why masts and not kites on multi's

Discussion in 'Multihulls' started by nota, Aug 14, 2013.

  1. nota
    Joined: Sep 2012
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    nota Junior Member

    why are more boats not using kites that limit heeling/capsize
    instead of old style masts ?

    how close winded are kites ?

    what is the cost of bigger kites vs masts and sail rigs
  2. champ0815
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    champ0815 Senior Member

    Kites are a tempting vision as replacement for conventional sails, aren't they? I have lost a few thoughts on that topic:
    Not much hardware, airflow undisturbed and faster than on the ground... .
    But: Doubtful upwind performance, starting and retrieving on the water, constant monitoring and adjusting required.
    Well, just theoretical thoughts - maybe here's some experienced kite surfer who can bring some light into the matter.
  3. thudpucker
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    thudpucker Senior Member

    Maybe some Ice boat people have tried those Kites?
  4. Petros
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    Petros Senior Member

    seems to me that it would take constant attention with a very high work load, and under many heavy weather conditions would be uncontrollable.

    If the purpose of a sailboat was to get there faster than why does not everyone have high performance cats or tris? If you are in a hurry to get somewhere than do not use a sailboat to get there. It is actually much faster and cheaper to get somewhere by commercial transport, the act of sailing is the activity itself. complicating it by fighting with a kite the whole time would be a lot of effort to gain what? A few knots, and few miles saved at the end of the day?

    I guess it comes down to the reason you go sailing.
  5. Richard Woods
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    Richard Woods Woods Designs

    I think the biggest problem is that they are not fit and forget. You have to actually "sail" them all the time. Not sure how many kite surfers go out in the dark.

    Also the kites and strings take up a lot of water, so your boat is bigger than it looks to oncoming boats. So is dangerous in crowded waters. A kite board is bad enough

    Richard Woods
  6. warwick
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    warwick Senior Member

    Slightly off topic, but still applicable. When Saveol was dismasted in the vendee globe race, part of the return trip was done using a kite when sailing back. It was tied as part of an future emergency kit. There may be more in the link http://www.saveol-samdavies.com/ it has been a while since I had red it.
  7. nota
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    nota Junior Member

    I have very limited kite watching on the local beaches

    and some cat ownership several hobie 18 and a poly-con 31

    and some how think cats and kites are a natural pair

    sure lots of early development work to do both to the kites and the boats
    for control and stability improvements

    maybe computers and el motors to play the lines in real time

    but looks more promising for off shore passages then beer can races
  8. champ0815
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    champ0815 Senior Member

    Seems to me like my objections are not to far fetched... .
    As for the "sail them all the time" it would be at least desirable if a kite has a stable "park position" in the air, were it hovers above the boat happily on its own, before you pick up the lines and move on.
    Maybe a kite could be useful as an additional downwind sail, deployed from the mast top, like a spi on very long lines.
    For the real limits and advantages of a kite I would still like to hear the opinion of someone with hands on experience.
  9. SteveMellet
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    SteveMellet Senior Member

    I think it depends largely on the size of the experiment. You can put a 14-21sqm kite up on a Hobie 18 / Tornado / any catamaran with daggerboards, and you should be able to sail upwind reasonably well, perhaps not as high as a conventional rig, but with much less heeling and capsize tendencies. The course-racing kitesurfers are actually very close-winded, proven a while back when a race was held between a kite, moth and 49er - the kite beat the moth to the windward mark, while the 49er was looking very unhappy about halfway up the beat it was so far behind.
    The advantage of the kite is clear in very strong winds going downwind - the platform remains safe with a bow-up attitude and there is no imminent pitchpole associated with a conventional rig.
    If you use a normal kite system ie lines and bar designed for kitesurfing and hook up the loop to the front beam, the loads are taken by the boat, and the crew only has to deal with steering the kite - yes the steering loads are higher than kitesurfing so it will be a workout. It's not for single-handed sailing as someone needs to decide which way the boat should go while another tends to the kite.
    I think it will have an application in recreational / racing sailing but not as a cruising solution as it is hands-on, but then in small catamarans you are always working the mainsheet if you want to get the best out of the boat or just stay upright.
    The more modern kites will park overhead if you release the bar and be stable facing into wind, but the boat moving under it may load up one side and cause a dive, which if unattended could end up in a series of kiteloops - very good for adrenalin.
  10. SteveMellet
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    SteveMellet Senior Member

  11. groper
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    groper Senior Member

    I have been kitesurfing for in excess of 10 years... i have also done done alot of cruising sailing...

    High L/D Kites, like the kite surfing kites, are not suited to cruising sailing because of the need for constant flight control. If the kites are left to "park" in a position, they do not generate the high thrust possible if they are flown through the wind window at much higher apparent wind. The ability of a kite like this to fly through the wind window at great apparent wind speed, allows these types of kites to generate tremendous amounts of power for their size, upto circa 27 times a traditional sail of the same size in fact...

    So your also left with a max/min problem. If the kite is to be "parked" it needs to be very large to generate large lift at slow speeds. If the huge kite then inadvertantly gets "flown" through the wind window, tremendous forces result and things break, or worse... If the kite is to remain small, for safety, then it need to be actively flown to generate useful power.

    There is also the problem of minimum wind speed. These kites generally need at least 10kts of wind just to get them into the air, they wont stay in the air if the wind drops out.

    Launch and retrieval is also difficult, although not unsolvable. However relaunching a a kite off the water is extremely difficult in marginally light winds. In strong winds, relaunching a kite is less difficult, but it gets much more dangerous and unpredictable with potential for things to go wrong and strong sudden loads.

    The main problem which needs to be solved, is the automatic flight control part of it. A computer control system would need to be perfected so it was almost as intuitive as a human. This is most surely possible, its just that noone has done it yet, although it looked like skysails came close before the money dried up...

    One of the kite designers published this on the web, and it echoes my sentiments pretty much exactly => http://peterlynnhimself.com/Kites_For_Yachts.php
  12. Munter
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    Munter Amateur

    Yes, adding kites looks simple but when you actually use a kitesurfing kite you learn about how important the active control of the kite actually is and how dangerous the power can be. Any kite used on a boat will need a very reliable depowering mechanism as you can't just use the kitesurfing alternative of being thrown 10m downwind to relieve the pressure. Kiters can balance power through board angle and side slip and taking this option away means that all the depowering needs to come from the kite itself. This was not a fully solved kite design problem last time I checked though bridled and bow kites were a good step forward.
    Recovery and crash worthiness are two additional issues that would need to be solved. In short, I think kites for boats would need to be quite different to kites for kitesurfing.
  13. Doug Lord
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    Doug Lord Flight Ready

  14. Angélique
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    Angélique aka Angel (only by name)

  15. HASYB
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    HASYB Senior Member

    On Adastra, the awards winning power trimaran designed by John Shuttleworth, they originally planned a kite to help power the boat in suitable conditions.
    So far, reinforcements for kiting are fitted, they opted out because the known technology isn't yet on the level that it is practical to use.
    I guess kite flying (on multihulls) still is much unexplored territory with the best applications yet to come.

    Probably a bit dated but here's a report of flying a kite on the trimaran Alacrity after she broke her mast.

    Attached Files:

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