What's wrong with Lug Rigs?

Discussion in 'Sailboats' started by bergwerk, Aug 7, 2016.

  1. CT249
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    CT249 Senior Member

    The modern theory we are getting from people like Mikko Brummer here tells us that the mast doesn't disturb the suction flow. If I may quote Mikko;

    "We have found through computer analysis that the mast is actually the most efficient part of the sail area. It can provide up to 10% of the sailboat drive (a Finn-dinghy with a rotating mast). For a sloop rig with main & jib the percentage is more like 2,5-5% of the total drive, with an area which is less than 3% of the total sail area (in case of the Star shown here). Per sqare meter the mast is far more efficient than the mainsail behind it, when it comes to driving the boat forward."

    As Mikko also put it in the link below, the mast is not just a drag producing device but something that can contribute power to the sails.

    http://cdn2.hubspot.net/hub/209338/news/Ad_aerodynamics/index.htm?t=1428319882242

    None of means that the lug isn't a great rig for its use. One of my daydream boats is a Michael Storer Beth lug canoe, although since I have another wooden sailing canoe sitting in the roof of the garage I can't find an excuse to get a Beth. But unless all the great racing sailors, designers and sailmakers are wrong, the lug can't be better aerodynamically, especially when issues like draft control via mast bend are considered.
     
  2. LP
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    LP Flying Boatman

    One aspect of the cost equation that hasn't been mentioned yet is the expense of the rig required to support a given sail plan.

    The free standing lug rig mast (wooden most likely) I believe will be comparably cheaper than the tall skinny mast (aluminum) and its associated hardware or a freestanding wing mast(carbon?).
     
  3. TeddyDiver
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    TeddyDiver Gollywobbler

    To be honest that's an utter BS if we talk about conventional masts. It may look like lift on the computer screen but that's out of context looking the just the pressure lines beside the mast but ignoring the separation behind the mast. If it were true why use sails at all just a bigger mast untill we have something resembling rotary cylinder, they produce real lift but with a cost of excess drag..

    BR Teddy
     
  4. bergwerk
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    bergwerk Junior Member

    Very interesting and thanks for the link, good reading.

    The Chris White Mastfoil rig had me convinced long ago of the power of the mast.

    http://www.chriswhitedesigns.com/atlantic_cats/mastfoil/
     
  5. sharpii2
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    sharpii2 Senior Member

    With a Balanced Lug, the Boom and Yard can be the bendy spars, so the sail's draft can be controlled that way.

    As for this computer study of the mast contributing to drive, is this mainly for upwind sailing?

    It would seem to me that, unless you have a somewhat more expensive pivoting mast, an airfoil shaped mast is going to be real good for upwind sailing but pretty sucky for cross wind sailing, as the wider profile of the airfoil section will be in front of the leeward side of the sail, where most of the lift is created.

    A more traditional BR had a round mast section, with the sail hooped or laced to the mast. This way, the mast section was mostly to the weather of the sail cloth, which is where I think one would want it to be.

    Once fore stays, spreaders, and lower shrouds come into the equation, the hoops and/or lacing have to go, with a sail track taking their place. Once this happens, the sail cloth could no longer move to the lee of the mast section. I have often thought of the idea of having a round section mast for a 3/4 sloop, with sail lacing up to the shrouds, and a luff spar, from there to the top of the sail.

    Add to that, the fact that racing seems to have become more and more an exclusively upwind/downwind affair, sacrificing crosswind performance (for the main only) for better upwind performance may well be worth it.

    As an interesting side note, Phil Bolger once claimed that Cat boats were only allowed spinnakers, in certain racing rules, if the length of the spinnaker pole and the height of the mast above it were counted as fore triangle area, for sail area measurement purposes. This way, sloops were effectively allowed t o have spinnakers as uncounted SA, while Cat boats weren't. If this is true, this certainly was the voter ID law of sailing.

    One can only imagine what would have happened in rig development if all the SA was counted, including that of the spinnaker. Would we be seeing a lot of gaff rigged Cat boats today, instead of the pervasive BR sloops?
     
  6. gggGuest
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    gggGuest ...

