Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on November 27, 2017, 02:15:13 pm
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I recently decided to drop to drop my draw weight. I was making bows in the 40-43# range but I wasn't getting full draw at that weight. Getting old I guess. Anyway I've made my last couple of bows at 35#. I was expecting the arrow speed to drop but at 10 gpp it's actually gone up a bit. These last bows are consistently in the high 170's with a few shots into the 180's. I was willing to kill to get into the 180's but I guess I dodged that bullet ;D Was a higher speed at 10 gpp at a lower draw weight to be expected?
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your form at the lower weight may be part of that,, and getting good full draw too,, or maybe you making a better bow now, since you are over the pyramid craze,, (-S
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Don't like pyramids do we Brad ;D ;D ;D. I figured that improved form and draw would help but in the back of my mind there's something that says lighter bows are faster using 10 gpp. I think I read it somewhere but I wanted to check. If it's just my form and draw length then maybe I should just buff up a bit and my 40#'ers should be screamers. Yeah right. To me getting in shape means shifting my position in my recliner.
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it does seem easier to make a lighter bow shoot harder,, really some of my bows look pyramidish ,, so no worries,,
i have not read that but have wondered about that
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Part of me has wondered, from time to time, if people building heavy bows do not always feel the need to maximise bow performance in the same way as those building medium and light-weight bows do. Equally, I think I read that more wood means more internal friction losses so 'big' bows are less efficient?
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First off how heavy are your arrows? The only way that a lighter bow will outshoot a heavier bow is if the lighter bow is made better. Speed without knowing arrow weight doesn't really mean anything. Are you talking 10 grains per pound? Your heavier bow may have been overstrained dropping performance. At 10 grains per pound high 170's is smoking fast. I have never seen that fast on a straight bow.
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Try shooting the 350grain arrows from the 40# bow...
Del
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Full draw means a lot regarding speed. Jawge
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First off how heavy are your arrows? The only way that a lighter bow will outshoot a heavier bow is if the lighter bow is made better. Speed without knowing arrow weight doesn't really mean anything. Are you talking 10 grains per pound? Your heavier bow may have been overstrained dropping performance. At 10 grains per pound high 170's is smoking fast. I have never seen that fast on a straight bow.
I always use 10 grains per pound(or as close as I can get) for chronoing. This arrow was 360gr and the bow is 37#. The arrows are 30" so I may be overdrawing a bit. It's amazing that dropping about 5# let me draw another 2". Some king of mental block I guess. It wasn't just one heavier bow. With the last ten bows or so I've been sneaking up on speed and draw weight. I was up to 44# two bows ago but my draw length had dropped by a couple of inches. Last two bows are about 37# but with them I can get 27" draw and both are in the high 170's. The Dogwood I just posted and a slightly recurved OS. I've always suspected my Chrony as being faulty but I've asked about it before and i think it was you that said he'd never seen one be out of calibration. They either work or they're broke. You suggested that I try for distance but I can't find a spot. I was going to use the beach but in the summer they are full of people and in the winter there are no low enough tide during the day to get to the sand. I'm bummed now because I'm back to suspecting that I have a faulty Chr.ono
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if it is faulty, its the right way,, :)
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Try shooting the 350grain arrows from the 40# bow...
Del
I used my last "heavy" bow it's 43#. I got in about ten or so shots all around 185-187 with one at 192 but that's probably an error. Then I hit the plywood frame of my target and smashed the arrow. It was a hemlock arrow and they're a tad brittle. I'm gunna be some disappointed when I find out my Chorny is reading fast.
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In principle, any bow weight can shoot equally fast at 10 gpp.
The distance covered by each arrow, however, will be shorter for lighter bows. The reason being that air density (and friction to be overwon) remains te same: that is an externality we cannot scale up or down with bow and arrow weight. Since heavy arrows have more kinetic energy, a smaller proportion of their kinetic energy is lost to friction, hence they fly further.
At very short distances, like when chronoing a bow, friction differences between light and heavy arrows (10 gpp for a light and heavy bow) are negligible.
When talking 10 gpp and 28" draw (or actually, a 22" power stroke), 175 fps is exceptional for a straight bow. longer draws, however, can get you a few fps more. So maybe you're just drawing it a bit further at the lower draw weight.
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I've sent an e-mail off to Chrony asking about whether or not they go out of calibration and how much it cots to recalibrate. What with shipping both ways it may be better just to buy another one. If the two Chony's agree then I'm golden. See what they have to say.
