Anti Capsize / Damage and Sails

Discussion in 'Multihulls' started by Fanie, Dec 8, 2007.

  1. GTO
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    GTO Senior Member

    Thinking more realistically at the moment, I wonder if the mast head float could be made to work.
    Obviously, the main drawback of attaching a float to the mast head is that it at best gets the boat to, what?, say 100 - 90 degrees?

    So what is really needed is a track or guide cable that the float is attached to, not the mast itself. The track or guide cable attaches to one hull, goes over the top of the mast and attaches to the other hull. I'm thinking of a sausage type float, attached to the track or guide cable in the middle, with two control/stabilizer lines, one on either end, running from one hull to the other, with enough slack to allow the float to roll over the mast head.

    The float is inflated under a hull and slowly pulled down toward the mast, rotating the boat to near vertical. Then the float passes over the mast and is pulled down to the other hull.
    Partial flooding of the lower hull would really help a lot. With a partially flooded hull, seems like if you could maintain about a 60 degree down angle, with the float's assist, you could then pump out the flooded hull and have the boat level out. Some help from a parachute anchor and/or a kite might work too.

    Required float size, stress on rig, etc., would be factors to consider. Boat would certainly have to be designed with this technique in mind, I would think.

    But man, that JATO solution, heck yeah, that would work! WHOOSH...BAM!!!! I like it!!
    Sorry, been to the shooting range. Still happily sensitive to visions of explosives.
     
  2. Fanie
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    Fanie Fanie

    Your car's air bags are situated in small pockets in the steering wheel, dash board, doors and so on.

    If you have on a mast tip a cavity with a similar device that could self inflate, and to such a size that suits the boat size I think one is halfway there. Least it should be able to float the mast comforatably.

    In the case of a capsized mono-hull the yacht would probably begin to self right by the time the mast begins to float upward if it isn't sinking.

    Catamaran will be a different story. If the mast is floating you will have to pull the upper hull over the lower one to get it to want to float upright. Only way I can think of is to flood the lower hull so it would sink down as far as possible or at least enough for the top hull to be dragged over the sunken one, and you can then begin to inflate the sunken hull again.
     
  3. tuks
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    tuks Junior Member

  4. Alan M.
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    Alan M. Senior Member

    It would be very difficult to right a big cruising multihull by lifting one hull over the other.

    In the capsize recoveries I have read about, (which are almost universally racing boats which have been "sailed over" during a race) the boat is turned bow over stern. The back end is usually heavier because of the engine/s, so it naturally tends to sink. I saw one article where a couple of divers righted a cat ( a racing boat which had been capsized during a race) using their airlift bags, initially on the mast, then on the rear beam.

    If you were really paranoid about capsizing, that would be a simpler, more sensible and more useful system to me - carry some SCUBA gear, and a couple of airlift bags. You'll almost certainly never ever be in a position where you need to use them to recover from a capsize, but at least there is the possibility you will get some use out of your investment.
     
  5. Fanie
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    Fanie Fanie

    Actually Alan, the thread originated with me enquiring about a revolving cleat (currently not existing yet :D) with a clutch to let the sail out since wind is the most likely to capsize a craft if cought unexpected.

    Under normal circumstances it is highly unlikely a cat would flip over.
     
  6. Richard Atkin
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    Richard Atkin atn_atkin@hotmail.com

    Fanie, I've read that it takes a HUGE amount of wind to capsize a well designed cruising cat in the way that you describe. On a racing cat the crew are always on standby....so if they are still blown over, without pitchpoling, then they should try to improve their sailing skills.

    I would like a sheet realease system on my CRUISING cat, if it can be reliable, for beaching or for just sheer laziness when a hurricane tips over my already reefed sail.
     
  7. Richard Woods
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    Richard Woods Woods Designs

    The 30ft Iroquois, designed in 1966, originally had a masthead float, but you don't see many with them still fitted these days. One reason was that it raised the C of G significantly which added to pitching when sailing. Another is that they didn't work too well, (often the mast broke). Finally they put a lot of people off buying the Iroquois in the first place. I think the earlier Prout 19 and Prout 27 also had masthead floats.

