Primitive Archer
Main Discussion Area => Bows => Topic started by: upstatenybowyer on December 29, 2017, 07:54:07 pm
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I guess I must have been pretty good this year cause Santa brought me a chrony. O:) Anyway, I've been shooting away and getting some interesting results.
The fasted bow I've tested so far is that cherry-bark-backed mulberry I posted last week, shooting an average of 175fps. That one had just a touch of natural deflex with longer, gradual static recurves at the ends.
Coming in a close second was a hackberry static with short and sharp curves. I just finished that one up and haven't posted it. It's average was 172 fps.
Both of the above are 60# at 27#.
All the other bows I've tested were between 50 and 55# and were shooting between 155 and 165 fps.
I'm assuming these are pretty normal results?
Man, I'd really like to break 180 someday.
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I was wondering how long before you had everything's speed checked. Figure you know how fast the family cat was by now. How about your arrows? Are you going 10 g per lb? Or did you use the same arrows for all of them?
Bjrogg
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Nice numbers but I want to know the arrow weight too. ;D ;D ;D
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Well BJ, the cat moves at approximately 4 fps while chasing prey (B) ;D
But in all seriousness, this goes to show how clueless I am about arrows. :NN All I know is I used the same cedar shaft arrow for every shot. Guess I better start saving up for an arrow scale? :-\
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Glad Santa brought you a Chrony, it is fun to measure the arrow speed of your bows. Most of my bows (none of them recurved or backed) are typically ~67" n/n with draw weights at 60-70" and they clock in within the 155 to 165 fps range as well. Also measured with a Chrony and with arrows weighing in between 490 and 510 grains. So your speeds are in line with mine. My draw length is a maximum of ~26", so someone with a longer draw length would get higher speeds from the same bows.
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Congrats on your present I really enjoy using the Chrono and trying to tweak a bow for the finale fps it's a great tool , most of my arrows are heaver then 10 gpp for 45-47 lb bow but close enough that I can take a good guess ,chronos really make you think about mass placement !
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Grain scales aren't too terribly expensive, but if your household already has a kitchen scale (like, for weighing food), you can place your arrows on the scale and get a somewhat general idea of how much your arrows weigh. Just make sure you're using a scale that will measure in decimals and not fractions. I had a food scale once that only did Imperial measurements in 1/8 oz increments, so if I wanted to me more exact with my measurements, I had to weigh things in grams (oh the horror!!). Now I have a scale that will measure oz to .01, so life is good (in addition to having a grain scale now)!
Then, go to the good ol' Google machine when you have your weight and type in "convert x oz/grams to grains" and you'll have your weight in grains!
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Knowing that there are 437 grains in an ounce, or that there are 15.4 grains in a gram, a slide rule would be even faster than a calculator and exponentially faster than getting Google involved, IF you could find a slide rule and IF you knew how to use one. Call it primitive math;) I have a half dozen slide rules and they are the cat's meow for multiple calculations of ratios.
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Knowing that there are 437 grains in an ounce, a slide rule would be even faster than a calculator and exponentially faster than getting Google involved, IF you could find a slide rule and IF you knew how to use one. Call it primitive math;) I have a half dozen slide rules and they are the cat's meow for multiple calculations of ratios.
I need to get a slide rule and learn how to use it. I am forever doing one calculation or another. I carry a calculator in my pocket most of the time and keep a larger one in my car. I don't think I have ever really looked at a slide rule closely.
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Steve, I think the only sources for slide rules today are eBay and other second hand outlets. I'm pretty sure nobody makes them anymore. But they can be found. I like them for scaling mechanical and architectural drawings.
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Knowing that there are 437 grains in an ounce, or that there are 15.4 grains in a gram, a slide rule would be even faster than a calculator and exponentially faster than getting Google involved, IF you could find a slide rule and IF you knew how to use one. Call it primitive math;) I have a half dozen slide rules and they are the cat's meow for multiple calculations of ratios.
I know it's good to know the calculations, but if we can use modern tools, glues, and strings for our primitive bows, then why not break out the handy smartphone for your calculating needs! ;D
Between all of this, I hope upstate has a handy tool he can weigh his arrows with so we can know what his bows are clocking at.
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I do have a baby scale that measures in ounces and according to it the arrow I was using weighs 1.5 ounces. So perhaps it's safe to say it's a little over 500 grains?
So is the general rule of thumb to use arrows that weigh 10 grains per every pound of draw weight on your bow? i.e. a 50# bow should shoot 500 grain arrows?
I guess another question I have is how does speed play into these calculations? For example, what's a good speed for a 50#bow shooting a 500 grain arrow? And how much faster should one expect a 60# bow shooting a 600 grain arrow to be?
Sorry for all the newbie arrow questions guys O:)
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I think the general formula for how efficient your bow is something like this: you take the draw weight of your bow and add 100 and this number should be the minimum of the speed in feet per second a 10 grain per pound arrow is propelled. So... If your bow pulls 60#, then it should be shooting an a 600 grain arrow 160 fps. If it's higher, then you have a very efficient bow. If lower, then you overstrained the limbs.
Take this with a grain of salt, of course.
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I do have a baby scale that measures in ounces and according to it the arrow I was using weighs 1.5 ounces. So perhaps it's safe to say it's a little over 500 grains?
So is the general rule of thumb to use arrows that weigh 10 grains per every pound of draw weight on your bow? i.e. a 50# bow should shoot 500 grain arrows?
