Best free-standing rig for small, light race-cruise tri?

Discussion in 'Boat Design' started by scotdomergue, Nov 6, 2014.

  1. scotdomergue
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    scotdomergue Scot

    I'm creating a 19' long, 14' beam tri for the Race to Alaska and for cruising thereafter. She'll have two tiny cabins fore/aft and displace under 1000 lbs fully loaded.

    I was going to use a cat-ketch rig with free-standing windsurfer masts. I realize they are awfully bendy for a multi-hull.

    I'm considering a single, free-standing carbon fiber mast with sloop rig. Would that be significantly more efficient and faster?

    Or perhaps the general question: what is the best/fastest un-stayed rig for a tri of this size, carrying perhaps 250 square feet of upwind sail?
     
  2. Petros
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    Petros Senior Member

    Scott,

    consider that all of the world sailing records for long distances are all sloop rigs, it seems to be that is the place to start. these always have conventional jibs with flat top fully battened main sails.

    the only reason you might want something different is for sail handling or simplicity reasons. I am partial to a modified junk rig for simplicity and easy of solo handling. Ideal for a cantilevered unstayed mast. It is efficient all all points of sail except it goes up wind poorly compared to a conventional sloop rig. But I think with some cleaver design to get some camber in the sail you can improve the junk's up wind performance.

    I have been working on a few concepts to make a modified junk even more efficient, and to improve the up wind performance with a simple means to camber the battens. I will be happy to share them with you for this project. I have considered this contest too, but I have too many other projects going right now, but I would be happy to help you develop your design for it.
     
  3. Tiny Turnip
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    Tiny Turnip Senior Member

    I have a 16ft cruising tri with a freestanding bermudan ketch rig, from Solway Dory, who make sailing canoes in the UK. It reefs simply by unhooking the kicking strap and rolling the sail around the mast.



    It carries a modest 75 sq ft of sail. I have had 11.5 knots; the sister boat is reputed to have hit 15 knots.

    They have another, cat rigged iteration of the tri:

    [​IMG]


    I am NO sort of canoey person, but I can paddle the tri at 3.5 knots.

    Colin Archer has been developing his cruising rowboat (with cabin) into a little ketch, and is looking at the possibility of an ama:

    [​IMG]

    Good luck with the adventure - I'm very envious! If I lived on your side of the pond and had more experience and ability I'd be joining you!
     
  4. philSweet
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    philSweet Senior Member

    One of the (few;)) things I like about tris is the ability to support a stayed rig in a sensible manner. If you think about the beam load of the lee aka, why not employ that strength on the windward side to do something useful. I'd prefer to put heavy structures to use all the time, not just half the time.

    JosephT sent me this link a few days ago - semistayed carbon.

    http://www.scandinaviancruisers.com/Yachts/The-Scandinavian-Cruiser-20.html

    I like the carbon rig here as well -

    http://areyspondboatyard.com/apby-built-boats/daysailer-18/

    <link working now>
     
  5. Nick_Sinev
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    Nick_Sinev Junior Member

    Almost a spam – sorry for advertising my ideas.

    Once I have offered a strange concept of a fully-rotating rig. Nothing like this was ever built, the general opinion of the forum members about my ideas was sceptical.
    Anyway, you could have a look at the pictures in the discussion http://www.boatdesign.net/forums/projects-proposals/hybrid-catamaran-sailboard-51190.html

    The concept could be simplified to a more "classical" variant - vertical mast and rotating struts. Everything could be done from aluminium, no expensive carbon fibre is needed.
     
  6. bruceb
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    bruceb Senior Member

    Power

    Scott, to move 1000lbs, you need some power in your rig, and a stayed mast will be lighter for the amount of sail area I would think you need. Also, you can use an inexpensive spar, carbon is not required. A fractional sloop rig gives you a lot of possible sail combinations and should be quite easy to handle with furling jibs and a battened main. Full batten square top mains are nice as they still retain their shape even when well reefed.
    B
     
  7. scotdomergue
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    scotdomergue Scot

    Hello all. Thanks for all the ideas. I will look at them closer soon and respond. My internet systems didn't alert me to several messages, so I'm behind.

    I've been very busy getting the boat design (not rig) to a point where I can order materials, also a lot of communicating with potential crew for the race.

    I will probably stay with the cat-ketch rig using carbon windsurfer masts - which are very light weight and inexpensive (for used ones), and can be strengthened and stiffened by inserting parts of other windsurfer masts inside. This idea came from an Australian land yacht forum someone on another forum pointed me to.

    More later.
    Scot
     
  8. gonzo
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    gonzo Senior Member

    If you are racing, the rig needs to be powerful. Windsurfer masts are really bendy and designed to have a person hanging from the wishbone. There is a huge amount of research gone into rig design, so it doesn't make sense to hodge podge something together if you intend to be competitive. Look at multihull rigs for comparison. The righting moment is relatively large, so the rig can be stiff. For example, a Hobie 18 has a 28 foot mast and 240 sq.ft of sail.
     
  9. CT249
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    CT249 Senior Member

    That's effectively Francis Herreshoff's idea from many decades ago with a different way of swivelling, isn't it? The same idea was a massive failure in the LACC some years ago.

