Tag Archives: Theory

Arrow Sense and Nonsense

QandA logoI got this question from a fairly new archer in Portugal:

When I was watching some archery videos I noticed that some archers in indoor tournaments use X7 aluminum arrows with at least 4˝ feathers and others use Easton X10 arrows; that’s just a matter of preference, right? But usually aluminium arrows are better for 18 meters and carbon/aluminium arrows are the best for longer distances, isn’t that so?

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It is wonderful that we now have a video storehouse for archers to browse through. (Thank you, YouTube!) And, at the same time, I have to warn you about what you see. Just because people do something doesn’t mean it is the right thing to do, it just means (usually) somebody was successful doing it.

Please realize that there is a lot of copying amongst archers. Less successful archers copy the behaviors of more successful archers. I consider this to being due in part to our evolution (Monkey see, monkey do.). There is a story that at the Las Vegas Indoor tournament a quite successful archer was dealing with a bow hand injury and so wore a glove on his bow hand. The next year, quite a number of archers showed up with gloved bow hands! (There is no advantage to using a glove other than keeping your hand warm (Vegas is hot indoors) but there are potential disadvantages from doing so.)

The use of “fat” arrows indoors was caused by the more demanding competitions of compound archers. Since arrows that barely touch the line of a higher scoring ring get that score, then having large diameter (aka “fatter”) arrows should help. Arrows that might have missed touching that higher scoring ring. Whether this applies to other than compound archers remains to be proven, but many a Olympic Recurve archer trades in his/her X10s for 2012 aluminums (a popular shaft of about the right spine) when shooting indoors.

I was “taught” that (by watching what others did and then copying) but, being an experimental scientist, on a couple of occasions I used a set of “thin” aluminum-carbon arrows to shoot an indoor NFAA 300 Round (60 arrows at 20 yards, 5-4-3-2-1 scoring). I then took a small piece of large diameter shafting and placed it over any hole that looked very close to touching the next ring and I found out that “fat shafts” are worth about a maximum of 1-2 points per round. If you are in a position to be needing those 1-2 points to win, then maybe it is a good idea.dead center arrow

The whole idea of using 4-5˝ feathers on indoor arrows is another “monkey see” phenomenon. The argument goes that indoors, with the distance being so short, “steerage” is more important than arrow speed. (Feathers/vanes cause the arrows to fly straighter by actually slowing them down through aerodynamic drag.) So, they took the idea from bow hunters to use large feathers as they were reputed to supply more steerage. Unfortunately this is another example of trickle down misinformation. Hunters used 4-5˝ feathers when the only thing available was feathers. Since they had arrows with heavier points (with the blades necessary for bow hunting) they felt the large vanes helped them “steer” the arrows better. Well, 4-5˝ feathers do steer arrows better than 2˝ feathers, but feathers also have a neat trick. When the arrow is first shot, feathers “lay down” and give less drag by creating much less surface area (feathers are made of individual pieces called barbs that “hook” together which is why you can separate them in so many places, these barbs slide against one another resulting in a very small feather during arrow launch). Arrows with feathers are therefore faster than arrows with equal sized plastic vanes because of this “lay down” phenomenon. In other words, feathers offer less steerage than vanes do over the first 220-40 meters or so. So archers desiring more steerage should use 4-5˝ vanes, not feathers.

So, I found myself shooting large diameter aluminum arrows with 4˝ feathers indoors because … because all of the other kids were doing it. Do you know what I was shooting when I shot my one and only 300/300 round (with 42X)? I was shooting small diameter aluminum-carbon shafts with 2˝ Flex-Fletch vanes.

The collective wisdom of archery is a mishmash of ideas from different eras and different styles passed around uncritically. I recommend that you always try to think things through and ask a lot of questions (even if they seem to be “dumb” questions). If something doesn’t make sense, there are probably good reasons why.

 

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Marketing on a Myth

I was reading a website’s marketing piece for yet another mechanical broadhead design. The line that caught my eye was “… allows the <brand name of broadhead> to maintain a minimal amount of blade exposure reducing the wind planning (sic) effect insuring better accuracy at a distance and (than?) a comparable field point shot.”

All mechanical broadheads are designed around this central bit of dogma. There’s only one problem with it: the “wind planing effect” is bogus. As the “wind planing effect” story goes the blades of an old model broadhead (see photo) act like airplane wings and cause the arrow to “fly” off line.

An "old style" two blade broadhead (still available)

An “old style” two blade broadhead (still available)

This is very bad science. An airplane wing allows a plane to fly because a number of factors:
1. Its shape causes air to move farther around one side than the other causing the pressure there (above the wing) to be lower than on the other side (below the wing) resulting in the air pushing harder from below than above creating aerodynamic lift.
2. The wing is angled to the line of flight, more so at slower speeds than to create more lift but also more drag. When the plane gets going, the higher the speed, the lower the “angle of attack” to reduce the drag and the lift (you only need enough lift at that point to keep the plane level, not climbing even more).

