I have heard a long draw is a positive thing but don't know why. My bow is 65@29 but I am pulling 30.75 in. What is the difference between the 2.75 inches before 28 in. and after 28 in.?
Whats the big deal, if there is one, after 28 inches? :confused:
Poundage increases as does the length of the power stroke = faster arrow, so more energy.
Nothing magic. It's a good way to pick up extra speed/power...even if the draw-weight stayed the same.
It's a longer "powerstroke". The bow has more time to impart the same amount of energy...blah blah blah.
Longer is better, but not at the price of accuracy.
Its why my 825+gr (non-EFOC) arrow isn't too heavy out of my bows when it is drawn 32" inches...
long draw means more speed. More speed means more momentum.
hits like a ton of bricks.....
If you have two similar bows (length, design, etc) one drawn 50# @30" and one 50# @26", the bow drawn to 30" will store considerably more energy. Depending on the bow design, that same 26" draw would need to be around 60-65# to store the same amount of energy.
Short draw your bow by the same amount and you will see the difference.
SL
Nothing magic about the inches after 28". As stated, it's in the power stroke. If a bow has an 8" brace height, look at it this way:
Draw Power Stroke
25 1/4" 17 1/4"
28" 20"
30 3/4" 22 3/4"
That's an increased stroke of 5 1/2", or about 32% more than the 25 1/4" draw. If all else were equal, including the draw weight at each of the above draws, the longer power stroke would still impart more energy into the arrow. Of course in a particular bow you are also pulling more weight at the longer draw, adding force with the additional pounds as well.
Keep in mind, I don't know much about physics, and may not be explaining this in true scientific terms. That's just the way I understand it.
So...the increase in lbs. from 26 to 27 inches may be 3 lbs. versus maybe a 4 lb. increase from 29 to 30 inches because of a longer powerstroke?
A 50@28 bow will have 8% give/take less energy in the arrow than a 50@30 due to the power-stroke. More time on string = more energy transferred to arrow. Figure roughly 4% per inch when doing apple to apple draw weight and arrows at the same weight per pound of draw weight. IE 500 grain arrow on both bows.
QuoteOriginally posted by Richie Nell:
So...the increase in lbs. from 26 to 27 inches may be 3 lbs. versus maybe a 4 lb. increase from 29 to 30 inches because of a longer powerstroke?
Not necessarilly. A well designed bow typically will have a smooth draw/force curve with the bow gaining a fairly even amount of weight for each additional inch of draw. If a bow gains more weight per inch the further it is drawn back it is called "stacking".
As Dave said, the power stroke simply means the arrow is on the string longer, giving it more time to absorb the energy as it is driven forward. (I think! :help: )
10-4
I was thinking that the "lbs" was the only way of measuring force. But even though the "lbs. of pull" may be the same, the length of time the force is exerted (nock on the string)the more force and speed you should gain.
Jeremy and David have the right answer. A Force/Draw curve is shaped roughly like a triangle. 50# @ 30" has more area under the curve than 50# @ 28". Simple to calculate, indisputable, and unavoidable.
Two bows of precisely the same design (excluding extremely short bows), with one being drawn to 30" and the other being drawn to 28", will almost always exhibit the same characteristic - the longer draw stores more energy PER POUND OF DRAW than the shorter draw. It doesn't matter if we're comparing 24" versus 26" or 28" versus 30". The relationship holds true. Longer draws at X pounds store more energy than shorter draws at X pounds. Don't make the mistake of comparing X pounds at 30" and Y pounds at 28". That's not a valid comparison.
An example: Joe, who draws his brand X bow rated 50# @ 30" stores more energy (PER POUND OF DRAW) than Sam who draws his similar brand X bow that's rated 50# @ 28". Therefore, Joe will shoot the same exact arrow (precisely XYZ grains per pound of draw weight) faster than Sam because his brand X bow is imparting more stored energy into the arrow than Sam's - even though both Joe and Sam are pulling the same draw weight. More stored energy PER POUND OF DRAW means more energy goes into the arrow for a longer draw length.
Longer draw lengths in bows designed to utilize and benefit from longer draws are always advantaged versus shorter draws.
However, many bows are very short because that's what some people want. Very short bows are AS A GENERAL RULE (emphasis on GENERALIZING HERE) less efficient at storing energy than longer bows. So a short bow may very well yield less benefit to the longer draw because it's stacking and therefore not storing as much energy per pound of draw over those last couple of inches of draw. If you can find a short bow that stores as much energy per pound of draw as a much longer one it would be the absolute schnizzle. When/if you find such a bow you will have found the result of much hard, miserable, low-paying, and sub-economic-return bowyer design work.
