away. You need to give the bottom some rocker. Calculate the draft amidships and raise the forefoot to about one to one and a half inches below the water line. The transom end should raise perhaps one inch above the water line. I think that you have too much angle on the lower chine at the transom.

    If you mean to paddle or row the boat then place some emphasis on minimizing wetted surface area.

    To use a double paddle, just about the limit beam is 35...36 inches. With widths much more than 30" you will need to use a long double paddle If you make the boat 40...42 inches wide, figure on using oars.
     
  4. charlief1
    Joined: Oct 2015
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    Location: Texas

    charlief1 Junior Member

    The idea of the width came from me using a bass buster and a kayak paddle. Instead of the original seat I'm using a low beach chair and it works fairly well, but it does have a 48" width and a learning curve. It's also a bit of a pig with the dual pontoon style bottom.

    The model was a pain to make since it's luan paneling and full sized one won't have wood as thick by scale. If you look carefully there's some rocker in the front and a slight V to the bottom. This is exactly why I build a model before moving on to the full sized one. The pirogue had several models made before I finalized and built it.

    You guys are helping me to refine the design, which is what I'm after here. By increasing the angle of the second panel it will reduce the drag some, but how much should I bring it up? I've estimated that the middle panel is at a 30 degree angle from the bottom. Will it work better if I make it closer to a 45 degree angle? I'm trying to keep this wide for stability more than speed and will mostly be used for fishing and backwater paddling.

    Once I get the design locked down I may be trying to make my own peddle system prop drive and I've already got a few ideas on how to make it work in a bit different manor.
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Just stick an extension on the stern, bringing everything more to a pointy end.
     
  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Try thin cardboard. It is much easier to work with.
     
  7. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    A shrewd designer/builder once said the "the primary purpose is primary" . Those are words of wisdom. So what is the primary purpose of the boat? If it is for fishing then space and stability are high on the list of wants. If it is to be a boat for paddling then that will imply other things, like wet surface area, entrance angle, and so on. Consider the distance that you may paddle or row. If the fishing hole is 4 miles away you may want to opt for a design that is the most easily propelled. If it is only a few hundred yards away then comfort and stability may be the most desirable design aim.

    The boat will have much more initial stability if you make it a simple flat bottomed design. The flattie will have more drag than the one you have modeled, but the model that you have shown will be pretty tender. In any case, small boats like this do not begin to stiffen very much until about five degrees of heel. An off hand example is a 12 foot 6 inch skiff with 40 inch beam. Let it have a displacement of 350 pounds which will require a draft of 3.5 inches. Place a10 pound weight on the rail at midships. The boat will heel one degree. 51 pounds at the rail will give her 5 degrees of heel and 99 pounds will cause 10 degree tilt. Note:these are ball park figures only. They apply to a flat bottomed skiff with 40 chine width. The bevel chined option will be more sensitive and tolerate less weight at the sheer line.

    A bevel angle of 30 degrees is reasonable. If you increase that angle the stability will diminish, depending on how high above the waterline the second joint is.

    You are on the right track with the beveled chines because it will be better in several ways including both the items mentioned above. But it will not be happy with having you standing up to fight a big fish. That depends, to some extent on your size and agility of course. There are also structural advantages to the one you have modeled because it reduces the width of the widest panel; the bottom. It also helps resist twisting.
     

  8. charlief1
    Joined: Oct 2015
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    Location: Texas

    charlief1 Junior Member

    Primary use is fishing and some paddling, but very seldom will it go that far. The only extra thing will be a small sail for going across large bodies of water to get to another inlet for fishing. Using it for hunting would also be considered since I live near an area where the corp of engineers have a lake and I can hunt there. The creek leading to the lake and the Brazos river or the Trinity river system in Texas is where it might get the most workout. This isn't for offshore use or fishing in the middle of a lake and I'm more interested in overall stability than speed. The best was to describe the bottom (I'm not an engineer after all) is a 3/4" rise from the middle of the bottom to the edge center of the first chine. Not a lot of angle overall but enough to give it better control of direction. The pirogue had a flat bottom and tracked ok but if you weren't careful it would go to one side at times.

    It may be taken on a river camping trip once in a while so it is possible that it goes some distance, but it will be down the river, not both directions.
     
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