Arrow Question for Math Whizes

[Cherokeeson]

Yesterday I was wanting to experiment so here is the set-up. Shooting a GT Laser IV with total weight of 506gr & A Firebolt with a Total Weight of 403gr. (Both are using 125 grain FP's and calculated into the total weight) At 20 yards all are within 0.5" - 1.5" of each other. (trying to avoid them costly robin hoods) At 40 Yards the GT's are still within the 0.5" - 1.5" of each other but the Firebolt is shooting high consistently from 3" up to a wild 4.5" . Now I figure the later 4.5" is operator / shooter error, but with a arrow weight of 103 gr less than another arrow cause this flight / POI difference. I am considering switching to a lighter shaft but maybe not. Solutions /Suggestions Anyone?

[_woods]

100 grains will change your POI. (Depending on the draw weight of your bow that could be a lot or a little) The further the distance, the more noticeable it will be.

In my traditional archery days I developed a taste for heavy arrows with a lot of weight up front. That seemed to translate well to the Excal, so I've stuck with it.

Experiment with your setup a bit and see what works best for you! The flat(er) trajectory of a lightweight bolt sure does sound tempting, but I could never get them to be as accurate as the heavies.

[Cherokeeson]

100 grains will change your POI. (Depending on the draw weight of your bow that could be a lot or a little) The further the distance, the more noticeable it will be.

In my traditional archery days I developed a taste for heavy arrows with a lot of weight up front. That seemed to translate well to the Excal, so I've stuck with it.

Experiment with your setup a bit and see what works best for you! The flat(er) trajectory of a lightweight bolt sure does sound tempting, but I could never get them to be as accurate as the heavies.

This was using a Axiom, which is 175 lbs DW. Dyna Flite Flemish String.

[chicotrout]

All right, here is the nerdy answer

Two major factors, weight and resistance, are affecting the trajectory of the arrow but, not for the reasons one might think. The reason why one arrow is hitting higher than the other is speed. If you chronographed your Firebolt you would see that it is traveling at a higher rate of speed than your GT Laser and therefore hitting higher.

Let me explain. An object's rate of descent depends only on how far the object has fallen. So two objects dropped at the same time from the same height will reach the ground at the same time. Enter the fly in the ointment: resistance. If you dropped a feather and a lead ball from the same height at the same time which would land first? The lead ball right? Correct but, only because of the feather's superior resistance to air. If you conducted the same experiment in a vacuum, the "Law of Conservation of Energy" dictates that both land at the same time...see for yourself on youtube http://www.youtube.com/watch?v=_XJcZ-KoL9o

Now, let's look at speed keeping in mind what we just observed. Imagine dropping an arrow in a vacuum from a height that takes exactly one second for the arrow to drop. Now imagine shooting two arrows parallel to a flat surface in a vacuum from that same height but, one traveling at 300 fps and the other traveling at 400 fps. If you shot both arrows at the same time they would both drop in exactly one second but one would have traveled 300 feet and the other would have traveled 400 feet (hence the measurement feet per second fps.)

Let's get out of the vacuum now and back to the shooting range. When one fires a projectile the resulting trajectory is an asymmetric parabola. It's like a camel's hump but the back side gets steeper because the velocity of the projectile gets slower as it travels through the air due to resistance. This parabola is why your arrow stays aloft for longer than one second and travels so far. So when you fire an arrow the arrow travels up, up, up, up, up, up, until it reaches its summit or highest point of the trajectory then it travels down, down, ground. It travels further on the way to the summit because the arrow is going faster at first. Most vanes (except Firenock's Aerovanes) stabilize the arrow by inducing drag on the arrow which slows the arrow down more and more as it travels though the air. So by the time the arrow reaches its summit it's running out of gas fast and begins a much steeper descent.

And now back to your arrows. The reason why the Firebolt hits higher than the GT Laser is because it's 20% lighter which translates to a much higher speed. The Firebolt's trajectory has a higher summit than the slower GT Laser accounting for its higher impact at 40yds.

There are many other variables involved but speed and resistance (fletching size, fletching type and method of fletching) are the main ones that you need to worry about.

And I used to ask my parents what the heck I needed to learn math for?

