Heavier Bow Performance Expectations

[Bayou Ben]

I feel I have a pretty good gauge of what's good performance wise with 50 lb bows.  Should the expectations be the same for let's say a 65 lb bow? 
So it should shoot 650 grain arrow at 150 fps average, 170 fps good, and 180+fps excellent?  Or should the expectations be curved for a heavier bow at 10 gpp?
It seems that it would be harder to build a 65 lb bow shooting a 650 grain arrow 180 fps than it would be to build a 50 lb bow shooting a 500 grain arrow 180 fps. 

[bradsmith2010]

I think it is more difficult,, but there is no curve formula that I know of,, I just do my best,,

[Stick Bender]

Well there is only one way to find out    but I look at it a little different in terms of 10 gpp my standard hunting arrow is 550 grain weather I'm shooting a 48lb or 58lb & the heavier bows defiantly put some FPS on a lighter arrow I bumped up my normal draw weight by 10 lbs this year buy default with the bow I'm shooting & when I got back to the lighter bows they seem like there slower now even though there not ! 

[Badger]

  If you don't underbuild them they will perform just like the lighter bows with the same weight per pound arrows. I built a guy a hickory bow at 92# and he was hitting 176 fps with a 900 grain arrow. I have machine tested elbs well into the hundred pound plus and most of them are hitting in the low 170's which I consider very good for elbs or any other bow for that matter.

[bradsmith2010]

thanks for chiming in STeve,, that is fascinating,,and informative,,

[Bayou Ben]

Brad, yeah I'm with you.  I just would like to know where to set my goals/expectations.

I was actually thinking about that bow Steve when I was writing this, if it's the same one you mention in TBB.  Now that arrow has some KE!

I've made 2 over 60 lbs, and neither one is up to par with my better 50 #ers, so I guess I need to design them better, and tiller them better.

[Selfbowman]

Ben if the heavier bow  took more set that's where your loss is most likely. That's where I struggle with the heavier bows. Don't build many either. Arvin

[Del the cat]

A heavier bow will give more speed... but double the poundage won't double the speed.
The 10gpp thing isn't really a fair comparison if you are measuring speed.
Multiple speed x arrow weight and that will show the difference in power/momentum more.
(The deer doesn't know what poundage the bow was  )
There's no need for real heavy bow other than for the fun of 'em. A well made 45# will out perform a badly made 60#
Del

[Bayou Ben]

I guess that's my question Del, is 10 gpp a fair comparison when it comes to speed? 
According to Steve and his extensive testing, it is. 

I monitor KE and momentum of my hunting rig.  Speed and arrow weight are the only 2 variables in both equations, and if I want 10 gpp for hunting weight arrow, then the only other variable is speed. 

I'm in the thought/design stage of a elk hunting bow.  That's what prompted this question.  I won't take anything in the woods with me that I can't shoot accurately.  We aren't talking 120#'s or anything     

[Del the cat]

I s'pose what I'm really saying is that if you have  45# bow and 10gpp arrows then you build a 50# bow, you don't really need to make a whole new load of arrows... your existing ones will shoot just fine, be faster and have more momentum.
But, if you stepped up to 60#  from 45# you'd probably want heavier arrows for a smoother shot.
Del

[bradsmith2010]

I shot a buffalo with a 70# at 25 inch draw bow,, 800 grain arrow,, the arrow went all the way through,,
now that being said,,that was along time ago and the bow was slow by todays standards,,and had a heavy b50 string,, so what I learned from that, is,, that a well made 55#,, would shoot that same arrow the same speed,,,as my old slow bow,,
so if you make a good 55 to 60 # bow that shoots ,, 165 to 170 fps 10 gpp,, you would be good for elk,,
Im not saying a lighter bow would not work,, just saying in that range should do the job,,

[Badger]

Brad, my buddy killed a cow buffalo with a 50# I made him. He went about 100 yards not sure if he got the heart or just both lungs. She weight just under 700# nothing like the big bulls but still a pretty tough animal.

[bradsmith2010]

I can see that,,,for sure,, I am guessing your friends bow was shooting 170 fps,, thats about what my old bow was shooting a 500 grain arrow, even with the high draw weight,,, it was when I first started,, I just took the heaviest bow I had,, but it was not effecient at all,, that being said,, when you get a 500 grain arrow to that speed it is deadly,, not sure how fast the 800 grain arrow was going,, it looked like slow motion,, but just disappeared into the buffalo,,

[willie]

I monitor KE and momentum of my hunting rig.  Speed and arrow weight are the only 2 variables in both equations, and if I want 10 gpp for hunting weight arrow, then the only other variable is speed. 

BB
those formulas are two different ways of looking at performance. take your pick, as there have been many discussions about which is better.  most compound guys like speed and the primitive cultures seemed to favor mass, maybe more than 10GPP if the range is close.

[Bayou Ben]

Willie, yes I agree. 
That was just my way of saying I'm aware of the other things that affect arrow penetration.   
In my previous life  I shot an 80 lb compound that flung a 525 grain arrow 295 fps.  I would say that's speed and mass combined, although nowhere near 10 gpp. 
 
 
The one variable that I as the bowyer can change is how efficient I make the bow at a certain draw weight.  I'm not speed chasing really, I just want to build the best bow I can and have realistic expectations of where a good heavier bow should be. 

I have a pretty good idea of where I should be after reading these responses.  Thanks guys.