Primitive Archer
Main Discussion Area => Bows => Topic started by: arachnid on January 21, 2016, 12:54:22 pm
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Hi guys.
Well, it`s pretty much as the title says. How do I use bamboo as a belly?
I guess I need to flatten the inside and glue the backing , and I read that
it`s good to heat treat it, but my main questions are:
a) how do you tiller it?Do you scrape the rind? how much? what about the nodes on the belly?
b) do I need to glue it so the nodes are facing each other?
c) do I have to have a core or can I glue the back to the belly piece?
Any help will be great.
Thanks
Dor
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Hi Arachnid...First prepare the bamboo as if for a backing, around 1/8" thick....then glue on the belly instead of the back..
.I presume you will be using a core and a backing as well? ....I believe there are many ways to do this....I have made quite a few and the easiest I find is to pre taper the core and go for absolute symmetry, , then if your lucky ( or accurate) then you wont need to tiller at all. This is quite acheivable.. but difficult with first bow of this type
This is a great tip , I wish I discovered earlier. This is to use separate bamboo lams for each limb. Then cut each lam from side by side in the pole, this ensures the nodes are in exactlty the same place on each limb. which will save much bother.. the node positions are important to be balanced
then you will need to heat treat the bamboo in order to make it all worthwhile. basically slowly toast till light golden brown, slow and steady....some people toast till dark brown or black...but I personnaly dont agree ..
irrregularities in tiller can then be scraped as normal,this will not affect the belly bamboo, but is disastrous for a bamboo backing....I have tested this and done it many times, you can definnately scrape as with an other wood belly....
There is a problem though , you dont want to scape too much...the power fibres get stronger towards the outer edge , unlike wood, so ypu dont want to scrape away too much....thatis why you should , pre taper the core and go for symmetry as far as possible..Hope this helps
also in korea, where the bamboo experts live, they often adjust the tiller with gently heat and stress the limb on their knee...I have tried this with good success, just dont heat enough to melt the glue and take it easy....bamboo appears to more forgiving like this than wood,
Dave
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Thanks a ton Dave! Very helpful.
I don`t want a core and I`ve seen BBB bows without core woods.
Can you give me some dimensions for the bow? belly thickness? width?
I want a 40#@26" bow. I think I`ll try a 5 curve design or a recurve...
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I have only ever made them with a core,,,which I think is the best way, but no reason why you couldnt make one without a core,,you would just have to make the lams thicker,,,I have thought about trying this, but never done it.
I will PM you with dimensions tomorow because I have to go out tonight and dont have time to make some accurate measurements!!
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Great advice from dragonman! It is very possible. I sanded the nodes down on the belly side of my all bamboo bow, rather than scraping, but either works.
Post up some progress pics. Looking forward to seeing this bow come to life for you!
Tattoo dave
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Heat treat first! Bamboo does really well as a belly wood when it is heat treated.
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Great advice from dragonman! It is very possible. I sanded the nodes down on the belly side of my all bamboo bow, rather than scraping, but either works.
Post up some progress pics. Looking forward to seeing this bow come to life for you!
Tattoo dave
Thanks Dave.
Do you sand the nodes flat on the belly?
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if I need to I sand the nodes flat, if the bow bends well I leave them. I agree sanding may be petter than scraping it leaves a more uniform surface.
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arachnid, I sent you a PM , but then I thought I would post the info, here as well for the benefit of anyone else who is interested to make one.
...there are too many variables and possibilities to give exact dimensions, depends on what type of bow you are planning to make...straight , reflexed, recurved, how long, what width profile etc
basically though I would make your limbs 1 1/4 inches wide at the widest point and with a core wood you would be looking at something like 1/8 inch - 3/16 inch of taper over the bending section of limb..If you're having parallel width limbs over the bending section you will need more core taper than if you are using a width taper as well , as in a pyramid style design...For a 50lb bow , I usualy make the belly and back lambs 1/8 " and the core 3/16" at the widest point tapering to almost nothing where the limb stops bending....this is with a strong reflex though, without the reflex you will need less taper...
dont make the bow too long or else the bamboo will not be very efficient, it works best with shorter bows, 56" - 60" long....depending how long the handle section is
important is to stagger the nodes on the back and belly ,so the belly nodes are positioned midway between the back nodes.
hopes this helps, good luck,
also do the heat treating before glue up
Dave
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Thanks Dave.
