hats off to the raggies!

[Warpa]

From my viewpoint at work down Woolston they are still making good use of the waters, was very blowy today and bloody cold compared to how it has been, yet there were always one or two coming or going from the itchen

Still trying to figure out how a sailing boat can use wind power against the wind without me having to google it Im starting to think it has something to do with the sail at the front (is that the spiniker?) and that catching the wind at an angle to throw it onto the main sail

Either that or im thinking the sailors have some small form of Jedi powers and use the force, or its all jiggery pokery and black magic

 

[sarabande]

ah, in five years' time, the Force will direct you, and you will want to change from the Dark Side. You will then look upon your time as a Moboist, as an adult looks upon his childhood. True Jedis are raggies (with the exception of Brendan, of course )

 

[Bav34]

Still trying to figure out how a sailing boat can use wind power against the wind

VERY simplistically:

A yacht can only sail ''45'' degrees towards the wind.

The sails are wound in tight.

The boat now wants to blow sideways down wind.

The keel prevents this.

The boat HAS to go somewhere so it choses the point of least resistance ... the pointy bow ... and moves forward.

THEN WE TACK IN FRONT OF YOU LOT so that we can zig-zag upwind.

 

[Searush]

The sails form a curve that acts like the wing of an aircraft creating "lift" at right angles to the sail. That lift can be resolved into 2 component forces, the larger part trying to move the boat sideways & a smaller part moving it forwards. Hull & keel design is such that the sideways forces are resisted strongly so the boat heels rather than moving much sideways & the forward motion meets very little resistance. A yacht does move slightly sideways as well as forwards which is why leeway has to be taken into account when planning a course.

Have a read of the Ladybird Book of Sailing. It's explained very well in there.

It can be very useful to know what a yacht is going to do next. As the wind, tide & charts mostly dictate our movements, it isn't hard to predict when a tack will happen.

 

[hlb]

Your sort of right, think about an aircraft wing, it takes longer for the wind to go over the top, than go underneath. So it causes a vacuum on top, so the plane is lifted into the air, rather than pushed.

A sail boat does similar and attemps to get as much wind as it can, between the sails, so it is sailing, ( towards the wind) on lift only. Some boats can get as close as 30deg to the wind, but each degree closer will be slower and slower.

Sailing boats actually sail much quicker on a broad reach, where the wind is coming from the side, so it is both pushed and pulled along.

Wind from behind being much slower.

 

[rafiki_]

Well done Haydn. A simple and clear explaination. Welcome back to the forum. Your inputs have been missed for a while.

 

[Neil_Y]

When we tack in front of you we'll also slowly change course after the tack to confound and confuse, the angle we can sail depends on boat speed so we start off at a bigger angle to the wind until we pick up speed, even though we may be able to sail at 30deg to the wind we have to start off at 45-50 if the boat has slowed down. The bigger/heavier the boat the more it will slow in a tack.

We also do course changes in gusts sometimes performing the laying the boat on its side manoeuvre if trying to hard, and then there is downwind with spinnaker manoeuvres which can be even more dramatic.

 

[jonic]

Either that or im thinking the sailors have some small form of Jedi powers and use the force, or its all jiggery pokery and black magic

Thats it really, there is some string involved too, but its mainly mind control and magic.

 

[Firefly625]

it must be very strange to share the water with other craft that you have no idea how they even manage to propel themselves.... should it be compulsory for all mobo owners to learn to sail first...?

 

[sharppractice]

just back form ten days in Greece on a sailing boat learning about ropes n stuff wanting to gain an insight into the insane weaving needed when not having natural propulsion (diesel). Came back to find one of the insane weaving vessels previously mentioned had crashed into the side of my boat whilst mine was tied up at the marina.!

 

[colingr]

it must be very strange to share the water with other craft that you have no idea how they even manage to propel themselves.... should it be compulsory for all mobo owners to learn to sail first...?

As a (current) mobo man I agree (but don't tell anyone )

I find having sailed in the past helps me not annoy you lot. Doesn't stop you lot annoying me sometimes though so maybe some mobo experience to raggies might help as well? I know yachts are mobos sometimes but nothing like trying to handle a light planing mobo in a cross wind at low speed.

 

[jfm]

think about an aircraft wing, it takes longer for the wind to go over the top, than go underneath. So it causes a vacuum on top, so the plane is lifted into the air, rather than pushed.

Scuse the thread drift, but while there must be 1000 text books saying that's how an aeroplane flies, and it is taught to pilots in their training, it is in fact wrong. As any fluids/aero engineer can prove to you, if you do the maths you can see that the story about the air going the "long way round" above the wing wont make it fly. It will make a modest contribution to lift, but it wont make the plane fly

An aircraft actually flies because its wing is rammed hard into the air, at an angle, by the engines. That creates lift by Newton's laws. It's exactly the same mechanism as a waterski and a planing mobo

Planes can fly upside down.

