Author Topic: Osage flatbow questions  (Read 928 times)

Offline Ol'school

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Osage flatbow questions
« on: February 20, 2009, 09:13:00 AM »
I'm working on another selfbow, the stave had 3 inches of natural reflex and some propeller.
A little work with the heat gun and the propeller sraightened out nicely.
The bow is 58 inches ete, 1.5" at fades with straight taper to .5" at the nocks so far. I've worked the limbs down to just over .5" thick at the fades tapering to just over .25" at the ends.
I've never worked one with reflex like this before and looking for some advise before going too much farther.
On the tiller tree I have the linbs bending nicely, but , the scale is showing 60# before the limbs are bending far enough to reach a low brace.
I guess my ? is, how much weight does a reflex stave like this take to brace comparesd to draw weight at 28"?
 
 
 
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Offline DCM

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Re: Osage flatbow questions
« Reply #1 on: February 20, 2009, 09:30:00 AM »
It's a really tough question, at least for me to answer.  I think lots of folks simply draw the bow with a long string (as short as practical if you get my meaning) to the desired final weight, or close, and when the draw lenght to that weight is say 7", 8", then one can be assured it's not overtaxing the bow to brace it.  I tend towards more like 40# @ 8" on a long string, but I rarely make bows over 60# and I'm extrodinarily careful about crushing a belly unecessarily during construction.

Heavily reflexed bows will show enormous weight at brace, so once you have it braced to say 5", be extra careful about giving draw weight until you have your tiller pretty much nailed.

BTW, you may be a little generous with width for 60# @ 28" or less.  1 3/8" would probably work.  Now's the time, if you are inclined in that direction.  1/2" at the crown is about as thin as I care to have an osage flatbow limb.

I'm working an osage bow right now, 59" ntn, 1 5/16" wide for 60# @ 27".  I may not have enough wood, but 1 1/4" to 1 3/8" is real common for such bows, depending upon the width taper.  You might run 1 3/8" parallel out as far as it goes and see where that leaves you.

Offline Ol'school

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Re: Osage flatbow questions
« Reply #2 on: February 20, 2009, 09:37:00 AM »
On the long string I'm hitting 60# when the tips have moved 6", still about 3" short of brace height. I'm aiming for 60-65# at 28"
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Offline John Scifres

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Re: Osage flatbow questions
« Reply #3 on: February 20, 2009, 10:30:00 AM »
You are way too heavy to think about bracing it.  I like to get my desried draw weight at 16" before I think about it.  It is critical not to have any big problems before bracing.  Careful layout and attention to detail on initial wood removal go a long way to making weight.  

I'd double-check your thickness.  It looks a lot thicker than 1/2" at the fades.  I generally get mine 5/8" or thinner.  For a 58" bow that is 1.5" wide, you are going to have to be pretty thin.  If it were me, I'd narrow it to 1-1/4".

These short bows require very patient tillering.  A rigid-handled bow, drawn to 60# at 28" is asking a lot until you are a very proficient bowyer.  

For the TBJ Ambush Bow Contest a few years ago, Tim Ott, one of the best osage bowyers I know, made a couple 58" NTN but they required great wood and the best Tim could do in tillering.  I make my short bows bend in the handle.

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Offline Art B

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Re: Osage flatbow questions
« Reply #4 on: February 20, 2009, 12:01:00 PM »
Your width should be fine for now since your finished length is going to somewhat shorter than the 58" ete (end to end) you have now. You can reduce later if the wood warrants. The more reflexed your limbs the less belly taper required, even less for the pyramid limb design. So you may end up more whip tillered then you want if not addressed now.

By putting your bow on a tillering board and leaving at brace heigth (assuming an even tiller and not overly heavy) for a half hour or so, will help eliminate  some of that early weight and give you a more accurate up front reading.

Your bottom limb looks rather short (pictures are often deceiving I know), how far are you off-setting your arrow pass? ART B

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