Primitive Archer

Main Discussion Area => Bows => Topic started by: PAHunter on March 14, 2014, 01:14:34 pm

Title: Selfbow FPS?
Post by: PAHunter on March 14, 2014, 01:14:34 pm
What do you feel is an average and very good FPS for a selfbow shooting a 10gr per pound DW arrow?  For example would you agree with the figures below?
thanks!
Title: Re: Selfbow FPS?
Post by: Joec123able on March 14, 2014, 02:47:29 pm
Well speed is something I don't care much about but in my head I would think they should all average around the same speed but there's so many factors that go along with speed that I dont know lol
Title: Re: Selfbow FPS?
Post by: Badger on March 14, 2014, 03:12:18 pm
    I agree with the 50# listed but feel they should all shoot the same if you raise the arrow weight. If they were all shooting 500 grain arrows your chart would be closer.
Title: Re: Selfbow FPS?
Post by: Marc St Louis on March 14, 2014, 03:14:54 pm
I've modified your post to show what it would be
Title: Re: Selfbow FPS?
Post by: PAHunter on March 14, 2014, 03:32:38 pm
    I agree with the 50# listed but feel they should all shoot the same if you raise the arrow weight. If they were all shooting 500 grain arrows your chart would be closer.

Excellent, that makes FPS it a lot easier!  So a very good 50, 60, and 70 pound bow would shoot around the same 170ish FPS with a 10gr per inch arrow.  But they would generate different kenetic energy, for example:
50# bow may generate 32 # KE
60# bow may generate 38.5 # KE (+6.5)
70# bow may generate 45 # KE  (+ 13)

Thanks guys!
Title: Re: Selfbow FPS?
Post by: adb on March 14, 2014, 03:35:32 pm
Why are you considering KE? There's not enough velocity to make it relevant.
Title: Re: Selfbow FPS?
Post by: PAHunter on March 14, 2014, 03:44:49 pm
Why are you considering KE? There's not enough velocity to make it relevant.

I hear some archers discussing it yesterday and it made me wonder about selfbows.  I'm looking for a good way to compare the potential penetration of bows given different DW and FPS.  The goal would be to help answer questions such as:
How much more effective is a 60# bow over a 50# bow?
What kind of FPS should I be trying to get when hunting elk?
How heavey of an arrow should I be using?

Personal experience and opinions are great but I was looking for a more concrete measurement of effectivness.  I was not aware the KE was not a relevant measure when it comes to bows.  I'm just trying to enter the woods with confidence that my equipment will be effective.

I appreciate your advice!
Title: Re: Selfbow FPS?
Post by: Buckeye Guy on March 14, 2014, 03:56:55 pm
Not sure that I would have much confidence in a chart as compared to a few thousand years of testimony to the effectiveness of a self bow But not every bodies mind works like mine so I hope you find what you need  !
Many of the words you speak of have more to do with salesmanship and mind games than the ability to get the job done .

Rest assured self bows do and will get the job done .

Have fun !!
Guy
Title: Re: Selfbow FPS?
Post by: PEARL DRUMS on March 14, 2014, 04:11:11 pm
Well said you worthless ol' nut!
Title: Re: Selfbow FPS?
Post by: Pat B on March 14, 2014, 05:01:13 pm
I shot one of my selfbows through a chrono a few years ago and was so disappointed in the number I never did or desired to do it again. I can tell from the first shot if a bow is a shooter or a good shooter. Either one will work for hunting or target. It's up to us to get good with the bow we shoot. Once you learn the trajectory of your arrows and are consistent in your form and release a 130fps bow will kill whatever you're shooting just as dead.
Title: Re: Selfbow FPS?
Post by: PEARL DRUMS on March 14, 2014, 05:19:39 pm
Well said you..........!
Title: Re: Selfbow FPS?
Post by: 4dog on March 14, 2014, 05:22:34 pm
yeah im thinkin a few thousand years of success IS proof enough.
Title: Re: Selfbow FPS?
Post by: Fred Arnold on March 14, 2014, 05:28:05 pm
I presume when speaking of the arrows you meant 10 grains per pound and not per inch. I've never shot through a crono but like Pat says after shooting for so many years you automatically know if the bow has good speed or is sluggish. An old rule of thumb was adding 100 to the bows weight (ie a 45# bow at your draw shooting 145 fps was considered adequate.
Title: Re: Selfbow FPS?
Post by: adb on March 14, 2014, 06:42:30 pm
If you want to be effective in the bush hunting, you need to do 3 things: practice, practice and practice. Shot placement is everything in archery and how fast the arrow gets there is less important.
Title: Re: Selfbow FPS?
Post by: smoke on March 14, 2014, 07:06:20 pm
 FOC weighted arrows with sharp broadheads make a significant difference if you are concerned about penetration.  But I'll confess, speed with the right arrows sure make me feel good!
Title: Re: Selfbow FPS?
Post by: Joec123able on March 14, 2014, 07:09:43 pm
yeah im thinkin a few thousand years of success IS proof enough.

