Since we're doing dumb physics/maths questions...

[Menelaus]

Bernoulli - WHS above.

[threaded]

Out the aft (assuming you want to go forwards).

I guess the obvious answer is to point it at the sail, but that can't work as the sail is attached to the boat, and the fan is (effectively) attatched to the boat too. The best thing you can do with the sail is take it down to remove any drag.

Couple of clues:

The air isn't attached to anything is it?

You are best leaving the sail up.

[Grinder]

Let me throw something in here (just to stir it up a bit more) - a helicopter works doesn't it? It has no sail underneath the rotor blades. If it did, it would not fly.

[minestrone]

In the water, use it as a prop.

[Grinder]

In the water, use it as a prop.

err *cough*

How about into the water?

[scooterscot]

There's a reason I'm not an IT contractor - yes - these guys are on the tip of the sword there's no way I could wrestle with that kind of intellect.

[NotAllThere]

Oh this should be a fun thread, because I actually tested this, (in a Physics laboratory no less,) so know the answer.

So, while the rest of us give our neurons a work out, and go to the effort of working it out from first pricinples, you just go an try it in a physics lab. Lazy git.

[Advocate]

Electric music's rubbish, I'd chuck the fan overboard!

[original PM]

given my previous lack of success with these damn questions I should leave well alone but I am glutton for punishment so here goes.

1) You could in effect use it to blow wind into the sail - I cannot see a problem with this. So point it foward.

2) It may be more efficent to point it back wards - either above the water so it acts like a hovercraft/swamp boat fan - but these tend to be quite large - so you may have more joy pointing it backwards in the water so it acts as a propeller.

3) I am sure the Benoulli principle will work also

As to which is going to be the best of the 3 options - I would go for using it as a propeller!

Come on someone come up with the correct answer to put me out of my misery!

[d000hg]

Put it on the back (stern) of the boat, pointing backwards (astern) so it pushes air out behind the boat. Additionally, take the sail down.

It's because of Newton's 3rd law, but I won't spoil the thread completely by explaining the reasoning just yet.