    To be honest that's simply rubbishing something you clearly don't understand.
    Its all to do with the interaction of mast and sail. Its explained in the referenced web pages.

    There have been so many rating rules, some of them very imperfect, that it would be foolish to categorically say that never happened, especially back in the early days of such things back in the mid 19thC, but to the best of my knowledge that hasn't been the case in any of the mainstream rules in the last 100 years. It seems possible there was a rule where they assumed jibs and spinnakers were never flown together (as was often the case in the days of spinnaker poles limited to J measurement) and the spinnaker was limited to the foretriangle size, which would have meant, say, a sloop would have 100sqft main and 50 sqft foretriangle for 150 sqft main and jib uphill and 150 sqft main and spinnaker downhill, and a cat boat with no spinnaker would have 150 sqft main up and down, so 50 sqft spinnaker would have meant 150sqft up and 200 sqft down and thus some sort of taxation appropriate. But I'm guessing.


    There are a number of classes where you can have any rig you like and there's just a total sail area limitation. The Bembridge Redwing is one such, in which one of the more radical rigs tried was an autogyro. But the typical rig now is a *very* high aspect ratio bermudan sloop. All such classes I can think of have either the sloop rig or a single una mainsail, with the arguable exception of the modern C Class Catamaran which could be said to have a una rig upwind and a sloop rig downwind!
    Square foot for square foot spinnakers aren't a very efficient use of sail area, but they are by far the easiest way of chucking up a bunch of extra rag for downhill and dropping it completely uphill.
     
  7. CT249
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    CT249 Senior Member

    It was mentioned earlier. No one has yet presented any evidence that lugs are cheaper when comparing like to like.

    There are expensive lug rigs with stay adjusters, die-form stays (if I recall correctly), custom-made chainplates, hand-made leather chafe protectors, custom-made engraved collars and spars that (if made in Holland) come from a special climate control-factory. They can't be cheap compared to the simple hole in the deck and agricultural-pipe mast you can have with a bermudan rig.

    [​IMG]

    The stainless steel lower mast base, adjustable mast track, carbon roller-bearing Harken fittings and high-tech lines at the base of the same mast wouldn't be cheap either.

    [​IMG]

    Sure you can build a cheaper lug, but you can build a cheaper bermudan than most people do, too. The stay adjusters alone on that boat (and on the standard Italian production Int 12) cost almost as much as a complete bermudan spar on the most popular 12' dinghy here.

    Going from history and the popular classes, there seems to be no strong indication that lugs are more likely to be freestanding rigs or cheaper rigs than bermudan rigs, all things being equal as much as we can judge. Back in the 1800s, the bermudan rig was thought to be the cheap and simple option and the lugs were used on fancy racing machines owned by the wealthy. The lug is still a great rig, no one's saying that anything is wrong with them. Sadly, though, there are lug rig fans who spend time casting aspersions on the bermudan.

    I've seen some lug fans criticise the bermudan rig because they supposedly need an expensive gooseneck, for example. But a bermudan rig can have a "gooseneck" that is just a piece of line, or a simple jaw like those used on a gaff, a plastic rowlock (like a Topper), a piece of bent scrap alloy and three bolts (as with old Moths), or even no gooseneck at all on an Olympic boat!

    [​IMG]
     
  8. CT249
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    CT249 Senior Member

    No, we wouldn't. Because in many classes all area IS counted, and in other classes no area is counted. And yet not a single one of these classes uses gaff rigs.

    So much of the blame that is put on rating rules is complete and utter BS. Not only is it often factually inaccurate, because the claimed rule often doesn't exist (and we've even had experienced designers from BDF publish such claims in magazine articles) but they almost always rests on the belief that the writer's own type of boat or location is the centre of the sailing universe. If Bolger's claim about catboats was correct, for example, then it appeared that he assumed that the US was the only place worth thinking about - because US rating rules didn't restrict design on London's Thames, Sydney Harbour, Auckland or Liverpool. No such rule applied in those areas - and in all those areas cat rigs were in the minority.