Yes but more then just a few thousand
Title: Re: Selfbow FPS?
Post by: PAHunter on March 14, 2014, 07:42:51 pm
First, thanks for all the input!  I have no doubt that primitive weapons are effective big game weapons.  If I did, I wouldn't be using one to hunt with and I probably wouldn't be alive as our ancestors would have starved.  And I can beleive that an average selfbow can still kill big game. 

But, certinally there is a range of efficiency/FPS that is more ideal for hunting various big game.  And making a beautiful bow is an amazing demonstration of patience and art.  However efficiency/FPS is another attribute of a bow that is very important to some.  For fun if nothing else.  It's an area that I would like to focus on and improve on.  That kind of measurable result is fun to me.  And if my bows shoot faster certinally they will be better hunters, which is my primary objective.
Title: Re: Selfbow FPS?
Post by: adb on March 14, 2014, 07:45:17 pm
If I'm shooting 3D then sure, I like arrow speed just like the next guy. But if I wanna kill any big game I want a heavy arrow.
Title: Re: Selfbow FPS?
Post by: Badger on March 14, 2014, 08:03:37 pm
   Pa, you never have to apologise or give a reason why you want to know how fast your bow is. Your reason for building bows is just as valid as the next guys reason. If you enjoy seeing what you can get out of a bow no one can tell you you are wrong for doing that. My hobby is flight shooting so I need to know how fast they shoot so I bring the right bow to a contest. Before that I just enjoyed seeing what I could get. Any reason you choose to build a bow is a valid reason if you are enjoying yourself.
Title: Re: Selfbow FPS?
Post by: Danzn Bar on March 14, 2014, 09:45:31 pm
I presume when speaking of the arrows you meant 10 grains per pound and not per inch. I've never shot through a crono but like Pat says after shooting for so many years you automatically know if the bow has good speed or is sluggish. An old rule of thumb was adding 100 to the bows weight (ie a 45# bow at your draw shooting 145 fps was considered adequate.

I agree, if your thinking fps.... 100 + bow draw weight at your draw is considered an adequate fps for that bow.
Title: Re: Selfbow FPS?
Post by: PAHunter on March 14, 2014, 09:50:31 pm
I presume when speaking of the arrows you meant 10 grains per pound and not per inch.

Yes, thanks for the correction!
Title: Re: Selfbow FPS?
Post by: Grandpa Bill on March 14, 2014, 10:13:27 pm
Is it time to bring up the "200 fps Challenge"?
Title: Re: Selfbow FPS?
Post by: Del the cat on March 15, 2014, 05:24:44 am
Is it time to bring up the "200 fps Challenge"?
That's one of my goals...
I've done the 100# and 300 yards
Del
Title: Re: Selfbow FPS?
Post by: Joec123able on March 15, 2014, 06:28:54 am
Is it time to bring up the "200 fps Challenge"?


Hmm that's a heck of a challenge for a self bow shooting 9 to10 gpp
Title: Re: Selfbow FPS?
Post by: Del the cat on March 15, 2014, 06:49:07 am
Is it time to bring up the "200 fps Challenge"?


