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Old 29-06-2008, 11:05   #151
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Hi Eleven. Good comments. I think there's room for more performance gains with end plate effect on the main and jib. I have noticed considerably higher wind velocity in the slot on a boat with a real deck-sweeper genoa, and can imagine some enhancement from a boom that is very wide, serving the same purpose. What I don't see is how much spanwise flow there is on a triangular sail with the pointy top in faster wind (further from the surface drag of the water). I would think that tell-tales in the middle of the sail would show this. Has anyone tried this?
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Old 29-06-2008, 11:35   #152
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Hi BigCat! Bernouli is hard at work on both Junk Rigs and assymetrical airfoils flying upside down. Inverted, a conventional wing is able to fly, but at a much higher angle of attack than right side up. Bernouli isn't completely happy with the situation, and complains with a whole bunch more induced drag, which requires a lot more power from engines that are designed to run tight side up (the oil sump is empty when the engine is upside down) so inverted flight is in most cases a no-no. But there are fixes for all these little problems, hence airobatic and flight demonstration aircraft.

What a lot of people missed about Junk rigs is that Bernouli speaks Chinese too. Those old sails were NOT flat boards. They curved in the wind because they were anchored towards the front and the control lines were tied to the aft ends of the battens. However, those more recent Chinese sail designers didn't speak Bernouli, and they had different reasons why tapered battens worked better! Just as airshow crowds were baffled by inverted flight, Junk sailors were amazed that junk sails worked when the mast was on the wrong side of the sail, giving it a funny "S" shape. The truth is, a little Bernouli goes a long way!
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Old 29-06-2008, 12:38   #153
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Reply to Eleven

"The transition from the back of the mast or the rigid front section of a wing mast onto the flexible sail must be smooth on the backside (upper of a wing). Neither wing edged sails or masts do much to help this. Lumps on the pressure side (underwing) just add a bit of drag and don't damage lift too much."

I agree that there has to be a smooth transition from the side of the mast to the sail. I am not sure why you think this is impossible, or even difficult. People use pivoting foil masts (wingmasts,) and report good results all the time-many people have remarked on how well wing masts work, and how surprised they are at the power they get from them. Many very fast boats have used some version of a wingsail. There are many links to accounts of such boats at the bottom of my website.

I agree that the lee side is where the work is done-and that this is where laminar flow is important. On my wingsail rig, the aft part of the sail is actually inside the wrap- around panel section, so the transition will be very smooth and well sealed indeed. An overview of my sail setup looks exactly like a drawing by Tom Speers showing the most effective possible combination of wing mast and sail-I have 2 sketches on my site showing this, and a link to Tom's webpage showing his drawings and math. See:
Aerodynamics of Teardrop Wingmasts

Sleeves have suffered from a couple of problems in the past-it was hard to hoist or furl the sail because of the drag of the cloth on the mast, and they weren't true foil shapes. I have pulled the sail cloth away from the mast by intervening battens, so only the battens touch the mast. The other drawback was that they weren't true foil shapes. My carbon fiber battens give the foil panels exactly what Tom Speers recommends-Clark Y sections.

Another issue which has had a negative effect on unstayed mast sail trim in the past has been the effect of mast bend on sail draft. This problem defeated Chris White, who otherwise likes unstayed masts on multihulls very much. I have completely eliminated this effect by using hinging battens to provide camber. Mast bend can't affect the camber of my wingsail design, because its camber is not provided by the usual method, which is to have a forward curve cut into the luff which throws camber into the sail when pulled up a straight mast.

My 'traditional looking' sail also more closely approximates the ideal planform for maximum lift and minimal drag-the ellipse. I think people will be very surprised indeed when a sail that looks like something from centuries ago turns out to develop more lift and less drag per square foot of sail area than the marconi rig, and zooms right by them. I think the lack of standing rigging is a benefit from a drag standpoint, but I don't count on it for a large improvement.

Steve Dashew used to put under boom bonnets on the bottom of his mainsails on his Beowolfs, to seal the sail bottom against flow under the boom, before be became a powerboater. He thought they were very effective, but I did the math and noticed that his increase in boat speed was directly proportional to his bonnet size, when compared to the boat speed and his sail size-that is adding say, 7% of bonnet gave him about 7% more speed-so the effect is real but not huge. "Park Avenue" or plank booms aren't new, either, but they never became very popular.

If you can't afford a big boat, how about buying a used Hobbie 14 or similar? They don't cost much, and are loads of fun-It is pretty tough to turn the smallest beach cats over if you take a friend sailing.
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Old 29-06-2008, 12:55   #154
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Quote:
Originally Posted by sandy daugherty View Post
Hi BigCat! Bernouli is hard at work on both Junk Rigs and assymetrical airfoils flying upside down. Inverted, a conventional wing is able to fly, but at a much higher angle of attack than right side up. Bernouli isn't completely happy with the situation, and complains with a whole bunch more induced drag, which requires a lot more power from engines that are designed to run tight side up (the oil sump is empty when the engine is upside down) so inverted flight is in most cases a no-no. But there are fixes for all these little problems, hence airobatic and flight demonstration aircraft.

