Effective Range/Max effective range

[Crystalshrimp]

#6861

Siting around the house and sipping my coffee, a thought came to mind. I’m one of quite a number of guys here that has been taken by uping my FOC. Now that I have what I’m comfortable shooting I was wondering.

Out of a 55# Bow, @ what range does a heavy arrow loose its effectiveness? Taking into consideration that I really wont shoot anything over 20 yds. We’ve seen pictures of the damage these High FOC arrows cause but out to what distance? Hypothetically, will a lighter faster arrow be most effective out to 40yds as opposed to a 800grn arrow at the same distance out of the same bow? Maybe nobody cares. This was just a thought.

[David Petersen]

#55545

Lots of variables here, like how fast your bow is. My elk setup from a 53# longbow (Shrew) currently is 791 grains with about 27% FOC. Maybe because I’ve been doing this for a few years now, but I really don’t consiciously notice having to hold high, out to 20 yards, to compensate for inflated trajectory arc. Beyond that it’s a different story. But no matter arrow weight I have always had to hold high beyond 20; it’s simple physics. So far as speed vs. momentum, once the arrow contacts flesh momentum always wins, no matter shot distance.

With luck, Ed Ashby and other who know way more about this stuff will chime in. For me, it’s a matter of using the most lethal possible arrow set-up first — that’s min. 650 grains total weight with as much FOC as I can manage — then limiting my range to what my bow/arrow combo can handle without consiciously having to think about compensating for trajectory. 20 yards remains as good a guideline today as it always has. IMHO

[Stephen Graf]

#56430

As usual, not much left to be said after Dave explains something. But I would add just 1 bit of fact, and 1 bit of subjective experience:

I got the feeling that maybe you thought a lighter arrow would retain more of it’s energy / momentum down range. This is not the case. A heavy arrow will leave the bow at a slower speed than a light arrow. But at some point down range, the heavy arrow will be traveling faster than a light arrow.

What this means is that at some hypothetical distance, lets say something over 75 yds, the heavy arrow will get there first!

My little bit of subjective experience is that if I use too much weight my accuracy goes way down. I attribute this to bad form (it’s all I got!).

What I think happens is that with the heavier arrows, it takes longer for the arrows to clear the bow. Additionally, the wight of the arrow becomes a significant percentage of the weight of the bow. This means that I have more time to flub the shot, and how I hold the bow is more critical.

I haven’t put numbers to it yet, but I have found that I can shoot a heavier arrow out of a heavier bow better than out of a lighter bow. even though the arrow tunes just as well and flies just as fast out of each bow.

So where I have settled out as far as heavy arrows goes is this. Shoot as heavy a FOC arrow as you can that:

-Can be shot at least 160 fps

-Doesn’t “seem” like it weights a lot compared to the bow.

Or, an even more woo woo way of saying it is that I don’t like to shoot an arrow so heavy that the bow seems to struggle to cast it.

To sum it up, I think I shoot about 12 grains/inch, and try to put as much as I can up front.

[Troy Breeding]

#56481

With Ed as my backup to confirm my findings I have been testing different weight arrows. I’ve shot everything from 550grs all the way up to 1511grs. Other than a few minor glitches all has gone well.

So far I’m down to the point of saying you will be fine with weight up to 15GPP. Even though momenium never stops growing the speed of the shaft decreases so much that IMHO you loose in trijectory (if thats the word I’m looking for).

Up to 15GPP I find that my gap doesn’t change that much. However, once I pass this point I have to correct everything and figure out a new gap. Even at close range.

Testing isn’t finalized at this point so my opinion may change. I will say that once I close in on 15gpp the noise level of my bow is just about null.

Troy

[Jason Wesbrock]

#56726

Th reality is that an arrow is lethal at distances far exceeding what most anyone would consider responsible for attempting to kill a healthy animal. As I recall, Hill once wrote about killing an elk at 185 yards with a straight-limbed longbow and a wood arrow.

[SteveMcD]

#56746

J.Wesbrock wrote: Th reality is that an arrow is lethal at distances far exceeding what most anyone would consider responsible for attempting to kill a healthy animal. As I recall, Hill once wrote about killing an elk at 185 yards with a straight-limbed longbow and a wood arrow.

I am not caught up in the EFOC thing. But I do prefer a heavy arrow, as stated simple physics.

I like your answer Jason. For me, it keeps it all in perspective.

