Prestress and Performance...

[Shredd]

  Just stumbled across this and thought to share it with you guys...  If you want to improve performance of a bow you might consider applying one of these techniques or principles to your limbs...  Anyway, some food for thought...

[Pat B]

Did you forget something, Shredd?   

[Shredd]

  Like what??    

[Shredd]

  And my name's not 'Shedd'...   

[Buemaker]

????

[onetone]

Methinks Shredd has forgotten to post a link.

[Shredd]

  LMAO..!!! 

Methinks you be right... I worked a long hard week and I am half dead today...

[Shredd]

Here she Be...

   

[onetone]

Thnx Shredd, I’ll watch it tonite. 

[Pat B]

Fixed!   

[Shredd]

    You guys are awesome...  Don't know what I would do without Y'all...   

[mmattockx]

If you want to improve performance of a bow you might consider applying one of these techniques or principles to your limbs...

That was a good explanation of prestressing concrete structures. This is essentially what I am doing with my Perry reflex lam bows. I prestress the belly into tension in the unbraced position so that it sees a lower maximum compression stress at full draw. I'm not sure how applicable it is to FG lam bows but the technique could be used on the cores of HH or ASL bows to minimize how much set they take.


Mark

[onetone]

Shredd - Interesting explanation of prestressed concrete beams.  Altho the function of beams is different than that of springs -bow limbs- it seems the same principles and forces are at work in both. I think Max was applying the principle of prestressing in his recent “Extreme Bow Reflexology” build-alongs e.g. see, All Fired Up. I mean 9-10” of reflex in a 48” bow is mind-bending, to me at least. Now that’s preload!

[garyschuler]

I prestressed quite a few of my later longbows. Glued the lams up to the belly glass on a separate form and then glued to the reg form with the back glass. I’d I have to go back on my records as I have not made a bow in 5-6 years for the actual process. It was based on Fred Anderson’s style of bow building in his books snd research. Not a new Theory as it was being done years ago.

[mmattockx]

I prestressed quite a few of my later longbows. Glued the lams up to the belly glass on a separate form and then glued to the reg form with the back glass.

What shape were the first form and the second form?


Mark

[Mad Max]

 

[beachbowhunter]

If you Google Harold Groves, I believe he was a pioneer in pre-stressing, dynastress I think he called it.

[Kirkll]

The pre stress in a bow limb using fiberglass or even wood is already being done by shaping the reflex in the form.

After watching this engineer explain the theory of a Post tension concrete floor or beam, it makes a guy wonder if you could run some piano wire in the core of a limb and adjust the tension after the bow was laid up. 

This would sure add some strength to a straight ASL design, but I have no idea how it could be done effectively.     I’ve built a lot of PT decks on parking structures and built 4-5 story buildings on them. So i I understand the concept….. but… I seriously doubt it could be incorporated into a bow limb.     

Kirk

[mmattockx]

The pre stress in a bow limb using fiberglass or even wood is already being done by shaping the reflex in the form.

You don't get much in the way of induced strain in a FG bow because the lams are too thin and flexible. In an all wood bow you can generate enough strain to be significant if it is done right. This is what Perry reflex does.


Mark

[garyschuler]

Came across this on Fred Anderson’s builds.