
The Archer's Paradox in Slow Motion [video] - ColinWright
https://www.patreon.com/creation?hid=2518042
======
inetsee
There's a scene in "Brave" (the animated movie) where you see Merida fire an
arrow. The scene is rendered in slow motion and you can see the arrow flex as
it leaves the bow. I knew that arrows flex as they are being fired, but this
was the first time I had seen it in slow motion. Comparing what I saw in the
movie with this video suggests to me that the animators did a very good job of
getting this detail right.

~~~
Laremere
That scene is impressively accurate in ways few people will notice: In
addition to the awesome slow motion, there are three boys who shoot before
Merida starts her shooting. The first two miss horribly, and the third one
gets a bull's eye on the sheer chance that he was startled as he was loosing
the arrow. What's interesting is that all three have different types of bad
form seen in real life, and they miss (or hit) in the way someone who has that
bad form would.

Source / Much more info: [http://archive.wired.com/geekdad/2012/02/new-brave-
trailer-g...](http://archive.wired.com/geekdad/2012/02/new-brave-trailer-gets-
it-right/)

~~~
geon
In the promo pics for the Avengers movie, Hawkeye was wearing _double_ arm
guards. As I understand it, they are only worn by n00bs who haven't learned to
rotate their elbow to the right instead of down. (Try it. You will see what I
mean.)

[http://www.blastr.com/sites/blastr/files/HawkeyeRenner1.jpg](http://www.blastr.com/sites/blastr/files/HawkeyeRenner1.jpg)

~~~
2muchcoffeeman
It's virtually impossible to not hit your forearm assuming you are doing
everything correctly. If you look at all the high level recurve comps,
everyone has an an arm gaurd. The same is true for chest protectors.

Google videos of the World Champs or Oylmpics and you'll see what I mean.

Even if this were not the case, why risk it? You don't want to get hit by a
bow string on a 44lb bow in the middle of a comp.

~~~
Gibbon1
When I was shooting bows, if you did things properly, you wouldn't hit your
forearm. The problem is if you blow chow and don't notch the arrow properly.
Or the notch blows out. Or the arrow shatters when you let loose. Then the
string will hit your arm. I got hit once with a 35lb bow. I don't want to get
bit by a 60-70 lb bow string nohow no way.

~~~
2muchcoffeeman
The angle between your arrow and bow arm may have been too high.

The strongest position is when your arms and shoulders form a straight line
(with your shoulders low). So the closer to parallel the line of the arrow is
to this, the easier it is to hold.

Now, technically you are correct. If your release is perfectly clean there
should be no problem. But in reality, there will be some degree of 'plucking'
going on. Your fingers can't open fast enough. So the string actually vibrates
a bit from side to side. I have seen some weird follow throughs that avoid
this problem.

There are very few top recurve archers that shoot without a guard.

------
muaddirac
Wouldn't you want your arrow to wobble so that it has a node right at the tip?
The archer they interview says he that he times the wobble to be able to hit
an aspirin, but in the slow motion video at the end, you can see that while
the arrow shaft wobbles a lot, the tip of the arrow remains relatively true.

~~~
donovanr
That would be ideal. Unfortunately the boundary conditions are wrong. Since
each end of the arrow is free, you get anti-nodes at the ends, just like in
open air columns:

[http://ks.kumu.net/Units/Waves/Sound/WebPages/Content_Harmon...](http://ks.kumu.net/Units/Waves/Sound/WebPages/Content_Harmonics.html)

and nodes from the second harmonic (which dominate the motion) at about a
quarter of the length in from the ends.

There is some black magic/hard engineering that goes into matching arrow
stiffness and length against tip weight and bow strength to produce optimally
timed and placed vibrations, but I've never dug deeply into it.

~~~
chongli
_and nodes from the second harmonic (which dominate the motion) at about a
quarter of the length in from the ends_

Ahhh, so the master archer (such as the guy we see in the video) likely knows
where these nodes are and can compensate his aim for that?

~~~
2muchcoffeeman
Not likely. The flex of an arrow is probably not quite symmetrical due to the
weight of the point. As mentioned, the point wobbles less than the nock end.
You can do things adjust the flexing.

Modern recurve archers generally spend time "tuning" their setup. You can
change arrow stiffness (spine), point weight (heavier gives a "softer" arrow,
lighter gives a "stiffer" arrow), plunger offset and plunger spring stiffness.
Arrow length is generally fixed if you are using a clicker.

There's also some leeway with poundage. You can screw the limb bolts in or out
to increase or decrease the poundage. And if you have money, buy X10s or ACEs.
They have barreled shafts and in my experience are easier to tune.

