core preformance in bows
I have been wondering how much the core effect's the preformance of the bows,by that i mean different wood for the core used for the same design. If you use different core woods and keep all the other dimentions and the design of the bow same what wood would preform better?has any one here tried this?
It is a very good question, but very difficult to answer. A definite objective test would require same-thickness laminates, tested in identical conditions. Even then, the properties of an individual wood laminates would differ greatly within the same species and a definite answer would be near impossible. I have used several species of wood in the composites and have not seen any significant difference which could be directly related to the core species. I also do not believe bamboo is any better than other woods (that is until proven otherwise).
The main thing is the workability and the grain orientation, plus of course the toughness/hardness. This means the softwoods (with the exception of yew) are not worth experimenting with. Another property may be the fatique resistance, but this again will require bench testing in controlled conditions.
Adam
The main thing is the workability and the grain orientation, plus of course the toughness/hardness. This means the softwoods (with the exception of yew) are not worth experimenting with. Another property may be the fatique resistance, but this again will require bench testing in controlled conditions.
Adam
Adam is very right.
I would add, that I prefer mountain- maple, cause it is the wood with the best glueing- capablities, it is easy to steam- bend, keeps its shape and it is light in physical weight.
Don?t forget that you can do great selfbows(flatbow- design) with it.
Michael
I would add, that I prefer mountain- maple, cause it is the wood with the best glueing- capablities, it is easy to steam- bend, keeps its shape and it is light in physical weight.
Don?t forget that you can do great selfbows(flatbow- design) with it.
Michael
I have success with Maple. Ash does work but it fells as a slower bow. Last wood I did try was Juniper. Fast bow but one limb core did crack.
I just recieved a pair of very good horns and a friend sent me some very good quatersawn red elm which i am thinking of using for sahiyas.and bamboo for core.I am thinking of getting some hard maple and using that exclusively in the future.
My question was the same:
Here is a nice table to at least compare the physical properties of the woods:
http://www.grafsnowboards.com/index.php ... ial%20data
I'm about to try beech for the core. Hard wood. Short grain. Easy to steam-bend (at least when flat).
Question will be if the core holds when stringing the bow. At least snowboards have beech cores :)
Has anybody experience with beech ?
Here is a nice table to at least compare the physical properties of the woods:
http://www.grafsnowboards.com/index.php ... ial%20data
I'm about to try beech for the core. Hard wood. Short grain. Easy to steam-bend (at least when flat).
Question will be if the core holds when stringing the bow. At least snowboards have beech cores :)
Has anybody experience with beech ?
I have try elm few times and that did not make bows.
Beech is by far not capable to withstand the tension stressing the back of the core, it is to slow too.
I?m a longboarder, my favourite is California- based ARBOR, they know how to make boards without using artificial fibres, their cores are made of mountain- maple.
Don?t use beech for any kind of bow.
Michael
I?m a longboarder, my favourite is California- based ARBOR, they know how to make boards without using artificial fibres, their cores are made of mountain- maple.
Don?t use beech for any kind of bow.
Michael
you're right beech might be too slow
as for tension maybe the backing can absorb it
concerning the boards once more - skateboards are often made of 7 layers of canadian mountain maple (yes!)
;-)
as for tension maybe the backing can absorb it
concerning the boards once more - skateboards are often made of 7 layers of canadian mountain maple (yes!)
;-)
I just started working on some bamboo for some cores and am planning to cut down a maple from the backyard as well as a branch from my red mulberry to try for cores.I tried bending some mulberry for sahiyas last week and ended up breaking them,I think my fault was that I did not soak the wood for long enough before bending it.
Is there some historic use for Chinese elm?
Beeing a scientist (sorry) I looked for scientific data:
I found this interesting article at woodweb.com
http://www.woodweb.com/knowledge_base/R ... _Wood.html
concerning the bending of wood
quote:
Stock Selection
The U.S. Forest Service has evaluated 25 hardwood species for relative bending quality. In their testing, the best 17 woods were:
Hackberry (Best)
White Oak
Red oak
Chestnut oak
Magnolia
Pecan
Black walnut
Hickory
Beech
Elm
Willow
Birch
Ash
Sweetgum
Soft maple
Yellow-poplar
Hard maple (Worst)
This ranking represents the results from one evaluation; variation in the results can be expected from tree to tree and site to site.