Hmm that's a heck of a challenge for a self bow shooting 9 to10 gpp
I don't think you'll be able to go that high in gpp ans still make it... I'd be thinking more like 6gpp?
Del
Title: Re: Selfbow FPS?
Post by: Marc St Louis on March 15, 2014, 08:37:57 am
You can easily hit 200 fps with 6 GPP in fact I have hit 230 FPS with 6 GPP.  Hitting 200 FPS with 9 GPP is a possibilty
Title: Re: Selfbow FPS?
Post by: ohma2 on March 15, 2014, 10:15:02 am
Agree its not all about speed in a hunting situation.but a crono will show you so much more than just speed .as how consistent are you and your bow to.
Title: Re: Selfbow FPS?
Post by: PEARL DRUMS on March 15, 2014, 10:16:48 am
What I notice most about my bows, or look for most I should say. Is how the arrow acts from the time I release until it hits a target. I like strong flight from the start to finish, like a train cruising by. Some bows act as if they gain power or lose it during flight, while others seem to have it out of the gates and maintain it for 25 yards. Now whether or not that is speed or power, I don't know? But I like it, look for it, and build for it.
Title: Re: Selfbow FPS?
Post by: PatM on March 15, 2014, 10:29:35 am
That's your arrow matching the bow Pearlie, not the bow itself.
Title: Re: Selfbow FPS?
Post by: Eric Krewson on March 15, 2014, 10:41:26 am
At my minuscule 25" draw I was always disappointed with any of my selfbow crono results so I quit checking. I don't get complete pass throughs that often on deer, usually the arrow is hanging by the feathers on the off side and the deer fall dead pretty quickly.  I  guess I have enough FPS from my bows to get the job done. 
Title: Re: Selfbow FPS?
Post by: Sidewinder on March 15, 2014, 11:12:28 am
Considering that the chest cavity on a full grown buck only takes a few inches of penetration to get into the vitals I would think that a pass through is less important than making it in the right spot. Also if the broadhead is still in the vitals and is grinding around as he runs its kiling him every step he takes.
 FPS to me is something I can't even worry about. I'm such a novice bowyer that all I can hope for is that it draws smooth, balances well and hits where I'm looking. Danny
Title: Re: Selfbow FPS?
Post by: Badger on March 15, 2014, 11:28:03 am
  I would like to see the challenge 9 gr per pound for a backed bow and 8 grains per pound for a self bow. It might take a while to get 1/2 dozen guys on this list. I know some of Marks could hit it at 9 grains.

   Lots of guys on here making bows that I have know are fast bows, many of the same guys claim they don't care how fast the bow is which is fine. The reason they are making the style bows they are making is because some guy proved the effectiveness of these same designs using a chrono.
Title: Re: Selfbow FPS?
Post by: 4dog on March 15, 2014, 02:03:52 pm
that and a very good eye!!!   8)   ^^^^^^^
Title: Re: Selfbow FPS?
Post by: H Rhodes on March 15, 2014, 02:22:30 pm
I haven't been around a chrono for a while.  I am curious how fast some of my bows are.  I just am not curious enough to shell out the bucks for a chrono.  I know when I have one shooting like I want it to.  I make mine to hunt with and a bow being accurate, quiet and hard hitting is what I want.  I think there is some kind of formula for calculating fps based on how many yards a bow will shoot.  If anyone has the straight skinny on that I am interested.  Don't know what it means, but I have a couple of hickory bows that will shoot 500 (or a little over) grain arrows over two hundred yards.  One pulls 60 and the other around 55.  Wonder how fast they are really shooting?  I don't see anything wrong with you guys measuring these things and putting a little science to work on them.  Hell, if it wasn't for a bunch of fellows smarter than I am, who have put a lot of thought into bowmaking, there wouldn't be so many great bows getting built.       
Title: Re: Selfbow FPS?
Post by: Del the cat on March 15, 2014, 03:03:50 pm
I haven't been around a chrono for a while.  I am curious how fast some of my bows are.  I just am not curious enough to shell out the bucks for a chrono.  I know when I have one shooting like I want it to.  I make mine to hunt with and a bow being accurate, quiet and hard hitting is what I want.  I think there is some kind of formula for calculating fps based on how many yards a bow will shoot.  If anyone has the straight skinny on that I am interested.  Don't know what it means, but I have a couple of hickory bows that will shoot 500 (or a little over) grain arrows over two hundred yards.  One pulls 60 and the other around 55.  Wonder how fast they are really shooting?  I don't see anything wrong with you guys measuring these things and putting a little science to work on them.  Hell, if it wasn't for a bunch of fellows smarter than I am, who have put a lot of thought into bowmaking, there wouldn't be so many great bows getting built.       
That sounds a good distance to me for those draw weights and arrow mass. A huge amount depends on the arrow of course.
Del
Title: Re: Selfbow FPS?
Post by: H Rhodes on March 15, 2014, 03:52:46 pm
Del, those shots were made with aluminum arrows.  I haven't been able to achieve those results with my homemade arrows.   
Title: Re: Selfbow FPS?
Post by: mikekeswick on March 15, 2014, 06:50:28 pm
I like making fast bows (or at least trying!) >:D and I love my chrono  >:D 
I noticed the comment earlier about how our ancestors would have starved if bows hadn't been effective....what did we do before bows (and atl-atl's ;))?
Title: Re: Selfbow FPS?
Post by: PAHunter on March 15, 2014, 08:08:21 pm
what did we do before bows (and atl-atl's ;))?

