Turbo sail - 100 knots?

[Rob melotti]

Just read Yachting World article about breaking the speed sailing record. There's an Aussie guy who doesn't think 100 knots is out of the question. My question is:
Has anyone tried heating up the leach of the sail? A little knowledge is a dangerous thing, but surely it follows that if you heat the leach it will suck more air across the sail/wind creating more lift/thrust??

[dimitarp]

It is a fully

[frosh]

:!: It sounds like a wet dream to me.

[Rob melotti]

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

[frosh]

Hi Rob, If you can get crossbow; see it at http://www.dcss.org/speedsl/crossbow.html bring it to Northern Queensland where they have been having absolute monster cyclones. Build a 50 meter long aka out of prepreg carbon fibre and put two guys out there during the next big breeze (250km/hour) and you will get a record that will last for centuries!:D

[TaSSie_deVil]

Either that, or die trying!! :D

[antonfourie]

It is only a matter of time, I am sure that climbing Everest sounded just as crazy before they got around to doing it ..... :)

[Rob melotti]

But heroics aside, by creating your own air-flow with hot and cold portions of a sailwing... you could do 20 knots in a flat calm, rising to 100 knots in a 20-knot breeze. Not that I can prove a word of this.. just seeing if anyone else can seriously ruin my day-dream speed sailer

[antonfourie]

How would you get over the "hot air rises" issue and get it to flow along the sail ?

[SailDesign]

I'm going to wait until someone gets to 50 in a boat, then I'll worry about whether 100 is possible. :)
We all know that 100 knots under sail is possible - it is done frequently in ice-boats. Doing it with the drag and stability problems associated with soft water is the key....
Steve

[Rob melotti]

Well put SailDesign. Any ideas on antonfourie's design question?

[SailDesign]

Rob,
Which design question of Anton's?
Steve

[Rob melotti]

How would you get over the "hot air rises" issue and get it to flow along the sail ?

Steve, I guess what you are saying is that high speed sailing on water is mainly a question of hull design - the sailwing/foil is already proven beyond 100 knots.
I guess what I'm wondering is whether any kind of heating/cooling mechanism could improve the basic design of the wing?
Anton's question has already stretched my (non-existent) practical knowledge of wind design... but what's on the horizon for sailwing design?

[SailDesign]

You're right, Rob, the 100mph thing is pretty much a given.
As far as the heating/cooling thing goes, how do you feel about people using electric motors during a sailing race? To apply enough heat to do any useful work against the cooling effect of 100mph (assuming the concept works in the first place) you would have to use a shiite-load of power. Is that really being propelled by the wind?
Steve

[SailDesign]

PS - Rob - A jet engine basically heats up air that travels over a foil, thus creating thrust - but it ain't sailing... :)

[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/EarlyApparatus/Miscellaneous/Rotor_Ship/Rotor_Ship.html ) which, although interesting, never became practical.

[Vega]

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

[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]

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! :confused:

[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! :o

[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?

[antonfourie]

I could do, as long as you have enough air, I guess that the opposite force would also help tp balance the boat, I assume that this would be in conjunction with a stiff breeze

[frosh]

Hi all, Are you taking this 100 knot B-S seriously? I certainly am not. Seeing the whole comedy routine seems to running out of puff I thought that I would come clean now. The increase in the sailing speed record has been folllowing a logarithmic curve with an infinity end point in time somewhere around 51 to 52 knots. I don't honestly believe the sailing speed record in water will ever get close to 100 knots, just as I believe that a runner will never do a 100 meter dash in 5 seconds! :D

[antonfourie]

LOL ... of course not, but then it is fun to discuss these impossibles, I mean you could always strap a jet engine to the boat to create the blast of air, but that could be cheating

[Burmzie]

Okay I am still a newbie at this, but I was thinking about your ideas of a 100 knot sailboat. It is very interesting what a group of people can come up with. I am have no naval design experience, but I do know that the quickest way to speed an object up is to reduce the friction, whether it be air friction or tire friction, or water friction. What if you were to install a simple line or groupings of airlines in the hull of said sailboat. You could harness the wind at the top of the mast by way of a windmill (of sorts), to power a simple compressor. You wouldn't even need to use electricity. Much the same as an air hockey table works. I know someone will say, "you can poke hole in the hull of a boat". I think if you could somehow design a one way valve on each of the outlets, water would not flow into the boat. Of course this is just an idea. Anyone who feels the need to slaughter this idea, please feel free to.

