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Lofting of Sairy Gamp lines from Orvo Markkula drawings

Discussion in 'Traditional All-Wood Construction' started by SteveReynolds, Dec 12, 2017.

  1. SteveReynolds

    SteveReynolds Curious about Wooden Canoes

    Has anyone lofted the lines drawn by Mr Markkula as published in the Atwood Manley book? If so, have they developed a corrected table of offsets?
     
  2. OP
    OP
    SteveReynolds

    SteveReynolds Curious about Wooden Canoes

    I am going to loft these, and will post my results.
     
  3. OP
    OP
    SteveReynolds

    SteveReynolds Curious about Wooden Canoes

    I've completed a first stab at a body plan derived from Markkula's "Offsets for 7-Station Form for 9'x26" Rushton Canoe 'Sairy Gamp'" as published in the Atwood Manley book. Some immediate problems with his work become apparent. First, a building form would normally be sized to the inside of the planking, but his dimensions appear to be outside planking. I say this because the maximum beam in his table is 13 3/16" for the half-width at station 4, which gives a total beam of 26 3/8". Secondly, some of his numbers are clearly wrong without drawing anything - for example, the sheer strake end of station #2 flares gently until the last 7/8", after which it abruptly turns inward. Thirdly, his dimensions for the widths at gunwale height appear to be to the outside of the gunwale except for his value for station 2 mentioned above which is just not usable - you cannot fair the lines of the station into his widths at gunwale height without assuming a gunwale. Finally, and maybe most disconcertingly, I can't believe he has the gunwale heights correct at least for stations 3 & 4. Using his numbers, the overall outside depth at the center of the boat is 7 1/16", or about 6 7/8" inside depth. I don't think that would float, at least for very long. Further, trying to draw in a fair sheer line in the body plan is not possible given his gunwale heights.

    What I have done is drawn the stations as faired curves as a starting point for lofting, assumed a gunwale measuring about 1/2" wide by 5/8" tall at station 4, and brought the heights of stations 3 and 4 up so they would give that fair sheer line. In my drawing, attached, Markkula's dimensions appear in red. I may try to scale his profile view to understand better what the depth should be.
     

    Attached Files:

  4. OP
    OP
    SteveReynolds

    SteveReynolds Curious about Wooden Canoes

    A measurement scaled from Markkula's profile drawing gives an outside depth at station 4 of 7-1/16" - same as his table of heights. A Vaux Jr, by comparison, is 10-3/16" deep - being 2 1/2' longer but same beam as Sairy Gamp.
     
  5. Dan Miller

    Dan Miller cranky canoeist Staff Member

    You have reaffirmed what many of us already know - the drawings in the back of Manley's book are quite bad.
     
  6. MGC

    MGC Scrapmaker

    I could never understand why Atwood relied upon Markkula to provide the drawings for his book.... his daughter had the drafting qualifications to provide equal or better details. While he was working on the book I assumed that she would be providing the drawings for him. Unfortunately it's a topic we never discussed so it will remain a mystery.
     
  7. Dave Osborn

    Dave Osborn LIFE MEMBER

    I’ve seen the Sairy Gamp in the Adirondack Museum. There was a sign there that said, “Do Not Touch”.
    Well a little devil on my shoulder said,”go ahead”.....
    I reached over the rope and long armed a feel of the gunwale on the little craft.
    I’ve carried the guilt ever since.
    I feel better now that I’ve come clean about it.
     
    Dan Lindberg and Andy Hutyera like this.
  8. OP
    OP
    SteveReynolds

    SteveReynolds Curious about Wooden Canoes

    I have decided not to loft these lines since there is no way they could be claimed to represent the Sairy Gamp because of the unreliability of the Markkula measurements. Also, a boat that is only 6-3/4" deep is not useful to me. So - I may take Markkula's lines and modify them for a deeper version, and publish the results in my blog. But they won't be a 'Sairy Gamp'.
     

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