I guess another question I have is how does speed play into these calculations? For example, what's a good speed for a 50#bow shooting a 500 grain arrow? And how much faster should one expect a 60# bow shooting a 600 grain arrow to be?
Sorry for all the newbie arrow questions guys O:)
If your arrow weighs an ounce and a half, that's about 650 grains. But, when weighing something that light on a scale made for up to, what, 20#, you could be off by 40 or 50 percent.
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I bought a grain scale off the auction sight for 8 bucks. I have a chrono that is gathering dust, seemed hard for me to get consistent readings. Probably should fiddle with it some more. I think the biggest variable for me, other than lighting, was getting to the same draw length every time.
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Ty, that's an awesome general description of exactly the information I was hoping to gain. Many thanks brother.
Jim, I figured it isn't the best scale for this. The arrow is from set of 12 I got on the auction site. They came from China. I'm pretty sure they are around 500 grains.
rps3, I didn't realize you could find them for that cheap. I'll be looking for sure. The great thing about this chrony I got is that it has built in LED lights that make it really accurate. I get very consistent readings with slight variations that are probably the result of different draw lengths.
Since I make mostly 50-60# bows, sounds like I should have a set of 500 grain arrows and a set of 600.
Thanks as always for dropping the knowledge on me boys! :)
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what's a good speed for a 50#bow shooting a 500 grain arrow?
Just a little bit faster than the last 50# bow you made ;D ;D ;D
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The problem with chronos is with out a shooting machine or very consistent draw you get errors and no test standards when I post a final speed I only do it after I leave the bow strung for at least 1 hour and have a total of 300 arrows on the bow and shoot 12 arrows prior to test that way in my heart of hearts I know the numbers are real also you get faster readings in the winter months if you live where it gets drier in the winter, right now my RH gauge is reading 27 % in my storage room , I have seen as much as a 8 fps drop in speed after breaking in a bow ! But it's the best tool for knowing what your bow will do in field conditions !
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I bought a little digital scale for pretty cheap on ebay a few years ago. It measures in to the 10th of a gram and is still accurate. Then just x 15.43 on my phones calculator
Once you start to tune arrows to a bow you will probably see the numbers go up. I do consider 10gpp the standard arrow speed test.
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Cool. Thanks Chuck. :)
I bought a grain scale off the auction site today for $4 with free shipping. Hopefully it's not a total POS, but things are tight after Christmas and with both my kids bdays coming up within the next 2 months! :o
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That's a better deal than I got. It's easy to check the weight. If you don't have a test weight just use a nickel. They should be pretty much exactly 5g
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There seems to be a confusion between shooting 10 grains of arrow weight per pound of draw weight (gpp) and shooting a 500 gr arrow.
In TTB4, there's a chapter on bow testing ("turtle bow"). There, all bows are shot with the same 500 gr arrow, no matter the draw weight, no matter the draw length. There the expectation is that a bow is, on average, expected to shoot 100 fps plus its draw weight (pounds) in fps. So a 50# bow should shoot 150 fps to be average, a 60# bow should shoot 160 fps. The former is shooting 10 gpp, the latter 8.3 gpp. Performance is compared by looking at how many fps above the expected average draw weight each bow shoots. A 70# bow shooting the 500 gr arrow 175 fps (5 fps above expected) is doing worse than a 40# bow shooting 150 fps (10 fps above).
However, since the TBB series, we have learned a great deal about bow design, and I have the feeling we have increased the average bow speed. A 50# bow shooting a 500 gr arrow 150 fps is currently less than mediocre.
The other standard is shooting at 10 gpp and 28" draw length. There, every bow is expected to have the same initial arrow speed no matter the draw weight. A 30# bow shooting 300 gr arrows at 165 fps is performing equally well as a 60# bow shooting a 600 gr arrow the same speed.
It's pretty darn difficult to shoot faster than 175 fps at 28" and 10 gpp, even with a composite horn bow. Few are those that have achieved more than 180 fps at 10 gpp and 28" DL. I haven't.
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Interesting points joachimM. I do love having this new toy cause it gives me an idea of which bows are most successful. Then I can ponder what it is that worked and try to build off that. :BB
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Something that sometimes helps get you closer to the ballpark with digital kitchen scales is to put a weight on it an then zero it. So if your scale maxes out at 10 pounds, put a 5 pound weight on it and then zero it out. A canned food item can fit the bill.
On my kitchen scale if I do this I end up getting an additional 2 to 4 grams added on to the weight of heavier objects and 1/2 to 1 grams additional on lighter objects. Which is more accurate according to my digital reloading scale.
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I get about 160-170 fps out of a 50 # bow with a 500gr arrow. But I know there are bowyers out there getting faster readings. On occasion close to 175. That's when I do my job with a good stave. Arvin
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I have measured most of my bows. The fastest Bow in my collection is a bow from Marc. It is a 62" deflex reflex static recurve (HHB with ash backing) 48# @ 27". With a 475grains arrow and 27" draw I reached several times 180+ fps. With some other bows I reached 170+ and 175+ with the same gpp arrowweight and the same draw length. The bows are from Hickory,Osage,Osage backed with sinew.
But I dont shoot better the faster the bow is! I think velocity isn`t the key for better shooting.
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When you guys talk of arrow weights in terms of 10 gpp is that for a finished arrow with point or shaft weight? I assume it is for a finished arrow, but wanted to be sure.
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Good question Morgan. I assumed it's for a finished arrow too. I'm sure someone will set us straight...
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Finished arrow.
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Finished arrow.