Seems the retro fad continues - sail power

[Colin Bignell]

We only controlled a quarter of the world's land surface and we did a lot of trade with the bits we didn't control as well. Clippers, designed for speed above carrying capacity or economy of operation, were built for the China tea trade, for example.

I don't think that the advent of steam affected the decision to build the Suez canal. The idea had ben explored by the Venetians in the 15th century and the French in the 17th and 18th, as a way to avoid having to transit the treacherous seas around the Cape of Good Hope. Steam probably made a difference as to whether it could be built though, as most of the original modern canal (the Pharaohs had one) was dug by machine.

[Paul]

This is not an aggressive sail design. It's designed for low maintenance. That is why it has such a small sail area.

Paul

[Rod Speed]

Wind is intermittent.

[Rod Speed]

The problem is that it isnt.

There is one cruise ship that does it that way, and since its a cruise ship, not a problem with getting the containers on and off, but its a dud economically.

And there is no way to do a container ship wind assisted.

Not going to work with a container ship.

But container ships don't.

[Rod Speed]

But no way to do the rigid sail masts on a container ship and no where to put the sails when not needed.

That last is because they are targets for nuke missiles.

Nuke powered contain vessels arent.

[Colin Bignell]

There was a concern that a failure of the system could result in a car flying off the track and, possibly, into the spectators.

[Jethro_uk]

Aren't they building planes like that now ?

[Rod Speed]

Nope.

[Soup]

Well use engines for that. Less rugged engines are required as (say) 70% of the running will be wind powered whilst the rest (docking adverse winds etc) can be engine powered.

[Soup]

Well when wind drops to zero or an againsterly, fold down whatever passes for the mast system and use engines

[The Natural Philosopher]

No. They use slats and fowler flaps

[alan_m]

70%? - even the hype doesn't claim anywhere near that in fuel saving. These are not ships that can sail by wind alone - they are wind "assisted".

A much greater fuel saving can be made by slowing down a ship by 20%.

[Colin Bignell]

Not that I am aware of. There are easier ways to delay boundary layer separation. If you look out of the window of many airliners, you will see a row of small metal tabs along the top. Those are vortex generators, which are, small, light, with no moving parts and they delay boundary layer separation.

The only use of perforated wing surface I can think of is along the leading edge on some aircraft, where it is used to dispense anti-icing fluid.

[The Natural Philosopher]

Well in WWII they had machine gun ports as well. :-)

The fact is that what aircraft designers are after is a controllable high lift low speed performance for landing, and for some cases, takeoff. High drag is not a problem, and in fact it is advantage, in getting speeds down to landing speed..

So *controlled* boundary layer separation is the goal.

[charles]

The suction boundary layer experiments were over 60 years ago. Ideas have changed.

[Colin Bignell]

If you are counting holes that big, they also had balloon cable cutters fitted to bombers.

The Miles Magister trials were about finding ways to increase fighter speeds at a time when engine powers were fairly low. However, weight is not quite as much of a problem on a ship.

[alan_m]

And aircraft technology has kept pace with new ideas over those 60 years, especially when it comes to using less fuel.

[The Natural Philosopher]

I don't think ideas have changed, its simply that the cost-benefit advantage of sucked or blown wings was very poor.

I have noticed that non engineers (and some engineers) think in terms of

*possibility*, but neither practicability, nor cost effectiveness.

(Which is of course why people think renewable energy is cool).

THIS is how you decrease landing and takeoff distances!

and massive flaps. And a bit of a headwind.

[Soup]

For (say) read numbers picked out of my nefr.

[Andrew]

Hence the term 'The doldrums'