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I'm not saying this is the case with your Chrono but if I'm just using natural light with mine I get some crazy fast eradic speeds but when I use the led hoods I get much more consistent readings also I disregard the speeds I get tell the bow has at least 200 arrows threw it and keeped braced for 1 hour then I pull it to full draw 3 times before shooting arrows usaly gives me real numbers that's similar to how Tim Baker did it I read , I'm not saying your numbers are wrong just saying I get a lot faster numbers on a fresh bow ! Plus wrong spine arrows give me erratic numbers to. chronos can be real touchy some times !
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I actually get very consistent numbers. I read on a website a few weeks ago that painting the tips of the arrows flat black helps get more consistent results. I tried it and now I get nice repeating numbers. I still get errors when I screw up but by and large I get good repeatable numbers. It's whether they're accurate or not that's my problem. The test I did for Del's suggestion was nice and solid, 8 or 10 shots all within 3 or 4 fps except for the one at 192 but that was just 4-5 fps out of the range. That could have been me. I just ignore numbers like that, they get me too exited.
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ok i made a straight stave bow shot pretty good last year,, my disclaimer is I shot by myself pulling the arrow to a piece of tape, and the hand scale I used is ok, but who knows,,
and the arrows not quite 10gpp,, but here it is,,
the bow was about 51# @ 27
I pulled it to 28 and figure about 53 at 28
it was shooting512 grain arrow 181 fps,, ok the bow was fresh,,most shots were in the high 170's,,
I did tiller the bow out to 29 1/2 but did not test it at that draw,,
the bow was holding some natural reflex after being shot in,, so I am guessing cause I cant do the math,,with 540 grain arrow maybe mid 170's,,
so I think your straight stave bow is shooting close to what you think, but wouldnt hurt to check with another chrono,, so you can sleep at night,, )P(
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If your getting contestant numbers with in 3 fps then I would bet your Chrono is probably ok , maybe you could find some body else that has one or a archery range that has one to test it !
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Cabelas is having a Cybersale. Free shipping and a Caldwell Chronograph for $100 Can. So I ordered one. If the two chronos agree then I can stop arguing with myself.
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I doubt your chrono is faulty, I suspect you have a pretty fast bow and are slightly overdrawing. This would easily account for a high number like you are getting. 180 at 10 grains at 28" is smoking fast for a self bow even with recurves and backset. I have honestly never seen a bow go past 170 if it had more than 1" set. It is also possible you may have trained yourself to crank up your release. You can add a lot of speed doing this. I do it for fun to see what I can get but when testing I have to avoid doing it. I have actually added over 20 fps using an active bow hand and pull through release. 10 fps is easy to add even if you don't realize you are doing it.
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crank up your release. You can add a lot of speed doing this
snap shooting, Steve? I will bet there is a bit more to the technique to get 20 fps gain...active bow hand....
Some of us would appreciate hearing a bit more about how the flight shooters get some extra oomph,
thanks
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Willie, I can't get much of a snap shoot in the flight shooting position, I think I can get a little but not near as much as I can get shooting through a chrono. It is mostly just practice and timing. You rip your fingers of the string so their is absolutely no forward creep loosing draw length. You bend your left arm and throw a left jab just as you release. Kind of like shooting from a moving car.
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I can't imagine that the left jab adds all that much to overall velocity, but I can certainty see where the jab makes sure that the string is ripped from the bowhand.
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Willie, I can't get much of a snap shoot in the flight shooting position, I think I can get a little but not near as much as I can get shooting through a chrono. It is mostly just practice and timing. You rip your fingers of the string so their is absolutely no forward creep loosing draw length. You bend your left arm and throw a left jab just as you release. Kind of like shooting from a moving car.
So for good honest testing you just draw normally, hold for a split second and release?
PS So, what is wrong with "cranking up the release". Arrow speed is arrow speed, right? If the arrow is going 180 fps 6" from the bow it's going to go as far as 180fps will go. Unless this is a "bad release" and the arrow isn't flying cleanly?
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DC, nothing wrong with it, just not good for testing bows, great for flight shooting though. In all honesty bow testing by hand doesn't really mean a lot unless you have really refined your testing techniques and even then it is questionable. It is great for your own knowledge but doesn't always give accurate results for others to compare to. If you are talking speed for a flight bow and not really looking for a measure of the bow then snap shooting is what you need.
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So I should make a shooting machine?
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Wow that is fast for sure, That is fast for a 50# bow much less a 35, you may have stumbled up on something and wished I could figure out what. ;) :)
Pappy
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Don that Caldwell is a good solid machine does it come with the L E D hoods ? They have nice soft ware for the computer also, the tournament archers at a range I go to swear buy them , thats a steel at that price !