Spears, sticks, and if you go back far enough flint rocks to scavenge off of others kills with.  But it's not legal to hunt with spears in my state for some reason.   :( :o
Title: Re: Selfbow FPS?
Post by: Fred Arnold on March 15, 2014, 08:28:51 pm
 ;D Probably afraid if they allowed spears that you guys would start running around neckad in the mountains :laugh:
Title: Re: Selfbow FPS?
Post by: Badger on March 15, 2014, 08:29:50 pm
  One of the guys in our group killed a rabbit at 60 yards with an atlatl. Little bit of luck but he is good.
Title: Re: Selfbow FPS?
Post by: Fred Arnold on March 15, 2014, 09:06:35 pm
Badger, I'd love to try an atlatl. Got an old 59 KS wallhanger that I've been thinking might make a pretty good speciman.
Title: Re: Selfbow FPS?
Post by: PAHunter on March 15, 2014, 09:18:29 pm
Badger, I'd love to try an atlatl. Got an old 59 KS wallhanger that I've been thinking might make a pretty good speciman.
Billy Burger recently posted an atlatl build along on his YouTube channel, primitivepathways.  Looks like fun!  I plan on giving it a try when I have some time.
Title: Re: Selfbow FPS?
Post by: Marc St Louis on March 16, 2014, 09:40:40 am
Del, those shots were made with aluminum arrows.  I haven't been able to achieve those results with my homemade arrows.

I bought a graphite arrow several years ago for testing purposes.  It had a small diameter and weighed about the same as my flight arrows but my arrows would out shoot it for distance even when I fletched it exactly the same as mine.
Title: Re: Selfbow FPS?
Post by: smoky#1 on March 16, 2014, 10:03:28 am
Spears, sticks, and if you go back far enough flint rocks to scavenge off of others kills with.  But it's not legal to hunt with spears in my state for some reason.   :( :o
[/quote]
it is now legal to hunt with a spear in Nebraska !
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 11:19:48 am
Keep in mind PAhunter is talking elk, not deer. That said, plenty of elk have been dropped with archery equipment drawing less than 50 lbs and shooting slower than 150 fps.  Like others have pointed out, it is all about shot placement.  I admit, I get hung up on the arrow speed myself, but when I do, it is usually because my mind is thinking about the next 3D shoot or next years Pope & young clout and wand competitions.  When I get thinking clear about hunting, I grab the heavy arrows.  Just flung some freshly fletched douglas fir arrows yesterday evening.  They weigh-in around 780 grns.  Great weight forward due to 190 grn points. Shot out of a 57 lb longbow.  I shot some of my 520 grain arrows (my go to arrows since last fall) before and after shooting the newly made up heavy arrows, and I re-learned why I love heavy arrows....despite the less flat trajectory I was dropping them into the vitals on the foam bear at 35-40 yards, whereas my light arrows were all over the place; over, under, front and back. Fast arrows seem more twitchy to me.  Heavy arrows are more forgiving to my release.  That and the heavy arrows are always much harder to pull from the target.    8) 

I am trained in the sciences too, and I used to put a lot of stock in numbers.  Just keep in mind where the numbers are coming from. 

I strive to make fast bows, but then shoot heavy arrows from them. 


Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 11:27:06 am
Back to your original question. Yes, you do impart more energy into the target from a heavier bow shooting 10 grn/# over a lighter bow shooting 10 grn/# , even though speed is constant.   E = mc2   duh!  ;D

My favorite example of why mass over speed matters for hunting is Dr. Ashby's account of the present day Papa New Guinea hunting large deer with 80# bamboo bows and 4,000 grn arrows!!!  Do a search for Ashby papa New Guinea arrows to find the downloadable pdf. 

Ashby judged the arrows to be flying no more than 100 fps.  These native hunters take deer at 30 yards with 4,000 grn arrows!
Title: Re: Selfbow FPS?
Post by: PatM on March 16, 2014, 12:07:38 pm
You have to wonder about hunters in NA going on about deer jumping the string and yet in New Guinea the deer wait for an arrow to cover 30 yards at 100fps.
  Not sure if it worth differentiating between a Deer and an Elk. They are all Deer.
Title: Re: Selfbow FPS?
Post by: half eye on March 16, 2014, 12:47:43 pm
What ? jumping the string is a result of untoward noise, and please correct me if I'm wrong but a 4,000 grain arrow from an 80# pound cant be very noisy as far as excess energy generated by shooting light weight arrows from heavy bows is. One is straining it's guts out, and the other is down to near dry-fire.....quiet is still better.
rich
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 12:48:26 pm
You have to wonder about hunters in NA going on about deer jumping the string and yet in New Guinea the deer wait for an arrow to cover 30 yards at 100fps.
  Not sure if it worth differentiating between a Deer and an Elk. They are all Deer.

The only difference is about 400 lbs and 1/4" hide thickness.  ;D 

The New Guinea have no problem because that 4,000 grn arrow quiets the bow down to nearly noiseless.  They stalk to within 30 yds in the wide open grasses and shoot the dear while it is looking right at them.  It seems their silent set-up does not alert the deer.  Just lobs a spear into their vitals.  ;D

Most NA bowhunters shoot really loud set-ups. 

Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 12:53:49 pm
half-eye beat me to it.   :)
Title: Re: Selfbow FPS?
Post by: PatM on March 16, 2014, 01:04:40 pm
Is it really quiet to a deer though or simply a less threatening sound?
 The "Deer" of New Guinea are  more closely related to the NA Wapiti in at least one case. All are introduced species. My point is that the Deer versus Elk size difference is very blurry depending on what type of Deer we are talking about and the age of the animal.
 A Sika Deer or Red Deer are cousins to our Elk.
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 02:23:29 pm
Is it really quiet to a deer though or simply a less threatening sound?
 The "Deer" of New Guinea are  more closely related to the NA Wapiti in at least one case. All are introduced species. My point is that the Deer versus Elk size difference is very blurry depending on what type of Deer we are talking about and the age of the animal.
 A Sika Deer or Red Deer are cousins to our Elk.

Pat, PAhunter is preparing for an Elk hunt and appears to be shopping around for peace of mind that his gear will get the job done  ;).  Others were making reference to pass-troughs on whitetail deer. Not sure stories of passthroughs on whitetails are going to give PAhunter, who has experience with elk,  the confidence he needs. That is all I was aiming at.   :)
Title: Re: Selfbow FPS?
Post by: Badger on March 16, 2014, 02:37:21 pm
  Several years ago I made a bow for a guy that he took on one of those canned hunts for a cow buffalo. She was almost 700#. The bow was about 54# and just slightly reflexed, 500 grain arrow. I don't know if he got double lung or not but he said it coughed up a lot of blood as soon as he hit it and it ran about 100 yards.
Title: Re: Selfbow FPS?
Post by: PatM on March 16, 2014, 02:51:00 pm

Pat, PAhunter is preparing for an Elk hunt and appears to be shopping around for peace of mind that his gear will get the job done  ;).  Others were making reference to pass-troughs on whitetail deer. Not sure stories of passthroughs on whitetails are going to give PAhunter, who has experience with elk,  the confidence he needs. That is all I was aiming at.   :)
  You can probably still find a bunch of guys that will argue that a bow that will allow pass through on a whitetail is good enough for Elk.
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 05:00:33 pm

Pat, PAhunter is preparing for an Elk hunt and appears to be shopping around for peace of mind that his gear will get the job done  ;).  Others were making reference to pass-troughs on whitetail deer. Not sure stories of passthroughs on whitetails are going to give PAhunter, who has experience with elk,  the confidence he needs. That is all I was aiming at.   :)
  You can probably still find a bunch of guys that will argue that a bow that will allow pass through on a whitetail is good enough for Elk.
I am sure you are right about that.  A 40 lb bow with a good weight arrow will work for elk, if you do your part.  I wasnt trying to argue it wont, just not sure PAhunter would find the conviction he needs from the deer pass-through testimonials, and wasnt sure if people understood he is gearing up for elk hunt. 
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 16, 2014, 05:44:05 pm
Why are you considering KE? There's not enough velocity to make it relevant.

