Fishing kayak

Discussion in 'Boatbuilding' started by ShagRock, Jan 4, 2009.

  1. ShagRock
    Joined: Jan 2009
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    ShagRock Junior Member

    I am looking to build a small kayak or canoe for fishing lakes and close to shore ocean fishing. I like the idea of a sit-on style that has flotation to self right, car top, and easy for one person to carry. I see there are plenty of rotomolded fishing rigs, eg. Cobra Fish and Dive and those from Ocean Kayak and Viking. Has anyone an idea or info on whether such designs can be mimicked using wood frame, composites, or materials like nylon.

    May your big jib draw!
    Newfie
     
  2. rasorinc
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    rasorinc Senior Member

    I used to have a neat picture of a fishing kayak but lost it. The design allowed you to stand up and cast. It was designed so that the aft part would split apart into 2 self contained pieces with flotation. When this was done it looked like a Y. When done fishing he pulled them together and latched them His seat was at the center forward of where the 3 pieces meet. It was unique and should not be to hard to design. Stan https://www.boatdesigns.com/products.asp?dept=185
    https://www.boatdesigns.com/products.asp?dept=186 You can imagine cutting the aft end into 2 pieces seperate from the hull closed off with 1/4" ply and filled with flotation 4 hinges and a latch. Would not even add much weight. If done to the aft 1/3 of the hull it should give necessary stability.
     
  3. ShagRock
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    ShagRock Junior Member

    That's a design I haven't seen before and certainly worth a look if I can track it down. I think I would prefer 'low weight' tech seat that swivels, has adjustable back, lock position, etc. Perhaps a 13' Loa with 32"+ beam would give adequate stability, but I am not experienced enough to evaluate speed and maneuverability. I looked at the Sabalo design by Jem which offers some build possibilities.

    I also read threads by Ancient Kayaker especially his posts to Millionwords inquiry on kayak. I am working on a design for a slip-out outrigger that could be used for drift control when fishing or to employ if water gets rough (paraw/proa type things come to mind). I'v heard that 26oz nylon is 'quite tough' but maybe s&g plywood is the way to go - others here may have some 'seaworthy opinions' to offer on that. I also reviewed an Arch Davis penobscot skiff where the plywood is glued and screwed to stringers, which I think might be a good technique for kayak or canoe.

    May your big jib Draw!
    Bayman
     
  4. rasorinc
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    rasorinc Senior Member

    I'm a wood boat builder so that is where my vote goes. If you do use 1/4" plywood get 4 ply. Doug Fir 1/4" is 3 ply. Meranti "Hygro-Tek" BS 1088 I think has 4 plys and in 1/4" should be the same price as DF. Okoume "Joubert" BS 1088 has 4 plys and is quite light but cost 70% more than the others. You probanly will use only 2 sheets and the weight is important to you then use Okoume Here is a site for plywood that gives you info and pricing. Their prices seem high to me.
    http://marine-plywood.us/

    Do you like inlay? http://www.boatdesign.net/gallery/showphoto.php/photo/4112
     
  5. ShagRock
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    ShagRock Junior Member

    rasorinc
    The stand-up kayak you referenced is at this link:
    www.hammacher.com/publish/11098.asp[/url] - 38k -
    It's $2000. I think I'll opt for building my own for a lot less. I'll take your advise and look into marine ply here 'up North'! I'll continue to work on creating some detachable ama for extra stability. I once jerry-rigged a sealed aluminum tube on a canoe for large lakes. It worked but the bamboo amas are much nicer. I'll check if bamboo tubes are available here.

    Fishing in a sit-on should be reasonably comfortable (after watching guys fly fishing in pontoons and belly boats):p . That won't do for me because I like to explore around.
    1) Any suggestions re light weight outrigger?
    2) What is the general opinion on creating your own design versus buying build plans?

    May your big jib Draw!
    Bayman
     
  6. rasorinc
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    rasorinc Senior Member

    I always buy professional plans for the hull. Then I do my thing after that. This way I know the hull design will do what I want the boat to do and that all factors have been incorporated in the design.
    For a simple outrigger look at Stryene pipe. Unlike PVC it is very light and you could fiberglass it for more strength. It has a crush strength of several thousand pounds I believe. Most lumber yards carry it. Stan
    I'm glad you found the Y plan--Thanks PS make sure stryene is compatable with epoxy..Styrofoam is.
     
  7. ancient kayaker
    Joined: Aug 2006
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    ancient kayaker aka Terry Haines

    I wondered why my ears were burning!

