Blowing your own sail
- Thread starter Liquidfox
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What's so hard to understand about newtons laws?
Soldato
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The fact that i've done this and it works?
It works, but not in the way the sail is designed to work.
So it depends how you word the question. Is the questions moly does it work in any way, or are we talking hypothetically in a perfect system.
Your experiment would not be very efficient at all and the sail is not working like a conventional sail.
As said it would be much better to just remove the sail. If you used a smaller fan, then it would give a true result, of no movement.
People often do things and get contradictory results, we see it all the time with perpetual motion machines et al. Experiments need to be conducted in an approved scientific matter, not like mtyhbusters etc. and home experiments that are subject to many uncontrolled variables and a scientific misunderstanding.
Both can happen depending on the exact setup - as seen in the mythbusters video.
I think the main question is this: if you have a fan, why the hell wouldn't you just use it on its own to propel the boat?
Soldato
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And yet the air you're blowing at the sail isn't coming from inside the craft, it's coming from outside. The fan creates a difference in pressure so the air moves in a general 'towards the sail' direction. Which is essentially exactly the same effect as wind.
No it's not, as it instills all that force through the fan, so it is eternal. Otherwise your sail would be working like a normal sail and your boat would be going many magnitudes faster.
Soldato
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I don't think it matters for our present argument if it's an efficient way of travelling, just that it's physically possible.
As I said, you are using a 100% efficient fan which is bolted to the boat..
You are creating 2Nm of force..
That force has to be exerted on the fan assembly in the opposite direction.
The fan is bolted to the boat so you are not going anywhere
I've only just watched the first of those mythbuster links, but isn't the only reason the boat moved because of the force of the propeller? The fact that the sail was there meant nothing, it was just moving backwards for the exact same reason it would have moved backwards if the sail wasn't there in the first place.
I'm confused. So what is happening in all 3 different tests that mythbusters perform.
As I said that depends on the question, in the traditional sense of how the sail works, then no it is not possible, as a smaller fan would prove.
The bee video with the helicopters is a much better test and with less variables and is what would happen in the boat under proper testing.
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Soldato
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Surely if the sail wasn't there the craft would move in the opposite direction? I'd break paint out but it's late and i'm up early in the morning so you know...
Don't bother, you are wrong.
Actually he's right in that point, without the sail, the boat would go in the other direction, just like a hovercraft.