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Single mast vs. multiple masts

Discussion in 'Yacht Designers Discussion' started by Chapstick, Jun 23, 2013.

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  1. Chapstick

    Chapstick Member

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    Sorry if this is an ignorant question, but I'm just curious: how is the decision for a design made between single and multiple masts?

    I suppose you can't fit multiple masts on a small boat anyway, but what about larger ones? Why are multiple mast designs so rare?

    Is it aesthetics? Are they just considered ugly?
    Is it complexity? Is a single mast easier to sail, especially with fewer crew?
    Is a single mast lighter for the same area of sail?

    I imagine for the same area of sail it'd be easier to keep stresses down for multiple shorter masts than for a huge single mast, so there must be some reason for the popularity of single masts....
  2. Ward

    Ward Senior Member

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    It depends on a huge number of factors: what the owner wants; what the boat is for (racing, cruising, where, how much...); how big is the boat; how many crew; what can the owner afford...

    There are a few generalizations:
    • a single mast is simpler - less rigging - which makes it more straightforward to design, build, and optimize.
    • but multiple masts can break a given sail area into more easily managed pieces...
    • single masts would seem to be faster... It hasn't always been the case, but I think that there are no current high-end racers with multiple masts.
  3. NYCAP123

    NYCAP123 Senior Member

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    A mast can only carry so much sail area before reaching the breaking point. More weight to be pushed, the more sail area needed. In the days of clipper ships and square rigs those ships and cargo were very heavy and needed a maximum sail area. Today's boats are more sleek (less water resistance) and don't carry cargo (less weight). Also modern technology has allowed taller, thinner masts to carry more sail area, and modern sails can be made larger and lighter without tearing.
    The minimum number of sails also allows them to collect more wind. Often square rigs and multi-mast can reduce the amount of wind that makes it to the further downwind sails. You'll often see a maneuver in sail racing where a boat will try to get downwind of their competition to take the wind out of their sails. Same principle.
  4. Chapstick

    Chapstick Member

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    Thanks for the info guys.

    So basically as I now understand it a single mast is simpler, and adding a second sail downwind will be less efficient than increasing the size of a single sail...
  5. NYCAP123

    NYCAP123 Senior Member

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    Yes, but additional masts could be needed if the sail area of a single mast couldn't gather enough wind to propel the vessel. Look up the vessel Zeus
    who now is (I believe) mastless for whatever reason down in Palm Beach. At the time she was built she was the largest single mast vessel (or had the largest mast). I believe it was about 150'. Then look up Maltese Falcon which needs multiple masts.
    Now this is just basics. In reality things are far more complex these days with computerized sail handling, lighter and stronger fabrics, turbine masts. Then you have things like Cat rigs, Ketches and Yawls which deal with different sail cuts and mast placement. It's quite a science. Personally I'm always amazed and in awe when I see the square riggers and think if what must have been involved in the calculations involved between the acres of sales and miles of lines in the days before calculators and computers. To think of some guy sitting with a pencil and a piece of paper figuring it all out is just mind blowing.
    I'm not much of a sailor, and don't think much of the Sunday sailors who stop their education once they hear "sailboats have right of way", but I have ultimate respect for the guys who design and run the big boats. Seems that the word genius is completely inadequate.
  6. Old Phart

    Old Phart Senior Member

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    Hidden in plain sight, 1889 Nat Hereshoff Cat Yawl Coquina.

    herreshoff coquina - Google Search
  7. Ward

    Ward Senior Member

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    Well... The best configuration for upwind vs. downwind is not that clear-cut. Again, the latest, highest-tech racers are all sloops, but for a cruiser that aims to avoid too much upwind slogging, ketches can make sense. See, e.g. Dashew's Beowolf...

