putting glass between lams?

[Kirkll]

Makes sense Mark- So that was what Nate steen /sunset hill longbows was trying to convey in his blog- changing the neutral plane by adding glass under the first lam under the back to cause more compression in the belly hence increasing performance.

Except it doesn't increase performance...... adding mass weight to the limbs kills that theory. 

Something doesn't sound right to me on this theory anyway... if you doubled up glass thickness on the back vs the belly it seems to me it would carry more of the limbs load in tension and lesson the compression load on the belly side.  Am I missing something here?

[mmattockx]

Something doesn't sound right to me on this theory anyway... if you doubled up glass thickness on the back vs the belly it seems to me it would carry more of the limbs load in tension and lesson the compression load on the belly side.  Am I missing something here?

You have it backwards. If you double up glass on the back it shifts the neutral axis towards the back and results in higher stresses on the belly.

If you want to optimize limb weight you would use lighter glass on the back (or trap the limb for narrower glass on the back) and heavier on the belly since the compression side will almost always fail first if they are the same thickness. This gives higher stresses on the back where it can carry them more safely and lower stresses on the belly where it needs some help.


Mark

[Kirkll]

I guess I'm ass backward then... I've always trapped my limbs to the belly side to help lower draw weight. But I sand the glass more aggressively on the back than the belly. So I guess I'm only half ass backwards eh? 

[mmattockx]

I guess I'm ass backward then... I've always trapped my limbs to the belly side to help lower draw weight. But I sand the glass more aggressively on the back than the belly. So I guess I'm only half ass backwards eh?

Since weight is more sensitive to thickness than width you were probably balancing that out without knowing it. Whatever gets it done in the end.


Mark

[Kirkll]

I guess I'm ass backward then... I've always trapped my limbs to the belly side to help lower draw weight. But I sand the glass more aggressively on the back than the belly. So I guess I'm only half ass backwards eh?

Since weight is more sensitive to thickness than width you were probably balancing that out without knowing it. Whatever gets it done in the end.


Mark

All i know is that they balance out and perform well well with my particular limb designs. What i have noticed is that dealing with deeper core long bow limbs using a  narrow profile, adjusting draw weight by trapping the limbs and adjusting the width profile is much more effective than recurve limbs. There really isn't any noticeable advantage to trapping a recurve limb in the working portion of the limb. I do trap the hooks a bit to eliminate mass weight. So they end up in a spiral trap. Stability in a recurve bow is all about geometry and backing choice.

Using a twill carbon, or bias weave 45/45 on the back of the limb will stabilize a very thin limb of low draw weight. It seems like once my thickness gets lower than .190 at the base of the hook, things start getting squirrelly.I wont build a static tip recurve less than 38# without carbon backing now.

[Longcruise]

You have it backwards. If you double up glass on the back it shifts the neutral axis towards the back and results in higher stresses on the belly

That's always been obvious to me and i could never figure out why some builders trap the belly??

[Crooked Stic]

Nah Kirk ur actually real messed up. 
Go on Utube and watch Shane Uraks vid on his new model Hudinni longbow. Then tell us what you think.

[Kirkll]

Nah Kirk ur actually real messed up. 
Go on Utube and watch Shane Uraks vid on his new model Hudinni longbow. Then tell us what you think.

Well i think you can have that Hudinni design Stic. The design is vertically unstable, and that part about a carbon core holding the tiller shape is total hog wash.

You want to build those floppy limbed long bows... Have at it.

[Crooked Stic]

Oh Kirk I agree 100 percent on the carbon thing.