A further test of 20 different white oak trees showed that the specific gravity (or density) and the rate of growth had no effect on bending failure. Likewise, the amount of end pressure (in excess of that required) was not related to the number of bending failures. (In other words, a piece that is going to fail will fail even if additional end pressure is exerted.) HOWEVER, bending quality was related to certain strength-reducing defects:
- Cross-grain wood is more likely to break than straight grain. the rule of thumb is that the grain should slope no more than 1:15 along the piece. Occasionally, there can be "local cross grain" (near a knot, for example) that can result in failure. A special form of cross grain is the interlocked grain, which is especially weak.
- Knots are accompanied by distorted grain and represent weak areas.
- Shake is a separation within the wood parallel to the annual rings. This separation encourages shear failures.
- The pith (or exact center of the tree) is very weak and failures there are likely.
- Surface checks, due to improper drying conditions early in drying, are small separations in the wood. In bending, they can result in small bumps or slivers.
- Brash wood is probably found in all species and results in very short (along the grain) breaks rather than longer slivers. Wood that is exceptionally light in weight, compared to the average for the species is especially prone to brashness. Brashness can, therefore, be a natural phenomenon. On the other hand, brashness can result because of overheating wood, because of decay, or because of earlier failure. (See Chapter 64.)
- Decayed wood is weaker than normal wood, even if decay has not progressed very far.
Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison. His Book, The Wood Doctor's Rx, is available from http://www.fdmbookstore.bigstep.com/.
I found this interesting article at woodweb.com
http://www.woodweb.com/knowledge_base/R ... _Wood.html
concerning the bending of wood
quote:
Stock Selection
The U.S. Forest Service has evaluated 25 hardwood species for relative bending quality. In their testing, the best 17 woods were:
Hackberry (Best)
White Oak
Red oak
Chestnut oak
Magnolia
Pecan
Black walnut
Hickory
Beech
Elm
Willow
Birch
Ash
Sweetgum
Soft maple
Yellow-poplar
Hard maple (Worst)
This ranking represents the results from one evaluation; variation in the results can be expected from tree to tree and site to site.
A further test of 20 different white oak trees showed that the specific gravity (or density) and the rate of growth had no effect on bending failure. Likewise, the amount of end pressure (in excess of that required) was not related to the number of bending failures. (In other words, a piece that is going to fail will fail even if additional end pressure is exerted.) HOWEVER, bending quality was related to certain strength-reducing defects:
- Cross-grain wood is more likely to break than straight grain. the rule of thumb is that the grain should slope no more than 1:15 along the piece. Occasionally, there can be "local cross grain" (near a knot, for example) that can result in failure. A special form of cross grain is the interlocked grain, which is especially weak.
- Knots are accompanied by distorted grain and represent weak areas.
- Shake is a separation within the wood parallel to the annual rings. This separation encourages shear failures.
- The pith (or exact center of the tree) is very weak and failures there are likely.
- Surface checks, due to improper drying conditions early in drying, are small separations in the wood. In bending, they can result in small bumps or slivers.
- Brash wood is probably found in all species and results in very short (along the grain) breaks rather than longer slivers. Wood that is exceptionally light in weight, compared to the average for the species is especially prone to brashness. Brashness can, therefore, be a natural phenomenon. On the other hand, brashness can result because of overheating wood, because of decay, or because of earlier failure. (See Chapter 64.)
- Decayed wood is weaker than normal wood, even if decay has not progressed very far.
Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison. His Book, The Wood Doctor's Rx, is available from http://www.fdmbookstore.bigstep.com/.
Uli; I would assume from the list that bending quality refers to the ability of wood to take a bend, permanently.
This is not necessarily a good quality for bow wood.
This is not necessarily a good quality for bow wood.
That?s it Jack.
Always the same story: scientists are no craftsmen, maybe some of them.