[Troy Breeding]

#56883

MCuiksa wrote: From a pure physics standpoint I find all 3 answers to be absolutely correct….To summarize the vast amount of data present on this site regarding arrow weight, grains per pound, EFOC/UEFOC I propose this:

Increasing arrow weight does reach a point of diminishing return and may even introduce negative consequences, but FOC can increase within the practical limit of building an arrow with no negative effects.

DOC, how’s that for short and sweet? 🙂 Mike.

Mike,

Ed and I have had quite afew talks about point of diminishing return. The question still remains open in my eye, yet Ed still says there is no such thing.

If you use KE for your figures, then yes there is a point of DR. Of course we all know KE is not the way to figure anything for archery.

With Momenium, the only thing I can say is there is a point with all bows that your speed starts to reduce, or should I say becomes such that shooting seem to go into slow motion. Even though your momenium never stops growing.

Trying to find the point of where your speed starts to break off is what I’ve been work towards.

Last but not least, is trying to figure what is too slow for the average shooter. What might seem slow to me, may very well be fine with someone else.

For those that still have the need for speed, anything under 150fps might seem like they are running backwards. So far I’ve been able to adpt to any speed with enough practice. I’ve shot arrows that pushed the 200fps range as well as some that bearly broke 100fps. All did well once I set the ol’ hair covered computer to that setup.

Troy

[Ed Ashby]

#57092

Well, that’s not exactly what I said, Troy. I did say that the arrow continues to absorb more of the bow’s energy as the arrow gets heavier. At least up to 4000 grains or so. A chronograph proves that. As the arrow weight increases at some point there is a marked decrease in the RATE of energy gain. A chronograph will show you where this point is for a given bow. This is the point of peak efficiency for arrow force from that given bow.

In the testing I did I found that for most self-wood bows the point where this abrupt decrease in the rate of gain in arrow energy is right around 10 grains of arrow weight per pound of bow draw force. I suspect that this was the origin of the “10 grains of arrow weight per pound of the bow’s draw force” axiom comes from. Not that they had chronographs back then, but they just noticed that they were not getting much gain in arrow force above that ratio. With the high-tech hybrid bows I find the point where the abrupt decrease in the rate of arrow energy gain occurs at 15 to 16 grains per pound of draw force. The arrow continues to gain arrow force from the bow as arrow weight is increased beyond this point, but the RATE of energy gain decreases.

Ed

[Troy Breeding]

#57522

Ed,

Do you have a formula or way of figuring rate of energy gain and loss?

I’ve chronoed several different weight arrows. I did a graph with speed numbers as I increased arrow weight as well as one with momenium rates.

With speed numbers the rate of decrease held fairly steady until I reached the 14-15 GPP. At that point the numbers seem to level off alittle then afterwards as I increased arrow weight the decrease in speed fell again.

Same results with momenium, only instead of the numbers decreasing it was in the gain column.

Troy

[David Coulter]

#57573

Question for you two mathematicians. I wonder about the question of how slow you can launch an arrow and still have it be effective. At a certain point the arrow just won’t get there. If you shoot an arrow at a distance you have to increase the arch to get it there. As long as the blades are sharp and the arrow has sufficient mass it seems it should work. Nobody wants to stand under an arrow falling out of the sky, even one that’s falling only with the force of its own weight. dwc

[Troy Breeding]

#57632

dwcphoto wrote: Question for you two mathematicians. I wonder about the question of how slow you can launch an arrow and still have it be effective. At a certain point the arrow just won’t get there. If you shoot an arrow at a distance you have to increase the arch to get it there. As long as the blades are sharp and the arrow has sufficient mass it seems it should work. Nobody wants to stand under an arrow falling out of the sky, even one that’s falling only with the force of its own weight. dwc

David,

What you are asking sounds about like the question I’ve been trying to figure out for some time now. I’ve tried to work it out by combining speed and weight. So far figuring momenium doesn’t seem to be answering the question.

I thinks Eds statement about gain and loss in energy may be the area I have to work on.

Troy

[Stephen Graf]

#57749

I scratching my head wondering what you two are trying to get at. I fear you are trying to over-complicate things. But in an effort to help out, as I am always eager to do 🙄 , here are some handy observations:

First, our esteemed teacher Mr. Newton observed and then proved that all objects fall at the same rate, regardless of mass (ignoring air resistance). He proved this by dropping a big ball and a small ball off the preverbal tower. People were amazed to see both balls hit the ground at the same time, as Mr. Newton predicted they would.

It is a short distance from that first observation to the following equation : Range = Velocity Squared / Gravitational constant * sin (2 theta). As you will note, there is no mass involved in this equation.

