Rigs

[Meerkat]

Seems like most of the smaller boats one sees these days use a lug rig. Personally, it's the rig I appreciate the least. I'm not particularly fond of any rig that does not have a headsail actually, but I really don't like lugs at all. Is the reason for their widespread use in current designs a matter of cost? Are there any nice gunter, gaff or marconi sloop or cutter rigged designs out there, aside from Selway-Fisher, who tends to like gunter best...?

Butterflies are nice. Lateens are nice, but seem a bit clunky to tack/jibe.

[Captain Pre-Capsize]

Mark this as a first, a civilized post from 'Da Meer! Must be the Christmas spirit?

Hey, I like my sprit on my eleven foot skiff with but one exception. When running the loose footed rig collapses upon itself. So I don't run - need to stay off a bit to keep the sail full. Bugs me a bit but so far I seem content to write this off to "character".

Does anybody know if a loosefooted sprit can have a boom? I know, duh, then it's not "loose"! Sure would help keep it tight when running. Or perhaps another spar that keeps the bottom of the sail (is that the "foot" - wow, what an amatuer!) tight? How would it attach to the mast? This is only a 49 square foot sail - maybe I need to relax but my concern is that the loose foot may continue helping keep my name a valid one. ;)

[Bruce Taylor]

Mark this as a first, a civilized post from 'Da Meer!Meerkat has been a frequent contributor in the upper sections. His posts up here are generally quite civil, and often generous and helpful.

What's your problem w/ lugs, Meer?

[N. Scheuer]

I believe one attraction is having a comparatively large mainsail on short spars, while keeping things simple.

I like my Leg-o-mutton sprit sails, but more sail area on a shorter mast are possible with the lug.

Moby Nick

[Meerkat]

Bruce; First, thanks for mentioning my posts "above decks"! ;)

Issue with lugs is firstly aesthetics. I just don't care much for the way they look. Secondly, stemming in part from the first, I think any boat without a headsail looks undressed - "bald headed" (even if that's probably not the original meaning of the term). Thirdly, also stemming from the first I guess, is the asymetry - on one tack, the sail is flying from the spars and on the other, it's draped over them (at least at the mast). Whatever the aerodynamics of it, it just looks (being polite) clunky to me. Lastly, and maybe most subjectively, I learned on a sloop and was taught about, and observed, the slot effect in action and higher mainsail performance because of it. Tightening the jib just right really made her show her heels - no mean feat in an O'Day 24' cabin sailboat with an outboard trailing off the stern ;)

Anyway, why the current popularity?

[Bill Perkins]

Unstayed masts are handy on small beach boats .Quick in , quick out; including jerking the rig out, or setting it while afloat .If you're landing down wind , or are overpowered at anytime you can let the boom swing forward till it points straight down wind ,which can be a big help .

Jibs work against these simplicities . you'll never get the luff of the jib tight enough to work with the efficency you've admired on a Marconi rigged sloop without staying the mast. Also the further forward one can place the mast on a small boat the more room for the people .

[ 12-20-2003, 05:09 PM: Message edited by: Bill Perkins ]

[Meerkat]

Good points Bill - thanks for the post!

I don't mind going to the trouble of connecting a couple of stays, especially if they're lanyards (I think that's what I mean). I like the (maybe illusory) peace of mind they give. I'm also less concerned with bodies per boat than I am with getting a move on (short, I hasten to add, of an all out "standing on her ear" racing boat!). I'd like a little more go from the blow! ;)

[Captain Pre-Capsize]

Meer:

I owe you an apology, I'm sorry. It's just that your post is so helpful above and in the bilge, well...

Ah, shut up Captain! Remember you are Pre-Capsize after all - a beginner. It is commendable Meer that you compartmentalize things and thus keep things civil up here. Thanks on behalf of all of us. It is nice to have an outlet down there though.

[ 12-20-2003, 05:09 PM: Message edited by: Captain Pre-Capsize ]

[Bruce Taylor]

As Bill & Nick say, the lugger lets you put a lot of sail on a short spar w/ low CE. A short, unstayed mast is not just good for a quick launch...it also permits you to strike the rig while at sea, and stow the spars on board. With the spars down, you can continue under oars or motor, or put your boat in tow. A stayed rig on a rowboat/sailboat is an obvious hindrance.

Despite its simplicity, a lug can be trimmed & tuned to a nice shape, and with just a few lines. It can be peaked quite high, if you should wish, giving a much better aspect ratio than the short mast would lead you to expect. If you should wish to douse the rig quickly, it can be brought down in a great hurry (just release the halyard, and down she comes).

The asymmetry of the various lug rigs -- a feature they share with the lateen, which you say you like -- doesn't noticeably affect their performance.

Anyone who installs a lug rig is probably looking for simplicity, so the lack of a headsail will likely be seen as an advantage.

The aesthetic question is unanswerable. I like the look of a lug. "Clunky "is high praise, in my books...right up there with "funky". smile.gif

As for the "slot effect"...I have half a mind to start a thread on that. There are those who say it's a myth, and I'd be curious to hear what folks here have to say about it.

[ 12-20-2003, 05:47 PM: Message edited by: Bruce Taylor ]

[Meerkat]

I like the look of a lateen, but not much it's foiables in tacking and jibing - see the misc. boat related thread on the subject (LOTR "Lanteen"...).

De gustibus non est desputandum of course when it comes to aesthetics. smile.gif (Il Porcupino Nil Sodomy Est too, but that's another point entirely ;) .)

Slot effect works - sound aerodynamic theory behind it. I'm interested in your opinion though. smile.gif

[Bruce Taylor]

A few years ago I ran into a guy who claimed that wind tunnels experiments and computer simulations show the slot effect doesn't actually occur. Since then, I've read a few skeptical comments about it...enough to raise my interest, at least.

I don't know nearly enough about aerodynamics to offer a useful opinion.

I know the value of a well-trimmed headsail, of course (play with the jib, and watch your speed fluctuate).