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It'll be a week or so til I get the new chrono but I'll go out today(if the rain holds off) and try a few more tests. I'll put tape on the arrow (after I repair it) to limit my draw length and just draw and release as if I'm target shooting. I've always questioned my chrono results. I don't think my skills are up to the numbers I'm getting. You have to be able to trust your tools. To bad there isn't a convenient way to calibrate them. You would think there would be an app for that.
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OK New 374gr arrow with tape at 27 1/2",extra 1/2" to allow for the thickness of my finger, bow weighed at 37#@27". Draw slowly back til the tape hits my finger, pause, and release. 6 shot all in the mid 170's. Best of 178. I guess it's wait for the new chrono
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I bet your chrono is right, You might just have a barn burner there, Chronos are usually pretty accurate or way off and inconsistent. Yours sounds like it is working fine. Just for fun why don't you flight shoot that 370 grain arrow and see how far it will go. About 200 to 215 yards would correlate with your speed. I had a very fast 35# a few weeks ago but mine has about 2 1/2" reflex. I don't have a chrono anymore but it shot a 450 grain arrow over 200 yards so I know it has some speed.
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I would love to but i can't find a spot. I was going to use the beach but in the winter the low tides are at night, the sand is never exposed during the day. The rest of the area is bush,at least public land. maybe I'll have to go knocking on farmers doors.
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that sounds pretty reasonable,, if you can get more with snappier release ok too,,
shooting machine would be nice too, I have always wanted one for testing
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I don't think you can calibrate a chrony post-hoc:
As I understand it, it measures the time between an interference in light (caused by the arrow) between the two light sensors, and calculates the speed from that on the basis of the distance between the sensors. Since the distance is fixed into the housing of the Chronograph, there's no way it can be wrong (unless the sensors have shifted).
So your numbers aren't wrong, IMO.
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I just heard back from Chrony. Apparently the sensors can shift slightly over time. You can send it in for calibration for $50.
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I have a little crossbow pistol which is very reproducible. Maybe an air-gun or some such that you can check on other people's chrono's ?
Del
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The amount they can shift is very small and wouldn't have much affect on your results. On the type that bend in half and fold you do have to be very careful thay are opened straight and level. This can give a false fast if the have a slight bend in them when opened up.
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I've asked their Tech if he would take a guess as to how much it would shift. Since most chronos are used for guns the "slightly" may not be an issue at all for me. Mine is a folding one and I have checked a double checked the little tongue and groove for debris etc.
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Don you will like the Caldwell unit it has a hat trick indicator when you shoot three consecutive arrows at the same speed it will flash and let you know that three arrows where the same speed that's the speed that I log the L. E. D. Lights help a lot you get much better results with them ! (-P
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Don you will like the Caldwell unit it has a hat trick indicator when you shoot three consecutive arrows at the same speed it will flash and let you know that three arrows where the same speed that's the speed that I log the L. E. D. Lights help a lot you get much better results with them ! (-P
That sounds good, I'm getting impatient now. Have you tried painting the first inch or so of the arrow flat black? I found it made a world of difference. Seems strange that this thing will pick up a gray bullet going 3000fps but the flat black tip makes a difference at 170.
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No I have not tried it ,my field points are dark when using the LED lights I don't seem to have issues unless I'm using real out of spine arrows that flirt accross the sensors Brad Smith gave me a tip a while back about shooting back farther from the sensors seemed to help to ,but nothing seems to cure a bad release !
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Yes, I have found that a stiffer arrow will sometimes get better results.
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Don,
Is that Caldwell the "Ballistic Precision Chrono, #IK-232020(US #)?. I have a store within driving distance, so my pick it up there. Maybe putting cart before the horse, but I also need to check some loads for my wife's new rifle. Thanks,
Hawkdancer
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I can't find a part number on my order but it looks like they only make one. There is the chrono by itself and a chrono with a kit. The kit includes a tripod and LED light kit so you can use it indoors. $100 extra for the kit. A camera tripod will work.
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You also get a case that fits every thing I got my kit on Amazon a while back for $129.00
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lighter pound bows may tend to make faster shooters probably because it's easier to make a bow without set if it's lighter. The material is under less stress while the design doesn't change that much, and you have more room to work on perfecting the tiller.
For speed and target shooting, this advantage may be good.
But if your hunting or flight shooting, then the light arrow may have less kinetic energy.
