Originally posted by 7 Lakes:
I went into a bow shop last week and watched the owner weigh a recurve. He secured the bow with the string downward. Hooked a 4 pound scale to the string and with a pulley hooked to the bottom hook of the scale pulled it to the 28" mark.
He did not take into account the 4 pound weight of the scale or that the 28" mark was used for all bows.
This man is a (un)professional that everyone in that county counts on to set up their bow. After talking with him a bit I discovered he's convinced all the arrow charts are off 5#.
Mike,
"Adjusting" the weight for the mass weight of the scale or the mass weight of the bow is a common myth that a lot of professional bowyers get sucked into believing...but think about it. In the situation you described, when the guy hooked the scale onto the string, the scale's physical mass pulled on the bowstring did it not? If so, then that weight should be included (which it is) and therefore should NOT be adjusted for. In the above situation, the scale is "drawing" some weight. Don't get me wrong, getting sucked into this myth this does not mean that the bows made by bowyers that made this mistake are not good bows. Although those bows will be incorrectly marked in terms of pull weight, many of those bows may very well be excellent bows. It only means those bowyers fell into confusion from a VERY COMMON MYTH that one should subtract the weight of the scale (if the bow is on top) or the weight of the bow (if the scale is one top) from the pull weight reported...when in fact they should READ IT AS THE SCALE REPORTS IT.
Here is why...
if the weight of the scale (or the weight of the bow if the scale is pulling upwards) is being supported/held by the bowstring, then it is flexing the limbs...and therefore it should be included. As long as the scale is calibrated, no adjustment should be made to the scale's reading. It sounds like that guy did it right...except for maybe the 28" mark thing. If he was using a block to hold the grip, the only variation he would have with that method would be variation in the depth of the grip/throat on the belly side of the bow to the backside of the bow...as throat depth varies from one design of bow to another (and to a lesser degree even grip size). Which is why draw length should be measured with a nocked measuring arrow when determining pull weight.
JamesV,
I use the same method that an archer uses to measure their draw length...and measure to the back of the bow on the outside of the arrow rest. I use a marked arrow to do that.