a question on canoe building

Discussion in 'Boat Design' started by yoram, May 27, 2011.

  1. yoram
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    yoram Senior Member

    guys, thank you all for your comments.
    i knew boats were built before epoxy time but i could not understand how they kept it water tight. i red they put thin cotton ropes and tar in the seams but i thought it is not the way i want to go.

    it must be very difficult to keep it water tight and still keep the canoe light without epoxy, isn't it?
     
  2. yoram
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    yoram Senior Member

    ancient kayaker, you wrote many important points from your experience and it raised a question in my mind about the secondary stability. is there a simple way to calculate the secondary stability in case i increase the beam(on the water line) in a flat bottom canoe?

    and do you really sleep on the canoe while it is sailing?.....amazing
     
  3. rwatson
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    rwatson Senior Member

    In those days they didnt have plywood - it was all solid wood planking.

    One of the previous posts reveals the reason for using epoxy, the fastenings (nails, screws etc) into the end grain of plywood are not reliable, so you have to use chine logs to hold the fastenings.

    As the intersection of the two plywood sides alone creates a structure that doesnt require the strength of chine logs, the timber is just extra weight, and a potential source of moisture entrapment (from water and condensation) due to the top angle of the logs (unless you go to the the trouble of shaping the top edges).

    So, to get maximum waterproofness with sufficient strength, epoxy is the outstanding choice. It has the advantage of creating a uniform bond at all locations of the ply edges (unlike stress points created by screws or nails), promotes water protection, and promotes water and condensation runoff to the bilges, while being inherantly waterproof.

    And dont forget, no complex placing and shaping of the chine logs - that has to be a big plus.

    By the time you use expensive sealers and glues, nails and screws and the extra timber in chine logs - it makes using the epoxy/glass method seem a better choice, to my way of thinking.
     
  4. peterchech
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    peterchech Senior Member

    unless you wanna build laguna sink-o style...
     
  5. ancient kayaker
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    ancient kayaker aka Terry Haines

    There is no really simple way to calculate primary or secondary stability but the easiest way is to download a free hull design program like FreeShip and learn to use it. It has a utility called cross curves which display the righting moment as the hull is heeled.

    I don't sleep while sailing! The canoe I was referring to for that comment was my tiny "lost-pond" style paddling canoe. These days I am not able to undertake long trips.

    This is quite true; the chine logs do the same job as glass tape and an epoxy fillet by reinforcing the plank-to-plank joint, or seam. The use of a glued chine log eliminates the stitching process used to assemble the planks ready for seaming, with its dozens of holes and wire stitches and fiddly adjustments to get the plank edges to lay right. Getting a neat epoxy fillet takes some practice and may require lots of sanding - I speak from experience - whereas the log looks neat and tidy from the get-go.

    For a small solo canoe I use 8 x 17 mm softwood. For a small sailboat I used the about 17 mm square but I had trouble bending the sheer plank with the log attached and had to cut slots halfway through the log which added about an hour to build time. For the canoe the 4 chine logs weighed less than a kilo and replaced perhaps half that so the weight penalty is not great, however, if the chine logs were part of a frame to which the ply planks were added, they would have to be much thicker to resist assembly forces during planking.

    I use fairly thin ply for my boats, 3 mm in the case of the canoe, and the planks are floppy and delicate; with the chine logs (I also glue the inwales) added (while the planks are flat) they become much easier to handle.

    This would apply to chine logs that are built into a frame, with ply attached to that, not to simple chine logs glued directly to the planks. I reiterate it is a very simple and easy method for a small boat and is shown in my blog http://theancientkayaker.weebly.com/
     
  6. yoram
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    yoram Senior Member

    hi guys
    i took the canoe for a long ride today with the amas and without. (i attach photos of the canoe) the conclusions are that it goes much much faster without the amas but the stability is almost infinite time higher with the amas.

    without the amas, i tried sitting on the floor and on a compartment i built which is about 18 cm higher above the floor in the center of the canoe. the sea was calm, winds of 3 Kn. it is also easy to handle when sitting on the compartment when the sea is calm and much easier when i sat on the floor. it felt relatively safe.

    i tried to check it with the waves that a 40m ferry was creating and there was no way it would tip over with the amas. it felt very safe and my feeling it could handle waves 3 times bigger easily.

    i paddled with a friend and by my self so it can hold 2 people (about 80 Kg each one)

    you were right. i should build better amas and it will improve the speed and will be nicer looking.

    next thing is to put a mast and a sail. any ideas for a quick and easy and simple way to do it beside buying a ready one?
     

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  7. ancient kayaker
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    ancient kayaker aka Terry Haines

    It is best if the mast is light and easy to handle, as it is inadvisable to stand up in such a small boat, and handling heavy gear from the sitting position can be a challenge. Some years ago I picked up a telescopic handle cheap, it was intended for cleaning a swimming pool but was missing some hardware and it was fine for a small sail. I have also made nice hollow wooden masts, not as difficult as I expected, I show the method in my blog.

    I have made several sails from small tarps. Without a leeboard you will not be able to sail into the wind so sail efficiency is not important, and a simple square cut of lug sail will work fine.

