MYTHBUSTERS 5/11: "Blow Your Own Sail"

[Christopher]

Sound Effects: This is a very simple thing to test, just record the real sounds and compare them to the fake Hollywood sounds. It was so simple that it made up an astonishingly small percentage of the episode. But I always like it when they debunk movie cliches. I would've liked more explanation of how the Hollywood sound effects were made.

Oh, and I liked how, in the opening "dream sequence," when Jamie blew up Adam's car, there was a bit of the Wilhelm scream in there.

I was surprised by their interpretation of the "silencer" (suppressor) result. I didn't think that was anywhere near the movie version. It was still recognizably a "bang," and 128 decibels is hardly quiet. It's still something that would be recognizable as a gunshot. The myth of the movie silencer isn't just that it makes a gun quieter, but that it makes it so quiet you can shoot someone without people in adjacent rooms hearing anything. And that's definitely rubbish. So I think they totally missed the boat on this one.

And I wish they'd explained what the movie "silencer" sound effect really was. It sounds to me like some sort of air rifle sound or something.


Blow Your Own Sail: I expected this to be boringly straightforward, since of course we all know the classic story-problem scenario here -- the action and reaction between the sail and the fan cancel each other out and the boat goes nowhere. The first segment just confirmed that. But the second segment, when they actually got the boat to move forward, totally shocked me. I never saw that coming. I didn't even think about the idea of the wind reflecting back and generating an uncancelled thrust. It's clearly a ridiculously inefficient form of propulsion, and if you've got a powerful enough fan, you'd be better off dropping the sail and pointing the fan backward. But it does actually accomplish something. A remarkable demonstration of how theory doesn't always take all the practical realities into account. I never saw that coming.

Although I guess if I'd known more about sailing, I might've been able to anticipate it. One of the aftershow questions pointed out that real sailing is rarely done with the wind blowing straight forward into the sail. Now that I think about it, sails on boats are usually at an angle to the direction of motion. So a sail isn't just a parachute, it's a device for redirecting the thrust of wind onto a vector useful for propulsion. That's what the sail was doing here. And that makes me wonder -- would this technique possibly be more efficient if the sail were at an angle and the fan was blowing from the side? I call for a revisit!

"Our health insurance actually covers a full-body cast." Of course it does!

 

[Trekker4747]

The sound effect myth(s) were fun though I think hitting a gutted pig in the head is a bit different than hitting a complete human in the torso. The suppressed gun shots, though, were surprising since it's always been my understanding that Hollywood very much exaggerates them which they still do, but I was still surprised bu the result.

(The most blatant example of Hollywood over-exaggerating suppressed guns is in the movie "Inception" when during the opening action piece DiCaprio's character shoots various guards with a suppressed gun and the gun makes no sound whatsoever other a "clink" sound from the shell being ejected. Now, some of you may be saying "it was a dream, it doesn't have to make sense" but in the movie's own rules making things too different from reality tips off the target's subconscious something is amiss and in the same sequence DiCaprio's character catches the spent casing with his hand. So why would he create a dream gun that needed a suppressor to be totally silent (as opposed to silent on its own) and also needed to eject a spent shell?)

The blow your own sail myth was also surprising but as I think Grant explains doesn't completely contradict Newtonian physics as, he points out, the sail can only contain so much air and the overflow pushes the boat. But this brings me to my big complaint of the episode:

After several seasons it seems the Mythbusters still have not learned the difference between a fan and a propeller. Something similar to this happened a couple of seasons ago when both Jamie and Adam tried making home-built hovercraft and Adam tried making a propulsive fan on his craft out of a fan.

Fans do not work this way.

Propellers do not work this way.

The same thing happens here when Kari tests out her small-scale rigs with various fans before getting the model-airplane device to produce a result.

If fans made a propulsive force then your home box or circular fan would blow itself over all of the time. Fans are nothing more than blades that whip up the air. Nothing else.

Propellers are sideways wings. Airfoil shapes that produce an aerodynamic effect of creating more airpressure on one side of the wing than on the other causing a net result of movement. We all know the basic airfoil design curved on top, flat on bottom, both tapering to a point on the end. The air on the top (curved) portion of the wing move slower (low air pressure) the air on the bottom of the wing moves faster (higher air pressure) the high air pressure pushes up on the low air pressure and you get lift.

