Turbo sail - 100 knots?

[Rob melotti]

Steve - but is it propulsion? With super-conductive materials and very high output batteries providing temperature control over a foil designed in such a way to counter-act the cooling effects of high speeds...

Perhaps a foil within a foil... the outer one generating normal lift up to a certain speed then an inner temp-controlled one acts as a booster??

[marshmat]

Interesting concept... wonder if it would catch on, or follow the path of the Flettner ship ( http://physics.kenyon.edu/EarlyAppar...otor_Ship.html ) which, although interesting, never became practical.

[Vega]

Originally Posted by Rob melotti

Frosh - this should really get you going... What about super-cooling the luff while heating the leach? Mega-turbo!

[frosh]

Hey Rob, Do you propose to use normal sail cloths albiet exotic ones for your heating and cooling thingo. What is the melting point of mylar and does it remain flexible at around 50 degrees Kelvin? Carbon might be much more temperature tolerant, but the way that the US defence force is buying up the stuff, there may soon be none left for ordinary guys like you and me.

[FAST FRED]

"A jet engine basically heats up air that travels over a foil, thus creating thrust "

By that logic a B-727 , DC9 or DC 10 among many others with tail mounted engines,would never leave the ground.

Strange, that Boeing built 1700 of them.

A jet engine works by tossing mass (exhaust gasses and air) rearward.

FAST FRED (With 20,000+ hours driving stuff you say cant aviate!)

[Rob melotti]

Originally Posted by frosh

Hey Rob, Do you propose to use normal sail cloths albiet exotic ones for your heating and cooling thingo.

Best to use those ceramic tiles that line the bottom of the space shuttle. They can go to very high temps but cool off v fast as well (useful for stopping/controlling the boost). Don't really know anything about cooling - something to do with converting gases into liquids??? Somehow need to stuff a refrigerator and an electric oven inside a sailwing, and hang on for dear life..

[SailDesign]

Fred,
I guess I should have put a tongue-in-cheek icon in there somewhere....
If it makes you feel better, bees can't fly, either.
My point, small though it might have been, is that using external energy to increase sailing speed is not far off just using a motor. How about taking the energy that would be used to heat/cool the sail, and using it to power a big fan on a nearby barge that will follow you around the course? Still "sailing"
Steve

[frosh]

Hi guys, I just consulted a PhD student regarding a nagging doubt that I had about Robs idea that there would be a massive air flow from luff to leach.
His opinion was that it is all about air pressure differentials. He explained it like this: If you tighten the bungs on a hollow boat and then leave it in the hot sun for a while. Assuming it does not burst, and then you open a bung what happens, yep the air rushes out not in!
Extending this argument to the sail the air at the leech becoming hot and expanding, would flow towards a region where the air has contracted in volume due to super-cooling. Kind of throws a spanner in the works!

[antonfourie]

I think that there are loads of spanners in this lot of works, one being that heat rises the flow would be up the sail not along it, two being that you would have to have a small nuclear reactor to power all this heating, three you would need a 10t mast to hold all the ceramic tiles that you make the sail out of.

But none the less without people trying things we would never have got too the moon ...

[CT 249]

Yes, but they only tried the things that were possible........

[SailDesign]

If heating up one side of a sail and having the air rush across to the unheated side worked, then the radiators in your house would blow heat at floor level, not just by convection currents (hot air rising)
Or have I missed something this winter?
Steve

[frosh]

Steve, you are right. Look at the principle behind the hot air balloon. Has been established for more than 200 years!
The other thing that worries me is the extremely inefficient use of energy.
Last Winter I got rid of my reverse cycle air conditioner at home and replaced it with a thick solid iron rod mounted in the centre of each room vertically.
Using an oxy torch I then heated each rod until it glowed orange in the dark.
I naturally assumed that the massive heating of air around each rod would cause the air to heat up and rush out at considerable velocity in every direction. Guess what? Nothing! The only thing that happened was the cat lost all its hair on one side!

[frosh]

Hi Guys, recently read a more promising concept than the "now sunken" concept of heating and cooling the sail. It is really happening for motor cars; see it at www.theaircar.com
All that needs to be done is to create a hull built around a large compressed air tank.
Fill with liquid air, I know that it is probably heavy but no problem!
Then you have two options: (1) is for purists, you release the valve and using a pipe and specially shaped diffuser, direct the extremely high velocity air stream at the sail which you set for a beam reach. 100 knots of air velocity should be easy, and as efficient craft these days sail faster than the true wind, you only have to work out how to keep the hull in contact with the water to get a speed perhaps double the existing sailing speed record.
(2) If you are not a purist and don't mind cheating a bit, assuming that no one really works out what is going on, you put up the sail just to make it look like you are sailing, but direct the pipe under the hull and facing rearward.
You will overtake the Kawasakis and Yamahas, (jet skis) like they are stuck on an anchor cable!

[antonfourie]

frosh, for every action you get a equal and opposite reaction, one of Newton's laws, so your blast of air aimed at your sail would push you backwards so to speak. You would be better off directing the flow along the sail, to create the "low" pressure on the lee of the sail that will create the "suction" to power your boat.

[frosh]

Hi Anton, I am very familiar with Newton's Laws. I did say that the sail would be set as for a reach. In normal sailing with a high peformance yacht, the apparent wind would be coming at around 45 degrees off the bow, even though the true wind is 90 degrees. This 45 degree angle is the one I would use for the blast of compressed air. Do you think that this might work?