Primitive Archer
Main Discussion Area => Bows => Flight Bows => Topic started by: JNystrom on September 08, 2017, 04:14:57 am
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I think the arrowhead discussion answered the questions, so let's make another topic.
Cp - center of pressure.
https://www.grc.nasa.gov/WWW/K-12/rocket/rktstab.html (https://www.grc.nasa.gov/WWW/K-12/rocket/rktstab.html)
Turkish arrows.
http://www.turkishculture.org/lifestyles/turkish-culture-portal/turkish-flight-arrows-554.htm?type=1 (http://www.turkishculture.org/lifestyles/turkish-culture-portal/turkish-flight-arrows-554.htm?type=1)
I don't have a very good method to analyze the center of pressure with my Primitive flight arrows. I do a little better job of this with my non-Primitive footbow arrows, by observing how they sink and shoot underwater. I can do this with arrows made of carbon and stainless steel components, but not with an arrow made of Primitive materials.
Probably the best advice I can recommend is to mark all your flight arrows with a permanent serial number and keep a log of how the arrows perform with different bows and shooting conditions. I observed some interesting things when I started doing this. First, I found that I had two or three arrows that were consistently the longest flyers, even if shot from radically different bows using radically different shooting styles. For example, I have one or two arrows that I found were used to set records for Modern Longbows 35 & 50lb), English Longbows(35 & 50 lb), and Primitive bows (35 & 50lb). Second, the arrows that matched the classic Turkish flight arrow geometry with the maximum thickness in the rear 1/3rd of the arrow were never my best performers. I have better luck with this shape if shot backward with the point where the nock should be, and nock where the point should be. Third, my high FOC arrows fly very consistent, but have not been the farthest flyers for whatever reason. They do seem to drill a deeper hole in the ground, but that is about it. Fourth, it is very important to pay a lot of attention to the fletching. Thick turkey feathers are the equivalent air-brakes.
Alan
Hope I am not going too far off topic, as this is not much about points anymore, but there are some good observations being shared in this thread about aerodynamics that I would like to follow up on. There might even be some erroneous statements also. I have to question my own assertation that the Cp moves in relation to the CG as the arrow slows down. The lift and drag forces that act at the Cp on the lever arm are reduced as velocity diminishes, thus lessening the ability of the arrow to restore itself to efficient flight, if disrupted, but I cannot see why the length of the lever arm would have reason to change.
A few different questions have been on my mind.....
1. what is the gliding effect that JNystrom mentions?
2. why did the reproduction turkish arrows that Alan made, fly better backwards?
3. why do high FOC arrows nose dive more at the end of the flight?
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Avcase,
I personally have just started to keep a log of all flight shooting. I mark the arrow serial number, weight, spine (deflection in 22" test, exact millimeters), length, balance point, thickness, fletching height and finally the distance arrow has travelled (every shot, not only the longest), the bow from which the arrow is shot.
Lots of info, so lets see how long do i have the patience to continue.
willie:
1) I may have just repeated others words, but i feel there is truth behind the speculation that back balanced arrow keeps itself in flying longer, than tip "heavy" arrow.
2) I haven't tested those 2" -FOC arrows of the Turks, but 1,5" -FOC arrows seemed to fly still ok. To the earlier question have i inspected any Turkish arrow, no way, i haven't seen any even reproduction of Turkish arrows. I live in Finland and well, for many reasons haven't been in any museum to check any. I have seen some of that style arrows made by a Finnish bowyer, with horn nock and pile, fletched with parchment.
3) Good guestion. Just because of gravity?
I don't know if you have visited this page, but it's full of nice information in terms of flight and it's aspects. http://www.tap46home.plus.com/mechanics/ (http://www.tap46home.plus.com/mechanics/)
For example the optimum calculated weight of the arrow, 60 grains???
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I think the arrowhead discussion answered the questions, so let's make another topic.
Cp - center of pressure.
https://www.grc.nasa.gov/WWW/K-12/rocket/rktstab.html (https://www.grc.nasa.gov/WWW/K-12/rocket/rktstab.html)
Turkish arrows.
http://www.turkishculture.org/lifestyles/turkish-culture-portal/turkish-flight-arrows-554.htm?type=1 (http://www.turkishculture.org/lifestyles/turkish-culture-portal/turkish-flight-arrows-554.htm?type=1)
I don't have a very good method to analyze the center of pressure with my Primitive flight arrows. I do a little better job of this with my non-Primitive footbow arrows, by observing how they sink and shoot underwater. I can do this with arrows made of carbon and stainless steel components, but not with an arrow made of Primitive materials.
Probably the best advice I can recommend is to mark all your flight arrows with a permanent serial number and keep a log of how the arrows perform with different bows and shooting conditions. I observed some interesting things when I started doing this. First, I found that I had two or three arrows that were consistently the longest flyers, even if shot from radically different bows using radically different shooting styles. For example, I have one or two arrows that I found were used to set records for Modern Longbows 35 & 50lb), English Longbows(35 & 50 lb), and Primitive bows (35 & 50lb). Second, the arrows that matched the classic Turkish flight arrow geometry with the maximum thickness in the rear 1/3rd of the arrow were never my best performers. I have better luck with this shape if shot backward with the point where the nock should be, and nock where the point should be. Third, my high FOC arrows fly very consistent, but have not been the farthest flyers for whatever reason. They do seem to drill a deeper hole in the ground, but that is about it. Fourth, it is very important to pay a lot of attention to the fletching. Thick turkey feathers are the equivalent air-brakes.
Alan
Hope I am not going too far off topic, as this is not much about points anymore, but there are some good observations being shared in this thread about aerodynamics that I would like to follow up on. There might even be some erroneous statements also. I have to question my own assertation that the Cp moves in relation to the CG as the arrow slows down. The lift and drag forces that act at the Cp on the lever arm are reduced as velocity diminishes, thus lessening the ability of the arrow to restore itself to efficient flight, if disrupted, but I cannot see why the length of the lever arm would have reason to change.
