Bow speed tests

[LeTuB]

I have completely tested several bows (mainly recurves) and the results are quite surprising...The speed test result shows that most of high end recurves produce similar speed when compared apples-to-apples.
I have a Pro-chrono and set of arrows from 400 to 700 grains, well certainly not matched to all bow weight but as the chrono is 3 feets beyond, it should not affect a lot the speed measurement.
The following graph shows the measured speed (at my draw length of 28") for various bows as a function of arrow mass in grain per pound (depending of the draw weight of each tested bow)
 
BWTFV66 : black widow TF V 58" 66#@28"
BT mono 61 : 1 piece Blacktail elite 62" 61#@28"
BT TD 61 : Take down Blacktail elite 60" 61#@28"
BD 60 : Border Black Douglas XP30 60" 60#@28"
Raven 60 : Checkmate Raven 52" 60#@28"
GP B 55: 1 pce Great Plains B model 60" 55#@28"
Rb TS 55: Robertson Tribal Styk 60" 55#@28"

Except the 52" Raven all bows produce between 175 and 180 fps when shot with 10 grains per pound arrows...

[Soilarch]

Honest question here.  

I'm not speed freak, but I am a "data" hound so I really enjoy this stuff.


Given the BW's and Raven's performance, and the fact that the GP and Styk do surpisingly well for being 5# ligher....are longer bows generally considered more efficient?

That might be a long accept rule-of-thumb in the trad community.  I don't know, but that's what I "see" when I look at the graph.

Let me edit this...many of the "eastern" designs destroy that theory.  I'm back at square at one.

All the same, thanks for posting!

[O.L. Adcock]

"Except the 52" Raven all bows produce between 175 and 180 fps when shot with 10 grains per pound arrows..."

Good stuff, you said only 5 fps between them? Yet your chart shows 10 or more at 10gr/lb. Or is that the Raven on the bottom? Even 5fps at 10gpp is the same as short drawing the better ones about 1.5" and matching the lower ones. Very noticeable. I'm really surprised the BD didn't show better then it did. Did they all have identical strings and silencers and were all the brace heights the same? Did all arrows fit the string the same? How did you control draw length?....O.L.

[O.L. Adcock]

Another question....Between 7gpp and 12, bows usually spread apart  more, being close at heavier weights and wider at the light. Keep in mind FPS is like RPM, it's the percentage in KE split that matters......O.L.

[LeTuB]

Well in fact the best performer is the Blacktail TD, as it is an older model, I shot it with a 15 strands B50 string...and it was as fast as the others using D97 strings. To my opinion, it is due to the fact that a 60" BT really starts to stack at 28" DL so it store a little bit more energy.
The border is an older model, a buddy has newer hex 4 limbs..I will measure them soon
For the moment, I shot the bows without controlling the DL,I make a mean over 5 shots (I know that it is the weak point of the procedure)..next step for me is building a hooter shooter clone.

[fleetus]

Also, it would be a good idea to actually measure the draw weight at 28" exactly.  Many bows are several pounds heavier or lighter than advertised.  So one of your 55# bows could actually be 58# and another one could be 52#.  You think they are both 55 when in fact there is a 6# difference between them.  Good stuff.  Look fwd to hearing about those Hex4's.

[O.L. Adcock]

Folks can see one of the basics of how bows work, in relation to mass force, distance, and time. Note that in doubling arrow mass (100% increase) you only lose 25% of your velocity. That factor of 4 is present in much of trying to understand how things work and why.

Another thing to look at LeTuB, you've got some lines crossing. They shouldn't cross. The best performing bow at 6gpp will also be at 12. That's a clue other factors are skewing the numbers....O.L.

[Mark Hedges]

Originally posted by O.L. Adcock:
Folks can see one of the basics of how bows work, in relation to mass force, distance, and time. Note that in doubling arrow mass (100% increase) you only lose 25% of your velocity. That factor of 4 is present in much of trying to understand how things work and why.

This is absolutely true but a 25% reduction in speed is huge.  If you were shooting 180 FPS you would drop down to 135 FPS.  This translates to being 18 inches low at only 20 yards.

Mark

[O.L. Adcock]

"This is absolutely true but a 25% reduction in speed is huge."

Didn't say it wasn't, the point was it shows a 10 or 20% (8gpp to 10, or 10 to 12) change in arrow mass is not a very large velocity change....O.L.