Steam bending bamboo recurve?

[nabiul]

Hi everyone; long time shooter, first time bowyer here looking for some advice on bending some recurve+reflex into bamboo limbs. I've spent the last month learning the quirks of working with this amazing material and have had some failures so I thought I'd ask people with more experience before I ruin any more limbs. The problem I'm having is that while trying to bend a modest recurve the inside fibers of the bamboo always fail in tension. My first attempt was with a heat gun and I quickly learned that the material I'm working with is far too dry for this to work. My second attempt was with a 24 hour soak in water followed by steaming which worked for recurving the tip, but the shallower reflex didn't take on the rest of the limb; also once I removed the limb from the form a day later it began to straighten out. I figured that the straightening was from drying so I tried another steaming without a presoak this time and the inside fibers failed again. I'm thinking of trying a bending strap next, but will it actually do anything? As you know the grain is parallel in bamboo and it doesn't lift splinters like the strap is supposed to prevent. Do I need to make the limbs thinner for a successful bend? The form I'm using now has a pitifully small recurve/reflex and what I really want is something closer to the amount an asiatic bow has.

[Bayou Ben]

I'm not sure about bending boo that thick as I've never tried it, but thin bamboo bends like a dream.  This was after maybe 2 minutes with the heat gun.

[bassman]

 

 


Nabiul,this bow is made from bamboo slats that were belly heat treated.A lot of the back set does pull out,but if if you angle the limbs up from the riser ,and use  longer ,sharper angled Siyahs you can come close to the profile you want.This one ended up with inch and half back set.It has a glued on handle, and wrapped. The siyahs are short to get the poundage I wanted because the slats were thin. It is 48 inches long ,and 45 lbs at 26 inches with cut in arrow shelf. Fun bow to shoot.

[bassman]

More pictures

[nabiul]

Thanks for the replys guys. Nice bow Bassman, I'm considering doing glued on siyahs if all else fails but for now I really want to make a bow with smooth sweeping curves if possible. @ Bayou Ben, now that's what I wanted to see; I need to make the limbs thinner. But how stiff is that thin piece you've got? I don't suppose it would be strong enough for a 30# bow?

[leonwood]

If you want a smooth curve you can heat recurve in a thin piece of wood (maple works great) and glue that on the belly of your bamboo recurve (or flattened back if you use the bamboo in reverse). With the added glue line it will definitely hold the curve better.

If you want to make better use of the bamboo powerfibers you can glue 2 pieces of bamboo for back and belly with the pre-shaped wood recurve between it in the tips

[Bayou Ben]

Nabiul, no that piece in my picture won't make a bow by itself.  It was thinned for a backing. 
I guess your options would be to make your bow like bassman's, or glue two bamboo slats together like leon mentioned. 
I personally want to try a bamboo back/ wood core/bamboo belly bow with the boo on the belly charred to increase compression strength.  I believe this is best utilizing the power fibers of bamboo and would allow for shaping as you like.  But it is more complex than the options mentioned above.  Check out James Parker's bows if you haven't already. 

I received this bow as a swap and it is constructed like I mentioned: bamboo back/maple core/ charred bamboo belly.  It's pretty fast.

[nabiul]

If you want a smooth curve you can heat recurve in a thin piece of wood (maple works great) and glue that on the belly of your bamboo recurve (or flattened back if you use the bamboo in reverse). With the added glue line it will definitely hold the curve better.

What do you mean it will hold the curve better, are you saying to steam bend the bamboo after gluing on a belly piece?

@Bayou Ben, laminations are too complicated for me right now. I'm new to woodworking as well as bowyering(?). I was originally planning to do a toasted belly but I tried some blue ink on the scrap pieces and it makes the tan belly look brilliant.

On another note, how do you guys get through that rock hard crust on the inside of the bamboo? It really makes using planes difficult and tends to tear out chunks of fiber.

[nabiul]

How long is the handle section supposed to be when shooting without a shelf?

[Pat B]

I make my handles 4" with 2" to 3" fades.

[nabiul]

My palm is about 4" wide so should I have a little extra room for the arrow?

[nabiul]

Limb #1 steamed in the oven in a foil packet covered by a wet cotton shirt after an 18 hour soak in the tub. Here's hoping it takes this time, going to leave it to dry on it's own for a while and then maybe hit it with the heat gun.

[nabiul]

My fears realized as soon as I applied the heat gun, instantly the inside fibers split. This flippin heat gun has caused way more problems than it has solved. I put in a couple of drops of superglue.

[gutpile]

if I'm bending a recurve ..I always boil... jm2c... gut

[ohma2]

Nabiul, no that piece in my picture won't make a bow by itself.  It was thinned for a backing. 
I guess your options would be to make your bow like bassman's, or glue two bamboo slats together like leon mentioned. 
I personally want to try a bamboo back/ wood core/bamboo belly bow with the boo on the belly charred to increase compression strength.  I believe this is best utilizing the power fibers of bamboo and would allow for shaping as you like.  But it is more complex than the options mentioned above.  Check out James Parker's bows if you haven't already. 

I received this bow as a swap and it is constructed like I mentioned: bamboo back/maple core/ charred bamboo belly.  It's pretty fast.

you are right Ben i shot a bamboo dragon from James for a couple years theyr quitr a bow .i know you could make one work too.