Helicopters do not fly because they have a giant fan, the main rotor is a giant, multi-pedaled, wing that does this exact same thing. The tail rotor is doing this too only sideways to negate counter-rotation.

Propeller-driven aircraft are the same way the propeller is a sideways wing/helicopter rotor that creates low air-pressure in the front of it, high air-pressure behind it creating a "pull" forwards as the high air-pressure tries to balance out the area of low air-pressure.

A propeller and a fan are not the same thing.

Reef Boats/Fan Boats are the same thing as the "fan" on the boat is a propeller that produces an atmospheric change the air-pressure on either side of the blade resulting in a propulsive force.

However a fan could work in the terms of this myth as a big enough fan could blow enough air into the sail to create this "overflow" of air to produce propulsion but, I suspect, the airfoil design is more efficient in directing an air-flow force. In fact I assume the facing the fan backwards was so slow because the fan had to overcome "going backwards" to produce a "going forwards" motion the two forces were working against one another and the sail edged out the airfoil design enough to produce a bit or propulsion.

 

[Locutus of Bored]

(The most blatant example of Hollywood over-exaggerating suppressed guns is in the movie "Inception" when during the opening action piece DiCaprio's character shoots various guards with a suppressed gun and the gun makes no sound whatsoever other a "clink" sound from the shell being ejected. Now, some of you may be saying "it was a dream, it doesn't have to make sense" but in the movie's own rules making things too different from reality tips off the target's subconscious something is amiss and in the same sequence DiCaprio's character catches the spent casing with his hand. So why would he create a dream gun that needed a suppressor to be totally silent (as opposed to silent on its own) and also needed to eject a spent shell?)

I think it was just an example of perpetuating a common movie mistake, but from an in-story standpoint, the subconscious is only tipped off that something is wrong if what's happening differs from the subject's perception of reality, not reality itself. If Cobb's perception of how a suppressed gun sounds is entirely based on the barely audible whooph of movie silencers, then that's what he would imagine it to sound like and his subconscious wouldn't detect anything out of the ordinary.

As far as making a real "silencer" where it would dampen the sound enough that a person in an adjoining room couldn't hear the shot, I wonder if some kind of computerized active noise cancellation system with a microchip and speaker in the silencer could create an inverted phase sound wave of the same amplitude to cancel out the sound of the gunshot. It wouldn't completely eliminate the sound, but it could make it unrecognizable as a gunshot and quiet enough to not be noticed by people in nearby rooms.

 

[Brent]

Anyone else feel like the teams shoulda been reversed? Shoulda been Adam and jamie doing the blow your own sail myth, and the holywood sounds the B team.

Also, really? Movie sounds? How is that a myth, no one believes movie sounds are real, unless you are dumb. People know they use sound engineers to make these sounds. I don't see how its a myth when it is easily obtainable knowledge of how movie sounds are made. Yeah, this was just filler, it was a shark jumping moment.

 

[Lonemagpie]

(The most blatant example of Hollywood over-exaggerating suppressed guns is in the movie "Inception" when during the opening action piece DiCaprio's character shoots various guards with a suppressed gun and the gun makes no sound whatsoever other a "clink" sound from the shell being ejected. Now, some of you may be saying "it was a dream, it doesn't have to make sense" but in the movie's own rules making things too different from reality tips off the target's subconscious something is amiss and in the same sequence DiCaprio's character catches the spent casing with his hand. So why would he create a dream gun that needed a suppressor to be totally silent (as opposed to silent on its own) and also needed to eject a spent shell?)

Daft as it sounds, this works fine, because that's what almost everybody *thinks* a silencer does... So that would be their perception of the norm, especially in a dream.

 

[LitmusDragon]

Anyone else feel like the teams shoulda been reversed? Shoulda been Adam and jamie doing the blow your own sail myth, and the holywood sounds the B team.

Also, really? Movie sounds? How is that a myth, no one believes movie sounds are real, unless you are dumb. People know they use sound engineers to make these sounds. I don't see how its a myth when it is easily obtainable knowledge of how movie sounds are made. Yeah, this was just filler, it was a shark jumping moment.

This was definitely a reversal of the usual paradigm: the B team going after the "big" myth, and Adam and Jamie going after the trivial one. Maybe they just wanted to mix things up. Or maybe they gave that one to Adam and Jamie so that they could do that movie parody thing demonstrating all of the sound effects (which was actually pretty funny!).