A few different questions have been on my mind.....
1. what is the gliding effect that JNystrom mentions?
2. why did the reproduction turkish arrows that Alan made, fly better backwards?
3. why do high FOC arrows nose dive more at the end of the flight?
Not sure how a rocket can be compared to an arrow since a rocket is under rear end propulsion while an arrow is in free flight
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Thanks for opening a new thread, JN. Lots of good reading for the weekend in that last link.
Once in a while I have an arrow or dart shot that seems to just float exceptionally before it falls, catches air as some say. A statistical outlier to the normal expected range variation. I thought perhaps there is another factor to the equation I am missing......... Lift that keeps the nose up? Allowing the trajectory to stay horizontal longer, in spite of the additional drag caused by the nose up attitude?
Alan, the arrows that fall short and dig in harder must land more vertical that the winning shots. What observations can you offer about the winners? Do they land on their sides or stick in the ground?
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Willie, very close to 100% of the arrows are stuck in the ground regardless of being a bad or good shot. Most of them are stuck at a higher degree than 45, some of the real bad shots are facing the wrong way.
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A model rocket is a lot like an arrow in a lot of ways. The same physics are at work. A rocket requires a little more stabilization, but it will fly stable as long as the center of gravity is forward of the center of pressure. There are a number of model rocket builders that have altitude competitions that resemble our flight archery competitions. The model rocket builders are also looking for that perfect balance of center of gravity to center of pressure. They need enough stability to keep the rocket on a straight upward path. An over-stable, point heavy rocket does not do as well because it tends to weathervane into every fluctuation of the wind currents that it passes through.
I do pay attention to the angle the arrows strike the ground. Every arrow seems to have a hard limit in how far it can be thrown. There comes a point where faster launch speeds from the bow makes little difference in how far the arrow can be thrown. If you start to notice the arrow starts landing at a very steep angle, like 75 or more degrees from horizontal, then this is a sign that the only way to progress is to work to improve the arrows. I experienced this first hand a couple of years ago at one of our Salt Flats events. I launched about 20 arrows from different bows over a wide range of launch speeds, launch angles, and wind conditions, and every arrow landed within +/-15 yards distance of each other! The arrows launched at high speeds went a little bit further, but landed almost vertically. The arrows launched at slower speeds landed at a little shallower angle, but still went nearly as far. It was as if there was an invisible wall that these arrows were not allowed to cross.
This led to a long process of trying to figure out how to break past this barrier. I was able to rule out atmospheric conditions by running into this same distance limit at completely different shoot locations and atmospheric conditions. I started playing around with arrow geometry and test shot my arrows alongside arrows made by past flight archers (arrows made by Harry Drake, Ike Hancock, and George Alavekiu). I found each of these groups of arrows had their own limits. Some were better than others. I considered an arrow topped out if it landed at an angle greater than 75 degrees. Faster launch speeds were a waste of time beyond this.
I even went as far as creating computer models of these flight arrows, and I used a fairly sophisticated model rocket program to shoot these virtual flight arrows at various launch velocities and angles. Funny thing is that these simulations showed the exact same symptoms that indicate the point of reaching the performance limits of a flight arrow.
The hard part is to figure out what to do to get the most out of an arrow. All I can say for certain is that there isn't a simple formula to make a great flight arrow. There are several factors that all interact with each other. I played around with several experiments to try to find some breakthrough. I tried an experiment shooting numerous arrows from a shooting machine that were identical weight, and identical nock and fletching geometry, but with different shaft geometry. Some were barreled with more thickness toward the rear, others barreled with more thickness to the front, others barreled with greatest thickness to the center. About the only consistent result from this indicated that the barelled arrows with more thickness at the rear performed worse than the rest. Also, arrows with more radical barrel tapering performed worse than arrows that had less radical barrel tapering. But it is kind of hard to isolate if this performance difference is due to the geometry differences, or due to shifts in the center of gravity due to the shape differences.
There's much more to this, but this post is long enough already. I will say that I did manage to break through the performance limit that I ran into a couple of years ago, but I am also sure there is still much to learn. For example, I cannot figure out how Harry Drake shot as far as he did using the equipment he had. I've ruled out the bows. They were very good, but not magic. It had something to do with his arrows and how they were shot. Pictures indicate Drake's record footbow arrows landed at pretty exceptionally shallow angles at distances exceeding 1-mile, but I don't understand how this was achieved. Drake's arrows were barreled with more of the thickness toward the front, and this pushes the center of pressure toward the front of the arrow. Drake's footbow arrows did not have metal points, but had a metal nock and steel razor blade vanes, which pushes the center of gravity rearward. My farthest flying arrows have similar properties, so maybe there is something to this.
Alan
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Very interesting post Allen, I enjoyed every bit of it. I also appreciate greatly the work you have done over the last decade and more. And congratulations on breaking the 1 mile barrier, that is a great achievement.
Arrow knowledge is the key to great flight shooting. My experience matches yours to a tee, it doesn't seem to matter what launch speed some arrows take off, they seem to have an upper limit. The best comprehensive approach to arrow design I could come up with was to rent an apt. near the flats and spend about a year their making and shooting arrows. The few arrows we launch each year for distance are not enough to tell us much if anything. At this time I am favoring slight tapers from front to back, no opinion on spine I really need to work on that, I have had some good flyers from arrows I thought were weak but I have also had some good flyers from arrows I thought too stiff.
I could pull my hair out just thinking about arrows!
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Great thread from everyone, great post Alan
Del :)
(Mrs Cat has vetoed the wind tunnel in the living room ;) )
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That's good idea to check the arrow angle at ground level! If the arrow angle changes quickly, shouldn't this be because of,
a) too much drag
b) too much FOC
?
In extreme, badminton ball leaves fast from the racket, but drops fast like hitting the imaginary wall. Because of drag and low mass.