[Meerkat]

I don't know enough to really comment much either, but the venturi effect (technical term for slot effect) does exist - turbofan jets are proof. It may be one of those things that is really only useful if you've got air moving at a gazillion mph to get any boost from it... maybe trimming a jib is more a matter of making the most effective use of the sail's area...calling any geeks that might be able to comment more! ;)

[Frank E. Price]

Sure, the venturi is real, but is the slot effect the same thing? Someone (Maurice Griffiths I think) wrote about early experiments in British dinghy racing. A major item was how best to distribute sail area when it is all measured, including the overlap in the jib. The imperical conclusion was that sail area provided the most power when it was in the main and the jib was kept small and not overlapping. From that I infer that the slot effect is little help, unless it is had from unmeasured sail area. And personally, I'd rather deal with a big main than a big jib.

As for booms on sprit rigs, I think Chapelle's drawings include a few with sprit and boom, or sprit and sprit-boom. My one-sail sharpie skiff is jibheaded with a sprit-boom. Very handy; I love it.

Frank

[Meerkat]

We need a techie to weigh in. John Hardiman, et. al, are you listening? ;)

[Jack Heinlen]

There are all kinds of handy small boat rigs, but a loose-footed gunter main, with a small jigger, jib on a roller, is a pretty handy, weatherly rig. It's a good compromise.

That's my story and I'm stickin' to it.

[johnw]

Lugs with booms are surprisingly common in this country. Every Pelican has one. They also have a jib. Have a look.

http://community-2.webtv.net/pelicansailboat/SFPELICANSAILBOATS/

I've only sailed a few lug rigs, but I have to say, few of them worked well to windward. Pelicans go better than most.

[Meerkat]

Point of enquiry here. Isn't a sail that has a boom, but whose foot is not lashed to the boom except at the outer end of the boom, considered loose footed?

[Meerkat]

I'm not sure that Pelicans are lug rigs. It's impossible to tell for sure from the pics, since the yard join at the mast is hidden by the jib, but I thought they where gaff or gunter rigged?

[Aramas]

As for the "slot effect"...I have half a mind to start a thread on that. There are those who say it's a myth, and I'd be curious to hear what folks here have to say about it.

Slot effect works - sound aerodynamic theory behind it. I'm interested in your opinion though AH - one of my pet peeves!
Sure, the slot effect works, and it's sound aerodynamic theory - on STOL aircraft! The only real world application of the slot effect that I'm aware of is the leading edge slots on aircraft. Their purpose is to forcibly deflect air around the leading edge in order to increase the angle of attack at which stall occurs. At low angles of attack the wing operates normally with the slot inactive. Important if you want to yank a plane off the ground and point it at the sky, but completely and utterly irrelevent on a sailboat. I mean, when was the last time you thought "Oh god, I better not point lower than 20 degrees or my boat will fall out of the water!" Sailboats operate perfectly well off the wind - hell, they can even go in the same direction!

Whatever it is that yachties refer to as 'the slot effect' is quite different from the 'sound aerodynamic theory' as applied in STOL aircraft. However you look at it, removing the mast and making the whole rig into one sail will increase it's efficiency. The 'yachtie slot effect' is just a bit of fiddling to partially backwind the main and perhaps improve sail shape and flow in spite of having a bloody big stick and a hole in the middle of the foil.

Unlike aircraft, boats are using lift to drive them, rather than to counteract gravity. The most efficient sail arrangement would be a single glider wing (high aspect ratio asymmetrical laminar flow foil) stuck on the boat and kept rotated to it's most efficient angle of attack (ie maximised lift/drag ratio) and kept vertical. In that scenario leading edge slots might indeed be useful as they would allow cranking up the angle of attack, producing more lift without increasing drag proportionally (deferring stall).

Then again I could be wrong smile.gif

[ 12-20-2003, 11:25 PM: Message edited by: Aramas ]

[Steve Paskey]

I don't have any experience with a lug rig myself, but I'm hoping John Welsford will drop by, as I'd be very interested in hearing his comments. John seems to have a keen interest in good sailing performance, and his design catalog abounds with variations on lug rigs. On a number of boats he uses a standing lug with a sprit boom, either individually (Rogue and Houdini) or as the mainsail for a yawl with a jib (Navigator and Pathfinder). Other designs use a balanced lug as the mainsail on a cat yawl (Walkabout, Tread Lightly).

[John B]

I think I'd have a play with a lug rig if I ever get around to building a new tender. Shorter spars and some balance forward of the mast so the mast doesn't have to be so far forward for a given area.

You know, hearing people say they don't believe in the slot effect is a bit like placing credence in "Moon landing was a fraud" to me. If , in the future, its absolutely proven that the slot effect is myth( which I rather sincerely doubt), what I think we'll find is that there's another reason why a jib in front of a main goes so well.
for example, a jib adds power in the eyes of the boat helping to punch you through a chop.
A small example. a few months ago, I put up a post on an American catboat built here in NZ in the 1930's. It wasn't successful. It couldn't keep up with the similar boats( and they are remarkably similar) .They moved the mast, put on a bowsprit and a jib, and it became a boat better suited to the typical Auckland conditions.

I mean the subject is too massive to refute in some ways. We've always had a big main on our boat which we've sailed in all sorts of combinations and all sorts of breezes. The addition of a jib in any given situation has always seemed to add HP well out of proportion to its size to me.

Its interesting, as Bruce says, but I'm skeptical to say the least.

[htom]

Take the halyard of your lug rig and run it to the bow rather than to the partners, and hank your jib onto it. You'll have to rig something to run the jib halyard over and it will be beyond messy if you have to lower the lugsail with the jib set.

The slot effect is real, but I suspect that at typical air-over-sail speeds that it's swamped in other problems. The rig to test it would be one of those rear-mast things, with two forward stays, adjustable in separation. Sail with one sail, then with two. Going to be a pain to tack; what you gain you'll probably lose going through stays.

