How fast is fast?

[Nativestranger]

Originally posted by heartlandbowyer:
Charles, I think on a calm animal and a great shot it probably doesn't matter. But if I miss my spot by 3 inches or the animal flinches etc and I hit shoulder the extra kinetic would probably help my arrow through the bone and possibly through the far side which would give me a higher percentage of a good blood trail and recovery.

If I'm shooting a 550 gr arrow at 160fps ke = 31.27
If I'm shooting a 550 gr arrow at 190fps ke = 44.1

Heck I don't know maybe the KE don't matter that much but why not shoot the more efficient bow especially if the bow is a great shooter with extra speed.

Cory

I agree there. Maybe it doesn't matter much the time it takes for the arrow to get there but there's a hell lot more energy in that faster arrow. Will it matter for penetration? There's 2 schools of thought and one of them believes penetration is determined by arrow mass not speed the other believes in KE. Not going start an argument there. But just imagine scenario where a 500 grain arrow is shot out of a 25# bow vs a 50# bow at a higher speed.

[ishoot4thrills]

Originally posted by cbCrow:
I maybe blissfully ignorant and my info maybe skewed according to some but if you read my first post it contained a question/ statement that no one including 2 bowyers and quite a bit of others have not answered  : at 15yds(avg hunting/killing distance) what does it matter if your bow is 160fps or 190fps when their is only 4/100's of a second involved in difference? By the way the drops stated earlier were way off. It would take approx. 35yds distance to reach close to a full second of time. What say ye all?

I detect frustration in your post.    

Blissfully ignorant? Definitely not. Looking for answers in the wrong places? Maybe.

Umm, not meaning to offend you but.....maybe no one answered your question/statement because you're not the original starter of this thread? That's the person that people should be really concerned about answering.

Perhaps you should start a thread posting your question to the get answers you're looking for.          

[gringol]

Originally posted by cbCrow:
I maybe blissfully ignorant and my info maybe skewed according to some but if you read my first post it contained a question/ statement that no one including 2 bowyers and quite a bit of others have not answered  : at 15yds(avg hunting/killing distance) what does it matter if your bow is 160fps or 190fps when their is only 4/100's of a second involved in difference? By the way the drops stated earlier were way off. It would take approx. 35yds distance to reach close to a full second of time. What say ye all?

The answer you are looking for is, the deer doesn't care how fsdt the arrow is going.  Deer can duck the string of just about any bow, including wheel bows.  However, last I checked, deer don't buy bows nor do they shoot them.  I prefer fast bows to slow bows because they shoot flatter and are actually MORE forgiving than slow bows.  The quicker the arrow if off the bow the less time i have to mess up the shot.

Looping trajectories are harder to estimate and the more launch angle you need, the farther the arrow has to travel, so time in the air will actually be greater than the times you calculated.  The times you calculated are straight line times.  Also, arrow drop actually accelerates with time, so a slight increase in flight time corresponds to increasingly larger arrow drop.  The simplest waytto calculate it is to assume a horizontal launch angle, calculate time to a distance, then use that time to calculate arrow drop using this

H = 0.5*g*t^2

H is in feet, g = 32.15 ft per second squared, and t is time in seconds.

Do the equation yourself.  That is the real difference between 160 and 190 fps.  At 15 yds, an arrow moving horizontally at 160 fps drops 15.2".  The same arrow going 190fps drops 10.8".  The difference gets more and more pronounced with increased range.

You certainly don't have to shoot a fast bow, but a fast bow has very real advamtages over a slow one.

[LookMomNoSights]

AAAAHHHH!  Trajectory.......
Gotta love a little speed.  I have not run my favorite set up through a chrono....maybe I will when I have the chance.   I dont dwell on it.  I will take speed if I can get it in a bow, so long as the grip and draw and just overall pleasure of shooting the bow is there.   I dont obsess over speed.  I know my bow is not slow though and I reall like that.   But I have to say,   hats off to guys like Kirk... craftsman who are building these great bows to efficiently zip an arrow on the faster side of the scale....you are surely  making possetive contributions to our great sport!

[cbCrow]

gringol, heck of a job there! I admire your pluck and thank you for pointing out my error in time. This would give you a 4.4" difference which is closer to what I got instead of 7". Now I like to take this time to say that I was definitely wrong for hijacking this thread and hope that Corey and all involved will accept my apology. I had only good intentions but did it all wrong.  Chuck

[heartlandbowyer]

Chuck, no apologies needed no ones feelings got hurt. Being a relatively new bowyer I'm just trying to get everyone's thoughts so I can build the smoothest most efficient bow I can.

Cory

[**DONOTDELETE**]

i think this whole thread has been handled pretty well by both high performance fans, and others that feel more comfortable with their current set up and the trajectory it offers.

if you guys want to have some fun checking out trajectory differences. set up a piece of card board, or a frame with a large piece of butcher paper stretched across it you can move. set your card board at 10 yards in front of your target and cut a 6" hole in it.... then go back to twenty yards and shoot through the hole to hit your target..... this simulates shooting through brush or vine maple we have a lot of on the west coast..... after you get to where you have the right elivation going to hit your target perfectly through the hole, step back five yards and shoot again... you'll be amazed  at what happens.

i've done it with a shooting machine set up hitting bulls eyes, then put the paper up mid way to measure the top of the cord or arch at different yardages. i used a laser levet to measure the exact elevation of the bulls eye and the shelf of the bow... its amazing how much short distances change the height of your trajectory curve..... it's also amazing how much 20 fps makes a difference on hunting weight shafts..... fun stuff.        

