Primitive Archer
Main Discussion Area => Bows => Topic started by: arachnid on March 13, 2015, 12:07:45 pm
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So I`ve been wondering about this for quite some time- Does the wood type used effect preofmance?
I`ll explain:
If we take 2 bows made by the same bowyer and have the same design (of course, the dimentions suit each wood type) each made from a different kind
of wood, will there be a difference in preformence?
The point is- Is it REALLY worth the extra time and effort to make, say, a BBI then just a simple, say, white oak or hickory board/stave bow?
I don`t consider in this question any other espect besides preformence (like looks, ease of construction, cost etc...)
Dor
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There are many factors that affect performance and wood can sometimes be one of them even within the same species.
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Go make a willow bow, then a Osage, and let us know. :)
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I don't think you can compare selfbows with backed bows or tri-lam bows.
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I don't own a chronograph, so its all relative to me. I just build what catches my eye and try to make each bow the best it can be no matter its content.
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Samo, samo, Pearlie! ;)
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I go by what I have the highest success ratio with, bows that take the least amount of set etc. You won't find a huge difference in most bow woods but you will find a differnce. My experience seems to go along with most others. Osage, yew, elm, ipe, hickory and a few others that might not be so readily available all seem to have high success ratios and perform well.
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yes,, :)
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I don't think you can compare selfbows with backed bows or tri-lam bows.
1) Why not? Will a backed bow out-preforme a selfbow?
2) Let`s take 2 selfbows for example- hickory and osage. All being equal, which will preforme better, and why?
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A backed bow can outperform a selfbow if the profile is manipulated in the glue-up.
Flight records suggest Hickory and Osage would be equal performers if the Hickory is at optimum moisture content.
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A backed bow can outperform a selfbow if the profile is manipulated in the glue-up.
Do you mean like adding reflex?
If so, that`s not what I asked, I ment 2 bows with the same profile.
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The potential is likely greater in a backed bow because you can use materials with better balanced properties for the back or belly and likely have better energy storage per mass.
Most good bow woods however are very good at playing both roles though.
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Backed bow with the same profile will usually outperform selfbows by about 8 fps. That is a lot. But not always. Occassionaly you will get a self bow that will keep right up with them but not often has been my experience.
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The potential is likely greater in a backed bow because you can use materials with better balanced properties for the back or belly and likely have better energy storage per mass.
Most good bow woods however are very good at playing both roles though.
Sooooo, if you were to build an osage backed osage with an osage core flatbow and built an osage selfbow to match it, which one would perform better? I have always been under the impression that any time you have a glue line, its stronger than the wood itself therefore you can build a lighter limb.
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I used to make a lot of maple backed maples. They would outperform the maple self bows. I think a single glue line or even two glue lines will optimise the bow. According to Perry reflex theory a single glue line is optimum, I see no difference in that and other glue ups using more than one glue line. I think the wood is just in better condition when you start bending the bow.
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Badger-
I did not understand your last post too well.
In the case of a maple backed maple, are you saying that it is better than a self maple because two pieces glued together somehow average out the weaknesses in a single piece?
Doesn't the performance gain come from prestressing the lamination before and into the glue-up?
Willie
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Willie, I honestly don't know whay it works but there is definite benefits to at least one glueline. I am just guessing that gluing thin woods into shape damages the wood less or holds up better than shaping a self bow with heat or steam. I really don't know for sure why.
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Arachnid,
I have made both kinds that you mention in your original post, so I have no dog in the fight. It seems to me that everyone is overlooking the obvious. What I mean is either type of bow or wood used can make screamers as well as dogs.
Learning to optimize what you have available is the key to good bows. If you have good wood learn to make self bows, if the wood is marginal learn to make laminates (sinew backed, sinew backed horn bellied, wood laminates, etc), if you want absolute speed and distance make 'em out of other materials all together. I think you would be surprised just how efficient of a bow can be made by someone who has worked with available material (or combination of materials) until they have mastered the type that fits the material they have.
No type of wood or style of bow will survive bad bowyering.
Just one guys opinion however.
rich
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Arachnid,
as I see it:
The type and species of wood you work can have a tremendous influence on performance of a certain bow design. The point that Tim Baker’s been making during many of his writings, however, is that you can make a good bow out of nearly every wood, if you take its particular properties into account (mostly density or specific gravity) to adjust the bow design to the wood.
