I realize there are so many variables, but say you have a 650 grain arrow and shoot it from a 40 pound, 50 pound and 60 pound bow of the same maker. Like a bear Montana or instance. How much difference in speed of the arrow do the different draw poundages have?
Wouldn't that depend entirely on the efficiency of the bows design, not poundage?
Maybe, but what then is the point of different pull weights?
Not really, but I used to have good luck with Archer's Advantage calculating how fast a different weight arrow would shoot from a bow that I had a speed chronoed from a known arrow. But you had to have accurate data like length and weight of an arrow etc and if you had good data put in you could plug in other arrows from a list and see how it would perform.
I built this calculator http://www.outdoorsden.com/archery/archbal.asp (http://www.outdoorsden.com/archery/archbal.asp) a while back to basically do just that and allow a comparison between bow designs. While there are always some averages/assumptions that have to be made to keep it simple, the calculator will get you very close.
Aside from plain curiosity, what and why would any of this matter in the real world?
I don't care about arrow speed. You have a bow, you test out arrows of different mass weights and perhaps different spines and decide what works best for you, your shooting style, your bow and its string, the distances typically shots taken at, the percentage of consistent accuracy the arrow delivers, and of course the critters hunted.
I must be too old school to get into the peripheral esoterics of the trad archery/bowhunting game. :dunno:
I sort of like Rob, do not care about arrow speed.....to a point. Do I want to shoot a bow that is a dog? No. I don't think anyone wants to. Is it useful to know arrow speed? I'd have to say yes, it is useful. It would be nice to know if/when you make any changes to your set up, if you have increased or decrease the speed/performance of your set up. Is it essential? Heck no ......... unless you are a bowyer. Good bowyers has this handled for those of us who aren't. Some peoples thing is to break down the numbers to the nitty gritty and know all the finest details. I respect that and respect those who want to incorporate that into their stick bow sets ups. We have the freedom to approach this interest/hobby/obsession in a manner that leaves each individual satisfied and keepin' at it. I like detail and specifics myself but I'll admit, it can get to a point with me that I'm going down the black hole of crunching decimal places and .0001 of an inch and .25 fps and any other negligible variances, that my brain shuts down and I revert back to how cool it is to just hold that light sleek longbow, nock a beautiful arrow that I built myself, nock it on the string, stretch out my upper half and let it rip, willing that arrow to the mark in front of that high tension thud of the string coming down. I'd say the second you feel like the tether to simplicity that makes shooting a stick bow what it is gets too long.....which it can, it always feels good to take in the slack again.
Not ignoring the original question about the speed calculator. Apparently (YES) they exist and are useful? I would say if you really want to know speed and have an accurate or even precise answer, you need to shoot THAT setup through a chronograph. Otherwise, you're going to get "pretty much" there. And I know, for someone who wants those finest details, "pretty much" ain't ever going to make you totally happy :campfire:
I don't need to know actual arrow speed.
Knowing whether or not an arrow is going fast enuf for a specific distance and task is easy - if the arrow trajectory isn't flat enuf to suit consistent accuracy, then a lighter mass weight shaft is probably needed. No need to make arrow shaft choice complicated when simple works.
When I went to the Black Widow instinctive archery course many years ago, Ken Beck made a comment that made a lot of sense to me. He told us that any of their bows, within the normal weight ranges that people bought them, would probably end up shooting at about 185 fps with a 9 gpp arrow. Of course, this was before the days of EFOC, so now you would have to adjust the velocity down somewhat to account for that, if an arrow weight in excess of 9 gpp is your preference. Also, when I later attended a seminar by Rod Jenkins, I found that the shooter had a lot to say about arrow velocity depending on his release and form.
But the point is that if you shoot arrows with the same gpp, and don't change your form between bows, you will shoot heavier arrows with heavier bows and lighter arrows with lighter bows, so your arrow velocity won't change much. At the same gpp and form, efficiency of the bow will have more to do with sarrow velocity than bow poundage.
ScouterMike I plugged in some data from one of mine and found your calculator spot on. It was basically a mirror of the gaps I have. Pretty cool.
I agree that knowing the arrow speed or other technical details is not necessary to enjoying or being successful with a traditional bow. Most of my bows are string follow longbows and my main hunting bows have a reverse handle so I am not really into high performance for the sake of it.
