I have several trick, but none of them are "primitive." So, if that bothers you, skip my post.
My first trick, and I'm supprised more people dont talk about it, is using your tiller tree and, with the bow partially drawn, mark a line under one limb with a marker. Then reverse the bow in the tree, draw to same position, and mark under that limb with a different color marker. Note the difference.
I usally design the bow with a Excel program called selfarc 10. I then draw the bow full size to the measurements the program tell me with Autocad here at work and plot it out.
Alast trick I've used on my last bow with great success, is a tool I make with dial indicator in it. I run it along the back of the limb and note the curve radius. This trick can give you a perfect curve of any radii you want, and you can match both limbs. The tiller can be perfectly circular or any other. Really works.
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