[frosh]

Hi Burmzie, Something along this line has been done and tested in Australia around 35 years ago. I think it was on the little fully decked skiff the VJ or its bigger cousin the Skate. Both classes are still actively raced.
The way it was done then was that a series of tubes were set in a line from port beam to starboard beam about half way down the length of the hull.
The tubes ran from the deck through to the bottom skin of the hull.
The idea was that a venturi effect at speed sucked air downwards and mixed it with the solid water under the hull creating a less dense air/water mixture. The aim was to reduce skin friction on the planing surface of the hull and increase high end speeds.
Only very few boats were built with this innovation, so we can only conclude that it was not a practical success. However your idea is a good one in theory. :)

[sharpii2]

It is only a matter of time, I am sure that climbing Everest sounded just as crazy before they got around to doing it ..... :)

So did building a perpetual motion machine.

Bob

[frosh]

Got to agree with Sharpii 2. 100 knots under sail with the boat in water is in the same ball park as the perpetual motion machine! :D

[antonfourie]

:) :) Yeah I figure that too, but then keep this in mind and we can check in 20 years to see if they are any closer.

[Guillermo]

The guy who says 100 kn under sail are possible is Simon McKeon, from Melbourne. He ran Yellow Pages to its 46.52 kn record (held for lomger than anyother). He's tryin again with Macquarie Innovation. His last attempt failed because of a failure in a minor piece in the sail which lead to its destruction.
http://www.ronstan.com/marine/story.asp?story=1668
Simon states:
"We're not spending time thinking about this, but I don't believe in barriers. Our boat does three times the speed of wind, our little America's Cup boat did four times the speed of wind. Ice boats are a good indicator that the wind is not the limiting factor, the difference is that they are running on a hard surface."

[Vega]

but I don't believe in barriers. ....Ice boats ara a good indicatos that the wind is not the limiting factor, the difference is that they are running on a hard surface."

I didn't think about the ice boats. Seems strange but probably he is right...even so 100m/h without the boat taking off, would have to be a completelly new thing, kind of a cross between a sailboat and an airplane:p

[frosh]

Ice boats ara a good indicatos that the wind is not the limiting factor, the difference is that they are running on a hard surface."
And that is a HUGE difference!

[antonfourie]

Yeah but water tends to get to be quite hard a 100Kn too

[frosh]

Agreed! water is pretty hard at 50 knts also if you face plant off your water skis. Interesting that the density of ice is less than water but friction is so much less on this medium. Something about a solid physical phase I guess. :D

[antonfourie]

mmm, wonder how far we are away from "teflon" for water or something super slippery ?

[SeaSpark]

To anyone who missed this thread:

http://www.boatdesign.net/forums/showthread.php?t=11497

[SailDesign]

Anton,
What gives ice its advantage is the fact that it is hard. It cannot be pushed out of the way, but the force of trying to do so melts it and the "Boat" (skate) hydroplanes on this tiny amount of water, with little friction.
Steve

[dimitarp]

How to achieve the 100 knots on water?. Is it possible to run with 100 knots on water?
To answer of these questions or similar questions we have to use some theoretical knowledge of aerodynamics and hydrodynamics. Here are some empirical considerations.
If we accept that exist only a sail ( wing ) and there are no other resistances in air and water then the speed of a ship is defined from:

Vs=Vw* L/D


Where: Vs - is velocity of ship (boat, windsurf), m/s ;
Vw – is velocity of wind, m/s;
L – is lift of sail, N;
And D – is drag of sail, N.

L/D ratio is a important characteristic of every sail and wing. For monofoil sail the maximum L/D is about 12; for doublefoil sail – 15 and for wing – 18 .
Let us now to add the resistances in air nad water, the equation for ship velocity will be:

Vs= (Vw/(1+m*Aa/As+n*Aw/As))*L/D


Where m – is ratio of resistance in air to drag of sail;
n – is ratio of resistance in water to drag of sail;
Aa – is all projection area of things that generate air resistance in direction of apparent wind.
Aw – is contact area of ship to water.
and As – is sail area

It is difficulty to estimate factors m and n theoretically. But if make some admissions they can be defined. The admissions are:
1. The wind is uniform;
2. The all things that generate the air resistance have a cylindrical form without gap and sharp angles;
3. All resistances in water are transform to a resistance of a flat with area Aw to water. This mean that water resistance is transform to only viscose resistance;
4. For large Re the resistances do not influence from speed.