.

[gringol]

That sounds like a cool experiment, kirk.

[Lee Viv]

Originally posted by duncan idaho:
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"Deer don't buy bows but hunters both buy bows and shoot them. To this day I have never had a single hunter that wanted to buy a slow bow. Never. Therefor , I will build the fastest bow I can build that is well mannered, Quiet and accurate."
God bless you all, Steve

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Quoted for absolute truth. I never seen someone posting about their pride and joy and start out by saying, "she is sold, stable, and sooooooo slow", man, what a dream bow!" Thats why all the comments that "speed doesnt matter", rings of severe hypocrisy.

In my three years working in the business for an archery company, I can honestly say that when i would receive a phone call or email concerning a particular bow, 9 out of 10 times the first question was "How fast is it?"  There are a lot of people who say speed doesn't matter...but they are the very same people asking that question in private..it seems like there is a taboo in traditional archery that shuns a person if they show an interest in speed.

[Sixby]

Aha!! Lee Viv is an honest man. That is exactly what I run into. Its almost always the first question.

The answer I love is this.   Enough

God bless, Steve

[TraditionalGuy]

I don't know if it's a taboo for traditional archers to talk about speed or a "where do you draw the line" kind of issue. I have no idea how fast my main hunting bow is, but I do know that it is faster than any of my other bows, which is why it is my main hunting bow. It matters a lot when I am shooting through trees, as Kirk says above. But at the end of the day we're still talking about traditional bows. I can't speak for every trad guy on here, but for me the day I chrono, tune, adjust, tinker or whatever to get that extra 10 fps is the day I put down the long bow and go get myself a set of wheels.

[ScouterMike]

For those wondering how much difference in trajectory a faster arrow will make for your bow, check out this calculator. If you know the numbers at one arrow weight it approximates what your bow will do at other arrow eights and calculates the trajectory of each....

  Arrow trajectory calculator

[elknutz]

That is interesting, think I need to save it.

[Hoyt]

I started shooting recurves before wheels or traditional archery.

Myself and the people I hunted and shot with wanted the newest, fastest, flattest shooting, best preforming and most modern bows and equipment available. I still do and speed is at the top of my list.. so I set my recurves up to squeeze every fps I can get out of them.

I shoot over 12 gpp arrows..but I want some zip on them.

Running my numbers through that calculator is making me like my 8.5 gpp setups even more.

[**DONOTDELETE**]

i played with that calculator a bit and it sure doesn't match the trajectory of my hunting bow...

Also ....the estimated difference in speed from 10 gpp to 9 gpp shows 12 fps. In most cases on the bows i've tested it"s closer 6 fps....  i wonder if there is a sliding scale for bows with more or less effeciency?....  

It sure is good to see all these archers who appreciate high performance coming out of the closet here.....

           

[pamike]

I think Kirk is right. Change from 9 to 10 gpp made a bigger diff in some bows - I saw 5-12 fps changes in the 10 bows I tested. No real change in noise though. But at 8gpp noise changed and speed jumped about the same. I doubt the calc has all the bows real eff curves.

[ScouterMike]

The key to the calculator is the fact that any bow will have about the same kinetic energy across different arrow weights with the KE increasing slightly as arrow weight increases. This is simple physics and careful testing will confirm. If you are not seeing similar velocity differences between arrow weights, with all due respect check your testing.

Different designs however will show a larger difference between heavier and lighter arrow KE. The more efficient the bow the less difference there will be. (Faster bows maintain KE better with lighter arrows). This explains why for example Hill style bows are "great with heavy arrows". The  real thing here is they lose efficiency quickly as arrow weight decreases because of the heavy limbs and perform poorly in comparison the lighter arrows.

When I designed the calculator I decided to not include a factor for bow design to keep it simple, so it does equal energy at all arrow weights. In the most extreme case this would only amount to about 3 fps error on an slow bow btween 8 and 12 gpp inputting at either extreme.

As far as trajectory is concerned this again is simple physics. There is a "ballistic coefficient" built in to allow for arrow velocity loss. This is averaged out and reflects traditional type arrows at traditional bow speeds. Again for simplicity and the fact that at normal ranges (out to 35 - 40 yards) there would be very little difference I fixed this value. This is also the reason the chart only goes to 40 yards. Much past that there are too many variables to be accurate and keep it simple. As an interesting note, for typical arrows used in olympic style competition at about 100 yards the arrow can actually increase in velocity slightly as it travels the last half of its flight - try building an accurate trajectory calculator for that!

This trajectory is from a zero line of sight perspective. That is the baseline and will seem accurate for instinctive shooting. If you are using sights or a consistent gap method using the arrow tip then the distance between the arrow (anchor point) and the line of sight (your eye) will effect the trajectory from that point of view. The trajectory will seem flatter as the distance between the anchor point and eye increases. Best to experiment to see how your style would effect this.

The base line trajectory in this calculator is ok. Two companies (excaliber crossbows and Nikon optics) have both consulted with me when developing their range compensating scopes. They saw the calculator of course wanted the behind the scenes details, mainly on how the arrow velocity loss was determined.

[Nativestranger]

Thanks for the explanation. Great program!

[duncan idaho]

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I started shooting recurves before wheels or traditional archery.

"Myself and the people I hunted and shot with wanted the newest, fastest, flattest shooting, best preforming and most modern bows and equipment available. I still do and speed is at the top of my list.. so I set my recurves up to squeeze every fps I can get out of them.

I shoot over 12 gpp arrows..but I want some zip on them."
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Sir,
      You got that right!