Bow length and draw force curves

[Rog600]

I think I understand about too short a bow for an archer leading to stacking and am trying to see how too long a bow might affect shooting. Am i along the right lines in thinking that with too long a bow, the stacking bit of a draw force curve isn't reached but in the extreme, the sweet spot (or sweet region) of the dfc isn't reached either? And what effect, if any, does this have on form (I've found that I prefer a little more on the fingers than a little less, if that makes sense) and on group size.

This is all hypothetical as I try and learn new stuff and improve my understanding. Any links to papers, diagrams, etc, most gratefully received! Thanks. Rog

 

[Senlac]

I can't help on the long- and short- question, though I'd be very interested in what others have to say.
However, in case it's helpful, I'm attaching some DFCs I measured for my two bows: both 25" riders with medium limbs.

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I can't help on the long- and short- question, though I'd be very interested in what others have to say.
However, in case it's helpful, I'm attaching some DFCs I measured for my two bows: both 25" riders with medium limbs.

 

[Rik]

The point is that most limbs don't have a pronounced enough reflex point in the curve to be noticeable. There are some which are exceptions - super recurves like Border's or Uukha, for example.

This is a bit different to stacking, though. I wouldn't expect any competently made limbs to stack noticeably under most circumstances. Cheap limbs might, though. I've shot bows which stack (a major achievement at my draw length ), but not for nearly 30 years. . .

 

[Rog600]

Thanks, so other than in extremis the dfc of modern limbs are broadly linear? In which case the merits of a longer bow are related to string angle and finger pinch, and that of a shorter bow, one related to a lighter mass in the bow hand? Or is there something to do with the 'shape' of a bow at full draw that is advantageous at a certain length; I'm imagining a long bow drawn to draw length looking like an elongated, narrow parallelogram, and a short bow drawn to the same length looking more square. Please excuse my layman's description! I know from changing from my 70" to 72" set up with the same limbs, the string is more comfortable (could be in my mind, granted) but that I understand the angle of the string at the limb tips must be more acute on the longer bow at full draw. My shooting has improved but is it down to the change of 'shape' due to the increase in bow length at the same draw length, the reduction of string angle at my fingers, general improvement that may have happened with the 70" bow, a combination or something else? I can see that a longer bow can eventually be too long, but there must be a point between too long and too short and a corresponding effect on precision, maybe?

 

[Yew Selfbow]

I'm just playing devils advocate here, but aren't draw force curves pretty much meaningless.

 

[Deleted member 7654]

The problem is you haven't defined any of your terms or what sort of bow you are talking about.
If you are talking about modern materials and deflex/reflex designs they are all so good and have so much spare performance it is probably pretty irrelevant.
E.g they can all probably be over drawn by a good 6" with no problem.
If you are talking about wooden bows and "long" being in excess of say 6' 6" the length adds considerable inertia.
Simplest way to illustrate is twanging a wooden school rule on your desk, as you shorten it the note becomes higher. Short limbs tend to be faster, long limbs tend to be smoother and better suited to shooting heavier arrows.
e.g My best flight distances are similar from a 100# @ 32" warbow (Elm) and a 70# @ 24" flight bow (Osage) yet the warbow has a lot more energy put into it.
In terms of force draw curve with wooden bows, adding reflex gives good early draw weight (which shows in the F/D curve) but limits draw length as there is only so much you can get from a bow.
The whole stacking thing is more about geometry than the materials.
All those F/D curves are pretty much the same, being from moder deflex reflex designs), longbows are remarkably linear and if you realy want extreme shape to the FD curve you need to be looking at Asiatic composite designs or compounds (spits on floor). Once Hickman had come up with the basic moder deflex/reflex design*, the rest is small incremental improvements.
Del
*He came up with the design using a F/D curve plotting machine which he built. He did it to allow him to compete despite having lost some fingers in a rocketry accident which meant he coulld no longer pull 50#, his design allowed his 35# bow to out shoot the 50#.
There is an biography of Hickman which is a good read:-
Clarence N Hickman the father of scientific archery ISBN0-9613582-0-3

Note:- all just my opinion of course, terms and conditions apply and I reserve the right to be wrong (especially if my wife says I am )

 

[AndyW]

Asiatic composite designs or compounds (spits on floor). Once Hickman had come up with the basic moder deflex/reflex design*, the rest is small incremental improvements.

Until the compound bow.:duh::duh::duh:

 

[Deleted member 7654]

Until the compound bow.:duh::duh::duh:

(Groan)... yes that is self evident, but the F/D curve of a compound has virtually nothing to do with the limbs, it's basically down to the cams, thus I feel it's not relevant to the discussions.
If we really have to discuss compounds, the cam is merely a development of the lever action of the siyahs of the Asiatic compounds, add in a block and tackle effect to pull high poundages through long draws and there you have it.
Del

 

[AndyW]

Not entirely fair of me, having read again. I just don't get how you can hold up one design improvement as a shining light and in the previous sentence spit on another.
Whatever your person bias - they are both steps in improved efficiency.

 

[AndyW]

(Groan)... yes that is self evident, but the F/D curve of a compound has virtually nothing to do with the limbs, it's basically down to the cams, thus I feel it's not relevant to the discussions.
If we really have to discuss compounds, the cam is merely a development of the lever action of the siyahs of the Asiatic compounds, add in a block and tackle effect to pull high poundages through long draws and there you have it.
Del

(Groan) - you hate compound bows - we get it. I wasn't talking about the FD curve but you replied 2s before my next post explaining - (Groan)

 

[Deleted member 7654]

(Groan) - you hate compound bows - we get it. I wasn't talking about the FD curve but you replied 2s before my next post explaining - (Groan)

I don't actually hate compounds, I admire the engineering in them.
But I do feel they are a somewhat specialised niche which can detract and distract from a discussion of the fundamentals.
I think the difference is that Hickmans improvements are still fundamentally a simple bow and string, whereas the compounds is a simple bow plus a block and tackle and a pair of cams.
Del
(groany groany groan groan )

 

[geoffretired]

It is possible to have a bow with let off at the later stage of the draw without cams of the block and tackle variety.
Firebrand Technologies made one using a stripped down Oneida. I did a strip down of my Oneida as it seemed such a fascinating design.
When the pivot points and associated lever lengths/angles are adjusted, the draw can be smooth and sweet.
I feel that all bow types add to the fascination of archery; and the variety gives everyone something to discuss, as opposed to repeating what is already known or part known.
Understanding one bow type seems to me to give the interested parties some common ground along with some challenges to what they know. Taking on new thinking required with new uses of older technologies, can help to deepen our understanding of our own particular favourites.
A couple of examples are archer's paradox and centre shot off sets.
I know Del has clear understanding of Archer's paradox and I know some who get it confused with centre shot off set. I think watching compounds and recurves in slo mo action can help to demonstrate the underlying differences, but perhaps more importantly, the common truths about arrow launch.

 

[AndyW]

I don't actually hate compounds, I admire the engineering in them.
But I do feel they are a somewhat specialised niche which can detract and distract from a discussion of the fundamentals.
I think the difference is that Hickmans improvements are still fundamentally a simple bow and string, whereas the compounds is a simple bow plus a block and tackle and a pair of cams.
Del
(groany groany groan groan )

Fundamentals with compounds - sadly there doesn't seem to be the will to go somewhere new. 20+ years ago they did but sadly no longer. At least the short, fast and stupid trend is dying off as the U.S. realises you still need to be able to hit the thing as well as blow a hole through it.