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  #61  
Old 07-13-2015, 10:59 PM
whitepointer23 whitepointer23 is offline
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Quote:
Originally Posted by Skyak View Post
The reason for the rant is the original claims of the commercial kite boat. I am angry that they present it as such a smart simple solution. Classic accentuate the positive and just look at them blankly when they ask what happens in less than perfect conditions. I also don't like these
"First Crossing of (insert ocean here) with (insert stupid dangerous propulsion method here) only!" stories which I see this indicating. I would be happy if all of them were required to post bond based on how stupid and dangerous their attempt was.

The Rant was labeled, you were warned, and I think the comparison of the sport bike to the windsurf kite was apt.

Big kite surf kites are about $3k and they are built to about 1000lb strength. Typical lines are 600lb tensile aramid fiber because elasticity is a major control problem. No tension=no control of a kite. When one end or the other gets yanked toward the other, control is lost until tension is reestablished. While there is no control the kite can (and usually does) find a way to give an even bigger yank! Search "kite board teabag" to see what I mean. Anyway, the point is that the $4000 kite and lines are designed to pull a ~200lb boarder, not a 500 to 2000lb displacement boat so it will not last as long and kites do not last as long as sails when used as recommended. There are very talented armature kite builders. I wonder what they would say if you told them you want to pull a 1000lb disp. boat. Beyond the problem of breaking the kite there is the problem of breaking something else. Up in the sky there are gusts and swirls far greater than at the surface. If you leave this foil up long enough something terrible will find it eventually. You need a plan for this to beak safely.

Anyway feel free to brainstorm. But do state what you expect to get out of it and do some calculations.
This reads like another rant. Why all the agro.
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  #62  
Old 07-15-2015, 02:03 AM
rob denney rob denney is offline
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We are playing with a 7.5m kite powered proa as a stepping stone to a 15m offshore race version. (see short video at harryproa.com, second button at the bottom of the screen).

Light air is one of many things to be overcome with offshore capable kite boats.
There are kites (Ozone Chrono. Flysurf Peak) that will launch and fly in 3 knots of breeze. Generally, but not always, wind sheer means that even when there is no breeze at the water surface, there is some 30+ metres up.

Our solution is to fit pedal driven props to the boat, which will drive it at 4 knots to get the kite up into the stronger air. With double or triple length lines, there should be enough wind to drive the boat. Long lines are another set of problems, (drag and sag), but not insurmountable.

Other things to try are black upper surfaces on large ram air kites to heat the air inside, very light lines, ie dental floss to get the kite up, then pull through the flying lines and a telescoping mast.
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  #63  
Old 07-15-2015, 03:45 AM
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Manie B Manie B is offline
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Rob I absolutely love your work and your site
stunning

http://harryproa.com/

cheers
Manie
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  #64  
Old 07-21-2015, 07:22 AM
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Angélique Angélique is offline
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Irish Navy starts Kite Sailing . . .

- Ship & Bunker (February 9, 2012): Military to Use Wind Power to Cut Bunker Costs

- Ship & Bunker (July 17, 2015): Irish Navy to Begin Commercialising Fuel Saving Kite Technology - - (copy paste)

- seai - Sustainable Energy Authority of Ireland (11th July 2015): Defence Forces Unveil Innovative Ship-Mounted Kite System at SeaFest

Of course a different ball game as their main propulsion remains the engine, so calms aren't a problem for them. But maybe some info can be gained from the systems and kites they use and their handling of sudden squalls that can tear up the kite and destroy the control systems. But of their solutions for those problems I haven't read anything yet . .
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Last edited by Angélique : 07-22-2015 at 07:56 AM. Reason: spelling
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  #65  
Old 07-21-2015, 08:56 AM
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Angélique Angélique is offline
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Quote:
Originally Posted by Skyak View Post

