Hi!
Is there a calculator somewhere on the web that can tell you about powerstroke?
Thinking about following:
If you pull a bow 55# with 28" of drawlength what # of bowweight would make an equal when you pull 31" :campfire:
Interesting question, I've wondered about that as well. I draw 29.5 and wonder what poundage advantage I have because of it. In other words, if I shoot 47 lbs at 29.5, whould my arrow speed equal 50 lbs at 28? (just an example, and of course all other factors being equal)
Interesting. I have often though of this and a comparison to performance of the different draw lenghts. But I am not sure it would ever even matter considering I draw 27 1/2" and can't change it.
I do not know if you will find a calculator though.
The old rule used to be 1" of draw was equal to 5# if bow weight in reguards to powerstroke.
Not sure if it still holds true.
Troy
Hmm
5# pr " sounds much?
Thats way I said, not sure if it holds true today.
I do know I've tested the speed difference by basing everything on 10 GPP.
ie: bow pulling 50# at 27" using a 500gr arrow, 53# at 28" using a 530gr arrow and 56# at 29" using a 560gr arrow. When drawn below 28" the increase in speed was only 2-3 FPS. From 28 to 29 it made alittle bigger jump, 4#.
Somewhere down the line you are going to hit a peek. I'd guess to say it would come once the bow starts to stack.
Troy
Inreresting numbers!
But if we as a thumb rule could say something ?
And that it not should take in to consideration the different effency from different bows then what would that number be?
Maybe 2-3# pr"?
So if you shoot a 50@28 I would get the same effect out of a 41-44@31?
Or in the other direction:
50 @28 would give me 56-59@31 in effency?
If a bow gains 2 1/2 lb per inch of draw with no stack then the pickup would be three times that amount. it would be equal to About a 63 lb bow.
This is why I worked toward a rear mounted bow with a 7 in brace instead of 8 1/2 or nine inches.
God bless you, Steve
So the difference would be 13#?
Lordy, all these numbers are making my noggin spin.... Been away from it toooooo long.
I do know you can increase you speed alittle bit by dropping your brace heigth. Guess you can say this is due to the arrow staying on the string longer. I found this out while shooting thru the chronie up close. However, when I backed off to say 20 yds and shot thru the chronie the speed would often be slower with the lower brace compared to the raised brace. I figured this had to do with the tuning being off. Never took the time to retune to the lower brace. Didn't like the way the string would eat on my arm at the lower brace
Troy
Hi, 2 - 3 lbs per inch would be a good average but with a 31 " draw all you have to worry about is getting long enough arras LOL.
Asgeir
Troy I hear ya about the brace. However 7 inches is not an excessively low brace . Ishoot with no armguard with no problems. Most d and r longbows brace about that height but for some reason people seem to have trouble getting good stability with the recurves without a deeper brace.
Margley It depends on the increase in lb you have per inch. If your bow increases 3 lb per inch and you have a 44 lb bow at 28 inches and you draw it 31 inches then your bow would add about 9 lbs . that would make it the equivilant of a 53 lb bow at 28 inches , give or take a lb or 2....
faster arrows have flatter trajectories than slower arrows of the same weight and aerodynamics. In other words if you shoot the same arrow then you will get a flatter trajectory if it is moving faster. If you are hitting lower with the faster arrow it would probably be a nock point change causing it.
God bless you all, Steve
I know from my experience with DAS ILF limbs that the preload is more important than a given weight at a determined draw length. For example, my wife shoots 46# @ 26". Two years ago she had trouble with her thyroid, lost strength and was unable to shoot 46#. I lowered the weight on the limbs to about 42# but the performance lost was significant because of the loss of pre load. I got a lower weight set of the same limbs, same length, and set them for 42# @ 26". Because the preload on the new limbs was increased in order to get to 42# she was able to redeem the performance she lost with the same set of limbs, set at 42# but with much less preload. So, one set of limbs at 42# was significantly better performance-wise than the 42# limbs with less preload. I know that was redundant but I think limb design has a lot to do with performance and one bow of equal weight at 28" may actually outshoot a bow of equal weight at 31".