Getting back to the point though Haydn, you are 100% right about yachts. The wing formed by a yacht's sail produces virtually all of its force by the "long way round" phenomenon (called Bernouille)

 

[DAKA]

should it be compulsory for all mobo owners to learn to sail first...?

Its a thought but first it should be compulsory for Raggies to learn to sail first , just at quick glance at col regs would help them to realize col regs are not 5 words long 'power gives way to sail'

 

[MapisM]

Getting back to the point though Haydn, you are 100% right about yachts. The wing formed by a yacht's sail produces virtually all of its force by the "long way round" phenomenon (called Bernouille)

Aaah, the good old Newton vs. Bernoulli debate...
Incidentally, I guess that by "virtually all of its force" you're not saying that there isn't also an AoA/Newton effect with sails, right?
Because even if I couldn't say in which percentage the two effects apply to sailboats, I see no reason why Newton shouldn't work also in this case.

 

[MapisM]

Its a thought but first it should be compulsory for Raggies to learn to sail first

 

[Firefly625]

Its a thought but first it should be compulsory for Raggies to learn to sail first , just at quick glance at col regs would help them to realize col regs are not 5 words long 'power gives way to sail'

totally agree with you there....

 

[jfm]

I see no reason why Newton shouldn't work also in this case.

You're right, AoA and Newton do in genera contribute to sail boats. The numbers are very complex though

For Newton AoA to work you need an external force. =The props on a mobo or the tow-rope on the water ski. The work done by the foil (force x distance, where force is the drag and the compression load on the fluid below and in front of the foil) is equal to the work done by the engine (totally ignoring friction and all parasitic losses, of course)

With a sailboat there generally is no such "engine" to do any work on the foil. But there is the wind, and that is the engine. Alternatively, if you think of motion as all relative, you can think of the air as stationary and the keel as pushing the boat into the wind like a massive midships bow thruster/propeller. The maths is the same however you choose to do it. So that gives you much Newtonian lift force. Another way to visualise it is that the keel and hull make a resistance like the string of a kite, and that causes the wind to create Newtonian forces on the sail. To state the obvious, a kite flies almost entirely due to Newton, not Bernouille; it is a copycat of a waterski.

Of course on a sailboat there is Bernouille force too. The Newton/Bernouille mix depends on the point of sailing so you cannot generalise. Broad reaching is mostly Newton; closehauled has much more Bernouille. The maths is very complex and beyond me now (though not at university!)

Very crudely, iirc, on a commercial plane the bernouille/Newton mix is in the order of 25-75 in steady state no-flaps flight

 

[MapisM]

The Newton/Bernouille mix depends on the point of sailing so you cannot generalise. Broad reaching is mostly Newton; closehauled has much more Bernouille.
The maths is very complex and beyond me now (though not at university!)

Yup, precisely my thought - even if just in principle: I also couldn't be bothered with the math.
And TBH, I wouldn't have been also in my uni years... Not for a thing like this, anyway.

 

[Warpa]

The sails form a curve that acts like the wing of an aircraft creating "lift" at right angles to the sail. That lift can be resolved into 2 component forces, the larger part trying to move the boat sideways & a smaller part moving it forwards. Hull & keel design is such that the sideways forces are resisted strongly so the boat heels rather than moving much sideways & the forward motion meets very little resistance. A yacht does move slightly sideways as well as forwards which is why leeway has to be taken into account when planning a course.

Have a read of the Ladybird Book of Sailing. It's explained very well in there.

It can be very useful to know what a yacht is going to do next. As the wind, tide & charts mostly dictate our movements, it isn't hard to predict when a tack will happen.

LMAO

I have a stack of ladybird books that i had 40 years ago, dont recall if i have that one...will check.

Nope i dont have that one, that Tassletip would have an ASBO order today!!

Of the educational ones i have;

British Wild Flowers
The Postman and the postal service
Arms and Armour
Subtraction made easy
Levers, Pulleys and Engines (doesnt cover mercruiser i bet
Houses and Homes
How to Swim and Dive
Leaves
Exploring Space
The Farm
The Nurse
Pope John Paul II That would have been my gran buyng that
Dinasaurs
Commercial Vehicles
And fanally
Lighthouse, Lightships and Lifeboats

They all take me back to my younger days

 

[l'escargot]

Its a thought but first it should be compulsory for Raggies to learn to sail first , just at quick glance at col regs would help them to realize col regs are not 5 words long 'power gives way to sail'

And moboers learn that it isn't "just like driving a car" ?