Primitive Archer
Main Discussion Area => Bows => Flight Bows => Topic started by: DC on January 28, 2018, 01:07:26 pm
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I'm looking to make some stiff, light arrows. Somewhere in the 350 grain,50-55# spine range. The only shafts I've found that come close are bamboo and then it's hit and miss, most are too heavy. Any ideas?
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Dc, the lighter arrows come out faster but loose speed quicker. I would go for a dense wood with no point smallish diameters. I would try between 175 grains up to about 270 grains and see which score the best. I think with the right arrow close to 400 yards is very possible.
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Do you taper or barrel them to get some weight forward?
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I seem to do best with an arrow that tapers slightly from front to back with about 1/2" of the front rounded into a point.
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DC,
How long do these arrows need to be?
Alan
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28" minimum.
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Decent quality 5/16” Douglas fir shafts should be sufficient for a finished weight of 355 grains. Starting with a straight shaft with 60-65 pound spine will still be around 50-55 pound spine after barrel tapering. This assumes that the diameter at base of the point and nock taper down to about .240-.245” diameter.
Sitka Spruce would end up around 270 grains for the same stiffness and a little bigger maximum diameter.
Alan
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I've got some old growth Western Hemlock that I tried a while back, maybe I'll give it another look. About 6 months ago a 3' dia Sitka Spruce washed up on the beach just up the road. Someone got to it before me :(
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Anyone in Europe know where to find some really stiff spruce? Been working on some flight arrows lately and have some success with purpleheart.
Want to try spruce or pine but the stiffest 5/16 spruce shafts available are only spined 45/50.
Did find some sitka spruce boards but they are crazy expensive and I have no idea if they will provide stiff enough shafts so I did not buy them
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Guys what is the rule of thumb on spine when the arrow has no point. I am building some 70# flight arrows and don't won't one in my arm. D.C. I have been tapering some SureShaft furr that will hit your needs. Arvin
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5# stiffer for every 25 grains less point weight. Arrows are usually spined with 125 grain points I think so no point should be 25# stiffer.
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DC 25# less stiff, not stiffer.
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I'm starting with a 125 grain point and I take it off. Doesn't the arrow get dynamically stiffer?
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I'm starting with a 125 grain point and I take it off. Doesn't the arrow get dynamically stiffer?
Ok, yes the arrow does get stiffer. I thought you meant you needed 25# more spine. Sorry I misunderstood.
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I probably could have explained better.
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So no point on a 70# bow would be around 40 in spine? Thanks guys. Arvin
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Arvin,
It will depend on your draw length too.
Alan
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Arvin,
It will depend on your draw length too.
Alan
Or more specifically the length of the arrow
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Leon, I have been testing spruce from boards and larch and pine also. without a lot of stock to pick thru with still a hit and miss result, i would look to someone like wayne, the sponsor of the arrow section. he spines a lot more arrows than any of us ever will. Canada is next to europe, right? Are there any wood arrow manufactures on your side of the pond? or just resellers?
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Leon, I have been testing spruce from boards and larch and pine also. without a lot of stock to pick thru with still a hit and miss result, i would look to someone like wayne, the sponsor of the arrow section. he spines a lot more arrows than any of us ever will. Canada is next to europe, right? Are there any wood arrow manufactures on your side of the pond? or just resellers?
Thanks! I had a pm from someone with a link, will post if that works out and will also extend my search for arrow manufacturers in europe.
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Let's say 28".
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how thin can one make a flight arrow from hardwoods like ash etc? Does a rain drop shape point help distance?
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For what it’s worth, I have been working on a way of estimating an arrow’s potential based on a spine/deflection measurement of a straight arrow shaft, plus a measurement of the mass, length, and diameter of the straight shaft. The calculation comes up with an arrow weight for a good performing barreled Flight arrow design based on the desired spine, bow characteristics, and arrow length.
