Any way to calculate arrow speed without a chro

[Falk]

[Frenchymanny]

Fun stuff right there, but any calculation based on time to reach the target will give you an average speed for the whole distance, where a chrono will give you an instant speed, almost a "velocity at the muzzle" for a bow

F-Manny

[Dave Bulla]

F-Manny, exactly what I was thinking.

Guaranteed "Lower than ya want to see" type numbers.  Especially if doing the 20 yard and 30 yard group height difference thing.  

Not only does the arrow begin to drop the instant it leaves the bow due to gravity but it begins to slow down too.  By 20 yards, I'm sure it's lost quite a bit of speed depending on the wind resistance due to fletch, oscillations of the shaft, frontal cross section etc etc....  Measure between there and 30 yards and dang, gotta be showing a lot of slow down.  

Then try to figure out how much speed loss you have due to fletch size, improper tuning or whatever, whew!  What's the point?  I can eyeball flight and trajectory to get a good enough idea of performance in my bows to satisfy myself.

Honestly, my "Go to" method for checking performance of my bows is to shoot for max distance on a calm day.  My hunting weight arrows shot from my longbow that is 60# at 30" but pulled about 32" (Arrows 33-34" BOP) are heavy but will shoot right about 190 to 210 yards if the bow is held at about a 35-40 degree incline.  The 190 is about right for wood arrows and the 210 is for Heritage 350 carbons which are lighter than the woods.  Broadheads seem to shoot farther than field points.  Too high of a shot angle (45deg or more) cuts down distance.

I've heard many times that a self bow should shoot a hunting weight arrow about the draw weight plus 100 yards if decently tillered.  Some guys get draw plus about 120 yards.  Glass bows can get draw plus 150 or better.  

Not really a help for figuring speed as far as getting an actual number but certainly an accurate performance indicator of one bow to another (if both are equally well tuned and shooting the same grains per pound).

[Falk]

[ScouterMike]

It is quite easy to predict how fast a bow will shoot a certain weight arrow by comparing results obtained from similar designs. I built a calculator for my own amusement that will do this. It can be found at  http://www.outdoorsden.com/archery
The calculator is not directly setup for predicting velocity but it can be done by guessing the velocity until the bow efficiency calculated equals your design. I am happy to answer any questions on how to use the calculator.

[SteveB]

Bottom line is there is no simple accurate way to estimate. If you want to know, go to a shop with a chrono, use a system to ensure draw length is fairly constant, shoot a string of arrows, and average the results throwing out the extremes first.

I shoot thru one a lot in the winter to work on consistant form - goal is to not vary more then 2 fps per shot.
Steve

[Rob DiStefano]

i've had three chronos over the last 7 years, and sold each one a month or so after getting it.  every time i buy one i wonder why the heck i bought it in the first place.  what am i really trying to prove?  

truthfully, it really doesn't matter knowing the precise fps a bow can generate, all that matters is if the bow's speed works for you with different arrow weights and shooting distances.

[Mo. Huntin]

I was thinking of getting a martin recurve from an archery shop around here and I took my montana longbow and My supermag 48 to see how it compared.  All the bows were 45 pounds at 28 inches and I am not kidding they were all very close with the same arrow.  they were also slower than I had hoped but whatever. Supermag was 10 feet faster, the other 2 were the exact same.