[ . . . . ] The keel boats the kite boat compared itself to can take a huge gust with just a knockdown and recover intact automatically unattended. I have yet to see a kite setup that could do any better than a complete loss of propulsion (lost kite) and most would suffer structural damage and loss of directional control. Kites are intrinsically weak due to the need to keep mass low for flight and control. Weight and control problems are also the reason that no kites are reefable. Different wind speed requires a different kite. Granted this is all about what has been done in the past while this blog is brainstorming what could be done in the future, but when you get to making real kites I think you will find the current state of the art very difficult to improve. Launch and retrieval could be improved, reefing will be a problem. Even feathering kites is limited because the kite uses lift to maintain shape and control. Low wind is the first problem of kite primary propulsion, but coping with sudden changes in wind speed and direction will be the next.
In post #52 Skyak introduced how to handle sudden squalls as another major issue for Ocean Kite Sailing, which is at least as important as how to deal with light airs . .

I therefore would like to add this issue to the thread title and will ask the Moderator to do so.

But this would be the second title change, so I can comprehend if this would be to much.

The suggested new thread title is:
Ocean Kite Sailing -- How to solve the problems with very light airs and sudden squalls ?
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  #66  
Old 07-22-2015, 01:23 AM
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Angélique Angélique is offline
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Many thanks to the Moderator for updating the thread title
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  #67  
Old 07-22-2015, 07:09 AM
rob denney rob denney is offline
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Quote:
Originally Posted by Angélique
Skyak introduced how to handle sudden squalls as another major issue for Ocean Kite Sailing, which is at least as important as how to deal with light airs . .
Assuming the kite is controlled, the limits to the size and power of a kite on a proa and some other boats are very high. The kite is attached to the lee hull with the leeway resister (foil) in the weather hull, so there are no heeling forces. Boat speed increases until the side load gets too large for the foil which stalls and the boat goes sideways.

In a sudden squall, the choices would be
1) Control the kite with enough power to keep the boat sailing with the option of complete depower with the kite at the edge of the window but still flying. This is no problem for a competent kiter and has low loads.
2) Boat recovery. This depends on the kite. With a Peter Lynn autozenithing kite (dump the lines and the kite flies directly overhead, applying little or no power), it is a simple exercise to pull it down and onto the boat, open a vent and collapse the kite. Good line handling equipment (reel or similar) helps. It is also possible to boat recover a leading edge inflatable kite, but the gear needs to be able to handle significant loads and control the brake lines independently.
3) Water recovery. With a single skin kite, it is landed on the water, collapses and the lines are pulled in. Very safe, simple and tidy. With a leading edge inflatable three lines are released and the kite pulled in on the 4th line. The kite tends to fly in circles at the end of the line, tangling the lines. One solution to this is a fifth line on the kite, which allows us to land the kite on it's top surface, then pull it in regardless of wind strength.

The problem with kites is not when they are doing what they should, but when, due to operator error or a lousy set up, they get out of control. A knife or quick release system, ideally on a fuse, is then the best solution. Unlike sails, which keep flogging, a kite in the water on a single string is usually pretty benign.

Manie,
Thanks, glad you like it.

rob
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  #68  
Old 07-22-2015, 08:09 AM
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Angélique Angélique is offline
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Thanks Rob, for the explanation how to handle sudden squalls when kite sailing with a boat.

But operator errors do happen, on a self righting boat with a mast and to much sail up a huge gust will cause a knock down, after which the boat automatically recovers and you only have to clean up the mess in the galley. As this thread is about Ocean Kite Sailing one has to sleep too, so when sailing single handed the boat has to be able to sail unattended for periods, then would an operator error with to much sail up in a huge gust cause damage on the kite ?
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  #69  
Old 07-22-2015, 12:45 PM
markstrimaran markstrimaran is offline
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Perhaps a Ram air sky diving parachute. I know they stay aloft in light winds. They would have to be kept out of the water. A 10 foot spar for launching. Interesting post. Ever tried to fly a kite side ways? From a mast like a sailboat.
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  #70  
Old 07-22-2015, 09:42 PM
sharpii2 sharpii2 is offline
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Quote:
Originally Posted by rob denney View Post
We are playing with a 7.5m kite powered proa as a stepping stone to a 15m offshore race version. (see short video at harryproa.com, second button at the bottom of the screen).