Well, as said, I`m not going to make a core but to glue the backing on the belly boo.
So, I`ll be thankful if you`ll tell me your thoughts about these dimensions:
60" long, tip to tip (58" nock to nock). stiff hand- 4"+2" fades (8" total)
My draw is 26" and I want a 40# bow.
Recurved tips.
1 1/4" width (I hope I get the backing that wide.... when I make backing strips it usualy ends up less, about 1 1/8").
1/8" thick backing lam.
1/4" thick belly lam.
Important note- I`m not using any power tools. Flatning is done with a spokeshave. So, is it safer to use epoxy instead fo wood
glue (due to the "not 100% flat" glue surface), please let me know.
Waiting for you reply, Dave.
Thanks,
Dor
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those dimensions look ok to me....1 1/8" width is good, anwhere between 1" and 1 1/4! should work well
I only use hand tools too, I find a small sharp block plane works best on bamboo
epoxy works well too, if I,m putting in a serious reflex or recurves I always use epoxy, think it is safer, safer for poor joints too,
the depth will be an estimation , but based on mine using a core I would say that 1/8 + 1/4 of depth may be a bit under, all depends on the quality of the bamboo though, it varies in strength a lot
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I think without a core you are going to get a dog for a shooter. I wouldn't sand the nodes. You should lay out the nodes so they are in between the nodes of the bamboo on the back. If you can help it don't put a node right in the fades. Good luck
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Very good topic and great information!
How do you make bamboo heat treating? Just conventionally, with heat gun? Outer or inner side or both sides? Have you tried any kind of heat treating tube, like insulated metal pipe where you can put for example ten bamboo slats and heat treat them all at same time? I think it would be beneficial to temper them both sides. And, it would save time a lot!
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the depth will be an estimation , but based on mine using a core I would say that 1/8 + 1/4 of depth may be a bit under, all depends on the quality of the bamboo though, it varies in strength a lot
If it's a bit under, how much do you suggest? I don't know bamboo properties so I'm only guessing here.
I think without a core you are going to get a dog for a shooter.
Sorry, but I didn't get it... Is that good or bad? :-/
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A dog would be bad, a slow bow with poor cast
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Considering how dogs are fast runners, i never understood the expression.
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I agree it could be a "dog" !!, only the outer 1/8" of the bamboo has any strength , in moso bamboo anyway....some other bamboo can be considerably harder, but also harder to get hold of in good condition
if you do it without a core, I would probably make both lams 1/4" thick , but I'm only guessing....you will have to make one to find out, as an experiment
how long extra would it take to make a tapered core? maybe you'll save time in the long run .using a tried and tested design....but then you may make a good discovery....I|'d be interested to see how it comes out....keep me posted
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http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=001887;p=1
Maybe this will help you out
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I agree it could be a "dog" !!, only the outer 1/8" of the bamboo has any strength , in moso bamboo anyway....some other bamboo can be considerably harder, but also harder to get hold of in good condition
if you do it without a core, I would probably make both lams 1/4" thick , but I'm only guessing....you will have to make one to find out, as an experiment
how long extra would it take to make a tapered core? maybe you'll save time in the long run .using a tried and tested design....but then you may make a good discovery....I|'d be interested to see how it comes out....keep me posted
Well.... the resonse I`m not using a core are pretty technical.
1st of all, I don`t have access to a lot of wood type. I can get white oak, but there`s the "no straight grain" issue. I can also get ipe pretty easily, but then I`ll just make a bamboo backed ipe...AGAIN. I can also get burmeas teak (I hope I spelled it right) but I don`t know how will it perform as a core. Then there`s alot of pine, but that`s not an option.
