Boo Backed tiller discussion

[Badger]

   Something I have noticed this past year. I changed my tillering style a little bit because I felt like I was having too many boo backed bows pop splinters. Normally I keep them very stiff out of the fades, and a very stiff outer limb with the majority of the bend in a 12" area around the middle of the limb. My observation is this. The splinters quit popping but I picked up a tad of handshock, not bad or even aggravating but I can feel it where before they were dead in the hand. I also lost just a tad of performance. My conclusion is that I like the higher percentage of successful bows so will probably compromise between the two styles, little more limb bending closer to the fade and maybe a little more outer limb slightly bending. Because of the crown on boo making them wider really doesn't do much besides make them wider, no real benefit I can see.

   Anyone else notice anything similar?

[Bryce]

I've tillered boo backed bows many different ways in many different styles and demensions.
Not one has popped a splinter or broken.
And I really like the way you brain works Steve. But properly selecting your boo and node placement are important factors to consider. Along with a properly prepped back.

Cheers

-Bryce

[Badger]

  Only ones I have had some problems on are the heavily reflexed ones with a very short working limb area. Still my favorite bows by far but I think I just may be right on the edge with what they can handle. I don't sell bows but do trade now and then. Guys will always ask for one as fast as the one I am shooting and I don't feel as confident giving a bow away built so close to the edge.

[Jim Davis]

Steve, why would making  the limb wider not do  anything? The bamboo (or most any wood) is far stronger  in tension  than  the belly wood is in compression. The back is already able to handle more than you can give it. So, if it's lifting  splinters, it's because the overall thickness is too great for the amount of  bend.

If you make the limb wider and a little thinner, you should get back in the safe zone. Make sense?

BTW, how thick are the limbs?

Jim

[KS51]

I think you may be seeing 2 affects from the tillering change.  The first, by bending more at the fades, you have more limb mass moving a net further distance, so there is a bigger shock wave produced when it all comes to a "stop"at the end.
Second, by decreasing the radius of bend in the center section, you are also reducing the strain at that region and more evenly distributing the stored energy through the limb. The reduced strain-stress keeps the splinters from occuring.

I wonder if the net efficiency is reduced between the 2 styles of tillering?

Ken

[Badger]

  Jim, I go a little wider but I find with the high crown on boo after about 1 3/8 the edges are not doing much. I was not having problems with complete failures as much as picking up a splinter mabe 1/8 wide on the boo. Most of the time they don't pop a splinter right away either, sometimes months after the bow is finished. Might not be as bad as I amking out anyway, I have probably built a few hundered boo backed bow by now, I imagine I have had 10 or 15 pop slinters.

  Ks51, I get much better performance by crowding the tiller into a shorter working area, I think I have found a decent compromise. This is one of the main reasons I have been looking harder lately at the deflex handles, they would much better conform to the style tiller I prefer.

[mikekeswick]

Deflex will make all the difference. Some deflex will allow you to keep the thickness mid limb.
A thicker limb returns faster than a thinner limb bent to the same degree (all things being equal) so the deflex will lower the overall strain whilst keeping the faster return speed of the thicker working limb.

[RT]

Hi Badger,

I read on you post about pop up splinter on you boo. I live in asia and I am using different species of bamboo that you are using ( I have received and also compared the moso boo from bowyers from US, believe these boo comes from china)

what is different with my boo?

-node to node spacing is 16 to 19 inches
-mature and very hard

if you are keen to try out some, please send me a PM to robintan188@gmail.com     
 

[RT]

[Badger]

 R.T.  Those would certainly be worth trying, they look good.