Shouldn't one always use vellum vanes only if he want's to shoot far? They surely are thinner and have less drag. I don't have any yet, so i would be interested in trying paper vanes saturated with superglue, which should act similary.
Yep, it's excellent we have a discussion about flight arrows! Its always bows, bows.
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Great post fellas.As just an interested observer of the knowledge commented here way more then my experience for this competition but making my own arrows.The greater front of center degree I thought was mostly for better penetration reasons hunting without any concern for distance.With not as much concern for the extra stiffness needed on the shaft flight shooting too.
My related thoughts when making arrows with more front of center degree were of a javeline being thrown for farther flight though.A javeline is very front heavy.
Arrow making for this competition is far more involved then just making hunting arrows.
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I have had my best distances, well past world record in the 50# classes with very average bows. Just by chance an arrow came out clean and flew well. The arrow is a huge part of the equation. I am convinced that the best strategy for working out the mysteries has a lot to do with shooting a lot more arrows of different designs at least until recognizable patterns start to emerge. We know drag is a bad thing but the jury still seems to be somewhat out on the perfect shape of an arrow and the best way to get an arrow out of a bow. I do believe we have a pretty good idea on these things that just needs some fine tuning. More shooting, shooting, shooting!
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Steve,
I agree. There is no substitute for going out and shooting. I often use the theoretical ideas to help target areas to explore with real world testing, and I use discoveries from real world testing to understand the limititations and improve the theoretical methods.
I feel there is a lot be learned about arrow flight. There really hasn't been a lot of research into the way we are trying to apply aerodynamics to a flight arrow. Especially where beneficial drag might be concerned. An arrow is not quite like a bullet or a rocket. An arrow is unlike fin stabililized armor piercing projectiles due to the lower velocity and due to the fact that we are not necessarily trying to punch as deep a hole as possible into the ground. Same goes for gravity bombs. We are able to learn a lot from these other applications, but there is much to be learned on our own as well.
Alan
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Alan and Steve,
the sharing of your experience(s) at the flight line and observations are appreciated, and make much food for thought.
"Especially where beneficial drag might be concerned." brings to mind some other innovative drag applications
1. some ideas seen in javelin development
http://www.symscape.com/blog/engineering-in-sports-javelin-throwing
2. a review of some primitive ideas used on harpoons (for extended glide underwater)
https://kayakgreenland1959.wordpress.com/look for winged harpoons about 4/5 down the page
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I used to throw javelin in high school. They used to be less point-heavy than they are now.
I am not finding the info on the harpoon but I think seems pretty interesting. I suppose it isn't possible to post a direct link here.
There is a water toy called a toypedo that will provide hours of entertainment in the swimming pool and get you thinking about flight arrows.
There has been a lot of unresolved discussion about the potential of beneficial drag with flight arrows. Is it better to give the arrow a polished surface, or leave it somewhat rough? I think it depends on a few different things. I can see how it might be beneficial to trip the boundary layer with some roughness on a longer arrow, but it with a very short arrow, it may be better to give it a highly polished surface in order to preserve as much laminar flow across the surface of the arrow as possible. those that compete and win model rocket altitude contests go with a polished surface. I will take a look through my best natural material arrows and see if there are any common traits worth sharing. It has been awhile since I really looked through them closely.
Alan
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https://kayakgreenland1959.wordpress.com/category/yak-1959-three/
about halfway down the page
his blog contains the same info in a few places, as one post seems to be an edit of another
In looking over article and tables from the Journal of the Society of Archer-Antiquaries, volume 4, 1961 article, I noticed that...........
"in some cases lead was inserted in a hole drilled in the bottom of the nock to bring the balance point........".
and that the balance point of the sampled arrows always coincides with the maximum diameter, and occurs at 55% (plus/minus 1%) back from the tip. These arrows are very similar, almost too similar?
Has anyone seen sources of info on different/other turkish arrows that show some variety? or is the turkish design that consistent?
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I think there could be some errors in the measurements of the Turkish Flight arrows. I would expect at least some minor difference between the center of gravity and the maximum diameter. It would be great if there are other measurement data on these types of arrows available.
The long taper to a very tiny point like the flight arrows in the Archery Antiqueries article have never worked very well for me. I am not sure why the Turkish archers adhered to this standard so rigidly. The shape of these arrows are probably driven by other factors such as shooting technique and attempting to get the most stiffness out of the lightest arrow possible. I am not that well educated in the history behind Turkish flight archery, so I am just guessing.
It looks as though the wings on the harpoons serve a function similar to fletching on an arrow.
Thanks for the links.
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I dug through my stash of natural material flight arrows and pulled a couple that have consistently outperformed the others.
They are in pretty rough shape after 8-9 years of flight shooting. Let's see if the images post okay...
(https://flic.kr/p/YrvVdo)
(https://www.flickr.com/photos/farflinger/37044728666/)
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Hoping to see the pics, but cannot, even after your edit. Perhaps It's just my setup. Can anyone confirm if they are visible?
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I don't see anything
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I think I have the way to post pictures finally figured out.
Both are split cane. The top one is 23" long, 23" long, and a maximum diameter of 0.215". The bottom one is 26-1/8" long, 212 grains, with a maximum diameter of 0.234". Balance points for both are just behind the center of the arrow. I am not sure why these have shot so well out of a such a large variety of bows. They totally contradict my earlier statements that the classic Turkish shaped arrow was not the best performer for me, are they are not even very straight! Hahaha!
(https://farm5.staticflickr.com/4332/37044728666_4a9f7d1caa_z.jpg)
Alan
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Nice arrows! What is spine of the arrows? How much they are bending for example a 2# weight on 22" centers, or something like that?
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I rarely spine test the flight arrows the usual way. My spine test usually consists of balancing the arrow on my finger tip, tapping it, and listening to the frequency it naturally rings at. I can try to measure the spine of these the normal way and let you know, but it doesn't seem particularly high.