    In the late 1970's I was working for Derek Kelsall and we built and tested a 35ft self righting catamaran. It worked, but there were many compromises to the design to make it self right. So it wasn't that successful as a cruising boat. However, I saw it a couple of years ago in the Caribbean so it is still around.

    I am sure Derek Kelsall can tell you more.

    Again back in the 1970's, several people designed quick release sheet mechanisms (eg Hugo Myers, Lars Oudrup etc). Hepplewaite Marine sold an electronic version. The problem with all of them was that they tended to release the sheets when you were just driving hard and not when on the point of capsize. Or they released when the boat was thrown sideways by a large wave.

    So they never became popular.

    One alternative idea was to have a weak break link in the mainsheet or in the mainhalyard. But again they tended to release when you didn't want them to.

    Richard Woods

    www.sailingcatamarans.com
     
  8. Fanie
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    Fanie Fanie

    Thanks Richard, some nice comments.

    Wrt the sheet release, there may still be some merit in looking into it again, technology has bettered since the 70's. Some built-in hysteresis would solve the release when just driving hard. Also if adjustable you could set the release limit. Maybe not perfect since more than one factor could still result in a problem situation, but in part a solution still.
     
  9. DungBeetle
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    DungBeetle Junior Member

    Fanie,
    i went looking for exactly what you are talking about and found some. but didn't bookmark them because i'm years off building. they were hard to find though.



    but you are 100% correct.

    cat rigging already has huge safety factor built in, ie reef at say 20 knots, which equals 150 Kg for me.

    cheapest thing i can think of is a clamcleat with a spring to hold it down and a small screw under the trip that you adjust yourself

    for me, i'll set it to trip around 150 Kg (block and tackle 1:3) (and not let out all the way but just let out till the force drops below 150 Kg again)


    cheap to try! comforting!
     
  10. Meanz Beanz
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    Meanz Beanz Boom Doom Gloom Boom

  11. masalai
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    masalai masalai

    I agree Heinz, A great big rubarb like this :p :p :p :p :D
    . . It will eventually get through that self releasing cleats are similar to no hand arms. Fcuking useless
     
  12. DungBeetle
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    DungBeetle Junior Member

    why useless?

    (because i definitely intend to buy one of the three versions i've found)

    (because i read some insurance guy's web site saying most catamaran capsizes were caused by a sudden gust of wind that just happens so fast (probably while the watch was busy looking for the corkscrew)

    so to me it sounds exactly the same as putting fuses in a house circuit.
     
  13. DGreenwood
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    DGreenwood Senior Member

    What makes you so sure that a sheet release doesn't exist. They have been around for years in different forms. Ocean Challenges designed one for Castorama. Never used because of rules. This one was designed for ORMAS>

    Sheet release 1.jpg

    sheet release.jpg

    Photos from the Daily Sail
     
  14. Meanz Beanz
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    Meanz Beanz Boom Doom Gloom Boom

    Most large cats go over their nose, pitchpole, at sea. Small boats go over sideways (off the beach). That is unless you are talking about relativity highly powered racing machines, by that I mean 25+ feet and can still fly a hull. For any self releasing cleat to be effective it would have to be adjustable to release at a predetermine load (unique to your design/load). Personally I would not trust it and would not put myself in the situation where I need to trust it, give me a helmsman's right hand over any contraption, any day.
     

  15. Fanie
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    Fanie Fanie

    I think such a device would work great.

    The guy who is actively racing would probably not use it since he has some control with the rudder and can let sail out if required. Remember this guy is on top of his things, manually controlling his craft.

    The cruiser (where everyone is looking for the corkscrew ;)) or lazing about has set their sails and is underway. They may be socializing and not concentrating on optimum performance. May even have the autocruise on. This is the guys that would use a release cleat to compemsate for the unexpected. When a sudden gust of wind let the sail out some, nothing is lost. They can at their lesure adjust the sail back and continue looking for the corkscrew.
     
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