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Re: [Cedar Strip Canoes] Gunwale material?

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  • James D. Marco
    Cauls are the strips of wood you put between the clamp and the pieces you are clamping. They are often used to reduce marring on the surface caused by clamps,
    Message 1 of 10 , Mar 31, 2010
      Cauls are the strips of wood you put between the clamp and the pieces
      you are clamping. They are often used to reduce marring on the surface
      caused by clamps, but this is minor. Generally they distribute the
      clamping pressure from the clamp to a wider area. This will reduce the
      tendency for narrow strips of two dissimilar woods, like oak and cedar,
      to "bubble" between clamps. The cedar compresses more where the
      clamp is, forcing the oak away as this pressure is reduced, just beyond
      the clamp. A caul prevents this by eliminating the "point" compression
      and distributing it for the length of the caul.
      In some cases they are used to focus on an area to be clamped.
      Sometimes they are used to clamp odd shapes. Some people will go so
      far as to use curved or milled cauls, clamping in the center, so that there
      is an even pressure along the caul from the center to the ends. There was
      an article about these in Fine Woodworking 6 or 7 years ago, I think...
      Reversing the curve and using two clamps lets you apply pressure along a
      large panel.
      Hundreds of uses for a simple wooden block.
      My thoughts only . . .
      jdm
      At 02:11 PM 3/31/2010, you wrote:

      >cauls ? what are cauls,
      >Graeme.
      >--- In cedarstripcanoes@yahoogroups.com, "James D. Marco" <jdm27@...> wrote:
      >>
      >> Corky,
      >> On all my boats, 'cept the last one, I have changed the gunnels at least
      >> once. They get banged up pretty good with docks, flipping them over, paddling
      >> (the occasional misstroke,) footwork, and, car topping. Oak, ash and mahogany
      >> have been my usual choices. With oak being the most durable, mahogany the
      >> most rot resistant but less durable, and ash light and medium durable.
      >> Mixed species would allow for lightness and good durability; a good
      >> thought. Hmm...
      >> I am planning on 3/8" cedar for the outwale for the Nimble Weed. 3/8x3/4
      >> with a 3/8" cove routed into the bottom to help turn waves. I like the idea of mixing
      >> species on the outwale, minimally. I have some 5/32"x7/8" oak strips left over
      >> from the last boat. I think I will borrow that idea and put this over the cedar as a
      >> wear strip, before milling. The inwale will still be cedar. If I use floured(sanding
      >> dust) epoxy, this should resist moisture, OK. Though, laminating a long thin strip
      >> is always painful, lots of bubbles. I'll have to remember to use plenty of cauls and
      >> plane it down a hair to remove the tendency to bubble. Plenty of cauls will be in
      >> order. Is this about what you were planning? Sounds light enough and still have
      >> the utility that is needed. Even if it only saves a few ounces, a UL boat wants
      >> every little bit.
      >> Thanks, Corky!
      >> jdm
      >> At 08:15 AM 3/31/2010, you wrote:
      >> >I was intrigued several weeks ago by a comment one of our group made about
      >> >gunwale material. I thought he'd said that you can sandwich cedar and ash
      >> >to form the outer wale, and can use cedar entirely for the inner one.
      >> >
      >> >
      >> >
      >> >Did I read that right?
      >> >
      >> >
      >> >
      >> >I can see how that could work for the outer wale, you need to have hardwood
      >> >to the outside of that piece because I frequently scrape the paddle against
      >> >it. It never occurred to me to use cedar for the inner wale though. Is it
      >> >strong enough to provide the stiffness the canoe hull requires?
      >> >
      >> >
      >> >
      >> >Is the weight saved by sandwiching cedar with ash for the outer wale worth
      >> >the weight savings?
      >> >
      >> >
      >> >
      >> >Thanks, Corky Scott
      >> >
      >> >
      >> >
      >> >[Non-text portions of this message have been removed]
      >> >
      >> >
      >> >
      >> >------------------------------------
      >> >
      >> >Yahoo! Groups Links
      >> >
      >> >
      >> >
      >> James Marco, Computer Operations Manager & Desktop Support
      >> Chemical and Biomolecular Engineering, and, Biomedical Engineering Departments
      >> B59 Olin Hall, Cornell University
      >> Ithaca, NY 14853 Office Phone: 607-255-7312
      >>
      >>
      >> [Non-text portions of this message have been removed]
      >>
      >
      >
      >
      >
      >------------------------------------
      >
      >Yahoo! Groups Links
      >
      >
      >
      James Marco, Computer Operations Manager & Desktop Support
      Chemical and Biomolecular Engineering, and, Biomedical Engineering Departments
      B59 Olin Hall, Cornell University
      Ithaca, NY 14853 Office Phone: 607-255-7312


      [Non-text portions of this message have been removed]
    • Charles & Dana Scott
      Thanks for the input James. Because you change your gunwales, did you install them with bolts, or did you bond them with epoxy, and therefore have to strip
      Message 2 of 10 , Apr 1, 2010
        Thanks for the input James. Because you change your gunwales, did you
        install them with bolts, or did you bond them with epoxy, and therefore have
        to strip them off with a sharp chisel or hand plane? Or perhaps a
        combination of power plane and hand plane?



