Riser length to limb length ratios and hand shock

[bornofmud]

So I was thinking about this and wanted to get some second opinions.  I use a 22 inch riser in my longbow design, and just made a 68" bow.  I was thinking that for my draw length, 66" might be better to get a bit more tension in the limb.

So here's what my problem was.  If the bow is 66" ntn, that means that each section of the bow is 22" (as in 22" limb, 22" riser, then 22" limb again). Thinking from a music perspective, 1/3 of the string length would make the 5th of your root note. This means that there would be a peak in vibration directly in the center of the bow.  Would this create more hand shock than a bow that had uneven limb lengths compared to riser lengths, or is there always going to be a peak vibration in the center of the bow just due to the design of the object?

Sorry if that was confusing, hopefully you understand what I'm getting at haha.

[bornofmud]

The reason I bring up the music is because a 5th is the most consonant sound there is other than a note's octave.  This means that more of the energy of the bow bouncing back into brace would be transferred to motion in the center of the limbs and the center of the riser.  I wondered then if it would be preferable to have a dissonant vibration, such that some of the vibrations cancel themselves out, or at least move the peaks of vibration away from where the hand grabs the bow. Would this be an accurate assumption or am I not considering something?

[bamboo]

nick you may be over thinking it--then again maybe not!!
but using you line of figuring--wouldn't it make more sense to do your calculations with string length-say nock to nock braced--I'm thinking --nut to bridge
understand I'm no engineer---but from where I stand--I would rather the energy be transferred  to the arrow than canceled out.....
I'm listening

[halfseminole]

You don't want dissonance.  A fifth and an octave are OK, but any dissonance would be felt, I should think.  Think horn fifths.  Sympathetic vibrations might be an issue, but I think we'd need physics software to model that.

[bornofmud]

Bamboo, I thought about that too, but I figured that it's not so much the string vibration that creates handshock as it is the limb snapping back into brace. Plus, no matter the length of string, the center will always vibrate most because that's where you're pulling it (there are not three parts on a string, only two, the side above your fingers and the side below, thus wherever your hand is will always be the peak of vibration).  So having a dissonant vibration throughout the bow itself (as in one where the nodes don't line up with the nocks and riser fades) would not affect arrow speed or the energy being transferred to the arrow.  

But yes, probably over thinking it, seemed like a simple idea in my head, but gets quite convoluted in translation to language haha.  Guess I should just make one and see!

[bamboo]

"Guess I should just make one and see!"

the only way I know of to prove any theory [or disprove!!LOL]