You will also notice that if theta is 45 deg, then 2*theta is 90 deg, which means sin (2 theta) = 1. Which is as great as the value of sin ever gets. Thus, the maximum range an object can be cast is achieved at an angle of 45 deg. And the faster the initial velocity, the farther it will go, regardless of weight.

[Troy Breeding]

#57759

Ahhhhh,,,, say what?????

That sound so complacated it can’t be right…:shock:

Besides,, I lost me after sin…

What I’m trying to figure out is,,,, when is certain amount of weight going to move so slow that any futher addition of weight would be a loss in productivity.

In other words,,, where does the energy start to back off?

Troy

[Ed Ashby]

#57814

Troy, the method I use is to make a graph showing arrow weight along the X-Axis and the percent of gain in arrow ‘force’, per grain of increase in arrow weight, along the Y-Axis. In this application, for ‘force’ you can use either arrow KE or arrow Momentum. I did both KE and Momentum, and either works. If you want to look at both you can either do separate graphs or use a double Y-Axis, to show both on one graph. Your lightest arrow will give you your base point for calculating the percent of gain in arrow force per grain of increase in arrow weight. Plot the graph and you will see the point where the percent of gain abruptly decreases. I enter my data into a spread sheet and let the spreadsheet plot the graph. This will show you the arrow weight for maximum efficiency of transfer of the bow’s stored force to the arrow. It won’t show you the ‘maximum effective range’ of the arrow though.

Maximum effective range implies some subjective/variable components, such as the design of the arrow and how well the archer is able to compensate for heavier arrow’s more arching trajectory; a result of its lower initial velocity. As Steve points out, if you drop a light arrow and a heavy arrow at the same instant both will fall to the ground at the exact same instant. This, however, is not our situation. Fired from the same bow a heavier arrow will absorb more of the bow’s stored energy but, because if its higher mass, it will depart at a lower velocity. On the opposite side of this equation, all else being equal with the two arrow’s external dimensions, the heavier arrow retains more of its velocity and momentum as it travels downrange. In other words the heavier arrow retains what velocity it does have longer than does the lighter arrow (the rate of velocity loss is less for the heavier arrow) and it sheds its Momentum more slowly than does the light arrow.

As far as at what range the arrow will still be effective, that’s a function of the arrow design and the arrow’s Momentum at impact. The design point should be self-evident. Because the mass (weight) of the arrow does not diminish the contribution that the arrow’s mass makes to the arrow’s Momentum is more important than the contribution the arrow’s velocity makes to the arrow’s Momentum. In other words, at an equal level of Momentum the heavier arrow will generate a longer Moment of Force; at impact it will ‘push forward’ longer than would the lighter arrow. Thus, with all else equal in arrow design, the heavier arrow would be ‘more lethal’ than the lighter arrow. If the velocity difference is significant the lighter arrow may travel farther, but at any range the heavier arrow is capable of reaching it will impact with more force than the lighter arrow can deliver at that range. (I must remind here that, by definition, Momentum is the measure of ‘force’; Kinetic Energy measures the energy of a body in motion, but not its forward ‘thrust’.)

Let it just be said that a well designed heavy arrow is lethal against soft targets to the full range of their flight. As for hunting effectiveness as a function of the arrow’s weight and velocity I’ll refer you to the article, Papua New Guinea’s Bows and Arrows (here’s the link: https://www.tradbow.com/members/310.cfm). Look carefully at the chart showing the weight and FOC of the heaviest arrow in the ‘contemporary arrows’ chart. Now look at the photo of my friend with his Rusa deer shot on the open floodplains. The arrows shown in the ‘contemporary arrow’s’ chart represents all the big game arrows he has. That Rusa deer was shot at a bit over 25 yards. The arrow he chose for his first (and only) shot was the heaviest one in his selection. It weighs 3953 grains, with a FOC of 42.6%. When I asked him why he chose that arrow his reply was, “It works best”. I’m sure the velocity was well below 100 fps. It worked very well indeed! Kinda makes me wonder when I hear folks say a 700, 800 or 900 grain arrow is “too heavy to hunt with”.

Ed

[David Coulter]

#57928

Steve,

I like your second sentence. Maybe, but interesting. This discussion reminds me of a trip I took to Mexico City trying to chase down a job. I found that I knew enough Spanish to ask questions, but didn’t know enough Spanish to understand the answers.

I do enjoy the discussions. dwc

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