Static bow design ?

[Stick Bender]

Hi Fellas I have a question about static limb bow design for example if you had a fixed limb thickness & length.  Does it increase & decrease  the weight of the bow by increasing & decreasing the length of the bows static portion, I'm not talking piquing the bow ,the limb has a fixed length in the hypothecate design ,I'm talking increasing or decreasing the static length that would increase & decrease the working area of the limb at a fixed over all length ?

[Badger]

   I would think that the further away from the riser the bending portion was the less impact on draw weight it would have and vice versa. So I would say yes same thickness more bending limb would give lower draw weight. But I could easily be wrong, I am just basing that on my wood bow building experience where we never actually measure thickness.

[Stick Bender]

That's what I was thinking too but I was wondering if the increased lever length on the static portion would  would negate the shorten stronger limb that's the part I can't put my mind around ?

[PatM]

It' has to be viewed from the standpoint of material strength and weight. Hypothetically  will not be the same as real world scenarios.
 The draw weight will increase as the bend is crowded into a shorter area and the static lever weight will also increase.

 People chase that balance all the time, trying to tip the scales in the favor of the working limb. But the working limb has to be holding up.

[Badger]

  A couple of years ago I built a couple of heavily reflexed (12") extra large recurves I called hinge bows because they had very short working areas. Most all the bend was right out of the fades and remaining part of the limb was static. The limb was very wide at the bending point but only a little over 5/16 thick. The bow broke down rapidly in less than a dozen shots. I tillered it never going to full. The first full draw shot was extremely fast and every shot thereafter continued to slow down until it leveled off after about a dozen shots.

[simson]

I believe there is optimum length for the levers by a given bowlength. It also belongs on the drawlength and angle of the lever. Like the others said a longer lever increases draweight bbut only to a definete point where lever mass or instability become too heavy.
So for me an angle of about 60° and 4" levers (for 56 -66" bow) are a good point to go from. I do shorter levers on shorter bows.
Forgot to say: a big thing is also the point of string lift off to get the full advantage of a static.

[Badger]

I believe there is optimum length for the levers by a given bowlength. It also belongs on the drawlength and angle of the lever. Like the others said a longer lever increases draweight bbut only to a definete point where lever mass or instability become too heavy.
So for me an angle of about 60° and 4" levers (for 56 -66" bow) are a good point to go from. I do shorter levers on shorter bows.
Forgot to say: a big thing is also the point of string lift off to get the full advantage of a static.

  Simpson, a couple of things come into play when shortening the working portion of the limb. #1 most of the energy losses due to vibration disappear and #2 with shorter working areas in the limb the bow will tolerate a lot more reflex without becomming unstable at brace. Of course there is always the problem of over stressing the limb which none of us have been able to get past so far. I really don't think it is practical for a wood bow where on a fiberglass bow it might work out very well.

[simson]

Steve, I'm 100% with you.
But Stick Bender is discussing the influence of decreasing/increasing the lever by a given length of the working limbs.
This is an interesting item for me, I love the statics and I always try to do next a bit different to see what happens.

Bob Kooi (from Netherlands) has done a lot of publications, also discussing these constellations. There are a lot available in the net, just google his name.

Maybe I didn't understand correctly ? You know - not my moms language.

[Badger]

     I agree with you Simpson, there likely is an optimum arm length where the weight starts to overide the stored energy gains. It may have something to do with the size f the hooks but I can't say for sure. Kind of like scaling, where a larger hook could tolerate a longer lever. On my short lived experimental bow with the giant hooks it did demostrate a few things I have always suspected, I had energy storage of 120% of draw weight and 10 grain per pound at 28" draw did exceed 200 fps. I don't think the design would ever work with wood though. The bows performance deteriorated from the very first shot.

[Marc St Louis]

It is my experience that short hooks will equal or surpass the performance of longer recurves regardless of bow length

[PEARL DRUMS]

I agree with Marc on short hooks, but I have no chrony to prove anything. Just my eyes watching arrows leave a bow.

[DC]

It is my experience that short hooks will equal or surpass the performance of longer recurves regardless of bow length

You've got my attention now. Short meaning smaller radius? Less total reflex? Both?

[simson]

Marc, Steve:
What do you think about following test:
1. Checking out drawweight /-curve for a common static with 4" levers.
now compare with
2. same bow with tied on nocks to shorten the levers at let's say 1", of course with a shorter string to from the same braceheight as bow one

What can we expect in sight of drawweight and curve?

[PatM]

You just wouldn't be able to use a shooting test with such a bow since the shorter string position  would be carrying the dead weight of the tips.

 Also the weight will jump since you're not re-tillering.

 I'm in the longer hooks camp as long as weight is minimized.

[Badger]

  I notice in a lot of Marks bows he has a medium length hook but he also has a gradual curve coming into the hook. Thats a good strategy for stored energy.

  Bows are hard to really gather meaningful data from because there are so many aspects to similar designs that can affect the outcomes. The amount of working limb is a major contributor to energy losses. I think this is one of the reasons shorter recurves tend to perform better than longer ones.

  My test bow I spoke of earlier had very long narrow static tips with large sweeping static curves. I had low mass in the outer limbs and tons of stored energy plus it was very stable with no tendency to twist. The only problem was the wood couldn't hold up to such a short bending area.