shortening a bow to increase weight

[sadiejane]

well, i did a search and found a few bits of info here and there but not enough to satisfy my question.
so is there any "rule" regarding how much you take off equals  pounds added.  of course, type of wood, weight(poundage) to start with, width, etc etc would effect this. but maybe there is some loose idea. have an osage bow ready to shoot-actually have put a few arrows thru it, but need to bring the weight up 5-10#. left it some longer for just this purpose; to cut shorter for added weight if necessary. it is currently 67" ntn and pulls 48# @ 28".
also was wondering about heat treating the belly. have found numerous references regarding heat treating white woods. what about osage?
appreciate ya'lls input.
thanks

[Del the cat]

There is some guidance in one of the TBBs.
My personal view is that unless the bow was very overdesigned in the first place (or you have a shorter draw than the designed one) you may well end up chasing your tail. E.G The shortened bow has a higher draw weight, but then takes more set.
I've found heat treating is the only way I've ever managed to recover significant draw weight.
The real advice is don't trust formulae, bows aren't classic simple mechanical devices, they are highly non linear.
If you want to play with a bow take off half an inch at a time, after all, you can't put it back on (Ok that's not strictly true, but you get my drift).
Del
Only other advice is don't listen to cats .

[PEARL DRUMS]

I would say snip an 1 1/2" off each end. If its only gettting pulled 28" and its a 67" ntn osage bow you have plenty of wiggle room Sadie.

[crooketarrow]

  I've did this on  few bows. It comes out to around 3 to 5 ponds and inch. Depending on lenth,desigh ,wood type. But it'll come ouut somewhere close. You'll likely have to touch up the tiller. But I've had 2 that I did'nt have to.

[M-P]

Hi Sadiejane,   I'll put in a slightly different opinion.   Yes piking (Bowyer's term for shortening a bow) is a time honored and effective way of increasing draw weight.  As noted taking an inch off each end gives ~ 5 # increase.   Makers of long bows routinely did this, but they always made the bow a little longer than necessary to begin with.   There are a lot of short osage bows being posted, so you may have the room to pike your bow too.  However, I strongly suggest you heat treat the belly first.  Heat treating will also raise the draw weight by 5-10# and since you should always heat with a little reflex, you will probably increase performance even more.  Osage takes to heating very well.    Of course you could pike the bow and then heat treat the belly to reduce any increased set, and have a real rocket launcher.
PS "Fix it 'til it breaks!"
Ron

[sadiejane]

the bow in question has about 1 1/2" natural reflex. it started with about 3" and lost about half during final tillering and shooting. just a bit more info that may or may not make any difference. have done no heating nor reflexing/straightening to this bow...yet. still thinking thinking thinking....about how to proceed. taking 'er with to mojam this coming week. let some folks i know shoot 'er, measure weight again and go from there.
so taking 1" off each limb would leave the bow at 65" ntn. not really a "short" bow....still plenty long enough for a 28" draw aye?

[Pat B]

If you are going to MoJam bring it there and let someone walk you through it. You will learn more that way too. 

[sadiejane]

If you are going to MoJam bring it there and let someone walk you through it. You will learn more that way too.

always look forward to hearing folks responses and expertise here. but i will indeed take to mojam...hoping to learn lots over these coming four days.
face to face and hands on sure helps things sink in....
thanks!