mez

Art, all good points, especially about having identical momentum and changing KE, I wondered about that also. To his credit, many of the variables you mention he did take into consideration. He shot each arrow ten times and took an average of the ten. Every shot was through a chronograph at the exact same distance. I believe the same bow was used and each arrow tuned to the bow before testing. For the momentum I believe it was 300gr and 600gr, used aluminum, same length one was 22 something the other 22 also but thicker walled so the arrows would be the same diameter. Gees, I can' t remember all of the gory details. I' ll look tonight and get all the stats, you should buy a copy so you can read it. Still no statistics though, is it signifigant, it is very easy to look at raw numbers and draw conclusions but you can' t draw any real conclusions without proving statistical signifigance. Like you said Art, they publish a bunch of numbers people will take as gospel and truthfully no one knows if they mean anything at all.

Arthur P

Okay, there' s another problem. I don' t know how he got a 300 grain aluminum and a 600 grain aluminum, both 22XX series and both spined correctly for a 50 pound draw. The lightest 22XX series is the 2212 X7. Maybe with a lightweight nibb point and 1" feathers? A 2219 XX75, even a full length 2216, will make 600 grains easy with a 125 gn field point and 5" vanes. But there is a HUGE problem with spine issues, different aluminum alloys and there cannot be any similarity at all in fletching style or point.

Thinking out loud here. If I do cut and paste a letter to the editor, it' s going to be a wooly booger! I' ll hit Wally World after tonight' s football game and see if they' ve got a copy. This is starting to really sound like an interesting farce.

JeffB

Dave Holt performed the same exact test years and years ago and wrote it up in his book (circa 1990), unfortunately the name escapes me at the moment.

I have seen it reprinted in Bowhunter mag a couple of times since.

This may be just another re-print w/ some new pictures. I haven' t seen it this time so I cannot say.

Nic Barca

Penetration is no thing to worry about because a 45 pound-plus bow with a sharp broadhead (no matter if it' s fixed or expandible) is gonna pass completely though the chest cavity provided you hit no hard bones. If you happen do hit the shoulder blade or spine, it doen' t matter if your bow is 40 or 80 pounds, your not likely to get a perfect pass through. ...I don' t know, I could be wrong on that. I saw my friend' s 70 pound bow stick an inch in a goats shoulder just like my little bow has. I also saw a 80 lb recurve go right through both shoulder blade and through both lungs somehow. I also saw my little 35 pound bow shatter right through a shoulder and kill a goat. Fluke occurence maybe.

But penetration is not very important. Shot placement and sharp broadheads are what matters most. Not speed, not penetration, or noise.

I think the sharpness of the broadhead is the most important part of penetration. I' ve been lazy before and shot animals with very dull blades. They do not penetrate or kill very well. There are also little things that can hamper penetration, like fishtailing, which can cause your arrow to hit somewhat sideways on the side of an animal.

...Ok, later.

Arthur P

You' re right, Nic. Top to bottom, you' re right. I guess most of us accept it as given that people will make good equipment choices and that they will use sharp broadheads. That leaves this momentum/KE stuff to argue about. And there shouldn' t even be an argument.

Didn' t find a copy of the magazine last night but I did run across my ancient copy of ' Balanced Bowhunting' . Never noticed it before, but Holt was turning into a light arrow advocate even then! Since I still haven' t seen this version of Holt' s article, I' ll reserve further comment on specifics. But in general...

The worst part about this KE/penetration baloney is it' s based on NOTHING but unsubtantiated opinion, backed by poorly designed ' experiments' that are basically geared toward proving a prejudice in favor of light, fast arrows (Holt' s or a goodly smattering of other such ' tests' ). I' d even go so far as to say it' s based a good bit on snobbery.

When you really dig into things though, you can easily see that it' s all smoke and mirrors. Just a cursory glance at Newton' s Three Laws of Motion will tell you a good bit. Kinetic energy isn' t even mentioned. Force, inertia, momentum, acceleration, velocity... These are all there. Where is KE if it' s so all fired important?

What really bugs the crap out of me about this kinetic energy fixation is it sets up the anti' s for an attack. If they can take one of those infamous minimum KE charts that are floating around, they can argue, in court, that someone MUST have 40 ft lbs minimum of KE for hunting deer or similar size game. We could not defend against it because they would be using OUR own information! Then they can get a lot of perfectly capable equipment banned. Like stickbows drawing under 50 pounds. Even some folks shooting compounds that draw less than 50 pounds, especially women and children with their shorter draws, would be cut out.

