Primitive Archer
Main Discussion Area => Bows => Topic started by: scp on January 14, 2010, 12:38:57 pm
-
I think I understand. I think I understand. But what is the mass principle in one sentence?
-
I think I understand. I think I understand. But what is the mass principle in one sentence?
"Bows that weigh the proper ammount relative to the wood's density perform better." ;D
Just kidding. I don't know
-
Bows of the right mass aren't to overbuilt or underbuilt.
-
I am going to think about this and try to describe it in one sentence. " Using mass as a guide when designing a bow" .
Funny thing about this is I seem to be getting more interest on this from our Euro friends. I also see mass mentioned more often when stats are posted leading me to believe mass is being kept in mind.
Some of the obvious benefits to the mass principle for the everyday bowyer, it will quickly tell you if the wood has too much moisture, if it does you can't make target mass without excessive set.
It can also help you to design a bow, for instance a couple of years ago we talked about making an English longbow form boo backed ipe at 50# for flight shooting. An elb is a good one to use as an example because it has to meet specs for both width and depth. It is impossible to make an arc of the circle tillered elb from ipe over 66" long without becomming extremely whip tillered. The formula suggested the bow be about 60" long and weigh about 11 0z. 3 months later Dan Perry broke a 50# world record using thos exact demensions.
A good way to evaluate the mass principle is to reverse design a bow. Go ahead and choose the demensions like you normaly would. Instaed of selecting a target draw weight simply build the bow as heavy as you can without taking more than 1" of set from the original profile. When doing this the front view has to agree with the tiller shape, this is critical. If the limbs are pyramid it should have an arc of the circle tiller, if the limbs are paralell the bend should increase down the length of the paralell limbs. When you get finished see how close it comes to target mass.
I see lots of examples of bows below mass but in most cases they have dropped a lot of draw weight from being underbuilt. You see this a lot in heavily reflexed bows, they may not break but they get a bit rubbery.
Any questions I will always be glad to chime in. Steve
-
Badger, you are talkng as if the mass principle is "being guided by mass" and the totality of our knowledge in bow making. Nobody would say mass does not matter in designing a bow. But we need to be more specific about how to be guided by mass. Guided by your table in the Traditional Bower's Bible? How do we know that the table is correct or optimum?
Don't get me wrong. I'm not trying to challenge the principle or your understanding of it. I just wanna have a more handy exposition of the principle. Is it more like wisdom than knowledge?
-
Scp, no problem with challenging something. It should be challenged. If you read the chapter in detail you would see how radicaly the mass changes as the bow design changes. The table is only for two basic designs. There were several hundred bows built of all different types to test this out. It never will be exact but does claim to be pretty close. as working limb decreases mass increases. Two bows tillered differently put radicaly different amounts of strain on the limbs, yet you will usually see the same width recomendations for different tillered bows. The criteria for judging proper mass was based on how much set a bow would take and how well it performed speed wise. In other words if a self bow was shooting 170 fps and took less than 1" set I would say it likely had the right amount of mass well distrubuted. if a bow limb is too wide it not only creates extra mass slowing the bow down but it also is thinner and vibrates more causing even more energy to be lost. If a bow limb is too narrow it will often take too much set or in some cases not take set but become a bit softer and less stiff. I did several surveys beyond my own bow building on different bowyers regarding performance, set and mass. The formula is simple once understould but useless if only glanced at. I use it with every bow I make. Steve
-
Scp, when you said be more specific had you read the entire chapter. It is actually very specific about when and how to add or subtract mass depending on design. There is no substitute for being familiar with the wood you are working with, but the truth is even wood within the same spiecies varies greatly in density. Suggested widths for bows are usually safe numbers. It also deals with mass logic, in other words simply putting the mass where you need it. And it can help to dial in a design, especialy in the case of very dense woods. If you were to tiller out a 69" 50# ipe bow for instance at only 1 1/8 wide and compare it to the mass principle it might say you are 4 oz too heavy. If you were to make that same bow with a slightly more elyptical tiller and stiffer tips it would say you had the mass right on. If you like put up a couple of bows and I will show you how I would estimate the mass. Steve
-
The mass principle works. Steve, the mass of the bow I just built is 18 oz. Just about spot on with your chart in Vol 4. Jawge
-
Jawge, I was hoping a school teacher would chime in in my defense, I enjoyed that buildalong very much, bow came out nice, I was happy to see you not get carried away for that absolute perfect tiller which is almost impossible on a character stave.
-
Thanks, Steve. The bow shoots really well. Good stuff, Steve, the mass principle. Tillering character staves is much different from tillering straight staves. I didn't always build osage bows. They have to be trimmer than whitewood and BL bows. The mass principle helps a bowyer get there. Jawge
-
I read the chapter three times. Saying that the mass principle works is rather like saying justice works. But how? If you already know how to make a good bow, it works. Even if you have no idea how to make a bow, still you would think mass matters. But where exactly? It's well explained in the above mentioned chapter. But that means we need to know all about the bow profiles and tillering. We know how to apply it; but what is it that is being applied? Can it be expressed in a sentence? Mass matters but where exactly? Can anyone make a terrible bow that has the recommended weight in the table?
Does common sense work? If so, what is it? In a sentence, please. ;-)
How about in a paragraph? Let's see. If you already know how to make a good bow in theory, say you have read the Traditional bower's Bible three times, you can use the weight of the bow you are making to figure out when you are done, when you need to scrape the side, or when to apply the sound bow design principle in tillering. What really matters is where we put the mass. Do we even know how to measure the weight of a particular section of the bow? Not exactly. So we use the width and the thickness as guides. Does that mean the width and the thickness natter? Of course. But how?
One of the specific sentence about the mass principle is that it assumes that "for bow making purposes all wood is equal." Is that why we look for certain kinds of wood or a particular stave with certain characteristics?
Of course, we can make the principle work. And I do believe the underlying intuition is correct. But to make it work for everyone, we need to know what it is. Is it just common sense about the total mass and its proper distribution in a well designed bow? If so, can it be expressed in a succinct paragraph?
-
SCP, you seem to have a pre-occupation with shortcuts. When we speak of mass in bows we are speaking of width most of the time. One of the most common questions you will see on any bow making forum is how wide to make a bow or how long to make a bow etc. There is not all that much difference in how different woods perform but there is some difference, yew for instance can be made a bit lower in mass, some woods you might want to lean toward the high side but for the most part the mass numbers given will give good results. I don't totaly follow your question, but if I could have expressed it n a sentence I would not have written a chapter on it. The prnciple take a bit of practice and study to learn but once learned is very simple.
After reading your post again I can see you might need to go back and reread the chapter. Sometimes things will make sense when you have more experience. There is a portion of the chapter dedicated to Mass logic that answers several of your questions.
The best I can say is the next time you start a bow send me an IM and we will do a buildalong together using the mass principle. We could do it right here in the forum if you like. I think you would have fun with it.
Steve
-
I'm trained in philosophy and law. It's almost natural for me to ask people to make themselves clear and succinct, if they don't mind. After several dozen stave selfbows, I think I know how to makes simple selfbows. I'm not trying to discredit the mass principle. I just want to see it expressed in a short paragraph. If you are comfortable with the exposition you have made in the book, I guess it's up to me to come up with a better one. Maybe after making a few hundred bows?