For example, for a 28” long flight arrow for a 70# bow with 63 ft-lb of stored energy and 175 grains virtual mass, I get the following stats for a barreled Flight arrow:
Western Larch/Tamarack:
Finished arrow weight 350 grains, max diameter .317”/8.06mm, launch speed 232 fps
Douglas fir from a recycled book shelf:
Finished arrow weight 364 grains, max diameter .341”/8.66mm, launch speed 230 fps
Sitka Spruce:
Finished arrow weight 275 grains, max diameter .343”/8.70mm, launch speed 251 fps
So, given the different arrow diameters, weights, and launch speeds, which of these arrows will fly furthest? ;)
Alan
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Would you please explain the "Virtual Mass" of the bow. I'm not sure if I've heard of this.
My guess would be Spruce, Larch and then Fir :D
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I think i found it here s://sites.google.com/site/technicalarchery/technical-discussions-1/virtual-mass---the-key-to-understanding-arrow-speed
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I am just using a virtual mass number for the bow to estimate how the arrow weight affects the launch speed.
Just for fun, I’ll throw in a more extreme arrow for this same 70# bow. This is from an exceptionally dense and stiff ipe board:
Finished arrow weight 522 grains, maximum diameter .296”/7.9mm, launch speed 202 fps
So this ipe arrow ends up nearly twice as heavy as the spruce arrow, launch speed is much slower, but the ipe arrow is also much thinner and much less affected by air resistance. Maybe this is best...
Alan
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Does the diameter of an arrow make that much difference in air resistance? I would have expected the skin friction to be more important and I thought the weight would trump them all, up to a point where penetration starts to suffer however. I guess diameter affects the amount of skin friction too. 10% less diameter would be 10% less skin
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I saw some tests done of different weight arrows to see how much they slowed down over a distance of about 30 yards I think. The difference between a 500 grain and a 400 grain was shocking. The heavier denser arrows carry much better. I wish the test was between 300 and 200 grain. That would have been more interesting. I am leaning more and more toward 260 grains up to 300 just to see how they do.
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have you ever seen an easy way to determine speed of an arrow downrange?
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There is a new LabRadar chronograph that tracks the speed of projectiles up to 50 yards out. I would love to play with one of those. I think much of the initial loss depends on how clean the arrow is released. It is possible to calculate the speed loss with reasonable accuracy for a perfectly launched arrow if you have a good idea of the arrow’s coefficient of drag.
I’ll give some predicted distances shortly. It is interesting that the worst performing arrow for one set of atmospheric conditions (elevation, temperature, and wind) can become the best performing for a completely different set of conditions.
Alan
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There is a new LabRadar chronograph that tracks the speed of projectiles up to 50 yards out. I would love to play with one of those. I think much of the initial loss depends on how clean the arrow is released.
Thanks, Alan. I will see if I can find out more about that product. Have you seen one in action?
Am following your latest calcs with interest, as I hope to test some arrows soon.
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Here are some calculations to give some idea of how much the material used to make the arrow can affect its potential for ultimate distance. This is just based on a few samples I had around the shop. There is a big range in properties, especially with the softwoods. A friend of mine has this one Douglas Fir arrow that is far superior to the one I measured here.
So here, I kept the shooting at sea level, and varied the temperature and wind.
Distance in yards, 42 deg
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Max Launch Sea Sea Sea Lvl Sea Lvl
Dia Weight Speed Level Level +10mph -10mph
Arrow in. mm grains (fps) @40°F @85°F HdWind TlWind
----------- --- --- ----- ----- ------ ----- ----- ------
Ipe-Case 0.296 7.5 522 202 313 325 320 331
Sitka Spruce 0.343 8.7 275 251 315 341 330 352
Douglas Fir 0.341 8.7 363 230 320 341 332 350
W. Larch 0.319 8.1 374 227 328 347 339 356
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That table was a mess. I’ll try an image to see if it is more readable.
(https://farm5.staticflickr.com/4710/39496235165_35a7852720_z_d.jpg)
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Alan,
are these arrows all simulations? I assume that they must fit well with you real life collected data. The .319 Larch
is an actual arrow?
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This is simulations. So this doesn’t take into account arrow wiggle from a finger release, or initial misalignment due to improper arrow spine.