I figure I may as well post more detail now that I finally figured out how to post images here:
Metal point on the smaller arrow is about 1/8" diameter.
(https://farm5.staticflickr.com/4381/36397676594_6239bd7f98_z.jpg)
(https://farm5.staticflickr.com/4395/37044767556_b9b7ffdc9d_z.jpg)
The nocks are reinforced with thin silk thread soaked in hide glue. It hasn't held up well to moisture. Fletches are stiff but thin, and are either duck or goose. Pheasant tail feathers are another favorite.
Alan
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I think I have the way to post pictures finally figured out.
Both are split cane. The top one is 23" long, 23" long, and a maximum diameter of 0.215". The bottom one is 26-1/8" long, 212 grains, with a maximum diameter of 0.234". Balance points for both are just behind the center of the arrow. I am not sure why these have shot so well out of a such a large variety of bows. They totally contradict my earlier statements that the classic Turkish shaped arrow was not the best performer for me, are they are not even very straight! Hahaha!
(https://farm5.staticflickr.com/4332/37044728666_4a9f7d1caa_z.jpg)
Alan
I'm in the dark about making flight arrows but split cane?From the sidewalls of thicker walled bamboo?Maximum diameter of under 1/4"?If so they should be pretty darn stiff I'd think but what do I know.Nice arrows BTW.
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The split cane flight arrows are made from six splits off a Tonkin Cane bamboo culm or stalk that are shaped and glued together to form the arrow shaft. The process is the same as used to make a split cane bamboo fly rod.
Deflection of the 26-1/8" long flight arrow shown above is about .57 inches with a 22 inch span and 2-pound weight. So stiffness is similar to that measured on old Turkish flight arrows. A good spruce flight arrow would have to be about 0.313" diameter to match the spiny/stiffness of the 0.234" diameter split cane flight arrow.
This is interesting. The weight for my larger diameter spruce flight arrow and equivalent stiffness of the split cane Tonkin arrow is almost identical.
Alan
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I am getting an itch to build some arrows for distance shooting. Wading thru the physics and aerodynamics at present, quite a complex and fascinating study. Maybe I can apply some old learning about fluid mechanics, to a new endevor, now that I have the time.
Just curious if any shooters can comment on shooting flight arrows at lesser angles or bow poundages. Having a suitable range nearby, where one does not loose too many arrows, seems to be desirable.
Thanks for taking the time to post your work, Alan. I am surprised to learn that some of your arrows "have shot so well out of a such a large variety of bows." Seems to speak more to the qualities of the arrow it's self, than some of the exacting particulars of a bow, or how it is tuned.
And thanks for posting the spruce specs, as I am keeping my eye out for some primo local wood.
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I made several flight arrows out of HHB many years ago, they were quite small in diameter. I tried a carbon arrow to see if it would shoot farther than the HHB arrows, it did not. My HHB arrows shot fairly consistently at around 330 yards and the carbon arrow fell at least 10 yards shy, consistently.
P.S. Forgot to mention that the carbon arrow at about .25" was roughly the same diameter as the HHB arrows
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Marc,
Anything over 300 yards with a primitive bow is really good! I wonder if the worse performance of the carbon arrow was mostly tuning related? The carbon arrow should be a lot stiffer than the wood arrow if the diameter was close to the same. Those must be pretty impressive wood flight arrows to work so well at only 0.25" in diameter!
I believe my Sitka spruce arrows would really shine if I could keep them from rehydrating after heat treating them.
Alan
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Thank you for all the information, this is really interesting subject!
Alan - what do you mean saying "these have shot so well out of a such a large variety of bows". So, what kind of bows? Which poundage and draw length?
And why do you believe, your heat treated spruce arrows would shine without rehydration - because of lower mass or higher spine or some other reason?
Third question - why those two arrows are so special? Have you compared them to similar arrows, which are not so good? Is there any kind of measurable difference? You have made a lot of split cane arrows but what makes some of them special? Spine, weight, diameter, balance point, some parameter we don't know yet?
I am going to make some new flight arrows. My last batch was not so good... I have some POC shafts, 5/16", 63# and 400 grains (full length). I will get also some spruce shafts, which will be 5/16" and over 60#. Should be good raw material.
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I am not sure what traits I can isolate about these flight arrows that would explain why they have had such a long history of performing as well as they have. The only reason I even realized that these two arrows were repeatedly the best performers is that I started engrave each arrow with a unique serial number, and this serial number is registered at our flight tournaments and cross-referenced to the distances measured.
Here's a quick summary:
The larger arrow:
50lb & 70lb Modern Longbow record
50lb Primitive Simple composite record
50 pound Women's English Longbow records
35 pound Junior Woman's English Longbow record, which still exceed the adult men's & woman's 35 pound English Longbow records.
Shorter arrow:
50 pound men's Primitive self bow record
50 pound Women's primitive self bow record
35 pound primitive simple composite record
35 pound Modern Longbow record
Willie,
I hope you build some flight arrows and give it a try! There is almost no end to it once you get started hahaha! It seems like there is no end to the learning curve.
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Thanks for the encouragement, Alan.
If I am reading what you said abut the longer arrow correctly, It broke a record in both a 75# class and a 35# class (and bested two other 35# classes with that shot)?
I would assume that many records are broken by shots that are only marginally longer than the previous record, but am curious how often a surprisingly exceptional shot occurs, a jaw dropper, so to speak.
I am suffering from some wishful thinking about what JNystrom was referring to earlier as the "glide effect".
There seems to be something that sets some arrows apart.
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And why do you believe, your heat treated spruce arrows would shine without rehydration - because of lower mass or higher spine or some other reason?
Third question - why those two arrows are so special? Have you compared them to similar arrows, which are not so good? Is there any kind of measurable difference? You have made a lot of split cane arrows but what makes some of them special? Spine, weight, diameter, balance point, some parameter we don't know yet.