-
Steve, I am trying to remember if you discuss heat-treating, and how it jives with the mass principle. If a finished bow is heat treated, it will often pick up several pounds. Does that mean the mass principle needs a fudge factor? How do you deal with this?
I'm very impressed with your willingness to keep answering everybody's questions; you're obviously a man of character.
Can I take a stab at the one sentence thing? "All (usable bow) woods are equal when expressed as elasticity per unit of mass."
-
I think "getting the most(performance) out of the least (mass)" pretty much covers it.
-
Zen, heat treating does slightly reduce the optimum mass. Backing a bow via the perry reflex method also reduces the mass by about 10%.
One more stab at one sentence: Optimum mass for any particular wood bow design is predictable and attainable.
Steve
-
Thanks, Steve!
I'd like to volunteer to do that mass principle buildalong with you if scp declines. I have to wait at least another week for my sapling stave (already roughed out) to mature.
-
Anytime Zen, it would be a pleasure. You just decide the design you want and we go from there. Steve
-
Awesome! I'll be in touch.
-
I for one would very much enjoy seeing it as a thread. May not comprehend it all but would enjoy the brain calisthenics. So please when you two run your experiment please post it to the board.
Thank you,
Mike
-
all mass is used with nothing to waste and nothing too stressed...gut
-
Gut, i like that one!
I just built a 40#@16"X40" long stiff handled bow, I didn't build it by the mass principle but used the tecnique that developed the principle, I just now weghed it and it was 7.7 oz, mass principle called for 7.5 oz. Close enough. I am going to use it for a crow killer with 200 grain arrows, Steve
-
the lighter the limbs the faster they move, so I would say it just means make the limbs as light as possible , getting rid of all surplus wood that doesnt do anything ( thats a bit more than 1 sentence)
-
One more stab at one sentence: Optimum mass for any particular wood bow design is predictable and attainable.
Let me be a little more constructive.
IMHO the mass principle say that, if we assume that for bow making purposes all wood is pretty much equal, the optimal total mass of a bow is predictable and attainable through the use of the table obtained through the experience of many good bowyers. Of course, it also matters a lot how we distribute the mass. There we should use the sound bow design principles, especially concerning the proper tillering for a specific profile. We also need to know how to adjust the figure in the table according to the length of the nonworking grip, the unbending tips, and etc. How to do this is in the directions after the table.
[Here we need to put the table and the directions.]
This principle is a work in progress. The proper issue is not whether it works or not, but how we can make it work and refine it to make its application easier. I still don't know how to use the total weight in figuring out the proper distribution of the mass. Is there any way we can refine the principle to tell us how to do it, other than invoking the sound bow design principles? I guess the mass principle is a part of the design principles. If so, what does it say about the proper distribution of the mass by itself?
-
Scp, it is becomming more and more obvious that you either did not read the chapter of did not comprehend it. All the things you mentioned are well covered in the chapter. The distribution of the mass is determined by width only, the depth is what you use to control your bending. Mass logic simply means that the full drawn side profile of a bow should agree with the front view of a bow. You make up a design and I will give you the mass and the tiller shape in about 3 seconds. Steve
-
Better yet, let me e email you a calculator, you feed in the handle size, the length, draw length, and draw weight, it will give you back the mass needed, you control the mass by controlling the width. Now to use the calculator you have to know how to manipulate the stiff handle area number to accomadate your tiller shape, and the draw length to accomadate stiff tips. Steve
-
the lighter the limbs the faster the move, so I would say it just means make the limbs as light as possible , getting rid of all surplus wood that doesnt do anything ( thats a bit more than 1 sentence)
Thanks. That must be a major part of the mass principle. If so, it might also mean that the tips need to be as light as possible. Does the mass principle say anything about the proper length of the unbending tips? All other things equal, is it correct that the unbending tips should be as long as the optimal table allows? How do we know when to scrape the side of the working part of the rims instead of lightening the tips? Can the mass principle be rephrased to help us in answering the question?
-
Steve, I am following this closely, and it occurs to me that the principle can be espressed (perhaps more simply), through specific gravity and surface area.
That is, since unbending handle is just a complication to the mass principle, can we not eliminate it all together? Would the surface area of the belly of the working limb be a good predictor of optimal design if the specific gravity of the wood is known? I suppose calculation of the surface area could be as complicated as accounting for handles anyways...
-
The distribution of the mass is determined by width only, the depth is what you use to control your bending. Mass logic simply means that the full drawn side profile of a bow should agree with the front view of a bow.
I don't think the first sentence above is correct. The relative distribution of the mass can be measured by using the width and the depth of sections.
As for the second sentence, it appear that the total mass would be optimal if "the full drawn side profile of a bow should agree with the front view of a bow." Does that mean the mass principle is a way to tell whether the profile agree with front view?
-
Better yet, let me e email you a calculator, you feed in the handle size, the length, draw length, and draw weight, it will give you back the mass needed, you control the mass by controlling the width. Now to use the calculator you have to know how to manipulate the stiff handle area number to accomadate your tiller shape, and the draw length to accomadate stiff tips. Steve
I'm afraid we can control the mass by controlling either the width or the depth or both. I agree that given the profile/style and "the handle size, the length, draw length, and draw weight," we can probably figure out the optimal mass of the bow. That means, as you have written in the book, the mass principle can tell us when to stop tillering and even when to start scraping the side instead of the belly, as doing so would change the mass much more without affecting the draw weight too much. But it probably cannot tell us whether we need to lighten the unbending tips instead of scraping the side of the working part of the limbs. Can it? Better yet, can we refine the principle to do so?
-
SCP, you are changing quotes, I said mass is determined by manipulating width, you said mass is measured by width. Two different things.
The amount of thickess you remove from a bow close to tiller is very small, the amount of width that might be removed can be significant with a much smaller effect.
The book clearly answers all the items you have addressed but I will topuch on them anyway.
There is no possible way to make a table that could allow for all bow designs, so the best way to it is to manipulate certain pertinent inputs.
Lets say you build a bow with an 8" handle and fade area which is kind of standard, this same bow has paralell limbs, mass logic or common sense or equal distribution of strain dictates that a paralell limb bow should not have a round tiller, it should be elyptical, so you change the handle figure to 10" even though it is really 8" to compensate. Lets say you like stiff tips on a bow so you leave the last 10" of the tips not bending, how much further would the bow draw if those last 10" were bending? Probably about 2" or so. So even though you will only be drawing the bow 28" you use a figure of 30 or 31 " for your draw length, this will allow a bit more mass for stiff tips. Learning to manipulate the handle and draw length figures are the key to the principle working. Not very hard actually, with extreme elyptical tiller you might use a 12" figure and extreme stiff tips you might add as much as 4" to the draw input figure. Seldom goes beyond that and estimation will get you plenty close enough. Steve
-
For me, the mass princple is closely associated with set. If I remove enough wood from the limbs so I'm getting a small amount of set (when all other contributng factors causing set are minimized), then I know the limbs are as light as possible, thereby opimizing performance. That's one of the biggest reasons I think a bit of set is a very good thing.
-
Actually one of the biggest msconceptions about the principle is that I am promoting low mass limbs. It is more about having enough mass and having it in the right places, If a bow took set in a paortion or the entire limb it is because it didn't have enough mass ( width) in that particular area to support the amount of bending it was asked to do. When we design a bow we cut out the front view of the bow, at this point we should allready know what we want the tiller to look like. The thickness controls how far a piece of wood can bend before it takes any set and the width controls how far it actually will bend when drawn. Steve
-
Badger, I am not saying that you didn't say it well or fully in the book. All I'm asking for now is a simple paragraph we can use to understand the principle and to learn how to apply it, even if we cannot express it in a sentence. Of course, what I have said in my version is all in the book. Otherwise I would be calling it my mass principle.
