What kind of boat can sail closest to the wind?

Discussion in 'Sailboats' started by laukejas, Aug 29, 2016.

  1. rob denney
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    rob denney Senior Member

    Sure was, and by an irish boat a century earlier, although it is not known how well, or if, it went directly into the wind. Bates' boat was my inspiration to put a 9.4m/32' dia 3 bladed windmill on my 9m/30' Iroquois cat 30 years ago.

    Designed turbine rpm was 180 in 20 knots of breeze, when it should have done 13 knots directly into the wind. We were never brave enough to go more than 110 rpm, at which it managed 6 knots directly into 20 knots of breeze, which was way faster than the boats vmg under sail.

    It was no slouch reaching and running, either. In theory, with the water prop disengaged, it would have "sailed" (autogyro'ed) as well or better than it did under it's sail rig, but the fear of the forces overcoming the controls meant we never tried it.

    Interestingly, an autogyro rig was tried on a Redwing (od hull, any rig) in the 20's by the very clever and adventurous Lord Brabazon. It was apparently pretty quick, but at one stage they lost control and it hit some moored boats, and was banned. The blades (painted canvas over steel shafts) from this boat were in a house in Cowes when i was building mine.
     

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  2. gggGuest
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    gggGuest ...

    It won't though. The high aspect ratio board will be lower drag at every speed providing its operating within its limits. What a low aspect ratio brings to the party is a lower tendency to stall and more tolerance of being pushed past the limits. This can be helpful of course. Most river sailors know the feeling of squeezing the boat round the bend, foil half stalled out, drag horrendous, speed diminishing rapidly, but just make it past the corner and it will be fine...
     
  3. DennisRB
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    DennisRB Senior Member

    There you have it. Wind turbine powered boats sail directly to windward.

    Wing sail boats like the latest AC boats can sail at very narrow angles and fast speed (compared to other boats) but as mentioned they can sail at faster VMG and much faster boat speed at a larger angle.

    I think you are looking for boat with excellent VMG and excellent pointing. Most racing multihulls can do both. A fast multi can point higher and sail faster than a fast mono. Its just that thier VMG is faster again if they back away.
     
  4. Stumble
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    Stumble Senior Member

    Whenever talking about pointing it is critical to make sure everyone is talking about TWA or AWA. My A-Cat for instance sails at about 20 degrees AWA but given the speeds this can work out to around 45 degrees TWA. Slow down by a lot and 20 degrees AWA stays the same, but I can probably squeeze to 30 degrees TWA. It's just god awful slow (4kn vs 12kn). But short of a wing sail the A-Class has one of the most refined rigs there is.

    You would ever see anyone sailing the boat at super tight TWA unless you just barely miss calling the line, and sometimes the speed loss is worth it to not have to tack two more times.
     
  5. DennisRB
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    DennisRB Senior Member

    Yeah I agree totally. It was kind of my point. I think the OP was interested in what sort of boats do well in both. I think most people go off the AWA. I often hear tales of disgruntled racing mono sailors who have been smoked by a racing multi upwind. They think its some sort of benefit their boat has when they proclaim at least they were pointing higher. Well since they are going slower, they can point higher. It does not mean the multi still would not have overtaken them anyway if they chose to slow down and point to the same TWA as the mono. The multi sailor was just sailing as fast as they could for VMG and it so happens it was at a broader TWA than the mono. The monos benefit was actually an illusion based on its slower speed.
     
  6. Petros
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    Petros Senior Member

    to make it clear, any lifting surface (sail, fin keel, wing, rudder, etc) that is high aspect ratio will have lower drag for the same amount of lift (better L/D), but will stall at an earlier angle of attack, and will also be much more sensitive to a sudden stall. A low aspect ratio surface will have more drag for the same amount of lift (lower L/D), but will not be stall sensitive, can swing through a larger angle of attack before stall, and on really low aspect ratio they do not stall at all, but kind of "mush" gently.

    so to point high, low drag is important, so you need high aspect ratio sails and fin keel, but it will be more sensitive to stalling out (suddenly you will be dropping off your point without warning when close to your limit). This is why high aspect ratio surfaces are not good for rudders, or low time skippers or crew.
     
