kite for powerboat?

Discussion in 'Boat Design' started by pabble, May 25, 2006.

  1. pabble
    Joined: Nov 2004
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: iowa and hawaii

    pabble Junior Member

    I've been researching the idea of using a kite such as those used for kite boarding, or those that are promoted by at kiteship.com by Dave Culp, for long distance power (ocean crossing) on a 30' rigid inflatable boat. the boats primary power are twin 300hp diesels turning jet drives. I can easily fit a rudder and leeboard(s) to give some direction and resistance. high speed or performance are not my goals...distance and low cost are - if I could pull the boat near downwind in the trades at 5 knots I would be very satisfied.

    my inquiries so far suggest that one of these kites could provide the pull necessary, but they seem to require so much attention to keep in the air that they would not be practical for 24/7 flying.

    I would appreciate any comments or thoughts on an appropriate setup and kite. thanks.
     
  2. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 184, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

  3. pabble
    Joined: Nov 2004
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: iowa and hawaii

    pabble Junior Member

    thanks very much for your reply. I've been in communication with Dave, but as I read the actual reports on his forum it seems there are always multiple crew involved and people are excited if they fly the kite for more than an hour or two without a crash and relaunch - these reports are for sailboats with racing in mind and I realize are not necessarily what might be expected with a powerboat application like mine. It does look like the best option so far though, and I will definately try it if I find nothing else.

    the skysail kites look great, but unfortunately the smallest application is for vessels more than twice the size of mine.

    I've spent a lot of time watching the kite board/surfing design and it seems more manageable...have you or other readers had any experience using either?
     
  4. marshmat
    Joined: Apr 2005
    Posts: 4,127
    Likes: 146, Points: 0, Legacy Rep: 2043
    Location: Ontario

    marshmat Senior Member

    The kite-boards look pretty manageable, but I rarely see any around here stay up for more than six to ten minutes. What you're after is not a very traditional setup- this is new, cutting-edge stuff and you might end up either making radical modifications to an existing design, or starting from scratch on a new one.
     
  5. frosh
    Joined: Jan 2005
    Posts: 621
    Likes: 14, Points: 0, Legacy Rep: 44
    Location: AUSTRALIA

    frosh Senior Member

    Have you considered setting up a thwart at deck level with a hole in the middle and placing a 2 or 3 piece carbon unstayed mast through? The mast can be simply pulled out, broken down to its shorter components and stored on board easily when not required.
    From the mast you can fly say a 150-200 sq. ft. parachute spinnaker off a short spinnaker pole. This will give you at least 5 knots if you boat is fairly light in medium winds, and at a range of 45 degrees either side of dead downwind. No launching or crashing problems! Second hand parachute spins are cheap, and you can probably source the mast second hand also if you are on a limited budget. :)
     
  6. fcfc
    Joined: Feb 2005
    Posts: 778
    Likes: 29, Points: 28, Legacy Rep: 399
    Location: france,europe

    fcfc Senior Member

  7. Poida
    Joined: Apr 2006
    Posts: 1,189
    Likes: 50, Points: 48, Legacy Rep: 497
    Location: Australia

    Poida Senior Member

    Wot's the difference between kites and a sail? My thinking is kites are used on craft that are too small to fit a sail ie suirf boards. I have also seen a documentry where kites were used to power a snow sled. Not only faster than dogs but in the situation where there is a snow covered ravine the upward thrust of the kite enabled the sledder to virtually fly over the ravine to safety.

    Which has nothing to do with boats.

    A kite seems to always need adjustments by the user to compensate for wind velocity and I think wind spillage from the kite.

    I have no idea what I'm talking about here!!

    To maintain the correct kite control manouvers I would think a rather elaborate set of sensors and compensators would be needed to make the neccesary adjustments to the kite strings.

    Also kite surfing requires the surfer to tack against the kite to keep the kite strings tight. A boat going in the same direction as the kite would probably slacken the control strings with the result, the kite would nose dive.

    Please note everything I have tried to make, design or modify has not worked this week, so please do not take any notice of anything I write here.

    I'm thinking that a wind sock type of configeration might be more successful, perhaps it would line itself up with the wind and this only leaves the up and down control.

    Maybe four control strings. Two horizontal which forms the axis on which the opening of the windsock moves and two on the vertical plane which will pull or slacken off to the alter the attitude of the windsock opening to lift or lower it.

    The lower string would be attached to a shaft that revolves in acordance to the angle of the windsock. An encoder at the end of the shaft would transmit the info to a linear motor that will pull or slacken off in relation to the signal received, thus keeping the windsock airborne.

    And it probably won't work. Like every other bloody thing I have done this week!!
     
  8. tighkey
    Joined: May 2006
    Posts: 20
    Likes: 1, Points: 0, Legacy Rep: 24
    Location: TOKYO, JAPAN

    tighkey Junior Member

  9. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 184, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    I have been with the people of SkySails this week and their system looks quite appealing. They've tested it first on a 4 m boat, then a two ton model ship, a 20 ton yacht, a 30 m fishing-research vessel and now they're installing a 160 sqm model on the cargo ship "Beluga" for commercial operation.

    They claim an average of 1 kW per sqm under conditions:

    Wind speed 10.5 m/s (25 knots)
    True wind direction 130°
    Ship speed 5.14 m/s (10 knots)
    Sea State 2
    Flight mode of towing kite Dynamic

    My good old 13 tonner motorsailer "Marie" with a 40 sqm kite (54.4 HP) would have a sail power equivalent to that of her engine. Even with a 25 sqm one would be enough to reach her hull speed. And probably the steadying upwards thrust would efficiently dampen down her rolling when in a following sea. Mmmm...have to think about it.
     