I think you would agree with me that the mass principle is not a fixed and explicit rule but a working hypothesis that seems to be working so far or a work in progress that can be made to work. Either way, according to the mass principle, given a particular specification of a bow, its optimal total mass is reasonably predictable and attainable.
We can stop there or we can make it also deal with the proper distribution of the mass. You appear to opt for the latter as you say "It is more about having enough mass and having it in the right places." Now we need to say what it means to "have enough mass in the right places." You say "The thickness controls how far a piece of wood can bend before it takes any set and the width controls how far it actually will bend when drawn." If this is the case according to the mass principle, of course when all other things are equal, what is the relationship between the mass and the width and the thickness that makes it so?
You also said, "The distribution of the mass is determined by width only, the depth is what you use to control your bending." Does that mean we cannot control the distribution of the mass by changing the thickness?
-
Yes, you ignore thickness when distributing mass, thickness is never negotiable if you have a particualr tiller in mind. I think it is beyond a work in progress, not perfect for sure. But well in use long before it was published. Steve
-
Yes, you ignore thickness when distributing mass, thickness is never negotiable if you have a particular tiller in mind.
That sounds like an oversimplification. Do you ignore thickness when you try to properly distribute mass in an ELB style bow? You must be talking about the case when you have reached at a certain stage of bow making, say when you have reached the target draw weight at the target draw length but still the total mass is a little high. Does that mean we are not allowed to scrape the belly and heat treat it?
-
Yes thats what it means, if you want to remove mass you remove it from the sides of the bow, always maintaining your design. If it is a bad design the mass formula will tell you long before you get to that point.
An elb is an excellent example and played a big part in the final stages of the formula. A elb has to meet certain criteria for depth to width proportions. The thickess can be anywhere from a 7/8 ratio to a 5/8 ratio minimum. In my opinion a properly made elb never bends in an arc of the circle but bends more in an elypse. The recomended demensions of an elb support this. If an elb is too high in mass you simply scrape down the sides a bit as you tiller till it starts comming into line. If by chance the wood is a bit too dense for the length and draw weight you chose you simply make the tiller slighlty more elptical and it will raise the number for projected mass and maintain performance. Steve
-
Scp, just for the ehck of it lets have a very non tecnical discussion about wood and bending wood.
Lets say you want to bend a piece of wood 6" and you don't care how much effort it takes, the width is fine like it is. You want that same piece of wood to be able to treturn to it's original shape when you release it. Some guys would start thinning the piece of wood and pushing on it till the wood bent 6". Some guys would push a little bit and see if it returned ok and then push a bit more and check back again, if it didn't quite return they would take a bit more thickess off, repeating this till they hit the 6" point. The other guy might make it way thinner than he needed and get his 6" with no problem the wood returning perfectly to it's old position, or it might just break when he was pushing. In other words he was just guessing. For the most part the inside circumference of a bend has to stay with in about .7% of the otside circumference, some woods may go as high as 1%.
When we make a bow we have very specific goals, we know how far we want to bend it and we know how much effort we want to expend doing this, we also should know how we want it to look when bent. The goal when making a bow is not to avoid breaking it as much as it is to stay within the elastic limits and not take too much set. I have seen great looking bows with lots of reflex and great profiles that shot like dogs because the wood was so rubberized from being overstressed.
Most of the demensions given out on line are pretty close and work pretty good because there are lots of guys experiemnting here making bows and they know what works, but if you want to start finessing your game a bit you try to eliminate as much guess work as possible. Every little change you make in a design changes the optimum mass needed for that design.
One of the other goals when making a bow is to even out the stresses on the limb as much as possible. The only way to do this is to make the bend match the thickness. Lets say you have a 28" long limb, 16" of that limb is straight and the last 12" tapered to 1/2". You are going to scrape that limb down in thickness until it bends the same thrughout the limb most likley. It will look nice but far from being evenly stressed because you have made the limb thinner down its length, in order to make it evenly stressed it has to bend more as it progresses toward the tapered area. If you wanted a nice circular tiller the pyramid style even thickness design is what should have been chosen.
Everything you do to a limb that shortens the working area causes the working area to be under more stress, making it wider and thinner is the only way to compensate. A childs bow of only 10# draw weight is under no more or less stress than the curviest 80# bow you have ever seen, wood will only take so much stress and it is relative. The mass principle just keeps these things in mind when recomending how much wood you need to make a bow. Steve
-
Badger, this is some interesting stuff, that you have presented. The take that I'm getting here, is that the Mass Principle helps in building a bow that is neither over or under built for a particular design, leaving or taking away wood in the right places for a given tiller, to achieve optimal performance. Am I seeing this correctly?
-
Lombard, yes that is the goal. It is on the conservative side for obvious reasons. If anyone is interested in downloading the calculator send me your e email address, all you do is fill in a few blanks and it spits out the number. The calculator is microsoft excel. Steve
-
scp, never stop questioning. I didn't chime in earlier because you had Badger to answer your questions. You had Badger to badger. :) I used to love it when my students questioned me. I used to tell them to keep at it even if I sounded aggravated which I wasn't (not usually LOL). I'm a retired chem teacher. Here is my synopsis of the mass principle. The mass principle is a technique that allows the bowyer to manipulate the mass of the bow in order to maximize performance. Thus a 50 # rigid handle bow with a mass of 28 oz is vastly over built. It's probably too wide. Around 18 oz is better. The bowyer can control the mass by reducing the width. Osage is one of the densest North American bows at 0.8 g/cc. Density is mass per unit of volume Therefore, it should be trimmer than a hickory bow at around 0.7 g/cc. Either bow would have the same mass just that the hickory bow needs more volume to get that same mass. The mass principle is quite scientifically grounded. Jawge
-
Thank You Jawge, I thought of you throughout this entire exchange and how patient you probably had to be. I am a diesel mechanic by trade so it doesn't come natural to me. Steve
-
Thank you. Badger, how'd I do with the synopsis? Jawge
-
I liked it! Steve
-
Jawge, a principle must be much more than a technique. I BELIVE in the underlying intuition. But unless you formulate the principle to make it falsifiable, you are not there yet.
Badger, I don't hunt. Not even fished lately. But I shoot at targets. I chase "principles" and understanding. I have no doubt you know what you are doing. But you might be calling the totality of your experience the mass principle. Of course, bow making is an art, not science. Still if you are going to call something a principle, you might have to provide a succinct exposition that can be used by everyone.
Your said "you ignore thickness when distributing mass." What do you mean by "when distributing mass"? It cannot mean "when we are tillering," can it? How can we ignore thickness when we are tillering? Does it mean "when we are applying the mass principle after most of the tillering is done"?
You also said, "The distribution of the mass is determined by width only." Then I have to ask when? When we are designing a bow? You might be thinking about when the bow is almost finished and you are trying to apply the mass principle to that bow. Why can't we determine the proper distribution of mass by thickness when we are designing a new bow?
Don't get me wrong. I'm not saying you are wrong. I'm saying good bowyers need to make their assumptions more explicit. Knowledge mining is never easy and can be quite irritating sometimes.
