String tension correlation to brace height

[Watsonjay]

As we know every bow has a sweet spot for brace height. Has anyone ever checked if optimal brace is also maximum string tension or are they unrelated?  Thanks. Getting ready to do testing myself.

[Crooked Stic]

Lower brace equals more string tension.
That does not mean the bow is ats its best brace. Can't explain it. Got something to do with the lever effect I think.

[Watsonjay]

Lower brace equals more string tension.
That does not mean the bow is ats its best brace. Can't explain it. Got something to do with the lever effect I think.

So optimal performance doesn't equal opty shot. Got it.

Sounds like what I need to do when designing a limb is make a shape that produces the most string tension then adjust to optimal brace and hope it doesn't reduce string tension too much.

[Rob DiStefano]

All that matters with brace height is what works best for good arrow flight and full draw/release ergonomics. 

Change arrows and form ... and brace height may need addressing again.

String type and strand count plays its part, too.

There sure are other considerations as well.

[Kirkll]

Typically the lower brace height# will always give you additional performance. Longer power stroke. But... like Rob stated above. There are other factors that make a difference. 

Example... I much prefer shooting a 7-7.25" brace just for arm clearance reasons alone. I don't use arm guards. In hunting conditions where I have a coat, I'll use a knee high tight women's stocking an cut the toe out. Nylons work too, but don't hold up as well as the tights do.

When designing a limb, I get the limbs bending the way I want with maximum performance and string tension. Then I measure back to the string for the grip location at 7". Shaping the grip is the last thing I do. Everything is tillered and weight is dialed in before I touch the grip area or the shelf cut out.

[Kirkll]

Lower brace equals more string tension.
That does not mean the bow is ats its best brace. Can't explain it. Got something to do with the lever effect I think.

What exactly is "The lever effect" ?  Should that be added to the bowyer terms summary?  

[Watsonjay]

Lower brace equals more string tension.
That does not mean the bow is ats its best brace. Can't explain it. Got something to do with the lever effect I think.

What exactly is "The lever effect" ?  Should that be added to the bowyer terms summary?

My interpretation and thought process is like a static recurve or siha. Because the end of the limb can't flatten out with added force it adds extra pressure at the bace of the siha or static tip making it move in a smaller diameter arc allowing it to return to its brace position quicker than if it could flatten out and move in a bigger arc.


Stand on one end of a 20 ft seesaw and drop 200lb on the other. Do the same on a 10ft seesaw.

Or maybe because more of the travel of a limb at shorter brace is in more of a forward motion rather than an up and forward motion??

As I always say though. "I aint know engineer!"

[Kirkll]

Going back to your original question regarding sweet spot vs maximum pre load. You will find a spot as you lower your brace, that produces the highest rate of energy transfer to the shaft, and then it starts getting diminishing returns even though the pre load continues to increase. THAT.... is the sweet spot as far as arrow speed goes.

But there are other factors that may influence your choice of adjustment such as arm clearance, noise, center shot capacity and arrow spine can play into it too.

Speaking of arrow spine... watch these high speed video clips of different spine arrows on the same bow.  You can't help but wonder if the extra flex in the shaft that absorbs the stored energy is lost, or retained with the spring back as it leaves the string.

Btw... using a high speed video camera to film the bow in a shooting machine can give you a lot of information. It really shows in detail what those limbs are doing after Elvis has left the building.


https://youtu.be/_KLBN1JqCmw?is=CCjuVDVCzUoVE9fz


https://youtu.be/rqO6WkXJ87A?is=UMr9dbBNlX-TR73I.


I can't  find the video of Borders super curve bow in action.... That one would blow your mind.