How does the brace height effect the left and right impact on a properly spined arrow? Thanks in advance.

low brace will make the spine stiffer and higher will make it weaker.

I agree with bigdog21 but never understood why this happens. A lower brace height gives a longer power stroke but requires less spine. Although this is counterintuitive to me, it does work this way. Anybody know why this happens?

The arrow releases sooner from a higher brace hight therefore not needing to flex as much around the riser. That's how I understand it. Some of the more experienced people can provide a more accurate answer.

It's the distance from center shot in relation to the arrow point. Because of the angle the arrow sits at BH. When BH is increased this distance is smaller. When lowering BH the angle is increased. Perhaps someone will post a picture which will make it easier to understand.

MP

George Stout is one to ask he is pretty good on this subject. he straighten me out on the subject a few years ago.

A lower brace height on the same bow--The string will not be under as much tension at brace and will travel much farther toward the bow at the shot, than a higher brace height. That increases the angle you speak of. It also can get very bad at smacking your wrist below the arm guard. >>>-------> Ken

So basically… Higher brace height equals higher draw weight equals more violent acceleration equals higher spine requirement.

The bit about higher brace height having an effect similar to more center-shot makes sense, too, but if that were all there is to it, then twisting up the brace height a bit more would have no effect on a truly centershot bow.

Found it! This might confuse you more, but it helped me. Credit Viper from www.shootingthestickbow.com

From Viper:

Yes, it's counter intuitive, but correct. The dynamic spine is determined at the instant of launch AND during the power stroke. The taller brace height, the more the limbs are stressed (higher weight) and the harder the initial push, making the arrow act weaker. Add to that, the taller brace height as the arrow disengages the string have a shallower off set, also making the arrow act weaker. That one is a tough concept, but does work, see diagram.

The amount of spine adjustment you have via brace height change is limited and assumes that your arrows are already close.

Raising the brace does in fact: increase the draw weight (less arcing of the limbs), lower the speed (both increasing the preload and increasing the bower stroke) and weaken the dynamic spine of the arrow (as above). Regarding the first two, while physical law, given the efficiency of modern bows, the changes would have to be pretty drastic to actually see.

The confusion comes in when equating the power stroke and dynamic spine. The other forces just over ride it.

Viper out.

Vipers book would settle lots of discussions if folks would read it.I have read and have most of the videos out there and highly recommend -- Shooting the Stick Bow. >>>>-------> Ken

I'm confused. I thought raising the brace height decreased the length of the power stroke. That's why a lower brace height results in higher arrow speed, as I understand it.

So, in practical application, if my bare shafts are showing stiff (impacting left of fletched for a right handed shooter), I raise the brace by twisting the string shorter and that will help make the shafts act weaker.

yes old school this is for fine tuning if shafts are just a little left it can make a difference I usually go 1/8" at a time are 3-4 twist and try.

Yep, bigdog21, that's how I've been doing it. Thanks

Sorry, but it seems like there is some contradictory information in the Viper explanation posted by JSD. Anyone else catch that?

It only seems contradictory until the lightbulb goes on.

With the higher brace, the arrow accelerates a shade more quickly but not over quite as great a distance, so the top speed attained is not (necessarily) quite equal.

But that said..... One of Larry Hatfield's flight records was set by a #50 bow short- drawn to only #35; if stroke length were as important as many believe it to be, then that could just never happen. Not unless that bow hit #35 at exactly the maximum allowable draw length for the class. But the same bow also set a record in the #50 class, so unless the max allowable DL increases with the weight class....

Makes me wish I had a shooting machine and a chronograph. If I did, I would run an experiment shooting the same arrow out of the same bow at the exact same draw length as I twisted the brace height up in 1/8 inch increments from maybe 6 inches to 8 or 9. And then of course you'd want to be able to layer on some super high speed photography so that you could calculate the changes in the rate of acceleration in addition to changes in launch velocity.

Backcountry if you look at the diagram again and think of three separate arrows with 7-8-9in brace hts it becomes clearer.maybe

I understand the diagram--that makes sense. I'm referring to the statement that "Raising the brace does in fact: ...and increasing the b(p)ower stroke)...

Guys -

This is really cool, I don't even have to post any more!!!

Happy Easter, if you're celebrating!

BTW -there were a couple of typos in that quote:

Raising the brace does in fact: increase the draw weight (MORE arcing of the limbs), lower the speed (both increasing the preload and increasing the POWER stroke) and weakenS the dynamic spine of the arrow (as above). Regarding the first two, while physical law, given the efficiency of modern bows, the changes would have to be pretty drastic to actually see.

Viper out.

Viper, please explain how raising the brace height results in increased power stroke. I understand the rest of it.

That's looking like a typo.

At any given draw length, raising BH reduces the length of the power stroke, but the impact on velocity is tempered by a slight increase in peak draw weight.

If you shorten the draw length in order to hit a specific peak weight, then you would definitely see a reduction in velocity because you're just giving the bow less to work with from the get-go...

Guys -

Sorry, typo city, lower br4ace height increases power stroke.

Viper out.

That's not a typo, but thanks for the clarification!

I once adjusted brace heights in small increments but I gave it up for Lent.

DDave

GF, The second part of your last post is pretty obvious. But what some may not realize is how the shorter draw results in the arrow reacting much stiffer despite the decreased draw weight.

Or I should have said, as a result of the decreased draw weight.

Shorter draw = stiffer DESPITE reduced draw weight?

That part seems stupid-obvious, too!

Yup. TYPO.

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