Diminishing returns

[oxnam]

I have been thinking about what it take to test this.  What would be the measure of efficiency, FPS, kinetic energy, momentum, etc?  Would arrow weight be kept constant as poundage was increased or would grain/lb be used to increase arrow weight proportional to bow poundage?  Take into account arrow tuning, optimum arrow weight for a given poundage, bow designs, draw lengths, etc.  It may be quite difficult if not impossible to ever come up with a definitive answer.  I would enjoy reading some standardized testing just to see if there really was a noticeable point of diminishing returns that were not simply related to an increasing denominator (poundage).

[pdk25]

It would be very difficult to test, but if a given bowyer tested enough of a given model using, say, 10 gpp arrows of the same type with all of the bows drawn to the same draw length over a spectrum of bows ranging from 40-70 pounds it could give a rough estimate for that model.  Get a few bowyers and you might have a general rule of thumb.  Very cumbersome, but I would love to see it.  You would need a large sample size to account for slight differences in materials, glue lines, etc..

[gregg dudley]

Diminishing returns does not mean that there are no benefits.  It means that the benefits per pound of increased weight drop off after a certain point.  We all buy into this concept in some fashion by choosing a draw weight for the bow we shoot.  If we genuinely thought that 80 pound bows were significantly more efficient and effective than the mid fifty pound bows that the masses are shooting then we would all be working out like crazy to shoot bows at that weight.

[Terry Green]

Yeah Gregg....a diminishing return is STILL a positive return....NOT a negative return.

A 63# bow with a 630 grain arrow has more power than a 53# bow of the same design with a 530 grain arrow.

[pdk25]

And not by a small margin.

[Bear Heart]

I wonder if this is because a higher poundage bow is not a to scale enlargement of a lighter pound bow but instead has completely different proportions.

[oxnam]

Originally posted by Bear Heart:
I wonder if this is because a higher poundage bow is not a to scale enlargement of a lighter pound bow but instead has completely different proportions.

I think that is a large part of the problem, poundage is often the denominator in the comparisons.  Hence the appearance of a 5# increase at 40# making noticible gains and then a 5# increase at 65# which is much less impressive.  If the fps per second gain per pound was graphed in increasing increments, it will appear that each additional pound has less and less benefit as the weight increases in comparison to the lighter weights.  This is because the percentage of increase keeps declining (the denominator, poundage, keeps increasing).  I really don't think limb mass or those kind of variables are going to be that much of a factor, which is a total uneducated guess.

Now in the real world, everytime weight is increased, the arrow with weight unchanged is going to go faster. There aren't any realistic poundages where there won't be a beneficial gain (not taking into account any issues of being overbowed.)

I would still love to see a bowyer take their bow through that testing process.  ILF's would probably be the easiest to test and probably would have the least bow to bow variance by going from one set of limbs to the next.

[lone hunter]

I seem to remember an extensive thread on this subject, maybe 5-6 years ago. Think OL was involved in it. A search might turn up something. As I recall, 60# was the point where efficiency started to diminish. The consensus, if I remember right,  was that you can't compare bow efficiency by weight alone but also the weight of the arrow.

[duncan idaho]

I wish Kirk and Sixby would comment on this issue.

[swampthing]

This can be seen 2 ways.
           1.  I would say a more "working man" test would be to shoot "heavy shielded boar," {or sow for that matter, nuther story}
 Start with a 450g arrows at various speeds,
Try some 500g arrows at various speeds,
Try some 550's, then 600's, then 650"s, etc... etc... and determine at what point are you "RELIABLY" getting through the shield and at least to the off side rib, every time.  
 Once you achieve that you have just reached the point of diminishing returns of arrow performance. About 58# an 580g should get you there if tuned right.
               2.   Once you got an arrow speed that you can use out to your desired effective kill range, you have just reached the point of diminishing returns. For me it is about 7.5gpp.with my slower bows.