So, to get this “force” attributed to broadheads, the blades (aka “wings”) would have to be curved and at an angle to the air sliding by them. In fact they are flat, that is “not curved,” and in line with the shaft of the arrow creating no lift whatsoever. Not only that but there are two or three of these wings spaced equally around the point either cancelling each other out or accentuating one another. If there were actual lift created (there is not) it would be at a right angle to blade and hence a right angle to the shaft and since it would be off axis, the effect would be to spin the arrow shaft around the shaft (faster or slower depending on whether they are working with or against the arrow’s fletching), which is considered to be a good thing.

A mechanical broadhead cocked (below) and deployed (above)

A mechanical broadhead cocked (below) and deployed (above)

So, where did the idea of the “wind planing effect” come from?

I have found references to this effect that go back to the early 1970s and I suspect they go back even farther. But I suspect it came about when people had the opportunity to compare the same arrows with different points, so possibly when screw-in points were invented. Arrows with a screwed in target or field points would impact in different places than a screwed in broadhead of the same weight. People immediately wondered “why?” and the wind planing effect story was invented to explain the problem.

So what was the real reason the two arrows hit in different places?

My guess is that a number of things could be the cause. First, broadheads are quite longer than target or field points. If they were not perfectly straight, when screwed on a shaft you would have the equivalent of a bent arrow and so it would not hit in the same place. Second, those considerable longer broadheads create a longer arrow with a different weight distribution (a different “front-of-center” or FOC balance point). That would cause the arrows to fly differently, too.

Of course, there are dozens and dozens (and dozens) of mechanical broadheads being sold in today’s market. All of the marketing for which is, well, bogus. So bowhunters are buying into more complicated and more expensive broadheads (in which more things can go wrong, such as the cutting blades not deploying or parts falling off before use making them unusable) for no good reason.

Can you see now why I ask all of my coach-trainees and all of my archers to think through everything and ask a lot of questions?

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Pushers and Pullers and Pullers and Pushers

More letters are coming in; this is good. If you have a question, send it to me at steve@archeryfocus.com. The most recent question is:

Awhile back I was reading Rick McKinney’s book (The Simple Art of Winning Highly Recommended! Steve) and he mentioned that the shot execution is a 50/50 effort between pulling and pushing, but he tended to focus on the pushing. This sort of reminds me of the pushing technique that the Koreans and many of the European countries seem to be teaching (see The Heretic Archer by Vittorio and Michele Frangilli, 2005). What are you thoughts of taking focus off the pulling effort and placing it on the pushing effort?SAW

Also, I have experimented with the closed stance, but I really haven’t noticed a big difference yet. Maybe it’s just one of those things that needs an adjustment period.

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Regarding Pushing and Pulling This is mostly psychological. Physically, if you are pulling a 40# bow, you will measure a 40# push and a 40# pull! Think about pulling on both ends of a rope or a piece of pipe instead of a bow. If the push were at all different from the pull, you would have imbalanced forces and the rope/bow would move. So, if the bow (itself) isn’t moving at full draw (and it isn’t; you are still) then the push = the pull. This is where the 50:50 description comes from, but physically it is really 100:100, that is the “push” is 100% of the “pull” and vice-versa.

In essence there is no push and no pull. (Yes, Grasshopper, and there is no spoon.) The force we feel as a “push” is really the resistance of our bow arm to being compressed. (Think about it. If you extend your arm fully to the side, how are you to “push?” When you want to push something, you use a bent arm and straighten it, or you lean into a straight arm. You do neither of these in an archery shot.) The “pull” we feel is not a pull per se but a rotating of our upper arm around the socket in the draw side scapula. The muscles in our back are working to pull the draw scapula closer to the spine (and the draw scapula is connected to the upper arm). So, we do not feel back tension (physically) but back compression, in that the muscles feel tightly bunched up. The tension referred to is “muscle tension,” not physical tension.

So, if psychologically we think of our arm as pushing, we are a “pusher.” If we think of our draw arm as pulling, we are a “puller.” What is actually needed is a focus on keeping the bow arm in proper conformation (without allowing it to be pulled back or bow shoulder raised, so “extended” is the word used) while at the same time being focused on our draw side rotation (some archers focus on the muscle tension in their back, other archers focus on moving their draw elbow in its arc—both of which require muscle activity in the back, they are just focal points).

THA Cover (small)It is at this point in the shot cycle that an archer’s attention gets divided (and only at this time): part of our focus is on aiming and part on completing the physical requirements for the shot. If, while you are aiming, you are also focused on keeping your bow arm extended, you are a “pusher.” If you are aiming and focused on your muscle tension in your back or on your draw elbow, you are a “puller.” Nobody I know is capable of splitting their focus into three parts: bow arm, draw side, and aiming, so one of those has to be treated with “set it and forget it” (and it ain’t going to be aiming). Either the bow arm configuration is set and then left to its own devices (by “pullers”) or the draw side/tension is so treated (by “pushers”). Neither approach is superior, but you may prefer one to the other; use that one, if so.

