tillering question/advice

[luke the drifter]

  hey folks,

      i have a four by eight sheet of plywood that i have drawn graph lines on to where the squares are one and half inches.  i have seen pictures of bowyers with their bows drawn at full tiller with an oval circle drawn to illustrate how close they are to perfect tiller(?).  i am wanting to get that circle drawn on my plywood graph to help me with tillering.  any ideas on how to achieve such a thing, easily?  do they much such a tool to draw that tillering oval to full scale?

[Hojo]

Luke---
Are going to draw it and erase it for each bow you build?  If not, I wouldn't bother trying to get anything drawn that is too exact, as the perfect circle or arc is going to change with different bow lengths, different limb profiles, etc.  

[luke the drifter]

i totally understand what you are saying.  which is why i plan to stick to one or two bow lengths and one or two draw weights/lengths just to keep it consistent.  the bow lengths will probably be 69 and 65 inches long and the draw lengths at 28 and 32 inches.  i plan to stay at one draw weight that being 50 lbs..   any ideas after these numbers?

[sailordad]

i just use the pic and windows paint to overlay the circle/oval
much easier than trying to draw in on a board

[Del the cat]

Another trick is to stand back from the bow when it is at full draw on the tiller rig, and hold up something round, say a saucer or plate between your eye and the bow so you can judge how the curve of the bow relates to the edge of the plate. If you want an ellipse then tilting the plate will give you and elipse.
I have my tiller on a brick wall and use chalk to trace around the limbs at various draw lengths, it allows you to see how it flexes over the draw.
Del