    Here's a Canadian site for ply and other stuff, it's in Toronto but you can probably find one close to home: http://www.noahsboatbuilding.com/noahs

    I find outriggers just get in the way when paddling. An inflatable bag on the end of the paddle provide lots extra stability when not paddling and can be tucked away when not needed. Anything airtight will do but proper ones are sold as reboarding aids in paddling/camping stores. On my canoes I can lash the paddle to the thwart to free up my hands; you can probably add a strong loop to do the same, or just sit on it.
     
  8. Guest625101138

    Guest625101138 Previous Member

    I will go into promotion mode.

    Slenderness and length equate to speed. You are on the right track with a sit-on outrigger type hull if you want performance.

    I would always go for twin outriggers over a single because I prefer the security and less twitchy approach. It also gives the best performance at least in reasonably calm water because the outriggers can be set up to carry zero load most of the time. With a single outrigger you have to remain alert and be prepared to counter a roll away from the outrigger because you only rely on the tiny weight of the outrigger for righting moment away from the outrigger. You can pre-load the outrigger with initial roll but this adds a lot of extra drag.

    The beauty of this approach is you can make a very simple build. This link is a ply boat easily built:
    http://www.boatdesign.net/forums/attachments/boat-design/27961d1230635527-pedal-powered-boats-p3.jpg
    It pushes along at 5kts without much effort.

    The key to these hulls is to keep them light and quick to launch. Mine is a pure speed machine and I fold the outriggers up to make it easy to carry and transport on cartop:
    http://www.boatdesign.net/forums/at...5d1230111804-pedal-powered-boats-pc240005.jpg
    You can see one outrigger is folded above the seat for transport. Both fold up like this. A male of average fitness can punt this along at 6 to 7kts for long periods. The whole thing weighs 20kg so quite easy to throw on the shoulder if not a little awkward in a strong breeze.

    You may have noticed both boats are pedal powered. Leaves the hands mostly free to do what you want- maybe trolling or having a snack or brown ale. Very relaxed way to spend a day on the water. It borders on being illegal it is so much fun.

    Happy to explain more about these ideas if you have further interest.

    Rick W
     
  9. ShagRock
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    ShagRock Junior Member

    Ahoy Mates, I'm most thankful for your input!

    Rasorinc - I agree re starting with a proven design, especially if I can obtain one for decent price. Is the pipe you are referring to 'expanded closed-cell ploystyrene'?

    Ancient Kayaker - Thanks for info on marine ply. I'm close to BC so maybe prices are a little better - I'll keep you posted on that.

    Rick - I'm not as young as I once was - but who is;) That's a lovely kayak you have. Do you mind me asking its loa? Comparing yours to the other model you referenced, is yours easier to tack with the amas placed aft to CG like that? you noted getting up to 7knts max. That's fast! Is there a way of figuring speed if loa is slightly reduced and beam slightly increased -something simple, like a rule of thumb for kayaks?
     
  10. ancient kayaker
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    ancient kayaker aka Terry Haines

    Rick: gotta agree with Newfie, looks great.
    Newfie: thought you were out East with that moniker!

    I put an ama together that looked very like Rick's, not quite as narrow, part of an ill-conceived plan to enthrall the missus with the joys of canoing. I'm not sure whether it was her weight or the ama's drag or the fact that I was the only one paddling but neither of us were impressed!

    However, the canoe was probably the drag-contributing culprit; that narrow hull of Rick's should cut hull drag and the ama's provide the stability instead of the hull.

    If you have full-time ama's and a super-narrow hull then two is the way to go. However, if the hull can be paddled without ama's then one float may be better for Newfie's purpose as it leaves an unobstructed side to fish from.
     
  11. Guest625101138

    Guest625101138 Previous Member

    The Yelow boat is 7.2m - that is long. It overhangs the car by 1m either end. The white one is 5m.

    The 6 to 7kts is not max speed. That is a sustainable level for a moderately fit individual. I have nudged 10kts for a few seconds and I am on the mature side of 55yo. I averaged 11kph (6kts) over a 404km river course in December running over 5 days with two long days over 90km each. That includes current assist, a lot of headwind, dodging logs and substantial turning as the river meanders.

    There is very good software called Michlet/Godzilla that provides accurate hull drag data for different hull shapes. The basic input is design displacement and maximum length. The Godzilla component can optimise the shape to minimise the drag.