[Meerkat]

Aramas; I'm not arguing with you, but maybe you're forgeting things like aspect ratio, speed and Reynolds Numbers? Consider that boat's underbody is an aerodynamic structure - by virtue of the viscosity of the medium it works in, it's operating in the equivelent of a hypersonic flight regime. In a like way, a jib, operating at a tiny fraction of that of a 100 Kts/hr jet aircraft wing (or even a prop driven STOL a/c at 40-50 kts/hr) and with a far lower aspect ratio is operating in a different "flight" regime in relation to the mast and it's low aspect ratio.

That high aspect "glider wing" airfoil you suggest would have some pretty severe stall characteristics, as do all high aspect airfoils.

[John E Hardiman]

I heard my name mentioned.....so below are my opinions from the available data as I see it.

Tall thin rigs are more efficient IF you can manage the angle of attack (AOA) along the leading edge (not bloody likely in a real situation with the boat pitching and rolling).

Cascade rigs are less efficient unless AOA is changing rapidly (implies forward velocity is small compared to wind speed) and aspect ratio is low.

INCREASED COEFFICIENT OF LIFT IS NOT THE SAME AS INCREASED THRUST!! I said this before just recently in another topic. I'm not being flip, just that VMG to weather is the only real measure of performance that means anything to a sailor. Any hunk of rag hung up will improve off the wind preformance. The ability to work off a lee shore is the true measure of a rig. While some of the high speed craft are engineering delights, they have no practical applications as VMG to weather is very low even though speed over ground is high.

A well trimmed jib ahead of a larger main sail functions similar to a slat on an STOL wing in that it controls the AOA into the larger planform by physical means ( similar to a kort nozzel). It does not increase "lift", but rather "flattens" the lift curve making it less "peaky" and less subject to stalling during AOA changes.

The tradeoff in a sail is between aspect ratio and center of effort. Aspect ratio controls the ability to go to weather, and center of effort the heeling moment.

The details, such as air gap above the water, leading edge straightness, weight aloft, rigging drag, sheeting angles, quarter cord line, mean rake, ability to prevent twist-off, camber control, etc. can so over shadow aspect ratio and sail efficiency as to render any advances in sail planform useless.

Slow and steady wins the race. Starting with a given rig and wringing it out may be better that trading for rig with many more unknowns.

I always remember the 4-masted, single handed 236' Club Méditerranée built for the OSTAR. She had it all in terms of rig efficiency; and lost to the 73' Pen Duick VI .

[Meerkat]

Wow John. I guess you nailed that! smile.gif

So, am I right that a low aspect gaff sloop or cutter is a good performer from what you said above? Um... BTW, how low an aspect, and what are the trade offs to a low aspect? (I know in wings it limits top speed...)

[John E Hardiman]

Originally posted by Meerkat:
BTW, how low an aspect, and what are the trade offs to a low aspect?The data is all scattered because "aspect ratio" gets defined differently by many people and you don't have all the data to standardize it all; the major ones are:

AR=span^2/area
= span/mean cord
= 2*span/cord (measured at the root, mostly aircraft data)

Generaly "low aspect" is 2-3, "high aspect" is 5-6.

Aspect ratios are somewhat related through things like "taper ratios" and "planform coefficients". Note that most of the general reasearch is old '30's-'60's; and any new stuff is being held close to the chest in the VPP programs.

[Aramas]

Meer - I didn't follow your post-before-last at all. Looks like nonsense to me smile.gif

JH is talking real-world rigs whereas the bit about a glider wing was an idealised situation - it would work on a flatwater cat or sailboard for speed records, but not something one would take sailing on a sunday afternoon.

I suspect that the main reason that foresails produce more drive per square metre is that they don't have a big fat pole on the leading edge detroying the flow.

In order to make the statement that the slot effect as applied to sailboats is 'proven aerodynamic theory', one should establish just what it's supposed to do and what it's supposed to be better than. So here's a gedanken experiment to compare a hypothetical rig - a cat with an A-frame rig is tried in 3 configurations:

1) Standard sloop - the main is set on a thick spar to simulate a mast, and the foresail is set on the forestay normally.

2) A-frame sloop - both sails are set on stays.

3) One large sail of the same shape and area of both main and foresail is used.

Which will perform better and why?

Additionally the A-frame is rigged on a large roatating disk that allows the angle of attack of the entire rig to be tuned.

Which rig will perform best now and why?

Do you still think the 'yachtie slot effect' is the duck's nuts? At best it partially diminishes the negative effects of a fundamentally flawed foil over a small range of angle of attack, only with optimum foresail overlap and only when sheeted flat (and even then it's uncertain whether better performace could be obtained by slacking the sheets).All of which is not at all the intent of putting slots on a STOL wing.

WHile Oblio did have a point about not having one, it is traditional, so I suppose I should. IMO, the slot effect could be useful on a sailboat only under very specific conditions - conditions which may be of interest to racers, but would be largely irrelevent to cruisers. It's not at all a case of just whacking on a headsail and achieving instant slot effect at all points of sail, sheeting positions and conditions.

[ 12-21-2003, 02:19 AM: Message edited by: Aramas ]

[Meerkat]

Interesting - power a/c can be 10+:1 and sailplanes regularly go over 14:1 (I think high performance is 22:1 and above, although the last I recall reading, 24:1 was considered a max due to materials strength). Being light in this area, I was unaware that there was more than one way to measure aspect ratio. All I know is span:root chord.

All I can say is that I prefer a higher aspect ratio rig to a lower aspect one. Gaff or gunter of course ;)

[John E Hardiman]

Meer;

It sounds like your using "wingtip-to-wingtip" as span which is 2*span (root-to-tip)/root cord. As I said, common for aircraft. You need root-to-tip to calculate "taper ratio" to determine the spanwise loading curve for aircraft. Not so important in sails due to the "plate effect" of the water surface.