    Since you're posting on a site geared towards big boats, keep in mind that size is a big factor: as the size of a sail goes up, the loads on sheets and fittings also go up. I think Mirabella V still holds the record for tallest sloop rig, and I recall reading something about the captain being leery of really pushing her in a blow because of the huge loads involved.
  8. Chasm

    Chasm Senior Member

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    Also Dashew's various cruisers were geared to two person operation. Which in an emergency means single handed.
    The larger the sail, the larger the forces - and the room for error shrinks further and further.

    Beyond aesthetics there are also such mundane considerations like bridge clearances.
  9. Fishtigua

    Fishtigua Senior Member

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    To give you an idea of the size of Mirabella's rig next to Falcon's.

    Attached Files:

  10. nilo

    nilo Senior Member

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    more advantages of ketch rigs

    1- a ketch rig is more stable because you have two points (each mast) that acts on the hull; thus keeping the hull more stable
    2- at anchor you can have the mizzen sail up and this will keep the boat heading towards the wind, not swinging and thus there will be less loads on the anchor and this will also push the boat somewhat forward also keeping the loads on the anchor low.
  11. Ward

    Ward Senior Member

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    I was curious, so I looked it up:

    Mirabella V:
    Length 75.2 m (247 ft)
    Mast height 88.5 m (290 ft)
    Displacement 740 tonnes
    Sail Area 2385 m² (25,675 sq ft) (main+working jib)

    Maltese Falcon:
    Length 88m / 289ft
    Mast height 58.2m / 191ft
    Displacement 1,240 t
    Sail Area 2,400 m² / 25,791 ft²

    So even though Mirabella V is shorter, her air draft is more than 50% greater than Maltese Falcon's.

    And, as pointed out in the following post, there are other factors, so I edited in sail area and displacement... The comparisons are interesting, and you can see some of the tradeoffs, but not enough to generalize into any rules or guidelines, they're two very different yachts.
    Last edited: Jun 24, 2013
  12. NYCAP123

    NYCAP123 Senior Member

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    Check what they're pushing also: 740 tons vs 1240 tons.
    Lots of calculations involved.
  13. brian eiland

    brian eiland Senior Member

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  14. brian eiland

    brian eiland Senior Member

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    Ketch Rigs

    I've long been a proponent for ketch rigs. If you were to google my name along with the word 'ketch' you would likely find many discussions on the subject,...including some references to my 'single-masted ketch' ;)
  15. Chapstick

    Chapstick Member

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    Which is the heavier sailing "system"? i.e. comparing only the masts, rigging, sails and other directly associated masses, which would be heavier: Maltese Falcon's multiple masts, or Mirabella's single mast?
  16. Ward

    Ward Senior Member

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    I would guess Maltese Falcon's total rig weight is higher, but not by a huge amount. Why?
  17. Chapstick

    Chapstick Member

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    Thirst for knowledge I suppose...I like to sponge up information, and there are plenty of brains to pick here.

    They have about the same area of sail, and NYCAP mentioned the difference in displacement, so I wondered how much was due to the way they're rigged.
  18. NYCAP123

    NYCAP123 Senior Member

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    Sorry but I could only give a wild and useless guess. However, since both vessels have taken full advantage of technology aiming for lighter, stronger and more efficient I'd imagine that whatever weight difference there is in this would one smaller piece of the equation.
  19. Pascal

    Pascal Senior Member

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    Boats are nothing more than a collection of compromises.... There is no magic formula, perfect boat or configuration and that applies to rigs. Yes, a ketch or yawl has advantages but so does a sloop rig. This is particularly true on smaller boats (under 50') where the mast will end up near the cockpit with extra stays, lines, etc...

    And of course, personal preferences is important as well as how you use the boat. Sometimes sacrificing a little bit of performance for comfort or ease of handling is worth it.
  20. 84far

    84far Senior Member

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    The layout for a Ketch will push things forward (cabin and anything down below). Plus you have extra stays to deal with, not ideal when the winds are high... more things to trip over. I can also see the vessel costing more to build as well... getting the CLR, CE, displacement etc, to flow is a mission! Cheers

    Far