A long consistent power stroke from the point of finger release to the point where the arrow leaves the string. You may want to develop a force/draw chart for your fastest bow and the trial bows to see how they compare. You did a great job covering the speed problem. Remember that you can miss very nicely at 200+fps with a fast bow that is difficult to shoot.
Yes, and I had it happen to me c. 1963/4 Michigan Doe, ground blind w.40# Kodiak Deluxe. That Bow was dangerous to arrows at 15 years but slow by today's standards. At the time, 200fps was a distant goal for factory bows. I am really not sure what speed it takes to out quick a string jump at that distance. @@jakesmith6337
It's fun to watch you reinvent/rediscover the wheel. The Turks played with the design of their hand bows and arrows until they were sending arrows over 400 fps and over 900 yards in the 15th century (1400s). They did it with highly reflexed/recurved crescent shaped (unstrung) bows, short, barreled arrow shafts, grip extensions, and overdraw devices. On some Turkish and Korean bows the unstrung bow tips are only a few inches apart, meet, or even cross. A lot of fun to string. Ivar Malde's Turkish horn bow at 100 lbs draw weight with short 200 grain arrows does 375 fps and 620 yards. FWIW the modern distance record with a traditional/conventional hand-held modern material bow was set by Don Brown in the 1980s. He sent a 14-inch 98 grain arrow over 500 fps and 1,336 yards. He also used a grip extension and overdraw device. Thanks to modern materials the bow limbs come straight off the handle and have a normal amount of recurve at the tips. James Martin has sent 29- inch 390 grain wood arrows over 800 yards from one piece and take-down 130 lb longbows and recurves that look normal when unstrung. He's a scientist at Sandia National Laboratories, so he knows the tech voodoo to make it happen. He'll admit the bows are blazing fast but feel terrible to shoot.
Fastest asiatic bow I currently own is the Alibow Nokor. Mine did 205fps with a 8gpp arrow. I heard that Turkish bows are crazy fast but they arent my style hahaha. Prefer drawing longer
@@bigDbigDbigD Ivar's at 100@28 does 375fps. At 125-150@28 (the old Turkish weights) with same arrows should get there. Soon as somebody builds one we can test it. The math checks out.
I remember reading that the warriors would rate their bows by how many men it took to string them..eg 1. 2 or 3 man bows. ??? Anyone know about that???? Fascinating thing , archery.
I am a bowyer for the past 17 years. Must say that you nailed it with this video. People can not understand why I rebuild ( change) my moulds for the bows over and over again. This is to change the way a bow limbs bend and also the angles at which they bend to get the max performance and smoothness out of the bow. This shows to importance of a correct mould in which the bow is formed ( set). Most of ones troubles start with a mould which is not correct. Can I throw a spanner in the works with this question.. With the Easton culture bows ( mainly horse bows) the limbs are already at the ' back' when the bow is strung. When the string is pulled to full draw, the upper limb goes down and the lower limb comes up. ( With the addition of siyahs at the tips)... So most of the movement is up and down when the string is released ( compare this to modern Parallel axel compound bows)... This makes for bows with almost no handshock and can also be very light in weight (Bow itself)... Compare this with longbows and normal recurves ...heavy grips to compensate for the forward movement of the limbs.. ( they bend backwards and goes forward on release of the string....Enjoyed your video . Keep up the good work. Good to know another bowyer with a passion for bows.....
Great video! Best bow performance explanation I have seen for a traditional bow. As you stated here, there are variants in a bow to get: speed, comfort, forgiveness, etc. Is almost impossible to have all the advantages in one bow. You have to choose what you like.
I've certainly liked your videos but for me this was the best. I have all kinds of bows, horse, long bows, recurve. Fully understood the working part of limbs, weight of moving parts, string, limb composition, length of riser, but never thought about angle of limb attachment. Seems obvious now. Excellent video.
Hey Krame... that's science made easily understandable by lay people. The fact that you tested & experimented & came up with results, that's science. ❤❤❤❤
Very interesting! Yesterday I decided to make a cordovan leather grip on my horse bow. It was thinner than my previous leather grip which already had hand shock, so I decided to wrap a thin exercise band around to beef it up and provide some dampening. Happy to say that it totally eliminated hand shock and made it a joy to shoot. Neat little trick to store in the memory bank.
Brilliant piece of work Kramer. Your willingness to experiment and go well beyond the "accepted norms" is breathtaking - the effort is clearly enormous - so much respect for you. cheers.
It’s absolutely amazing how one inch can make a world of difference and how things change with design, length, string. So many factors go into these things it’s amazing. Even a simple thing like arrow placed on the inside of the bow will draw differently and effect how the paradox works too. When I was testing my crossbow with all sorts of things from brace hight to different bolts I found the reverse of your tests. Longer draw was worse than the shorter. It also affected arrow flight differently too and how it would impact. Archery is just a world of fun and seeing different things and understanding or trying to understand the whys and how comes is fun.
This was one was hard to wrap around my head but justified by the large data dump I received once I understood the complexities. It was well worth the mental challenge. It also reminded me of university level organic chemistry, a requirement class designed to weed out students who had aspirations of going into the health care fields. Thanks. Ron M. (retired pharmacist)
I'm at the 4:30 time and I think I have a general answer to the question about why longer draw length makes faster arrows. Generally, the more energy you put into it, the faster will arrow move. If you put energy into an object, you make Work (in the physical sense). And from a basic formula for work is W=F*s. It is the force provided to an object over some distance. If you increase that distance, you make more work - thus, you give more energy to an arrow. It is very simplified, because in a real situation, Force will change with time, and you would need to calculate the area under a Force - distance graph, but it's doable in an excell (or any other spreadsheet or even just by drawing it yourself). Especially if you made your inch by inch draw force readings (I saw that in another video). So by measuring force every inch, putting it on a graph and calcualting area under it, you will get the amount of work done on the arrow. Great video! 🥰 [edit] Watched till the end and i think you could calculate approximate arrow speed just by measuring draw strength in increments. Your arrow starts with 0 kinetic energy, so all Work you do on that arrow, becomes that arrow's energy. Another formula E=mv^2/2. And if you combine it with Work, you will get formula for speed: V=sqrt(2W/m) where m is the mass of an arrow and W is the work the bow does on that arrow. Give me a shout if you would like me to help you make some spreadsheet calculations. I will gladly help ans also see if I'm correct 😁
Well done I have followed this channel and watched many of your videos for quite a while now. Your demonstrations and explanations have always been direct and informative. Now that you have delved into the science of bow design all viewers have a better understanding of why/how a particular bow behaves the way it does. Thanks for sharing this awesome information. Everyone is smarter for having watched this video.
Interesting! I make and shoot slingshots. The majority of todays shooters use a cheek anchor with the slingshot layed over 90 degrees similiar to archery but many now days shoot what's called long draw and some even full butterfly draw. The same bands cut longer and drawn back farther at the same draw weight produce more speed the same as you show here with a bow. Great video!