I heat treated some Sitka spruce shafts in an oven set at 375 degrees f for just long enough that the color of the wood began to darken a slight amount. The stiffness of these arrow shafts were incredibly high afterward, which is just what I look for in an an arrow shaft material. Unfortunately, much of this benefit faded away over the next week as the arrow shafts regained moisture.
I will have to carefully look through all my flight arrows to see if I notice some traits that the best arrows have in common. It doesn't seem very obvious to me right now.
Alan
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It is very interesting that one arrow functions well with 35, 50 and 70# bows. It seems that fine-tuning of bow-and-arrow is not so important. There has to be something else.
If release is good and arrow is leaving bow well and supposing that speed is same between different arrows, then the only discriminating thing is how the arrow is flying. We can measure speed of arrow, see how it is behaving at release but don't see how it is flying. Maybe there is something what you said about landing angle.
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A good arrow you can't see at release at all they just disappear. Any arrow you can see is a bad shot it seems. About 320 yards is the maximum I have ever gotten for an arrow I could see leave the bow and track for some distance.
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A good arrow you can't see at release at all they just disappear. Any arrow you can see is a bad shot it seems. About 320 yards is the maximum I have ever gotten for an arrow I could see leave the bow and track for some distance.
That disappearing arrow obviously leaves the bow cleanly and fast. BUT that doesn't mean it still can't have too much drag to slow it down and fast. Right? Not that it would be the case everytime, but just as a minor point.
I think those arrows Alan Case shoots from 30# to 70# pound bows, can't possibly leave all of the bows super cleanly (because of different spine), but still maintain their flight for "quite" :D long.
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I think those arrows Alan Case shoots from 30# to 70# pound bows, can't possibly leave all of the bows super cleanly (because of different spine)
Perhaps the tapering in the rear half helps more than one would presume?, although that's quite a bit of range.
Alan, in addition to citing the poundage range you have had good luck with, could you comment on the handle widths of the bows in question?
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I think that it's the speed of the arrow rather than the poundage of the bow that determines the spine. In order to get to say, 180 fps the arrow has to accelerate at a certain rate. There is more involved than just bow draw weight. I believe that if you have a 70# bow that has a dry fire speed that is the same as a 30# bow the same spine arrow will work in both.
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you might have hit on something with that observation, DC. Axial force is a function of acceleration.
I have been thinking of what constitutes a "clean release". If an arrow leaves the string with the nock in-line with the direction of flight, then what could be better? Of course how much an arrow nock oscillates laterally is both a function of the arrows stiffness and the displacement of the string rolling off the fingers.
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I wasn't the archer or bow builder for any of the flight records shot with the arrows I posted earlier. I was just the arrow guy. The bows were built by Steve Gardner, Dan Perry, and Larry Hatfield. The English Longbow records were shot with a couple of hickory-backed Ike bows that are just under 3/4" wide at the handle (no cut-in arrow shelf, of course). Steve can best comment on the degree of center shot his self bows and simple composite bows have. They usually have a shelf cut in to the handle. I think it is not quite to center. Same for Dan Perry's bows. Larry Hatfield's Modern Composite Longbows have a shelf that is cut in close to center, which still leaves the arrow off center by some amount.
Alan
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This is interesting. The weight for my larger diameter spruce flight arrow and equivalent stiffness of the split cane Tonkin arrow is almost identical.
Alan, are you saying the spruce and tonkin arrows spine about the same, and weigh about the same? Just the diameters differ?
.57 deflection 22" O.C. seems soft, especially for a 75# bow. Seems like the bows you mentioned did not necessarily need to have the arrows spined as soft as they are for getting around the handles. As a generality, are most flight arrows sacrificing as much spine as possible, for the aerodynamic advantage of having minimal diameter?
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I'm sensing a Mass Principle for arrows.
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Willie, say you have a 70# bow with a 125 grain tip on it. You would want about 70# spine. Take away the tip and now you need 45# spind, take away about 100 grains of arrow mass from the front of the arrow and now you are down to about 30# spine. You don't need much spine for flight arrows. The spine protects against the weight forward of center that the arrow is trying to accelerate. If there is not much weight up front you don't need much spine to still be stiff.
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Alan, are you saying the spruce and tonkin arrows spine about the same, and weigh about the same? Just the diameters differ?
.57 deflection 22" O.C. seems soft, especially for a 75# bow. Seems like the bows you mentioned did not necessarily need to have the arrows spined as soft as they are for getting around the handles. As a generality, are most flight arrows sacrificing as much spine as possible, for the aerodynamic advantage of having minimal diameter?
Yes, the primary difference between the spruce arrow and Tonkin Cane arrow is that the spruce arrows are a bit larger in diameter.
It is most important to have clean arrow flight out of the bow. An arrow that wiggles too much or comes out of the bow at an odd angle doesn't go very far. Especially if it is a very light arrow.
The "floating arrow" topic is an interesting one. I am still not sure how effective it is or how well it can be controlled, but I can try to show what I think is going on with some of these arrows using a rocket flight simulator.
Alan
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I am seriously thinking a change in strategy. Longer bows, longer arrows more stored energy and heavier arrows. At around the 250 to 280 range they become a little more consistent even though they might be quite a bit slower. I know ranges are more consistent at that weight. The lighter arrows always have that chance of an outlier that took off clean and stayed straight but I don't like gambling on it so much anymore. Maybe use a range of arrows from 200 to 270 grains.
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I'm sensing a Mass Principle for arrows.
Well my wife has a 20 " draw and getting target arrows for 35# draw draw weight that come in at 264 grains is not difficult if you can spine them . My spine tester required 26" arrow. So I got a hundred 1/4" by 24" shafts and weighed them , grouped them and built arrows from different groups. The ones that weighed in the 264 gr. Total weight shot the best. That being said I tried this to see if weight of arrrow could give you spine. I used same point and fletchings set up on the different weights of shafts. It seamed to work for the most impossible client,. ;Dh Arvin
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I am seriously thinking a change in strategy. Longer bows, longer arrows more stored energy and heavier arrows. At around the 250 to 280 range they become a little more consistent even though they might be quite a bit slower. I know ranges are more consistent at that weight. The lighter arrows always have that chance of an outlier that took off clean and stayed straight but I don't like gambling on it so much anymore. Maybe use a range of arrows from 200 to 270 grains.
