Increasing stored energy in laminated bows.

[RyanY]

I had this weird idea about a way to possibly increased stored energy in a laminated bow. The idea is that gluing laminations that are twisted into a straight profile would increased stored energy. For example, in a bow with four lams the back and belly could be normal but the middle two could be steamed and twisted in opposite directions before glue up. Of course this would increase the chances of twist in the final product with increased difficulty in keeping everything symmetrical. But would gluing twisted lams together increase stored energy for the bend of a bow? Just a crazy idea I'll likely never try but any thoughts? Has this been done?

[gfugal]

It might but sounds like more hassel than its worth unless you had nothing better to try. I can imagine it being overly diffucult to get right with minor benefit.

[loon]

sounds somewhat like perry reflex but more wonky

[Del the cat]

Stored stress in a direction that can't be released to do useful work?
Del

[PEARL DRUMS]

Ryan the glass guys are doing something like with woven carbon. They also like to take wood veneers with opposing cuts and glue them together believing they are making more energy.

[willie]

Just a gut feeling, but I would tend to agree with Del about twisted. The larger question, of improving ways to store more energy in prestressed laminations, might still have more room to run.....

[osage outlaw]

Good to see you back Dr. Yoon.  Are you going to make it to the Classic again?

[RyanY]

I guess it makes sense that the rotational stress probably wouldn't contribute to stored energy for a bow. Thanks for the input!

Clint, I'm hoping its in the cards. Going to be a lot going on next year starting residency so we'll see. I'm praying that I can make it!

[Badger]

  I have never really accepted that the prestressing of the laminations is what gives the laminated bow that little extra boost it has. I think it has more to do with less hysteresis do to the bow being strained less while acquiring its finished profile. 

[Danzn Bar]

Good to see you back Dr. Yoon.  Are you going to make it to the Classic again?

+1
DBar

[scp]

  I have never really accepted that the prestressing of the laminations is what gives the laminated bow that little extra boost it has. I think it has more to do with less hysteresis do to the bow being strained less while acquiring its finished profile.

It would damage the wood a lot less if we just glue in the reflex instated of preforming the laminates through heat bending and gluing them.

One way to test the effect of pre-stressing would be to make two identical 4-part laminated limbs; and make one by gluing in reflex with all 4 laminates at once and compare it to the other that was made by first gluing the 2 laminates each flat and later glue the two flat glued laminates into reflex. The former would have three pre-stress glue lines while the latter would have just one. But I don't do laminated bows. At most I make bamboo backed bows, still very rarely. I might try the test by making two same shape siyahs.

[Tree_Ninja]

Would a perry reflex be an example of this?


I alwayd wondered about the unwinding of a twisted limb  during a release.  I figured that the angle of force would not be tangential to the plane of the string.  There would be torque but I don't think it would translate the energy to the string and arrow.

  Snowboard makers have cross grained wood cores in order to increase strength and breaking resistance, they call these X-grain so that the grain lines up 45 degrees opposing the laminates. This is more to solve breakage from the forces being at 90/perpindicular to the edge of the snowboard. You could store more energy before breakage this way.... off topic....

 I had made a higly reflexed recurve that caused the string to fly off and would go past the arrow pass, I wondered if was allowed in flight archery to do this, as it increases stroke length and releasing all stored energy (including energy stored in brace).

[Aaron H]

I agree, great to see you back Dr.

[bushboy]

cool idea!I like to think up unique designs also.

[Buckeye Guy]

Good to see the Dr in the house
where you doing the residency
you best show up at Marshall  son
as for your question man its Christmas I ain't stressing my brain over it right now I have Grandkids to play with
see ya in the spring my friend