I don't know if you've ever done this, but if you wrote a book on all the wackiest things to build bows out of I would 100% buy that anf read it. Love your channel and where it's taken you over the years
This the kind of Archery content the world deserves, backed up by data through trial and error. (I've watched a few vids of yours for a while, this one made me sub!) Now I'd like to know your approach on combining all the best features of warbows(of different cultures) into one.
This is one of best informative videos about bow design I've seen. You did a good job of explaining how the design affects speed...and it was a real eye opener. One question, what kind of wood did you use to make the wood billet risers at the end? I'd like to do the same to replace a metal riser, but I'm not sure if there are certain woods or design issues to avoid.
Really cool video to watch. Thanks for the experiments. I think with your two different riser designs with the same limbs at the end you have to look at the total potential energy available. Think of dropping a ball off a 20' roof. It has a certain potential for energy. It doesn't matter if the ground is at sea level or 900' above sea level, because the roof is only 20' above the ground. Your flat riser design probably has an initial draw weight that is higher than the angled riser. So your difference in force between the start and stop of the shot is smaller with the flat riser than the angled riser. Your flat riser is higher above sea level with a shorter house. Your angled riser is closer to sea level with a taller house.
I would guess that this video is also demonstrating that bow limbs are non-linear springs. Therefore, the power band of a bow limb changes depending upon where in that band you are. If bow limbs were linear springs (following Hooke's Law) it wouldn't matter what part of the band you use. Great video, love this channel!
Among the complications, leverage between the bow limbs and arrow changes through the draw, with the angles between string and path of the arrow, and pull of the limbs.
Great video! You explain the difference in designs well. The reason a lower brace height is faster is because you increase the "power stroke", which is the length the string is in contact with the arrow and transferring energy. More contact time equals more energy transfer, same reason a longer draw length increases speed at the same draw weight. Also don't confuse riser reflex/deflex with limb pocket angles. Reflex/deflex is where the limb pocket ends reletive to the grip, regardless of angle. In order to optimise speed you need to refine the limb geometry more. Extra recurve at the tip, taper the cores to optimise the flex where you want it, and minimise limb mass. Once you have the limb as good as you can make it then play with the riser geometry to get a stable bow with workable brace height. The limbs being all floppy like that on the straight riser is because the brace height was way too high for that geometry. Check out Border Archery super recurves, I think they are the fastest wheel-less bows on the market.
Aloha Kramer, awesome explanation of modern bow design. Question: since most bows are built to standard @28" how does a strong but small short draw archer shoot a faster bow for hunting?
We really need to know the arrow weight each time you test to give the speeds real meaning. Btw, I'm a world record holding bowyer and archer for flight ( distance ) shooting. The deflex reflex with recurved tips is what I build to get the longest distance shot. As an aside, my bows are wooden. I'd be interested in knowing why you think wood won't shoot as fast as glass?
You can use calculus and a draw force curve to prove it but basically the longer your powerstroke (draw length minus brace height), the more time the string has to transfer energy to the bow. The reason your bow is like that is because your limb pockets are too forward. Past parallel limb pockets if there is a tiller problem the limbs are inherently unstable because they aren't swept back at all. If you put the limb pockets at 1 degree swept back this shouldn't be a problem. Glad you talked about efficiency, i have a border and it probably has the most stored energy of any recurve i own, but its not as efficient. You can tell from the handshock and how loud it is.
Yes, Forward handles are seen quite a bit on shorter recurve bows, think Bear Supermag 48 where bow handle is so wide on model. Same deal with limb shape, why for one piece production bows with a shelf, a Cheyenne model of bow is going to be one of fastest bows on market, besides a Supermag where limb position to handle, working portions see how long bow riser area is comparied as well as bow length will have helped in speed similar to a Bearpaw Firestick shelf one piece where 50 inches will help speed of bow due to length of bow being so short having been based off an Asian static limb tip recurve only using modern limbs and a shelf added. I have from Great Plains Traditional Bow Company in 2022, a Youth Model Longbow at 45 pounds as I have a 24 inch draw to lower front ear cartilage just before ear hole and bow is 52 inches so I think length of bow helps in getting speed for my needs. I was going to get Youth Model (recurve) but when owners explained bows, he said after I got bow I was getting, the handle even for my small hands kids XL, women's small, Adult/Men's XS size, would have needed reworking to put a skinnier design of adult handle on bow for me. Now handle size is why company had on website saying teens, ladies and smaller adult men using Youth Longbow and having Youth Bow (recurve) being advertised for 9--12 years old.
Couple of theories on bow speed verses bow length. Lets look at a 52 inch bow verses a 60 inch bow, both shooting the same weight/length of arrow, the same poundage at 28 inches, AND the same brace height. All these factors the same, the short bow will shoot faster. THEORY ONE - Longer limbs weigh more than short limbs, and require more energy to propel the arrow AND move the heavier limbs forward. THEORY TWO- A a shorter limb stacks energy more quickly at the beginning of the draw. This gives more total energy over the entire length of the draw. This would be easy to test. Draw each bow an inch at a time and measure the draw weight at each inch increase. If this theory is correct, the pull weight should increase more rapidly with the short bow. Keep in mind, the brace height has to be the same for both bows to be a legitimate test, otherwise, the power strokes will be different lengths and not an accurate comparison. Thanks for all the interesting topics.
I have a fishing bow converted to terrestrial use. 45 lb. It's slow, but perfectly happy with a heavy arrow, and very accurate. And still easily shoots through a straw bale at what doesn't seem to be more than 175 fps. Those bows are indestructible, lol. Thats why I got it. I've only ever worn out strings. I have other bows, compounds and longbows. But old rainproof is reliable.
For so much of the design differences affecting arrow speed, it comes down to the amount of time the force of the string can apply itself to a bow. It's all about imparting ENERGY into the arrow, which has a time/length component as well as a force component. The same is true in firearms. Up to a certain point, a longer barrel will result in a faster, longer shooting gun. This is why the M16 can shoot further than the M4 carbine, even though both use the same round, and are practically the same chamber/receiver/etc. The M16's 20 inch bareel is longer than the M4's 14.5 inch barrel, so the force of the exploding gunpowder can push against the bullet for a longer period of time. Of course there comes a point where friction, etc will take away from the speed and range benefits. Same with a bow.
That's really a WOW video, I already and read about those parameters but never seen a video with demonstrations...I'm a beginner on bow making I'm at my third bow (first almost succesfull), I had think about give to it some reflex and make it a little shorter but I also don't want to ruin it. So I'll make some more planning on my next bow. Unfortunatly I can't build a lot of bows because here in Italy for laws we can't cut down trees (only if it is in your property and if that tree is not considered "protected species") and on the other hand it's also almost impossible to find boards...the only wood you can buy at stores is Pinus and Abies...I have tried make a bow out of Abies and obiously I didn't even arrived at tillering that it went in pieces, the other one was make of Olea, it was an iteresting experiment because it didn't brake but it was so low on poundage, I'll try again with that wood. My last bow is made out of black locust I for sure know that I can make better bows out of it. Black Locust is the only "good" wood that I can find somewere in my area, the problem is that is a recent tree and you can't find big trees it is here only from something about 20 years
Hi! Not an archer, really (though I can shoot a bow) but the brace height change just makes good sense when you consider the physics at work: Even though the amount of force required to draw the bow is *slightly* lower, the distance over which that force must be applied - both to draw the bow, and as the bow accelerates the arrow - is now larger. Work equals force times displacement; so long as the 'draw weight' is not reduced too drastically, any change which increases the displacement over which that force can be applied to the projectile in turn results in a greater total acceleration.
