Primitive Archer
Main Discussion Area => Bows => Flight Bows => Topic started by: DC on September 10, 2020, 09:53:09 am
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Obviously a question for Alan ;D I'd be very interested in a few specs for the arrow you used. I can't imagine anything but steel taking the compressive forces needed to push an arrow almost 2000 yds but I don't think you used steel. I can imagine the string splitting the arrow and having the two halves dropping on the ground. ;D Any info you'd be willing to share would be very interesting.
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Allen posted some good pics of his arrows on the flight shooting page on facebook. They are carbon fiber solid rods. Very short about 10" they appear to be.
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I can find a half dozen Flight facebook pages. Do you have a link please?
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https://www.facebook.com/photo/?fbid=3738060809542067&set=gm.2637070553213318&__cft__[0]=AZWc5bCUkgJmd8mJw3-k28dlaxG94LQyFHdHgJqn2iKZROZU5i5ibKSWYW7q0VcRNaaA3jWuox4h7y-45oau79tLsd2OEX0wWs5huvyHJJazzFXVN9rDXP3e1yB1I9dMQWkejT_agZVBwApUKDmUuIfr9W-0jRaEXLZFqRh7cawsyEvy2eZnOcvrewa810Vw280&__tn__=EH-R
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Those a really neat. And tidy :D They are long bullets with fletching. Are they barrelled or am I seeing things?
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I am used to getting funny looks when I call these arrows. Haha!
The side view profile is airfoil-like, or resembles a stretched out version of an aircraft external fuel tank. The thickest part of the arrow is .186” diameter, and this is forward of the center of the arrow. It then gradually tapers to a .125” diameter nock, which is small as I can go to fit a string. The best performers are about 115 grains and short as I can get them. They are overdrawn as much as three times their length. The point has to be perfectly balanced on a thin transparent Mylar rest. At release, there is nothing supporting the arrow and the arrow and string just blow through the arrow rest, so it needs to be perfectly aligned and balanced or it will tumble or smash into the bow.
The arrows are also on the edge of aerodynamic stability with long stainless steel nocks shifting weight to the aft end. I take down the corners on one side of the leading edge of the vanes with a diamond hone in order to induce a very mild spin. This spin is the only thing keeping the arrow from tumbling when it slows down at the maximum height of its trajectory. It is tricky to get this just right. What works well at lower altitudes doesn’t always work well at higher altitudes. This trades off some arrow speed for lift and drag so that the arrow lands as softly as possible. Otherwise, it is just gone underground, never to be seen again.
I have had arrows fail on release, and the arrow usually disintegrates so thoroughly that it looks like the bow hacked up a puff of black smoke. Good protective foot shields are essential! The bow is cratered with pock-marks, gouges, and embedded razor blades after years of abuse. It adds character.
It is a fun hobby.
Unfortunately, I don’t yet know how to transfer what I learned about making these tiny carbon arrows to primitive flight arrows. I miss making primitive equipment, but I found I can only focus on one thing at a time.
Alan
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Thanks Alan. If you mounted a chrono on the front of your bow it would look a lot like my shooting machine :D
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Turkish arrows should get you halfway :)
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Thanks Alan. If you mounted a chrono on the front of your bow it would look a lot like my shooting machine :D
I’d have a chrono mounted in front of I could find one light enough! One of these days I’m going to get one of those LabRadar’s that can give speeds over the first 40 or so yards.
Alan
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How on earth do you find them again is my question!!! What draw weight is your footbow Alan? I see what you mean about good foot protectors now....that thing is nuts!
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How on earth do you find them again is my question!!! What draw weight is your footbow Alan? I see what you mean about good foot protectors now....that thing is nuts!
There are bits of arrow and razor blade vanes embedded all over the bow riser and foot shields. There is one recent gouge in the metal riser that is a half inch deep, and it has me re-thinking the shields. I think this happened with one of my last shots at Smith Creek. I remember feeling like I was sprayed with what felt like tiny bits of broken glass at release. I Checked myself for damage, and saw a shattered half of the stainless steel arrow point lying next to me. I picked it up and it was so hot that it sizzled my finger tips. It almost felt like I grabbed the end of a hot soldering iron. I made some adjustments afterward which has really helped prevent these kinds of misfires. So I am expecting much smoother shooting next time.
To answer how the arrows are found, the most important thing is accuracy. The closer I can group the arrows so they fall along a line, the easier it is for the search team to find them. I can usually keep the arrows within a few yards of the line As long as there isn’t any significant cross wind. I also have someone take notes on each shot. They record the arrow serial number, the wind direction and speed, the draw length, and the shape of the hole the arrow leaves in the paper holder. This helps guide where other arrows probably landed relative to any that were found first. I keep a of this information for each of my arrows, and that gives me a pretty good idea of how far out it probably is. Assigning permanent serial numbers to the arrows, and keeping a log of the shots has been extremely valuable for the development of better performing arrows.