  10. pabble
    Joined: Nov 2004
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: iowa and hawaii

    pabble Junior Member

    thanks again for the replies...

    Frosh and Poida....I've experienced using a small emergency rig with mast on a 24' Zodiac in mid ocean, using a small main, jib, genoa and spinnaker. The idea can definately work. I was able to use the standing rig easily but the spinnaker was problematic - but the obvious main problem was the absence of a keel and rudder of any substance. That rig was for emergency only, and was useful for that purpose but was clumsy for a primary rig. The rudder problem can be solved, and it seems leeboard(s) could meet the lateral resistance requirement. This experience is what prompted my current interest - and I'm just curious how well a kite might work.

    Poida, the sock idea sounds very creative but I would prefer to start with a system already in the air because of my limited knowledge in this field. If you make one please let me know...would love to give it a try!

    The discussion Dave Culp and others give about the benefits of a kite over spinnaker, especially for my needs, is persuasive and has moved me in that direction. I'm particularly infuenced by the tendency of the kites to fly higher than a spinnaker, creating a nice/safe upward pull and accessing stronger winds. But I have no personal experience with them so am in no position to present the merits of any option at this point.

    Guillermo.....I re-contacted SkySails and received this reply; "...At the moment SkySails is focussing on the development of Systems for cargo vessels which could also be used on large yachts (> 24m). Therefore I'm afraid we cannot offer a system for your boat at the moment. Nevertheless it is planned to scale down the system for the use on smaller boats later on." So, although it sounds like a great choice, the timing isn't right.

    tighkey and fcfc......these links are very helpful and informative - makes me think this might really be practical. I've contacted both of the recommeded sources for info and help.

    marshmat....It does seem like my purpose is outside what developers have been focusing on (for obvious reasons - who would want to cross an ocean in a little powerboat using a sail?!). But I'm hopeful the low performance standards acceptable to me might help in finding a kite that fits.

    thanks again for all your help......am looking for any ideas and references I can get, and the knowledge here is impressive....
     
  11. Poida
    Joined: Apr 2006
    Posts: 1,189
    Likes: 50, Points: 48, Legacy Rep: 497
    Location: Australia

    Poida Senior Member

    The windsock idea was not to use it as is but to modify it to suit what you are after.

    The way I see it sails on are a boat are controlled, ie they can't drift as they are held down. As a yacht keels over the sail is designed to spill wind and therefore has a controlled spillage. Probably not a correct term.

    Kites dart all over the place as they don't have a controlled wind spill and has to be continually corrected, difficult for an automatic system.

    I feel the wind spillage has to be in the centre requiring a conical design probably a square cone, this will provide an even pressure in all directions and hold the kite stationary.

    Not sure about your desirte to have a 45 degree kite. I would have thought a kite as close as practical to sea level would provide more forward thrust. A kite that is going to lift a boat is going to need some serious rigging, too heavy to allow kite flight.

    Thought later a kite with an attached airfoil, as the kite looses altitude it changes the angle of the airfoil providing lift.

    LOL if you use the windsock idea you can use it as a sea anchor while you are fishing.
     
  12. frosh
    Joined: Jan 2005
    Posts: 621
    Likes: 14, Points: 0, Legacy Rep: 44
    Location: AUSTRALIA

    frosh Senior Member

    Hi Pabble, I commend you on all the reasearch you have done on the kite issue and your willingness to do an ocean crossing in a relatively small powerboat.
    My previous posting was from actual experience with my 7 metre OC-2 fitted with a rudder, but otherwise no lateral resistance at all.
    The 65 sq. ft. spinnaker provides plenty of power off the wind and is very easily controlled with one spinnaker sheet, and the rudder of course which is essential. I don't know how you can sail safely without a rudder unless you are on a sailboard, or using a steering oar. :)
     
  13. pabble
    Joined: Nov 2004
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: iowa and hawaii

    pabble Junior Member

    Yes, a rudder will be essential. I'll keep looking online for people exploring this concept and appreciate the continued input on this forum. my boat should be ready for the water in early August so hope to have something to experiment with soon after that.....more ideas and references are welcome.
     
  14. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    Pabble: I believe your requirements are easily met by a stable, high lift single line "pilot kite". It would fly straight downwind of you, at an upward angle ofcourse. There are free plans for a peter lynn designed such, which I have not tried.
    You could set your course relative to the kite by adjusting your tow point or the lateral center of effort in the boat.

    I wonder whether it would be worth it for you to experiment with more versatile, higher performance varieties. It might be a challenge to find a kite that is cheap, can be steered and sheeted with little effort, can hold a tack by itself without drinking, has an appreciable increase in lift to drag ratio, has an acceptably low pull when sweeping through the "downwind eye", and a high enough pull when parked, in the relevant wind range, and finally that can be launched and stowed at sea.
    For hardware useable for launching a kitesurf kite singlehandedly at sea, look at the kite dinghy thread.
     

  15. pabble
    Joined: Nov 2004
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: iowa and hawaii

    pabble Junior Member

    thanks for the info....I've emailed peter lynn and the parent company to see if they think it might work. I think I've already read posts in this forum that might be relevant but will double check with the suggested dinghy thread to be sure. It may be that what I want doesn't exist...but will keep looking. thanks again.
    bryan
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.