If I recall my science 101 class correctly, I think Newton's equation F=ma comes into play. The Force(40 lbs) equals mass(arrow)x acceleration ( draw length). So the Force and the arrow mass don't change but,...the acceration(draw length) does. The draw length influences the arrow speed.
U Sir are crazy. Thx so much for these experiments. I am just 4months into this hobby. i have a 34lbs TD recurve from a german bowmaker. With a light 600 spine arrow it gives me almost 200fps. My 49lbs Recurve is only 20fps faster with the same arrow. That 34lbs Bow is my learn-the-technique Bow and will be probably forever. I am really thankful to have bought this masterpiece for 750 euros as a first. There is so much engineering in it, to reach this speed.
Fascinating! I'm hardly confused at all - maybe I need more confusion; maybe confusion with the right attitude (and some coffee) leads to profusion (of concepts).
This reminds me of an old idea of optimizing a bow for traditional or instinctive archery while using newer technology. I wonder if this would be of interest, making a lomgbow/recurve combined with a modern compound, and optimizing the various factors to not have a release like a compound, not sight etc
You should test out string bridges they allegedly add 7- 15fps. Depending on what composite materials used. For me mimicking a baseball has worked well
Very very interesting study mate !! I commend you for your interest and desire to experiment 👍 I’d love to see what speed you could get with those limbs of 70# @ 29” draw
Thanks for this, Kramer. I learned a lot. Now I know why my 66# Ole Ben longbow shoots a slower arrow than my 50# Samick Sage, but the longbow seems to hit harder.
You can figure in a multitude of variables but the main one is simply the direction or angle of released energy. The reason a recurve is faster than a longbow is that the energy is released in a tighter forward motion. The longbow's limbs release energy in an outward arching trajectory. Look at the newer compounds. The limbs are configured in a fairly extreme arch, therefore the energy is created mostly in the cams not the limbs and released in a forward motion rather than being wasted in the outward arching trajectory of the tips of the limbs. The more energy moving in the direction of the arrows flight, rather than at an outward angle, the faster the trajectory.
hey man one of ur vids was the first "bow build" I ever saw about 2 yrs ago. now my garage and basement is packed full of all stages of wood drying it drives my wife NUTS!! but thank you! just wanted to throw that out there B4 I was that also that had to say if u use ur pliers(or channel locks.. I know brand name..) the other way they will work way better for u lol anyways cheers mang
I think in the traditional world where we can't attach as many things to our bows to dampen vibration, chasing speed had noticeably more cons to our performance. I talked to 4 different bowyers and researched for 5 years before I got my first and only custom bow and I chased silence and bow length (as I am a backyard archer first and a hunter second). Longer draw length is a longer powerstroke I'm 5'8.5" with a 29" draw so 50lbs is a long 50lbs to pull back but has a higher speed than 50lbs at 28" (atleast from tests I've seen). Thin limbs have less air resistance but the mass of the limbs is a huge component in arrow cast as well, you want light mass limbs with a heavy draw and thin profile so thicker limbs are good. I settled on my favorite design and performance for my needs being a 50s style recurve called the Toelke Super static because 64" bows are slower, but more comfortable for longer draw guys like myself. The thing is quieter than any compound or other bow I've been around but while that comes in part from the design, the real factor is my arrow mass being so high. That is how I got a super super whisper quiet bow, that still shoots relatively fast and is dead in the hand.
Cool video bringing a couple of key factors in for speed. Kramer, have you studied also Yumi bows? They claim to be very efficient because less energy can turn to handshock, as the grip is set not on a node of the resulting resonance frequency. I found no further notes, unfortunatelly, but I know they are onto something. An efficient bow doesn‘t wobble much after the arrow left the string. Yes, weight of arrow/weight of limb is a key factor-but what if the frequency of the limbs is another factor for their effficiency?
Lower brace height means change in bow geometry. You will make a recurve bow more recurve and giving overall more energy storage even if the final draw weight is a bit less.
Draw graph of draw weight (y axis) vs length (x axis). Graph the weight at different points during the draw, up to max draw length. Now colour in the area below that line. The *area* coloured in represents the sorted energy in the bow.
reflex and recurve all make your bow faster, but that's only in comparison to another bow weighing the same, with the same amount of working limb, and shaped the shape that isn't reflexed or recurved. But just making a recurve on a bow can add extra weight and offset the benefit you get from recurving it. But if you don't put enough wood in the recurve portion, then the recurve can get pulled out as you use it. Making a fast bow needs to maximize the positives while minimizing the negatives. One of the fastest bows I build was a simple pyramid bow made from a board of cherry and backed with a layer of flax fibers. It got close to 200 fps, but then exploded one day out of the blue.
if 2 bows are different draw lengths but the arrows are both the same nd the draw weights are the same then you wont increase speed because running a longer arrow in the shorter length will also it down and compromise accuracy Also over drawing can add more pounds might get more speed but you risks bow damage raising brace height does not increase speed it actually reduces speed adds more stress to limbs causing damage to the bow
Forget about maximum draw weight. That is like saying only horsepower is important for acceleration and not torque. Keep things simple. First, Energy = Force X Distance. The Distance would be the draw length but the Force is not the maximum draw weight, rather an average from zero inches of draw to maximum draw length. What you need to do for each bow is to come up with a graph of draw weight versus draw length. Start with 0.5¨ and measure draw weight all the way up to maximum draw length in 0.5¨ increments, now graph the results. The area under the graph is the total energy of that bow at that given draw length. Arrow velocity would follow that total energy figure much better than maximum draw weight. Keeping in mind that varying arrow weight would result in varying efficiencies. Heavier arrows will always extract more energy from a bow, i.e. more efficient. Once you have this graph for a bunch of bows you can begin to weed out the less efficient bow designs. For instance, let´s say you have two bows that at 28¨ draw length have very similar areas under the graph. Take those two bows and test them for speed keeping the arrow weight the same. The results may show that with the same area under the graph one shows higher arrow speed. Then investigate why. It could turn out that a bow limb or riser type may be more efficient. This will help you derive at the best bow design taking all variables into consideration. The goad would be to maximize arrow speed performance with the lightest draw weight, i.e. a more comfortable bow to handle and shoot accurately. Basically you would optimize the design. I would love to see those results of that analysis. Go for it.
Here are my two cents... When it comes to energy stored, you should only consider energy put in by the draw, not the stringing, since it will not be transferred to the arrow. @GeekBot makes a great point about why energy transfer can be affected by how much bending is happening until you reach brace height. Instead of a brace height, draw length and draw weight one should consider the work stored in the system, which is just the force over the distance (eg actual draw weight at any given point along the draw length). This will then still get altered by your limbs - not only will their weight affect things, but how fast they want to spring back - since it is not instantaneous.