[Meerkat]

http://www.cachesoaring.org/images/Blanik_in_Grass.gif
A Blanik sailplane. Possibly the same or a later model of the plane I soloed in. Note the lack of twirly bits on the front ;)
Wing Span 53.1 ft / 16.2 m
Wing Area 206 sq ft. / 19.1 sq m
Aspect Ratio 13.7
Airfoil NACA 63(2) A-615root, -612, tip
Wing Loading 5.35 lb per sq ft
26.17 kg per sq m

Max L/D 28 @ 49 kts / 28 kph Flaps deployed
Min. Sink 2.5 fps / .76 m/s @ 39 kts / 72kph
Seats 2
Empty Weight 644 lbs / 240 kg
Payload 458 lbs / 171 kg
Gross Weight 1102 lbs / 411 kg

IIRC, this plane was said to have a 14:1 aspect ratio (oops, I just noticed the aspect ratio figure in the specs - I wuz right, more or less! smile.gif ). At a touch over 16m total span, that would be consistant with your length*2/root as aspect ratio. (At this aspect ratio, the plane is not considered a contest contender for speed and acrobatics, although it is acrobatic capable.)

As long as I've wondered off the main topic, there's a tale to be told. The instructor was a British Indian who had flown Spitfires in India during WWII. One day, late in the afternoon, on what may have been my pre-solo check ride, the instructor decided that we would not be flying any more that day. As we had a fair amount of altitude, he promptly took the stick ("I have the aircraft!") and dove on the parking apron, pulled up about 6' off the deck, climbed so far, skidded in about the plane's own length and came back down and landed her literally in about 40'. Scared the holy cr*p out of the ground crew and I had to about be poured out of the front seat! :D The good news was that she was about 15' from her tiedowns and she was put to bed in short order. An unforgettable memory! We went back to the base (this was in western Oz in the Navy) and he went back to his job running the diesel electric plant.

[Aramas]

A Blanik sailplane hey - I think I soloed in one of those too, at Benalla in Victoria (AU). Ugly buggers, but built like the proverbial brick outhouse.

[Meerkat]

UGLY!!!! YOu call this thing of grace and beauty UGLY? You philistine!!! tongue.gif

You're right about them being strongly built though - kind of like a Czech farmgirl! ;)

[ 12-21-2003, 02:56 AM: Message edited by: Meerkat ]

[Todd Bradshaw]

There is a superb chapter in Tom Whidden's book "The Art and Science of Sails" (chapter 5)dealing with main/jib interaction which is a very worthwhile read if you want to get down to brass tacks on the issue as it relates to sailboats. Tom's not too keen on the standard Slot Effect theories either. It's way too long and complex to do justice to with any kind of paraphrase, but here are some highlights from the end of the chapter, minus their detailed explanations which are written earlier. He approaches the subject not only in terms of the jib's affect on the main, but also in terms of the main's effect on the jib with both factors contributing to the sailplan making the boat go. (the rest of the book is also well worth reading). Apologies to Tom for any typos, I'm a lousy typist.

"How the Mainsail Affects the Jib:

1-The flow ahead of the mainsail causes the stagnation point on the jib to be shifted around toward the windward side of the sail (a lift), and the jib can be pointed closer to the wind without the jib luffing. This lifting is upwash.

2-The leech of the jib is in a high-speed flow region created by the mainsail. The leech velocity on the jib is, therefore, higher than if the jib alone was used.

3-Because of the higher leech velocity, velocities along the entire lee surface of the jib are generally increased when both jib and main are used, and this contributes to the high efficiency of the headsail.

4-The higher lee-surface velocities of the jib mean that the jib can be operated at higher angles of attack (more trim) before the jib lee-side flow will separate and stall.

5-Because of the aforementioned, proper trim and shape of the mainsail significantly affect the efficiency of the overlapping jib. Anything that causes a velocity reduction in the region of the jib's leech, such as some separation on the aft part of the main, results in the jib contributing a lower driving force.

6-The trim of the main significantly affects the pointing ability of the boat, for it directly influences the upwash that approaches the luff of the jib.

7- The drag from the mast - in front of the mainsail - has always been blamed for making the main less efficient than the jib. Another, probably equally important factor is the increased velocity on the jib, and the fact that the Kutta-condition requirement (explained earlier in the chapter - in short, it means that the flows coming off of both the windward and leeward trailing edges of a foil are traveling at the same speed - T.E.B.) of the jib is satisfied in a local high-speed flow region that is created by the mainsail.

How the Jib Affects the Mainsail:

1- The jib causes the stagnation point of the mainsail to shift around toward the leading edge of the mast, placing the mainsail in a header. This is downwash.

2-As a result, the peak suction velocities on the forward-lee side of the main are greatly reduced. Since peak suction velocities are reduced, the rise in pressure is less abrupt.

3-Because the speed of the flow is reduced on the mainsail, the possibility of the boundry layer separating and the airfoil stalling is reduced.

4- With the jib up, a mainsail can be operated efficiently at higher angles of attack (more trim or higher traveler angle) without flow separation and stalling than would be the case with just a mainsail alone. This, too, is caused by a reduction in velocities over the forward-lee part of the mainsail. Since the air is moving fairly slowly at the front, further slowing at the back to satisfy the Kutta condition is not a dramatic event. This disproves the slot-effect theory. If the air were speeded up in the slot as the old theory promises, the air on the main would be more likely to separate.

5-Much less air goes between the headstay and the mast when the jib is placed in the flow with the main. The circulations of the main and jib (also explained earlier in the chapter - T.B.) tend to oppose and cancel each other in the area between the two sails, and therefore more air is forced over the lee side of the jib."

Anyhow, it's a good book and not all of it is this dry, technical theory stuff. There is also a lot of practical information on getting the most out of your sailplan, sail construction, etc. And by the way, unlike the big middle eastern lateen-rigged boats, most modern-style, small-boat, boomed lateens tack and jibe very easily

[ 12-22-2003, 03:46 AM: Message edited by: Todd Bradshaw ]

[rbgarr]

Thanks, Todd, for the summary of Whidden's chapter. When I first got his book, I had to read that chapter over and over, carefully following his drawings, before I finally understood it and the implications for sail trim. How sails actually work make so much more sense to me now.