What a lot of people missed about Junk rigs is that Bernouli speaks Chinese too. Those old sails were NOT flat boards. They curved in the wind because they were anchored towards the front and the control lines were tied to the aft ends of the battens. However, those more recent Chinese sail designers didn't speak Bernouli, and they had different reasons why tapered battens worked better! Just as airshow crowds were baffled by inverted flight, Junk sailors were amazed that junk sails worked when the mast was on the wrong side of the sail, giving it a funny "S" shape. The truth is, a little Bernouli goes a long way!
Hi, Sandy - I built and sailed "Batwing" across the Pacific Ocean. See my website for a drawing- and its rig was designed by Blondie Hasler. Whatever foil shapes the ancient junks may have had, Blondie didn't give in his designs. My junk sail was as as 'flat as a wall,' as Arne Kverneland ( home.triad.rr.com/boatbarn/arnek.htm ) said. It would tack through 100 to 110 degrees, which certainly isn't sparkling, but is definitely to windward. Arne's website shows the progression of his improvements of the junk sail from no camber through two different methods of using camber, and the great improvements he gave his sails thereby.

I can't really comment on the theoretical aspects of Bernoulli versus Newton, because the details go right by me. Fortunately, the design of effective rigs and their trim doesn't require a grasp of the finer points of theories which even Ph.D's debate.
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Old 29-06-2008, 13:08   #155
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Sandy, I've looked at these plans before and the first thing I note is that each sail approximates to a wing and remains clear of lumps like masts etc. giving really good airflow. Leading edge stalling can be balanced with the shape across the sail and timely trimming or self trimming sails (do the ones shown react laterally, swinging across the boat around the mast, to the wind direction?)
I agree with your comments on fairing from the lee edge of the mast, if it is worth doing for race, fast cruise it's not that hard but for day sailing it's another compplication. The first option is the part rigid wing with some mechanial bias to keep the lee face smooth and aligned. In conventional rig I have wondered if it is better to have a gap between mast and the leading edge (luff?) of the sail?
Price wise I'll be limited to an older prout. Re-rigging could be by extending the mast upward with a three foot extension in the foot. It means new standing rigging and sails so is a major cost but maybe - . A free standing mast might be worth a look, shorter maybe but with better sails.
The 'bonnets' seem to prove it's basically a sound idea. It's got to be light but does work well. A 7% improvement is cheap if achieved in the right way. I'm considering heavy sail cloth to either side with the same fixings as a marina sun shade. Water gathering seems not to bein fashion? Great for washing and cooking but the American cruisers in particular still seems to burn energy for comfort, they don't payeuropean rates for their diesel.
I'm surprised the rear mast hasn't developed into a gaff rig with forestay tension maintained by a back haul off the end of the gaff?
Rear masted cats today really should have self supporting masts now but most seem to prefer patio doors! Where have the production adventurers boats gone? Fastcat seems to be trying very hard with lighter builds and attention to almost every item but doesn't seem to get much praise on this forum.
I think the hybrid drive is a long way off being practical, it still needs a diesel to give a few days motoring time though it may be time for diesel electric drives as pods get better. Don't need drogues in bad weather either, just generate and keep warm and well lit instead.
I hope diesel prices remain practical for my cruising days, I'm hoping for ten years or so and do I wish I'd done it when I was twenty (1965) but girls were more important then. Warm winds, calm waters.
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Old 29-06-2008, 13:48   #156
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Fastcat - shameless marketer or bold innovator?

Eleven, I think Fastcat has gotten quite a bit of praise on this forum. At least two posters are buying one, and others have said that they wished they could. He has gotten a lot of criticism for going too far with his advertising / propaganda efforts, as well, which some frank suspicion being inspired in the occasional poster. I think 'both' Fastcats are real-Fastcat 'A' is an 'over-the-top' marketer who exaggerates and even distorts the truth occasionally, and Fastcat 'B', is a very dedicated and disciplined boatbuilder and sailor. The alternation between the two can be disconcerting, of course, and inspire a great deal of skepticism.

When caught out in exaggerations and distortions, Fastcat 'A' simply quits the argument rather than conceding the point, and he doesn't help himself with that--my debates with him about vinyester versus epoxy are a case in point. The actual specifications of his actual epoxy resin and my actual vinylester resin demonstrate that my vinylester is actually stronger than his epoxy-he, on the other hand, tries to pretend that vinylester is just another polyester in its properties, which is quite untrue.