I remember a wood- engineer took part in one of my bow- classes, he knows everything about wood, but was absolutely uncapable of working the growthring at the back of a selfbow with the drawknife( he was asking for a machine to do this?).
F.e. no bowyer would make a bow of white oak.
F.e. what?s about yew, osage, black locust, hawthorn, euonymus, blackthorn, theyall are outstanding bow- woods, but to delicious for the nowadays wood- working industry.
I?m a trained cabinetmaker, but my lessons didn?t tell me too much about the needs and capablities of a bowyer.
A bowyer has a very different look at wood than a nowadays cabinetmaker, carpenter or wood- engineer.
I think, for a self- bowyer the much more determing capablity of a wood is not its bending- capablity, but its springiness.
A hornbowyer is looking for a light wood with quite good bending capablities, but with outstanding glueing capablities.
Michael
Always the same story: scientists are no craftsmen, maybe some of them.
I remember a wood- engineer took part in one of my bow- classes, he knows everything about wood, but was absolutely uncapable of working the growthring at the back of a selfbow with the drawknife( he was asking for a machine to do this?).
F.e. no bowyer would make a bow of white oak.
F.e. what?s about yew, osage, black locust, hawthorn, euonymus, blackthorn, theyall are outstanding bow- woods, but to delicious for the nowadays wood- working industry.
I?m a trained cabinetmaker, but my lessons didn?t tell me too much about the needs and capablities of a bowyer.
A bowyer has a very different look at wood than a nowadays cabinetmaker, carpenter or wood- engineer.
I think, for a self- bowyer the much more determing capablity of a wood is not its bending- capablity, but its springiness.
A hornbowyer is looking for a light wood with quite good bending capablities, but with outstanding glueing capablities.
Michael
Right the article mentioned above only refers to plastic (steam)bending of wood and the relationship to elastic bending quality is not examinded.
Unfortunately I could find no useful data about the elastic bending range (at least in the internet). One would need to compare the complete stress-bending curves, for example to some appreciated bow-wood.
;-)
Unfortunately I could find no useful data about the elastic bending range (at least in the internet). One would need to compare the complete stress-bending curves, for example to some appreciated bow-wood.
;-)
Uli , can you explain me, why every novice try working vith bad material ? all information about material are here in Atarnet, Adams book etc. Our grand , grand fathers was not idiots . 1000 years hard working and opinion. Dont good for you ? :roll:
My wish would be that someone could identify (Latin names) the five recommended Chinese bow woods that Stephen has mentioned previously several times.
Because all do not live in the same environment as they did. So we have to spend 1000 year to find out what wood will work :)Dusan wrote:
Uli , can you explain me, why every novice try working vith bad material ? all information about material are here in Atarnet, Adams book etc. Our grand , grand fathers was not idiots . 1000 years hard working and opinion. Dont good for you ? :roll:
bamboo, maple, birch, mulberry,ash,robinia... can find everyvhere. But good quality - grain- this is problem.
hey guys
I appreciate your advises about wood
of course I will use traditional wood
but dont want to waste a lot of good wood for a light bow at the beginning
;-) Uli
I appreciate your advises about wood
of course I will use traditional wood
but dont want to waste a lot of good wood for a light bow at the beginning
;-) Uli
:shock: :roll:
:shock:Uli wrote:
hey guys
I appreciate your advises about wood
of course I will use traditional wood
but dont want to waste a lot of good wood for a light bow at the beginning
;-) Uli
Uli, you live in the Black Forest so that you should have no problem at all to find the wood Dusan recommended before: maple, ash and black locust are available very very easy were you live and they should be fairly cheap too.
And timber recommended by redhawk (hawthorn, euonymus, blackthorn) should be easily available too: you just have to look for it by yourself as they are not commercially sold.
you're right i ll check the local stores :)
or cut down the black forest :twisted:
anyways I was really amazed how much a stable backing can change the properties of wood !
the pics here show a friend doing the "stress - and - relax - test"
with a simple piece of beech prepared by me:
steam-bent, 0.5cm thick
backed with one layer (~1mm) of fiberglass and polyurethane glue (from a car repair set)
with scrapings for the glue on the back
or cut down the black forest :twisted:
anyways I was really amazed how much a stable backing can change the properties of wood !
the pics here show a friend doing the "stress - and - relax - test"
with a simple piece of beech prepared by me:
steam-bent, 0.5cm thick
backed with one layer (~1mm) of fiberglass and polyurethane glue (from a car repair set)
with scrapings for the glue on the back
Uli; Have you heard the expression, "You cannot make a silk purse from sow's ear." ?
