how to use bamboo as belly- please help (have no idea how to do it)

[sleek]

Considering how dogs are fast runners, i never understood the expression.

[dragonman]

 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

[bubby]

http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=001887;p=1
Maybe this will help you out

[arachnid]

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

[Badger]

 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.

[sleek]

Why wont pine work as a core? I know cedar will.

[arachnid]

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....

[sleek]

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.

[dragonman]

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

[arachnid]

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?

[Gaur]

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.

[dragonman]

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

[arachnid]

Which core will give me better cast- bamboo or ipe? Will it make such big of a difference?

[Gaur]

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.

[dragonman]

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