The mass principle in a paragraph, anyone?
-
SCp, with a lot of mathematics you could apply the mass to the demensions of the bow relatively close before starting but it is not neccessary and would never be as accurate as just zeroing in as you build the bow, forget about the thickness of a bow, ignore it! That happens when you tiller. All you are doing with the mass pricilpe is adjusting the width on a pre-determined design, nothing more. If the mass is way off then you adjust the design but only if neccessary. I hope I can get you to try this. It is actually very simple once understould. Steve
-
The mass principle says that it always takes the same amount of wood mass to do the same amount of work in a bow. But, of course, how can it be otherwise? Still, is this principle falsifiable?
-
"Jawge, a principle must be much more than a technique. I BELIVE in the underlying intuition. But unless you formulate the principle to make it falsifiable, you are not there yet."
Please explain what you mean. I detect an underlying assumption here on your part but I don't want to elaborate until your philosophy on bow making is clear to me. Suffice to say, that in my view, building bows is NOT an exercise in the scientific method. So you have a log stave in front of you what do you do to turn it into a bow?
Also, I just built a 51# rigid handle osage bow, drawn 26 in that happens to fall at 18 oz in mass. I did not set out to achieve that mass figure. It just happened. I checked the mass to tell Badger. No other reason.
"Don't get me wrong. I'm not saying you are wrong. I'm saying good bowyers need to make their assumptions more explicit. Knowledge mining is never easy and can be quite irritating sometimes.
The mass principle in a paragraph, anyone?"
I gave you the mass principle in one sentence and then explained it in a post approved by the author of the mass principle itself (Badger). LOL.
"The mass principle is a technique that allows the bowyer to manipulate the mass of the bow in order to maximize performance."
Now either you don't understand (I can't see your non verbal cues like I did when I was teaching so I can't tell) or you don't think the mass principle is a viable technique. It is a technique. Is the name a problem? This is not science, scp. This is art. :) Jawge
-
But it probably cannot tell us whether we need to lighten the unbending tips instead of scraping the side of the working part of the limbs. Can it? Better yet, can we refine the principle to do so?
scp, the formula isn't supposed to tell you to use stiff tips or rigid risers. It tells us if we have done them properly. If you have more wood on the unbending tips than is needed to keep them unbending, it will tell you that you are over weight. Steve mentions that he doesn't advocate lighter bows, and it is true. Some of us make bows too light/narrow, and the formula helps to prevent these occasions also. I have previously thought that some species, because of their superior qualities could cheat the formula and have less weight. Steve helped me with the formula on one such bow. I came in about 1 ounce lighter than Steve projected. I thought it was close enough since this was only about 5% of total weight. The bow held up for 4 months then started showing signs of damage. Steve is as humble as he is helpfull so I will say it. This mass principle is extraordinary. It is probably the best scientific tool available to let a bowyer know if he is getting the most from a bow design.
One paragraph.....
All woods are not of even density. All trees of one species are not of one density. Badgers bow mass principle helps us to refine design to fit the particular piece of wood, not the general species or type of wood. The formula uses design characteristics such as but not limited to, length, riser style, amount of reflex/deflex compared with draw length and draw weight to help us to eliminate excess wood that would decrease performance. It also uses those same principles to help us not make bows that will not stand up to the strain that we are putting upon the wood by building to light, too narrow, or too short of a bow by telling us when we are asking too much of the wood.
One last thing. The principle is more accurate than the interpretation by the human. If there is an error, it is in the human inturpretation.
-
scp, no, it is not and that's why it can be called a principle. The underlying principle is the concept of density (d=m/v). Osage (at 0.8 g/cc ) is going to have the same mass in a smaller volume when compared to hickory at 0.7 g/cc. Practically speaking, without even considering the mass principle, the reason why the bowyer should begin to narrow the limbs is that too thin limbs can break easier. So when I see a limb unresponsive to belly removal I slowly begin to narrow the limbs. Keep the questions coming. :) jawge
-
Justin Snyder, you are talking about the PRIMARY mass principle. "According to the mass principle, given a particular specification of a bow, its optimal total mass is reasonably predictable and attainable." Nobody seems to have any problem with that.
But Badger goes much further than that. He thinks the principle is useful in predictng or prescribing the proper mass distribution in a well made bow. When I ask him how, he just invokes the sound bow design principles. I'm sure mass is relevant in there somewhere somehow. But where, when, and how?
-
scp, no, it is not and that's why it can be called a principle. The underlying principle is the concept of density (d=m/v).
"A hypothesis, proposition, or theory is 'scientific' only if it is falsifiable."
http://en.wikipedia.org/wiki/Falsifiability (http://en.wikipedia.org/wiki/Falsifiability)
Are you trying to say that the mass principle is a semantic one?
-
Maybe priinciple is the wrong word, I will call Jim Hamm and hav him recall all the books immediately so we can change that word and reprint all the books. I believ it is falsifiable, build a bow 20% under the recomended mass and see how it performs, or build it 20% over the recomended mass and see how it performs. The whole idea here is wether or not it works! It seems to work for me and several others, why are you so stuck on definitions. No claim was ever made that it was exact science, it is just another tool used to attain proper demensions, I am not going to spend anymore time defining a word. Try it, if you ike it use it, if you don't like it, don't use it. Steve
-
scp- wow. You must have been on your High School debatig team. :D
-
science, science, science......maybe you ought to read the headline banner, something about "primitive archer". I think I'll see if I can book some time with some stupid oldworld bow-maker. You know, the one that does it by feel and devotion to the craft and probably aint got a pencil, ruler, bandsaw and for sure no desire beyond making a good solid bow. He probably dont even know what a chronograph is let alone what it's used for. I mean hell who wants to settle for something that kills food, shoots where you look, etc. etc.
I hope you get all the stupid people like me good and confussed, because God forbid somebody wants to take up the hobby for fun. Why dont you just get with Socrates and debate how many fairy's can dance on the head of a pin? I hold 2 United States Patents in the field of anti-ballistic armor, a published author blah, blah, blah (and so what?). For the life of me I dont see why this is even an issue. I thought there were bows around for at least 10,000 years and never realized that all them bows were crap up untill the "Bibles" got published.
There are a few of us stupid, crappy bow builders that sort of enjoy the exploration of the process, and the mystery of it.
half eye
-
Halfeye, I agree with you 100% on a personnal level. Bow making is kind of a lost art that we have been rediscovering. Looking back at some of the old designs it it obvious these guys knew exactly what they were doing and very good at doing it. We don't do it here for survival we do it as a hobby. They may have spent a lifetime or a particular civilization or village may have spent generations developing and improving one style of bow. As hobby bow builders many of us would like to experiement with a lot of different designs from a lot of different woods. Little clues and the logic that goes into designing a bow is helpful, without the combined input from the hundreds of bowers we have today it wouldn't be likely we could take it as far as we have in our own lifetime. I have settled into favorite designs of just basic stave bows, straight and basic. But the journey has been fun never the less. Steve
-
Steve, I am trying to remember if you discuss heat-treating, and how it jives with the mass principle. If a finished bow is heat treated, it will often pick up several pounds. Does that mean the mass principle needs a fudge factor? How do you deal with this?
I'm very impressed with your willingness to keep answering everybody's questions; you're obviously a man of character.
Can I take a stab at the one sentence thing? "All (usable bow) woods are equal when expressed as elasticity per unit of mass."
