h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Probably an easy one

Sail boats and ships can sail close to the wind, about 45 degrees in a modern fore and aft rig, about 60 degrees for a square rigger.

What is the principal that allows this. And what did this make possible?

F S

Guess the square rig and a rudder on the stern

No we are looking for a little physics here.

F S

Well it was a guess and its nearly 2am here and I he man wants physics more like.
Off to think it through.

Torque?

No, not torque. That has more to do with turning shafts and the like.
For some reason it has also been ascribed to obscene dance moves, but I am not sure you can apply it to a sail boat unless you twist the mast out of her.

F S

Oh, is this trimming the sails? I've heard of it but never quite knew what it meant.

Is it not because the contour of the sail is curved and it acts like an aeroplane's wing when pointed into the wind. In that the aerofoil shape generates lift at right angles to the centre of lift of the sail? It's just that the 'lift' force is generated horizontally, not vertically which allows the boat to move 'against' the direction the wind is coming from.

Oh... IIRC the first sail to use the principle was the Lutine (sp) sail.

The physics part of the aerofoil is Bernoulli's principle.

Well done 27380 I knew someone would know here. Next question please

Also good for Icy naming Bernouili's principal. I am sure sails have been cut like that for thousands of year, they just didn't know why they worked so well.

F S

BTW Icy;

Trimming the sails is to adjust their angle to the centre-line of the boat. When the wind is behind you you want them as far out as possible to catch the most wind. As the wind moves to the side, or even in front of the mast you keep pulling them closer to centre to keep the boat moving as fast as possible.



F S

Back in a day when I once tried to learn ( unsuccessfully) how to sail a dingy, I got repeatedly shouted at for not trimming the sail I was in charge of correctly. It was the jib, and apparently I was pulling it too tight, and 'back winding' the sail. I never could get the hang of it.

Anyhow... For a question

What did Douglas T Corrigan do wrong?

Broke with his flight plan and flew from New York to Ireland instead?

I can only agree with ITIWBS.

Wrong Way Corrigan flew his plane to New York City and filed a flight plan to cross the Atlantic Ocean. The authorities refused to accept it and instead only authorised him to return to his home airport (I believe it was in Chicago). After re-fueling his aeroplane he flew east instead of west and completed his flight.

He claimed to have been confused by his compass, but after landing at his intended destination, about 3,000 miles away, no one believed him.



The second principal used in sailing with multiple sails is the 'Venturi Effect' - narrowing the width of passage of a gas increases its speed. However you have to watch the front edge of the other (main) sail, to make sure you don't make it too narrow

I would have yelled too, but then I would have tried to explain what you were doing wrong.

F

At which lunar crater did Harrison Schmidt and Gene Cernan discover the orange earth?

Ah... Sorry for getting behind the game.
Yes Corrigan crossed the Atlantic accidentally. Apparently he never admitted that he'd done it deliberately and blamed flying a reciprocal course in poor visual conditions. He said he didn't realise it until 23 hours into the flight.

His aircraft, a Curtis Robin, developed a fuel leak from the tank leaving the cockpit floor awash with petrol. He cleared it by punching a hole in the floor with a screwdriver on the opposite side to the exhaust

Anyway, over to ITIWBS

See post 197