Slab reefing for a standing lug rig

[Aramas]

I've been looking at old sailplans for canoe yawls like Holmes' 'Cassy' and 'Ethel' (standing lug yawl) and also Nigel Irens and Ed Burnett's 'Romily' and 'Roxanne'.

I've never used a standing lug rig, and doing a search of previous posts here and on the YBW forum turns up that a) They're only suited to 'small' boats, and b) That they're not terribly amenable to reefing.

I really like the sail shape that Nigel and Ed managed with 'Romily' and 'Roxanne', and I suspect that the high aspect ratio version of the old canoe yawl rigs is a worthy direction to pursue. However, I'm thinking about how (in)effective single-line slab reefing would be, and my brain hurts.

Ideally, I'd like the convenience of a junk rig with the sail shape of a standing lug rig. 'Fat chance' comes to mind for some reason smile.gif Imo the main drawbacks of a junk rig are heaviness, 'unfortunate' geometric outline and complete lack of shape - or more specifically, flat in light air and camber increasing with wind speed - the opposite of ideal.

I've considered using heavy but relatively floppy battens (and I wouldn't leave home without lazyjacks) but they still wouldn't fall neatly like a junk because they're not attached to the mast. I imagine that the main problems would be high loading in the reefing line and a tendency to pull the sailcloth into the reefing grommets.

So has anyone used single line slab reefing with a largish standing lug rig? Anyone have any suggestions or recommend any books?

[Ian McColgin]

If it's a really small boat, the sail you have when reefed may be so smally that you can't even reach, much less go to weather, and you'll want to strike the rig alltogether. Or maybe strike the main and plop the mizzen into the main step. In a wee boat, reefing is more trouble than just paddeling.

I've seen perfectly good reefing on a large chinese lug rig - a Colvin schooner. Real slab reefing depends on clew and tack tension, which are not possible on a rig where the luff is not attached to a spar. So all that happens is that the reef points are just above the battens and that works fine. You'll want clew and tack patches. In chinese style lugs, there's a line along each batten pocket that ends just abaft the mast when the sail is set and runs horizontally forward to wherever the mast will be when the sail is struck. This keeps the sail near enough to the mast.

If you've no battens, just add a patch at the reefing clews and tacks and use the reef points simply to secure the bunt but not around the boom.

In either event, you'll need to adjust the euphroe for each reef.

G'luck

[ 12-16-2003, 07:32 AM: Message edited by: Ian McColgin ]

[Todd Bradshaw]

Also keep in mind that reefing a standing lug can be different from most rigs (like balanced Chinese lugs) in that when you put in a reef, moving the tack up the luff, the sail, yard and boom tend to rotate a bit, and sometimes a good bit. The peak angle increases and the aft end of the boom lifts. As they do, the mainsail C.E. (and for that matter, the combined C.E.) will tend to wander a bit. On a fairly high-aspect standing lug main you can probably get at least one reef in without drastic changes, but it's something which should be kept track of closely when designing the rig and laying out the reefs, some of which may need to be put at unusual angles to keep the boom down in the boat and not pointing off into space. You also want to be sure that your sailmaker has carefully thought out and drawn-out the reef planning and that you are both on the same page. If he simply tosses-in a couple fairly standard reef slabs without taking this sail/yard/boom rotation into consideration, you may both get quite a surprise when you put in a big reef. You can see some of this rotation and mainsail C.E. movement on these drawings.
http://www.imagestation.com/picture/sraid93/p6bebaf1b4ad925623519d1709e0a3f3c/fa48543e.jpg

http://www.imagestation.com/picture/sraid93/p4188216ee067f1bb5c57060e2ee5696b/fa48540e.jpg

http://www.imagestation.com/picture/sraid93/p5581b3543fd28eaf589eb575cdd94d25/fa4853ec.jpg

http://www.imagestation.com/picture/sraid93/pc7197de783d75bc6710eb13b925f6bb7/fa4853cb.jpg

[Aramas]

Ack! I mean balanced lug rigs - like Holmes' Cassy and Ethel, and Irens' Romily and Roxanne - the one like a junk without battens.

I always get them arse about. How embarrassing smile.gif

[Todd Bradshaw]

Actually, I've seen photos of Romilly (and/or Roxanne, not sure which) with both standing and balanced lugs. The balanced lug would probably make designing the reefing system easier. I kind of like the looks of this one and reefing would seem pretty straight-forward.
http://www.byd.btinternet.co.uk/ROM-SP.jpg

[AndyFarquhar]

Jim Michalak has a useful article on jiffy reefing a small balanced lug. I use it on my sailing canoe. It's here: http://marina.fortunecity.com/breakwater/274/2000/0615/index.htm#BALANCED%20LUG%20JIFFY%20REEF

Regards

Andy

[MAGIC's Craig]

Todd has nicely illustrated the area changes likely to be encountered as you reef the sail. It occurs to me that the slab reefing you are contemplating would not be all that different than that required for a boomless sail, though I have no experience with the single line set-up you mentioned.