Wood is comprised of a significant amount of air trapped inside the cells. Dry heat forces some of this air out especially on the belly's surface wood. This would make the wood more dense and generally speaking the denser the wood the higher the compression strength.
-
science, science, science......maybe you ought to read the headline banner, something about "primitive archer". I think I'll see if I can book some time with some stupid oldworld bow-maker. You know, the one that does it by feel and devotion to the craft and probably aint got a pencil, ruler, bandsaw and for sure no desire beyond making a good solid bow. He probably dont even know what a chronograph is let alone what it's used for. I mean hell who wants to settle for something that kills food, shoots where you look, etc. etc.
I hope you get all the stupid people like me good and confussed, because God forbid somebody wants to take up the hobby for fun. Why dont you just get with Socrates and debate how many fairy's can dance on the head of a pin? I hold 2 United States Patents in the field of anti-ballistic armor, a published author blah, blah, blah (and so what?). For the life of me I dont see why this is even an issue. I thought there were bows around for at least 10,000 years and never realized that all them bows were crap up untill the "Bibles" got published.
There are a few of us stupid, crappy bow builders that sort of enjoy the exploration of the process, and the mystery of it.
half eye
half eye
Aren't you the guy that posted something about making a bow from a picture using some kind of a formula?
-
I believ it is falsifiable, build a bow 20% under the recomended mass and see how it performs, or build it 20% over the recomended mass and see how it performs.
Me too. The PRIMARY mass principle is falsifiable. Or at least, it appears that we can make it so.
The mass principle says that it always takes the same amount of wood mass to do the same amount of work in a bow.
If we wanna go further and talk about the mass principle concerning the proper distribution of mass in a well made bow, we probably have to talk about the relationship between the mass, the width, and the thickness of each sctions of the bow. You have been making several interesting statements about it. I don't think you are wrong. But I do believe that many of the underlying assumptions or qualifications have to be made explicit. I repeat:
Your said "you ignore thickness when distributing mass." What do you mean by "when distributing mass"? It cannot mean "when we are tillering," can it? How can we ignore thickness when we are tillering? Does it mean "when we are applying the mass principle after most of the tillering is done"?
You also said, "The distribution of the mass is determined by width only." Then I have to ask when? When we are designing a bow? You might be thinking about when the bow is almost finished and you are trying to apply the mass principle to that bow. Why can't we determine the proper distribution of mass by thickness when we are designing a new bow?
-
SCP, when using this formula width and mass are almost interchangeble. I don't even consider thickness here in anyway because it is not negotiable, I do know a gentleman who can prefigure a bow's thickess and width and mass but is is very difficult, innaccurate and not really useable for most of us.
The distribution of the mass and the tiller shape are predetermined by the bowyer at the design stage before the bow is started.
All the formula does is to direct the bowyer in the final stages to fine tuning the width. Steve
-
He thinks the principle is useful in predictng or prescribing the proper mass distribution in a well made bow. When I ask him how, he just invokes the sound bow design principles. I'm sure mass is relevant in there somewhere somehow. But where, when, and how?
It does...... Maybe you should go back and read it again. Then use it to build 6 or 7 bows and you will begin to understand. Nobody ever learned to drive by reading a drivers handbook.
-
Hey Marc,
Ya that was me...you can do proportions with a stick but the formula was the easiest way to explain it and it sure was not put forward as a "principle".
I am well aware I'm not part of the old boys, I didn't write a chapter in Bowyers Bible IV, I don't have a website to sell bows and I know you are one of the "Global Moderators"......the other thing I'm well aware of is your sarcasm....and will give it all the respect that it is due.
half eye
-
Badger, I agree. That's why I have said earlier, "as you have written in the book, the mass principle can tell us when to stop tillering and even when to start scraping the side instead of the belly, as doing so would change the mass much more without affecting the draw weight too much."
Believe it or not, I think we can milk the mass principle a little more than we have done so far. I suspect it is implicitly used in the sound bow design principles. But saying that "the distribution of the mass is determined by width only" seems to be too blunt. In the pyramid style bow, the distribution of mass is usually determined by width. If so, we can use the way where energy is stored in a bow limb (pp. 116-117 of TBB4) to set the proper width of each sections, according to the mass principle. But in an ELB style bow, we might use the thickness instead. In both cases, we will be using the mass principle to put the proper amount of mass in a particular section as required by the amount of work it has to do.
-
Half eye, if you look closely at the few remaining remnants of primitive designs that we have to work with you will quickly see they are very well engineered. Better than we do today. If you study them a bit it becomes apparent there was quite a bit of logic involved in them and I suspect this was discussed by bowyers of that day similar to the way men have discussed hunting and war weapons throughout history. The english long bow is almost perfectly designed for what it does, the mollabet and holmgarde are also good examples.
One that had puzzled me for years but I think I finaly figured out is the Solomom island bow. These bows at a glance seem to be contrary to any kind of logic. But when examined closely are absolutely stunning in their design.
A solomom bow is extremely long in the upper limb and very short in the lower limb, most long bows like this would have a very heavy draw weight and very long draw, these are medium weight bows with average draw lengths. A bow like this would be extremely shocky and inefficent with a normal weight arrow. The bows are also made in an s shape which doesn't seem to make sense.
These bows are used for fishing as the fishernman wades through shallow water, the short bottom limb is obvious it needs to stay dry. The top limb is not so obvious, it is wide and thin with a very narrow tip, this would vibrate a lot and loose most of it's energy before it ever got to the arrow. I suspect that these fishing arrows were very heavy so they could penetrate water and only had to shoot a few feet. The length of the bow would store a lot of energy and offer a smooth draw, the heavy weight of the arrow would allow the bow to be efficient regardless of it's wide thin limbs. They would also dry out faster if they got wet for some reason. The curve in the bow used to puzzle me, I think now it is the equivalent to a sight window so they could see their fish. They dont anchor these bows at the face like we do shooting a deer. I have to wonder how long it took them to figure all this out. They obviously passed it down from generation to generation and improved on it as it went. The bow eveoloved just as animals do in special circumstances. For us hobby bowyers to fully get the experience we are looking for we pass info back and forth and sometimes look for shortcuts. Understanding the logic behind the bow is the key to proper design. Steve
-
Again, scp, your initial assumptions are flawed. Almost any human activity involves science but building bows is NOT science. and therefore needs no independent testing. It's art. I also believe the mass principle is verifiable but if it isn't applicable all the time so what? It's a viable technique. Beginners are lucky to get a bow made. Forget about worrying about mass considerations. Jawge
-
Jawge, I already said and believe that bow making is an art, not science. I would even say that it should remain that way! That does not mean we cannot use rigorous reasoning to understand what goes into making a well designed bow.
I don't know and haven't tried to figure out how they did that, but we even have the chart showing where energy is stored for a D-longbow. That means, using the mass principle, we can design a decent bow rather easily.
This is the chart from p. 117 of TBB4:
Inches from center --- energy
0 - 7" 30%
7 - 14" 27%
14 - 21" 22%
21 - 28" 15%
28 - 35" 6%
I bet most well made bows will have the similar mass profile.
-
So, scp, you all set? :) Jawge
-
Hey Marc,
Ya that was me...you can do proportions with a stick but the formula was the easiest way to explain it and it sure was not put forward as a "principle".