Awesome video, Kramer! I’m struggling a little with my recurve bow getting only 175ish fps with approx. 45# draw weight and 27ish “ draw length I’m shooting the Uukha Selenga limbs on an Oak Ridge Byron riser. Can you say anything about a possible optimal riser design for those limbs? Or is it simply try try try - and then find out? :)
In engineering, a Moment (a physics concept about velocity) is equal to the force times the distance (Moment=force*distance). So, by making the limbs longer, but making the draw weight less, you can achieve a faster bow due to an ideal ratio between the force and the distance. If you are able to find the sweet spot for speed in that ratio, you can find an ideal draw weight! Materials and angles make it even more interesting, but this idea is a good place to start!
Acceleration the longer draw has more time to accelerate the arrow just as a short barrel pistol or rifle using the same cartridge have different velocity.
"Pounds", in this context, is a force being applied to the arrow when the string is released, but the question is for how low that force is being applied to it. There are two things that matter: 1. The average pounds of force during the time that the string is pushing the arrow and returning to its rest position. 2. The amount of time this force is being applied to the arrow, to accelerate it. It all comes down to applying as much force as possibly, consistently, over as much time as possible. That is why a longer draw length means the string will be pushing the arrow for a longer amount of time. But the problem is if the bow has most of its pundage of force at maximum draw, and very little during the first part of the draw. Yes, it's quite complicated to calculate. The "best bow" would be one that is as heavy to pull on the string in the beginning of the draw as when you're reaching max draw, which is of course very tricky to build. I'm not sure, but I think this is what a recurve bow design is attempting to improve on. All of this ignores the problem of air resistance, which isn't a very large factor in this context, though. There is additionally the question of how quickly the bow is able to shed its energy, how quickly it can return to resting position. This could potentially bottleneck the arrow speed, otherwise. When we measure the poundage of the bow, we're measuring it while it is being drawn, not while it is releasing, which can be deceptive. In fact, a really heavy arrow will be able to absorb much more of the energy from he bow, but this is of course a case of Newton's F=ma.
Hey Kramer, this was a great video. I really appreciate ya, Very interesting lots of great theories and it would be absolutely a blast to be working with you and testing all these different theories. I still have not heard back from you on whether you could build me a set of limbs or not. I’d really appreciate you getting back in contact with me. Thank you so much my friend take care and God bless.
Hey, I’ve been watching you for a long time always really enjoy your video and you are one of the reason why I started making bows and I’m gonna be making a bow for hunting soon but I’m curious did this bow shoot faster than your old fastest bow? The bad thing is, I don’t remember how fast that one shoot and what if you make the handle curve kind of like a bow that will that shoot faster, curve the handle away from you a lot and put Normal we curve limbs on it. And keep up the great work.
Think about a high power bottle necked rifle cartridge. They use slow burning powder to build pressure as the bullet goes down the barrel. Longer Push!
You never mentioned material reaction time. Different materials will return to least tension at different rates, so the type of material should be considered. In order for the rules you've stated here to apply, you'd have to be using the same materials in each of the various design changes.
He did mention that fiberglass was faster then wood and carbon fiber was faster then fiberglass. Not a great selection but pretty much covers materials we are likely to use.
That matters much less than you'd think. The real performance gain is the strength to mass ratio. Carbon is simply much lighter than glass for the same strength and therefore more efficient.
I think the more time the arrow attached to the string at the moment of release, the more power it will store from the bow limbs, so a longer draw length + a short brace hight should give more power, I think So you may loose few bounds from the short brace hight, but smother draw and more stored energy.
How much recurve you have and how much recurve you use is a huge factor. I have moved the grip away from the string to keep from unwinding the recurves at brace height. The recurve is not just an interesting shape it’s a shape the allows the limb to store more energy mid draw. To use the recurve the string must be lying on the limb. When it does the bow seems shorter to the string and harder to pull, until the recurve unfolds then it’s the same as a long bow.
I have a question that I know you know the definitive answer to. I'm 5'2" tall. Stocky guy with a very short draw length. I'm also 74 years old but that's just some information and not an issue here. The thing is I'm having to use bows somewhere between 55 to 60 lbs in order to get 40ish pounds at my draw length. I also set my brace height as low as possible to get, what I think, is a long enough power stroke on my arrows. Is this correct thinking on my part? My hunting bow now is an old Ben Pearson 52" 56# bow set at 6 inch brace height and it pulls 39 to 40 lbs at my draw length. BUT....this bow is more deflex than reflex. With a compound my bow was pulling 80 lbs peak and I'd found a brand of bow that favored a low brace height. Now my BP is a good bow but finding something to replace it with has me concerned that I may at some point have to have a bow custom built or just suffer the trade off in finding a "sufficient" off the rack bow. Whatcha think? That short Mountain Bow was looking pretty dang right up my alley kinda bow. I've scoured the WWW For answers to these questions and haven't had much luck. Anywho, thanks for your time. Love the vids and my new Shattered Bowstring.
Another thing: Every bow is already storing energy before you even touch the string. Would be possible a design which can use ALL the energy pre-stored in the bow, for example using a loose string before shooting?
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A long consistent power stroke from the point of finger release to the point where the arrow leaves the string. You may want to develop a force/draw chart for your fastest bow and the trial bows to see how they compare. You did a great job covering the speed problem. Remember that you can miss very nicely at 200+fps with a fast bow that is difficult to shoot.
And a deer at 12 yds can duck the arrow of a slow bow
Ah! Cam wheels and a mechanical release...
Yes, and I had it happen to me c. 1963/4 Michigan Doe, ground blind w.40# Kodiak Deluxe. That Bow was dangerous to arrows at 15 years but slow by today's standards. At the time, 200fps was a distant goal for factory bows. I am really not sure what speed it takes to out quick a string jump at that distance. @@jakesmith6337
That's a lot of good information. Thank you for your experimentation
@@jakesmith6337 missed?
It's fun to watch you reinvent/rediscover the wheel. The Turks played with the design of their hand bows and arrows until they were sending arrows over 400 fps and over 900 yards in the 15th century (1400s). They did it with highly reflexed/recurved crescent shaped (unstrung) bows, short, barreled arrow shafts, grip extensions, and overdraw devices. On some Turkish and Korean bows the unstrung bow tips are only a few inches apart, meet, or even cross. A lot of fun to string. Ivar Malde's Turkish horn bow at 100 lbs draw weight with short 200 grain arrows does 375 fps and 620 yards. FWIW the modern distance record with a traditional/conventional hand-held modern material bow was set by Don Brown in the 1980s. He sent a 14-inch 98 grain arrow over 500 fps and 1,336 yards. He also used a grip extension and overdraw device. Thanks to modern materials the bow limbs come straight off the handle and have a normal amount of recurve at the tips. James Martin has sent 29- inch 390 grain wood arrows over 800 yards from one piece and take-down 130 lb longbows and recurves that look normal when unstrung. He's a scientist at Sandia National Laboratories, so he knows the tech voodoo to make it happen. He'll admit the bows are blazing fast but feel terrible to shoot.
