Bamboo static & dynamic spine different vs wood/carbon

[markliep]

Hi all - love my carbon & spruce shafts & want to love bamboo too, but I'm still trying to find the sweet spot where I dont have either a light over spined arrow or a heavy correctly spined one.

From what I've noticed so far bamboo looks to have a lower static spine with a higher dynamic one - this is based on the observation that bamboo shafts deflect more under the same weight than either spine-matched carbon or spruce but then shootnhigh & Lt; adding weight to the tip corrects this BUT then I end up with an arrow heavier than I want. Context is that I'm trying to match the bamboos weights to existing broadhead carrying arrows.

So my question is: are any of you aware of any spine guidelines for bamboo that are different to those that we use for other materials?

Thx as always for your accumulated wisdom - M

[AkDan]

its interesting on lower static vs stiffer dynamic.  overall Arrow weight would play into things.  I'm trying to see this in my head (long night at work).

Maybe sorting shafts and picking out lighter OAL weights with the spine your looking for.  (again its been a long night and I probably have that backwards LOL!)  dont forget you can add weight to the nock end to help with spine, but alas it'll likely add too much...oh the fun of natural materials!

It's very similar to shooting soft woods vs a heavy hardwood, and its relation to dynamic spine, though I think boo/cane is overall more forgiving of spine as a hole.  There's an interesting article in Klopsteg/Naglers book about harmonics and how they tested for it.   Taking arrow selection another step closer to identical.   Maybe we settle for less in woods today I dont know.

[stringstretcher]

Yes, there is a large spine difference in the way that you use them.  On all cane, you automatically want to add 10lbs of spine to what you are looking for.  This is because of the natural taper of the bamboo.  You also have to add or substract 5lbs of spine, adding for anything over 28", and substracting 5lbs for anything under 28".  You would do the same with point weight, add 5 lbs for every 15 grains of point weight, or substract 5 lbs for every 15 grains under.

How you place the node in relation to the strike plate is also very important.  The leaf scars, the indentations at the node, have to be place at the 12 and 6 o'clock position, with the stiffest of the two sides against the strike plate.

[markliep]

Thx - didn't know the orientation rules so that might make a difference - otherwise it looks like the basic rules still apply & that I'll have to find the sweet spot between point weight & shaft weight .... Those carbons are looking pretty simple now - M

[Cromm]

12 and 6. I will have to try that as I was told 3 and 9. But still with the stiffer side against the bow.