Primitive Archer
Main Discussion Area => Bows => Topic started by: Part time Archer on February 10, 2019, 08:23:37 pm
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I read this on a Longbow site that they made their upper limb 4 lbs weaker to help shoot various spines can anyone explain please?
Fisk Longbow
This produces a bow with a tiller between top and bottom limbs that varies by four pounds. In other words, the top limb pulls four pounds less than the bottom limb. This produces a "heavy chested" longbow. With this design, any of my longbows will shoot a variety of differently spined arrows well, including graphite, carbon, wood and aluminum.
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I don't buy this, spine is spine. The heavy chested tiller would have more effect on the nocking point.
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Sounds like it's been somewhat embroidered.....
How do you measure the draw weight of an individual limb? ::)
Most bows have a slightly stiffer lower limb... I can picture what they mean by "heavy chested" ( like a bloke standing up puffing his chest out, giving a more rounded top) but I've not heard it used of bows before.
Del
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The term used in the past was breasted tiller. Sounds like he's made up some stuff to make it seem worthwhile.
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Thank you both. For the sake of argument , I could imagine the handle in a vise and not moving . 2 separate strings , not connected , attached to 2 scales against a very detailed tillering board measuring the 4 lb difference. Would be a more standardized way to always ensure bottom limb is timed, or maybe the bottom limb is not over strained , instead of using the old adage of + 1/4 tiller or comstock says 3\8 to 1\2 positive tiller in his book.
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Thank you both. For the sake of argument , I could imagine the handle in a vise and not moving . 2 separate strings , not connected , attached to 2 scales against a very detailed tillering board measuring the 4 lb difference. Would be a more standardized way to always ensure bottom limb is timed, or maybe the bottom limb is not over strained , instead of using the old adage of + 1/4 tiller or comstock says 3\8 to 1\2 positive tiller in his book.
Very difficult to pull a single string in the correct direction to match up with how a normal string would draw.
Del
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True but with the angles drawn out on a tillering board at a given draw length then sure, but then you take the primitive out of bow building and replace it with standardized measureing techniques. Love to see a primitive archer myth busters style approach in an upcoming issue for fun! And discuss 3\8 to 1\2 positive tiller.different weight bows would be different positive tillers if you trying to achieve 4 lb lighter limb on top!
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True but with the angles drawn out on a tillering board at a given draw length then sure, but then you take the primitive out of bow building and replace it with standardized measureing techniques. Love to see a primitive archer myth busters style approach in an upcoming issue for fun! And discuss 3\8 to 1\2 positive tiller.different weight bows would be different positive tillers if you trying to achieve 4 lb lighter limb on top!
No, it's bonkers. It would remove a key aspect of the bows design... that it is fundamentally balanced.
To test one limb at a time would necessitate clamping it and introducing unbalanced stresses.
If you think it is in some way a good idea, you need to sit on the naughty step and have a careful think ;)
Del
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If the person that made the claim was making 100+ pound warbows, then 1/4" positive tiller might equate to 4# lighter on the top limb... :OK but if it was a 20# bow 4# would be ridiculous...
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Is the term referring to all wooden bows or FG bows?
I never heard of it which doesn't mean much. LOL.
Jawge
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O:) You guys rock. Makes me wonder. But wait the site says , When the bows are tillered, I avoid sanding down the surfaces of the FRP to achieve balance between the top and the bottom limb. The top limb lamination are ground 0.004 of an inch thinner than the bottom. .... Hmm which makes it 4 lbs lighter. So is this just for the average 50 lb bow? Your right a 20 lb wouldn't equate but is Fisk using a formula of just a percentage based on weight that would give him for example 4 lb for a idk 50 lb bow and a 2 lb difference for a lower poundage bow. ....... (-P Is there a simple formula that would allow us to assign a lb difference according to bow weight that would be idea of at least ball park for even limb strain and timing because we all know split finger puts uneven stresses on the limbs causing set in the lower unless positive tiller is placed on top. :OK
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)-w( George I would like to apply it to a wooden bow. But this whole talk is about fun and seeing where it goes. It is from a fiber glass site. Don't understand why Fisk would go through all of that. I build I shoot and it doesn't break if I'm lucky. (--)
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This I s .ca wood bow site
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I never measure positive or negative tiller. I simple look at the fully drawn bow and make sure the bottom limb a bit stronger. If this were rocket science or we were building Swiss watches perfection is probably necessary but with wood bows close enough is enough. IMHO!
FG mentality is rarely pertinent in wood bow building. That why we build wood bows. ;D
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A good release will let u shoot a wide range of arrows,,.from a well made wood bow
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I look like to apply this to a wooden bow. Would it make sense that a 20 lb bow to have less positive tiller than a 60 lb bow for split finger? If so then could someone come up with a solution. Maybe just guessing here throwing numbers out there , maybe 1\16 positive tiller adjustment on top limb for every 12.5 lbs of draw weight.
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Yeah could not imagine having that kind of tillering board set up. But could imagine if it was correct to use a simple formula based on adding 1\16 or some fraction for every so many lbs. If it was correct. No I am a wood bow person.
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On wood bows,,.the stave can vary...looking at full draw gives u a good idea of positive tiller,,,and the way it shoots...measuring brace,,,can be deceptive,,,the flight shooting guys are experts on arrow flight
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ThankS everyone. Could imagine a model mini bow of 12 inches having something like 1\32 positive tiller and an 80 inch bow having maybe 3\4 or 1 inch but does weight mass density factor in? Imagine the easy way out fiber glass that the properties never change and you have a plethora of formulas to plug in and make a Lego like bow, not for me !
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I have 2 early 50's Bear Grizzly bows ,and a Stemmler all fiberglass bow . All 3 bows have up to one inch of positive tiller, and deep bending limbs to get proper brace at the riser. At first I thought the bows were just bad from use, and that still could be, but with a higher than normal string nock point they shoot fine.Both Bear bows have static tips.
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On a selfbow only the full draw tiller matters like Brad said. Using staves to build bows there is no "regular" about it. Each is different. Where on a braced selfbow would you measure positive tiller, at the fades? what if there is a hump there or a twist. Neither would prevent the selfbow from shooting well.
Also, with a very loose grip, where the bow can turn in your loosely gripping hand on release arrows of different spines can be shot accurately. This was demonstrated successfully to my by Art Butner years ago.
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Pat C, coming off the fades at three inches the top limb brace is 7 and half inches. Bottom limb is 7 inches.When you measure the widest point in the belly the top limb is 8 inches, and the bottom limb is 7 inches.That is on the fiberglass bow.On the tiller tree at 25 inch draw the top limb is 14 inches,the bottom limb is 13 inches.The 2 old Bear grizzly bows are similar. I only mention fiberglass, and fiberglass lamb bows,because that is what the Fisk bows are with the claims he is making.I am sure I read some were that the old bows were made this , but I don't remember for what reason.
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ThankS for the positive feedback. Love you guys .
:OK