Fastest asiatic bow I currently own is the Alibow Nokor. Mine did 205fps with a 8gpp arrow. I heard that Turkish bows are crazy fast but they arent my style hahaha. Prefer drawing longer
If Turks really had 400 fps I would like to see it tested
@@bigDbigDbigD Ivar's at 100@28 does 375fps. At 125-150@28 (the old Turkish weights) with same arrows should get there. Soon as somebody builds one we can test it. The math checks out.
Hungarian, Turkish, Korean and Mongolian bows are all bows of ancient Scythes
I remember reading that the warriors would rate their bows by how many men it took to string them..eg 1. 2 or 3 man bows. ??? Anyone know about that???? Fascinating thing , archery.
I am a bowyer for the past 17 years. Must say that you nailed it with this video. People can not understand why I rebuild ( change) my moulds for the bows over and over again. This is to change the way a bow limbs bend and also the angles at which they bend to get the max performance and smoothness out of the bow. This shows to importance of a correct mould in which the bow is formed ( set). Most of ones troubles start with a mould which is not correct. Can I throw a spanner in the works with this question.. With the Easton culture bows ( mainly horse bows) the limbs are already at the ' back' when the bow is strung. When the string is pulled to full draw, the upper limb goes down and the lower limb comes up. ( With the addition of siyahs at the tips)... So most of the movement is up and down when the string is released ( compare this to modern Parallel axel compound bows)... This makes for bows with almost no handshock and can also be very light in weight (Bow itself)... Compare this with longbows and normal recurves ...heavy grips to compensate for the forward movement of the limbs.. ( they bend backwards and goes forward on release of the string....Enjoyed your video . Keep up the good work. Good to know another bowyer with a passion for bows.....
Great video!
Best bow performance explanation I have seen for a traditional bow.
As you stated here, there are variants in a bow to get: speed, comfort, forgiveness, etc. Is almost impossible to have all the advantages in one bow. You have to choose what you like.
I've certainly liked your videos but for me this was the best. I have all kinds of bows, horse, long bows, recurve. Fully understood the working part of limbs, weight of moving parts, string, limb composition, length of riser, but never thought about angle of limb attachment. Seems obvious now. Excellent video.
Do yourself a favor: pause at 12:04. The level of psychotic dedicated passion in this man’s eyes indicates I believe his opinion!!!
Hey Krame... that's science made easily understandable by lay people. The fact that you tested & experimented & came up with results, that's science.
❤❤❤❤
Very interesting! Yesterday I decided to make a cordovan leather grip on my horse bow. It was thinner than my previous leather grip which already had hand shock, so I decided to wrap a thin exercise band around to beef it up and provide some dampening. Happy to say that it totally eliminated hand shock and made it a joy to shoot. Neat little trick to store in the memory bank.
You passion to find the answers is inspiring! Thank you Mr K. Answered allot of questions for me to!
Brilliant piece of work Kramer. Your willingness to experiment and go well beyond the "accepted norms" is breathtaking - the effort is clearly enormous - so much respect for you. cheers.
It’s absolutely amazing how one inch can make a world of difference and how things change with design, length, string. So many factors go into these things it’s amazing.
Even a simple thing like arrow placed on the inside of the bow will draw differently and effect how the paradox works too.
When I was testing my crossbow with all sorts of things from brace hight to different bolts I found the reverse of your tests.
Longer draw was worse than the shorter. It also affected arrow flight differently too and how it would impact.
Archery is just a world of fun and seeing different things and understanding or trying to understand the whys and how comes is fun.
This was one was hard to wrap around my head but justified by the large data dump I received once I understood the complexities. It was well worth the mental challenge. It also reminded me of university level organic chemistry, a requirement class designed to weed out students who had aspirations of going into the health care fields. Thanks. Ron M. (retired pharmacist)
Fascinating. For me, one of your most interesting videos. Thanks.
It’s amazing to follow your videos and your trail and error analysis and your capability and knowledge and and and…. keep going and stay safe! 👍
I'm at the 4:30 time and I think I have a general answer to the question about why longer draw length makes faster arrows. Generally, the more energy you put into it, the faster will arrow move. If you put energy into an object, you make Work (in the physical sense). And from a basic formula for work is W=F*s. It is the force provided to an object over some distance. If you increase that distance, you make more work - thus, you give more energy to an arrow. It is very simplified, because in a real situation, Force will change with time, and you would need to calculate the area under a Force - distance graph, but it's doable in an excell (or any other spreadsheet or even just by drawing it yourself). Especially if you made your inch by inch draw force readings (I saw that in another video). So by measuring force every inch, putting it on a graph and calcualting area under it, you will get the amount of work done on the arrow.
Great video! 🥰
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Watched till the end and i think you could calculate approximate arrow speed just by measuring draw strength in increments. Your arrow starts with 0 kinetic energy, so all Work you do on that arrow, becomes that arrow's energy. Another formula E=mv^2/2. And if you combine it with Work, you will get formula for speed: V=sqrt(2W/m) where m is the mass of an arrow and W is the work the bow does on that arrow. Give me a shout if you would like me to help you make some spreadsheet calculations. I will gladly help ans also see if I'm correct 😁
I learn so much from watching/ listening on here! Thank you, J
Well done
I have followed this channel and watched many of your videos for quite a while now.
Your demonstrations and explanations have always been direct and informative. Now that you have delved into the science of bow design all viewers have a better understanding of why/how a particular bow behaves the way it does.
Thanks for sharing this awesome information.
Everyone is smarter for having watched this video.
That was so cool!!
You did prove that the "law of diminishing returns" is alive and well.
Interesting! I make and shoot slingshots. The majority of todays shooters use a cheek anchor with the slingshot layed over 90 degrees similiar to archery but many now days shoot what's called long draw and some even full butterfly draw. The same bands cut longer and drawn back farther at the same draw weight produce more speed the same as you show here with a bow. Great video!
I don't know if you've ever done this, but if you wrote a book on all the wackiest things to build bows out of I would 100% buy that anf read it. Love your channel and where it's taken you over the years
This the kind of Archery content the world deserves, backed up by data through trial and error. (I've watched a few vids of yours for a while, this one made me sub!)
Now I'd like to know your approach on combining all the best features of warbows(of different cultures) into one.
This is one of best informative videos about bow design I've seen. You did a good job of explaining how the design affects speed...and it was a real eye opener.
One question, what kind of wood did you use to make the wood billet risers at the end?
I'd like to do the same to replace a metal riser, but I'm not sure if there are certain woods or design issues to avoid.
He used Selangan Batu for that one… I brought it home from Japan and gave it to him.
Really cool video to watch. Thanks for the experiments. I think with your two different riser designs with the same limbs at the end you have to look at the total potential energy available. Think of dropping a ball off a 20' roof. It has a certain potential for energy. It doesn't matter if the ground is at sea level or 900' above sea level, because the roof is only 20' above the ground.
Your flat riser design probably has an initial draw weight that is higher than the angled riser. So your difference in force between the start and stop of the shot is smaller with the flat riser than the angled riser.
Your flat riser is higher above sea level with a shorter house. Your angled riser is closer to sea level with a taller house.