Sixby, that's good information, thank you.
I look forward to hearing from other skilled bowyers.
Those of us with longer draws, but who choose a slightly lower draw weight, want to know!
I used to think fellows with short draws had it made.
Now that I understand things better I found that short draws are a cursed.
I have a 29-29.25" draw and find I can shoot lower poundage and still get the same preformance as my friends that have short draws and heavy weight bows.
My only problem is with the arrow.
Troy
Margly,
I am unaware of any such online calculator. However, to calculate draw weight at a given draw length, divide the draw weight at 28" by (28 minus brace height) to arrive at the weight that you would need to add or subtract for each inch or part thereof above or below 28". Once you get this figure, it's simple math to find out what draw weight bow is required at a given draw length to arrive at your desired draw weight.
Dodger
I was told 3# per inch as a rule of thumb when going over 28". I checked it before on a R/D longbow and again tonight on a recurve and it came out on the money. My 49#@28" came in at 58#@31", exactly 9 pounds at 3". Brace height set to recommended height. YMMV.
I am thinking that there are too many "other" things to consider to be able to calculate this out in a forum setting.
it comes down to. . . whatever speed your bow puts an arrow down range at, thats what it does.
Shoot it thru a chronograph, shoot other bows using the same arrow, which ever one shoots fastest has the best performance FOR YOU. Make it shoot a good clean arrow and you got you a winner. Done !
ChuckC
What Bill Carlsen says makes sense, and is part of why it would seem to be better to shoot a bow designed for a 26" dl than try to achieve the same weight in a 29" dl (using more #). Yes, it is the same holding weight at total 26" dl, but the 29" limb may not be working as hard throughout the draw or designed as efficiently for the 26" draw.
Just something to chew on with custom bows, but in most cases (like 1-2" draw) probably won't make much difference.
BH doesn't seem to be a big deal in the stickbow world, but seems like having 1 - 2" less bh would lead to a slightly faster, less forgiving bow (all other things being equal).
QuoteOriginally posted by Bill Carlsen:
I know from my experience with DAS ILF limbs that the preload is more important than a given weight at a determined draw length. For example, my wife shoots 46# @ 26". Two years ago she had trouble with her thyroid, lost strength and was unable to shoot 46#. I lowered the weight on the limbs to about 42# but the performance lost was significant because of the loss of pre load. I got a lower weight set of the same limbs, same length, and set them for 42# @ 26". Because the preload on the new limbs was increased in order to get to 42# she was able to redeem the performance she lost with the same set of limbs, set at 42# but with much less preload. So, one set of limbs at 42# was significantly better performance-wise than the 42# limbs with less preload. I know that was redundant but I think limb design has a lot to do with performance and one bow of equal weight at 28" may actually outshoot a bow of equal weight at 31".
I agree Bill that preload has a lot to say, but what I'm thinking about is as follows:
If you and I use the same type of limbs on our DAS'es you pull 28" and I pull 31"
With the same preload what # would you use to get the same performance as I if I for example shoots with a 55#?
(we will use the same arrow)
Just read thru the thread again and there is a lot of good advises here :thumbsup:
Hello, I draw between the 29 and 30 inch. What you gain in weight is dependent of the weight you start with. The rule of thumb is simple: add 5% per inch more. If you go from 28 to 31, you will gain 15%. For 55 lbs this is 8,25 lbs.
So at 31" you will end at 63,25 lbs with this bow.
I wonder if the English Longbowmen or Native Americans sat around the campfire wondering about the draw force curve of their bows...
Javi,,,
lmao.....
Most likely they were wondering where their next meal was coming from and if anyone saw them miss that deer earlier in the day.. :-) :-)
Troy
Deleted.
