a question on canoe building

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

  1. peterchech
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    peterchech Senior Member

    my guess is so that you have some clearance below the keel to lash or use fasteners to fasten the keel to the frame at the lowest point. That's my guess.
     
  2. yoram
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    yoram Senior Member

  3. ancient kayaker
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    ancient kayaker aka Terry Haines

    Peterchech: fir is heavier and likely a bit stronger than cedar but both strength and stiffness comes from the cross-sectional dimensions. I suggest you cut the width down more than the depth, since that’s the direction most of the hits will come from.


    Yoram: take your time, you don’t want to be disappointed and there is no tearing rush.

    Cutting stringers with a skilsaw (handheld circular saw) is less accurate than a table saw. If you do it this way, first make sure the blade is exactly at right angles to the base plate and attach a ply foot under the steel baseplate; then drop the blade, while running, through it to make a slot that is snug with the blade. This will give a much cleaner cut. Also use a guide that is much, much longer than the one supplied with the saw. Make it at least twice as long as the base plate and arrange for some to stick out in front of, and behind the saw: that will guide the saw at the beginning and end of the cut. This is shown in my blog, the link is on post #20.

    I do not recommend cutting stringers with a jigsaw. Even with a guide a jigsaw blade will wander off the cutting path because it is so flexible. When cutting a curve with a jigsaw move slowly to put minimum force on the blade; if it bends the edge will have a bevel.

    Take a look at the pictures of the Sea Bee sections and note the notches for the stringers. Compare them with the notches for the multi-chine Nikumi. Note that the ones for the 3 chines between the gunnel and keel are smaller; this is normal practice to reduce weight. Also note the curved edges of the sections between stringer notches; this prevents the fabric from touching the section - sometimes these edges are straight but recessed back from the outer edge of the stringer for the same reason.


    I think the reason for that is for clarity on the drawing: the HAB has to measured from a horizontal line and the draftsman wants clearly distinguished from other lines on the drawing such as the keel.
     
  4. peterchech
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    peterchech Senior Member

    I mean, his measurements are in fractions of feet (why not feet and inches, or just metric?) but his coaming measurements are in millimeters.

    The guy has a wonderful, free website full of free plans that lots of people have built and tested, and he even seems to update designs based on feedback. I can see why he may be too busy to make every plan perfect...
     
  5. peterchech
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    peterchech Senior Member

    Good advice ancient kayaker thanks
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    Here's a pic of the skilsaw ply foot and guide. Please be careful when using power tools!
     

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  7. yoram
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    yoram Senior Member

    very good tips, thanks. the skillsaw with the plywood base, very cool idea!
    i have seen somewhere a table saw made from a skillsaw. the saw was up side down, connected to a piece of plywood 60x60 that was a table when only the blade was sticking out through the plywood board. like a table with 4 legs with a blade sticking out.

    anyone recognize the type wood i posted ?
     
  8. yoram
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    yoram Senior Member

    again, good and creative thinking but still why it is zero in some places and 0.12 in other?
    maybe it is just not well organized like peterchech wrote and different people are writing in the web site.

    i was sure that it is good for the skin to touch the sections as it gets more support. so should the skin be supported only by the stringers and should i curve all the places in the section where it touches the skin?
     
  9. peterchech
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    peterchech Senior Member

    IMO the skin should only contact the stringers.

    Here's a pic of my chuckanut 15 tandem kayak (that's my girlfriend and dog having fun in it by the beach-very stable)

    [​IMG]
     
  10. ancient kayaker
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    ancient kayaker aka Terry Haines

    The skin is normally only supported by the stringers - including the gunnels - and keel, plus the stems. The edges created by these all run fore-and-aft.

    The theory is, any edges across the flow of water past the hull can create turbulence, at least below the waterline.

    Above the waterline some people consider it is ugly - the boating term in English is "unfair" . . .

    There is another reason; if the skin gets hit by a pointed object it can flex more easily if there are no corners.
     
  11. yoram
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    yoram Senior Member

    what to do with the keel in the Seabee? it is bent almost 5 cm (4.66 cm) from the base line and i doubt if i could do that with the keel. i want to use 2 cm thick x 5 cm wide fir. i doubt that any other wood would bend 4.66 cm.

    how is it done?
     
  12. peterchech
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    peterchech Senior Member

    4.66 cm bend over 13 ft? What is the problem?
     
  13. yoram
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    yoram Senior Member

    i have tried it today and it doesn't move much. i tried to bend it when the narrow part is vertical, the way i am planning to have the keel. (2 cm horizontal and 5 cm vertical).
     
  14. peterchech
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    peterchech Senior Member

    The keel should be closer to 2cmx2cm anyway I think.

    I have never heard of wood that won't bend 4.66 cm over 13 ft maybe you should post a pic I'd like to see what you mean...
     

  15. yoram
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    yoram Senior Member

    i have taken 3 photos. i hope it is clear enough. check it out and if you can tell me what am i doing wrong because it doesn't bend. (when i try to bend it to make the arch longitudinal on the 2 cm facet
    i do not want to cut it to be 2cm x 2cm because it might break easily.
     

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