    A word of warning: the power of the wind is surprising: for example Beaufort force 5 - see http://en.wikipedia.org/wiki/Beaufort_scale - is described as a fresh breeze, about 35 kph with moderate waves with many white foam crests, will generate a pressure of about 72 N/square meter or 1.5 lb/sq ft. That against a small sail made from the smallest tarpaulin size which is 4 x 6 feet or about 2.25 sq.m area will produce about 162 N at a height of about 1.5 m for a heeling moment of over 240 Nm or a down force on an ama 1 m from the main hull of 240N or 24 kg. That is considerably more than your current ama will support; a skilled sailor might handle that but with your existing ama size you would be advised not to venture out in any breeze capable of more than rustling tree leaves.

    You should also test your mast with a weight to ensure it can handle the force before venturing out. You can add standing rigging from the mast top to the hull to support the mast, that will roughly triple the force the mast can support, but all those lines are messy and easy to get tangled, as I found when I tried it.

    Later you can get more ambitious and adventurous . . . most of us do.
     
  8. yoram
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    yoram Senior Member

    ancient kayaker, thanks for your comments. i think i will make the mast and boom from wood that we have in the school, laying around, waiting to be used. so this will be cheap...
    the rest, i will try to go to second hand shops or garage sales that we have here a lot in the summer time. it is a challenge to spend as little as possible on it.

    i have checked your blog. very nice and inspiring. did you build the one **** canoe or it is still on paper?
     
  9. peterchech
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    peterchech Senior Member

  10. ancient kayaker
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    ancient kayaker aka Terry Haines

    It's built, just been waiting for the finishing touches. I have another in the works so I will finish them together.
     
  11. yoram
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    yoram Senior Member

    ancient kayaker do you have photos of the one sheet (not **** like i wrote last time... sorry) kayak?

    peterchech
    very interesting links. did not have a lot of time to read but looks very good. thanks for the tip.

    i have been canoeing a lot today without the amas. i noticed that sometimes the canoe has a tendency not to go in a strait line but pulls to the left or to the right. most of the time it is fine. is it the flat bottom that creates it?
     
  12. troy2000
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    troy2000 Senior Member

    When you lean the boat, the underwater shape changes drastically because of the hard chine. If the curve of the bottom doesn't somewhat match the curve of the side that's in the water, you suddenly have a lopsided vee-bottom that doesn't want to go straight.

    My earlier flat bottomed canoes would turn right if I leaned left, and would turn left if I leaned right. I seem to have gotten the shape right on my last one; it goes pretty much in a straight line no matter how hard I lean it. Maybe it's just wide enough to counter the effect...
     
  13. ancient kayaker
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    ancient kayaker aka Terry Haines

    No problem: I was chuckling over that typo for hours.

    I will add an image of the one-sheeter to my blog when it gets finished: presently it is stored out of the way and is a bit inaccessible - the poor thing has been waiting for 2 years. However it is very similar to the boat on the first page - Dora - just a foot or so shorter; the length reduction was done aft of midships so she is not symmetric like Dora.

    Leaning to turn is a valid technique for both canoe and kayak paddlers, some boats will do it and some don't - it isn't considered a fault and is very handy if you have a boat that tends to turn off or into the wind as it's a lot less tiring to compensate by leaning than by using the paddle.

    Another trait is when the boat turns when you stop paddling; a boat with this fault will typically turn in either direction, usually in the opposite direction of the last stroke. It is caused by the center of gravity being aft of the center of lateral area and aggravated by a deep forefoot; once started it gets worse and can end up more than 45 deg off course in some cases. It commonly happens to a kayak with a rudder when it is raised out of the water and tends to afflict short kayaks with maximum beam aft of midships, so I expect to encounter it on the one-sheeter. The cure is to add a rudder or skeg.
     
  14. troy2000
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    troy2000 Senior Member

    You're right, Terry. It isn't necessarily a fault that a boat turns when leaned, if you like to take advantage of that for steering.

    On the other hand, it's a !@#$%^ nuisance when you give your paddle a couple of hard strokes to keep you moving, stretch out and over to reach a beer or your tackle box, and look back up to see the shore bearing down on you...

    My Blue Rose spins almost on a dime if I want her to. But she doesn't wander around based on which way I'm tilting her. Since I built her to fish out of, rather than as a trekking canoe, that's a good thing. :)

    Hmmm... I'm in trouble. I see I've started referring to Blue Rose as my boat, instead of as my son's boat--even though she was his when we built her. Whether I can get away with that depends largely on where he gets stationed after he's out of EOD school, I guess.
     

  15. yoram
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    yoram Senior Member

    ancient kayaker , i am glad i made you chuckle... well English is not my mother tongue so sometimes that is what happens.

    i am still on the one sheet canoe. it seems like something i would like to build. i have some questions about it:
    how much does it weight?
    what is it's displacement?
    thickness of the sheet?
    was it built and tested before?
    what system do you use to build it? (btw, what is The Bass-Ackwards Design Method?)
    is there a way to get the plans?

    thanks

    yoram
     
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