I can tell you that 50 odd years ago, I bought cedar shafts spined 5# more than my draw weight and hand straightened them, cut them to 28" cause that's what the measurement was when I stuck a nock in the middle of my chest and held the arrow between my outstretched hands, tapered them, glued a nock and a 125 grain point on them, fletched them and went out and shot them.... I didn't worry about tuning the bow other than nock point and brace height; I didn't care how much the arrow weighed, or how much FOC it had. I worried about how sharp the broadhead was and how straight the shaft was... I couldn't have told you if my arrows all weighed the same or if they were spined within 1#; all I knew was if one didn't fly good and hit where I was looking it got burned in the stove for kindling come winter.. We didn't know nothing about shooting off no point or gaping, drawforce curves, or skinny strings we just killed stuff with our bows, some of us even shot field archery with our hunting bows... had a bunch of fun..... oh..... did I say killed stuff with our bows... :D
Bill Carlsen has it right. A lot depends on the limbs and what poundage they were built for. As a rule they say 3#s per inch over 28"s but some limbs start to stack at 28"s and that can be up to 5#s an inch out to 30-31"s. My new Borders are very smooth and I beleive after 28"s they gain only 2-2.5#s an inch until you get out there past 31"s or so. I also do not know about sixbys post, I don't think it would make it like a 53# bow at 28"s, that 3 more inches of power stroke will increase FPS. I doubt all else being equal a 53# at 28" bow will be as quick as a 53# bow at 31"s. Shawn
I also would say to marglys question that Bill would have to shoot a bow that is around 63-64#s at 28"s to get the same performance you would out of your bow at 55#s at 31"s. That 3"s of powerstroke is huge, just ask the guys who draw 26-27"s. Shawn
Margly: There is no doubt in my mind that draw length would improve bow performance with two bows, identical preload and one was X#'s at 28' and the other limbs were the same weight at 31". When the DAS bows first came out there was a great deal of discussion about this on other sites and that seemed to be the consensus. I do not know, however, if you could quantify the dynamics simply because every bow is designed differently and the use of various materials, carbon for example, would all have to be figured in in some way.
I draw 31", and shoot a 48# @ 31" longbow. This thread is of great interest to me, as I have wondered the same: Can I have the identical "confidence" in the "knockdown power" of my setup as a guy shooting, say, 55# @ 28"??? (All other variables being equal.) I shoot heavier bows, too, but the 48-pounder is just so pleasant to shoot...
Archie
QuoteOriginally posted by Bill Carlsen:
Margly: There is no doubt in my mind that draw length would improve bow performance with two bows, identical preload and one was X#'s at 28' and the other limbs were the same weight at 31". When the DAS bows first came out there was a great deal of discussion about this on other sites and that seemed to be the consensus. I do not know, however, if you could quantify the dynamics simply because every bow is designed differently and the use of various materials, carbon for example, would all have to be figured in in some way.
Hi Bill!
I have the same thoughts and is curious about the difference in performance, I do have a Firefly longbow 66" 43@30 and acces to a same in 46@28 and will give it a try and see how it goes:)
Of course it is a lot of unknown factos but this will give me a clue of what we are talking about!
Take care:)
Ronny
NB Will post the results after some chrono testing:)
Shawn, I guess I worded that wrong and good catch. I meant that the bow would probably pull about 53 lb at 31 in draw.
I believe what I was trying to say is that if the bow still pulled 44 lb when drawn to 31 inches then it would shoot much harder that the same 44 lb pull drawn only to 26 inches.
We are attempting to analyze how much is gained by adding inches, not lbs but we have to have a lb per inch figure to do that.
With my analysis, (right or wrong) agree or disagree. The 44 lb pull at 31 inches would shoot like you had added 8 or nine lbs more weight over the same 44 lbs pulled to 28 inches. I believe this is harmonious to what you are saying but I did not make myself very clear nor am I completely sure that the figures are exact. The added three inches of string time definately does add considerably to the performance without having to add poundage.
Now as to preload. The limbs can be built to have preload without having a high brace. You gain on the bottom end or brace end extra string time instead of tacking it on with a long draw. This increases the efficiency of the bow without adding extra poundage. It really helps all draw lengths but especially the shorter draws. A person with a bow with a brace of 7inches compared to the same poundage bow with a brace of say 9 inches , that has a draw of 26 inches will be able to have the performance that they normally would have to draw 28 inches to get.
