been playing with some arrows for my new bob lee recurve. with these limbs i'm pulling 66-67#. looks like two options will work. these are- 75/95 g/tip, 100gr insert, 240gr b/head, 5gr/" wt tube for 780gr 20% FOC. also- same combo except with 3gr/" wt tube for 730gr 23% FOC. target game could be anything from pigs, goats, deer, scrub bulls and buffs. what would you use? also, i've got a set of 53# limbs for the same bow with which i currently shoot 11.13gr/#. if i set up the 67# bow to shoot close to 11.13gr/# can i expect the the trajectories to be very close to the same? this would allow for quick change over between bows with less "sighting in".
Theoretically speaking, if you have identical limbs, say 50 & 60# for the same bow, they should shoot a propotionately identical arrow at the same speed.
ie. 500gn arrow from the 50# limbs = 180fps
600gn arrow from the 60# limbs should also be 180fps.
If you can match arrow weight to draw weight in this fashion, you shouldn't notice any trajectory difference between your light & heavy limbs. For that reason alone, Id go with the lighter arrow (11.06gr/# @ 66#) :) Normally I'd say the heavy, but 50gn really isn't that much extra.
i maybe changing my 53# setup(to extreme FOC) and if it shoots ok it will be running at 11.47gr/#. which is closer to the 11.73gr/# the 67# bow would be at with the 780gr arrow. just thought this might influence your answers. thanks.
Just inquisitive. If your weight tubes extend the length of the arrow, why would there be that much of a change in FOC? 3% is pretty much.
because a heavier wt tube creates a heavier shaft, the point weight would need to be greater to make it balance at the same spot. the lighter the shaft with a given point weight the greater the foc will be. the ultimate arrow would be one that has a light shaft but at the same time is very stiff so it could handle having huge point weights. imagine the mega foc! but you cant make an arrow stiff enough without enough material, which adds mass.
Agreed, but I didn't think there was enough difference in the weights to move it 3 pecentage points. Thought it might increase a percent or so. If I figure it right, the lighter arrow is about 50 grains lighter behind the balance point than is the heavier arrow. It's also about 12 grains lighter in front of the balance point. So it seems a difference of about 38 grains in back of the balance point is enough to tip the scale 3 percentage points.
Regardless, you have a good arrow either way. I'd lean toward using the lighter one with higher FOC.
maybe the weight difference behind the balance point is more critical because it has a longer lever with which it can do its thing? anyway i played around with wt tubes. now i've got it weighing in at 760gr (11.42gr/#, same as what my new setup should be for my other limbs) by putting 7" of 8gr/" tube up front with the remainder being 3gr/" tube. i'll see if it will tune.