Then m is about 10 and n is about 20.

I take part in a project that aim to estimate the possibility of achieving 60 knots in sailing on water. The first stage of this project is to define the m and n experimentally. The web site of this project now in constructing and will coming soon. The project is open for funds and advices from all. Now I will shortly present the second stage of the project.

Example:
Let us have a windsurf with Aw=0.8m2 , double sail with As=8m2 and crew with Aa=0.8m2 , then :

Vs = 3.75xVw. For achieving 100 knots the wind speed must be about 13.3 m/s. For this speed wind will be never uniform and heel moment will be very large. That is mean the crew (one man) have to will be with fine skill and must compensate the heel moment ( of about 30000 N.m). For compensating the heel moment we will use central boat fin and other fin.
But why the skill is so important?
The answer of this question lies in dynamics of windsurf. The acceleration of a ship is define from:

Fx+Fd = +- M*(dVs/dt)

where Fx – is the general tractive force, N
Fd –s the general resistance force, N
M – is general mass of ship, kg
t – is time, s
+ note acceleration
- note decelerate.

When the crew is made a mistake Fd is increase fast and velocity fall, but when every think is all right Fx increase much slowly from Fd about 10 times.

My conclusion is. The speed of 100 knots is attainable but we need from:

1. Special boat,
2. Special rig (probably wing)
3. Special conditions ( flat water and moderate uniform wind)
4. And Special crew.
Is it possible?

[frosh]

Hi Dimitarp, just when I thought that this was dead and sunk, as a serious proposition, you come along with some complex mathematics and show us that in fact 100kts is possible! :mad:
However even with my level of maths, which is probably less than yours, I can see some fatal flaws in your presentation.
You make an initial assumption that there is only a wing on this boat to create drive, and suffer drag, nothing else???
We havn't been able to do this yet, and I understand that hydrofoils are a type of wing but you do not include these in your calculations, do you?
Then there are those ratios, m and n. They make no real sense. If m is the ratio of resistance in air to drag of sail, these two items appear to me to be two items that have a fairly similar meaning. To make mathematical sense the two items need to be completely separate. The problem with n is even worse.
The ratio of resistance in water to drag of the sail. Is the sail drag occurring when it is in the air or water? If part of the sail is in the water, then again the two items have fairly similar meanings and can't form a mathematical ratio.
Then we have an assumption that m=10 and n=20. So if we simplify, and say the ratio m in air is 1, then the ratio n in water is only 2.
I must be missing something here! Jet aircraft wings can go through air at Mach 3.3 approx. 2000 knots. Accordingly then should a wing be able to driven through water at 1000 knots?
Please explain a bit better as you have lost some of us along the way! :confused:

[Doug Lord]

A foiler team from Australia including Sean Langman, Andy Dovell, John Biddlecombe and Rohan Veal believe they have a design for crunching the 50 knot mark on supercavitating foils.
More here: http://www.rohanveal.com/home.html

[dimitarp]

Hi Dimitarp, just when I thought that this was dead and sunk, as a serious proposition, you come along with some complex mathematics and show us that in fact 100kts is possible! :mad:
:confused:
Hi,
The resistance in air and water do not defines only from fluid characteristic but also it defines from area that in contact in fluid and from shape of body. The m parameter mean that the resistance in air from all other things ( exception of sail) is m times greater than restance from sail with same area. The n parametar mean that the resistance in water is n times greater than resistance from sail with same area.
The hydrofoil I do not comment at all. I think that at speed 100 knots it is anpossible to compensate the heel moment. The heel moment will be so great so can not be compensate with wight of sailor.
At high Mah number there are another effects and lift to drag ratio is fall to about 3

[marshmat]

I see a few iffy things in the mathematics mentioned earlier. The resistances are defined in very unconventional ways that do not bear a clear relationship to known formulae.
For instance, drag force (with no free surface) is normally parametrized as:
Fd = 1/2 * Cd * rho * V^2 * A
for drag coefficient Cd defined in terms of area A, at speed V in a fluid of density rho. Cd IS dependent on Reynolds number. I would like to see the calculations expressed in accordance with accepted engineering practice and with a little less hand-waving.
13.3 m/s of wind is about 48 km/h, or a little under 25 knots. Are you saying this boat would travel at over four times the speed of the wind driving it?
-Added- > By the way, the Mach number ( Ma = v / a ) is an indicator of compressible flow character and is only important if it is greater than about 0.3. For an object in air moving at less than about 100 metres per second, Ma is irrelevant.