[JT of PA]

chicotrout,

Great easy-to-follow article. This type of information is fascinating to me, unfortunately, most of the time I get lost.

Thanks for taking the time to share your insight with us all.

[Cherokeeson]

chicotrout,

Great easy-to-follow article. This type of information is fascinating to me, unfortunately, most of the time I get lost.

Thanks for taking the time to share your insight with us all.

Cannot get the link to work. Would like to read it though. Chicotrout I shot some more today and will post results with pics once I get back in.

[gametrail]

OK now I am so confused. If you are shooting a 150 boltcutter out of a exocet which is the best set up a 2 inch vane or 4 inch vane also the firebolt or gold tip?

[chicotrout]

Cherokeeson, just copy and paste the link on your browser; it's just a short video that shows the feather and the lead ball experiment. I still have to figure out how to post an active URL. I have tried several times but it says that I can't use certain BBCodes, URL being one of them. Sorry

[chicotrout]

OK now I am so confused. If you are shooting a 150 boltcutter out of a exocet which is the best set up a 2 inch vane or 4 inch vane also the firebolt or gold tip?

The best set up is the one that does what you want it to do. For me, I would try to find the shortest vane that stabilizes the arrow and gives me good tight groups. That way I keep the arrow speed up and have a flatter trajectory.

[Cherokeeson]

Cherokeeson, just copy and paste the link on your browser; it's just a short video that shows the feather and the lead ball experiment. I still have to figure out how to post an active URL. I have tried several times but it says that I can't use certain BBCodes, URL being one of them. Sorry

Chicotrout, I cant get active to work either. "Great easy-to-follow" underlined but no clickable. Maybe pm me the url or put here.

[JT of PA]

chicotrout,

Great easy-to-follow article. This type of information is fascinating to me, unfortunately, most of the time I get lost.

Thanks for taking the time to share your insight with us all.

Cannot get the link to work. Would like to read it though. Chicotrout I shot some more today and will post results with pics once I get back in.

cherokeeson,

My fault.

I meant the underlined portion of my post to chicotrout for emphasis, however, it does look like it could be a link to an easy-to-follow article. Sorry about that.

http://www.youtube.com/watch?v=_XJcZ-KoL9o

The above link in blue is from chicotrout's original post and it is a copy/paste link. You cannot click on it to work, you have to copy it and paste it into your browser bar. (Very interesting video showing a steel ball and feather falling in a normal atmospheric condition and then falling in a vacuum.)

Thanks for starting this post. I'm learning a lot.

All the best,
John

[Cherokeeson]

OK So back to "Outdoor Lab" after reading this and watching videos. And here are the results.

Here we have a a 403 grain Firebolt (weight includes the 125gr FP) & 3 506gr GT Laser IV's (weight includes the 125gr FP) at 50 yards. Aiming Point for the Firebolt was the LOWER Black Dot & as expected the Lighter, Faster Firebolt hit High. The Aiming point for the GT Laser IV's was The UPPER Red Dot and much to my surprise they all hit low but grouped somewhat decent at that range considering the lower DW of the Axiom and Heavier Arrow.



Here we have the same arrows but at 40 yards. Aiming point for the Firebolt in was the Lower Red Dot not shown in this pic at the bottom of the target (but it is the same distance as upper Red DOT) & The Firebolt Hit (plenty) High as expected, while the GT Laser IV's aimed at the Center Smaller Black Dot Hit Right on the Aiming Point and really grouped well as shown in this pic.



Testing was stopped after this though



So while I generally take shots 40 yards or less, if I wanted to go out to 50 yards on a good clean shot with the Axiom, switching to a lighter arrow but not quite as light as the Firebolt and do some scope adjustment it would seem would be in order. But I do like them heavier Arrows.

(After thought) I wonder if this would be enough to convince the wife of my "disadvantage" of not having a Matrix?

[chicotrout]

Nice update!!! I would take either of those groups any day.

[nchunterkw]

What kind of scope are you using? Does it have an adjustable reticle like a Vari-zone?

[Cherokeeson]

What kind of scope are you using? Does it have an adjustable reticle like a Vari-zone?

Standard Excal scope that comes on the Axiom