violating the bamboo nodes

[msamn]

Hi All, I'm a newbie, with a perhaps a naive question. I am planning to try to make a bamboo backed bow, but I really don't like the look of the bamboo nodes. I want to sand them down to near nothing. I still want to use the bamboo backing for its tension quality though. So here's my question. What is the "penalty" for node violation? Will it splinter, will it be weaker? will it not hold reflex/deflex?
many thanks for any input.
     

[Pat B]

I think that the boos tension strength will be deminished by reducing the nodes. If you don't like the look of the boo try Hickory backing. It is quite strong in tension and way less work than boo backings.     Pat

[Aeronut]

I sand the node down to round it off and have not had any problem with it.  I leave it raised just a tad.

Dennis

[msamn]

Many thanks for the replies and suggestions, I think that I would like to use Hickory as an alternative but I have not been able to find any locally. I live near San Francisco. I have been able to find some sources for bamboo and still looking around for hickory. In the meantime, I will try the bamboo and take the chance on reduced tension.

[yakstone]

Sanding the nodes flush will not weaken the bamboo in any way. Fly rod builders have been building rods that way for years.
I sanded the nodes flush on the bow that I built and got a much nicer looking stick with no loss of strength.

[Springbuck]

I disagree with Yak (respectfully, of course).  I, and many people I have heard of, have had bad experiences with totally flattening nodes.  

  If you look at a node in cross section, you will see why.  The outer power fibers curve outward with rise of the bump at the node.  If you flatten the node, you will be cutting those fibers offshort, and that leavesstubbed fibers that can lift.

  If you want to experiment, flatten the nodes on a piece of bamboo and prep it for a backing, then bend it till it breaks or splinters and look where the splinters start from. It will be the nodes.

  You might get away with it, but I wouldn't count on it.

[Aeronut]

Sand the bamboo down real thin for backing, 1/16" or so at the tips tapered to 1/8" or less at the handle.  I left mine thicker on my first bow and wound up over stressing the Osage.  I have many frets on the lower limb and it is a wall hanger now.
 

Dennis

[Glenn Newell]

I keep an eye on the limb during the tillering process and weaken the nodes if I have to to get the limb to bend there. I didn't do it on one bow and the limb failed under the node....Glenn...

[John Scifres]

It sometimes works but often doesn't.  I just take the rough stuff off.  The type and quality of bamboo makes a difference.  If you want to build a bamboo backed bow, get Dean Torges video "Hunting the Bamboo Backed Bow".   www.bowyersedge.com

Or you can play and learn all the lessons for yourself.  That's fun too.

[msamn]

I have Dean Torges' dvd "Hunting the Bamboo Backed Bow",  and he states that you should not violate the node, but he does not say why.

[Pat B]

The node is the weak link in the boo. That is where the longitudinal fibers join. As well as strength, a boo backing is also aesthetically pleasing to look at and I like my boo backings to look like boo backings. I do sometimes remove the little corky ridge but that's about it.    Pat

[Diamondback59]

justin  snyder ,, had sent out some info a while back on some action boo  i belive it was on his stick bow site  from what i see in the pic s you might get a hold of him see if he  has any in like 1/8 strips and try that as i think thats a laminated type of bamboo  without the nodes  i have no experince with it  i like the moso and the nodes to show  the real thing on my bows  brock

[Springbuck]

Glenn has a good point.  It is possible to have a node so humped up and stiff that a belly lam ends up very thin, and then, since the wood is harder than the bamboo, but you have removed it, the bow can hinge at the thin spot, even if the limb overall seems thick enough.

  I avoid this by making the bamboo as consistent as possible between the nodes, or have as consistent as possible a taper.  For instance, if you are making a backing that is not supposed to be thickness tapered and the calipers tell you 1/8" between the nodes at the middle, 1/8" just off the node to the right, but 7/32" just off the node to the left, it will probably mess with your tiller.  I try to get as much of the "flat" between the nodes consistent as possible, then let the nodes be what they are, but as small a bump as possible.

[mmgrode]

Yup, fiber violation is bad news on bamboo backings which are highly stressed, unlike fly rods.  Taking the node down flat with the rest of the boo is asking for trouble as is scraping too far past the rind.  Personally, I like the nodes.  Heck, it's always the first thing people ask about when they see my bows. You might be able to get away with it on lightweight bows, but not with heavier bows. Happy bow building!

[msamn]

My intention is to make a light weight bow of about 35 to 40 pounds. This is for target shooting and not hunting. So maybe I can get away with sanding down the nodes. I think that I will experiment with it and just see what happens. Thanks to all your contributions and suggestions. I see what might happen if I violate the nodes too much, so now I know what to expect.