The most important key to finding the arrows is to make sure they are shot in a place that has the best surface to stop the arrows above ground. The ideal surface should also be smooth and uniform in color. Color variation and a broken uneven surface is like camouflage. It makes it almost impossible. This is where I have failed repeatedly, and the reason I lost so many arrows this year. Next year, I would rather spend an extra hour or two scouting out the surrounding area before shooting so that shoot direction will give the best chances of finding the arrows. This is a much better use of time compared to wasting many hours of the field crew’s time to find just a fraction of the arrows shot.
I will not plan to shoot this bow at Bonneville again. Bonneville is great for flight shooting wood arrows or much longer arrows, but it is just futile shooting these tiny extreme distance arrows.
I don’t know the draw weight of the bow limbs I shot. I hadn’t finished them in time to take the usual force-draw curve and chronograph testing. I was pretty nervous shooting untested bow limbs. They seemed relatively light in draw weight. I am still cleaning up my shop, but I will measure a force-draw curve and report back. I am curious also!
Alan
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Arrows going underground, or exploding !?!?!?!!!
That's razorblade fletching?
This project is starting to remind me of Rocket Boys.
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Sometimes I wish I was on Facebook but I already spend to much time on this site.
Bjrogg
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Sounds like something from a smokey haze! >:D >:D (lol) (SH)! I think I will stick to the primitive
Arrows and only get the wheelie out to keep it happy! Should be able to do some flight shooting at my friend's place! Those are a bit out of my thought process!
Hawkdancer
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Alan, have you chrono'd the arrows? what kind of speed are we talking?
2000 yds is fascinating, thats just crazy!
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For each set of limbs, I measure the force-draw curve, and run chronograph tests with a range of draw lengths and at least a couple different arrow weights. The configuration I was shooting last year was giving me 640-680 fps with a 110 grain arrow. Stored energy was 160 ft-lb. This recurve design averages about 70% dynamic efficiency at 0.44 grains per pound, so a majority of the energy stored drawing the bow still makes it to the arrow. In other words, it isn’t even operating close to dry-fire conditions.
This isn’t the fastest I’ve tested. The fastest chrono readings were well over 700 fps a few years ago, but I was blowing up a string nearly every shot and the limbs would come apart after about a dozen shots. That was not a lot of fun. I didn’t achieve very good distances because of all the disruption caused by various components failing. As a result, I took a step back and focused on reliability and it really paid off. I am able to pay more attention to systematically tuning the system. Really interesting things happen at low ggp. Small tuning and design differences that may not even register a measurable speed difference on my target bow will easily gain or lose 30-50 fps with this footbow contraption shooting very light arrows. It is a real eye opener.
Now that I have a proven design that is reliable and very efficient, I am ramping up the launch speed again. I hope to be reliably shooting 110-125 grain arrows around 700-750 fps by this fall. I want to make it as challenging as possible for someone with a wheel-bow design to come along and do better!
Alan
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700 fps! Wow, thats getting pretty close to the sound barrier.... almost bumping into the low end of the transonic zone, Thats crazy! I had no idea that was possible with a recurve bow
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For each set of limbs, I measure the force-draw curve, and run chronograph tests with a range of draw lengths and at least a couple different arrow weights. The configuration I was shooting last year was giving me 640-680 fps with a 110 grain arrow. Stored energy was 160 ft-lb. This recurve design averages about 70% dynamic efficiency at 0.44 grains per pound, so a majority of the energy stored drawing the bow still makes it to the arrow. In other words, it isn’t even operating close to dry-fire conditions.
This isn’t the fastest I’ve tested. The fastest chrono readings were well over 700 fps a few years ago, but I was blowing up a string nearly every shot and the limbs would come apart after about a dozen shots. That was not a lot of fun. I didn’t achieve very good distances because of all the disruption caused by various components failing. As a result, I took a step back and focused on reliability and it really paid off. I am able to pay more attention to systematically tuning the system. Really interesting things happen at low ggp. Small tuning and design differences that may not even register a measurable speed difference on my target bow will easily gain or lose 30-50 fps with this footbow contraption shooting very light arrows. It is a real eye opener.
Now that I have a proven design that is reliable and very efficient, I am ramping up the launch speed again. I hope to be reliably shooting 110-125 grain arrows around 700-750 fps by this fall. I want to make it as challenging as possible for someone with a wheel-bow design to come along and do better!
