Face or back

[Flem]

What the he!! are you guys talking about?

[Mad Max]

Thanks Walt

we are waiting on you Flem

[Flem]

I am seeking another path for the answer to the "neutral zone"

[Longcruise]

I am seeking another path for the answer to the "neutral zone"

Guess I've been MIA here after getting this started.   Had family commitments.

Im very impressed and intrigued by the contributions to this topic.

So, Flem,  is it a neutral zone that is being sought?  I kinda share that view but wonder what materials and placement will give the best results.   

What is happening in the balancing act between back and belly?  Is the belly a drag on the effort of the back?  Does the belly need to push harder?  Would that be an improvement in performance?  Or, is it better to emphasize more tension in the back?

Flight bow builders are obviously maximizing to some degree even to the point that a highly performing Flight bow may have a very limited life span.   When they die is it the back or belly that goes?

[Shredd]

Good one Flem...   

   Maybe Allen will chime in on flight bows...

[Roy from Pa]

Note to self..

Roy, do not click on this thread again:)

[Shredd]

Most glass bows break just outside of the fade.

That area is a high stress area.

With thousands of shots out of a bow, sooner or later a weak spot is created there.

My old bear 1972 takedown, with prolly 10,000 shots out of it, broke just outside of the fade.

Wasn't a glue failure, just finally got weak enough and broke while at full draw.

That was exciting as hell:)

I have come to the conclusion that most bows are like guitar strings...  They are eventually gonna break from use...

[Flem]

So instead of looking at the neutral zone as something seen from the outside, I have decided to become one with the neutral zone. The view from inside, looking toward the back and belly is enlightening.
Since everything in the physical world we know is trying to reach dynamic equilibrium, homeostasis, Yin/Yang or whatever you want to call it, we have to decide do we want our Bows to be in balance?
Do the materials we use store more energy and return to their resting position faster, when in tension or compression? What is the optimum balance between the opposing forces? Do we try to establish the position of the neutral zone or do we leave it to destiny? 

[Bvas]

Why doesn’t someone build a relatively simple bow. Perfectly flat limbs, with a perfectly centered riser. .040 glass one side, .030 other. Cut string grooves so bow can be strung and drawn either direction.

And before anyone says it........I have time to think about, not to do it.

[kennym]

Thats a great idea Brad, when ya startin on it ? 

[Roy from Pa]

Why doesn’t someone build a relatively simple bow. Perfectly flat limbs, with a perfectly centered riser. .040 glass one side, .030 other. Cut string grooves so bow can be strung and drawn either direction.

And before anyone says it........I have time to think about, not to do it.

Sure Bvass, come in here and throw wood on the fire and leave:)

[Mad Max]

So instead of looking at the neutral zone as something seen from the outside, I have decided to become one with the neutral zone. The view from inside, looking toward the back and belly is enlightening.
Since everything in the physical world we know is trying to reach dynamic equilibrium, homeostasis, Yin/Yang or whatever you want to call it, we have to decide do we want our Bows to be in balance?
Do the materials we use store more energy and return to their resting position faster, when in tension or compression? What is the optimum balance between the opposing forces? Do we try to establish the position of the neutral zone or do we leave it to destiny? 

Maybe Gordans or who ever made the first glass figured that out for us.
And YES Safety would be calculate in that.

[Buemaker]

I had chicken wok and beer for dinner, I’m in perfect balance. I can be bent in any direction.

[williwaw]

"And an excessively strained glass lam in tension, seems to fail when the epoxy in the lam separates from the glass fiber?"

Perhaps that's partly what I saw. But the glass fibers themselves were failing too. If you fold your hands by interlocking your fingers and then straighten your fingers so they stand up a little, that's what the glass fibers were doing. Did they 'come unglued' and then break, or vice versa? I don't know.

These bows had seen decades of regular use before failing.

No glue joint issues in those bows. They stayed together. Yes, there were other root causes concerning how the fadeout was executed, it acted like a hinge of sorts, creating much strain of both types in a very specific, isolated spot, and it seems to me at least that if glass was weaker in compression resistance, that it would have failed there in that spot in compression and not tension.

Has anyone ever seen glass fail only in compression? As in crushing, fretting etc... without wood or glue joint failure?

Jeff,
thanks for the followup of your observations. I should mention my "excessively strained" observation was of a test specimen,  newly constructed and strained to complete failure, well beyond normal design stresses.  As for the glass fibers failing in your repair bows.  I have no doubt that long term usage at some stress near the working limit will cause some breakdown in the glass fibers. Also, if you take a strand of glass from new e-glass roving and dissolve away the sizing, it can be easily seen what appears as a "continuous" fiber is in fact only a collection of shorter strands.

  Is the belly a drag on the effort of the back?  Does the belly need to push harder?  Would that be an improvement in performance?  Or, is it better to emphasize more tension in the back?