2nd, since I don`t have power tools, I don`t know how to make a tapered lam.
If you have any solutions of ideas for these problems, I`d like to know.
I`ll also might try 1/4" backing. Might work.
Thanks.
Dor
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The grain orientation for your core is not that important. White oak or ipe would aslo make suitable cores. I have always marveled at the guys who pull off the bamboo belly bows with no tillering. I think you really have to know what you are doing or have exact demension for it to work.
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Why wont pine work as a core? I know cedar will.
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The grain orientation for your core is not that important. White oak or ipe would aslo make suitable cores. I have always marveled at the guys who pull off the bamboo belly bows with no tillering. I think you really have to know what you are doing or have exact demension for it to work.
Well, I can get bamboo poles pretty easily and it`s not very expensive, so I`m willing to try.
Will Teak work as a core?
Why wont pine work as a core? I know cedar will.
Are you talking about Western red ceder? that very light weight wood they sell at lumber yards?
I figured pine is too brittle....
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I dont knkw about western. I was refering to erc. I know JW has made a western cedar bow once ao it can be done as a bow. It may work as a core.
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ipe makes an excellent core......so does bamboo.....just make a bamboo core, you dont need power tools for this!!...just draw the taper down the edge of the lam and plane to the line
the taper of the core will control the tiller and final drawn profile, if you dont get it right first time, so long as youre paying attention you'll get pretty close the next time, then there is always 3rd time lucky.....these bows are an art that people perfect over years, unless you perfect them they dont perform much better than any other wooden bow, but they are possible to make much shorter than most wood bows....the bamboo has to work more than wood, too get the best out of it, so you want a small bending limb section
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ipe makes an excellent core......so does bamboo.....just make a bamboo core, you dont need power tools for this!!...just draw the taper down the edge of the lam and plane to the line
the taper of the core will control the tiller and final drawn profile, if you dont get it right first time, so long as youre paying attention you'll get pretty close the next time, then there is always 3rd time lucky.....these bows are an art that people perfect over years, unless you perfect them they dont perform much better than any other wooden bow, but they are possible to make much shorter than most wood bows....the bamboo has to work more than wood, too get the best out of it, so you want a small bending limb section
If I make a bamboo core, I just plan it from both sides?
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sorry. Yeah what the other guys said. I think the bow would have a slow speed (cast) without a core
You can buy them from binghams for about $20.
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yes just plane the bamboo from both sides.....if your bamboo has thick enough walls.
the best bamboo bow makers are the koreans, this is how they do it.....so I believe
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Which core will give me better cast- bamboo or ipe? Will it make such big of a difference?
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The challenge doing this by hand is getting the exact taper for both limbs. Because once you glue up the bamboo belly there is no scraping you can do on the belly. The only way to tiller is to narrow the sides on this style. That i why I use a drum sander and put the tapers in and then splice identical tapers in the center. The style James Parker taught me I use three lams that are tapered. So when you glue it up you are very close to your tiller. You still have to flex the bamboo over your knee to adjust things a bit at times.
Of course it can be done and the Japanese have done it by hand for eons. To make a really good core like a yumi from bamboo you stack it vertically and offset nodes and then cut and plane your tapers. You can also use bamboo flooring as it has offset nodes like this.
I would say Ipe would be better than just flat planning some bamboo. Be prepared to mess up a few until you get the thickness of the core right on to get your poundage. Use a micrometer and take notes of your core(s), bamboo. First one I tried got so skinny as I was trying to tiller it. Too thick on the cores.
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with respect Gaur you are wrong about sanding the bamboo belly, the nodes on the belly can be sanded down with no adverse effects , as in fact can any part of the belly. The belly lam is only being compressed and compromising the integrity of the belly fibres makes no difference to the compressive strength of the belly. I tested this to destruction on several of my first bows like this that I wasnt happy with. You can sand or scrape the belly like you would on any other wooden bow. I wouldnt say this if I hadnt tested it and wasn't completely sure.
