Author Topic: static tips and levers  (Read 1582 times)

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Offline bushboy

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Re: static tips and levers
« Reply #15 on: April 20, 2017, 04:17:59 pm »
The bow wants to bend in a arc but the recurved resist ,placing more tension on the limbs,thus raising early draw weight.smooth draw as it is referred,means there is hardly any noticeable weight gain from brace to full draw from my experience.
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Offline Danzn Bar

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Re: static tips and levers
« Reply #16 on: April 20, 2017, 04:27:53 pm »
It's all about string angle........
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Offline PatM

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Re: static tips and levers
« Reply #17 on: April 20, 2017, 04:47:04 pm »
It's all about string angle........
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Offline loon

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Re: static tips and levers
« Reply #18 on: April 21, 2017, 12:40:21 am »
yeah, I mean, you can have 90 degree short hooks that are vertical at full draw but still have plenty of stack..

Offline Stick Bender

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Re: static tips and levers
« Reply #19 on: April 21, 2017, 02:07:59 am »
Ok maybe Im thinking about it wrong but I always thought that the early tension had nothing to do with recurve angle but how far foward of the back the tips are regardless of design ,strait,recurve etc. I think Tim Baker did some writting on the subject !
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Offline gfugal

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Re: static tips and levers
« Reply #20 on: April 21, 2017, 06:02:55 am »
Ok maybe Im thinking about it wrong but I always thought that the early tension had nothing to do with recurve angle but how far foward of the back the tips are regardless of design ,strait,recurve etc. I think Tim Baker did some writting on the subject !
I think I was wrong when I thought bracing eliminates all pre-brace stored energy. I think bushboy is right in that it's like a pre-stressed spring. Even though its braced and that's its new starting point, the limbs still want to return to their unbraced profile.

Threrfore I would say early tension is based on how far the working limb has to travel to brace. When you brace a recurve you don't get the tips moving to brace height, just the end of the working limb. The tips may still be hanging back a bit at brace, especially if it's a sharp static. However, with a reflex you do have to make the working limb travel further to brace therefore you get eary tension greater than a straight limb. If you had reflex and recurve you would have both an increase in early draw weight and a decrease in final draw weight due to the lever effect Aaron and DC said. Thus you get a nice fat force curve.

Sorry PatM i'm going to have to disagree with you in that recurves do decrease final draw weight. If you increase the lever length (moment arm) you need less force to produce the same torque. Just like a longer wrench is easier to loosen those lugnuts on a tire. You get more torque for less force. So if we have less force near the end of the draw due to longer moment arms, we thus need less force for the same bend. In other words we have less draw weight at the end than if there wasn't recurved tips.
« Last Edit: April 21, 2017, 07:27:38 am by gfugal »
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Offline PatM

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Re: static tips and levers
« Reply #21 on: April 21, 2017, 06:59:23 am »
My comment was tongue in cheek. The rate of increase may diminish but the actual draw weight does not decrease or let off.

Offline gfugal

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Re: static tips and levers
« Reply #22 on: April 21, 2017, 07:31:51 am »
My comment was tongue in cheek. The rate of increase may diminish but the actual draw weight does not decrease or let off.
Touche. That is true. It never decreases in relation to itself. You will never lower the draw weight from a previous weight at an earlier draw (unless you have a compound  ;D). You're right. However, it does decrease in relation to non-recurve bows, and that's what we were talking about.
Greg,
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Offline Badger

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Re: static tips and levers
« Reply #23 on: April 21, 2017, 10:26:45 am »
  I think you need to think about the spring and the geometry separately. Almost all springs build at a predictable rate as long as they are pulled at the same angle. Lets say a limb gains 1# per inch if pushing down on the tip. That will start before it was braced at any amount of reflex you have. Now once you hook a string to it the geometry changes so now you are no longer pushing or pulling straight down on the limb tip. If you have a static recurve with 4" of string contact on the limb you are not pulling down on the limb tip, your lever just got 4" shorter and will require more effort to move.

   If you take an unbraced bow and put a long string on it and pull it down to say 28", say your string was hanging loose at 6" so your movement of the string was about the same but no preload on the limbs. The weight at 28" will read very close to what it reades even if the bow were braced and preloaded because of the geometry. 

Online Selfbowman

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Re: static tips and levers
« Reply #24 on: April 21, 2017, 01:00:10 pm »
I don't know about all the math but if the static does not work the extra mass does not have that much effect in performance. The mass is just along for the ride. That's why I have not built them anymore. Arvin
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Offline PatM

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Re: static tips and levers
« Reply #25 on: April 21, 2017, 01:04:53 pm »
Also not true. The outer parts of a bow are pretty dead unless a bow is whip tillered.

Offline Marc St Louis

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Re: static tips and levers
« Reply #26 on: April 21, 2017, 01:44:26 pm »
I don't know about all the math but if the static does not work the extra mass does not have that much effect in performance. The mass is just along for the ride. That's why I have not built them anymore. Arvin

I beg to differ.  A well built static will outperform a straight limb bow by a wide margin
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Offline willie

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Re: static tips and levers
« Reply #27 on: April 21, 2017, 01:48:32 pm »
Has anyone found that when a static recurved tip is used, the limb has to be heavier or stiffer?

BTW, here is a link to last years discussion.

http://www.primitivearcher.com/smf/index.php/topic,56255.0.html

Offline PatM

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Re: static tips and levers
« Reply #28 on: April 21, 2017, 02:42:02 pm »
Has anyone found that when a static recurved tip is used, the limb has to be heavier or stiffer?

BTW, here is a link to last years discussion.

http://www.primitivearcher.com/smf/index.php/topic,56255.0.html

What do you mean by heavier or stiffer? Those are functions of draw weight choice.
« Last Edit: April 21, 2017, 05:23:08 pm by PatM »

Offline willie

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Re: static tips and levers
« Reply #29 on: April 21, 2017, 03:30:30 pm »
Quote
What do you mean by heavier or stiffer?

thicker or wider than an otherwise comparable length and draw weight bows, with out the hooks.

If there are advantages to static recurves that increase performance, then there should be extra wood required to store the extra energy. Of course, extra performance can also come from stressing a bow harder or is that what is really happening when special claims are made for bows with static recurves?