(See: http://www.interplastic.com/UserFile..._CycleTest.pdf for the differences between vinylester and the two kinds of polyester resin in wide use.)
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Old 29-06-2008, 14:03   #157
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First a general remark:
God I love these open debates! There are so many opinions searching for facts! Staid old fashioned objective investigation (purely boring!) mandates drawing no conclusions until all the evidence is rounded up and studied to see what facts can be derived. This is absolutely no fun, and unhealthy, because leaping to a conclusion is just about the only exercise I get!
Rigid objectivity strictly forbids anecdotal evidence. Post hoc, ergo procto hoc reasoning is against the law! [It follows, therefore it is caused by] Here we can begin with an inspiration, nourish a fascination, and then valiantly defend an obsession, gathering support and justification from a wide range of sources, with little fear of reprisal based on missing the context or drawing conclusions from irrelevant facts.

Second: In defense of Bernouli: Barn doors fly. It takes a tornado, but they can fly as well as cows and houses and little dogs named Toto! They fly much better if they are shaped like a wing. God knew this, but he made flat-winged butterflies that cruise 4000 miles, and camber winged birds who can't fly over a frying pan. I think he did that just to show its a bad idea to draw a conclusion without doing a lot of research and testing. Things like laminar vs turbulent flow seem relative obscure, but the WWII fighter that could control where that happened could shoot down a fighter that couldn't. That's how wars are won. The point is that little things count. Square riggers evolved from a purely down-wind sailing tradition, until someone discovered that they could be sailed above a broad reach if the shape of the sail could be curved like a beer belly. Who ever got to market with the goodies first got the best price, and finding a sailmaker who could build a faster and more weatherly sail became an economy, not just an effete intellectual exercise by the astrologers of the day. It required big crews, running around, constantly adjusting sails for a certain point of sail, but this was the rocket-science of the day! So, over the years, strange ideas were tried, and some succeded (keels, for example) but for the most part, performance increased incrementally, as a result of the best minds available being fascinated with the subject. They didn't miss much. So there probably isn't "anything new under the sun" or a brand new way to do things better.

Thats why the next America's cup boats (catamarans) are going to cost much more than years in the past, the new rule allows a nearly blank sheet for design and the designers have started with a boatless sail optomized for a particular set of sailing conditions. When they got that, they next searched for the best way to carry that sail rig, and came up with a catamaran, engineered to perfectly fit the loads generated by that sail plan, with no cares about cost or difficulty in construction. They might have considered Mr, Eiland's mast aft design, but I guess they decided against it. I guess they thought it was OK to stick with a vertical mast, but I am positive they didn't make that decision based on convention; they RESEARCHED it, and evaluated all the loads, and came up with a vessel with a single design goal, to win.
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Old 29-06-2008, 14:13   #158
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So any guesses what it will look like. A hobie?
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Old 29-06-2008, 14:22   #159
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"Square riggers evolved from a purely down-wind sailing tradition, until someone discovered that they could be sailed above a broad reach if the shape of the sail could be curved like a beer belly." Actually, you reduce the camber of a square rigged sail to sail to windward. The Vikings used a device called a "beitass," to sail to windward with a square sail. In the days of the square rigger, sail cloth had a lot of stretch, so the sails all had a lot of belly. The Vikings also worked to flatten their sails also with a criss-cross of diagonal reinforcements.
See: Hurstwic: Norse Ships
See: Beitass - Wikipedia, the free encyclopedia

As far as the America's Cup goes, why not a giant Hobie? It's been done before:
See: 32nd America's Cup Official Website - 1988 - Stars & Stripes US-1 Catamaran

(Speaking of wingsails on catamarans!)
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Old 29-06-2008, 14:30   #160
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FlatTER is not FLAT.
but thanks for the cool refs!

Here is today's Alinghi:
SAILKARMA.COM - Sailing News, Videos and Photos!: Alinghi Extreme 40 Cat Video

Hey Steven, if you're still here, this cat is BLACK!
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Old 29-06-2008, 14:39   #161
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FlatTER is not FLAT.
but thanks for the cool refs!
Never said it was! Indeed, review my above comments about putting camber into flat sails!
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Old 29-06-2008, 21:57   #162
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You should look at Grainger or MTG for design consulting.
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Old 30-06-2008, 13:08   #163
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Cat or Tri

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..Thats why the next America's cup boats (catamarans) are going to cost much more than years in the past, the new rule allows a nearly blank sheet for design and the designers have started with a boatless sail optomized for a particular set of sailing conditions.
Not so sure that this is the case?? I believe the cats are being used in a teaching mode, but trimarans may be the final form for AmCup.

Funny how the originally Formula 40 started out this same way in France.
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Old 30-06-2008, 14:01   #164
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If you look around the marina's in NZ 20% of the boats would be designed by the NZ designer Frank Pelin , Power and sail, I watched a 40ft cat design of his being built and I will say I was impressed they can be built out of cold molded marine ply or glass he has 2 sizes in the off shore range 40ft and 45ft ....Worth checking out
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Old 21-04-2017, 07:34   #165
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Re: New design - opinions / idea's wanted

Thought I would bump this subject thread back into existence so I would remember to go back and read thru it. Can't remember how much good material there was in it?

I'm going back thru some older ideas/designs/etc looking for ideas to consider in designing an alternative fishing-sailing cat for Jimmy Buffett in lieu of that monohull he is having built.
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