    It seems from the other thread that you are hoping to incline the rig like a windsurfer, however windsurfers try to keep their rig as upright as possible, generally, as an upright rig is more efficient. Also, of course, a rig that is heeled to windward is a disaster in very light winds.

    Frank Bethwaite tried ideas like these for years and then realised how much more effective the classic sloop rig is in the real world of normal sailing.
     
  10. CT249
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    CT249 Senior Member

    We windsurfers notice an enormous difference in the way a rig works when we go from a 12'6" 21kg Original Windsurfer to a 16kg 12'9" Raceboard, to a modern 6kg 7' slalom board. You need a different rig to get the best out of each of these types of board despite the fact that they vary in length and weight by only small amounts (when you take into account sailor weight).

    The standard modern windsurfer rig is extremely low drag but has low lift. It doesn't push a 21kg Original Windsurfer as well as an '80s style soft sail, so it is highly unlikely to push 1000kg of tri. The typical modern windsurfer rig is designed to push a very light board around on a reach in about 12-15 knots of wind and more, not to push a heavy tri around a course. To expect a board-style rig to work on a heavy tri is a bit like saying that because a racing cyclist can ride a 6.8kg bike on the flat at 60kmh in a sprint, you should be able to use bicycle gears to propel a 1000kg car up a hill at a decent speed.

    As gonzo pointed out, multi rigs are at the other extreme of stiffness. Our old Formula 16 had a wing mast so wide that it had higher mainsheet loads that the Tornado, which was 4' longer and much heavier. The small tris I've sailed (Tri Fli, Outrigger, Bethwaite HSP, Supernova) had quite flexy rigs but all of them are pretty light.
     
  11. Nick_Sinev
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    Nick_Sinev Junior Member

    Thanks for info about Francis Herreshoff and Frank Bethwaite!
    It's really interesting for me!
    Right now I'm trying to "google" their variants of riggging.
    If you have some links or more information on this item, could you provide me with this info?

    Some lifting force could be an advantage (for some vessels).

    Yes, you are absolutely correct. A standard sail in this scheme wouldn't work in case of a slow wind.
    When I draw the sketch I was thinking on a semi-rigid wingsail with a symmetrical profile.
     
  12. Claus Riepe
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    Claus Riepe Junior Member

    IMHO the use of freestanding carbon windsurfer masts would be perfectly possible. They are not necessarily "awfully bendy". You can get them in various dimensions and stiffness grades ("IMCS" indicates the stiffness, the higher the stiffer). Though I admit the very long and very stiff ones can be quite expensive. I know a few sucessful homebuilts and production boats using windsurfer masts for masts, topmasts and booms.
    One caution: If you step a mast into a deck quiver or socket, do reinforce the mast internally with an inserted hardwood piece in the area of the mouth of the socket.
     
  13. Richard Woods
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    Richard Woods Woods Designs

    The Finn dinghy has about 10sqm sail. So smaller, but close to what you are proposing. So it might make sense to use a Finn mast as a basis for your design, not a windsurfer mast

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  14. FAST FRED
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    FAST FRED Senior Member

    It is true some rigs are more efficient than others at some point of sail.

    BUT since you are not rating bound and can have as much sail as the boat needs efficiency takes on a different meaning.

    Which is the best to windward that you can handle with the most ease?

    I would look for a sloop rig I could purchase used .

    Free standing adds lots of complexity to the method of installing it and carrying the loads to the vessel.

    A few stays will lower the cost by 1/2 or more and make a safer installation.

    With a try , the wide staying base makes the wire loads very small.
     

  15. CT249
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    CT249 Senior Member

    A pic of Wingmill can be seen in

    http://cfd.mace.manchester.ac.uk/twiki/pub/CfdTm/ResPub261/thesis.pdf

    This source says that Wingmill appeared to be fast, but I seem to recall that those who saw her sail (in the brief time before she fell apart) thought that she was not consistently fast.

    The sketch showing a similar design by Francis Herreshoff is in his book "Common Sense of Yacht Design", if I recall correctly.

    Frank Bethwaite's experiments with rigs are covered in his "High Performance Sailing" book. Many of the experiments were in front of my old house and we used to see how inconsistent the deltas, kites etc were in performance. Frank returned to the conventional sloop for his HSP tri as a result of these many experiments.

    Yes, lifting force can be an advantage, but its advantages have often been overstated in the past. Back in the 1980s when windsurfers were starting to go really fast, I went to the Weymouth Speed Week. The beach appeared to be full of bearded men with fragile, complex and slow inclined-rig multis, all of them convinced that rig inclination was the key to speed. The week before I had been racing at a development-class windsurfer world championships where many people were working hard to ensure that their rigs DIDN'T incline. Modern boards are sailed with dramatically less rig inclination than the early Windsurfers, which used inclination to control weather helm rather than to go fast. I got the feeling that many of the fans of the inclined rig hadn't bothered to try to learn from those who used inclined rigs to go fast -the windsurfers.

    Obviously Sailrocket showed how well an inclined rig can work, but she's a very different style of beast.

    I've got three wing masts and a bunch of other leading-edge fairings, but IMHO the advantages of them are often over-rated.

    Cheers
     
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