I would not want to discourage anyone but it will be very difficult to research Asian traditional archery using non bow wood species and fiberglass and polyurethane.
Now back to the topic. Redhawk has pm ed me that one of the preferred Chinese species is Tamarisk. This took the word right out of my mouth as I have heard that some bows of the Xinjiang desert had Tamarisk cores.
A little research has demonstrated that it also is a family with many varieties. Has anyone tried this wood? It is available in the USA and is considered a nuisance introduced species. Entertaining how many Chinese tree species fall into this category. -j-
I would not want to discourage anyone but it will be very difficult to research Asian traditional archery using non bow wood species and fiberglass and polyurethane.
Now back to the topic. Redhawk has pm ed me that one of the preferred Chinese species is Tamarisk. This took the word right out of my mouth as I have heard that some bows of the Xinjiang desert had Tamarisk cores.
A little research has demonstrated that it also is a family with many varieties. Has anyone tried this wood? It is available in the USA and is considered a nuisance introduced species. Entertaining how many Chinese tree species fall into this category. -j-
never ending story...
:D
dont worry I am getting REAL bow wood and glue
but all this takes a long time
just could not believe the mechanics of a strongly reflexed piece of wood (I have shot only some modern mongolian hornbows yet) and had to make the "experiment"
Cheers, Uli
dont worry I am getting REAL bow wood and glue
but all this takes a long time
just could not believe the mechanics of a strongly reflexed piece of wood (I have shot only some modern mongolian hornbows yet) and had to make the "experiment"
Cheers, Uli
Jack,
To answer your question partly, Chinese elm was often used for bow-ears. It says so in the regulations, and I have a large bow with elm ears to confirm that they indeed followed these regulations.
More expensive bows would have mulberry, birch or acacia ears. I just worked on some acacia ears of Qing bow reproductions, and it really is good stuff to make these ears out of: rather hard and with dense grain but still relatively light. It is a pleasure to work them with a traditional "centipede scraper", a tool with a number of razor sharp blades scraping at 90 degrees.
As for the core, mulberry was used on the better ones. I would have to check what the regulations say about core-wood for common bows.
For some reason bamboo was not considered a preferred wood for the cores, although it was used. I don't know whether this was related to its properties or its symbolical meaning. The early Manchus may not have had much bamboo available to them, and may have carried on the tradition of using materials used by their ancestors.
Mulberry, in contrast, was noted as a bow-making material in present-day Manchuria since at least the Zhou dynasty where the inhabitants or this region were already hailed as expert large game-hunters and their archery equipment appreciated by the Zhou court.
-Peter
To answer your question partly, Chinese elm was often used for bow-ears. It says so in the regulations, and I have a large bow with elm ears to confirm that they indeed followed these regulations.
More expensive bows would have mulberry, birch or acacia ears. I just worked on some acacia ears of Qing bow reproductions, and it really is good stuff to make these ears out of: rather hard and with dense grain but still relatively light. It is a pleasure to work them with a traditional "centipede scraper", a tool with a number of razor sharp blades scraping at 90 degrees.
As for the core, mulberry was used on the better ones. I would have to check what the regulations say about core-wood for common bows.
For some reason bamboo was not considered a preferred wood for the cores, although it was used. I don't know whether this was related to its properties or its symbolical meaning. The early Manchus may not have had much bamboo available to them, and may have carried on the tradition of using materials used by their ancestors.
Mulberry, in contrast, was noted as a bow-making material in present-day Manchuria since at least the Zhou dynasty where the inhabitants or this region were already hailed as expert large game-hunters and their archery equipment appreciated by the Zhou court.