The most practical demonstration of the myth of the slot effect is to light a cigarette and watch the smoke trail when you sit or stand to leeward of the main in the area between it and a genoa when hard on the wind. The air movement is very disturbed, mostly spiralling upwards(!) from my observation, rather than showing signs of 'speeding up' to create any kind of additional thrust.

[ 12-21-2003, 08:26 AM: Message edited by: rbgarr ]

[Meerkat]

So, does this, or does this not, suggest that a boat with a headsail works better than a boat with only a mainsail? It sounds to me like, whether or not it can be attributed to slot effect, that it does...

[Tonyr]

Here is a slightly different point of view on having a single lug sail, perhaps. I like my 84 sq ft balanced lug (fully battened, boomed, loose foot) on a 17 ft Whitehall because it is a SINGLE sail, which a solo sailor can hoist and lower quickly when under way, control with a single (multipart) sheet with one hand, let fly when overpowered and ride out a gust, reef easily and quickly when under way, and drop completely when things get too rough. All this with an unstayed and relatively short mast.

For really heavy weather the lug can be replaced on the fly, as it were (well, within five minutes anyway) with a 40 sq foot simple leg-of-mutton hoisted on the same halliard, and using the same boom (two point contact, remember, so easy to change sails).

In theory you could then add a jib to the leg of mutton, say of 20 to 25 sq ft, but with lots of wind (by definition) it has never seemed worth the complication, since the boat is already going at hull speed anyway, in those conditions.

The upwind theory of slots and so on is all very well, but the sheer ease of getting somewhere with a well cut single lugsail makes it more or less irrelevent, I have found.

Perhaps if I was racing, instead of cruising, I would have a different opinion.

Tony.

[ 12-21-2003, 02:40 PM: Message edited by: Tonyr ]

[Meerkat]

Said John: "The ability to work off a lee shore is the true measure of a rig."

I agree! So, how does a standing lug measure up in that regard?

[Bruce Taylor]

Meer, there is no "true measure" of a rig. Different rigs serve different needs.

Designers like Iain Oughtred, John Welsford, Phil Bolger and Joel White don't put lug rigs on some of their designs because they're too thick-witted to realize that a tall Marconi might point a few degrees higher. When they draw lugs, they do so because they offer the right mix of features for certain types of boats.

As you probably remember, I chose a standing lug for my camping boat. A stayed Marconi would have been completely impractical. I needed a good spread of canvas to drive her when heavily loaded; but CE had to be kept low, since she's a narrow boat with fairly low freeboard and no decks. I needed to be able to raise and douse the rig quickly (preferably without standing up in the boat). I wanted to keep the mast (and all spars) shorter than 12', for convenient stowage, while allowing the peak of the rig to rise to 16' or more.

I considered various other rigs (sprit, leg o' mutton, gunter, solent), but chose the standing lug because I've had good experiences with it in the past. Really, my only complaint about the rig is that it can be hard to control twist on a run (John Welsford's sprit-lug is supposed to address this, and I might switch to it one of these days). In short: it's a good rig for the job.

[ 12-21-2003, 03:31 PM: Message edited by: Bruce Taylor ]

[Captain Pre-Capsize]

Way too much thinkin' going on in this thread... :rolleyes:

[ 12-21-2003, 03:30 PM: Message edited by: Captain Pre-Capsize ]

[Meerkat]

Bruce; I hope we're not arguing here - that's not my intent.

I think John pointed out that pointing ability isn't the important factor, it's DMG to windward that is! Makes no difference how high you point if the boat is still being blown onto that leeward shore. Within the limits of my subjective aesthetics, makes no difference to me what the rig is. Marconi is acceptable, but gaff and then gunter are more so.

I have no argument with the idea that different rigs suit different purposes/answer a different set of trade offs. FWIW, Paul Fisher, of Selway-Fisher, seems to strongly favor gunters for his small boat designs.

BTW, what's a "Solent" rig? That's a new one on me!

The original notion of this tread was to enquire about why lugs have seemingly gotten so popular. My sense is that, in part because people are buying/building smaller boats that have to be kept ashore and in part because of some advantages for the casual sailor in sail management, that it's a matter of convenience, followed by cost. Am I missing something?

[Tonyr]

Meer, about lugsails and upwind ability.

So far as I can tell, there aren't any special problems here, within the limits imposed by any given boat's size, that is. More important in tweaking my particular boat's performance than the sail, was the daggerboard. I had to build a new, deeper one (three feet below the hull, as opposed to two) before I was happy.

I have never had any problems in sailing as close to the wind as any of the other (casually sailed) boats around here.

Tony.

[John E Hardiman]

Meerkat, as you keep draging my name back into this, notice that in my first post all I did was point out that a rig of any planform has increased efficiency as aspect ratio increases.

That said, the differences between rigs begins to breakdown into the details. While a lug rig with an AR of 4 and the same sailarea as a bermudian with an AR of 3 is nominaly more efficient; other things such as heeling moment, leading edge shape, camber control, twist, etc. come into play. It quickly devolves into a development/cash game where he who spends the most time/money wringing out the boat/rig goes fastest. Additionally there is the old quote from one of the early Whitbread's that "the team that wins will be the team that keeps the rig in the boat". IIRC, this was just hammered home in a recent ICCT (Little America's Cup) C-cat race where a large light softsail kicked the snot out of a very expensive wingsail (that fell down BTW).

What does this mean to the average woodenboat sailor? Not much. There is no "silver bullet" best rig that solves all the requirements for a given boat. That why the smart people avoid topics like "What is the best...." because that answer is "It depends...". The best rig for any given boat/sailor combination is the one the the sailor is most comfortable with. I have seen inordinately complicated rigs build just because the owner liked to pull strings, or like Club Méditerranée where there was only one sheet control ( and as I recall, you reefed by blowing out the sails as one man couldn't handle sails that large).