My 2cts: will a bow that stores more energy shoot farther if the dry fire speed is the same? I wouldn't think so. Energy storage and bow efficiency are not the bottlenecks in flight archery. However, heavier combos may be at an advantage if you can shoot heavier arrows at the same speed as light arrows. The reason is that the one thing we cannot scale up or down, is the physical environment. Light arrows experience the same air density as larger heavier arrows, but relative to their mass they experience more drag because the air in which we shoot is the same. Put otherwise, heavy arrows shot at the same speed have more energy to push away the air in front of them. All else being the same (but scaled up, say 25%), heavier combos should shoot farther.
To reduce drag, we shoot the shortest and thinnest arrows possible, but the trade-off is less energy per arrow. The other option is to choose heavier and slightly longer arrows. This will indeed require scaling up the bows.
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Theoretically, if the dry fire speed is the same, then then will both only shoot a 0 grain arrow at the same speed. As the arrow weight increases the bow that stores more energy will take the lead. But that's only my 2cts worth. :D :D
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dry fire speed isn't about theoretical 0 grains arrows, it's the speed at which reducing arrow mass doesn't yield higher initial velocity. It may be that the dry fire speed of two bows is identical, one with 250 grain arrows, the other at 350 grain arrow. The heavier arrow will fly farther, because of its higher energy content (energy = mass times velocity squared).
With the same bow design, identical dry fire speed at higher arrow mass requires a larger bow, hence scaling up the bow.
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dry fire speed isn't about theoretical 0 grains arrows, it's the speed at which reducing arrow mass doesn't yield higher initial velocity. It may be that the dry fire speed of two bows is identical, one with 250 grain arrows, the other at 350 grain arrow. The heavier arrow will fly farther, because of its higher energy content (energy = mass times velocity squared).
With the same bow design, identical dry fire speed at higher arrow mass requires a larger bow, hence scaling up the bow.
Dry fire speed is just that, dry fire speed, there is no lower limit where they quit getting faster as you lighten the arrow. If there is close to one it is way below an practical arrow weight. I have tested them down below 100 grains and they keep getting faster.
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Theoretically, if the dry fire speed is the same, then then will both only shoot a 0 grain arrow at the same speed. As the arrow weight increases the bow that stores more energy will take the lead. But that's only my 2cts worth. :D :D
Energy storage isn't the big factor when dealing with light arrows, efficiency is the big one. Higher energy storage along with efficiency is a good thing especially when it allows you to shoot a heavier arrow at a desired velocity. As arrow weights get lighter the gap in speed between high energy storers and highly efficient bows starts narrowing. Eventually the more efficient bow will overtake the higher energy storing bow unless they are just too far apart to begin with.
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It seems the point I was trying to make is missed here, as it's not about dry fire speed per sé. It's that, IMO, a heavy arow shot at the same initial velocity will fly farther than a light arrow, because, unlike bow and arrow dimensions, air density (and thus drag) cannot be scaled up or down, it remains the same.
But it's close to the obvious, since we already know heavy flight bows shoot farther than light flight bows...
This said, can you explain, Steve, how you think larger bows and more energy storage will aid flight shooting?
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This is a good conversation, I am going to pour my heart out archery fashion.
One of the reasons I am thinking of going toward longer bows, longer arrows and more energy storage is basically to compensate for inadequacies in my arrows and release techniques for clean arrow flight. I am not so sure about the longer arrow but I know heavier arrows carry much better and are more forgiving. The greater potential I believe is still in the shorter arrows.
One thing that I have only recently appreciated the importance of in recent years is our ability to lower hysteresis in wood bows. The lighter you arrow gets the more significant this becomes. Normally a very well built self bow with a little reflex would usually hit around 172 fps at 10 grains per pound, by controlling set and lowering the hysteresis that number can suddenly jump into the 180's with a bow of identical unstrung profiles. This won't happen every time but if you get everything right you will get some of these super shooters. When it comes to light arrow shooting the lower hysteresis is even more significant and can add over 30 fps to a 200 grain arrow, that might give you 100 yards. I am pretty sure 50# wood bows will eventually hit 450 yards. With the longer arrows and bows I am hoping for shots in the 375 to 380 yard range. Finding a place to practice often, at least a dozen times a year I think would help immensely.
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THE ONES YOU CAN SEE LEAVE vs. THE ONES YOU CAN'T
Badgers observation and comment seems sensible. The short reason is of course, "aerodynamics". The links posted earlier seem to categorize drag values as being highly dependent on whether the airflow past an arrow is considered "laminar" or "turbulent". For a look at the desirable low drag laminar flow around a point, see the pics in
http://sci-hub.bz/10.1177/1754337111430569
Also of note is the assertion that a typical arrow shaft has air flow that is neither laminar nor turbulent, but transitional, (primarily because of its diameter to length ratio). Although airflow may start out as laminar, there appears to be an increasing amount of drag caused by growing turbulence, the further down the arrow shaft you look. The distance from the point that this turbulence begins, and when it occurs during the arrow's flight could be enough to separate the winners from the losers.
The tradeoff/strategy Badger mentions, heavier arrows vs lighter arrow, certainly could be viable on account of the ability to launch a heavier stiffer arrow more consistently. Yaw or angle of attack is a large predictor of point drag when the flow is considered laminar. In this study, after about 3 degrees, it is essentially the same as if the flow was turbulent. See graph 7
https://www.researchgate.net/publication/241124001_Aerodynamic_properties_of_an_arrow_Influence_of_point_shape_on_the_boundary_layer_transition
For whatever reasons turbulence forms (and there are a few more like surface smoothness, wind gusts, etc.), It is unclear (to me) how easy or hard it is for turbulence to subside, once the smoother flow has been disrupted.