-Peter
I would assume MOR/MOE would be good number... or more if that is bad the wood is not good for core. 1% is good 0.7% bad
Diffuse porous is also good(Maple,hazel,birch, alder). Ring porous not so good(ash,hickory,osage ...). Then the wood should be glueable and heat bendable.
Diffuse porous is also good(Maple,hazel,birch, alder). Ring porous not so good(ash,hickory,osage ...). Then the wood should be glueable and heat bendable.
I think lighter core will add speed.
It will also make the bow typically more prone to break.
We probably agree on these.
You cannot make the analysis just making the same bow and comparing the crono results. You should also break the bows and compare how much it took.
Yet the breakage can be due to material defects or craftmanship problems, so even that may not be that good.
I was thinking of if the durability between glassfibres is the same as durability in asian composite? (sinew is bending alot unlike gf-backing, so I think this is not the same.)
It will also make the bow typically more prone to break.
We probably agree on these.
You cannot make the analysis just making the same bow and comparing the crono results. You should also break the bows and compare how much it took.
Yet the breakage can be due to material defects or craftmanship problems, so even that may not be that good.
I was thinking of if the durability between glassfibres is the same as durability in asian composite? (sinew is bending alot unlike gf-backing, so I think this is not the same.)
I think lighter core will add speed.
It will also make the bow typically more prone to break.
We probably agree on these.
You cannot make the analysis just making the same bow and comparing the crono results. You should also break the bows and compare how much it took.
Yet the breakage can be due to material defects or craftmanship problems, so even that may not be that good.
I was thinking of if the durability between glassfibres is the same as durability in asian composite? (sinew is bending alot unlike gf-backing, so I think this is not the same.)
It will also make the bow typically more prone to break.
We probably agree on these.
You cannot make the analysis just making the same bow and comparing the crono results. You should also break the bows and compare how much it took.
Yet the breakage can be due to material defects or craftmanship problems, so even that may not be that good.
I was thinking of if the durability between glassfibres is the same as durability in asian composite? (sinew is bending alot unlike gf-backing, so I think this is not the same.)
If one looks this from an engineering (materials- and structural) point of view the answer for desired properties is fairly easy and standard but tranlating those to actual species values is more difficult.
-Light weight
- elastic (returns well)
-low hysteresis or low internal losses
- required breaking and/or elastic tensile strain for surviving under the sinew
- required shear strength
The problem is that one can't find those values measured properly for most species. FPL data is mostly good but does not cover all required properties.
Besides it is not possible to find the anciently used woods everywhere so it would be good to know what to substitute. The only white mulberries that I know to grow in Helsinki are at the University's botanical garden, I don't think they would be happy if I went and cut them down.
TLM
-Light weight
- elastic (returns well)
-low hysteresis or low internal losses
- required breaking and/or elastic tensile strain for surviving under the sinew
- required shear strength
The problem is that one can't find those values measured properly for most species. FPL data is mostly good but does not cover all required properties.
Besides it is not possible to find the anciently used woods everywhere so it would be good to know what to substitute. The only white mulberries that I know to grow in Helsinki are at the University's botanical garden, I don't think they would be happy if I went and cut them down.
TLM
Mulberry for the core? That's new for me. Here we have plenty of mullbery, It is virtualy everywhere in the rural areas. It does have straight fibres, but I have never tought of it as a good core wood.Peter Dekker wrote:
...
As for the core, mulberry was used on the better ones. I would have to check what the regulations say about core-wood for common bows.
...
-Peter
Yes. Mulberry was very popular wood core in Korea or China too. Koreans masters made some full mulberry bows vithout horn - shorter than hornbows !!! Extraordinery thing full circle reflex... :shock:
That's verry verry interesting. I'll post a new topic about mulberry core in this section of the forum in order not to spam here ! Thanks a lot !
I have a mulberry core that I am trying to get ready for a crabbow,am going to use mulberry for the ears as well,I hope it works out.
What do you think of Laburnum? I got some.
If its mine , i dont do it...I try time ago hard woods close the laburnum (yew), not very good result. low porosity dont work good vith glue. But couriosly, some turkish sources say about yew...