God bless you, Steve
As far as how much weight the bow gains per inch of draw...that would depend upon a few things...
1. Design (recurve, longbow, r/d hybrid, amount of backset/string follow, tip angle, etc),
2. core to width ratio
3. carbon or not
4. trap style (IME a rev trap draws smoother than the typical belly trap),
5. bow length, and
6. riser length
All that said, most bows of that pull weight would gain between 2.5# to 3.5# per inch with the better ones being on the lower side.
Now, that said...let's say your bow is 55#@28 and 64#@31", you are going to get way more velocity than a bow of the same design that is 64#@28" draw. I suspect this is where the 1" of extra draw equals about 5# of extra draw weight at the same draw comment comes from...although I would venture to say it would be equal to even more than that.
You can bet for sure that if you had two shooters with different draw lengths shooting the same weight the longer draw would be faster.
Longer powerstroke is a big advantage.
Troy
Cool.
I always wondered if I would be better off getting a set of 45 pound limbs @ a true 29in vs 53# limbs drawn to 28inches....
pretty interesting thread, but it has too many variables and gives me a headache thinking about.
I believe that the technical answer is going to be different with each bow and that you have to look at the "area" of increase under the force draw curve for the additional stored energy under the draw force curve for each inch of draw. As noted above, this is going to be different for each bow and the draw length for that bow. If you look at the graph that's in Blacky's bow report article in each TBM issue, you'll see what I mean. I wonder if Blacky has an average that he could share with the class?
These threads are interesting. I especially enjoy technical input from bowyers as well as "experienced" (ie older) guys. I wish there was some way to quantify the effect.
I do know that when I went from 28 inch draw to 29 1/2 after my eye surgery that allowed me to stretch out without hitting glasses I was impressed with both the power increase and accuracy increase. The new eyes may have had something to do with the accuracy, but the power was for sure powerstroke.
R
Ryan, if the bow was the same, you just added one and one half inches of draw,increased the bow weight by maybe five pounds, maybe hit the arrow spine more correctly, and shot tighter groups! Just my 5 cents worth.
I draw 26 1/2". I used to shoot a 58# BW recurve, and it didn't seem to me that I was keeping up with the guys drawing 28" at even 50#s with properly preloaded limbs.
Powerstroke is a BIG advantage, just as it is with a wheelie bow. Can't fool physics guys.
Typically the weight of draw per inch, 2 1/2# is the accepted norm.
A far as power is concerned, the area under the curve should be a good comparison of one bow to the next.
A better comparison would be to measure the weight at a given length as you let down. This allows for the hysteresis (Loss due to internal friction) of the bow
Now, I have a headache...8^) This stuff ain't suppose to be rocket science...8^)
Gotta agree with ya Javi...
Been doing this stuff a long time and this is the first I ever heard the term "preload".
Can someone please enlighten me?
Thanx
Preload is the poundage at correct brace for the bow design. It varies greatly with design. Say from a string follow bow to a highly reflex deflex design. the string follow bow generally would have much less preload. It would also be a less effiecient bow. However a lot of guys love the way they shoot so they will sacrifice the speed and effiecieny for the special feel of a string follow bow. And VS versa
God bless you, Steve
QuoteOriginally posted by Sixby:
Preload is the poundage at correct brace for the bow design. It varies greatly with design. Say from a string follow bow to a highly reflex deflex design. the string follow bow generally would have much less preload. It would also be a less effiecient bow. However a lot of guys love the way they shoot so they will sacrifice the speed and effiecieny for the special feel of a string follow bow. And VS versa
God bless you, Steve
Very good explaination :thumbsup:
Thanx for the explaination.
QuoteOriginally posted by Bill Carlsen:
I know that was redundant but I think limb design has a lot to do with performance and one bow of equal weight at 28" may actually outshoot a bow of equal weight at 31". [/QB]
X2 A good bowyer can design a bow for a short draw that will lose little if any efficency.