Light air is one of many things to be overcome with offshore capable kite boats.
There are kites (Ozone Chrono. Flysurf Peak) that will launch and fly in 3 knots of breeze. Generally, but not always, wind sheer means that even when there is no breeze at the water surface, there is some 30+ metres up.

Our solution is to fit pedal driven props to the boat, which will drive it at 4 knots to get the kite up into the stronger air. With double or triple length lines, there should be enough wind to drive the boat. Long lines are another set of problems, (drag and sag), but not insurmountable.

Other things to try are black upper surfaces on large ram air kites to heat the air inside, very light lines, ie dental floss to get the kite up, then pull through the flying lines and a telescoping mast.
This is a fine sounding solution on paper, but in real life, it may lead to an ocean of frustration.

You get the kite up in the air. You get the actual flying lines to it. The wind poops out.

Down comes the kite.

You start the process all over again, but this time with a wet kite. Maybe this time you get a gust, while launching the kite. The dental floss breaks and the kite sails away for several miles. Now you have to pedal to the kite to start the whole process over again.

After this happens a few times, you stow the damned kite and simply pedal towards your destination.

This is why I found the notion of a gas filled kite so attractive. It stays up in the air even with no wind at all. This is what you need.

The problem is that it takes a lot of lifting gas to lift even a very modest amount of weight.

To make THIS at all practical, it had to be a one-does-it-all system, like I proposed in an earlier post. The balloon is the kite, is the sail. It is flown like a sail from a stubby mast, sometimes, and sometimes it's flown high above the boat.

This way, it never has to be stowed, and the gas in it stays in it, hopefully throughout the voyage.

BTW--I really admire your work with the "Harry Proa". I think it is one of the most underrated creations in contemporary sailing.
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  #71  
Old 07-23-2015, 09:01 AM
Skyak Skyak is offline
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Quote:
Originally Posted by rob denney View Post
Assuming the kite is controlled, the limits to the size and power of a kite on a proa and some other boats are very high. The kite is attached to the lee hull with the leeway resister (foil) in the weather hull, so there are no heeling forces. Boat speed increases until the side load gets too large for the foil which stalls and the boat goes sideways.

In a sudden squall, the choices would be
1) Control the kite with enough power to keep the boat sailing with the option of complete depower with the kite at the edge of the window but still flying. This is no problem for a competent kiter and has low loads.
2) Boat recovery. This depends on the kite. With a Peter Lynn autozenithing kite (dump the lines and the kite flies directly overhead, applying little or no power), it is a simple exercise to pull it down and onto the boat, open a vent and collapse the kite. Good line handling equipment (reel or similar) helps. It is also possible to boat recover a leading edge inflatable kite, but the gear needs to be able to handle significant loads and control the brake lines independently.
3) Water recovery. With a single skin kite, it is landed on the water, collapses and the lines are pulled in. Very safe, simple and tidy. With a leading edge inflatable three lines are released and the kite pulled in on the 4th line. The kite tends to fly in circles at the end of the line, tangling the lines. One solution to this is a fifth line on the kite, which allows us to land the kite on it's top surface, then pull it in regardless of wind strength.

The problem with kites is not when they are doing what they should, but when, due to operator error or a lousy set up, they get out of control. A knife or quick release system, ideally on a fuse, is then the best solution. Unlike sails, which keep flogging, a kite in the water on a single string is usually pretty benign.

Manie,
Thanks, glad you like it.

rob
Pardon the digression (I kind of have to given you reached conclusion) but to start what kind of kite design are you referring to? I was under the impression that the only appropriate C kite for a boat would be an LEI because it is most likely to recover from hitting the water and least likely to become a tangled sea-anchor. I assume three line control and I understand how an extra safety/trip line could be attached so in the case of a large gust the kite would fold up and fall in the water -is this what you are suggesting or is there something better? I had never seen the single skin kite before your link. Can it take off again after hitting the water?

I am also wondering about control. My kites are a full time job. Is there something better? Automatable?

