Help needed by clear thinkers ;)

[bambodoggy]

Hi All,

I've got a question that's been bugging me for ages and although I have asked many people....I'm still not sure I know the answer.....but I'm sure one or two of you will

So, if I stand on the edge of a lake with a petrol powered leaf blower and blow it into the sail of a little sailing dingy, say a Topper or similar, it will fill the sail with "wind" and blow the boat away or propel it forward.
If I stood on that same dingy (regardless of sail up or down) and aimed the leaf blower to the stern, the force of air would again propel the boat forwards.

Still awake?

So my question is: If I stood on that same dingy with the sail up and aimed the leaf blower into the sail....what would happen? Would the boat move or not?

Many thanks in advance,

Bam.

 

[mountainm]

No. You are on the boat. The forces cancel out.

 

[bambodoggy]

No. You are on the boat. The forces cancel out.

Yer....see that's where I think I am....but then somebody I respect goes and says something different lol Thanks

 

[ged]

Er, it depends.

If your sail deflects the blast of air from the leaf-blower so that there's a net movement of air in some direction, and it could hardly be otherwise of course, then the boat will experience a force (from the mast and the rigging) in the opposite direction.

Of course the boat certainly has a hull, and if it has a sail it probably also has a keel, so it might not actually move in that direction because the water will exert forces on the hull and the keel, just as they do when she's sailing (which is a much more sensible pastime than waving leaf-blowers around for ANY reason other than to get a fire going).

 

[drliamski]

Why do you need the sail just point the blower in the opposite direction that you wish to travel and cruise off?

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[GGTBod]

it reminds me of a closed truck full of chickens on the truck weigh station, half the chickens are flying inside the truck and half are standing on the floor of the truck but the truck remains the same weight, remove the roof of the truck and the equation stays the same unless any of the chickens fly above the hieght of the truck and their weight is minus from the original total weight.

So because of this i am in the boat stays still club due to forces acting upon each other in the boat, like you swaying backwards slightly, the deck flexing and in turn flexing through the boat structure and the water on the boat responding to these forces in return.

Good brain work either way imaging the interactions

 

[GGTBod]

further thought, what about if you are on the boat and only blow the leaf blower at the sail whilst jumping in the air?

 

[bikething]

further thought, what about if you are on the boat and only blow the leaf blower at the sail whilst jumping in the air?

you may not be in the boat for long

 

[ged]

you may not be in the boat for long

I owe you a pint for that!

 

[Johnnyboy1971]

Wouldn't an outboard be more suited than a leaf blower for a boat.

 

[British Red]

Think about a fan boat. The pressures certainly don't cancel out there. So I suggest an "air pusher" can move a boat. I also sugget that (as mentioned previously) trying to push wind into the sail would probably result in the boat going backwards since not all the thrust would transfer to the sail.

 

[mountainm]

Think about a fan boat. The pressures certainly don't cancel out there. So I suggest an "air pusher" can move a boat. I also sugget that (as mentioned previously) trying to push wind into the sail would probably result in the boat going backwards since not all the thrust would transfer to the sail.

Put a sail behind the fan on an air boat. The fan pushes one way, the sail the other.

 

[British Red]

Just so, but I suggest the sail does not capture all the kinetic energy meaning the forward motion would be impaired, not cancelled out. No energy transfer is 100% efficient.

 

[mountainm]

Just so, but I suggest the sail does not capture all the kinetic energy meaning the forward motion would be impaired, not cancelled out. No energy transfer is 100% efficient.

I'd argue if it went anywhere it'd be backwards (in the case of the air boat, forwards for the sail boat). Given the blast will fill and be directed off the sail.
However physics deals with perfect universes.

 

[Nomad]

The blower generates thrust. That's why a fan boat works, and why pointing the blower backwards will push the boat forwards. If you point the blower forwards, it will generate reverse thrust and try to push the boat backwards. It is very unlikely that the sail will capture enough energy from the locally generated wind to create enough of a forward motion to counteract the reverse thrust.

Now, if the blower was on a frame out to the side of the boat and was generating a local wind coming across the beam, then it is possible that the sail could be set up to make use of that wind to move the boat forwards (let some of the wind pass over the other side of the sail to generate lift). Due to the blower's thrust effectively pulling the boat to windward, this would also create negative leeway.

 

[Shewie]

Build a big enough sail and turbo up that leaf blower and job's a good 'un ...

[video=youtube;1QJz-BVXCI4]https://www.youtube.com/watch?v=1QJz-BVXCI4[/video]

 

[bambodoggy]

(which is a much more sensible pastime than waving leaf-blowers around for ANY reason other than to get a fire going).

I think you'll find that for anybody over the age of 35 it's perfectly acceptable to wave backpack leaf blowers around while pretending to shoot green goo monsters and singing Ghost Busters at the top of your voice

 

[cbr6fs]

[video=youtube;bG24Sa_bluI]http://www.youtube.com/watch?v=bG24Sa_bluI[/video]

 

[bambodoggy]

Build a big enough sail and turbo up that leaf blower and job's a good 'un ..

Brilliant.....thank you so much for that, I knew somebody here could answer it for me

Good brain work either way imaging the interactions

Very boring days spent standing still grinding stumps out one after the next gives me loads of time to imagine weird and wonderful conundrums to entertain myself lol

 

[tom.moran]

Pretty sure mythbusters did this and got a very small amount of movement

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