not having a chrono or access to one that I can test this for myself I was wondering what effect a full inch of brace height would have on speed. I understand the higher brace height typically equates to quiet shot but what kind of speed loss do you think one would experience by raising the brace height by one inch?
This would be a modern recurve bow 54#'s at 29 and shooting a 540 grain carbon arrow. The brace is currently set at 7 inches. What kind of speed loss do you think I would see moving up to 8 inches of brace? I always wondered about this and thought this would be a great place to ask....
I'll take a guess and this is ONLY a guess.
Since drawing an inch further will cause a velocity gain of approximately 10 fps, I'll venture a GUESS that raising the BH an inch would cause a loss of something less than that, say 5 fps.
Somebody with a crono weigh in here and tell me I'm full of it.
I tune the brace height for quietness. My arrow just pokes along while I eat a candy bar and drink a cherry coke.Then it hit's the (insert animal here) and kills it graveyard dead. :campfire:
I don't think the difference would worry me. Recurves tend to like a bit more brace height. Some of the old Bears braced at 10 inches! My Kota Killum shoots way better at 8 1/2 inches than it does at 7 1/2, and it is whisper quiet at 8 1/2.
Twist up the string to find the sweet spot. What you lose in speed you will gain in quiet and probably get better arrow flight to boot...I did.
You will loose way to much speed like that, keep it one inch lower, and maintain that speed.
You've got two things going on that sort of offset each other. With the higher brace height, you have a higher peak weight at full draw. With the lower brace height, you have the arrow being pushed by the string a little longer. Within the normal range of brace heights, my understanding is that you will get a little more speed out of a lower brace height. You also will get a little more noise and vibration. But you would really need a chrono to tell, and I'll bet the difference, within the recommended max and min brace heights, which is probably less than an inch, would be only a couple of fps. The general rule is to reduce brace height until you start getting noise and vibration.
Doesn't matter how fast you shoot if your quarry jumps the string.
To me a bow is tuned when it is at its quietest without silencers. This means to me that the energy is transfered to the arrow, and not to the limbs in the way of vibration, string slap, and hand shock. When a bow shoots smooth and quiet all the energy is going down range.
Just my 2cents.
I recently spent an entire afternoon with a chronograph pursuing answers to just this sort of question. I found adding an inch of power stroke on the draw length often yielded a whopping 8-10 fps increase. Pretty substantial. Lowering the brace an entire inch had virtually no effect on speed. Sometimes none. This surprised me. I concluded brace height belonged in the tuning shot/feel category as it generally has been all along. As I thought about it more, I realized I was looking at the difference an inch made relative to where it was...adding an inch draw at peak pull was adding an inch where all the power was. Adding an inch by lowering brace was only adding power stroke at the end, where the bow was already pretty much spent and there was little or no gain as a result. Then it made more sense to me.
I also learned aluminums of equal weight were a tad faster off the bow than woodies, and a single brass nock point can cost as much as 2-3 fps, among other things.
I have a long bow I tested, tillered from a Hill blank to match a Schulz limb angle at full draw. At 63/8'' I got 178, at 71/2'' I got 166.
Slow bow. what you said depends entirely on the bow design. If the limbs are prestressed right then you add considerable speed by dropping the brace height. I build my bows for low brace height to get max string time for better performance. If the bow is not designed for high brace weight then you gain virtually nothing. The only way to answer this question is to chrono the bow , take it up an inch and Chrono it again. I would say that you will lose about 8 fps. But that is just a guess.
Lower brace= faster speed =less forgiveing and loader.Higher brace = less speed = more forgiveing and less noise.bd
Sixby I can see where design would have a LOT to do with it...that's stuff for you smart guys though! :D
A quick recall of any force-draw curve will confirm what SlowBowinMo has found in his testing. Force draw curves are plotted in 1 inch draw increments. If you look at the area under the curve out at the end of the curve, say at the 29 inch point. Look at the area taken up under the curve by that vertical span over the 29 inch draw point. REGARDLESS of bow design, THAT area is SUBSTANTIALLY larger than the area over the 8 inch or 7 inch draw point. Opinions and guesses aside, physics states that an inch of draw at the end of the draw cycle will have a SUSTANTIALLY greater effect on speed than an inch difference in brace height. SlowBowinMo found 8-10 fps by increasing the draw by an inch and negligible difference in changing the brace height by an inch. That passes the smell test and makes sense from a physical/mathmatical standpoint as well.
Yep. Slowbow is right. Changing the brace height doesn't change one's draw length. Any differences in speed due to brace height change (within a normal range for the bow,of course) are so small that most wouldn't notice them.
I have a gm2 that will shoot 218fps at 6.5 brace ht but it sounds like .22 when i shoot it. Set brace ht 7.5 speed is now 180fps and less noise. Plus my point of impact is about the same out to 25 yards. By the way its 50# at 28in. with gt 55/75 125 tips.
Clear
Check your chrono bud. You ain't gaining almost 40 fps by dropping an inch in brace height.
In God we trust...all others...bring data.
LOL
ok..im sort of following along here... does raising the brace height tend to make an arrow fly weaker..or does lowering the brace height...? i always assumed it would be lowering, but its looking like it is raising the height.
jacobsladder, I always assumed the same as you. I do remember reading that it was opposite though(higher brace=weaker arrow) and it had to do with "archer's paradox". Sorry, can't explain it, just relaying what I read...Mike
Accuracy first. You can cut your group size in half by finding the right brace.
For those changing BH and using a chrono, shoot at least 6 arrows after stringing the bow to seat the string fibers before you chrono the bow or the numbers will misslead you.
The best setting is not always the fastest.
Pete
Otto check my post I said I lost 38 fps . Plus the chorno is a old and I just shot one arrow to see the change.