Thanks for the great information guys.
CORRECTION: I mispoke the other day to someone about my bow speed. It was in low light and I think I got a bad reading. Just wanted to clarify.
Anyway I chronographed my bow today in good light. The readings seemed slower than I was expecting.
Bow is 65@29 so I am guessing at 30.75 it would be about 71 lbs.
770 grains 31" GT 7595 with 25% FOC. 174 fps.
950 grains shot 161 fps.
Does that seem like decent readings? Does it appear that I am benefitting from a longer draw?
Thanks again
You get two things that increase the energy in your arrow, and also the speed.
As you pull the arrow back your bow is increasing in poundage, and if it is 50# @ 28" then it will be 50+# as you pass 28", the amount differs with each bow. So at 30" you might now shooting a 55# bow.
To give you an analogy for the powerstroke, think of a short barrel pistol and a long barrel pistol. The longer the barrel the more time that expanding gas has to push/accelerate the bullet. The powerstroke is the same thing. The longer the powerstroke, the more time the string has to accelerate/push the arrow. And the more energy it can transfer to the arrow which will increase its momentum when it gets downrange.
Doesn't seem like too bad of speed to me, getting 174 fps at almost 11 gpp. I have a MAIII that is 67@27 and I draw a hair over 29". Haven't chrono'd it yet. Shooting 675 grain arrows at around 73# and it fairly smokes them, but that is around 9gpp. If I can find a chrono, I'll let you know for comparison.
Those speeds sound really good to me for those gpp's.
Also, I might add, you gain about 8 to 10 feet per second for every inch you increase your draw length, not counting the poundage increase added on top of that.
Actually 4fps is more common per inch of draw,
DAve and John explained it best. Some bowyers also say that adding 1" of draw is like adding 5# of weight, weight being equal.
I also saw a post by one of the few very experienced and trustworthy posters that said reaching the holy grail mark of 190-200 fps with 10 gr/lb will be nearly impossible at normal hunting weights and 28" draw. When you get up around 30", all bets are off and you see some dramatic difference. Then swtich from a 16 strand dacron to a 6 strand D97... viola- a 42@28 1965 Kodiak drawn to 30" has now gone from low 160's to 178 fps. Now that's a difference.
Back when I was shooting closer to 65@31 I was getting in that 200 fps range with 10 gr/lb.
I think draw length and a properly made high performance string have to be the two biggest factors. Within the range of "normal" draw weight would come third.
There is a second great advantage that has not been discussed - form. If you have a long wingspan, you will need to be at a long draw to have proper back tension. This could also be a disadvantage if you have a normal or short wingspan and try to draw beyond your natural correct draw length.
Much better to reach correct form than to shoot heavy draw weight.
1 inch of added draw is like adding 10# to the bow weight as far as performance is concerned. IE a 50#@28 bow compared to a 50#@29 bow, the 29in draw bow will shoot much faster and you would have to shoot almost 60# at 28in to get that speed or something close to it. Just for comparison and not exact figures, but you get my drift!
QuoteOriginally posted by vermonster13:
Actually 4fps is more common per inch of draw,
Hmmmmm.....I was thinkin' it was much more than that, Dave. :confused:
Actually the 4-5 fps number is pretty golden. Take a typical bow that's say, 50# @ 28". For sake of this discussion let's say it's 53# @ 29".
So, to accurately measure this you need a shooting machine. Place the bow into the shooting machine and shoot a 10 grain/lb arrow (500 grains) drawn to 28". Let's say it shoots 180 fps.
Now, take the same bow and shoot another 10 grain/lb arrow at 29" (now the arrow must weigh 530 grains since at 29" the bow now pulls 53#). It will almost always shoot 184-185 fps when compared with the 10 grain/lb arrow at 28". So, going up 1" of draw adds (ALL OTHER THINGS REMAINING EQUAL!!) about 4-5 fps.
If we keep the 500 grain arrow that was drawn to 28" (and as a result shot 180 fps) and then pull it to 29" the increment will be more than 4-5 fps. But in this instance the archer has changet TWO things. Not only has the draw length been increased but the grains per pound of draw weight has been decreased. Maybe this way it's possible to get as much as 10 fps difference.
Once again it's important to stress that unless the archer has a perfect release like a super-top-notch archer (think Rod Jenkins) then the only way to measure these differences with certainty is with a shooting machine.