Surely I' m not the only one with enough brain power to see the potential for threat in this!!

hdsanders

How do you calculate momentum? What is considered good?

Thanks

Rangeball

Arrow weight (in grains) X Feet Per Second % 225,200 = momentum

Dr. Ashton' s study showed that the chance of a killing shot when encountering bone increased 80% when momentum was at .57 or above...

Of course, this was for very large african game... how much is the minimum to yield similar results on whitetails is the million dollar question.

Art, Doesn' t Holt' s argument prove that a heavier arrow is more preferable to a lighter arrow, as the heavier one will always have a higher level of KE for a given bow?

mez

Ok Arthur I brought the magazine to work, here goes for the momentum test:
1. 2219 and 2213 cut to same length
2. 5 inch feathers left helical
3. 2219 @ 600 gr 2213 @ 400gr does not specify how this was done, only that
weights were adjusted
4. Velocity calculated to give same KE for both shafts
5. Draw weight changed and bow retuned for both arrows
6. Paper tune each arrow prior to testing at the distance test was conducted, 16
yards, chrony 1 yard in front of test material.
7. ethafoam and styrofoam used because of homogenous nature
8. each arrrow shot 9 times, velocity and penetration recorded
The results are as follows:
Ethafoam
400 gr arrow, 128 gr bullet point, velocity 244.8, KE 53.28,
Penetration 12 1/32 in

600 gr arrow, 128 gr bullet point, velocity 201, KE 53.84,
Penetration 11 15/16

Styrofoam
400 gr arrow penetration 13 3/16

600 gr arrow penetration 13 1/16

His conclusion:
" Data from test 5 and 6 strongly support the theory that kinetic energy, not momentum, is the dominant factor controlling arrow penetration, all other variables being equal. As a reminder, professional engineer Norb Mullaney addressed this same question with a different testing format. His test data support the conclusion that kinetic energy is the primary factor cotrolling penetration when all other variables are equal."

Arthur P

Well, I don' t trust his numbers ' cuz something is plain fishy.

No problem with a 600 grain 2219 with a 128 grain point. That' s simple. Cut it 30" long, 4" vanes and a glue on nock and you' re there. You' d have an FOC a shade under 9%.

Where I think he' s full of meadow muffins is with the 400 grain arrow. The only way he can get a 2213 down to 400 grains with a 128 grain point is by cutting it to 23" and using 2" feathers. Such an arrow would have an FOC of 15%.

The 2219 would be spined for a bow from 45 pounds on the low end to 60 pounds on the high end. A 23" 2213 would spine out somewhere around 100 pounds.

I don' t care how much adjusting you do, the same bow would not shoot both those arrows with anywhere near the same efficiency. Especially considering you' d be shooting the 2213 off a pretty healthy overdraw!

So, even if he did get the weights he claims, and got the speeds adjusted to give equal KE, with an 18% difference in momentum (.4348 vs .5355)... he' s got a 40% difference in FOC! Couldn' t someone just as easily say he proved that 40% HIGHER FOC gives as much penetration benefit as an additional 18% in momentum?

That' s something else he ' proved' without intending to: A heavy arrow at the same KE (at less draw weight) will penetrate as well as a lighter arrow.

He also might have proved that a short, light, incredibly overspined arrow might penetrate every bit as well as long heavy arrow at the prescribed spine.

Or he might have proved that an arrow with 2" feathers will penetrate as well as an arrow with 4" vanes.

Or he might have proved an overdraw arrow will penetrate as well as a full length arrow.

I have great respect for Dave Holt but I don' t buy into everything he says. IMO, he set out to prove a pet theory and so he did what he had to do to ' prove' it. Proven, at least, to those who don' t question the methods. He left too many variables wide open and unanswered.


And then, even if you account for all the variables, one question remains to be answered... Does penetration in styrofoam or ethafoam correlate in any way whatsoever to how arrows will penetrate in actual flesh? I think NOT.

corey006

If you are talking Whitetails I think you guys are getting carried away. I simply does not take that much energy to pass threw them. You DO NOT need heavy arrows either. The only advantage to a heavy arrow is a QUIETER BOW and MORE forgiving arrow flight.

I was told that my arrows were too light for Moose (380gr) and I was asking for trouble. Well I arrowed a BIG bull Friday evening and achieved a pass threw right behind his shoulder. It was at point blank range(6 yards) so that definitely helped but I think it would still have done the same at 30-40 yards.

I not even sure what speed my bow shoots at I think around 270 fps so My KE would be right around 60 ft lbs...