Author Topic: static tips and levers  (Read 12386 times)

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Offline BowEd

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  • BowEd
Re: static tips and levers
« Reply #60 on: April 27, 2017, 12:58:57 pm »
The Japanese shot longer bows from a horse.I forget the name of those bows.Starts with a Y.
I look at shorter versus longer like barrels on a gun.The slightest twich on a pistol and your way off.Not so with a longer barrel.All depends what way you look at it.It's the early tension mostly too talking about accuracy.Probably a little of both.
For manuverability ease walking through the woods brush nocks seem the most useful to me in a lot of ways.
As you said I think comparing 2 well built bows of 2 different designs recurve versus straight recurve will shoot the fastest.
BowEd
You got to stand for something or you'll fall for anything.
Ed

Offline Ballasted_Bowyer

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Re: static tips and levers
« Reply #61 on: April 27, 2017, 07:56:47 pm »
I'm not sure I agree that a sharp static has higher brace tension than a rounded static.., but here's how I explain what a contact recurve does. Think of two pencils, a regular one and a "golf" pencil (short). Both are the same thickness, but the long one is easier to bend because the ends act like levers.If you hold the regular pencil with both hands near the middle, it is hard to bend just like a golf pencil.
 When a recurve is at brace, it "acts" like a bow that is shorter- it acts like a bow that is only as long as the distance between the points of contact. This short bow is harder to draw because it is short.Hard to draw= high early draw weight. At full draw, the string lifts off the recurves, and now the bow "acts" like a bow that is longer, giving you more leverage to bend the bow. So a recurve acts like a short, stiff bow early in the draw cycle, and a long bow later in the draw cycle.

^----^ correct answer!
For science types refer to the following:
D = F * E ( L ^ 2 ) / ( W * ( H ^ 2 ) ) where
D is the displacement of a beam fixed at one end with a rectangular cross section of dimensions Length, Width, Height, modulus of Elasticity, and a Force applied to the loose end.

The above approximates a limb where the fixed end of the beam is the inflexible part of the fade. Where the limb is a more complex shape use calculus to integrate the solid.

Edit: fixed the equation
« Last Edit: April 28, 2017, 12:07:56 am by Ballasted_Bowyer »
Acts 10:12-13  "It contained all kinds of four-footed animals, as well as reptiles and birds. Then a voice told him, 'Get up, Peter. Kill and eat.'"

Offline Ballasted_Bowyer

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Re: static tips and levers
« Reply #62 on: April 27, 2017, 08:11:05 pm »
Yes, but we build bows to a certain final draw weight. The recurve bow gets "longer" as the string lifts off. This lowers the final draw weight. So if we have your hypothetical bows the straight one will keep climbing to a higher draw weight while the recurves weight will level off. If you re-tiller the straight one to the same final draw weight you loose the early draw weight.
So really recurves don't increase the early draw weight. They decrease the final draw weight and thus only give the illusion of increasing the early draw weight.

Thus going back to the earlier post about the bow that reached final draw but had no string let off. Since it had no string let off it didn't have any lever advantage to decrease the final draw weight. Therefore, just because it is a recurve, it doesn't necessarily mean it had better early draw weight since it didn't have string let off. That is unless there is something we are missing still.

If the bow is long enough that the string never lifts off the tips you have shorter long bow with really heavy tips. The string should lift off the recurves area. The earlier it does the higher the slope of the force curve early on. Once the string is off the limb, the force draw curve is linear. Not taking weight into consideration, the perfect static recurve would have a gentle curve so the effective limb lengthened continually until just before full draw. With a wood bow this could be done with a deflexed handle. A working recurve of similar concept would have the string lift off a little sooner. With the static option, one could laminate something very light into the recurved portion to save weight and have enough width for the string to rest on.
Acts 10:12-13  "It contained all kinds of four-footed animals, as well as reptiles and birds. Then a voice told him, 'Get up, Peter. Kill and eat.'"