This is what I am doing:
I have established a reference barreled flight arrow geometry that dictates the geometric proportions for a pretty decent performing flight arrow.
I developed a good approximation of the drag coefficient for this reference arrow.
I then do a spine test on a straight dowel that I intend to make into a new flight arrow. I also measure the diameter, mass, length, span, and weight used for the spine deflection test. Finally, I supply the finished arrow length and spine needed, plus some information about the stored energy and virtual mass of the bow.
The program then calculates the shape of the arrow needed to meet the spine and length requirements (based on the reference arrow proportions). It also calculates the new drag coefficient based on the new arrow geometry. The diameter and mass of the arrows in my example are dictated by the geometry necessary to meet a required spine value. These all have the same spine. So very stiff materials will generate a thinner arrow and v
ery dense materials will drive up the mass of the arrow.
The arrow launch speed is dictated by the calculated arrow mass, stored energy, and virtual mass of the bow. Lighter arrows have a faster launch speed, heaveier arrows have a slower launch speed. The distance calculated is just ballistics. I can include the effects of temperature, altitude, and wind.
It is really pretty eye opening. It takes about 15 minutes to spine check, weigh, and measure the length and diameter of a dozen dowels made from different materials. After that, it gives instant feedback on which dowel should be the best to meet the requirements.
Alan
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It is really pretty eye opening.
wow, quite a few features
I am full of questions, but perhaps one at a time?
As far as the arrow calcs go, Is there a way to input an arbitrary initial velocity of a particular design, for instance one obtained from a chrono, should one want to examine other flight variables besides drag ?
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This is simulations. So this doesn’t take into account arrow wiggle from a finger release, or initial misalignment due to improper arrow spine.
This is what I am doing:
I have established a reference barreled flight arrow geometry that dictates the geometric proportions for a pretty decent performing flight arrow.
I developed a good approximation of the drag coefficient for this reference arrow.
I then do a spine test on a straight dowel that I intend to make into a new flight arrow. I also measure the diameter, mass, length, span, and weight used for the spine deflection test. Finally, I supply the finished arrow length and spine needed, plus some information about the stored energy and virtual mass of the bow.
The program then calculates the shape of the arrow needed to meet the spine and length requirements (based on the reference arrow proportions). It also calculates the new drag coefficient based on the new arrow geometry. The diameter and mass of the arrows in my example are dictated by the geometry necessary to meet a required spine value. These all have the same spine. So very stiff materials will generate a thinner arrow and v
ery dense materials will drive up the mass of the arrow.
The arrow launch speed is dictated by the calculated arrow mass, stored energy, and virtual mass of the bow. Lighter arrows have a faster launch speed, heaveier arrows have a slower launch speed. The distance calculated is just ballistics. I can include the effects of temperature, altitude, and wind.
It is really pretty eye opening. It takes about 15 minutes to spine check, weigh, and measure the length and diameter of a dozen dowels made from different materials. After that, it gives instant feedback on which dowel should be the best to meet the requirements.
Alan
Golly geez! Alan I guess I will just build arrows and throw the crappie arrows away.
Arvin
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wow, quite a few features
I am full of questions, but perhaps one at a time?
As far as the arrow calcs go, Is there a way to input an arbitrary initial velocity of a particular design, for instance one obtained from a chrono, should one want to examine other flight variables besides drag ?
[/quote]
You mean just create a computer model of an arrow and “shoot” it at a certain velocity just to see how far it will go?
What I am really excited about is that
Alan
Alan
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You mean just create a computer model of an arrow and “shoot” it at a certain velocity just to see how far it will go?
yes
I am building a shooting fixture to hold a set of takedown limbs. I want to play with different limb profiles, different amounts of reflex and deflex, different limb lengths and draw lengths. A primary goal is to also experiment with different arrows, and see what they can do with a mechanical release. Hopefully, results from the fixture will let me see whats possible, and help me set reasonable goals for my own finger release when shooting offhand?, and give me some ideas about bow designs to pursue. I intend to use a chrono, and if possible, shoot for distance at the same time.
