The Case for the Valley

The case for shooting from the valley goes like this: 

It is crucial to release each arrow from a consistent draw weight.  Obviously, you don’t want to release it before the valley because a) you would be wasting the bow’s potential power, b) your holding weight would be higher than it need be and c) the draw weight is changing so quickly that even a tiny variation of draw length would have a huge effect.  Similarly, if you draw back past the valley, the draw weight starts to climb very rapidly indeed (the line on the graph becomes vertical almost immediately), so the argument about tiny variations of draw resulting in large variations of weight applies even more when shooting from the wall.  In addition, when shooting from the wall the arrow experiences uneven acceleration – high, low, high – as it moves into the valley and out the other side.  This tends to give inconsistent arrow flight.  The practical demonstration of this is that the arrow will go high if shot from in front or behind the valley – because of the higher draw weight – and it will be difficult to achieve consistency in either case.

So, its advocates argue, the only sensible place to shoot from is the valley, where small inconsistencies of draw length don’t matter as it all has more or less the same draw weight, so the arrow is always given the same, smooth acceleration. 

The Case for the Wall

The case for the wall is based on the argument that it is easier to achieve consistency of draw from the very positive wall, than from the rather nebulous valley, and that, in practice, this added degree of consistency more than makes up for any theoretical disadvantages.  But what are the disadvantages really?  It is the total amount energy stored in the bent limbs that determines arrow speed, not the draw weight at that particular point, and stored energy is always higher the further the bow is drawn, so one 'valley' argument falls.  What is more, stored energy is only increasing while the limbs are bending – the bending is precisely what stores it.  That means that, beyond the wall, there is no storage however much energy you put into drawing the bow. The wall marks the point where the wheels or cams no longer have any effect, and the limbs stop bending: it would take a pull of 400 to 500 lb to bend the limbs of a typical 50-60 lb peak weight compound any further.  You can, of course, make the scales say anything you like, just by pulling harder: as Ben Jones of Merlin Bows (http://www.merlin-bows.co.uk) points out, a coat hanger will register just about any peak weight you want on the scales, if you pull it hard enough, but you might be a bit disappointed at the arrow speed!  There goes another 'valley' argument.

About all we are left with is the changing acceleration as the arrow passes through the valley and out the other side.  This is real, but on a modern compound with well designed wheels or cams its practical effect is negligible, or so proponents of the wall maintain. Provided draw length is truly consistent there should be no difference in grouping from the wall, the valley, or anywhere else.   If there is, then the first thing to check is your cam timing.  If this is not spot-on, you will be severely punished for even the smallest variation of draw length.

 The Verdict

One thing is clear – it is possible to shoot top scores off the wall and out of the valley.  Larry Wise and Frank Pearson illustrate this point perfectly, the one being a dedicated valley shooter (or at least he was, and shot extremely good scores at the time), the other drawing hard against the wall.  The key, as both schools of thought would agree, is achieving the same arrow speed shot after shot, through the whole of a long, hard day’s shooting.  So, which is likely to be the more consistent method? 

The answer, I believe, depends mainly on the design of the bow.  If your bow has round, or nearly round wheels and a 50% let-off it is likely to have a long, easily found valley and a very spongy wall.  At the other end of the scale, if you have an hard cam and an 85% let-off, the chances are that that you have no valley to speak of, but your wall is like hitting a … well, a wall!  The same applies to any bow having draw stops ('wallbangers') built in to the cams.  In the first case you would be well advised to shoot from the valley, and in the others, you have little option but to shoot from the wall. 

Wheel/cam adjustability is another factor to consider.  If your bow has fixed length steel cables, and no other means of adjustment, then cam timing is apt to be a bit hit-or-miss, unless it has been set up specifically for you, taking into account your personal nocking height, tiller, release and hand position – all of which can affect timing significantly.  In this case, the weight of evidence suggests that you might get better groups shooting from the valley.  On the other hand, with modern fibre cables (Fastflight, BCY 450+ etc), where precise adjustment of cam timing is easy, the wall is again likely to be the better option.

So, if you have a more modern bow, with a 65%+ let-off, fibre cables and wheels/cams specifically designed to stop dead at the end of their effective draw you will probably get the best results shooting from the wall.  Lower  let-offs, steel cables and round, unstopped wheels all suggest the valley as your best bet.  But remember that both techniques can work equally effectively, so don’t feel you must use one or the other – if in doubt, try both and let your scores decide.

 A Footnote – Underdrawn Arrows

Why do slightly under-drawn arrows go high when shot from a compound? There is no doubt that they do, but equally, there is no doubt that it is stored energy, not draw weight as such that determines arrow speed.  An underdrawn arrow is always slower than a correctly drawn one and a speed meter will soon confirm the point.

I have seen explanations in terms of cam timing (I can’t remember where), but I was not convinced, and also in terms of the nocking height, but that becomes effectively higher the shorter the draw, which would tend to send the arrow low, not high.  Personally, I suspect that the answer has something to do with changing pressure on the bow hand, but I’m not at all sure.  Any solutions?