Really enjoyed the blow your own sail myth. The sound effects one was a classic example of a filler myth. We don't really need to be told that movie sound effects aren't accurate do we? Also, they already covered the difference between movie explosions and real life explosions in a previous myth (the sound is just a minor detail).

 

[Trekker4747]

(The most blatant example of Hollywood over-exaggerating suppressed guns is in the movie "Inception" when during the opening action piece DiCaprio's character shoots various guards with a suppressed gun and the gun makes no sound whatsoever other a "clink" sound from the shell being ejected. Now, some of you may be saying "it was a dream, it doesn't have to make sense" but in the movie's own rules making things too different from reality tips off the target's subconscious something is amiss and in the same sequence DiCaprio's character catches the spent casing with his hand. So why would he create a dream gun that needed a suppressor to be totally silent (as opposed to silent on its own) and also needed to eject a spent shell?)

Daft as it sounds, this works fine, because that's what almost everybody *thinks* a silencer does... So that would be their perception of the norm, especially in a dream.

No, you don't get it. It made no sound at all just a "clink" from the casing being ejected. In most movies a silencer at least makes a "Ptew" sound.

 

[Temis the Vorta]

Blowing the sail worked? Wow!

 

[scotpens]

. . . One of the aftershow questions pointed out that real sailing is rarely done with the wind blowing straight forward into the sail. Now that I think about it, sails on boats are usually at an angle to the direction of motion. So a sail isn't just a parachute, it's a device for redirecting the thrust of wind onto a vector useful for propulsion.

A modern sail actually acts as an airfoil, like a vertical airplane wing. A sailboat is at its most efficient on a broad reach.

Also, really? Movie sounds? How is that a myth, no one believes movie sounds are real, unless you are dumb. People know they use sound engineers to make these sounds.

You’d be surprised at how many people think the background sounds they hear in movies are recorded live while the cameras are rolling. People don’t realize that most movie sound, except for dialog spoken by the actors on-camera, is added in postproduction. And that even a lot of the actors’ lines have to be re-recorded or “looped” in post.

 

[Trekker4747]

Blowing the sail worked? Wow!

Yep. If the sail is too small some of the air being putout by the "fan" escapes around the fan, thus not canceling everything out and allowing thrust to occur, in the opposite direction from where the sail is pointed. If the sail is too large and the fan is going high enough eventually the sail's air-capacity is met, the excess air is forced backward resulting in forward movement.

 

[Locutus of Bored]

(The most blatant example of Hollywood over-exaggerating suppressed guns is in the movie "Inception" when during the opening action piece DiCaprio's character shoots various guards with a suppressed gun and the gun makes no sound whatsoever other a "clink" sound from the shell being ejected. Now, some of you may be saying "it was a dream, it doesn't have to make sense" but in the movie's own rules making things too different from reality tips off the target's subconscious something is amiss and in the same sequence DiCaprio's character catches the spent casing with his hand. So why would he create a dream gun that needed a suppressor to be totally silent (as opposed to silent on its own) and also needed to eject a spent shell?)

Daft as it sounds, this works fine, because that's what almost everybody *thinks* a silencer does... So that would be their perception of the norm, especially in a dream.

No, you don't get it. It made no sound at all just a "clink" from the casing being ejected. In most movies a silencer at least makes a "Ptew" sound.

You need to watch it again. It made a very typical movie silencer sound.

 

[Nerys Myk]

Now they need to explore if "pew pew pew" is real.

 

[Ryan]

As far as making a real "silencer" where it would dampen the sound enough that a person in an adjoining room couldn't hear the shot, I wonder if some kind of computerized active noise cancellation system with a microchip and speaker in the silencer could create an inverted phase sound wave of the same amplitude to cancel out the sound of the gunshot.

Or, you know, just use a less powerful ammunition.

I'm really surprised the Mythbusters missed this in their research.

 

[Christopher]

Or, you know, just use a less powerful ammunition.

I'm really surprised the Mythbusters missed this in their research.

But that wasn't what they were testing. They weren't looking at how to make a gun quieter, they were looking at how the movie sound effect of a "silencer" compares to the sound of a genuine suppressor.