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WIllie,
I haven’t run across that article before. That’s a good one that I will have to read through carefully. I thought the comment about the observation of arrow vibration induced by aerodynamic turbulence was interesting.
I have found a trend that shorter arrows do better than longer arrows with my footbow. These also have a very smooth and polished outer surface. In this case, the arrows are released with a mechanical release, which eliminates a lot of the tuning issues that come with a finger release.
On the other hand, the split cane arrows I posted about earlier are far from being smooth or polished.
Thanks!
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I am starting to think a key design feature on a flight arrow might be in it's ability to recover as fast as possible from release. I think Allen had some discussion on this a few years back. A 150 grain arrow can easily leave a 50# wood bow at 250 fps but will not tolerate any sideways motion without loosing most of its velocity. What qualities enhance rapid recovery from slight inconsistencies in release.
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I think that it's the speed of the arrow rather than the poundage of the bow that determines the spine. In order to get to say, 180 fps the arrow has to accelerate at a certain rate. There is more involved than just bow draw weight. I believe that if you have a 70# bow that has a dry fire speed that is the same as a 30# bow the same spine arrow will work in both.
Exactly... it's acceleration that flexes the arrow. I've had 50# spine arrows shot from 120# warbow no prob'...
Mind when I mentioned it on a FB warbow thread I had some bloke who couldn't understand it calling me an idiot ::) . It's sad 'cos the guy didn't even realize how little he knew !
Del
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I am starting to think a key design feature on a flight arrow might be in it's ability to recover as fast as possible from release. I think Allen had some discussion on this a few years back. A 150 grain arrow can easily leave a 50# wood bow at 250 fps but will not tolerate any sideways motion without loosing most of its velocity. What qualities enhance rapid recovery from slight inconsistencies in release.
Yeah, it must be springy enough to recover quickly but not to resonate and keep oscillating, so it needs damping... maybe bamboo stuffed with Christmas pudding? ;)
Del
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maybe bamboo stuffed with Christmas pudding?
Have not tried the pudding yet Del, but I agree about the oscillations and dampening. A thread in the arrow section has a few links to interesting footage of arrows and darts in flight, focusing on those ocillations.
(the recent discussion and links start with Reply #26) http://www.primitivearcher.com/smf/index.php/topic,61394.0.html
I have been experimenting with primitive tapers on Atlatl darts. . The tapers I have tried are copied from darts found in melting ice fields in Yukon Territory that are between 3200 and 4500 years old. A good dart release is not easy, on account of the pronounced lateral displacement of the nock that an atlatl spur creates. Soft spines are required, stiff darts do not fly well at all, and tapering can change the location and timing of the oscillations quite a bit.
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I have thought about this same thing with the darts, I am not that good with darts but played around with them some and was amazed at how much difference the proper spine makes. I was able to throw a little over 100 yards with a not so hard throw once I got my spine figured out. You could visibly see it oscillate. Intuitively I would think that once they are on the right path the oscillations don't really help but there was no question that my softer spines took off and flew better. I think it was easier for a beginner to get a clean throw.
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Arrow flex is always a necessary evil with finger release and degree of non-center shot. A wiggling arrow experiencing a lot of excess drag in the early part of its flight, so it’s best to find ways to avoid as much as possible. When it comes to damping our vibrations, I don’t know what may work best. Big fletching helps, but adds lots of drag.
Once the vibration damps out, the air flow boundary layer should start to reattach and become laminar toward the front couple of inches of a polished arrow.
My best arrows are higher density at the point and nock, and light and stiff in the center. It seems like this should be worse for a shot that leaves the bow misaligned, because the arrow has high inertia for the fletching to overcome. However, this higher inertia should be better if we are talking about a “floater”. ;)
Alan
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Alan, are you still describing your bamboo hex shaft arrows, where the outer skin on the bamboo is presumably denser than the interior?
It seems like this should be worse for a shot that leaves the bow misaligned, because the arrow has high inertia for the fletching to overcome.
The inertial force causing yaw?
I have been giving some thought to similar mass distributions, ie, heavier footings, both front and rear, or both, on some designs I hope to make soon.
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Alan, are you still describing your bamboo hex shaft arrows, where the outer skin on the bamboo is presumably denser than the interior?
It seems like this should be worse for a shot that leaves the bow misaligned, because the arrow has high inertia for the fletching to overcome.
The inertial force causing yaw?
I have been giving some thought to similar mass distributions, ie, heavier footings, both front and rear, or both, on some designs I hope to make soon.
Willie,
Yes, I was referring to the split cane bamboo arrows. I leave the thickness of the wall thinner in the middle and thicker at the ends. It is a similar effect as footing a wood shaft at each end.
Alan
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"It is a similar effect as footing a wood shaft at each end"
"However, this higher inertia should be better if we are talking about a “floater”".
Alan, Do you have a hypothesis for why such a mass distribution might act this way? Maybe the "high inertia to overcome" works both ways? Once the arrow gets going straight the end weighted arrows are harder to disrupt from straight flight?
Just a guess on my part.
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"It is a similar effect as footing a wood shaft at each end"
"However, this higher inertia should be better if we are talking about a “floater”".
Alan, Do you have a hypothesis for why such a mass distribution might act this way? Maybe the "high inertia to overcome" works both ways? Once the arrow gets going straight the end weighted arrows are harder to disrupt from straight flight?
Just a guess on my part.
There is a disadvantage in the initial flight of a higher inertia arrow since it takes more fletching action to get a misaligned arrow on course. But, once on course, it should want to stay there.
The trajectory of the arrow is also constantly changing the direction the arrow travels. This requires the arrow to be redirected, particularly as the arrow approaches the descent portion of the trajectory. At the top of the trajectory, the arrow speed has slowed, and the center of pressure starts creeping forward closer to the center of gravity of the arrow, reducing stability.