I would guess that this video is also demonstrating that bow limbs are non-linear springs. Therefore, the power band of a bow limb changes depending upon where in that band you are.
If bow limbs were linear springs (following Hooke's Law) it wouldn't matter what part of the band you use.
Great video, love this channel!
Among the complications, leverage between the bow limbs and arrow changes through the draw, with the angles between string and path of the arrow, and pull of the limbs.
Great video! You explain the difference in designs well. The reason a lower brace height is faster is because you increase the "power stroke", which is the length the string is in contact with the arrow and transferring energy. More contact time equals more energy transfer, same reason a longer draw length increases speed at the same draw weight.
Also don't confuse riser reflex/deflex with limb pocket angles. Reflex/deflex is where the limb pocket ends reletive to the grip, regardless of angle.
In order to optimise speed you need to refine the limb geometry more. Extra recurve at the tip, taper the cores to optimise the flex where you want it, and minimise limb mass. Once you have the limb as good as you can make it then play with the riser geometry to get a stable bow with workable brace height. The limbs being all floppy like that on the straight riser is because the brace height was way too high for that geometry.
Check out Border Archery super recurves, I think they are the fastest wheel-less bows on the market.
Remember that you also gain about 2# of draw weight for every inch over 28 inches measured draw length. So, you pick up some speed there too.
@@paullewis5045 Yes, that's why I clarified with "at the same draw weight", meaning at full draw not marked weight.
@@mrnice752yep..I was a bit confused too. Got it 👍
This is just awesome Kramer! Keep up the good work😁😁 let's see more crazy designs for high performance bows - keep em coming
Aloha Kramer, awesome explanation of modern bow design. Question: since most bows are built to standard @28" how does a strong but small short draw archer shoot a faster bow for hunting?
Wow Kramer! Such a great video. I learned quite a lot! Keep up the great work!
We really need to know the arrow weight each time you test to give the speeds real meaning. Btw, I'm a world record holding bowyer and archer for flight ( distance ) shooting. The deflex reflex with recurved tips is what I build to get the longest distance shot. As an aside, my bows are wooden. I'd be interested in knowing why you think wood won't shoot as fast as glass?
You can use calculus and a draw force curve to prove it but basically the longer your powerstroke (draw length minus brace height), the more time the string has to transfer energy to the bow.
The reason your bow is like that is because your limb pockets are too forward. Past parallel limb pockets if there is a tiller problem the limbs are inherently unstable because they aren't swept back at all. If you put the limb pockets at 1 degree swept back this shouldn't be a problem.
Glad you talked about efficiency, i have a border and it probably has the most stored energy of any recurve i own, but its not as efficient. You can tell from the handshock and how loud it is.
I'm binge watching this channel, just found it this morning, enjoying the style
Thanks
🏹
Yes, Forward handles are seen quite a bit on shorter recurve bows, think Bear Supermag 48 where bow handle is so wide on model. Same deal with limb shape, why for one piece production bows with a shelf, a Cheyenne model of bow is going to be one of fastest bows on market, besides a Supermag where limb position to handle, working portions see how long bow riser area is comparied as well as bow length will have helped in speed similar to a Bearpaw Firestick shelf one piece where 50 inches will help speed of bow due to length of bow being so short having been based off an Asian static limb tip recurve only using modern limbs and a shelf added.
I have from Great Plains Traditional Bow Company in 2022, a Youth Model Longbow at 45 pounds as I have a 24 inch draw to lower front ear cartilage just before ear hole and bow is 52 inches so I think length of bow helps in getting speed for my needs. I was going to get Youth Model (recurve) but when owners explained bows, he said after I got bow I was getting, the handle even for my small hands kids XL, women's small, Adult/Men's XS size, would have needed reworking to put a skinnier design of adult handle on bow for me. Now handle size is why company had on website saying teens, ladies and smaller adult men using Youth Longbow and having Youth Bow (recurve) being advertised for 9--12 years old.
Very instructive. Thanks for taking the time making it.
The most exciting part about your videos is constant desire to perfect bows.
Looking forward to see your new "research and development"
Thank you for such informations, which gives me tons of ideas & knowledge of Bows & Arrows ...
Couple of theories on bow speed verses bow length. Lets look at a 52 inch bow verses a 60 inch bow, both shooting the same weight/length of arrow, the same poundage at 28 inches, AND the same brace height. All these factors the same, the short bow will shoot faster. THEORY ONE - Longer limbs weigh more than short limbs, and require more energy to propel the arrow AND move the heavier limbs forward. THEORY TWO- A a shorter limb stacks energy more quickly at the beginning of the draw. This gives more total energy over the entire length of the draw. This would be easy to test. Draw each bow an inch at a time and measure the draw weight at each inch increase. If this theory is correct, the pull weight should increase more rapidly with the short bow. Keep in mind, the brace height has to be the same for both bows to be a legitimate test, otherwise, the power strokes will be different lengths and not an accurate comparison. Thanks for all the interesting topics.
I have a fishing bow converted to terrestrial use. 45 lb. It's slow, but perfectly happy with a heavy arrow, and very accurate. And still easily shoots through a straw bale at what doesn't seem to be more than 175 fps.
Those bows are indestructible, lol. Thats why I got it. I've only ever worn out strings. I have other bows, compounds and longbows. But old rainproof is reliable.
For so much of the design differences affecting arrow speed, it comes down to the amount of time the force of the string can apply itself to a bow. It's all about imparting ENERGY into the arrow, which has a time/length component as well as a force component.
The same is true in firearms. Up to a certain point, a longer barrel will result in a faster, longer shooting gun. This is why the M16 can shoot further than the M4 carbine, even though both use the same round, and are practically the same chamber/receiver/etc. The M16's 20 inch bareel is longer than the M4's 14.5 inch barrel, so the force of the exploding gunpowder can push against the bullet for a longer period of time.
Of course there comes a point where friction, etc will take away from the speed and range benefits. Same with a bow.
As a intermediate archer this was fascinating. Nice job explaining this 👍🏻
Best bideo I've seen on bow design. Thank you.
That's really a WOW video, I already and read about those parameters but never seen a video with demonstrations...I'm a beginner on bow making I'm at my third bow (first almost succesfull), I had think about give to it some reflex and make it a little shorter but I also don't want to ruin it. So I'll make some more planning on my next bow.
Unfortunatly I can't build a lot of bows because here in Italy for laws we can't cut down trees (only if it is in your property and if that tree is not considered "protected species") and on the other hand it's also almost impossible to find boards...the only wood you can buy at stores is Pinus and Abies...I have tried make a bow out of Abies and obiously I didn't even arrived at tillering that it went in pieces, the other one was make of Olea, it was an iteresting experiment because it didn't brake but it was so low on poundage, I'll try again with that wood.
My last bow is made out of black locust I for sure know that I can make better bows out of it. Black Locust is the only "good" wood that I can find somewere in my area, the problem is that is a recent tree and you can't find big trees it is here only from something about 20 years
Thank you for the video and really enjoy your passion. Can you tell us the grains per pound used when testing arrow speed between the designs?