Standardizing some arrow parameters and keeping records of the shots was part of the plan. I was hoping you might be willing to share some arrow designs when I asked about your programs capabilities. It seems like a very nice way to have a baseline when exploring other variables.
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You have to be wary of computer models, they are basically some fundamental equations with a load of approximations dumped on to to get a match with reality. So the models are made to match reality... reality doesn't start off matching the models.
An anecdote from an engineering forum:-
During high winds in Australia, two power lines touched, arced over, melted and caused a fire that burnt down the farmers barn.
The power company wouldn't pay out because their computer models showed that the insulating spacers prevented the power lines ever touching even in high winds. ::)
The farmer lost his case! :o
(His lawyer must have been pretty useless....)
Del
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My doug fir didn't test out too bad. 27" long 215 grains, 36# spine, .270 at front and .240 at nock. FOC 1/2". Should be good for a 50# bow, I will cut it to 26". So it will likely finish after sanding at about 200 grains. I am going to make a set from 200 to 260 graduating 10 grains with each arrow
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My doug fir didn't test out too bad. 27" long 215 grains, 36# spine, .270 at front and .240 at nock. FOC 1/2". Should be good for a 50# bow, I will cut it to 26". So it will likely finish after sanding at about 200 grains. I am going to make a set from 200 to 260 graduating 10 grains with each arrow
Steve,
That may be exceptional Flight arrow material! Would you be willing to do the following?
1) Measure the deflection of one of the square blanks under a weight placed at its center, like a spine test.
2) Check the height and width of the blank in several spots with some calipers.
3) Measure the mass of the blank in grains
Thanks!
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You mean just create a computer model of an arrow and “shoot” it at a certain velocity just to see how far it will go?
yes
I am building a shooting fixture to hold a set of takedown limbs. I want to play with different limb profiles, different amounts of reflex and deflex, different limb lengths and draw lengths. A primary goal is to also experiment with different arrows, and see what they can do with a mechanical release. Hopefully, results from the fixture will let me see whats possible, and help me set reasonable goals for my own finger release when shooting offhand?, and give me some ideas about bow designs to pursue. I intend to use a chrono, and if possible, shoot for distance at the same time.
Standardizing some arrow parameters and keeping records of the shots was part of the plan. I was hoping you might be willing to share some arrow designs when I asked about your programs capabilities. It seems like a very nice way to have a baseline when exploring other variables.
Sure! I’m Certainly willing to give it a try to see if this approach helps out with getting the most out of your bows. I don’t claim it will accurately predict an exact distance, but I feel it is very possible to get an idea of the potential of how one arrow stacks up against another for a given bow. Potential is the key word. Achieving that potential is an entirely different issue.
Alan
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You have to be wary of computer models....
I agree. But the nice thing about a computer model is that it will always give the same answer for a given model. You start with assumptions and then start chipping away at what needs more work Vs. what doesn’t. It should get better and better over time to the point it captures what is really important and shows similar trends as found with the physical tests.
In contrast, actual real physical testing shows what happened for a particular test at a particular point in time. But nothing stays perfectly consistent from one test to another. Temperature changes, moisture content, wind, properties of the materials are not perfectly consistent, etc. but hopefully physical tests can be controlled well enough that it shows some general trends over time.
Alan
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Allen, could you estimate an arrow distance for me. Ipe, 240 grains, launch speed 216 fps, max dia .220", length 25", spine about 38#.
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Sure! I’m Certainly willing to give it a try to see if this approach helps out with getting the most out of your bows.
Thanks, Alan. Will post my set up and ask more later.
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Allen, could you estimate an arrow distance for me. Ipe, 240 grains, launch speed 216 fps, max dia .220", length 25", spine about 38#.
What span is the spine measured across? Is the spine measured on the dowel that the flight arrow was made from, or on the actual finished flight arrow? All I need is the weight used, distance between supports, and amount of deflection.
Something doesn’t seem right. In order to get a 38# spine from a .220” diameter barreled Flight arrow, it would need to be made of something far stiffer than the stiffest ipe I have ever measured.
Thanks!
