Arrow/ bow weight and trajectory... Your thoughts?

[Al Kidner]

G'day all,

 Well just the other day I was out practice shooting in some sand dunes close by my place and the thought crossed my mind...

 If I shoot say a 63# recurve with an arrow weight of 10 grains per bow weight - that being 630 grains - and then, on another day shoot a 73# recurve with the same amount of arrow weight, 730 grains... If, all things being equal, and shooting well here... Should my arrows always have the same arch in trajectory ?

The reason I ask this is that I have always aimed at having just that, 10 grains per bow weight for all my arrows, both hunting and on the practice range. And it's only now that I have bumped up my arrow weight (Grizzlystiks with The big Grizzly BH's up front ) ... That I have noticed I need to adjust my shooting for these heavier arrows.

I may have already answered my own question and I am not very good with numbers as my brain has troubles with them so I thought I'd ask the smarter people of trad gang. In saying that.... I am pretty good at Crossfit...lol.

Cheers guys,


ak.

[katman]

IF all things are equal I would suspect very similar trajectory, However some bows are more efficient at transferring the energy to the arrow, heck same model from same bowyer will not be exactly the same. So probably not exactly same trajectory in this not so perfect world.

Thinking a little more very slight differences in arrow speed would probably not be noticed inside 20 yds.

[Michael Pfander]

My 2 cents.  If the bows are fairly close in efficiency then the greatest difference will be the result of knock point ht.  I have had this happen with my setups when everything is equal accept arrow diameter.
MAP

[LittleBen]

A lighter weight bow will shoot a few fps slower at the same gpp as a heavier weight bow, assuming all else is equal.

With that said, theres probably more variation in speed from one arrow to another (woodies at least) than there is from bow to bow. So I think keeping the same GPP will keep the same arc (not from a strict engineering sense but in the real world you wont be able to tell unless you're a shooting legend)

[Trumpkin the Dwarf]

I would wager that you either don't draw the heavier bow back as far, or the bow is less efficient.

[Friend]

With proper tuning, all other set-up factors equal and same inital velocities, you should expect no difference.

[flinthead]

Our club has a shooter that has won many state and several national championships. He gap shoots w/ 3 under[which is almost like shooting with a pin sight in the hands of a very accurate archer], and tells me with equally efficient bows there is not any difference in the arrow arc. He has owned  several Widows and everything is the same on most widows[same model] except the poundage.
My shooting is not accurate enough to say this positively, but this guy is a shooting machine so will go with his results. Thanks, Roy

[Benjy]

I would think that based on the fact that a heavier object is harder to slow down (Momentum), I would think that if both arrows left the bow  at the same speed , the heavier arrow would be faster at 40 yards than the lighter one.

The fletching would do a better job at slowing down the lighter arrow.

My thought would be, is the heavier bow pushing the heavier arrow at the same speed as the lighter setup at the bow? Since you are having to adjust your sight picture, I would say it is not...

These are just my thoughts and subject to be wrong! I have no idea how to do the math!   :D  

Benjy

[Orion]

Benjy is right about the heavier arrow carrying the speed longer, though it may not start out quite as fast as the lighter arrow/bow combination.  Of course, we're only talking a couple fps here at most.

If you shoot the same gpp on similar bows, the initial and downrange speed and trajectory difference will be so slight as to be unnoticeable at hunting ranges.

[Al Kidner]

Thanks guys for your input... And I must say, that was what I thought and my findings also, being the trajectory if I aim at having the same GPP on either bow.

ak.

[Nativestranger]

The heavier bow and arrow setup will be more efficient.

[old_goat2]

I have an ILF bow with two sets of limbs, one 45 and one 55 that are the same length and model etc, just different draw weight, to get the same speed out of the lighter limbs, I had to drop from 10gpp to 9gpp. You would have graph out the Force Draw Curve to know if the limbs were truly equal which I haven't done, so my findings are purely anecdotal

[Danny Rowan]

Al,

All of my bows are 55-60#. I shoot the same arrow out of all of them, AD Trad which are 11 gr per inch, 31" with 400gr up front so my total arrow weight is probably around 800 gr . I do not notice any difference out to 25 yards which is about as far as I would shoot at an animal. I do shoot regularly out to 40 yards in practice and again, no difference, I realize there is only 5# in difference and not the 10# you have, so that may be why my results are what they are. I do have a 53# bow coming so will have to see if the same arrow will work out of it, my guess is that it will but I may have to adjust my sight picture for that bow, we shall see.

[Friend]

Variable ballistic arrow claculators reveal there is no difference.

[Nativestranger]

The virtual moving mass of bow limbs/ string vs arrow mass is less on the heavier bow and arrow setup making it more efficient.

[Nativestranger]

The virtual moving mass of bow limbs/ string vs arrow mass is less on the heavier bow and arrow setup making it more efficient.