Hi! Not an archer, really (though I can shoot a bow) but the brace height change just makes good sense when you consider the physics at work:
Even though the amount of force required to draw the bow is *slightly* lower, the distance over which that force must be applied - both to draw the bow, and as the bow accelerates the arrow - is now larger.
Work equals force times displacement; so long as the 'draw weight' is not reduced too drastically, any change which increases the displacement over which that force can be applied to the projectile in turn results in a greater total acceleration.
Seem pretty informative I just could not handle the dirt in the middle of your lens at 6.24
Just found your channel. This one video earned you a new subscriber.
If I recall my science 101 class correctly, I think Newton's equation F=ma comes into play. The Force(40 lbs) equals mass(arrow)x acceleration ( draw length). So the Force and the arrow mass don't change but,...the acceration(draw length) does. The draw length influences the arrow speed.
U Sir are crazy. Thx so much for these experiments.
I am just 4months into this hobby.
i have a 34lbs TD recurve from a german bowmaker. With a light 600 spine arrow it gives me almost 200fps.
My 49lbs Recurve is only 20fps faster with the same arrow.
That 34lbs Bow is my learn-the-technique Bow and will be probably forever.
I am really thankful to have bought this masterpiece for 750 euros as a first.
There is so much engineering in it, to reach this speed.
Fascinating! I'm hardly confused at all - maybe I need more confusion; maybe confusion with the right attitude (and some coffee) leads to profusion (of concepts).
great explanation about bows strength well done
This reminds me of an old idea of optimizing a bow for traditional or instinctive archery while using newer technology. I wonder if this would be of interest, making a lomgbow/recurve combined with a modern compound, and optimizing the various factors to not have a release like a compound, not sight etc
I think you should include in your test, also different arrows, for same setup before changing risers
You should test out string bridges they allegedly add 7- 15fps. Depending on what composite materials used. For me mimicking a baseball has worked well
Very very interesting study mate !!
I commend you for your interest and desire to experiment 👍
I’d love to see what speed you could get with those limbs of 70# @ 29” draw
Thanks for this, Kramer. I learned a lot. Now I know why my 66# Ole Ben longbow shoots a slower arrow than my 50# Samick Sage, but the longbow seems to hit harder.
Love the research and development!!
You can figure in a multitude of variables but the main one is simply the direction or angle of released energy. The reason a recurve is faster than a longbow is that the energy is released in a tighter forward motion. The longbow's limbs release energy in an outward arching trajectory. Look at the newer compounds. The limbs are configured in a fairly extreme arch, therefore the energy is created mostly in the cams not the limbs and released in a forward motion rather than being wasted in the outward arching trajectory of the tips of the limbs. The more energy moving in the direction of the arrows flight, rather than at an outward angle, the faster the trajectory.
The physics behind the extra speed from draw length is the extra time acceleration is imparted to the arrow even if it's fractions of a second
I believe that the 40# at 30" increases poundage 2lbs per inch so it's no longer a 40# bow at 30"
hey man one of ur vids was the first "bow build" I ever saw about 2 yrs ago. now my garage and basement is packed full of all stages of wood drying it drives my wife NUTS!! but thank you! just wanted to throw that out there B4 I was that also that had to say if u use ur pliers(or channel locks.. I know brand name..) the other way they will work way better for u lol anyways cheers mang
edit B4 I was that asshole not also lol
I think in the traditional world where we can't attach as many things to our bows to dampen vibration, chasing speed had noticeably more cons to our performance. I talked to 4 different bowyers and researched for 5 years before I got my first and only custom bow and I chased silence and bow length (as I am a backyard archer first and a hunter second). Longer draw length is a longer powerstroke I'm 5'8.5" with a 29" draw so 50lbs is a long 50lbs to pull back but has a higher speed than 50lbs at 28" (atleast from tests I've seen). Thin limbs have less air resistance but the mass of the limbs is a huge component in arrow cast as well, you want light mass limbs with a heavy draw and thin profile so thicker limbs are good. I settled on my favorite design and performance for my needs being a 50s style recurve called the Toelke Super static because 64" bows are slower, but more comfortable for longer draw guys like myself. The thing is quieter than any compound or other bow I've been around but while that comes in part from the design, the real factor is my arrow mass being so high. That is how I got a super super whisper quiet bow, that still shoots relatively fast and is dead in the hand.
Cool video bringing a couple of key factors in for speed.
Kramer, have you studied also Yumi bows? They claim to be very efficient because less energy can turn to handshock, as the grip is set not on a node of the resulting resonance frequency.
I found no further notes, unfortunatelly, but I know they are onto something.
An efficient bow doesn‘t wobble much after the arrow left the string. Yes, weight of arrow/weight of limb is a key factor-but what if the frequency of the limbs is another factor for their effficiency?
Speed and smoothness are directly related. The smoother bow, the more energy is stores
Lower brace height means change in bow geometry. You will make a recurve bow more recurve and giving overall more energy storage even if the final draw weight is a bit less.
Draw graph of draw weight (y axis) vs length (x axis). Graph the weight at different points during the draw, up to max draw length.
Now colour in the area below that line.
The *area* coloured in represents the sorted energy in the bow.
Amazing video! Keep up the good work! Thank you!
reflex and recurve all make your bow faster, but that's only in comparison to another bow weighing the same, with the same amount of working limb, and shaped the shape that isn't reflexed or recurved. But just making a recurve on a bow can add extra weight and offset the benefit you get from recurving it. But if you don't put enough wood in the recurve portion, then the recurve can get pulled out as you use it. Making a fast bow needs to maximize the positives while minimizing the negatives. One of the fastest bows I build was a simple pyramid bow made from a board of cherry and backed with a layer of flax fibers. It got close to 200 fps, but then exploded one day out of the blue.
if 2 bows are different draw lengths but the arrows are both the same nd the draw weights are the same then you wont increase speed because running a longer arrow in the shorter length will also it down and compromise accuracy Also over drawing can add more pounds might get more speed but you risks bow damage raising brace height does not increase speed it actually reduces speed adds more stress to limbs causing damage to the bow
Very informative video. Hope you will be able to design a 90# warbow which can shoot 3GPP with >300 fps easily without breaking
Forget about maximum draw weight. That is like saying only horsepower is important for acceleration and not torque. Keep things simple. First, Energy = Force X Distance. The Distance would be the draw length but the Force is not the maximum draw weight, rather an average from zero inches of draw to maximum draw length. What you need to do for each bow is to come up with a graph of draw weight versus draw length. Start with 0.5¨ and measure draw weight all the way up to maximum draw length in 0.5¨ increments, now graph the results. The area under the graph is the total energy of that bow at that given draw length. Arrow velocity would follow that total energy figure much better than maximum draw weight. Keeping in mind that varying arrow weight would result in varying efficiencies. Heavier arrows will always extract more energy from a bow, i.e. more efficient. Once you have this graph for a bunch of bows you can begin to weed out the less efficient bow designs. For instance, let´s say you have two bows that at 28¨ draw length have very similar areas under the graph. Take those two bows and test them for speed keeping the arrow weight the same. The results may show that with the same area under the graph one shows higher arrow speed. Then investigate why. It could turn out that a bow limb or riser type may be more efficient. This will help you derive at the best bow design taking all variables into consideration. The goad would be to maximize arrow speed performance with the lightest draw weight, i.e. a more comfortable bow to handle and shoot accurately. Basically you would optimize the design. I would love to see those results of that analysis. Go for it.