I am well aware I'm not part of the old boys, I didn't write a chapter in Bowyers Bible IV, I don't have a website to sell bows and I know you are one of the "Global Moderators"......the other thing I'm well aware of is your sarcasm....and will give it all the respect that it is due.
half eye
Ah so you recognize the fact that it was well deserved. Good
-
So, scp, you all set? :) Jawge
Exactly
-
This has been a pretty good read. Of course, monitoring the mass of a bow won't design the bow for you but it is another reference point that has been useful for many. I see it as a tool that takes a similar approach as an arrow spine chart. There is a basic assumption that correlates very well to an easy to measure property, then a number of incremental adjustments to suit the particular circumstance. Steve has done a great job with this in it's application to wood bow building.
Whether it is intended or not, there is plenty of SCIENCE to support this mass idea. Wood from trees is amazingly consistent. There are several places in research publications from the US Forest Products research where it closely correlates most engineering properties of wood to the density (Elastic modulus, Maximum Strength in Bending, etc.). So, I guess you could say the mass/density idea has been used for a long time for designing wood structures. With these same properties you can calculate the minimum amount of bow wood required to store the amount of energy for a given draw weight and draw length.
Or, you can just bypass all the intermediate formulas and calculations and take Steve's approach that the minimum amount of wood needed to store the energy for a given draw length and draw weight is proportional to the mass. That is pretty much it. I like it.
-Alan
-
Jawg, I make bows for physical exercise. After making several dozen flat bows mainly in pyramid style while reading the Traditional Bower's Bible a couple of times, I'm asking myself whether I wanna make bows for mental exercise as well. Definitely not, unless I have to! Don't make me, please. ;-)
-
Not I, scp. I did 35 years of mental exercise. I just make them and shoot them. :) Jawge
-
Jawg, I make bows for physical exercise. After making several dozen flat bows mainly in pyramid style while reading the Traditional Bower's Bible a couple of times, I'm asking myself whether I wanna make bows for mental exercise as well. Definitely not, unless I have to! Don't make me, please. ;-)
I don't do it for mental exercise, do it for a mental break.
-
Jawg, I make bows for physical exercise. After making several dozen flat bows mainly in pyramid style while reading the Traditional Bower's Bible a couple of times, I'm asking myself whether I wanna make bows for mental exercise as well. Definitely not, unless I have to! Don't make me, please. ;-)
I don't do it for mental exercise, do it for a mental break.
ME TOO!!! And what a mental break it is... 8)
-
Half I pointed out they were making bows just fine for the last 10,000 years with no need for the bowyers bibles and he was right on when he said that, instead they were using 10,000 years of experience that was lost a while back. The quality of bows has come up immensely in the last 10 years I think because of internet sharing of experience. a new guy can come in today and be making excellent bows in a very short amount of time. If he chooses he can still strive to make them better. If not he can just enjoy the journey. I enjoy both, I have the greatest appreciation and respect for the ancient bowyers, I can't say it enough times, they really knew their stuff. Just for the record, in some cultures bows were not measured by draw weight they were measured by mass weight, so it is nothing new. Steve
-
Half I pointed out they were making bows just fine for the last 10,000 years with no need for the bowyers bibles and he was right on when he said that, instead they were using 10,000 years of experience that was lost a while back. The quality of bows has come up immensely in the last 10 years I think because of internet sharing of experience. a new guy can come in today and be making excellent bows in a very short amount of time. If he chooses he can still strive to make them better. If not he can just enjoy the journey. I enjoy both, I have the greatest appreciation and respect for the ancient bowyers, I can't say it enough times, they really knew their stuff. Just for the record, in some cultures bows were not measured by draw weight they were measured by mass weight, so it is nothing new. Steve
I appreciate your hard work Steve. I really enjoy pushing, and have broken less bows while improving performance since using your bow mass calculator. For me, pushing the limits is part of "just enjoying the journey."
-
Justin, I appreciate that. I thin all of us enjoy this in different ways, none of them are bad. Steve
-
Steve,
I'm building a set of bows for a husband and wife. The 48# bow came in right about where your table in TBB4 says it should. The 30# bow, however, came in about 2 oz light. It does not seem underbuilt and didn't take any noticable set. Does your formula require some adjustment in the lighter range?
-
Gordon, not really should remain pretty close down to 35#. It is a bit conservative. Just for the heck of it could you post the bow and let me figure the suggested weight without you telling me what it was. Give me the draw weight, front view ( description or picture) handle size. Draw length and tiller shape. There are several woods I tend to come in light with all the time, yew, cherry, cedar, are a few of them.
-
Here it is Steve. Draw weight is 30# at 26", 4" handle with 2.5" fades, length is 63.5" ntn. The tiller is more or less circular. The wood is hazelnut which seems to have a similar density to yew.
(http://mysite.verizon.net/res0oeio/Misc/HazelnutFrontView.jpg)
-
Gordon if the bow is a straight bow with no deflex or reflex and the finished profile is within 1" of the strting profile I have 13.9 oz, I would usually tweak that down to about 13 oz. Steve
-
Steve, the bows holds about 1" of reflex at rest and is straight right after shooting. And the reflex was induced. Does that change your weight calculation?
-
Thats pretty good, perfect would be the same before and after shooting but seldom do any of us see perfect. That would stay about the same maybe 13.5 after tweaking. Looks like you refined the tips and such as I would have. 14.3 would be conservative.
-
one more question, how much reflex did it have when glued up? Steve
-
Steve, it's a self-bow. The stave started with about 1" of deflex. I heated in 3" of reflex before tillering and lost most of it.
-
I figred it as a backed bow, I would have built it at about 16.5 with all that reflex. Steve
-
The bow weights 11.7 oz. Maybe I underbuilt it?
-
One other thing to note. It was made from a 2" sapling so has a relatively high crown. I don't know if that makes any difference?
-
One thing that I have found is that when you are doing bows for people with small hands you often loose a little bit more weight in the handle. Womens bows with rigid handles can easily weigh 1-2 oz less just in handle weight.
-
Thats not bad Gordon, heat treating takes off some weight also. I would say you slightly underbuit it. One thing I have found if a bow is comming in lighter than I expect is sometimes the moisture is on the low side. A 6% moisture bow will come in lighter and not take set than an 8% moisture bow. I have a couple of light bows I checked and they are a bit lighter also. You may have a small handle which you have to judge yourself that might be worth an ounce or so. Handles are one of the things the bowyer has to take into account, it is based on a 4" by 1 1/2 handle roughly. Once I start tweaking I try to get the mass as low as I can without changing the tiler.
-
Good point about the sapling, glad you brought that up. After the paper was turned in I checked out some bows with higher crowns and found it is similar to trapping, most woods are stronger in tension than compression and the crown compensates for that a bit lowering the mass some. I was going to discuss that with one of the gentleman here who has a sapling he wants to do a buildalong with. Steve
-
Steve, the belly was tempered during the floor tillering stage and then tempered lightly again after the first bracing. The handle is 1.5" in depth, but hazelnut is quite light relative to most of the woods I use (with the exception of yew) so the handle is probably somewhat lighter than most.
A very interesting post. Thank you.
-
IMHO heat tempering would not change the mass much. I'm just guessing here, but it might temporarily make the bow lighter by drying it out too much.
-
Not much you can really do with a sapling bow besides get them as wide as you can and see what you can get out of them. If you go to wide the outside wood is so thin it really isn't doing any work, just adding mass.