  7. The Q
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    The Q Senior Member

    For more conventionally rigged boats I would look at those used on rivers, For instance the 3 Rivers Rivers Race allows boats up to 40Ft LOA, which have to sail up the river Ant to the turning point in front of Ludham bridge at some points the river is about 40ft in width!!!

    Here's a link to some Photos taken from the bridge / Bank at the turning point which is a bit wider.

    https://www.flickr.com/photos/rssupport/albums/72157668929912141

    and a link to the same mans photos around the Norfolk broads

    https://www.flickr.com/photos/rssupport/albums/with/72157668929912141


    and a broads cruiser going up the river Thurne, think about the tacking when the wind is head on.!!!

    http://s0.geograph.org.uk/geophotos/04/61/68/4616899_a0f2cff6.jpg


    quote"It won't though. The high aspect ratio board will be lower drag at every speed providing its operating within its limits. What a low aspect ratio brings to the party is a lower tendency to stall and more tolerance of being pushed past the limits. This can be helpful of course. Most river sailors know the feeling of squeezing the boat round the bend, foil half stalled out, drag horrendous, speed diminishing rapidly, but just make it past the corner and it will be fine..."quote

    Oh ggggGuest, do I know that one....
    (and pray you don't hit bottom or catch a tree at the same time)
     
  8. CT249
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    CT249 Senior Member

    Hmmmm.....while the multi may well have overtaken the mono if the multi slowed to the same VMG, in my experience many monos will, in the end, be able to sail higher than a multi. The larger area of the foils, compared to the aero drag, gives the mono the ability to pinch to a higher angle.

    Although I haven't checked directly, I reckon the International Canoe and Tasar, for example, would be able to sail higher than a Taipan 4.9 or Hobie Miracle 20. Of course, the VMG can't be compared, but that wasn't the question.

    As someone who sails boards, monos and multis I never hear of many disgruntled mono sailors making excuses. Most just don't care if they get passed by multis, just as multi sailors don't really care if they are passed by foiling Moths, and foiler Moth sailors don't really care if they are passed by foiling kites.
     
  9. Skyak
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    Skyak Senior Member

    Angle upwind is kind of useless compared to VMG. The caveat is that you need to take tacking speed into account. AC33 put this on display -the wing sail trimaran was a little faster upwind, but it absolutely crushed the catamaran in every tack because it could pivot on the main hull with lots of rocker.

    As others have pointed out, speed upwind takes directly from apparent wind angle. For very fast boats like the current generation AC there is no downwind. These boats have the highest VMG acheived -and the key is LOW DRAG.

    Upwind speed of all sailboats is limited by drag. The example of the iceboat also shows how important drag is. Iceboats with big sloop rigs are pathetic compared to tall thin wingsails. With no water drag the wing reaches its potential.

    So how do you get to low drag?

    Hull -minimal wetted surface -preferably none like a foiler. Minimal displacement creating waves, longer smoother hull between entry and exit to get the longest wavelength and highest speed before wave drag shoots up. And once you have this long optimal hull, be sure it is going straight through the water. Leeway is best resisted by foils, not hulls.

    The last important point about hulls is that wave drag from your hull will most likely be the speed limiter of your boat upwind. This is important because it influences the shape of your lee board and rudder by defining their operating speed.

    Foils

    In the water I think your foils are pretty good. Higher aspect ratio, smaller area foils are higher performance upwind, but for the operating speed of your boat stall would be a problem. Which leaves the big factor -sails. After wave drag on the hull, drag on your sail rig is second highest. The lowest drag sail would be high aspect, tall, flat, and have an elliptical loading over it's span. What this means is that if you could see the air forces summed up vertically on your rig the curve they create would look like a circle viewed at an angle. The smooth increase in force from zero at the free ends to the peak toward the middle looses the smallest amount of power to creating vortexes. The lug sail you have is far from this ideal. It is low aspect, oddly shaped (relative to ellipse) and it is difficult to control twist and camber. The big plus is that it hangs the largest sail area in the wind with the lowest righting moment. In low wind conditions you have the advantage.
     