Re the Closed Stance You need to have somebody check your alignment (looking for the Archer’s Triangle). Often one’s “line” is much better with a closed stance (as it puts the shoulders into their full draw position with no fighting per se) than with an open stance. If so, shooting with a closed stance and good line, you can get acclimated and accustomed to shooting “in line” and then you can experiment with different stances later, all the while maintain your good line. Having “good line” is one of the most necessary aspects of shooting form to achieve good results; it is far more important and any stance. If your line is no better with a closed stance (and still not “good”), you need to look to potential flaws in your hip or shoulder positions.

Hope this helps! Let me know.

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Q&A How does arrow length affect the point on distance? Will a longer arrow increase the point on?

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I got this question from “Ken” on the blog.

First Some Background
The “point-on-target distance” or “point on” for a barebow setup is an indicator of the power or “cast” of the bow-arrow combination. Powerful bows have longer point ons than weaker ones and heavier arrows result in closer point ons than lighter ones. Beware! There are a whole host of other factors that are involved. I give you the example of a compound archer who cranked his draw weight down by one whole turn on each limb and got an increase in point on! The reason was that the adjustment in draw weight, while making a less powerful bow, created a better spine match with the arrow, resulting in better energy transfer from bow to arrow (a greater % of the energy stored in the bow ended up in the arrow), offsetting the lower draw weight to create more cast and a farther point on.

So, point-on-target distance is determined by a great many factors: the question is about the effect of arrow length. Any such discussion has to occur assuming all of the other factors stay roughly the same, otherwise we will end up talking about those effects and not just the length of the arrows, so point weight, fletching, spine match with bow, all must be ceteris paribus. (How’s that for classy language? So, you don’t have to look it up, it means “all other things being equal or the same.”)

So, Now the Question
How does arrow length affect the point on distance? Will a longer arrow increase the point on?

Actually the reverse is true; a longer arrow will decrease point on. Here’s the reasoning: since the arrow is slanting upward (arrow nock is near the anchor point which is below the eye line, arrow point is on the eye line, (also called the line of sight), the longer the arrow, the lower one must hold the bow to get the arrow point onto the sight line (the eye is looking at the point of aim). Think about being at full draw with a normal arrow, lined up with a point of aim (POA), and then magically the arrow grows three inches. Since the arrow is slanted upward, the point goes outward from the bow and upward above the line of sight (since the behavior of the arrow is being held constant so it will fly in the same arc as the shorter one, you must lower the bow to bring the point down onto the line of sight. If the bow is held at a lower angle, the distance of trravel is reduced.

So, for an indoor setup, in which most bows have too much cast, one is left with either a POA on the floor or a large crawl if stringwalking. Many archers switch to a much longer, much stiffer arrow (about one spine group stiffer per extra inch of arrow). This gives a shootable arrow (with roughly the same dynamic spine as the shorter one) with a much higher POA (hopefully on the target or very near it) or smaller crawl. Some are so adept at this that they can create a point on equal to the target distance.

Outdoors the situation is the reverse; there is no such thing as “too much cast/bow power.” Since the targets mostly are farther away, you want a shorter arrow, correctly spined, and as light as possible to give a POA down near the target and not up in the trees.

The Short Answer
So, longer arrow, closer point on; shorter arrow, farther point on.

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A Little Bow Geometry

Everything about archery consists of tradeoffs, starting with the design of bows.

Recurve Bow Geometry Diagram
Consider the recurve bow at brace in the figure. The horizontal centerline of the bow is midway between the arrow rest hole and the pivot point of the grip. The nocking point is about one half inch above the level of the arrow rest, so that arrow (depending on size) is attached to the string about 3/8˝ above level and an additional inch or so above the previously mentioned centerline. All of these are examples of many of the various tradeoffs necessary to design a bow.

Basically this results in the archer’s fingers (plus tab), being 2-2.5˝ high, being practically centered on the bowstring (see fingers in diagram in relation to bows centerline (CL) which is also the string’s centerline). The bow hand is on the bottom half of the bow, creating what is called a “tiller” problem. (The word tiller means the same as the word tiller associated with sail boats; it means a thing “to steer.” By holding the bow asymetrically, that is on the bottom half, we in effect have made the top limb longer. Many people adjust for this by turning the limb screws to create a slightly weaker limb on top than bottom. (In the old days, they actually sanded one limb more than the other to make it weaker.) Others address this issue by adjusting the nocking point location, leaving the limb bolts alone. If you move the nocking point up, you are decreasing the leverage you have on the top limb, making it effectively stronger, etc. and apparently only small adjustments in nocking point location are necessary to adjust for the problem that comes from holding the bow on its bottom half.

The same issues come up whether you shoot a longbow, recurve bow, or compound bow. The simplest approach is to set the tiller at “even” and then adjust the nocking point location while tuning (bare shaft test). Tiller is determined by measuring from the top or bottom of the riser to the bowstring (at a right angle), then “tiller = top tiller measurement – bottom tiller measurement.” Typical recurve settings are +1/8˝ to +1/4˝ (string closer to bottom limb than top).

This situation has benefits, though, in that as the bow is drawn, a torque is created hinging on the bow shoulder that helps to raise the bow. Basically the draw is part “back” and part “up” (using the bow arm as a boom.

Full Draw Vectors

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