Because of the thin layer of "power fibres" the belly responds more quickly than wood, but again all depending on bamboo quality, some bamboo has much thicker power fibres than other.....The older the bamboo the better, it hardens with age. In japan they use bamboo from younger poles on the back and from older poles on the belly. These days most commercial bamboo is harvested as soon as it reaches a good height and it isnt given the chance to mature, so older bamboo is harder to get. But you can get it and when you do it is visibly darker and clearly harder when you do a nail test on the inner fibres....considerably harder infact. this makes a big difference in performance.
In my experiments the harder the core the better, the added weight of a hard core seems negligble compared to the increase in performance....so if you only have young bamboo I would use ipe instead...the main problem with ipe is the oil in it that makes gluing procedures more critical. if you are going to use a big recurves...(.without a good reflex or recurve the bamboo isnt stressed enough to work enough to make a good bow)
\dave
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Ok dragonman if you tried it and based on your experience you can do so. For me that would defeat the whole reason to make such a bow. I still wouldn't say it would be benificial to do so and you would want to get it right in you stack
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sure- natural bamboo lams,and bamboo flooring can be used as the core,, but performance will be lost,,, maybe not a dog per say to shoot, but very noticable differences compared to to any hardwood core lams.. as far as breaking through the belly,a significant drop in poundage and cast will be apparent,,almost instantly,,, but a lot has to do with thickness of boo belly lam, how much carbonizing of belly lam, there is a large difference ,in just light heating the belly compaired to all out black full carbonizing of the lam,, also quick flash carbonizing compaired to slow heating or long time smoking of bamboo will be very different too. in my test and experience the more temper , the more wiggle room you have , if you do break through the belly,, it is still easier to Pre- factor in the tiller in the lams ,,than to scrape for a targeted poundage,, of course that just my assessment,,, I'm no pro,, i just build a bow
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I have to admit that the intact bamboo belly bows impress me more than almost anything else. I would not recomend them for new builders for sure.
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;)
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yes of course its better not to sand the belly...I dont touch the nodes or the rind unless I have to... I am saying.if it is necessary it can be carefully done..... if it means the diference between a shooting bow or one that is going in the wood burner, then scraping the belly is an option....but aim for symmetry and exact taper measured with a vernier......this was my first advice
.(.even the old japanese bowers used a basic wooden vernier to measure the taper)
James Parker has made more of these than me and knows more...I would follow his advice now he has showed up...
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I asked James how many of these style bows he has made over the years. He said according to his ledger he is at 1872 bamboo belly bows in 25 years. That's a lot of bows. :o
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yes of course its better not to sand the belly...I dont touch the nodes or the rind unless I have to... I am saying.if it is necessary it can be carefully done..... if it means the diference between a shooting bow or one that is going in the wood burner, then scraping the belly is an option....but aim for symmetry and exact taper measured with a vernier......this was my first advice
what dragonman said,, :) i agree completley
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So james the question i have is do you prefer flash carbonizing or a slower method?
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I've watched James flash temper a boo belly strip :o and it would scare the heck out of you to watch and you'd wonder how that charred belly strip could withstand the compression stresses of the bow...but it does...but also, this ain't James' first rodeo. He has probably built more bows of all styles than most of us put together. So, listen to what James says and take it as gospel.
...and actually James, you are a pro. ;)
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I'm glad this topic got alot involved. I just don't get one thing- if I'm using ipe as a core, why not make a bamboo backed ipe short bow (60", as planned with the bamboo belly)? What's the benefit in making a bamboo backed bamboo (with ipe core) bow?
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Well originally the topic WASabout how to use a boo belly not boo backed epe wasn't it😉
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Well originally the topic WASabout how to use a boo belly not boo backed epe wasn't it😉
Yeah... That right.... But I thought of making a bbb without a core. Now that I understand that without one the bow will have poor cast, I wonder why not make a BBI instead? Seem way simpler...