What are your plans at the boat end? Have you found a line handling rig or do you plan to make your own?

I love the idea of human+wind powered boat racing. Are there any existing competitions on your side of the world?
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  #72  
Old 07-23-2015, 09:50 AM
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Angélique Angélique is offline
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Quote:
Originally Posted by Skyak View Post

. . . . I am also wondering about control. My kites are a full time job. Is there something better? Automatable? . . . .
Yes, the flight mode is automatable, at least on Cargo Ships...

SkySails ---> SkySails Marine Kite Wind Propulsion ---> Check the buttons on the left ---> Operation --->

Check the buttons: -- ‘‘Safe & Easy Operation’’ -- ‘‘Launching’’ -- ‘‘Flying’’ -- ‘‘Landing’’ -- ‘‘Crew Training’’ --

From the button ‘‘Flying’’
Quote:
The towing kite is controlled automatically at all times while in flight mode. An autopilot software ensures that the towing kite flies defined patterns based on wind direction and velocity, as well as the speed of the ship, so that it generates optimal propulsion. The SkySails control panel on the bridge keeps the ship's officers informed at all times about the system’s operating status.

SkySails propulsion’s multi-level security and backup systems ensure safe ship operations. Emergency actions can be initiated from the bridge at the press of a button.
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  #73  
Old 07-23-2015, 12:54 PM
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Angélique Angélique is offline
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Rob, in your video I saw you uses an 17.5m ASV Kite, the closest I found was the 17m 2015 XR, is that the one ?

Quote:
- -
This is our best high performance SLE kite ever! Built on 3 years of relentless development and proven on the worldwide Formula and Hydrofoil racing circuits, the 2015 XR is the most advanced inflatable kite on the scene.

For 2015, the XR's bridle and airfoil have been finely tuned to achieve incredible stability and stiffness. The results are a kite with near zero luffing, even in the most powered conditions, allowing the kite to hold shape and airfoil. With a weight reduction of about 6% from last year (not a small achievement), accounts for a much floatier feel when going downwind. The upwind sailing speed of the XR were just unthinkable for inflatables just a couple of years ago.

If you are interested in RAM air kites performances, but don't want to deal with all the drawbacks, the XR 2015 is the answer. It offers all the advantages and safety of an inflatable kite with the closest performances to RAM air that the market can offer.
• Thinner diameter struts and LE [2% weight reduction]
• Light Darcon for leading edge and struts [4% weight reduction on 10m and up.]
• Technoforce ripstop material
• Single point inflation
• Internal leading edge bridle attachments increase rigidity and reduce bridle drag
• Thin, hand spliced bridle material
• Adjustable leading edge arc
• Adjustable bar pressure
• Coming with Inner bag and shoulder bag
• Four color combo
• Size: 6m | 7m | 8.5m | 10m | 13m | 17m
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  #74  
Old 07-23-2015, 12:54 PM
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Angélique Angélique is offline
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In the ASV store I saw also the Get Home Quicker, a Rescue Kite for the VO65 fleet in the Volvo Ocean Race 2014-2105 edition, which looks intersting . .

Quote:
In 2014 we have been challenged with development and delivery of the QXI 'Get Home Quicker' Rescue Kite for the VO65 fleet in the Volvo Ocean Race 2014 - 2105 Edition.

This is the first time that any professional Ocean racing yacht has been equipped with a rescue kite that will help it reach a safe port in the event of the yacht losing its mast or losing control of its swing keel, and so being unable to raise any sails. Ocean Race yachts only carry fuel for less than 200 miles of motoring under power.

We are already working on systems for other classes and have started developing personalized systems for private owned yachts.




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  #75  
Old 07-23-2015, 11:35 PM
rob denney rob denney is offline
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Originally Posted by Angélique View Post
Thanks Rob, for the explanation how to handle sudden squalls when kite sailing with a boat.