    Sorry to sound so cranky about this - I just can't work out why sailors like Bolger and so many others spend so much time blaming other people for things like the fact that most people prefer a certain rig or type, while arrogantly ignoring the huge parts of the world that don't fit their theories. Almost all of these claims that can be examined are rubbish. Don't we learn a lot more by looking for the truth and working out what it is about popular rigs that makes them popular, instead of making up fairy tales about unfair rules?
     
  9. gggGuest
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    gggGuest ...

    That depends on whether we would rather accept an unwelcome truth, or cling to any myth that supports our preconceptions... The latter is demonstrably a very human thing to do... I know I've been guilty of it from time to time.
     
  10. TeddyDiver
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    TeddyDiver Gollywobbler

    Don't know this particular case by Bolger but generally I believe most such claims are just taken out of context and started to have life of their own..

    What comes to the theory of the benefits of mast lift, it's just unproven theory untill real world windtunnel tests are done.

    BR Teddy
     
  11. gggGuest
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    gggGuest ...

    Bit of a struggle to claim that the tools used for all sorts of other aerodynamic work are unproven theory.

    But the main reason I find Mikko's work so compelling is that for 30 years or more sophisticated mast sections, wing masts, rotating masts and the like have utterly failed to show on the water the performance benefits that the more simplistic aero theory we had in the 70s claimed they should have. Now this new more sophisticated analysis is providing theory that provides an explanation for what we'd already observed in real life.
     
  12. CT249
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    CT249 Senior Member

    As gggGuest notes, these tools are used for other work. Secondly, at least one oft-quoted study (Marchaj's) was not at all "real life" because it was done with a grossly over-sized mast section that you would never see in the real world - 15% of foot length of something like that.

    To again repeat gggGuest, the issue is that the real world has shown that theoretically efficient masts don't achieve what is claimed for them on the water. If there was just one or two attempts they could be written off or put down to the problems of using full size boats for experiments. However, when the attempts started around 1931 and have been regularly repeated in something like a score or more of different classes, it's apparent that the wind tunnel tests were wrong and not the hundreds of real-life full-size tests.

    To quote aerodynamics expert Arvel Gentry "Wind tunnel tests can often be just as misleading as tank tests" and "The results of the studies described in this paper seem to indicate that the mast is not quite the villain that it was
    previously thought to be. Although it does cause separated flow to exist over a portion of the mainsail, its position as the leading edge of the mainsail airfoil also causes a part of the surface of the mast to contribute a
    significant amount of forward thrust."

    And finally, as noted, the idea that lugs are faster than bermudan requires some mass madness or wilful blindness to have overcome all the designers in all the development classes around the time that lugs faded away. It is hard to see why that is more likely than some wind tunnel tests being wrong.

    Dinghy designer Mike Storer has done lug rigs, and sailmaker Todd Bradshaw makes more lug sails than any other type. Both are interesting sources for information on the rig. Neither says they are as fast as a bermudan. They obviously had significant advantages in some ways in the 1870s when people like Burgoyne and Hope adopted them, but advances in materials have turned the situation around.
     
  13. TeddyDiver
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    TeddyDiver Gollywobbler

    Square top main is more efficient than conventional bermudan main is something we can agree? If we have (theorically speaking) square top and lug identical in shape and material both properly trimmed then the only difference is the mast. Then it boils down is the drag of the mast standing separately of the sail more or less than the lost lift of the sail behind the mast. Being different phenomens there's certainly not one absolute thruth for all circumstances.
    A computer program, thou giving quite accurate predictions in some pretermined scenarios can give wrong answers in others. If they cannot be verified in reality it's just air..
    Wind tunnel and tank test results are precise, how we interprete and scale them may be inaccurate IMO

    BR Teddy
     
  14. bergwerk
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    bergwerk Junior Member

    +1 Excellent point Teddy.

    Another issue that I've raised but gotten no answer to is the cost of the entire BR -including the headsail- compared to the LR. If we want to ignore it then we should sail the LR against the BR under main alone.
     

  15. upchurchmr
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    upchurchmr Senior Member

    I've never seen a lug with the same aspect ratio as a square top bermudan.
    I'm pretty sure that makes a difference
    And having the yard up at the top of the bermudan would have an effect on heeling and motion in waves - a bad effect.
     
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