I hear some archers discussing it yesterday and it made me wonder about selfbows.  I'm looking for a good way to compare the potential penetration of bows given different DW and FPS.  The goal would be to help answer questions such as:
How much more effective is a 60# bow over a 50# bow?
What kind of FPS should I be trying to get when hunting elk?
How heavey of an arrow should I be using?

Personal experience and opinions are great but I was looking for a more concrete measurement of effectivness.  I was not aware the KE was not a relevant measure when it comes to bows.  I'm just trying to enter the woods with confidence that my equipment will be effective.

I appreciate your advice!

I am not sure why KE would not be relevant, as Adb states..but hey I am no physician  ;D ;D

To answer your questions I would say the bow that you can shoot a good hunting weight arrow (10-13g/#) accurately is the most effective elk hunting weapon.   
Forget about arrow speed. 

And be sure to use a good cut on contact two blade broadhead.  Or a sharp stone  >:D
Title: Re: Selfbow FPS?
Post by: loefflerchuck on March 17, 2014, 01:05:24 am
How would you modify it for short bows with a short draw? Would the arrows be 17.8 grains less for every inch under 28" for 50# and so on? Lets be fair here. Not everyone shoots a 28' draw. Anybody have a better formula?
Title: Re: Selfbow FPS?
Post by: mikekeswick on March 17, 2014, 05:13:01 am
what did we do before bows (and atl-atl's ;))?

Spears, sticks, and if you go back far enough flint rocks to scavenge off of others kills with.  But it's not legal to hunt with spears in my state for some reason.   :( :o

Before projectile weapons we used a thing which is now known as persistance hunting. Run after your prey until it overheats and cannot carry on.
Title: Re: Selfbow FPS?
Post by: Del the cat on March 17, 2014, 08:08:20 am
what did we do before bows (and atl-atl's ;))?

Spears, sticks, and if you go back far enough flint rocks to scavenge off of others kills with.  But it's not legal to hunt with spears in my state for some reason.   :( :o

Before projectile weapons we used a thing which is now known as persistance hunting. Run after your prey until it overheats and cannot carry on.
I thought that was 'courting'  :-*
Del
Title: Re: Selfbow FPS?
Post by: Gsulfridge on March 17, 2014, 08:15:35 am
what did we do before bows (and atl-atl's ;))?

Spears, sticks, and if you go back far enough flint rocks to scavenge off of others kills with.  But it's not legal to hunt with spears in my state for some reason.   :( :o

Before projectile weapons we used a thing which is now known as persistance hunting. Run after your prey until it overheats and cannot carry on.
I thought that was 'courting'  :-*
Del
Ha ha ha!  Good one!!
Title: Re: Selfbow FPS?
Post by: Fred Arnold on March 17, 2014, 08:32:50 am
 ::) I can see where this might be heading.
Title: Re: Selfbow FPS?
Post by: George Tsoukalas on March 17, 2014, 10:36:59 am
E-MC squared is the formula that applies when matter (M) is converted to energy (E) as in a nuclear reaction. C is the speed of light squared (3 x 10 to the 8th meters/ second). Even Badger can't get an arrow to go that fast. :)

Applicable formulas:
Force = mass X acceleration  ... which is the one I favor...

Kinetic Energy= 1/2 mass x velocity squared

Sorry  as I do not know how to do superscripts on my mac.

Jawge
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 17, 2014, 02:30:51 pm
Good one Del  :laugh:

Like I said, I am no physician , but I see the equation as indication that an underlying universal law is that energy is a function of the relationship between mass and movement. 