[frosh]

Hi Dimitarp, I think that partly it is a language difficulty but are you now backing down from your earlier claim that 100 knots or even 60 knots is possible by a sail boat? Matt quite rightly points out that your mathematical equations are "unconventional" to say the least! "Yellow Pages Endeavor" solved the problem of lack of RM by a regular solo sailor but still has not achieved 47 knots even in the new model "Macquarie Innovations". You can find all the info on these at: http://www.macquarie.com.au/speedsailing/background.htm

[tspeer]

...
Let us now to add the resistances in air nad water, the equation for ship velocity will be:

Vs= (Vw/(1+m*Aa/As+n*Aw/As))*L/D


Where m – is ratio of resistance in air to drag of sail;
n – is ratio of resistance in water to drag of sail;
Aa – is all projection area of things that generate air resistance in direction of apparent wind.
Aw – is contact area of ship to water.
and As – is sail area
...

This is not true. The correct relationship is:

Vs = Vw * sin(gamma - beta) / sin(beta) = Vw * [sin(gamma)/tan(beta) - cos(gamma)]
beta = arctan(Ds/Ls) + arctan(Dh/Lh)

gamma = course relative to the true wind
beta = angle between apparent wind and boat's course
Ds = aerodynamic drag
Ls = aerodynamic lift
Dh = hydrodynamic drag
Lh = hydrodynamic lift

Even if beta is a small angle, the course gamma will not be a small angle. For small beta and a beam reach (gamma = 90 deg), the speed becomes:

Vs = Vw / (Ds/Ls + Dh/Lh)

Notice that this has absolutely nothing to do with projected areas at all, and it does not reduce down to the same expression when you substitute in the ratios m and n.

Here's a real-world example of the kind of sailing performance you're talking about. The current landsailing speed record (http://www.nalsa.org/speed_record.htm#note)is 116 mph, or right at 100 kt, set in winds of 25 - 30 mph. This is a boatspeed/windspeed ratio of about 4. So beta had to be no greater than 14.5 degrees. This is what you have to shoot for if you want to go 100 kt on water.

Say, beta = 14 degrees just to provide a little margin. The optimum angle to the true wind will be 104 degrees [sin(gamma-beta)=1], just below a beam reach. In order to establish some requirements, arbitrarily divide beta into its aerodynamic and hydrodynamic drag angles:

beta_s, beta_h, Ls/Ds, Lh/Dh
7, 7, 8.1, 8.1
5, 9, 11.4, 6.3
3, 11, 19.1, 5.1
1, 13, 57.3, 4.3

The best Standard Class sailplanes achieve L/D's on the order of 40, so an aerodynamic drag angle of 2 - 3 degrees is probably the best you can hope for. Call it an L/D of 20 for everything in the air. This means that you have to achieve L/D's for the hull & foils of at least 5. At 100 kt.

The lift on the hull will be approximately equal to the lift on the sails, and the drag of the hull will be equal to the drag necessary to support the weight plus the drag from providing the lift to oppose the side force on the sail.

Dh/Lh = (W/Ls) * 1/(Lv/Dv) + 1/(Lf/Df)
W = weight of the boat + vertical load from the sails
Lv/Dv = L/D of vertical support
Lf/Df = L/D of foils providing horizontal lift

This is where sail area comes in. If the L/D's can be maintained, then a high ratio of sail loading to weight (Ls/W) will improve the performance. If the vertical and horizontal L/D's are the same and the sail-force to weight ratio is about 1, then an L/D around 10 from the vertical foils is in order.

At 100 kt, you're way past the subcavitating regime, so you will have to use supercavitating foils to provide side force. Or fully ventilated angled planing surfaces. Getting an L/D of 10 out of these is not going to be easy.

With regard to compensating for heeling and pitching moments, this will dictate much of the craft's configuration. Iron Duck was a semi-symmetrical craft with a symmetrical wing section, but angled wheel fairings and wheel placement. It could sail on both tacks, but sailed better on one tack. Past sailing record breakers, like Crossbow, Yellow Pages, and MacQuarie Innovation are asymmetrical single-tack craft.