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It is certainly easier, but if you don't push yourself you stagnate, imo
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Cuz bamboo belly bows look cool 8) and perform great. I have one from James that has ipe as a core and two other Osage lams. Most of his designs have three lams.
But bamboo backed ipe and bamboo backed Osage are great as well.
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what is flash carbonizing? the least amount of time spent to temper a subject (bamboo belly lam), but at the same time get a thorough heating through the rind down to the near other side of the strip without total burn out or burn through or total annhialation of the lam.... whew that was a mouthfull.. anyway - it takes a lot of practice and ruination of good bamboo,, i suggest practice on scraps a lot first.. now you have to take in account the thicknesses of the boo backing strip as well as the core wood stack, if any,,, a single one pc core can be used- but with great difficulties when inducing reflex or recurve of the limbs, also, springback will be more if built on a form of any kind,, rope and wedges takes care of this problem.. target poundage is figured into the build before hand ( the stack), tillering can be achieved with and or spot limb heating or knee tillering but too much of either one can induce set in one particular area more than another,,, takes a lot of practice also.. R and D is time consnuming and expensive... try boo backed bows first ,work the bugs out ,then try adding the belly strip to an existing bow and then work the bugs out from there..
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slow heatreating bamboo belly,,, just what it says,, slower time that the boo is subjected to a heat source , soaking-- as in a bath of heat or soaking in smoke for a long period of time,, lower heat if any, or smoke only..as in a smoke house like smoking hams..if you can wait that long,, it can be better and have great effect on the belly boo , but from my findings does not get quite as hard in compression as full char carbonizing, meaning the strip is on fire , controlled burning..
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When making a bamboo CORE (cut from a pole and flattened on both sides), does it need to be heat treated too? If so, on which side (facing the belly or the back)?
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yes it is hard to get a decent recurve with a single one piece core...(.but for a first bow I would recommend starting with a one piece core then progressing from there..)
thanks James for the info on flash carbonising, very interesting, I was aware you do this.....I never had the courage to try this, it seems to go against something inside me...!!... so I cant comment on it, I do believe you though , you have proved it with your bows.....maybe I'll have to try on my next one!!!... Is there an old tradition of this method of flash carbonising? or did you discover it your self?
Also how much difference does smoking the bamboo make ? I have tried this but not seriously enough to notice any difference.
One more question..Have you ever tried Indonesian black bamboo? It is seriously harder than moso, much harder, but the 2 times I made a bow from it the belly crysalled and virtualy collapsed, which didnt make sense to me considering its hardness!!
Dave
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Apparently Moso is still very hard but the depth of power fibers is very minimal.
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diameter size and compactness of power fibers can have a great deal of of varying effects also,whether on the back or belly. also age of the boo can make a large difference,,, too young not good,, too old not good either..
as far as discovery of flash tempering bamboo,, i discovered through trial and error,,, many many pcs were used in different stages of temper on many bows of the same design and specs, this is how i regulate target poundage in the bow, also overbuild , that way you keep front profile shape when tillering from the sides.
ten bows, same design, same specs,each belly boo tempered different,, from barely noticable to pecan color to caramel color to chocolate to all out coal black, will have tremendous changes in the end poundages, compression will be better on the darker bellies as will the cast will be better too
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thanks, I'll have to try it. I believe you use a gas torch?
yes the black(ish) bamboo was only 4" diameter, smaller than I usually use, therefore had higher crown, so could acount for the belly being crushed.
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Yes I wouldn't have believed it was possible. Basically you are putting out the flames with one hand while torching with the other using a big torch. Obviously you want to do this before you grind the bamboo or it burns the thin edges
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If a bowyer was to make many of these styles the difference in bamboos brings up for me the need to get it yourself so you can select the right variety and age of culms. Or get them from a known source that selectively harvests them