That was good I'll have to watch it again.
Just curious to watch triangular shape limb. I think this simple extension will help to cut the wind and move the limb move faster.
I got to ask because I can't find it, but do you have a video of making limbs for takedown bows?
Here are my two cents... When it comes to energy stored, you should only consider energy put in by the draw, not the stringing, since it will not be transferred to the arrow.
@GeekBot makes a great point about why energy transfer can be affected by how much bending is happening until you reach brace height.
Instead of a brace height, draw length and draw weight one should consider the work stored in the system, which is just the force over the distance (eg actual draw weight at any given point along the draw length). This will then still get altered by your limbs - not only will their weight affect things, but how fast they want to spring back - since it is not instantaneous.
I’m curious to see how fast of a bow you can really make, fastest design, materials, arrows, etc
Awesome video, Kramer!
I’m struggling a little with my recurve bow getting only 175ish fps with approx. 45# draw weight and 27ish “ draw length
I’m shooting the Uukha Selenga limbs on an Oak Ridge Byron riser.
Can you say anything about a possible optimal riser design for those limbs? Or is it simply try try try - and then find out? :)
In engineering, a Moment (a physics concept about velocity) is equal to the force times the distance (Moment=force*distance). So, by making the limbs longer, but making the draw weight less, you can achieve a faster bow due to an ideal ratio between the force and the distance.
If you are able to find the sweet spot for speed in that ratio, you can find an ideal draw weight!
Materials and angles make it even more interesting, but this idea is a good place to start!
Acceleration the longer draw has more time to accelerate the arrow just as a short barrel pistol or rifle using the same cartridge have different velocity.
"Pounds", in this context, is a force being applied to the arrow when the string is released, but the question is for how low that force is being applied to it.
There are two things that matter:
1. The average pounds of force during the time that the string is pushing the arrow and returning to its rest position.
2. The amount of time this force is being applied to the arrow, to accelerate it.
It all comes down to applying as much force as possibly, consistently, over as much time as possible.
That is why a longer draw length means the string will be pushing the arrow for a longer amount of time.
But the problem is if the bow has most of its pundage of force at maximum draw, and very little during the first part of the draw.
Yes, it's quite complicated to calculate.
The "best bow" would be one that is as heavy to pull on the string in the beginning of the draw as when you're reaching max draw, which is of course very tricky to build.
I'm not sure, but I think this is what a recurve bow design is attempting to improve on.
All of this ignores the problem of air resistance, which isn't a very large factor in this context, though.
There is additionally the question of how quickly the bow is able to shed its energy, how quickly it can return to resting position. This could potentially bottleneck the arrow speed, otherwise. When we measure the poundage of the bow, we're measuring it while it is being drawn, not while it is releasing, which can be deceptive.
In fact, a really heavy arrow will be able to absorb much more of the energy from he bow, but this is of course a case of Newton's F=ma.
You did your homewerk on this one, very informative my friend 🍺🏹
First six minutes and something just clicked in my head, thank you
Hey Kramer, this was a great video. I really appreciate ya, Very interesting lots of great theories and it would be absolutely a blast to be working with you and testing all these different theories. I still have not heard back from you on whether you could build me a set of limbs or not. I’d really appreciate you getting back in contact with me. Thank you so much my friend take care and God bless.
Hey, I’ve been watching you for a long time always really enjoy your video and you are one of the reason why I started making bows and I’m gonna be making a bow for hunting soon but I’m curious did this bow shoot faster than your old fastest bow? The bad thing is, I don’t remember how fast that one shoot and what if you make the handle curve kind of like a bow that will that shoot faster, curve the handle away from you a lot and put Normal we curve limbs on it. And keep up the great work.
Sorry, supposed to have kind of like a horse bow handle
Brace height changes the power stroke. A longer power stroke means the arrow is accelerated for longer therefore going faster.
Amazing channel great explanation
please kramer i have a question about another thing about bows can we make a longbow with ipê without backed bamboo ?
Very cool findings!
Think about a high power bottle necked rifle cartridge. They use slow burning powder to build pressure as the bullet goes down the barrel. Longer Push!
Putting all these considerations together what bwould the ultimate bow be?
You never mentioned material reaction time. Different materials will return to least tension at different rates, so the type of material should be considered. In order for the rules you've stated here to apply, you'd have to be using the same materials in each of the various design changes.
He did mention that fiberglass was faster then wood and carbon fiber was faster then fiberglass. Not a great selection but pretty much covers materials we are likely to use.
That matters much less than you'd think. The real performance gain is the strength to mass ratio. Carbon is simply much lighter than glass for the same strength and therefore more efficient.
I think the more time the arrow attached to the string at the moment of release, the more power it will store from the bow limbs, so a longer draw length + a short brace hight should give more power, I think
So you may loose few bounds from the short brace hight, but smother draw and more stored energy.
Good video on a interesting topic.
To obtain a mongalese bow with a distance to 400yrds, what length and pull weight would I need?
This was a fun video!!!
How much recurve you have and how much recurve you use is a huge factor. I have moved the grip away from the string to keep from unwinding the recurves at brace height. The recurve is not just an interesting shape it’s a shape the allows the limb to store more energy mid draw. To use the recurve the string must be lying on the limb. When it does the bow seems shorter to the string and harder to pull, until the recurve unfolds then it’s the same as a long bow.
Just to be clear. If your bow is 45 pounds at 28 inch draw lenght, the poundage is more or les if your draw lenght is different than 28".
The dust or bug on your camera was funny but a little distraction 😂
I have a question that I know you know the definitive answer to. I'm 5'2" tall. Stocky guy with a very short draw length. I'm also 74 years old but that's just some information and not an issue here. The thing is I'm having to use bows somewhere between 55 to 60 lbs in order to get 40ish pounds at my draw length. I also set my brace height as low as possible to get, what I think, is a long enough power stroke on my arrows. Is this correct thinking on my part? My hunting bow now is an old Ben Pearson 52" 56# bow set at 6 inch brace height and it pulls 39 to 40 lbs at my draw length. BUT....this bow is more deflex than reflex. With a compound my bow was pulling 80 lbs peak and I'd found a brand of bow that favored a low brace height. Now my BP is a good bow but finding something to replace it with has me concerned that I may at some point have to have a bow custom built or just suffer the trade off in finding a "sufficient" off the rack bow. Whatcha think? That short Mountain Bow was looking pretty dang right up my alley kinda bow. I've scoured the WWW For answers to these questions and haven't had much luck. Anywho, thanks for your time. Love the vids and my new Shattered Bowstring.
Maximum velocity is determined by the string acceleration curve releasing the arrow at its peak.
Soooo, when can we place an order for this new design 😊
Another thing:
Every bow is already storing energy before you even touch the string.
Would be possible a design which can use ALL the energy pre-stored in the bow, for example using a loose string before shooting?