If the arrow has zero spin, this increasing misalignment with the arrow to the trajectory will create a reactive force in the fletching, forcing the arrow to start pitching down. It will usually overreact, requiring the fletching to react the opposite way, and the arrow pictches nose up again. This pitching up and down continues until the arrow has regained speed on the way down. This is not a good thing, and probably a major reason why distances sometimes suffer with arrows that have a CG behind center.
But, what happens if the same arrow is shot again at the same angle and speed, except the fletching is changed to induce a mild amount of spin?
It takes awhile for the arrow to spin up, during which time hopefully most of the launch misalignment issues are sorted out. But as the spinning arrow arcs across the top of its trajectory, the rotation of the arrow should be just enough that it doesn’t start pitching up and down. Instead, it reacts more slowly to the changing trajectory path. In other words it is descending a bit nose up, causing drag. This drag slows the descent, keeping it in the air longer and giving it more time to travel a little farther before it picks up enough speed that the fletching becomes more effective again and forces the arrow back into closer alignment with the trajectory.
I don’t know if that makes any sense.
Too much spin combined with not enough aerodynamic stability will create too much drag and can lead to excessive angles of attack on the descent. This can cause the fletching to stall and loseeffectiveness, and the arrow will turn 90 degrees and fall to the ground. This is not good either.
Alan
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So having the mass distributed towards the ends of the arrow seems to attenuate pitching (as does the spin), or helps the arrow to keep it's nose slightly up with less spin? Quite a lot to consider when one wants the arrow to "float" at the top of its trajectory, seems like lots of tradeoffs when the COG is so close to the CP (center of pressure).
On a different note, I was reading about FOC experiments done by Clarence Hickman. I cannot find the full text of his paper, just this synopsis from Barry Groves. With all fletch sizes, distance fell slightly as the CofG moved backwards. With the CofG behind the center of the arrow, the distances achieved fell markedly. The greatest distance he achieved was with the CofG at 32% and the arrow unfletched.
(CofG is percentage of total arrow length that COG locates behind the point, not FOC).
Can you comment if this has proven out in any of the flight records? Or are any shooters competitive with arrows designed around the high FOC/minimal fletching concepts.?
Thanks for taking the time to share, Alan. Almost every thing I have read about arrow exterior ballistics admits "not much has been researched" about arrow flight.
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It’s funny that I just Hickman’s report on his FOC experiment last night. Hickman created an arrow with an internal weight that he could adjust to shift the center of gravity of the arrow without affecting its shape. The arrow was initially fletched with large straight-fletched feathers that he could trim down to see if the fletch size affected anything. The bow was set in a shooting machine with a mechanical release and set at 45 degrees. Hickman used a pretty light bow and the arrow was pretty heavy in order to keep the distances within reason (less than 140 yards for the farthest shots). The procedure was as follows:
With the full size feathers, shoot several times with the weight forward to give a high forward balance, then neutral balance in the center, than rearward balance. The distances were recorded for each shot.
Then he would then trim the feathers down and repeat the shot sequence and measure the distances. He continued this to the point where he was shooting a bare shaft with no fletching at all.
Hickman’s results showed that there was little difference in distance for different FOC with the large fletched arrows. But as the fletching was reduced, the shots with the forward center of balance out distances the arrow with rearward center of balance. At yet smaller fletch size, the arrow with rearward balance was completely unstable, and the forward balance configuration outdistanced the center balance configuration. Finally, with no fletching, only the forward balance configuration flew stable.
It was also no surprise that the distance of the farthest flying arrow increased as fletching size was reduced. The farthest shots of the test were with the unfletched arrow with a forward center of balance. He concluded that the floating arrow theory was busted and that a rearward CG was not beneficial to long distance arrow Flight.
But there was one important detail missing in his experiment. Did you happen to notice what that was? ;)
Alan
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My first thought would be how various speeds affected the arrows but that was not part of this test. Good question? Fun trying to figure out what he forgot.
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He didn't use medium settings of balance, only the extremes and center.
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Going out on a limb here. The arrow was not barrel tapered. Arvin
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Going out on a limb here. The arrow was not barrel tapered. Arvin
what arvin mentioned, and not sure how hickman accounted for changes in dynamic spine in his continuously modified test arrow
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Okay, here is where I think Hickman may have missed something. I didn’t see where he included the effect of arrow spin. A straight fletched arrow with little to no spin should do just what he reported. It should get a little erratic as the fletch size is reduced and weight moved rearward.
I am actually not yet completely sure that moving the center of balance rearward and inducing a moderate spin is a good strategy for longer arrow Flight, but I do think I too is worth investigating further. I have seen some evidence of this with my foot bow arrows. The nose-heavy arrows flew predictably, and buried themselves deep in the ground. The arrows with their center of gravity further rearward landed more erratically, and often didn’t go any farther. But when I induced a small amount of spin (by altering the shape of the vanes), I had a few very long flying arrows. Unfortunately, I haven’t been able to test this out in a very controlled way yet.
Alan
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In addition to the gyroscopic benefits of spin, perhaps there is also a beneficial reduction of turbulence? or thickness of the boundary layer?
http://sci-hub.bz/10.1063/1.2885330
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Ok I won't ask for the math anymore. Ifen I was to understand it though I could shoot farther arrows than you guys. . :-\ O:) ;D Arvin
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Ok I won't ask for the math anymore.
LOL......... Arvin, Its not like I try to follow the calculus either, I am too old to remember how.
I find the basic principles described to be of interest, but will leave it up to experimentation to see if the extra friction from a faster spin is a net gain or loss when glueing and trimming feathers on an arrow.
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i came across this info- and thought i would just drop it here
http://www.turkishculture.org/lifestyles/turkish-culture-portal/turkish-flight-arrows-554.htm