I was wondering why Momentum is not used more when discussing arrow dynamics.  momentum = mass *velocity 
Is it not applicable?
Title: Re: Selfbow FPS?
Post by: adb on March 19, 2014, 10:56:56 am
Hey Carson... a physician is someone who cures the sick. A physicist is someone who studies physics... but I know you knew that, right?  ::) ;D
Title: Re: Selfbow FPS?
Post by: Carson (CMB) on March 19, 2014, 01:27:15 pm
adb, yeah sure, and next you tell me a physiologist is someone who cures the sick using physics   ;D ;D
Title: Re: Selfbow FPS?
Post by: adb on March 19, 2014, 03:13:17 pm
adb, yeah sure, and next you tell me a physiologist is someone who cures the sick using physics   ;D ;D

You got it brother! ::)
Title: Re: Selfbow FPS?
Post by: Swatch on March 20, 2014, 01:22:02 pm
Dr. Ed Ashby has been doing research on arrow penetration for about 2 decades now and his research will clearly answer many of the questions and theories being expressed here. You can find a presentation that he made to the Michigan Bowhunters at the Tuffhead broadhead site.  Dr. Ashby talks about momentum vs kinetic energy, showing that momentum is highly correlated to increased penetration, so the advice about heavy arrows is very good. Dr. Ashby shows a correlation between penetration and arrows that are above 650 grains. It would be very good to go through his entire presentation, including his presentation on the New Guinea people shooting the 4000 grain arrows, which by the way are not fletched, which further increases their quietness.

PAHunter, get David Petersen's book A Man Made of Elk, , He will clearly explain what it takes to get an elk with a self bow. He is what I would consider an authority on elk hunting in Colorado. For those deer hunters who have not taken elk with a bow, it is much different. Elk are harder to bring down. Shot placement, heavy arrows, and sharp broadheads are very important, as always! I got a cow elk last year and I went through much of the same mental exercise as PAHunter.
Title: Re: Selfbow FPS?
Post by: PAHunter on March 20, 2014, 02:10:34 pm
@Swatch: thanks much man!  I'll definitely check out Dr. Ed's research.  650gr wow!  The ones I'm planning on taking ATM are 550 but there is still time to reconsider that.  I just ordered David's book!  I've been looking for a good book to read.   
Title: Re: Selfbow FPS?
Post by: Pat B on March 20, 2014, 02:16:16 pm
550 gr arrow with a very sharp broadhead from a 55# bow should do what you need done if you do your part.   
Title: Re: Selfbow FPS?
Post by: Swatch on March 20, 2014, 02:47:16 pm
Let me know how you like the book. I am shooting arrows that average 602 grains with a +-4 grain range. I shoot 300 grain Tuffheads giving me about 30%  forward of center (FOC). The arrows fly great.  My bow is just over 50# @ 28.5" and I limit my range to <35 yards.
Title: Re: Selfbow FPS?
Post by: JW_Halverson on March 20, 2014, 02:53:25 pm
Ashby's fact-based data applies wonderfully with elk because his research is on larger game animals in Africa, not our thin skinned North American deer.  And there is great statistical value in his work because it encompasses not just a few animals taken by a few combinations of tackle, but it's measured in thousands upon thousands of game animals. 
Title: Re: Selfbow FPS?
Post by: PAHunter on March 20, 2014, 04:06:44 pm
I got a cow elk last year and I went through much of the same mental exercise as PAHunter.

Oh and congradulations!!  That must have been a great feeling!
Title: Re: Selfbow FPS?
Post by: Badger on March 20, 2014, 06:11:28 pm
Good one Del  :laugh:

Like I said, I am no physician , but I see the equation as indication that an underlying universal law is that energy is a function of the relationship between mass and movement. 

I was wondering why Momentum is not used more when discussing arrow dynamics.  momentum = mass *velocity 
Is it not applicable?

  Carson, momentum is used when discussing penetration. When discussing bow performance kinetic energy is used because it remains relatively constant within a normal arrow mass range. You can't do anything to change the kinetic energy but you can make adjustments to your arrow weight to increase momentum. In reality bows are also more efficient with heavier arrows even if they are a bit slower, they have more kinetic energy as well.
Title: Re: Selfbow FPS?
Post by: adb on March 20, 2014, 07:13:49 pm
550 gr arrow with a very sharp broadhead from a 55# bow should do what you need done if you do your part.

A big +1 on that.