As to my VMG comment, I have pointed out before that I straddle the fence on this one. Absolute VMG to weather is just a conveiant measure, but the ability to pinch the rig up and go slowly may also be needed depending on the situation. Again, it all depends.... :D

[Bruce Taylor]

Meer, a solent rig is like a standing lug w/ the yard peaked extremely high (almost vertical). Solent is to lug as gunter to gaff, if you will. smile.gif Bolger uses it on Black Skimmer, these days. The mainsail on this one looks, at first glance, like a sprit-boomed leg o' mutton, but if you look closely you can see the yard.

http://www.ace.net.au/schooner/cabs4.jpg

[Aramas]

Way too much thinkin' going on in this thread... Seems so smile.gif In my view, the only true measure of a rig is how much the owner likes it.

[Meerkat]

Bruce; Thanks for the solent rig explanation. Welsford's "Navigator" seems to have a rig not far off that.

John; I'm really not trying to get you into trouble! ;) I appreciate your willingness to share your knowledge.

Isn't DMG more important than VMG, or is there no real difference?

Oh, I would also like to point out that I did not start this thread as a "which is better" kind of thing. I guess, at the bottom, there is a lament that there are so relatively few headsail rigged boats these days (relative of course, being relative ;) ). I was also curious as to why so many people found them attractive.

I guess, since I'm too young to be an old fuddy duddy, I'm a young fuddy duddy! ;) I like rigs with headsails and particularly gaffs, gunters and marconis in that order. That doesn't mean I don't respect other people's choices, nor would I decline a chance to sail in a boat just because I didn't like her rig. Water squirting in between the seams while she lay at anchor would difinitely give me pause though ;)

[Aramas]

The simple answer as to why I've chosen a lug rig for Gwenda (whether chinese or balanced) is several-fold.

1) I don't want to have to venture onto the foredeck to handle a jib, and I don't trust roller-reefing.

2) I want an unstayed rig - which can't provide the luff tension to get a good set from a jib.

3) I like the look of lug rigs - terribly rakish imo smile.gif

4) I have every reason to believe that they can perform well (see Romily). This factor is what sways me from junk toward balanced lug.

5) Balanced lug rigs are a (but not the only) traditional choice for canoe yawls.

[ 12-22-2003, 03:39 AM: Message edited by: Aramas ]

[John E Hardiman]

DMG vs VMG is actual distance vs potential distance.

If you've just started on a 5nmi tack you want to optmize VMG. If you're 5 boatlengths from the windward mark and half a boatlength to lee with the rest of the fleet steaming up on you, you want to pinch up and make 15 feet directly to weather. :D

[SailBoatDude]

About 10 years ago, I had a discussion with Mike O'Brien (Senior Editor WB) about a mistake while testing a different set of rigs on the same model hull form.

This was a home spun test conducted on a pond in my front yard and measurements where observed and checked across a wide range of conditions. During one of the tests on the cutter rig with 130% jib, I left a weighted dowel on the wrong side of the boat. It was just aft of the mast in the slot and I thought the test was worthless in this run, until I ran the numbers. In this screwed up configuration, the sails and boat preformed just as well as the other tack did without the dowel "messing up" the so called slot effect.

I wondered why, started asking around and came to Mike as someone who could lead me to a source for more information.

For what's it's worth, I discovered the slot effect is less important then having a headsail with some over lap. Both of the sails work better as a result of there being an overlap and that this has little to do with the "slot", but much more so in presenting a larger foil to the wind. The wind seems to "see" a complete wing from stemhead fitting back to the end of the main boom, not the believed slot effect. You could sew a flap between the mast and jib at it's leech and have little reduction in performance hard on the wind (presenting a host of other problems)

Testing has proven this out several times over. Aircraft use some similar principles, but at much greater volumes and velocities and the techniques and formula applications go right out the window in flow numbers sails normally get to see. Those aircraft numbers are effected by thrust, I'd venture to guess, as even a glider generates more thrust than it's wing would normally do in the same air flow, like in a dive for example. A sail doesn't have the benefit of that much additional thrust as do aircraft or gliders. Sure a sail sucks it's self to wind, but without the added use of gravity or a big engine spun prop.

When you stick your hand out the widow of a car, does it rise or fall because of shape or because of being forced by thrust and angle of attack? If you spread your fingers while your hand is in the air stream it still rises or falls (depending on AOA) less efficiently, but non the less. If you zipper opened a glider wing in a dive, it would still dive (a much decreased glide slope), but try this on a sail and you'd come to a halt in a boat length, because of no outside thrust. I never understood the comparisons of sails to aircraft wings, the numbers suggest it's silly.

[Caribbean SeaWolf]

To me any sail which catches wind.....
Any canvas which may be flown aloft~
All configurations of spar and cloth.....
Are fine.....

Having sailed a wood canvas canoe down the
Suwanee River with a long branch & bedsheet....
& having sailed with moonrakers and t'gallants across the grand reaches of the Pacific....

I say: a sail is a sail..... each sailor may
find love in each sail... if he looks long and
well enou'....... SeaWolf ~

[Caribbean SeaWolf]

Ummm ...also.... times were when soaring in my Schwietzer 1-26.... I oft thought-wandered
of my 63'yawl....
Times were~ when laying off the last barrel roll at 300 knots & setting for a hot landing on the Kootenai.... joystick white knuckled in that cockpit of my ten-G aerobatic low-wing...
my mind would wander to a full gale
of Bora Bora....
No....no .... I disagree ......
For sailing? Is flight. And flying? Is sailing.

When man chooses to play with wind....he chooses
the disparity of consequence and the similarity of the greatest force on earth~

Admiral SeaWolf
Sloop Makari Revenant
Cayo Hueso
***********

[ahp]

My two cents worth: My little plywood pram has a sprit rig, with a boom. The sail is laced to the mast and the sail is loose footed, that is the foot of the sail is secured at the tack and clew but not in between. It sails well, but not as close winded or as fast as a FG Dow with a leg-o-mutton sail.

Some years ago Uffa Fox wrote a book in which he described an interesting class of boat that was around the Isle of Wright, the Redwing class.

