• Registered: 2010-10-20
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Topic: graph

http://i183.photobucket.com/albums/x123/cuadrant/graficehwsorin.jpg?t=1324406824

Graph is based on empirical data (thick lines) and mathematical equations (thin lines) .

red: SMG long, marked 75,5 lbs @28
data:
draw 28” : force = 68,16 lbs, stored energy 99,23 joules
draw 29,5” : force = 74,92 lbs, stored energy 111,49 joules
draw 33” : force = 98,48 lbs, stored energy 145,69 joules



green: SMG standard, marked 70 lbs @28”
data:
draw 28” : force = 63,47 lbs, stored energy 90,53 joules
draw 29,5” : force = 70,31 lbs, stored energy 102,01 joules
drawe 33” : forta = 98,48 lbs, stored energy 134,69 joules

yellow: YMG standard, marked 65 lbs @ 28”
data:
draw 28” : force = 60,55 lbs, stored energy 84,08 joules
draw 29” : force = 64,86 lbs, stored energy 91,26 joules
draw 33” : force = 89,96 lbs,  stored energy 126,08 joules

brown: SMG long, marked 50 lbs @28”
data:
draw 28” : force = 47,05 lbs, stored energy 69,46 joules
draw 29” : force = 50,02 lbs, stored energy 75,04 joules
draw 33” : force = 72,97 lbs, stored energy 102,46 joules

mauve: SMG standard, marked 49 lbs @28”
data:
draw 28” : force = 46,67 lbs, stored energy 63,67 joules
draw 29” : force =  50,47 lbs, stored energy 69,24 joules
draw 33” : force = 73,22 lbs, stored energy 97,00 joules

blue: SMG standard, marked 22 lbs @28”
data:
draw 28” : force = 20,08 lbs, stored energy 29,69 joules
draw 29,5” : force =  22,41 lbs, stored energy 33,45 joules
draw 33” : force = 31,92 lbs, stored energy 44,32 joules
draw 35” : force = 42,64 lbs, stored energy 52,85 joules

Speeds will come soon. tongue

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  • Registered: 2010-10-22
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Re: graph

Thank you sir,

We needed this. Great information to have.

Kind regards,

Joseph

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3 Reply by WillScarlet (edited by WillScarlet 2011-12-20 23:56:50)

  • Registered: 2011-11-27
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Re: graph

Could someone give a cross-reference, joules to foot-pounds?    hmm 


Will

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  • Registered: 2011-04-13
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Re: graph

1 joule = 0.737562149 foot pounds

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  • Registered: 2011-04-13
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Re: graph

That's 107 lbs-ft energy for the long red SMG (horn belly) laminated bow!!!

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  • Registered: 2011-04-13
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Re: graph

Even the standard SMG manages 99 lbs-ft energy!

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7 Reply by Kanuck (edited by Kanuck 2011-12-21 04:17:05)

  • From: Medicine Hat, Alberta, Canada
  • Registered: 2011-12-06
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Re: graph

Ginni

Nice work.  Thanks for this information.  Are you measuring the draw length from the back of the bow or using ATA standards (distance to grip + 1.75")?  That may be part of the reason there seems to be a discrepancy between the marked draw weight and the measured draw weight.  It is amazing how much weight these bows gain the last 3.5-4" of draw - 25 lbs or more!!!!

Will Scarlet

The units used aren't so important as the shape of the curve to indicate the characteristics of the bow.  As for the stored energy, you have to know the speed and mass of the arrow to know how efficient the bow/arrow combination is.  No bow will be 100% efficient.  Besides, KE isn't a very good indication of the "power" of a particular arrow in terms of its effectiveness.

Kanuck

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  • Registered: 2010-10-20
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Re: graph

Draw-length is measured from belly to string, this should be from notch of arrow to base of the tip, for a longer point, with power flight is 1,5 cm from base ot the tip.

I have only some incomplete speed measurements, I have to do this more carefully.

If you want to know, for YMG marked 65@28, I got this (max speed, not average):


Easton Powerflight, 353 grains

draw length          draw weight         grains/lbs         speed          KE            stored energy             eficiency
     28”                     61,16 lbs                5,78              236 fps      59,28J               84,08J                    70,50%
     31”                     69,68 lbs                5,05              265 fps      74,75J               107,27J                  69,68%

I made this shooting with thumbring and I observed higher speeds with snap release, up to 15 fps, this is something I must to verify.


Peter, you are right, the 75,5 long SMG is semihorn, I forgot to mention.

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  • From: Medicine Hat, Alberta, Canada
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Re: graph

Ginni

Thankyou once again.  This is all very interesting.  The efficiencies are quite high for such a light arrow and, of course, the speeds are very impressive.

