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

[arachnid]

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

[dragonman]

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

[arachnid]

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...

[dragonman]

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!!

[tattoo dave]

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

[Limbit]

Heat treat first! Bamboo does really well as a belly wood when it is heat treated.

[arachnid]

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?

[dragonman]

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.

[dragonman]

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

[arachnid]

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

[dragonman]

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

[Gaur]

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

[Tuomo]

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!

[arachnid]

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? :-/

[bubby]

A dog would be bad, a slow bow with poor cast