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I mixed up my measure, the arrow is only 24" long, so I was likely measuring on about 22" center. I need to get my arrow stuff out of my shed. I am guessing too much here. Using 2# of water in a cup and ballancing while I slide stuff underneath to measure the gaps. LOL.
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I mixed up my measure, the arrow is only 24" long, so I was likely measuring on about 22" center. I need to get my arrow stuff out of my shed. I am guessing too much here. Using 2# of water in a cup and ballancing while I slide stuff underneath to measure the gaps. LOL.
You don’t need to use a 2# weight. Any weight will do as long as you accurately know what it is. One of Thebes weight led that I use for spine testing is 1.612#. A deflection of .500” @ 1.612# is equivalent to 0.500” * (2#/1.612#) = 0.620” for a 2# weight.
Alan
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I will get my set up going again tomorrow so I can take some close measurements.
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I had a 3# weight sitting around and it was off the chart at about 1.8" deflection with 23" span.
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I had a 3# weight sitting around and it was off the chart at about 1.8" deflection with 23" span.
Steve,
That’s about right for Ipe, maybe a bit higher deflection than expected, but it depends on how the arrow is shaped. This arrow is probably way under spine deflection for clean Flight with your bow, but let’s run with it.
At sea level, 70 deg f, zero wind, 42 degree shooting angle, perfectly clean Flight, 323 yards.
But I based on your spine deflection test, I estimate the maximum diameter for the ipe flight arrow would have to be increased to about 0.255” to get enough spine, which would increase arrow mass to about 321 grains, dropping the arrow launch speed to about 180 fps, and giving a distance of 255 yards.
If the same stiffness arrow was made of your best Tamarack/Larch, then the maximum diameter wouldn’t be much different than the ipe arrow, but the arrow would be much lighter at around 200 grains, launch speed much quicker at 211 fps, and distance much better at 283 yards.
Alan
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Alan are the wall hung Ace spine testers accurate enough? They can measure shorter arrows. Arvin
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Alan are the wall hung Ace spine testers accurate enough? They can measure shorter arrows. Arvin
I would hope these are accurate, but I have no experience with these. I just use a dial indicator with the spring removed from the plunger to measure deflection. My setup resembles an arrow straightener. I’ll take a picture.
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Alan, the idea of having an algorithim to predict flight distance potential is intriguing. Are you willing to share the dimensions of the taper of your reference arrow? I need to make a few 24" arrows for 35 lb limbs. Perhaps you have some suggestions so that any actual chrono tests or flight results may help with your evaluation of the formulas or constants you use in your calcs?
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I saw some tests done of different weight arrows to see how much they slowed down over a distance of about 30 yards I think. The difference between a 500 grain and a 400 grain was shocking. The heavier denser arrows carry much better. I wish the test was between 300 and 200 grain. That would have been more interesting. I am leaning more and more toward 260 grains up to 300 just to see how they do.
So the 400 grain arrow would come out of the bow faster than the 500 grain arrow.
The 400 grain arrow would loose speed a lot faster but at 30 yards it would stilll be faster than the 500 grain arrow?
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I saw some tests done of different weight arrows to see how much they slowed down over a distance of about 30 yards I think. The difference between a 500 grain and a 400 grain was shocking. The heavier denser arrows carry much better. I wish the test was between 300 and 200 grain. That would have been more interesting. I am leaning more and more toward 260 grains up to 300 just to see how they do.
So the 400 grain arrow would come out of the bow faster than the 500 grain arrow.
The 400 grain arrow would loose speed a lot faster but at 30 yards it would stilll be faster than the 500 grain arrow?
Not sure if it was still faster at 30 yards but at the rate it was slowing down the 500 would have passed it before too long.
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I have some well cured Phragmites reeds that are feather light and very stiff. Going to give them a try for 500 yards. ;)
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I have some well cured Phragmites reeds that are feather light and very stiff. Going to give them a try for 500 yards. ;)
Try them for 300 yards first, how big is the diameter?
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Varied diameters. A few are very slim but with closer nodes which boosts the stiffness and strength.