    Hull speed, as defined, is the typical sustainable speed of a long slender hull using human power. This is determined as:
    Speed in kts = 1.34 x (LWL ft)^0.5
    So 16ft slender boat displacing say 100kg could be punted along at say 5.5kts for a long period. Going up to 25ft gives 6.7kts. These are close to what is possible.

    Rick W
     
  12. ShagRock
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    ShagRock Junior Member

    Yes AK, it was the Rock but I am left for the bigger rocks called the Rockies, when the fish ran out!:) :) The amas I rode on in the Philippines last year were really efficient. Most were of bamboo with spider arms and kind of just skimmed the surface under motor or sail.

    Rick, thanks for the software tip and the details on your kayak. Regarding the speed factor for the 16' you referenced, what speed gain could be possible with the addition of a lateen sail? Is there a maximum limit for for this hull?

    Also, does the choice of multi chine as opposed to hard chine make much difference in a kayak of 16' LOA variety - for lake use as opposed to racing or whitewater?

    Newfie
     
  13. ancient kayaker
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    ancient kayaker aka Terry Haines

    A multi-chine hull is a closer approximation to a rounded hull than one with few planks and hard chines. Hard chines are more likely to cause turbulence and the hull would have more wetted area.

    The given truth is soft chines are faster than hard chines, but I haven't paddled boats that are close enough in design to establish that. My own experience is, my hard chine home-built boat can leave my (longer) soft chine boat in its wake unless both paddlers are working hard, so it's a minor effect.

    You're sailing question was directed at Rick, but my kayak sailing experience so far indicates that a small sail (12-15 sq ft) will easily push a kayak to sprint paddling speed in anything more than a gentle breeze on a reach or run. Upwind performance was so limited by the paddlers air resistance as to be non-existent an dis the only time I have felt the need for a larger sail.

    I have read varying reports about lateen sail efficiency so I am going to try one this year to see for myself.
     
  14. Guest625101138

    Guest625101138 Previous Member

    The speed figures I provided would be achieved with 120 to 150W. So the hull drag is around 50N on the 16' boat and around 35N on the 25' at their respective hull speed.

    50N (11lbf) is not very much when you are considering a sail. If you can react the rolling moment and use a keel to reduce leeway then kayaks make fast sailing boats.

    If you add a sail to pedal powered boat then you are adding weight and complexity. I certainly would not bother because I can already outperform most sailing dinghies and small cats. Once you start fiddling with sails you increase the set up time and the utility of the boat. Also my preferred days to be on the water are when it is very still. A sail is useless in these circumstances. I think sailing is its own end rather than a means to get to a fishing spot. I expect you will find you will become a sailor rather than a fisherman. Depends on what your objective is.

    There is very little difference in performance between a hard chine and a rounded chine hull. You typically find that for a particular design speed you can optimise to a rounded chine hull if you are not length constrained. Once you are length constrained, as you are with a 16' boat, the slight reduction in beam with the hard chine reducing wave drag effectively offsets the tiny reduction in wetted area that can bee achieved with a rounded chine.

    The 5m long white hull in the earlier photo is 300mm beam. If the boat had rounded chine you would have a beam more like 450mm for the same displacement.

    Rick W
     

  15. ShagRock
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    ShagRock Junior Member

    I have to admit I have only used paddles in the past and never used a Hobie peddle type. I didn't realize as noted by Rick that this could produce such speeds. Also, I can see Rick's point re the uselessness of a sail on a calm day. However, in my local you only need wait a bit for a weather change.
    I suppose one could have both, but it does complicate things.

    At this junction, I am looking at combining design features from a Philippine sailing canoe and a kayak like the 14' to 16' Arctic Tern. The hard chine type would be an easier build. As you note, there is not a big factorial difference between hard and soft chine in this size of boat (something which has been noted by the designer at Pygmy kayaks). However, I have read that the round hull will be better for tacking with a sail.

    On the subject of sail, I would say AC that if you go to a larger sail, you need to best consult a sail expert; because too large will cause the outrigger to bury and drag on the leeward side. I also read somewhere that a cat ketch rig may be just as effective and easier to handle than a lateen - something I need to study more myself.

    Before I forget, I want to follow up on Rasorinc's comments on plywood. Here, the options for 'marine ply' are limited in my locale: (1) Okoume but expensive, (2) 1/4" fir (Douglas not available) and it's seems a little heavy and bit rough, and (3) 4mm, 3 ply South American mahogany (Meranti not available either). With some stringers, I think the lighter weight mahogany is better choice, but I could certainly use some feedback on that.

    Newfie
     
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