But operator errors do happen, on a self righting boat with a mast and to much sail up a huge gust will cause a knock down, after which the boat automatically recovers and you only have to clean up the mess in the galley. As this thread is about Ocean Kite Sailing one has to sleep too, so when sailing single handed the boat has to be able to sail unattended for periods, then would an operator error with to much sail up in a huge gust cause damage on the kite ?
Single handed facing implies automated upwind, no external power kite control. This is a whole new area, in which, as far as I know, no one has made much progress. Best i could offer would be sub 50% performance with the kite on very short strings with one tip pulled down onto the bow. And a fuse that released 2 lines at a certain load.

A strong gust scenario is much less likely to be a kite boat problem for the reasons in my last post. Our problems have occurred testing new set ups (once, the boat was lifted and landed 20m up the beach), and when the operator stops concentrating on the kite, at which time it can unexpectedly fly across the window with a surge of power which the boat or crew were not ready for.

Personally, I would prefer to be on a kite boat rather than a sail boat when things go wrong. Release the safety line and in a couple of seconds the kite is flapping in the water 30m downwind. Pull it in and sort out the tangle (or just shove it in a bag for later and hook up another set) at your leisure. No booms or sails banging around, no mast to fall down, no winches to jam your fingers in and no heeling.

This is a pretty new field and i am yet to go offshore, so my comments should be seen in this light. Our ASV is a 17.5. Very old, but still does the job. Most lei kites are pretty similar, so it is much the same as the new 17.

Mark,
Suspect ram air parachutes don't have high enough L/D to make good traction kites.
We have launched kites off masts. It is pretty easy, and a potential light air option with a very high telescoping mast. But for non light air, they are not necessary. The important thing for boat launching is sufficient distance between the attachment points to constrain the kite until it is flying high enough and a good line control system. The autozenithing kites are much easier than the lei's for this.

Sharpie,
I disagree. The dental floss for lines solution sounds lousy, even on paper! ;-) The black top surface is not much better (although it would help). Both would be worth trying, though, if only to see their limitations.
Tethering a ballon kite to a mast loses a lot of the kite advantages (no capsize moment, no rigging, etc).
Lighter than air has a lot going for it, but a big enough kite to float in air would be too big and/or draggy in normal breeze for most boats, but if you can get something working, or come up with a reasonable plan, I would be only too happy to try it.
Glad you like the harrys. Lots of stuff on the verge of happening with them. Same as always. ;-).

Skyak,
We are nowhere near conclusion. All input is gratefully accepted and any ideas that seem worthwhile, we will try.
The kite in the video is a 17.5 sq m lei.
The autozenith kite, which I prefer is a Peter Lynn Venom, but we only have a 14 sqm so we use the lei for speed related testing. We launch it from the beach which is often fraught. Both are 4 strings, although for the long lines we join the 2 front ones so there are 3 attached to the boat. The single skin kites are not yet available in large sizes, but will also be 4 strings. Not sure if they will autozenith, but I suspect not.

The lei's are much easier to water launch, but the bigger they get, the less easy this becomes. The aim is to keep them out of the water, which is easy enough for a good pilot for shortish periods.

There is a video of a Peak 2 single skin water launch, but I suspect it is not easy.

If the kite has to be jettisoned onto one line (unusual, see above), then an lei will make a bigger tangle as it flies around on one line. The autozenith kites just fold in half and sit, usually. The single skins will crumple and float and be the easiest to recover, I think.

In large gusts, I would try to keep the kite flying at the edge of the window, mostly depowered. If this proved hard, I would fly it overhead and lower it onto the boat (easy with the autozenith, challenging with the others). Last resort is recovering it from the water.

There is no automation for upwind traction kites, as far as I know.

At present, we use a bar to control the lines and and a winch (no handle) for recovery/launch. if we progress to a bigger boat, I have a roller (a complex bit of kit if the lines are under any load) to look after the lines, but will still use the winch to control them. The autozenith kites go up and down on 2 lines with the brake lines slack which is much easier than an lei.

No competitors over here. The giants' shoulders on which we are crouching are Peter Lynn (kite boating in small boats for >30 years) and Don Montague (30+ knots on a hydrofoiled catamaran, plus Google money for experimenting).
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