SCP, heat treating hardens up the belly and will allow you to go with less mass than a non heat treated bow. It doesn't really change the mass of the wood than much but it does change how much wood you need. Steve
-
Not much you can really do with a sapling bow besides get them as wide as you can and see what you can get out of them.
Agreed. I used to make my sapling bows wider, but after a while I began to question whether such width yielded much benefit given a high crown. Now I make the limbs narrower and temper the belly in an attempt to compensate for the loss of compression area. It seems to work okay.
-
SCP, heat treating hardens up the belly and will allow you to go with less mass than a non heat treated bow. It doesn't really change the mass of the wood than much but it does change how much wood you need. Steve
Fascinating. Does that mean heat treatment defeats the mass principle?
-
Steve, I always thought that heat treating really did nothing more than shrinking and sealing the wood cells. Like when you see skin that has been burned, drawing it in creating really, scar tissue, that makes the belly tighter and dense. Also cutting down on moisture absorbing ducts to the inner wood?
-
No, SCP, it means a bowyer has to know what he is doing and allow for various things. Lots of things change projected bow mass, trapping, backing a bow, heat treating a bow, excessive dryness in a bow. It is not designed for idiots, more for advanced bowyers. Steve
-
No, SCP, it means a bowyer has to know what he is doing and allow for various things. Lots of things change projected bow mass, trapping, backing a bow, heat treating a bow, excessive dryness in a bow. It is not designed for idiots, more for advanced bowyers. Steve
I'm afraid you are not thinking clearly here. If you can reduce the mass required by the WOOD mass principle through heat treatment, that means the principle is no longer applicable.
Let's look at the nature of heat treatment. If it somehow changes light wood into heavy wood, the WOOD mass principle should hold even after the heat treatment. That is, still same mass is required.
If it somehow changes wood into something other than wood, say fiberglass, we don't expect the WOOD mass principle to be valid anymore. You appear to be thinking this is the case. That means we cannot use the same mass principle for the heat treated wood bows, just as we cannot do so with fiberglass bows. Of course, each different materials will have their own mass principles, so long as they are cohesive enough.
Now, what is the nature of heat treatment? Does it change light wood into heavy wood? Or, does it change wood into something else?
-
None of the above, it changes the typical ratios of compression to tension strength, allowing for a lower mass bow. Please read the chapter you questions are all answered there. I don't think you have enough knowledge here to carry on a conversation on the topic. Steve
-
None of the above, it changes the typical ratios of compression to tension strength, allowing for a lower mass bow.
I don't think you understood what I said. If heat treatment "changes the typical ratios of compression to tension strength, allowing for a lower mass bow" does that mean heat treatment renders the mass principle useless?
-
scp,
I'm not sure why, but heat treating (when proprely done) makes the belly wood more resistant to compression. I even use it to tweak a tiller when I don't want to remove wood. For instance, I will sometimes lightly temper the outer limbs when I want them to bend slightly less. You have to be careful, however, because too much can throw the whole tiller out of wack.
I'm no expert on Steve's mass theory, but I expect that you have to account for this effect like you would with any other model.
-
I answered that, You make an adjustment for that the same way you make adjustments for many other factors. Thats where experience come in. If you are too lazy t read a chapter I don't really want to deal with you anymore, it is getting rediculous here. Steve
-
scp, I'm not sure why, but heat treating (when proprely done) makes the belly wood more resistant to compression. I even use it to tweak a tiller when I don't want to remove wood. For instance, I will sometimes lightly temper the outer limbs when I want them to bend slightly less. You have to be careful, however, because too much can throw the whole tiller out of wack.
You can think of it as scraping out a certain amount of wood and replacing it with the same mass of OTHER MATERIAL, say bamboo, horn or even fiberglass. For the belly, that other material better be something that has more resistance to compression. You are basically turning your bow wood into something better than it was. It is possible that, as Badger says, heat treatment "changes the typical ratios of compression to tension strength."
Whether it can do so enough to become an exception to the WOOD mass principle is another story.
-
Steve, Am I in the ball park with my question above, or mistaken? I've never used your theory till I'm about 98% finished with a bow. If it is a high performer, just for the hell of it I have weighed it. Most of the time it is close or a little over. And then I have removed some wood after taking a closer look.
-
You can think of it as scraping out a certain amount of wood and replacing it with the same mass of OTHER MATERIAL, say bamboo, horn or even fiberglass. For the belly, that other material better be something that has more resistance to compression.
I agree with that characterization. I just don't understand what sort of changes to the wood cells are causing this to happen.
-
I answered that, You make an adjustment for that the same way you make adjustments for many other factors. Thats where experience come in. If you are too lazy t read a chapter I don't really want to deal with you anymore, it is getting rediculous here. Steve
Honestly Steve I don't know why you engaged with this guy for this long in the first place. He is just looking for someone to argue with but has little to no base of information or experience to argue with
-
Gotta love a lawyer. Try to make right things wrong and wrong things right. ::)
It should be pretty clear that even with heat treating you're just turning wood into slightly better wood. Better wood needs less mass to reach a goal.
You could just rename your heat treated wood.
I would think you would find that heat treated HHB equals Osage and Elm equals yew in regards to mass requirement.
No need to dance around and try to get a guilty verdict as you appear to be doing here.
-
I was trying to wear him out, LOL, he won! Going to start a new thread just more on a personnal note about the mass theory. Try to explain what was behind it, the motivation etc,
-
Pat, I forgot he was a lawyer, ::) I was wondering why this was getting monotonous, and we had to read through so much organic matter.
-
It should be pretty clear that even with heat treating you're just turning wood into slightly better wood. Better wood needs less mass to reach a goal.
Badger said NO to the first sentence. See, above.
As for the second sentence, Badger said, the mass principle assumes for bow making purposes all wood is equal.
-
Yea, you win, NEXT CASE, YOUR HONOR.
-
I guess Badger has his work cut out to teach the mass principle here. Good luck.
-
Badger also said we assume it is all equal even though we know it is not. This is your first indication allowances will be used by the bowyer. Quit playing lawyer! steve
-
Badger also said we assume it is all equal even though we know it is not. This is your first indication allowances will be used by the bowyer.
Of course we all know it's not the case, but let's just pretend that we all already know what the mass principle is, shall we?
-
scp, the base assumption of Steve's theory is that all wood is equal. However, Steve acknowledges that heat treating changes that calculation and that an allowance has to be made. No model can perfectly predict an outcome for something that has as many variables as constructing a bow made of all natural materials. But is seems to be a pretty good approximation and a useful tool for any bowyer who is serious about the performance of their bows.
-
scp, you've got several world class bowyers on this site. You've got members who have authored articles for archery publications. You've got a couple of world class flight shooters. I wish I had this site when I started breakin' and makin' 20 years ago. I humbly suggest you spend more time picking brains rather than nitpicking. :) Jawge
-
scp, the base assumption of Steve's theory is that all wood is equal. However, Steve acknowledges that heat treating changes that calculation and that an allowance has to be made. No model can perfectly predict an outcome for something that has as many variables as constructing a bow made of all natural materials. But is seems to be a pretty good approximation and a useful tool for any bowyer who is serious about the performance of their bows.
I believe it works. If not, we can always make it work! But we can't do that if we are not willing to think, ask questions, experiment, and communicate. I mostly ask questions.
-
Jawge, what makes you think I am not doing exactly what you want me to do? Knowledge mining is never easy and often extremely irritating.