Many people say that the differences within species are more important than among species, but I don’t buy that. A lot of this can be attributed to misinterpreting extreme values for actual variance among wood samples. It may be that you find crack willow with a SG of 0.70, but that will be extremely rare. 95% of crack willow will have a SG between 0.30 and 0.40. So the important differences among wood species stand for the majority of wood samples.
As a matter of fact, I performed an earlier an analysis on bow wood properties, which is independent of specific gravity. So if your sample of wood X has a low or a high SG is entirely irrelevant to the results shown there.
http://www.primitivearcher.com/smf/index.php/topic,50571.msg692410.html#msg692410
If you take the figure for (relative) back elongation (http://www.primitivearcher.com/smf/index.php?action=dlattach;topic=50571.0;attach=109230;image), you will see that some species withstand much more back elongation than others (how far you can bend it for a certain thickness). At the same time, those which tolerate less back elongation need more force to elongate that back. And both even out to a certain degree (samples parallel to the shown regression line can store about the same amount of energy at maximum strain), but that doesn’t mean you can just interchange woods for a particular design. For a same front shape, osage and yew can be made thicker and narrower than norway spruce or paper birch, as they can withstand much more back elongation.
Woods with low SG need wider limbs to yield the same mass of the working limb, hence energy storage capacity, and therefore draw weight.
In the graph I made, the more you go right, the longer or thinner the bow should be made (both are completely interchangeable: make a bow 2 times longer, it will have eight times the draw weight. Make it two times thicker, it will also have eight times the draw weight). But at the end of the day, most woods can be utilized to yield bows shooting 170 fps at 10 gpp. TBB4 is loaded with such examples. But don’t go taking a short osage recurve and try to fit a silver birch into that exact design (length, width, taper, thickness, etc.), cos it will break. Likewise, a design optimized for a silver birch will yield a sluggish bow if made out of osage.
As for adding a backing: take the same figure and take two extremely different backing materials: sinew will be way (really way) outside the figure on the top left (allowing extreme elongation; its value is c. 5.5 for relative stiffness, and 5% for elongation), flax or hemp will be on the top right (being very stiff; c. 38 for relative stiffness, and 1.8% for elongation). They have much better properties than wood for bows but from a very different perspective, both tweaking bow performance in a different way. Glass fibre, moreover, takes the best of both of them (c 28 for relative stiffness, and 4.9% for elongation). So it’s logic that backed bows should be able to outperform non-backed bows to some degree, and that best fiberglass bows should outshoot the best wood bows.
Still, there are numbers of unbacked bows that outperform backed bows, and lots of wood bows that outshoot fiberglass bows. Why? Because the particular bow design fitted the used materials better to optimize performance.
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Willie, I honestly don't know whay it works but there is definite benefits to at least one glueline. I am just guessing that gluing thin woods into shape damages the wood less or holds up better than shaping a self bow with heat or steam. I really don't know for sure why.
Badger, straight limbed, or glued in reflex?
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Good question, I havent done any backed straight limbed.
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Arachnid,
I have made both kinds that you mention in your original post, so I have no dog in the fight. It seems to me that everyone is overlooking the obvious. What I mean is either type of bow or wood used can make screamers as well as dogs.
Learning to optimize what you have available is the key to good bows. If you have good wood learn to make self bows, if the wood is marginal learn to make laminates (sinew backed, sinew backed horn bellied, wood laminates, etc), if you want absolute speed and distance make 'em out of other materials all together. I think you would be surprised just how efficient of a bow can be made by someone who has worked with available material (or combination of materials) until they have mastered the type that fits the material they have.
No type of wood or style of bow will survive bad bowyering.
Just one guys opinion however.
rich
I never talked about bad bowyering (not that I consider myself a good bowyer...). It`s just a question I asked myself and wanted to hear the experienced guys` opinion.
Badger,
Does the "one glue line" (so called) rule applys to a straight pyramid bow (no reflex)? I have 2 white oak boards. Will gluing them together and then make a straight bow result in a better preforming bow the just a single board?
And another question to you all,
Since I only use my bow for stomp and target shooting, accuracy is the most imortant factor for me.
What are the best designs (in genral, of course) for an accurate bow (besides center-shot)? (and yes, I know good form and tuned arrows are critical, but I want to optimize all my equipment).