        Thanks, Corky Scott











        _____

        From: cedarstripcanoes@yahoogroups.com
        [mailto:cedarstripcanoes@yahoogroups.com] On Behalf Of James D. Marco
        Sent: Wednesday, March 31, 2010 1:29 PM
        To: cedarstripcanoes@yahoogroups.com
        Subject: Re: [Cedar Strip Canoes] Gunwale material?





        Corky,
        On all my boats, 'cept the last one, I have changed the gunnels at least
        once. They get banged up pretty good with docks, flipping them over,
        paddling
        (the occasional misstroke,) footwork, and, car topping. Oak, ash and
        mahogany
        have been my usual choices. With oak being the most durable, mahogany the
        most rot resistant but less durable, and ash light and medium durable.
        Mixed species would allow for lightness and good durability; a good
        thought. Hmm...
        I am planning on 3/8" cedar for the outwale for the Nimble Weed. 3/8x3/4
        with a 3/8" cove routed into the bottom to help turn waves. I like the idea
        of mixing
        species on the outwale, minimally. I have some 5/32"x7/8" oak strips left
        over
        from the last boat. I think I will borrow that idea and put this over the
        cedar as a
        wear strip, before milling. The inwale will still be cedar. If I use
        floured(sanding
        dust) epoxy, this should resist moisture, OK. Though, laminating a long thin
        strip
        is always painful, lots of bubbles. I'll have to remember to use plenty of
        cauls and
        plane it down a hair to remove the tendency to bubble. Plenty of cauls will
        be in
        order. Is this about what you were planning? Sounds light enough and still
        have
        the utility that is needed. Even if it only saves a few ounces, a UL boat
        wants
        every little bit.





        [Non-text portions of this message have been removed]
      • Charles & Dana Scott
        When I was building my homebuilt airplane, I did a lot of research on propellers, because I discovered that a number of them were using an airfoil that was
        Message 3 of 10 , Apr 1, 2010
          When I was building my homebuilt airplane, I did a lot of research on
          propellers, because I discovered that a number of them were using an airfoil
          that was designed back in the '30's. It turned out, prop design is
          extraordinarily complicated with the airfoil needing to be different from
          one place to another from the hub out to the tip. Or not, depending on how
          complicated you wanted to make things. Plus, the angle of attack of the
          airfoil also changed from the hub to the tip. So hand carving a prop
          requires extreme care and lots of jigs to make sure that you carve the two
          blanks the same.



          One of the interesting things about wooden props is that they "absorb"
          vibration as opposed to metal props which can and do "amplify" vibration.
          So wooden props could be used on lots of low performance type airplanes, but
          metal props were normally used on the higher speed airplanes because the
          props needed to have thinner airfoils.



          But getting to the subject of wood used in prop fabrication, almost all the
          props I researched were made using sandwiches of hardwoods because the
          propellers lived in a harsh world where flying into rain could very well
          degrade the prop to the point of danger. If you've ever driven a motorcycle
          in the rain without a full face shield, you can appreciate how hard a drop
          of water can be.



          So I'm not saying that no one ever made a prop out of Sitka Spruce, or some
          other softwood, but if they did they probably would have needed to protect
          the leading edge somehow, like with a brass cuff, or simply not fly in
          inclement weather or clouds.



          One of the other factors regarding wooden props is that the compression
          plate, which attaches the prop to the prop flange of the engine and is on
          the outside of the propeller, had to be retorqued periodically, or the prop
          could get itself loose, with understandably disastrous consequences. Each
          firing impulse from the engine sends a separate jolt to the prop, which is
          what causes vibration in metal props. Large cylindered aircraft engines
          with just four cylinders produce considerable spikes of torque to the prop.
          Just another factor in prop design.



          Just to keep things relevant, Sitka Spruce was the dominant building
          material for airplanes since the first airplanes were designed, up to the
          end of the '30's. It's light weight and flexibility and strength is what
          also made it very popular for boat building.



          Corky Scott



          _____

          From: cedarstripcanoes@yahoogroups.com
          [mailto:cedarstripcanoes@yahoogroups.com] On Behalf Of badgerberling
          Sent: Wednesday, March 31, 2010 12:20 PM
          To: cedarstripcanoes@yahoogroups.com
          Subject: [Cedar Strip Canoes] Re: Gunwale material?





          Here in Madison Wisconsin we can get adequate lengths of Sitka Spruce for
          gunwales. Our experience is that it is light, flexible and strong enough to
          hang seats, etc. We epoxy glue in and out wales. My preference is 5/8
          inwales and 3/8 outwales with the scuppers 5/16 cut out of the inwale
          material every six or eight inches.

          The easiest thing for me (being absent a real wood shop) to do here is have
          the lumberyard plane the 1 x 6 to the desired thickness and rip it to the
          desired dimensions. It beats handling a nearly 20 foot board.

          A 1 X 6 will yield enough 3/8 and 5/8 strips for two canoes with a strip or
          two leftover.

          The softer Sitka will collect a few nicks from abrasion but really after
          twelve years on my first boat it is insignificant. Small washers for
          tightening seat bolts will increase fastener strength without gouging into
          the soft Sitka and are not noticeable.

          I do find the sandwich idea interesting and enjoy reading these posts.

          I was told they use the Sikta here to make iceboats and airplane propellers.

          Badgerberling





          [Non-text portions of this message have been removed]
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