-
........WHOLLY-WHAH............
Man............I can't beleive that this went on this Long..........and that I stayed out of it too......... ;D....I am impressed.......... ;)
-
This is nothing. Just wait until Badger starts to teach the mass principle to all people here.
-
He already did. We were advanced students though.
-
I think he did already, way back on page one?? Or in TBB4... ;)
And by the way Steve, really liked that chapter in the book. A great real world application of engineering for fine tuning bows.
-
Frankly I don't think that many people here understand the principle. Some just use it; most don't even use it, but at best make Badger apply it for them. All I'm trying to do is to make it understandable to dummies.
-
I think Steve is starting to feel the same way.
-
PatM, do you believe that Badger thinks he already fully comprehends all the ramifications of the mass principle?
-
scp... question for yah? How many bows have you made? You argue like you're an advanced and expert bowyer. What level of experience do you actually possess?
-
Will somebody PLEASE get the electric tennis racket? It's hard to sleep in this tent with that mosquito buzzing around. ;D
-
Not at all and he has admitted as much and on many occasions mentioned his pursuit of greater understanding.
-
It would be extremely difficult to incorporate the heat treatment into the mass principle, mainly because it does not work the same way for all kinds of wood.
-
scp... I asked you a question. I'm not being sarcastic. I'm genuinely interested.
-
scp... question for yah? How many bows have you made? You argue like you're an advanced and expert bowyer. What level of experience do you actually possess?
I majored in the philosophy of science several decades ago. I made several dozen selfbows and several of them are as shootable as the two cheap fiberglass bows I have.
-
Pretty vague answer.
Why don't you show us some of your work?
-
You're trying to make it pure Science. A bowyer knows it's a blend of Art and Science unless you're working with actionwood and Glass/Carbon.
Of course it works differently with various woods but you can still group them closely based on how they react.
I'm surprised you take such umbrage to Steve presenting this theory and with your background wanting a single verdict. After all OJ was guilty, not guilty and innocent all at the same time. Does Philosophy explain that?
-
Pretty vague answer.
Why don't you show us some of your work?
You don't have to trust me. Have you at least read the whole thread?
-
PatM, I already said twice in this thread that bow making is an art, not science. All I'm trying to do here is to make all the implicit assumptions of the mass principle explicit. I even suggested a way to expand the principle by using the knowledge where energy is stored in a bow limb. But for whatever reason, many people here think I am attacking the principle. Go figure.
-
It isn't just art. However the art side of it is the very reason it can't be expressed explicitly because there is always a factor that has the potential to throw it off a bit. Moisture content, local environment etc.
-
Pretty vague answer.
Why don't you show us some of your work?
You don't have to trust me. Have you at least read the whole thread?
You expect him to read all your ramblings when you wont read the section of the book that you have rambled on about. The book at least made sense. As for teaching, Badger was walking us through this before you even saw it in the book. A lot of us have a decent grasp of the principle, and understand what it was intended to do. It was not intended to plug into a computer and let lasers cut out the bow. It still requires a bowyer or at least a bow maker with a little common sense.
-
Justin Snyder, if he wants to comment on the issue, he better be willing to read the whole thread. If he just wanna express his gut feelings, he can do that without doing so, I guess.
-
Is anyone going to address the issue of how to incorporate heat treatment into the mass principle? How about you, Marc?
-
I think the mass principle is intended for practical use by bowyers. To get much more precise and exact would require impractical measurements, like cutting off the tips of your bow to see how much mass they have. The mass principle allows you to make an excellent bow just by monitoring the total mass of the bow and by taking other easy measurements like length of bending limbs, etc. You might say it's "low resolution", where a high resolution method would involve chopping the bow into inch long pieces to see exactly where the mass is placed, the obvious problem being reassembly. At least that's what I think you're getting at when you mention "where energy is stored in the bow limb".
As far as underlying assumptions, I think it is that a bow's ability to perform work is fundamentally dependent upon how massive it is. The "mass principle" is more of an empirical determination of what the ideal mass is for a given amount of stored energy from a bow made of an "average" wood. The big revelation was that the ideal mass didn't change much from one wood to another, that you could basically use the same mass for a bow made from any wood. But there small discrepancies for certain woods, and for things like cross-section, reflex, and heat-treating and so it gets fudged up or down. It sounds like you want a fully fleshed out theorem that deals precisely with all of these factors. But that starts to get extremely complicated so fast...and even if you were ambitious enough to try, the average bowyer wouldn't be able to measure enough dimensions accurately enough for it be practical to actually implement.
The whole discussion reminded me of the ideal gas law (PV=nRT, iirc) from chemistry. It relates pressure volume and temperature for gases. It is based upon an ideal gas, which doesn't exist, under an abstract set of conditions called standard temperature and pressure, which probably only occur in a laboratory. But it is applied everyday for non-ideal (i.e. real) gases in all sorts of different conditions nowhere near the standard. It is close enough, and I think the mass principle is similar for wooden bow.
So if you ever get bored you can go to the chemistry boards and question their "implicit assumptions" ;D
-
Scp, I'm just a redneck off a dirt farm in the mountains, and I'm as dumb as a sack full of rocks; but after reading Steve's chapter about the mass principal, I can understand it enough to apply it to what little I already know and make better bows as a result. I'll never be able to make bows like Steve, Marc, or some of the other bowyers here, but if I listen to them instead of argue with them, I learn, and can see results of that in my own work. One thing I have learned from hanging around here for years, also, is something that you don't seem to have grasped yet-let's call it the "wooden bow principal." In it's simplest form, it states that each piece of wood is a unique entity. Coming from a living tree, it has its own unique character and characteristics, unlike a sample of fiberglass or carbon fiber, which is pretty much standardized and consistant with any other sample manufactured to the same specifications. Therein lies the interest, challenge, and joy of building wooden bows. If you want a set formula that will allow you to build a completely predictable bow to pre-set measurements every time, get you some fiberglass lams and a calculator. Maybe building wooden bows isn't your thing. If you want to experience the challenge of working with the individual personality of the piece of wood you're working on at the moment; and try to get the best bow from it you can, then you have to accept this fact: wood isn't wood isn't wood. Steve's mass principal, when combined with a certain amount of experience and a desire to learn from and listen to the wood, is a very useful tool for making a better bow. It is not a machine that works by itself, it still requires a bowyer to operate it. Start with the ideal design for your wood, then work with it within the limitations of your particular piece of wood. There may be a knot here, a place there where a woodpecker pecked the wood, the grain may swirl, there may be a spot where the growth rings crown up or dish in. These anomalies can't be answered by mathematics, only by experience, feel, and attention. This is the very thing that attracts many of us to building wooden bows-the challenge of making them, the process of learning to read and feel wood, and the uniqueness of the finished product. This is the very thing you seem to not want to accept. It's a simple concept. It's not all quantifiable or measureable, there are too many variables. But-it can be predicted to a certain extent, which is what Steve's principlal does as well as any other method could. The rest relies on your skill as a bowyer, there's no way to get around that. Steve's theory seems sound to me, and seems simple to understand if you've built some bows. After the dozens you say you've built, you should already understand this and accept it instead of try to argue about it. I'm not very scientific at alll when I make a bow. Like Eddie, I have never weighed a bow while I was making it-but the better performing ones I have made, when weighed tend to agree in mass with Steve's ideas.