Alan
Maybe heavier arrows would have taken some strain off all the components plus a high BC from the heavier arrows
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Maybe heavier arrows would have taken some strain off all the components plus a high BC from the heavier arrows
Hello Marc,
I will try this out. Distance with a heavier arrow launched at the same velocity should go a little farther, and heavier arrows does help the bow and strings live longer. This balancing act is one area where there is no substitute for real trial and error shooting. A month prior to the flight events, I have been preparing a wide range of arrows and travel to the Alvord dry lake bed to test and tune the system. This is where durability of the bows are really critical. I set the bow in a shooting fixture and keep careful notes about the arrows used, setup of the bow, shot quality, and atmospheric conditions on every shot. A hundred shots later, the data starts to paint a clearer picture of what is and is not working. I’d go insane if I was blowing a string on every shot!
Alan
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@Alan:- Thanks, very interesting post.
I've long suspected that low gpp wasn't the evil that many postulated.
The acceleration from a bow is so high* (even from a "normal" bow) that it doesn't take much to present quite a high inertial load.
I dread to think what the acceleration from your bow is! :o
Del
(I recall doing a back of an envelope calculation showing the acceleration to be about 300g :) )
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This recurve design averages about 70% dynamic efficiency at 0.44 grains per pound, so a majority of the energy stored drawing the bow still makes it to the arrow.
Alan
May I ask, what is this recurve design? Would it also be possible to use that design in primitive bows? Or is it specific to foot bows or is it material dependent?
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May I ask, what is this recurve design? Would it also be possible to use that design in primitive bows? Or is it specific to foot bows or is it material dependent?
This is an interesting thought. Yes, I believe it could be adapted to all natural materials. I follow many of the exact same ideas we discuss here with the primitive flight bows. It is a mild static recurve. Each limb is 20” long. A majority of the bending takes place over 2-3” of the limb, and the wood core is very thin in that area to accommodate the bend without taking on damage or internal set. The limb gradually transitions to very rigid levers and more stiff materials.
I think a modified version of this optimized for sinew-wood-horn composite with natural string would be an interesting project. It would be like making a crossbow prod. I could make very similar arrows out of solid high density Tonkin split cane with water buffalo vanes. I bet 1300 yards is possible. It would pop the string on every shot.
Arvin Weaver made an amazing crossbow a few months back with bamboo back and water buffalo horn belly. I mounted the limbs from that crossbow in my footbow because he wanted to know what it would do. Unfortunately, the bamboo in one of the limbs sheared apart before I could find out. I felt pretty bad about that, but I was able to repair it and will try again.
Alan
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May I ask, what is this recurve design? Would it also be possible to use that design in primitive bows? Or is it specific to foot bows or is it material dependent?
This is an interesting thought. Yes, I believe it could be adapted to all natural materials. I follow many of the exact same ideas we discuss here with the primitive flight bows. It is a mild static recurve. Each limb is 20” long. A majority of the bending takes place over 2-3” of the limb, and the wood core is very thin in that area to accommodate the bend without taking on damage or internal set. The limb gradually transitions to very rigid levers and more stiff materials.
I think a modified version of this optimized for sinew-wood-horn composite with natural string would be an interesting project. It would be like making a crossbow prod. I could make very similar arrows out of solid high density Tonkin split cane with water buffalo vanes. I bet 1300 yards is possible. It would pop the string on every shot.
Arvin Weaver made an amazing crossbow a few months back with bamboo back and water buffalo horn belly. I mounted the limbs from that crossbow in my footbow because he wanted to know what it would do. Unfortunately, the bamboo in one of the limbs sheared apart before I could find out. I felt pretty bad about that, but I was able to repair it and will try again.
Alan
Is there a category for all wood self bow for the foot bow?
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Is there a category for all wood self bow for the foot bow?
No, there isn’t a primitive-specific footbow category. But please don’t let this stop you! Any information you provide about your bow, arrows, and strings on the equipment registration form will be transferred to the detailed shoot results. So there will be a permanent record of what you shot, and how far it was shot that can always be referenced in the future. There are times where someone does make an exceptional shot with equipment that does not quite fit in the existing categories. I was thinking of collecting some of these in a document for those who are curious. For example, Bede Dwyer once shot a round using a modern materials bow with a Historical Korean overdraw “Tongah” made from a split length of bamboo or grooved wood. It allowed him to shoot these very short arrows at full draw. He also shot similar full length arrows from the same bow for comparison. This didn’t fit in any existing category, but the results were officially measured and recorded for anyone who is curious.
Alan