Perry reflex

[DC]

my guess is that creep would be dependent the stress level, so you might be onto something Don, but not live long enough to see it happen if the stress is not high enough.

Why would it take so long? You can ruin a bow in a few weeks leaving it braced.

[Allyn T]

I feel like if it happened that fast people would have already noticed a pretty quick decline in performance and their perry reflex bows. so either it doesn't happen or there are other forces at work or maybe all the energy comes from moving it to brace and drawing

[DC]

The only thing I can relate to it is a raw log. If you let a log cure it can build up stresses that don't release until you split it. Then the two halves go their separate ways. Maybe, as in a braced bow, only the wood that is not constrained can move. Like the belly of the bow is only pushing against air so it can move but inside the bow it's pushing against other wood and so it can't go very far.

[willie]

a braced bow is half drawn if you look at how far the tips come back when bent. a gain from perry reflex is quite a bit lesser

a log drying gets the internal stress from drying shrinkage.  each cell is shrinking and pulling away from its neighbor

[Allyn T]

That kind of makes sense to me but at the same time when set happens it's not just the very outside cells that get crushed it's the ones further in so I feel like the wood could still suffer from set even though it has other wood pushing against it.

[mmattockx]

I'll bring this up again because there's different people here now. If I string a normal bow and stand it on the back porch for a year it's going to take some serious set. Why wouldn't Perry reflexed bows sort of stretch(or shrink) and loose all those internal tensions over time?

I expect it is as willie says and the internal stresses are low enough to not suffer from creep to a measurable degree with bows featuring a typical or 'normal' amount of Perry reflex. Maybe someone needs to glue up a test piece with enough reflex to induce the same level of strain as a bow sees at brace and then report back in a few months?

It would be an interesting experiment to try. Maybe I will try it with some scrap wood once I am done my first lam bow if I remember it at that point. The problem is there are so many things to try and only so many available hours to do them in...


Mark

[Selfbowman]

Ok guys if you build a55# bow and it takes  say2-1/2” set will the bow retillered to 45# bow with a better tiller job will it have the same set?  Arvin

[simk]

in my experience: what you loose does not come back.

[bradsmith2010]

just keep stress to a minumum to prolong life of the bow and yourself,,

[Selfbowman]

So we are crushing cells in the middle of the limb ?

[willie]

So we are crushing cells in the middle of the limb ?

not at the very middle, or where the stress is neither tension or compression. It is the worst at the surfaces and progressively less towards the middle. 

[mmattockx]

Ok guys if you build a55# bow and it takes  say2-1/2” set will the bow retillered to 45# bow with a better tiller job will it have the same set?  Arvin

I think Badger is the man to answer this question.

So we are crushing cells in the middle of the limb ?

Not into the center of the limb, but that much damage would likely go deep enough that going down to 45# from 55# won't get rid of it. To drop from 55# to 45# only requires a 6.5% limb thickness reduction. If your limb is 0.5" thick, that means you only take 0.0325" off the belly ( for reference 1/32"=0.03125"), which won't be near enough to get rid of the damaged cells.

Badger has commented that when he is tillering a bow using his no set method if he sees a 50# bow start taking set  before he is close to his target draw length that he immediately drops it to a 35# target weight and goes from there. I suspect some of that is due to the weight classes in flight, but that gives you an idea of how much drop it takes to lose damaged wood and that is not after 2.5" of set, but as soon as set becomes measurable on the tree.

just keep stress to a minumum to prolong life of the bow and yourself,,

Wise words indeed. 


Mark

[bradsmith2010]

yes if you re tiller, i dont think the set is gonna change much,,

[Selfbowman]

Thanks Marc I will store that information in my little forgetful head. Arvin

[DC]

Ok guys if you build a55# bow and it takes  say2-1/2” set will the bow retillered to 45# bow with a better tiller job will it have the same set?  Arvin

Sometimes a bow made with Perry reflex will gain reflex as you tiller it. Usually happens in the earlier stages of tillering but  in the situation you've described it may gain a little reflex which would hide some of the set. I wouldn't count on it though. Notice that there's a "sometimes" and a "may" in my message. I think they combine exponentially