Sometimes however things come up like above...I wish the trajectory was flatter so I think I will just shoot a lighter arrow or get a 5lb heavier bow. The real question then becomes how much difference will the change make and will it be worth it? Questions like that and some of the crazy assumptions/conclusions we often share that are just plain wrong is why I decided to crunch some numbers and ended up with the calculator. Will a FF string really make a 20 fps difference over B50 on my longbow? Will my Hill style longbow really shoot those heavy arrows faster than the same weight recurve? Will that new fast recurve really shoot flat to 30 yards and then start dropping? Most of us that have been around a while have heard them all several times. I can answer all those questions without touching a bow, just crunch data. (Full disclosure - my title at work is director of data management)
I have found that knowing the numbers helps me make good decisions and gives confidence. It also clarifies why that arrow flew 10 inches under that hog that my brain thought was 20 yards away and was really 30. BTW thanks Todd and if you wanted to know how much a heavier arrow would affect those gaps, the data would be close....
To the original question I would predict...
Bear Montana longbow with 650 grain arrows and basic ff string. Drawn to the bows listed weight of course.
40 lb - 133 fps
50 lb - 149 fps
60 lb - 163 fps
About five years or more ago I chronographed every recurve I bought. Of course the draw weights were very similar and it turned out that most of the bows (custom jobs mostly) shot about the same FPS.
I did find one dog but I could tell it was vastly slower by eye. Around 150 FPS with 424 grain arrow where most of my bows were in high 160's. I have a 26" real draw so I'm a bit handicapped from the get go.I did sell that bow within a couple of weeks. I've never divulged which model of bow it was and won't. While it isn't a rare brand and has been around a long time, it was one that was only very rarely mentioned here on the Gang. I may have gotten a bad one?
I don't chronograph my bows anymore because like I mentioned, if draw weight and arrow weight are the same, or nearly so, the FPS is also nearly the same.
The best arrow chronograph is an organic computer - yer brain, as it receives input from eyes and ears as any arrow is launched at any competent typical trad bow killing distance. :wavey: ;)
Now that said, my extreme long range rifle *requires* and *demands* the use of a good chrono (Magnetospeed) in order to build good cartridges for my 300 to 1000 yard shooting distances. So no, I'm not an anti-chrono'er. :saywhat: :thumbsup:
The tale of two chronographs. This came up while watching the weather yesterday. A fellow that use to live here wanted to know how much KE he would get from a light carbon arrow versus a EFOC, but at 30 yards. He set up his ILF to be point on with both arrows at 30 yards. When he thought he was ready, he measured the distance and set up the chronograph and careful took a shot with the light arrow first. He killed the chronograph with his first shot. Turns out the chronograph was borrowed. So he bought the owner a new one. Then later the owners friend bought one as well, he had money. No matter what they tried they could not get the chronographs to agree. Shooter's variance? I do not know how to tweak them, but everyone seems to think that their's is always correct.
I'm VERY interested in my arrow weight and speed as it gives me VALUABLE info on momentum. I don't hunt just whitetails.
ScouterMike--- your calculator is an excellent resource for the very reasons you mentioned. Within a couple gpp difference it shows net gains or losses aren't quite as dramatic as I sometimes envision when I think of changing something up. Thanks for sharing.
This is my opinion only, and I am sure it is not based at all in real science. Everybody I know is interested in how well their equipment is performing. Many don't understand momentum, kinetic energy, and other concepts that factor in the performance of their rig. However, they understand the concept of speed. Besides, it is something that can often be seen with the unaided eye. Consequently, speed is often equated with performance by a lot of people. Therefore, they seek speed as "proof" of performance. While I agree with Rob, I still think most people strongly desire more arrow speed. Even Howard Hill Archery uses speed in their advertising, stating their longbows will shoot 115 fps plus the weight of the bow. Their example is that a 65# bow should shoot approximately 180fps. (115 + 65). I suspect this concern about speed has been true as long as there has been archery.
I use a chronograph in training occasionally. However to my way of thinking the most valuable data it gives is extreme spread and standard deviation. That data gives ONE measurable input to indicate how consistently you are drawing and releasing the string. There are other variables as well but as with any shooting sport consistency is typically far more influential than simple velocity measurements.
The latest version of Stu Miller's Dynamic Spine Calculator (2011) will give you that information. It runs on Microsoft Excel. Get it here.
https://heilakka.com/stumiller/