Dor
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A recurve like a glass bow would be my pick....ther's a reason they made them that way. :)
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Joachim, that is some great info! Thanks.
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joachim +1
Did you also measure the properties of bamboo as a backing??
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Joachim, I read your post (data crunching) and didn`t understand how to read the diagrams.
Can you explain plz?
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Meh....the greatest factor is the dude holding the tools. :-X
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Joachim, I read your post (data crunching) and didn`t understand how to read the diagrams.
Can you explain plz?
The more left on the graph, the less force is required to bend.
The more up the further you can bend it without breaking.
As far as wood is concerned it seems you cannot have both, but some are still better for both properties than other.
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Meh....the greatest factor is the dude holding the tools. :-X
+1000 :)
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Crooket arrow told me there a bow in just about any piece of wood. If you want to take the time to let it out. I've found out that's very true.
A lot of hard wood and white woods makes a bow. But hands down on the east coast it's OSAGE. You can mess and mess up and you'll still get a bow from it.
On west coast it's yew all the way.
My 3 favorite woods.
OSAGE
HICKORY
YEW
I put YEW last because I've only made 6 yew bows. The other 2 are at my finger tips.
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If all you build are hunting bows then you most likely wouldn't notice any difference. It's when you start building for performance that you start to see differences and when you see differences within species.
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As stated. The bowyer holding the tools seems to make part of the difference, while the wood I would assume also makes a difference. If one were to take one design for two different woods there is a possibility that 2 shooters could be made. But that isn't always true. Take Osage vs. Juniper. One would work as a longbow style, while the other more than likely wouldn't. While a short backed style would work with both. I guess my way is to try, if it works try again and see if it was pure luck. Not every chunk of wood is the same.
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Something I have noticed is that on the occassional self bow that does keep up with the laminates in every case I can think of it didn't take any appreciable set.
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I feel like heat treating might help even the playing field between a selfie and a perry reflexed laminate.
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Heat treating has certainly narrowed the gap between the two. If you look at published performance levels in TB1 before heat treating had become popular they were markedly lower than they are now.
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Do I think it is worth the time and effort to make a wood backed bow? :)
I guess I don't. No interest anyway.
I've made hundreds of bows and not one wood backed bow.
I just love making selfbows. I seem to favor osage and hickory these days.
But I've made bows black locust, osage, yew, maple, red and white oak, hornbeam, hophornbeam, elm, Aus. pine, ash, lemonwood, most of the hickories and probably some others I can't remember.
Arachnid, you'll find your niche.
Jawge
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I prefer self bows also George. A backed bow is considerably easier to make than a self bow once you get the process down. I guess a board bow would be the easier. I find self bows more satifying to work on.
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Yes, Badger, board bows are easy provided the bowyer chooses a board with straight grain. :)
I guess I lean more to the primitive side of bowyering. I've never seen a Native American wood backed bow which is why I've shied away from them.
I wish I kept records.
Arachnid, think about keeping records.
Jawge
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joachimM - Right on.
Learn the properties of your materials. Go and build a bridge out of wood then go build one out of steel....they can both do the job but they would look very different if built to carry the same load.
Without knowing the properties of your materials you are just guessing. Guessing can get you close but it's all in the details.
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Since my resorces are limited, I tend to relay on other people`s experience. I don`t have the time and money to
experiment too much and most of my bows comes from boards.
I`m glad this topic caused you all to spill some knolege on us mere mortals.....
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joachim +1
Did you also measure the properties of bamboo as a backing??
Just to clarify: i never measured anything, just used existing data. As for bamboo: depends so much on the species, and there are many of them. Moreover, within a bamboo shoot properties even change markedly, from less tension strong at the base to stronger near the tip.
So bamboo is difficult to pin down
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I started with laminates (about 25 bows) and found the tri-lams out performed those with the single glue line.
I have moved on to the self bows and would not go back to laminates as they are too clinical.
Osage is my #1 and yew a distant second. I am trying red elm and mulberry next, suggestions?. Also sinew backing my short ones.
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Crooket arrow told me there a bow in just about any piece of wood. If you want to take the time to let it out. I've found out that's very true.
And credit should be given where it's due: that's exactly what Steve Gardner's mass principle is all about. Look at the mass of the bow and how it's distributed, and any wood species can yield a good bow if you adjust the bow design. Thanks for one of the greatest advances in understanding bow performance.