Weight vs Speed = Penetration ?

[Don Stokes]

If we were trying to penetrate animals with blunts, the energy figures would be very pertinent. With a cut-to-tip broadhead, arrow stability and broadhead sharpness become the more important factors.

[chopx2]

If you read the Ashby articles on here you will see that KINETIC energy DOES NOT PREDICT penetration. And the complete physics analysis proves it.

What the compound shooters and the industry that supports them has done is create a myth to sell product.

Speed will only increase penetration if mass (arrow weight) stays the same. This results in a momentum increase (speed is not squared). Of course you must keep perfect flight the same. Weight does not change at impact, but speed decreases rapidly. So the more momentum is made up of in speed the less it will penetrate because retained energy is much less than the the same impact momentum achieved through higher weight and less speed.

Using the bowling ball example. Throwing the bowling ball harder will cause more damage assuming identical impact angle and placement. Dropping down to a softball so it will go faster actually reduces the damage. That is where fact gets confused with fiction.

Hope that makes sense when you read it...lol

[fredhill]

i have never understood KE nonsence when talking about archery equipment.

[ozy clint]

sounds like you are ready to go eugene. now comes the hard part....getting access to buffulo. i wish i could have helped you out. good luck.

[ArrowCrester]

ditto !!! to you Ragnarok Forge…….      

[ArrowCrester]

AND ditto to You too GRAPES !!!!!!              

[Rattus58]

Originally posted by Ragnarok Forge:
fentirger.

Yes, KE decreases with increased arrow weight out of the same bow. The KE has velocity squared as a factor which pumps up the numbers based on velocity.  Increased arrow weight out of the same bow means decreased velocity = decreased KE.

[Rattus58]

grains   450
speed   220
KE   48.35164835
Momentum   0.43956044
   
   
grains   500
speed   200
KE   44.4000444
Momentum   0.444000444
   
   
grains   550
speed   180
KE   39.56043956
Momentum   0.43956044
   
   
grains   600
speed   160
KE   34.0992341
Momentum   0.426240426

I don't consider KE in anything I do as it to me is irrelevent. KE might get the arrow to the hide, but it is momentum that will finish the job.

The point of this illustration, is that the last value, 600 grain arrow at 160 is exceeded by my 45# Dorado, which some say is more like 50, or at my 31" more like maybe 55-60 some say... but the point is, but anyone here will attest to the fact that there is little out there that will not drop to this formula.

Just as an aside, I've been using 700 grain arrows and get 170 fps minimum from the Dorado with them and result goes up from what we have here.

Point of all of this, is momentum carries the arrow, and reduced speeds is no penalty.

grains   700
speed   170
KE   44.91064491
Momentum   0.528360528

Much Aloha...  :cool:

[hybridbow hunter]

Rattus58, from which bow did you get those numbers?
I don't know why so many archers still believe that joke "KE is decreasing with arrow weight"
Ragnarok, your assessment is absolutely wrong.
From most of bows, traditional AND compounds, from same bow shot at the same drawlenght with same release, both KE and Momentum will increase. BECAUSE DYNAMIC EFFICIENCY OF THE BOW INCREASE WITH ARROW WEIGHT. Past 13 to 15gpp according to the bow design, that increase will indeed be minor but still significant.

[Rattus58]

Hi Hybrid... the only number that is mine is the last one, 700 grains with a 45# Dorado... People tell me that the Dorado could be heavier but I don't know. I have a 31" draw, so it's subjective, but I do have a chrony that is consistent in readings so this is what I use when I shoot...

That said.... KE has to go up with an arrow weight given the ratio of weight to speed.

Weight can provide a diminishing return but speed has to reduce fairly dramatically along with weight increase being small.

grains   450
speed   220
KE   48.35164835
Momentum   0.43956044
   
   
grains   500
speed   200
KE   44.4000444
Momentum   0.444000444
   
   
grains   500
speed   180
KE   35.96403596
Momentum   0.3996004

Much Aloha...  :cool:

[Rattus58]

Might add, momentum again is the driver of the arrow in game, KE gets it there but become irrelevant once the points hits the hide.

Aloha...  :cool:

[slivrslingr]

This is interesting stuff, physics has always been a little difficult for me, but this helps.  That being said, sharp broadheads, perfectly tuned arrows, and proper shot placement kills game, not math.

[Rattus58]

Precisely.....

Aloha...  :cool:

[hybridbow hunter]

i tested extensively my bows in order to determine realistic performance measure before my trip to South africa and... for the fun of archery too !  :
i was shooting seated on the rinehart target my four hybrid bows with 4 arrows through a chrono with a checked draw length @ 31" BUT the shot was done to hit the "vitals" of the target # 11 yrds and valid only if so.
All arrows were tuned rather good for the shot distance with each bow (of course not "perfect" with all...) and were really made to hunt with high penetrating power with point weight (insert+BH) ranging from 280 gr to 325 gr

     


     

     

     


Those are the numbers, and as you see, with no exception from the same bow/archer KE increase with arrow weight (and of course momentum)

Guys, when you shoot a bow, if you make well tuned arrows, there is no way you loose "work" of the arrow when increasing the weight