This was quite instructive. The a hulls were one-designs, about 28 LOA with fairly long overhangs and wineglass cross section. They were a pretty keel boat that reminded one of the Universal Rule boats.

When it came to the rig, anything was permited, provided that the sail area did not exceed 200 sq. ft. Overlaps were measured and counted fully as area.

Anything and everything was tried. Eventually the rigs gravitated to a Marcony rig with a mainsail having about 70% of the total area and an aspect ratio of about 3 to 1, and a non-overlaping jib.

[Meerkat]

SailBoatDude; I'm not sure I agree with all you've said, but I believe, based on my training and experience, that you're misinformed about sailplanes - a sailplane is always descending, period. It is able to climb by virtue of finding and staying in air that is rising ("lift") faster than it is descending. It gains energy (height) by doing that and gives it back by diving (at the bottom of a dive, a good sailplane driver does not level off, he/she climbs to recover energy (height) at the expense of forward speed until he/she is once more at the desired speed for the conditions - in lift or sink). One flies from one pocket of lift to the next through areas of descending air ("sink"). Sailplanes never "develop thrust" as you put it. They, like I think sailboats do, manage energy in such a way to accomplish their goals without generating it themselves.

I wonder if those "aircraft numbers" you refer to are not Reynolds Numbers? If so, it's been shown that they do apply across all speeds with respect to air or water foils. I've a dim recollection that there are some factors that play a larger or lessor role at various speeds, but Reynolds Numbers predict, fairly accurately, the performance of a particular foil. (And that pretty much exhausts my educated layman's knowledge of them ;) .)

[Todd Bradshaw]

This also gets interesting when you think in terms of iceboats or Aussie 18' skiffs which use wind power so effiently that they sail faster than the wind and are essentially in upwind sailing mode even when sailing downwind. I think my brain is too stuffed to comtemplate all the data. I like lugsails because I find that they have a pleasing shape and with so few strings I can concentrate on enjoying myself rather than wondering if I should add another half-inch of vang.
AHP, I suppose the choice of a simple Marconi sloop makes sense for the Redwing, especially in varying conditions. The Star, for example, has a similar sailplan and gizmos which allow it to be adjusted dramatically to suit the conditions, something which is far less feasable on a lug.

[Meerkat]

You bring up a good point Todd. There are rigs and then there are rigs. While I like the rigs I like, I don't want all those fiddly gadgets alike cunninghams, vangs (except as a preventer) and zippers! All those do get in the way of sailing if all you're really interested in is sailing for relaxation.

[Bill Perkins]

Speaking again of smaller boats : when you need to maximize DMG in restricted waters you drop the rig and row . If the breeze drops very light you'll also maximize VMG under oars ,if the hulls modeled to row well , but such boats won't stand up to a tall rig without acrobatics when single handing ..As said before ,it's all a matter of compromises chosen . I like small boats that sail well , but that you also can look forward to rowing when needed . I have a well made boomed spritsail (from Dabbler Sails )and I'm never disappointed by my boats ability to sail to windward .

[Banjo]

Oh goody Gliders! My fave subject smile.gif

All aircraft from biggest to smallest, powered or unpowered, manned or remote, er you get me? smile.gif follow the same laws. It's That thing called gravity. What goes up must come down. The difference is how long it takes to come back down.
In the case of aircarft wings and foil shapes there are just as many variables as sails on boats.
For sailpalnes or 'gliders' the common factor listed in all their specs is the "Glide Ratio" usualy stated something like 1:16, this means at a specified airspeed the glider will move forward 16 meters and descend 1 meter. All foil shapes have an optimum air flow rate, some are able to be effective over a large range while some with very high cambers need to be maintained in a small speed range for optimum lift.
Sailboatdude, I think you meant to say 'Lift' rather than 'Thrust' as Meer pointed out.

So as an analogy, which would have the better glide ratio, a short deep cord delta wing shape or a long slender wing with higer camber cord?

Thats an ambiguos question because I didn't specify at what air speed smile.gif The delta wing would require a higher air speed to maintain a shallow glide ratio, while the long winged sail plane would maintain the same glide ratio at a much slower air speed.

But in respect to compairing wings to sails, it has been proven in wind tunnel tests that the longer the leading edge the better it will perform 'at a given air speed'. For a sails ability to point, the longer the mast thus the leading edge of the sail the better it will 'lift'. This would be fine if we always sailed upwind, right? smile.gif but we don't.

If you have a tall skinny rig you need to fly a chute to stay in the race downwind, but if you had a ballanced lug, you might drop back little upwind, but on the downwing leg you make up ground and still have only one sail on the stick.

I'm starting to ramble on so I'll stop here, there are too many variables smile.gif
Merry Christmas, I hope the New Year brings good things to you all.

Banjo

[Meerkat]

Would this be considered a Solent Rig?
http://www.selway-fisher.com/Beaump1.jpg
http://www.selway-fisher.com/Beaump3.jpg

[Aramas]

hey! If we want everyone to get really confused, let's start a discussion on water ballast in gliders! lol! tongue.gif

[Banjo]

Originally posted by Aramas:
hey! If we want everyone to get really confused, let's start a discussion on water ballast in gliders! lol! tongue.gif ROFL That just topped off a great year! :D :D

What gets me confused are sayings that make no sense like this one.........
We all know that winners never quit, right?
And that quitters will never win, right?

Then who was the d---k head who started the saying "You'd better quit while your ahead" ?? :rolleyes:

Hehe have a great Christmas Aramas! smile.gif .
Banjo ...out.

[ 12-23-2003, 02:07 AM: Message edited by: Banjo ]

[John E Hardiman]

I was wondering when everyone would see the light.

You all know of course, now that you've finally worked yourselves around to it and embraced it fully, that the glider-sailboat analogy is correct. The both are designed to optimize movement in a direction perpendicular to the applied force, similar to the motion of a watermellon seed squeezed between the fingers. And because of this you can see that there is no such thing as 'lift', only drag generating motion in the direction that you want to go.

