Bow length/ draw length

[DC]

Anyone ever figured out a way of telling how much changing the overall length of a bow changes the draw length? I did a quick drawing and came up with 2" off each end changes the DL by 1 1/2" on a 60" bow. Does that sound reasonable? I hate to say it but I think it would change with the string angle but I'm not sure.

[IrishJay]

Don I think overall design plays a huge role in it (r/d, recurve, stiff handle, bendy handle etc...) I think each design probably scales differently i.e. a 4" change on a rigid handle flip tip probably has a different effect on draw length than a 4" change on a straight limbed bendy handle.

[burtonridr]

I've read its

Bow length = (drawlength x 2)+10

Is that what you mean?

Shortening the bow definitely changes full draw string angle and by extension the feeling of the bow stacking due to the loss of leverage as the string angle increases. Which (in part) is why shorter bows sometimes have extreme tip flipping going on.

[PatM]

A simple scaled drawing will show the ratio.

[DC]

I've read its

Bow length = (drawlength x 2)+10

Is that what you mean?

Shortening the bow definitely changes full draw string angle and by extension the feeling of the bow stacking due to the loss of leverage as the string angle increases. Which (in part) is why shorter bows sometimes have extreme tip flipping going on.

Not really. That would almost work. What I'm looking for is how much longer the draw length would be if you lengthened the bow, or vice versa.

A simple scaled drawing will show the ratio.

Yeah, that's what I did. I keep looking for "rules of thumb". There doesn't seem to be to many in bowyery.

[bradsmith2010]

ok Im going by memory,,, so ,, but I think in Volume 1  of THE TRADIONAL BOWERS BIBLE,,
rule of thumb,, if you increase the draw 1 inche,, increas the bow length 2 inches,,,
its in there I will look for it and post later,,but I think thats right,,
it says,,,,,,based upon a starting point of 66 to 67 inches for a 28 inch draw length,, the ideal bow length rises and falls with the draw length,, and an adjustment of two inches of bow length for every inch of arrow length will be very close to correct.  that is on page 69,,

[DC]

Thanks Brad.

[Hawkdancer]

Dr Al Herrin has a chart in his book on Cherokee Bows and arrows.
Hawkdancer

[Woodely]

........."changing the overall length of a bow changes the draw length?"  I always thought that if I build a 62" bow and still have a draw length of 28"  regardless of bow length,  unless its a real shorty like 54".  pulling that would stress it ,  thats all I know.

If I related all this math stuff to bow building I may as well become an engineer for Ford Motor Comp.

[DC]

Maybe I should have said,"Assuming the same bend." although it probably wouldn't help. I seem to have a problem with the English language. I have a heck of a time being understood a good part of the time. My mother was an English teacher too.

[Woodely]

Its appears that your Math skills are up to par with some Brainiacs, I mean that in a good way.   I just do everything in the seat of my pants sort of way.   I hate reading directions,  I just build on a whim, any plans are just maybe chicken scratch on a note pad.

[TimBo]

Hey DC,

Are you thinking of something like this?  Usually we pike a bow to pick up more draw weight at the same draw length, but the bow is more stressed.  I think you are asking if there is a way to calculate the new draw length if we said, "I want a 56" 50# bow and am going to make it out of a 60" 50# bow; I wonder what the draw length will be?"  Of course, I may be way off, which would not be unusual...

[TimBo]

Please refrain from any tiller critiques!

[bradsmith2010]

Left limb little stiff,,,

[DC]

Yup, that's it