# Kite power for boats - boats powerd by kites

Discussion in 'Boat Design' started by 4wings, Jun 18, 2012.

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### 4wingsJunior Member

Ilan -
Thanks for the info - do you think you can get a square-yard to Hp relation on the Omega sail which would help interested persons to pinpoint the appropriate size they need for their application - without overpowering their boat.
I see that kayak user are the quick driving force behind kite and alternative sails as their out of pocket expense is in a reasonable wind window in case it is down the wind ...lol

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### Ilan VoyagerSenior Member

A video with the Omega sail and kayak. Visibly the guy is not struggling to control the sail. The wind is moderate.

In the Internet site the recommendations are the following;
Motor Yachts
Length meters 5 8 11 14 16
Surface sail 20 40 60 90 120
traction kg@20 knots 210 400 600 950 1300
wind

The differential of speed between the boat and the sail must be mini 7 knots. The sail works from 12-15 knots to 30 knots of wind.

I think these are static tractions, measures taken surely on a beach. That's consistent with speeds about 5-6 knots and a bit more. Knowing the tractions at 20 knots it's easy to calculate the statics at 15, 25 and 30 knots of wind.

The guy gives tractions which are more consistent than HP for calculating the possible speed. It's easy to calculate the real "pushing" force of a propeller at a given speed (it's equal at the total of the resistances...) and extrapolate. With tractions you eliminate the problems of losses factors, efficiency coefficients and tutti quanti. Just bare ciphers.

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### VerticaliftNew Member

Kite System for Grady-White in Phuket Thailand

Purchasing a Grady-White 225 Tournament in Singapore last year, I moved the boat up to its new home in Phuket, Thailand. Plans are to rig the boat with a kite system from "Kiteboat Systems" in Germany.
Have a look at these links:

http://www.kite-boat-systems.com/

http://www.kite-boat-systems.com/index.php?option=com_content&view=article&id=134&Itemid=144&lang=en

Cost for the Kiteboat Rescue System is about 1,800 Euros / \$2,300USD

Having previously owned and lived aboard a Passport 40 in S.E. Asia, I'm looking forward to powering up my little Grady-White with a kite. Should be great fun. Kites make perfect sense for all boat owners, both power and sail.

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### 4wingsJunior Member

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### SpartanJunior Member

I have an interest in small cargo ships (10k) ever since I worked on one for a month back in my teens. Yup, a career of ONE month....LOL!

Bitten by the willfully fond memories of four decades back...

I thought about alternative ways to power my fantasy cargo ship including wind, solar and kites. In the end, I think that the old tried and proven sail technology is the only thing that is robust enough and controllable enough to have any real traction. In my opinion, given cost of crews and need to make money by constantly moving cargo, it's not a replacement, but rather, additions to the main propulsion.

Here is a kite on a ship.

~~~~~~~~~~

BTW...does anyone know how to calculate wind power from sails? I can do a pretty accurate job on calculating wind turbine and solar number but I'm lost on sails.

Just for the record on solar....this is what solar look like on a 16mx100m 10K ton ship.

150wm2 at 16mx100m at 70% ship coverage and 1200 hours yearly of rated output and 85% net after DC/AC conversion and wire loses. Equals to about.....171,360kw. Or about 584,704,653 btu. Or about 14.7 tons of oil. Invert this at 50% diesel engine yield and you get about 29.4 tons of oil OR about 3 days sailing. 29.4 tons cost \$19,000 and 170 kw solar system cost about \$400k, for deck mounted system. Adding all the problems, plus secondary drives, it doesn't make sense to do this to get 1% of the ship energy needs. So next time you get some greenwashigng article spouting solar powered ships.....try to control the laughter.

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### projetdaredJunior Member

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### 4wingsJunior Member

Kitewing appears as a hybrid

For all who have interest in kite-boating - this appears as a interesting hybrid between kite / glider and windsurfer sail ...
http://www.kitewing.com/
Just missing some lines to fly it high
All the best
Michael
http://kite-sailer.com/

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I am designing a 40ft catamaran and looking into kite propulsion.
It is nice to see the discussion, but quite disappointing that so many years have past and there isn't really a good solution available. A kite should be very inexpensive, much less than a traditional mast/sails, so anything that isn't is a failure in my opinion.

While I can understand the desire to maximize the wind direction for propulsion, it seems to me this introduces significant complication. I would be quite happy to have a simple system which works mostly for downwind operation. I am happy to use motor power on other points of sail.

I am thinking for downwind use, a simple set of helium balloons will get the job done.
Say 1-5 of them, how many deployed depending on wind speeds. They would be dirt simple drag devices. Has it been tried?

JackB

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### rasorincSenior Member

Is a circle (balloon) the best shape to catch and hold wind so it can be pushed forward
by the wind? I do not know the answer that is why I pose the queston.

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No of course not. It is however a very inexpensive shape to make and hold hydrogen. It might work to have the balloon hold up a sheet attached to the boat with lines. A sail if you will, the balloon(s) as the "mast".

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### philSweetSenior Member

The obvious problem with a balloon is that the pull is only the net lift times the tangent of the angle from vertical. You would need something like a 10,000 cu ft balloon (27 ft dia) at 30 degrees from the horizon to get 100# of thrust, which would only happen at exactly one smallish wind speed. As windspeed increased, the balloon would fall lower and lower. Balloons don't make very good masts.

So calculate the elevation angle as a function of apparent wind speed and balloon diameter and see what you get. <edit. The h2 lift goes as r^3, the shell area goes as r^2, and the shell thickness goes as r if overpressure is constant. The drag force goes as r^2 or so >

You could motor a fair distance burning 25 pounds of h2.

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Right, a balloon would just be pushed down to the ground as it creates no lift.
However, it might solve the launch and retrieval problem. As I see it, the major problem of any kite is what happens when the wind dies and it plummets into the sea? Particularly if you have a long tether. Now you have a serious problem.

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### SaildudeJunior Member

The kites that kite boarders use have some inflatable sections - add stiffness and when they do land on the water they float -yes the lines in the water are an issue for a boat picking the kite up -

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### alan whiteSenior Member

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### kach22iArchitect

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