The wing of a glider has the same function as the keel of a sailboat or the runners on an iceboat. They only function to make the differential between "ahead" drag and "sidle" drag as large as possible.

Gravity on a glider is the same type of force as drag on the sail. It pushes the "hull" in one direction only. The "wing", "hull" and/or "keel" then resists this force with its own drag. The vector sum of these two forces creates an imbalance in the forces and motion begins in that direction. This motion begins flow over the "wing/hull/keel" which generates a friction drag force to restore the force balance. For any given force balance there is only one ratio of "ahead" velocity to "sidle" velocity of the "wing/hull/keel" that causes everything to balance, i.e. one specific Angle of Attack (AOA). In practice a glider controls AOA of the wing by pitch (i.e. changes the drag of the wing against a constant gravity), a sailboat controls AOA of the keel by trimming the sails (i.e. changes the force of the sails against a "constant" side drag on the keel.

Glide slope has the same relation to gravity as leeway angle to total drag on the sail.

Climb rate is the same as VMG. However, because a glider must always work against gravity to increase its potential energy, it cannot "work to weather" without an energy input. A sailboat does not change its potential energy as it moves about on the flat sea surface, and therefor can work to weather as long a there is wind and force balance can be maintained. A thermal's relation to gravity is the same as current against the wind, the "wing/hull/keel" just goes with the flow.

Pointing a glider straight down is the same as running DDW. They both go fastest this way.

A glider is limited by skin friction and sonic compression, a sailboat by skin friction and sonic compression (which is all wave making is anyway).

The only difference between a sailboat and and glider is that gravity is a lot more constant than the wind. But then again, gravity only "blows" in one direction (around here anyway). :D

Now as you can see, sails are unimportant except to generate lee force. Rig shape has little to do with the generation of this drag. The important thing is to minimize drag in the direction of travel (effectively attempting to climb the glider) or even getting a little thrust in the "ahead" direction (effectively putting the glider in a dive).

[brian.cunningham]

Originally posted by Bruce Taylor:
Meer, a solent rig is like a standing lug w/ the yard peaked extremely high (almost vertical). Solent is to lug as gunter to gaff, if you will. smile.gif Bolger uses it on Black Skimmer, these days. The mainsail on this one looks, at first glance, like a sprit-boomed leg o' mutton, but if you look closely you can see the yard.

http://www.ace.net.au/schooner/cabs4.jpgThat's just way :cool: looking rig! smile.gif

[Howard Sharp]

In defence of lugs... Willow, my (Oughtred) Ptarmigan has a boomless lug, and quite frankly when I first sailed the boat I had no idea why it had a lug rig, but after 8 years I've come to appreciate it as near perfect for the size and type. People can sit where needed to trim the boat without fear of being hit by the boom (the same reason, I believe, that boomless lugs were used in work boats). With the spar on top the sail comes down fast when needed. Without a boom I was interested to learn where most of the thrust from a sail is delivered - even on a small boat I found I needed a two part purchase to be able to hold the mainsheet comfortably. I never looked for this boat to be fast, and a Mirror dinghy will beat it to windward, but reaching or running the lug is powerful, and Willow is quicker. At the end of the day, the rig with no stays comes down in a couple of minutes. And Willow is complemented on her looks wherever she goes

[brian.cunningham]

Have you got the lastest WB issue in the mail yet?

Great article on a lugger that's right up this threads alley! smile.gif

[Meerkat]

Very good post John - Thanks!

I have this notion (inspired by your post) that a glider and a sailboat are more similar than different. They both have two "wings", only the sailboat's "under" wing is shaped to conform to the (relatively) hypersonic conditions it works in. I suspect a good design (should) effectively makes them a balanced pair (?).

Doesn't a rudder change the AOA of the keel?

[Frank E. Price]

Horses for courses is the message, isn't it? If you put a rig in a rowing boat it doesn't need any windward ability at all since rowing to windward is faster in a real rowboat.

And as a cruiser I am less interested in VMG to weather than in a boat's weatherliness: it's ability to continue making something good to weather in conditions that would stop all windward progress in a lesser vessel, even a vessel faster or closer to windward in normal weather. VMG comes next.

My Nutshell pram has one sail, a standing lug, and I think it's the "best" rig for the boat. My cutter rigged motorsailer has the "best" rig, because there's no place to put a mizzen. But if I could afford it, I'd rather have a pinky schooner, and windward ability has nothing to do with it.

By the way, the reference to Maurice Griffiths in my 20 December post should have been Uffa Fox, and the bit about jibs with no overlap should have been not more than a little overlap.

Frank

P.S. Sloop rigs are great, but pity the people who know nothing else.

[Lucky Luke]

Originally posted by John E Hardiman:

gravity is a lot more constant than the wind. But then again, gravity only "blows" in one direction (around here anyway). I still have to recover from the hangover...but I really remember that it was not like that last night! :D

[John E Hardiman]

Originally posted by Meerkat:
only the sailboat's "under" wing is shaped to conform to the (relatively) hypersonic conditions it works in. I suspect a good design (should) effectively makes them a balanced pair (?).A sailboat in water is not really hypersonic (though the speed of sound in water is greater than in air), but water is much denser than air and incompressable therefor requireing a much smaller and different shaped planform to balance the sail forces.


Doesn't a rudder change the AOA of the keel?No. The AOA of a keel is determined by the ratio between the "ahead" velocity through the water and the "sidle" velocity (leeway). The rudder should only serve to provide a short term force to point the vessel in the direction you want to go when changing course or when knocked off course by a seaway (and of course provide positive directional stability indices when centered). Having to hold a rudder a some angle off center to go in a straight line is an indication that the rig/keel balance is out of whack and needs to be corrected. That said, historically boats with tillers/tiller bars have been trimed so that there is a slight weather helm (the elusive 'lead' or difference between the CE of the rig and the CE of the keel). This is to give some "feel" to the tiller and to cause the vessel to round up (thereby relieving the force on the rig) in a gust. This is more a man/machine interface than a true need of the rig/keel interaction.