Primitive Archer
Main Discussion Area => Bows => Topic started by: ShinneryOak on November 17, 2009, 05:17:40 pm
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I'm reading Hunting The Osage Bow by Dean Torges and was a little surprised to see he advocates making the lower limb up to 1 1/4 inches shorter than the top limb. All the plans I'd seen before had basically equal limb length, with the lower limb tillered a little stiffer. He goes into a long list of benefits for this design, mostly better balance, durability, shootability, etc. Is anyone using this design much ?
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I make my bows 63" and shorter with lower limb 1-2 inches shorter, but don't bother often on longer bows.
Dave
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Yep asymmetrical, you'll like it. ;)
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Being making them equal length and assymetrical, and from what I see, assymetrican are more quiet and accurate
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I make mine equal length, but the top limb usually bends more (about 1/4"-1/2"). Given that I shoot with the heel down, this is perfect.
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Ive made all mine with the bottom limb 1-2 inches shorter...(I read the same book before I made my first bow) I like it better that way...thats really the only way you can get a center shot bow with a shorter riser section...IMO
-Ky
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Asymmetrical seems to work better for me, too, for making and shooting. I pretty much see it as a personal preference...
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I make mine equal length,unless I have a problem and need to shorten the bottom limb.
Never noticed any difference in the way they shoot. Also if you plan to do that you will need to pick the top limb at the start witch is not a big problem ,but I usually don't do that till I get them
to low brace and see where the string tracks. Either way works fine,to each there own. :)
Pappy
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I make mine with a longer upper limb too. When you use a bulbous handle and let the fulcrum hit the web of your hand, it makes for good pointability and a "quiet in the hand" feel.
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im from oklahoma so all this shorter longer well i just dont need that kind of pressure on my little old head so i make all mine the same and it seems fine.
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Well I may have to try it next time. Torges says it does make the lower limb harder to tiller, especially on short bows. Does that seem true?
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More precisely, Dean advocates putting the arrow pass at dimensional center. Technically, from the of the arrow at least, the limbs are of equal lenght. That the bending portion of the lower limb is shorter (part of it being occupied by handle) means, particularly on a shorter bow, it needs to be a little wider and carefully tillered to avoid overworking it. I try to visualize the apex of the tiller curve at the arrow pass and it all seems to work out.
In fact, on a bow where arrow pass is arbitrarily positioned 2" above dimensional center, the upper limb is "shorter" in terms of the geometry at the string grooves, even if the bending portion is "the same." That's why, I think, Dean and others assert such bows may tend to fatigue the upper limb more quickly. Even though they have "equal" bending lenght, the positive tiller required to offset the asym of the geometry means they have to bend farther, causing more set. Since we can't abide arrow nock downward travel on the power stroke, for want of interference, "negative" tiller is not an option.
In practice I make 'em all different ways and honestly any difference in performance I'd have a hard time quantifying. But I do prefer arrow pass closer to center.
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There is no doubt that every bow I've made the lower limb has been more stressed than the upper and needs to be made stronger some how!!!
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Hi, I've made them both ways and don't see a real difference in performance. If there is a difference, you'd just have to be either a better bowyer, or a better shot to notice. Making them symmetrical is a little easier for me and allows me to flip the bow end for end if the string lays a little off center. Historically you might take note of the fact that different cultures seem to have held strong preferences. For instance, the symmetrical bows of the Ottoman Turks and the very asymmetrical yumi of the Japanese are certainly very different. Ron
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It was standard British practice for centuries and American practice until the middle of the last century to make the lower limb one inch shorter so the arrow would pass closer to the center of the bow's length.
In the 1930s and 1940s, C.N. Hickman introduced a design with a longer handle and both limbs the same length. The bow hand was placed on the lower half of the handle, leaving an equal length of handle above. The arrow could pass at the center of the bow's length and still have the limbs equal.
I usually make my handles 5" or 5-1/2" long and gain about an inch toward center for the arrow. I make my limbs equal length and the bows shoot fine.
Reparrow man
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If it's true that equal length limbs overstress the top limb it should be way more common for top limbs to fail than bottom, but I'm not sure that's really the case. If not, then tillering the lower limb stiffer should do the same job as unequal limbs. Does anyone notice top limbs failing more than bottoms?
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I have probably had more top fail but I think it is because I build a lot of character bow and the one with the most snake or knots or other character I try and use on top. On good clean bows I haven't noticed it. :)
Pappy
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I personally only get overstressed lower limbs, but still haven't got my head around the mechanics of how pulling the bow off centre affects the leverage of the string, and also it depends on how you hold and pull the bow, if you dig in the heel of the hand etc.
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Give this a read, maybe several reads...maybe all of this will make more sense then.
http://bowyersedge.com/organic.html
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Thanks for posting Tom, love to read his stuff,....don't agree with everything he says, but love to read his stuff ;D
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Good link Tom! The first part also addressed a question I asked a while back. He believes quick drying osage and naturally curing osage over a much longer period has no difference on the bow....Sorry- I know that was off topic, but you get a lot of different opinions regarding aging wood on here....
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The bow Im hunting with this year has a lower limb 3/4" shorter than the top. I tried out what Dean was speaking of. I have to say, I like it. It spits an arrow well and seems to have no hand shock.
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Good point Manny, Dean never intended that every one should agree with him, these are just his words for us to enjoy.
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The first few years I built all my bows with the top limb 1 1/4" longer than the bottom.They perform very well. The last few years I have built nearly all equal lenght limbs,they perform very well.Maybe I'm just not sensitive enough to detect a difference. ;D God Bless
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You have to admire Dean and his ability to get someone to thinking. Dean's article, the way it was presented, makes a strong case for negative tillered bows. I know some of the positive tillered bows that I gave away to certain individuals could have benefited from a stronger upper and/or lower limb. So Dean's argument does have merit.
I like to think that everybody is a little bit right and everybody is a little bit wrong on certain matters. I think that's the case here. Dean presented his case on equal tip weight/strain alone. Here, a bow can be tillered for above or below of the dimensional center of the bow depending on where the greater hand pressure lies. It would be easy to build a bow with a two foot lower limb and a four foot upper limb and have equal tip strain. But then you would have to account for unequal limb mass.
Jumping back to the bows I gave away that ended up with more positive tiller than desired, these bows were gripped futher above dimensional center than designed creating greater strain on the upper limb. Here a more negative tiller bow would have been approperate. Same thing happened to many of my bows where the shooters applied to much heel pressure than designed. Here a greater positive tiller would have surficed.
But IMO, to get it right, you have achieve both equal limb strain AND limb mass (as close as possible). Then using the proper grip per arrow pass layout to maintain equilibrium, you will only have a need for a positive tiller bow. Adding "equal limb mass" only adds to creating even less shock to the bow. ART