I will venture a wild ass guess that if there were more drag or hysteresis in compression or tension, it would have been confirmed by now. The technology of fiberglass has not changed all that much in 70 years.  Having all areas of the working limb, front and back, working as close to the limits you choose in your design, would seem to be the way to optimize.

[mmattockx]

Do the materials we use store more energy and return to their resting position faster, when in tension or compression?

For linear elastic materials they will store the same energy either way. I don't know if our composite lams behave close enough to linear elastic or not for that to work. Gordon's published info says their lams have the same elastic modulus in both tension and compression, which indicates they are very close to linear elastic behaviour.

Also worth noting is that Gordon's lists the tensile strength of the ULS lams as 152,000psi and the compressive strength as 119,000psi. The UL lams have a tensile strength of 152,000psi and a compressive strength of 111,000psi.

Good question on the rebound back to shape.

Do we try to establish the position of the neutral zone or do we leave it to destiny? 

The neutral axis is easily calculated for any given cross section shape. You certainly don't need to know what it is to build a bow, but understanding its effects and controlling where it is located are useful things when trying to maximize performance.


Mark

[Shredd]

Note to self..

Roy, do not click on this thread again:)

 

[Shredd]

Why doesn’t someone build a relatively simple bow. Perfectly flat limbs, with a perfectly centered riser. .040 glass one side, .030 other. Cut string grooves so bow can be strung and drawn either direction.

And before anyone says it........I have time to think about, not to do it.

  First sensible thing I heard all day... There yah go Longcruise...  yah got all your answers right there...

[Roy from Pa]

Yup Mike you build that bow wif some of Flems carbon lams he's gonna build and we'll have a super bow wif a perfect neutral balanced plane.

 

[Shredd]

Ok Guys...  I am about to throw a monkey wrench into this thread...

   I am not trying to be cocky, a know it all or arrogant I am simply stating what I have been through, what I know and sharing with you what direction or directions I would take... And / or to give some advice when searching for high performance...

   I busted my butt for about three years or more working toward making a high performance bow...  In that period of time I made about 40 to 50 bows... Each bow went through a bunch of tests...  The first test was vertical stability the second was speed...  If a bow did not shoot over 182 or over I threw it to the side and made another one...  At one time I had a pile of about 20 or more unfinished bows... All good bows but in my opinion slow...   I experimented with split limb, prestressed and about 4 or 5 other exotic applications...  I heard from someone that Ken Rohloff had a big pile of bow forms behind his workshop...  All not up to par to his standards for a high performance bow...  At the WTT contest he got 199 fps @ 10 gpp @ 28" with a 6" brace with carbon limbs and was a hot rod, which I am assuming that it had very narrow limbs ( maybe not suitable for constant and every day use)....  My hat goes off to this guy...  That is an amazing achievement...   My fastest bow shot 196 fps @ 10 gpp @ 28" @ 6" brace and is a basic maple/ fiberglass lay up and with standard width (everyday use limbs)...  I would have loved to be at that contest and talked with all those guys...

    The reason I am sharing this is that there is no magic bullet...  I see you all going off on these tangents talking about carbon fiber, numbers, stresses and such but not one time did I ever think I heard the word radius when talking about limb design...  In my world it is all about radius's and angles plus a few other things...  I feel as though I just scratched the surface in understanding how a bow works and what it takes to suck performance out of one...  It takes a lot of work and hours upon hours of testing and experimentation unless you happen to get very lucky and stumble across a good design with a perfect taper rate.... 

   So there is no magic bullet...  If you have a sub par design and you throw some carbon on it or try some other exotic technique you may gain 2 to 3 fps which in my book is crap... Now you got and expensive bow with carbon shooting 178 fps instead of 175 fps...  If you have an optimal design and cannot go any further with geometry then is the time to pull out the tricks with carbon fiber and such...  Until then it's just talk and a waste of good $$ When you can do better with maple and f/g...  It is ok and nice to understand how carbon and other things work but I think the real effort needs to go towards design and I am seeing very few on here making the efforts of making 15 to 20 bows to refine a single bow design's performance...

   So the bottom line is if you all want to be real about this performance thing and want to work as a team to reach higher performance I would start comparing notes on geometry first until you cannot go any further in performance before you start discussing carbon and theories and such...

    This is just my opinion... 

After I reached a certain level I now see a little bit of the light on performance... (I feel years of hard work away from where I would like to be)...  I now shed a little of that light on you...  If you spend a lot of time researching and applying exotic applications to a sub par design I feel that you are stumbling in the dark...  Although it probably does feel good talking about the Magic Bullet and having some kinda hope that an application of such an exotic is gonna take your 170 to 175 fps bow and bring it up to 190 fps...  It's not happening...

[Buemaker]

Shredd’s bow tested by Cody Greennwood at 196 feet 9 grains pp. and 188 feet 10 grains pp.It was the fastest of the ones tested.
https://www.thetradlab.com/reddbowrecurve