Morrisson (61,1 # @ 31) :
878 gr (14,37 gpp) / 162 fps/ KE 51,2
735 gr (12,02 gpp) / 175 fps/ KE 49,99
682 gr (11,16 gpp) / 178 fps/ KE 47,99
619 gr (10,13 gpp) / 186 fps/ KE 47,56

Fedora (62, 8 # @ 31):
878 gr (13,98 gpp) / 165 fps/ KE 53,09
735 gr (11,70 gpp) / 179 fps/ KE 52,31
682 gr (10,86 gpp) / 184 fps/ KE 51,28
619 gr (9,86 gpp) / 190 fps/ KE 49,63

Fedora (56,9# @ 31):
878 gr (15,46 gpp) / 161 fps/ KE 50,55
735 gr (12,94 gpp) / 173 fps/ KE 48,85
682 gr (12,00 gpp) / 178 fps/ KE 47,99
619 gr (10,90 gpp) / 185 fps/ KE 47,05

Cari Bow (59,4 @ à 31):
878 gr (14,78 gpp ) / 161 fps/ KE 50,55
735 gr (12,37 gpp) / 174 fps/ KE 49,42
682 gr (11,48 gpp) / 180 fps/ KE 49,08
619 gr (10,42 gpp) / 188 fps/ KE 48,59

[hybridbow hunter]

Finally for my african trip i took my Fedora 57# and my cari bow 59# and made a 675 grain arrow (with 320 gr up front) flying perfectly for me up to 30 yards with the BH.
And that worked quite ok if you wanna look there:    http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=27;t=000317

[Andy Cooper]

Did you consider hunting the buffalo?

[hybridbow hunter]

I wish to hunt buffalo ! and hopefully i will do it in a couple of years but not in South Africa as my will for buffalo is a more free range hunt.
My set up for that hunt would be the Fedora 63# and the 735 gr arrow with 325 gr in front which indeed was the "perfect" arrow for that bow & set of limbs. and  would switch from 3 blades large broadheads to 2 blades standard width.

[Rattus58]

Originally posted by hybridbow hunter:
i tested extensively my bows in order to determine realistic performance measure before my trip to South africa and... for the fun of archery too !  :
i was shooting seated on the rinehart target my four hybrid bows with 4 arrows through a chrono with a checked draw length @ 31" BUT the shot was done to hit the "vitals" of the target # 11 yrds and valid only if so.
All arrows were tuned rather good for the shot distance with each bow (of course not "perfect" with all...) and were really made to hunt with high penetrating power with point weight (inert+BH) ranging from 280 gr to 325 gr

     


     

     

   


Those are the numbers, and as you see, with no exception from the same bow/archer KE increase with arrow weight (and of course momenum)

Guys, when you shoot a bow, if you make well tuned arrows, there is no way you loose "work" of the arrow when increasing the weight


Morrisson (61,1 # @ 31) :
878 gr (14,37 gpp) / 162 fps/ KE 51,2
735 gr (12,02 gpp) / 175 fps/ KE 49,99
682 gr (11,16 gpp) / 178 fps/ KE 47,99
619 gr (10,13 gpp) / 186 fps/ KE 47,56

Fedora (62, 8 # @ 31):
878 gr (13,98 gpp) / 165 fps/ KE 53,09
735 gr (11,70 gpp) / 179 fps/ KE 52,31
682 gr (10,86 gpp) / 184 fps/ KE 51,28
619 gr (9,86 gpp) / 190 fps/ KE 49,63

Fedora (56,9# @ 31):
878 gr (15,46 gpp) / 161 fps/ KE 50,55
735 gr (12,94 gpp) / 173 fps/ KE 48,85
682 gr (12,00 gpp) / 178 fps/ KE 47,99
619 gr (10,90 gpp) / 185 fps/ KE 47,05

Cari Bow (59,4 @ à 31):
878 gr (14,78 gpp ) / 161 fps/ KE 50,55
735 gr (12,37 gpp) / 174 fps/ KE 49,42
682 gr (11,48 gpp) / 180 fps/ KE 49,08
619 gr (10,42 gpp) / 188 fps/ KE 48,59

Beautiful Bows...  

Aloha...  :cool:

[Kip l Hoffman]

I spent 2 summers shooting my osage orange recurve through a chronograph from 10 yards out to 40 yards.  All arrows were woodies of different species ranging from POC to Hickory.  All arrows were spined properly and all arrows flew very well.  I was mostly testing to see if the different tapers on a shaft made any difference in velocity at hunting ranges.  They do not.  The arrow speed at 40 yards is the same no matter how the shaft is tapered.  All arrows with in 10 grains of each other shot the same speed no matter the taper or the wood.  I suspect that a barrel tapered shaft shot a bit further at 400 yards than a straight tapered shaft.  If it didn't then the armies of old wouldn't have gone to the expense to barrel taper shafts.  When I put the E=MCsquared conversion formula to the grain weight of arrows, my self bows were most efficient at 11 grains per pound of bow weight.  I.E., a 65# bow shot most efficiently with a 714 grain arrow.
With out a heck of alot of balistic jelli i think this is the best method of determening what shaft to shoot.

[stickbowhntr]

good read.