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lighter pound bows may tend to make faster shooters probably because it's easier to make a bow without set if it's lighter. The material is under less stress while the design doesn't change that much, and you have more room to work on perfecting the tiller.
For speed and target shooting, this advantage may be good.
But if your hunting or flight shooting, then the light arrow may have less kinetic energy.
I believe you are right that they are under less stress but in reality that is only because the heavier bows are under designed. The stress is ideally identical regardless of draw weight.
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lighter pound bows may tend to make faster shooters probably because it's easier to make a bow without set if it's lighter. The material is under less stress while the design doesn't change that much, and you have more room to work on perfecting the tiller.
For speed and target shooting, this advantage may be good.
But if your hunting or flight shooting, then the light arrow may have less kinetic energy.
I believe you are right that they are under less stress but in reality that is only because the heavier bows are under designed. The stress is ideally identical regardless of draw weight.
Ideally, if we were excellent bowyers our designs would appropriately reflect the stresses. you seem to demonstrate this, but many, myself included, don't. DCs realization probably shows like you said, that we tend to "under design" our bows.
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We're just looking for that magic balance between over stressed and over built. I think I've hit it a couple of times but it was just out house luck, it really wasn't good planning.
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DC did the caldwell arrive ? (-P
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No, It hasn't even been shipped yet. Christmas rush they say :(
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Not sure if this goes here, but we are talking chromographs. Sort of had to choose between a Chrono and new boots - the boots won, since I use my feet all the time while hunting! Boots were on sale about half price, and I had an extra $20 USD club points! Got out before temptation took over! Went looking for the chrono. in the Shooting Accessories section, (logical place) - didn't see them, looked twice at that rack, still didn't see them, went to find an "outfitter" to get help. Got the new kid on the block( dumb looks are still free), he had to go ask a more senior guy, flagged me over, and took me back to where I was - they were hiding in plain sight, in bubble packs, right next to where I looked at something in a box!! Duh! Been a bear or abig cat, they would have bit me! Thanked the outfitter for his time, and admitted I had a dumb attack! At least, I know what I am looking for now, and where to look. Now just have to get the "piggy bank beer mug full, and maybe they will go on sale by spring. Have to check that other supplier (Sprtsmn Whse) to see if they have them, closer and often cheaper,
same military discount.
Hawkdancer ;D :P ::) :-[
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Just for fun why don't you flight shoot that 370 grain arrow and see how far it will go. About 200 to 215 yards would correlate with your speed. I had a very fast 35# a few weeks ago but mine has about 2 1/2" reflex. I don't have a chrono anymore but it shot a 450 grain arrow over 200 yards so I know it has some speed.
Steve, Is there a way to estimate cast when you know lbs pull and GPP?
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Not really, all bows are different. You can roughly estimate based on speed if you know that.
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ok, is there a formula or method to plug in the speed?
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The speed may vary from 140 fps to 180 fps with the same weight bows. You just have to test them out. For distance vs speed I always figure 170 fps can get 200 yards + or -. 205 fps can get about 300 yards.
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DC...Here's my chrono.Could'nt tell ya the brand because I don't have the box it came in any more,but it works great.Had it for quite some time now.Used it a bunch.Got it from an archery supply business.Only use it on sunny days most times for good readings from it.
(https://i.imgur.com/a5ZjSrG.jpg)
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thats the same one I have,,, I like it,,
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I have about 6 of those that don't work anymore and about 4 of the green ones that fold in half. For some reason I don't get much life out of my chronos. I don't shoot them or bang them around, they just quit working right.
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your energetic field is too much for them,, (-S
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I always figure 170 fps can get 200 yards + or -. 205 fps can get about 300 yards.
thanks Steve. does that speed to distance ratio hold true no matter what the GPP? what happens when you are shooting 5 GPP?
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Willie, the heavier arrow will travel further at the same speed. I think they have a better ration of mass to drag. Josef is about the most successful flight shooter at the moment and he is using mostly 28" or longer arrows. I don't know the weight but I imagine around 300 to 400 grains depending on the spine he needs.
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it would be interesting to plot some weight vs speed and especially weight vs distance curves on a graph and see the shape of the curves
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Willie, the heavier arrow will travel further at the same speed. I think they have a better ration of mass to drag. Josef is about the most successful flight shooter at the moment and he is using mostly 28" or longer arrows. I don't know the weight but I imagine around 300 to 400 grains depending on the spine he needs.
The reason for this better ratio of mass to drag is that mass increases cubically with arrow diameter, whereas drag (surface area!) only increases quadratically (power 2).