  10. Petros
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    Petros Senior Member

    the answer is a power boat. it will sail closest to the wind in all conditions.
     
  11. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Lol! As a power boat owner I'm following thread with interest .

    Einstein said ' If you can't explain it to a six year old child, you probably don't understand it very well yourself.'

    Me, I'm the six year old!
     
  12. gggGuest
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    gggGuest ...

    Cue for a "lost man in balloon" joke...
     
  13. Stumble
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    Stumble Senior Member

    A multihull should be able to out point any similarly placed monohull. If for no other reason than the L/b of the multihull will result in less drag than a monohull can achieve. Comparing an IC to a Hobie anything is really just silly, but compare the same IC to an A-Cat and the A-Cat will out point it.

    Though in race mode the A-Cat may choose to sail lower and faster, if you put both of them in pure point mode the cat will be higher and faster.
     
  14. gggGuest
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    gggGuest ...

    Got to love it when people are so dogmatic about what they cannot possibly know for sure.

    Canoe rig will be at least as sophisticated as the A Cat.
    Most Canoes have a lower drag rudder configuration with the blade end plated by the hull.
    Once you get into the really high and slow regime the Canoe has much lower displacement and a good bit less wetted area, which most certainly has the potential to outweigh the l/b ratio of the Catamaran, which is about wave drag and comes into play at higher speeds.
    The Canoe has rather lower aerodynamic drag, and as CT noted, probably larger foils in proportion than the A, which relies, quite correctly, on its speed to make up for small foil area.

    *I'm* not going to try and predict the result. Of all the people I know though, CT is one of the best placed to make the comparison, as he owns both high performance catamarans and monohulls. Its also an utterly utterly pointless comparison because its not a regime either is designed for. Naturally a good A is faster upwind in normal racing conditions than a good IC, but that's not relevant to this. Indeed *if* the Canoe should be better at a pointless pointing match, it could be argued that the most likely reason would be that the A has been optimised so much for sailing at a higher speed through the water just because sailed properly it will be sailing at a higher speed.

    There's this peculiar chip on the shoulder/inferiority complex from a section of the multihull community. Like CT says, I never heard of a disgruntled monohull sailor making excuses. The laws of physics say a catamaran should be faster when both are sailed for best vmg, and like the man said, "Captain, I cannae change the laws of physics".

    Tell you one thing though, if I were on the rivers that "the Q" describes, which I know reasonably well, and is one of the few situations where pure pointing can pay, I'd get up the Ant a great deal more easily in an IC than an A class, and get up it more easily again in something quite different to either - possibly a Thames Rater or a Norfolk Punt.
     

  15. rcnesneg
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    rcnesneg Senior Member

    Etchells can point really well. Same with a lot of the older boats with deep keels and tall rigs and notable overhangs. The overhangs don't help by themselves but those tend to be the kind of boats that point slow and high.

    Catamaran experience:
    I sail quite often on a Hobie Fox (Formula 20 Catamaran, a lot like an F-18 but bigger).
    It will point up to 20 degrees with the jib furled up in flat water with both boards all the way down. Granted, I'm only doing 2-3 mph in 10 mph of wind, and if I roll out the jib and fall off to 50 degrees I'm doing 9-10 mph, but it will point that high at the expense of speed. It's especially useful when getting out of a really tight marina with a long channel less than 40 feet wide. It's fun to take someone new on it and pinch like that and see their reaction when they realize we are going extremely high. It feels like you are going straight upwind, and you really have to be on the steering to handle the shifts. It also helps to have the weight forward and keep the transoms out.
     
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