I am curious to know what the "natural" arrow mass would be for typical traditional Korean bamboo arrows.  I am guessing it will be between 400 and 600 grains for a full length 33" arrow.  At this mass, which is still quite light, velocities should be 180-220 fps, which is very good for a natural material bow and arrow.

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  • ~HUN~
  • ~HUN~
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Re: graph

Thanks for posting the information, Ginni.

The weight and density varies considerably with bamboo, with some similar looking shafts I've seen 100+gr difference.
I've made sets of arrows from 370gr - 550gr (finished arrows 35") I've previously cut some that were over 400gr as bare 32" shafts.

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  • Registered: 2010-10-20
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Re: graph

Mathematical approximation:
http://i873.photobucket.com/albums/ab296/storm_ro/FD_Hwarang.jpg

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  • Registered: 2011-11-27
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Re: graph

~HUN~ wrote:

Thanks for posting the information, Ginni.

The weight and density varies considerably with bamboo, with some similar looking shafts I've seen 100+gr difference.
I've made sets of arrows from 370gr - 550gr (finished arrows 35") I've previously cut some that were over 400gr as bare 32" shafts.

   
     Bamboo shafts can be had matched within 5# spines and  25 grains weight. Bought in bulk
they are less expensive than by the dozen. But.........they are only 33" long.

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  • Registered: 2011-11-27
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Re: graph

Kanuck wrote:
   " Besides, KE isn't a very good indication of the "power" of a particular arrow in terms of its effectiveness."


       True, in fact, as far as hunting goes, what the hunting archer is most interested in is penetration,(along with speed and trajectory)  Penetration is determined by momentum and
momentum = mass x velocity
        There is a mathmatical formula for finding momentum but I won't go into that, unless someone wants it, but from a practical standpoint I'm not sure whether one can really determine how efficient a bow/arrow combination is on "paper", except to find the speeds of differing weight arrows. You will still have to expeirment to find  which arrow your bow shoots
best for the different applications you intend (targets/small game/large game/etc.)

       Just my 2 cents.   cool

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  • Registered: 2011-04-13
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Re: graph

How many grains or grams are the field points?  265 fps is very respectable for a recurve.

ginni wrote:

Draw-length is measured from belly to string, this should be from notch of arrow to base of the tip, for a longer point, with power flight is 1,5 cm from base ot the tip.

I have only some incomplete speed measurements, I have to do this more carefully.

If you want to know, for YMG marked 65@28, I got this (max speed, not average):


Easton Powerflight, 353 grains

draw length          draw weight         grains/lbs         speed          KE            stored energy             eficiency
     28”                     61,16 lbs                5,78              236 fps      59,28J               84,08J                    70,50%
     31”                     69,68 lbs                5,05              265 fps      74,75J               107,27J                  69,68%

I made this shooting with thumbring and I observed higher speeds with snap release, up to 15 fps, this is something I must to verify.


Peter, you are right, the 75,5 long SMG is semihorn, I forgot to mention.

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  • Registered: 2011-04-13
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Re: graph

Eugen, can the long version of 75.5# SMG be drawn to 35" a few times without breaking?  There is no way a 70# standard (mid length) SMG can be drawn to 35".  I understand your second graph is a mathematical approximation.

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  • From: Medicine Hat, Alberta, Canada
  • Registered: 2011-12-06
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Re: graph

While the curves and the areas under the curves are interesting and impressive, if you draw a straight line from brace height to maximum draw length, you will see that part of the curve is above the line (which is good) and part is below the line (which is not so good).  On average, the area under the curve for the longest of draw lengths will be very similar to the straight line "curve" - basically no advantage over a self longbow in terms of energy storage.  However, because the limbs are so much lighter than the longbow, the arrow speed with light arrows is terrific.  With heavy arrows, the recurve will still do very well also but no better than the longbow of the same weight if it is designed correctly.

The "design" draw length will be where the maximum amount of curve is above a straight line - where the curve first touches the straight line or anywhere from 20 to 24" for these bows.  Obviously, these bows are designed to draw far beyond that but it is interesting to see how the curve compares to modern bows and especially those that are built to a specific design draw length.

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  • Registered: 2010-10-20
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Re: graph

http://i873.photobucket.com/albums/ab296/storm_ro/BhutanvsHwarang.png

Kanuck, above is the bhutanese bow, which is whitout doubt a high performance longbow (not so long tough).
The energy stored is lower than hwarang:
SMG semihorn @28 has 68,18 lbs and 99,23 J energy.
SMG short 70 lbs@28 has 63,47lbs and 90,53 J energy.
YMG short 65lbs@ 28 has 61,16 lbs and 84,98J energy.
Bhutanese bow @28 65,24 lbs and 87,52J energy.

That because no longbow have a straight line curve of D/W graph.
And if you want a long bow to draw to 33", it should be very long and heavy, not so efficient.

