Primitive Archer
Main Discussion Area => Bows => Topic started by: stuckinthemud on April 12, 2023, 07:22:08 am
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Right, so, this is my current project, the dimensions are taken from a medieval example in the Kristianstad museum, Sweden. The taper is 1mm per 1 inch of thickness, except for the central 8" which fade to a stiff centre of 4". Front taper is constant from centre to nocks. The original is 27mm thick by 37mm wide at centre, I am a little under this at 25mm and so I am about 2mm too thin along the whole length. The original is yew, probably compression wood - it was drawn in 1945 as straight, but now shows a very slight deflex (set?) - the humidity of storing conditions changing would explain the difference in profile as compression wood moves with humidity changes. I figure I am about 10% below the original's draw weight. Does that seem fair?
Also, the centre 1/3 of my bow has a tiny amount of reflex, the photo shows the centre as straight where the reflex is affecting the draw profile. I figure I need to soften the inner 1/3 but would welcome any opinions on this. For what its worth, the draw length will be 10.5 inches measured from the belly - brace height is 4"
the original
(https://stuckinthemudsite.files.wordpress.com/2022/12/img_1503-1.jpeg)
Getting near to brace height
(https://stuckinthemudsite.files.wordpress.com/2023/04/img_0517.jpg)
Side profle (unstrung)
(https://stuckinthemudsite.files.wordpress.com/2023/04/img_0522.jpg)
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Taking stiffness as proportional to the cube of the thickness...
25mm cubed vs 27mm cubed would give about 80% of the stiffness.
Dunno how valid this is, but it's probably pretty good.
Del