For example take two douglas arrow shafts (sg 0.5 g/cm3), 0.8 cm and 1.2 cm thick, both 26" long, which translates roughly into 220 grains and 500 grains of mass. The surface and hence drag of the heavy arrow is only 1.5 times that of the lighter one, but its mass has increased by a factor 2.25.
So although the heavy arrow has 1.5 times more drag, it has 2.25 times more kinetic energy (E=MV2) at the same initial arrow velocity. Relative to the light arrow, It has more kinetic energy to compensate for drag (its drag coefficient will hence be lower), hence it will fly further.
We know there is a trade-off between arrow speed and arrow mass. However, because of the virtual mass of a bow, arrow speed doesn't decrease linearly with arrow mass. Taken the non-linear relation between drag and arrow mass, there is a sweet spot (arrow mass) at which a bow can shoot farthest. At that sweet spot, both heavier and lighter arrows will reduce distance.
Part of the flight shooting game (next to arrow tuning, arrow shape, drag reduction, release, ...) is to find that sweet spot of perfect arrow mass for that particular bow.
This means it is possible that an heavier arrow shot at 190 fps may fly further than a lighter arrow shot at 200 fps. I think Steve can testify to this.
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Taken the non-linear relation between drag and arrow mass, there is a sweet spot (arrow mass) at which a bow can shoot farthest.
and consequently, an ideal SG of the arrow materiel, so that there is enough diameter to make spine?
Is there a way to plot this non-linear curve?
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in theory it's possible to plot these things, for theoretical values. But there are just so many different variables for which we don't have reliable parameter value estimates that it doesn't make too much sense to me, right now. But if we have better inputs, we may at least narrow our search area for ideal arrow-bow combinations.
At the very least, we would need to know the actual drag coefficients of the (flight) arrows being used. Which can be estimated, I think, by shooting through a chrony at varying distances.
For a technical and theoretical discussion on virtual mass, distance of arrow flight etc, see https://sites.google.com/site/technicalarchery/technical-discussions-1
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DC did the caldwell arrive ? (-P
Well it arrived. Ten days to get across the warehouse and 2 days to get 1000 miles and in the meantime it has been officially designated a Christmas present so I can't open it yet. And because of family work comitments and stuff we're not celebrating Christmas until Dec 30 so nothing until then. Humbug ;D ;D ;D
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Well, she let me open it today but in the instructions it says it won't work reliably on snow. Maybe in 3-4 days.
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Sounds good (-P
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I couldn't wait. I tried it in the snow. It worked great. Way less errors than the Chrony but then I've never used the Chrony in the snow. I only took ten shots or so cause it's cold out there. I only got two errors. Worst shot was 169 and I flubbed that. Most were high 170's, best was 182. So this means that my Chrony works so now I have two chronos. But the best news is that my bows are as fast as I was being told by the old chrono. That makes me feel very good.
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Congrats ! That was a long haul to confirm your results but awsome speed, I really like the Caldwell it works in most conditions !
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I just noticed that I was using a light arrow. The bow is 44#@27" and I was using a 372grn arrow. So that's 8.5 gpp. I'll try a 10gpp later.
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That should put you at about 170 fps with 10 grains which is still very good performance.
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Good deal!!!
I am lucky enough here to be able to compare my readings on my chronograph with a buddys' chrono of mine and another chrono at a clubs' 3D range I go to occasionally.
They are spendy little tools for sure.I could of just not bought one myself for those reasons.
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Just tested with 10gpp and it's in the high 160's. Hit 170 a couple of times. It was not as reliable with the heavier arrows. I'll paint the tips black and see if that helps.
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For a 27 in. Draw and that weight it's great !! speed still , how many strand string I assuming FF ?
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I recently went from 10 to 8 strand FF strings so I'm not sure but I think it's 8.
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OK I tested both chronos with the same bow and arrow 10gpp this time. If anything the new Caldwell reads 1or 2 fps faster than my old Chrony so I'm pleased with that. The Caldwell seems to have a bigger sweet spot so you get more results. I would estimate 80% positive results with the Caldwell as opposed to 50% with the Chrony. The Caldwell also has a cellphone app to record the results so you can look over them afterwards. With my Chrony you have to write them down as they happen. The Caldwell measured 170-172fps and the Chrony measured 168-170fps so thats pretty much a wash. I'm glad I got the new one. It's easier to use and it backed up the speed I was hoping I was getting.
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thanks for the update,, glad they both working,,
keep up the good work,, B (W