However, I put the bhutanese in the chrono and got this:
Easton  PowerFlight 353 grains @28:
Shooting with fingers, target style max.198 fps.
With snap technique I got max. 219 fps.
If we compare this with YMG who got 236 - target technique, same arrows, we can see the difference in efficiency. And YMG has less energy stored than buthanese bow at 28" draw.
I didnt tried with heavier arrows, Ill do that asap.

Peter, the 75lbs semihorn cannot be drawn to 35" safely. I must say the semihorn bow has a very big failure rate. As I know, here we got 10 bows and 6 has broken. Is a very pleasant bow to shot, but very unpleasant to break tongue
i have a long draw and I encouraged everybody to draw long, maybe this can be a problem. But the last who broke wasnt drawn longer than 31". Horn does not mix well with synthetic materials.

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  • From: Medicine Hat, Alberta, Canada
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Re: graph

Ginni

Thanks for the great information.  I'm not familiar with the Bhutanese longbow.  Is it a self bow of a single piece of wood or is it laminated - with or without fiberglass?  What is its length, nock to nock, when strung?   The brace height seems very low for a longbow and helps with the performance.  What sort of bowstring is on it?  198 fps is pretty darn good, even at 5.6 gpp.  I could never shoot any of my longbows with that light an arrow, unless I used an extremely light point. 

Kanuck

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  • Registered: 2010-10-15
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Re: graph

Kanuck wrote:

Ginni

Thanks for the great information.  I'm not familiar with the Bhutanese longbow.  Is it a self bow of a single piece of wood or is it laminated - with or without fiberglass?  What is its length, nock to nock, when strung?   The brace height seems very low for a longbow and helps with the performance.  What sort of bowstring is on it?  198 fps is pretty darn good, even at 5.6 gpp.  I could never shoot any of my longbows with that light an arrow, unless I used an extremely light point. 

Kanuck

They are two pieces of bamboo slats, overlapped at the grip, and bound.

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20 Reply by EM

  • EM
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  • Registered: 2011-12-18
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Re: graph

ginni wrote:

... the 75lbs semihorn cannot be drawn to 35" safely  ... I encouraged everybody to draw long ...

Hi Ginni,

very interesting data !

I'm interested in the Korean very long draw (draw hand far back on the shoulder) more than in the super strength of a bow. To perform this very long draw I would probably need to draw past 35" and remain under 50# [lets say 50#@36" for instance].

From your first graph we see that a standard version of SMG 22#@28" can be drawn to 36" and be under 50#.

Do you know if there are longer versions of these bows SMG or YMG that can also be drawn [50#@36"]  even more consistantly and safely (and without breaking)  ?

(where would one find the bowyer's description for these bows ?
I've only found Song Mu Gung's web site : it doesn't tell - english version - what is the maximum safe draw for the "jang gung" and only recommends 32" arrows).

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  • Registered: 2010-10-20
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Re: graph

EM, as you can see, the 22lbs bow have over 43 lbs at 35". Is not very efficient by comparison with the more stronger bows.
Any longer version of YMG or SMG can be drawn safely @35" if is not strong, but will stack. Storm have a regular length SMG marked 49@28 (mauve in the second graph) and he shot a long time with 89-90 cm length arrows.

http://img3.rajce.idnes.cz/d6/3/3610/3610079_4b8e3043b264a6c106c7e19e9915218f/images/P6265618.JPG

http://img3.rajce.idnes.cz/d6/3/3610/3610079_4b8e3043b264a6c106c7e19e9915218f/images/P6265623.JPG

For YMG bows you can contact Bluelake. The site is here http://www.goongdo.com/product/bow.php

http://www.goongdo.com/product/facility.php

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22 Reply by EM

  • EM
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Re: graph

ginni wrote:

  ... 22lbs bow have over 43 lbs at 35"


sorry for my error : 35", not 36"

ginni wrote:

   Storm have a regular length SMG marked 49@28 (mauve in the second graph) and he shot a long time with 89-90 cm length arrows


According to the mauve curve, Storm pulls near 100lbs if he uses the full length of his arrows ?!   I'll probably never have the strength for that, and will remain under 50lbs for ever  :-) 

ginni wrote:

  http://www.goongdo.com


Thanks for the links. And many thanks for making all the measurements for the bows and for sharing the results. As the bowyer's web site doesn't really show the properties of the bows [as far as I could understand from my browser's translation of Korean language :-) ] we are very fortunate that you make all the work !

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  • Registered: 2011-04-13
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Re: graph

Ginni, what's the draw weight of the 70# long-length YMG at 35"?

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  • Registered: 2011-04-13
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Re: graph

http://www.youtube.com/watch?v=Azmfi7en … ature=plcp

Wow, you guys are on TV!

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  • Registered: 2010-10-20
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Re: graph

I doubt it can be drawn to 35”. According to the graph it should be over 120 lbs.

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