Barebow archers (like the guy in the video) have far fewer variables and I
think they just measure shafts to get the right tune. I've seen some go
through a lot of shafts to get usable arrows.

~~~
kbenson
He very specifically tests all his arrows for how much they flex, and if it's
outside his tolerance, he doesn't use it (as explained in the video). In this
way, he is able to normalize the deflection of the arrows he uses, and
correctly predict the deflection offset.

------
spydum
i have been an avid watcher of Destin's material, and my girls (3 & 6) love to
watch as well. if you haven't checked out his other stuff, it is pretty much
all excellent and enlightening (its not ALL high speed magic -- for example he
has a bit about inverted bicycle which is really fascinating)

~~~
hoopd
The backwards bicycle one is awesome because he actually spent 8 months
learning to ride the ridiculous thing, and then filmed himself trying to ride
a regular bike: www.youtube.com/watch?v=MFzDaBzBlL0

~~~
mutagen
Yeah that backwards bicycle episode is worth watching.

------
yuvadam
Here's the direct YouTube video -
[https://www.youtube.com/watch?v=O7zewtuUM_0](https://www.youtube.com/watch?v=O7zewtuUM_0)

~~~
deelowe
What's wrong with linking to patreon?

~~~
benihana
No 1080p

~~~
21echoes
i'm seeing 1080p just fine?

------
nerdy
The way the video is shot is really awesome (first-person, timely changes,
slow motion, etc)... even if he does look a bit goofy with the gopro strapped
to his head like a mining light.

~~~
comrh
He really has the Bill Nye like enthusiasm + nerdiness nailed.

~~~
nerdy
And it's contagious.

------
ridgeguy
Has anybody tried making arrows with increased damping? I searched briefly,
found nothing.

This would extinguish the flex oscillation more rapidly. I wonder if this
would affect arrow performance one way or the other.

With carbon arrows, you might do it by using a lower modulus matrix material,
which would dissipate flex energy faster than the high modulus epoxy they
likely use. The arrow flex amplitude should be determined by the carbon fiber
modulus and layup pattern. Oscillation ringdown (damping) should mostly be a
function of matrix material energy dissipation, since the carbon fiber has
very low damping.

------
SilasX
Wow. Anyone else feel like this is a classical, macro scale version of wave-
particle duality?

The arrow, despite projecting like a particle, is also a wave in how it
flexes. It goes "through" the bow's wood[1] by having just the right
wavelength for this vibration mode that its nodes point it toward the target
rather than letting the arrow project along a line tangent to the wood.

Does that analogy of the dynamic work?

[1] don't know the technical term; best I could find was "back" or "belly"

~~~
ori_b
Regarding terminology: The back of the bow is the part facing away from you;
Belly is the part facing towards you.

And regarding the particle wave duality -- not so much. The interesting part
of the particle wave duality is that the "waveicles" actually act like waves
in the ocean, spreading in all directions, interfering with each other,
diffracting and reflecting, and so on. It gets even weirder when you ask what
they are waves of: They're more or less waves of probability of finding the
particle.

I don't acutally know of a good analogy for it; I've only ever successfully
thought about it in terms of a mind game, instead of a 'real' physical
analogy.

~~~
SilasX
>Regarding terminology: The back of the bow is the part facing away from you;
Belly is the part facing towards you.

So the wood of the bow is called ...?

>And regarding the particle wave duality -- not so much. The interesting part
of the particle wave duality is that the "waveicles" actually act like waves
in the ocean, spreading in all directions, interfering with each other,
diffracting and reflecting, and so on. It gets even weirder when you ask what
they are waves of: They're more or less waves of probability of finding the
particle.

What I mean is, it's like the "weird" effects in the two-slit setup: the
wavelength and barrier locations (and direction the light is shot) determine
the locations of constructive interference. The arrow ends up going one
direction rather than others -- bypassing barriers in the process -- for
basically the same reason.

~~~
hoopd
It's a good try to connect it to the two-slit experiment but it doesn't work
for several reasons: double-slit is about a particle passing through two holes
at the same time and the waves go in the direction of the motion instead of
perpendicular to it.

You get a good consolation prize though, because it is a little like quantum
tunneling which is in the same neighborhood as the double-slit experiment:
[http://en.wikipedia.org/wiki/Quantum_tunneling](http://en.wikipedia.org/wiki/Quantum_tunneling)

In the tunneling case what's "waving" would again be (I believe) the
probability density function, but it's definitely a case of a particle using
some sort of waviness to pass through a classically impossible boundary.

------
eranation
Smarter Every Day is my favorite youtube channel. Check out the episodes he
did in collaboration with astronauts from the international space station.
[https://www.youtube.com/watch?v=KSzuiqVjJg4](https://www.youtube.com/watch?v=KSzuiqVjJg4)

------
z3t4
Level 20 archer.