Aboard MAGIC, our 395 sq.ft. boomless gaff fores'l has two sets of reef points in it and we worked out a method to haul the working clew up to the reefed clew, using the "lazy" sheet and a smaller line kept rove between the clews. Tensioning the lazy sheet while slightly easing out the working fores'l sheet cups the clew slightly to windward. Once the sail is lowered to the new reefed position, the working sheet can be re-tied through both clews, tensioned, and the lazy sheet eased away to be similarly tied.

Not as quick as a simple slab reef, but not all that bad once you get the steps of the dance down correctly. ;)
http://www.imagestation.com/picture/sraid13/p2d93f7a3f120ff16258a093e9012b318/fdd7b8be.jpg

[Aramas]

Todd - I've been looking at balanced lugs and I have a few questions.

Just to get started, I've been wondering about how high to peak up the yard, and also whether to lengthen it so that the bit behind the mast is the same length as the boom when the sail's furled. The Irens boats (such as romily) seem to go for very high peak which I presume is to make the yard more of an effective leading edge - is that right? Is it better to have a higher peak and less area?

How does lengthening the top of the yard effect twist? More yard more twist?

Is there an advantage in bulding the parrels for the boom and yard with 'spacers' to keep the sail off the mast?

Since the boom doesn't kick up when the sheets are slackened, would they generally need to be angled up more than other rigs to avoid dragging in the water when heeled?

That'll do for starters - What do you consider to be the critical design areas in terms of performance and ease of handling?

Oh and Craig - I hope that process is a lot easier than it sounds smile.gif

[ 12-18-2003, 09:26 AM: Message edited by: Aramas ]

[Venchka]

While we wait for Todd, here are some more sail plans to help the head scratching and pondering:

Trailer Sailer 24

http://www.cmdboats.com/images/trailersailer24_sailplan.jpg

Caledonia yawl forespars & foresail dimensions:

Foremast 16'-9"
Foresail Boom 11'-4"
Foresail Yard 13'-4"
Downhaul attachment on boom 1'-6" aft of forward end
Halyard attachment on yard 5'-4" aft of forward end

Foresail luff 8'-4"
Foresail head 12'-10" with about 2"-3" of head round
Foresail leech 18'-2"
Foresail foot 10'-9" with about 3"-4" of foot round
Foresail diagonal 12'-11"
Total 131 sq. ft.

Have fun! :D

[MAGIC's Craig]

Oh, Si:

It sounds worse than it is...sorta ;)

[Ed Burnett]

Aramas,

Just a note or two on your comments above....

You mention adjusting the length of the yard such that the portion aft of the mast is the same as that of the boom. With Rox and Rom, we don't use a fixed ring type parrel and have a system where the end of the halyard serves as the yard parrel. The upshot of this is that as the sail comes down the parrel slackens and you can move the yard fore an aft to stow as you like. The key to making this work is a light line from the forward end of the yard that passes around the mast. In effect, this serves as a hinge about which the yard pivots during the first stages of hoisting and the last stage of lowering.

With the short boom on the Strip plank version of Romilly (The glass Rom, like Rox, has no boom), having the end of the spar hit the water has never been a problem. The boom end does lift as you ease the sheet and you can adjust the tendency of the sail to twist by moving the position of the downhaul on the boom. With your boat, if you set the boom at a nice looking angle to start with I am sure you will be fine.

[Todd Bradshaw]

In general, if we have "x" amount of square feet of area in a sail and we stick it on a hull which is fairly easily driven (rather than trying to push a box into a chop) The most helpful portion of that sail area in terms of boat-speed and pointing ability is the leading edge. Higher aspect sails maximize leading edge and at the same time tend to "leak" less. This means that less of their power-producing area is concentrated on the top and bottom where air can sneak over the ends and get away without pushing the boat. So yes, a higher peak on a lug is usually a better bet on a good hull.

Twist on a four-sided sail is often more a function of chord width near the top than anything else. The sail naturally wants to twist, which is generally fine to an extent, since the wind up there is also twisted a bit. The weight of the yard, influenced by the heeling hull is also a powerful twist-producer. A higher-peaked, somewhat narrower head is going to be less prone to twisting excessively than a low-peaked wider-headed sail since the yard and more of the sail's upper area are closer to the mast that they are rotating around (less leverage).

The drawbacks to lengthening the yard are increased weight aloft and in many cases increased yard bend, which can make getting a good sailshape for varying conditions difficult. A skinnier, lighter yard yields less weight aloft (which is good, and which may twist less) but one which bends more (which is bad when you are trying to cut a sail that will work as well in 20 knots of wind as it does in 5 knots). A sturdy, stiff yard that bends less will be easier to cut a good sail for (which is good) but will increase weight aloft and probably twist (which is bad).

On lugsails you also always need to be aware of the (for lack of a better term) "rigging forces". There is a rotational thing going on: The mainsheet pulls down on the tail of the boom, which pulls down on the leech, which pulls down on the aft end of the yard, which pivots on the halyard, pulling up on the forward end (heel) of the yard, which pulls up on the sail's luff creating proper luff tension against the forward end of the boom, which is prevented from lifting by the fixed downhaul and/or parrel or jaws on the boom at the mast/boom junction.

But what if the mainsheet is eased or not pulling down on the boom at the moment? In that case, it is the weight of the yard, pivoting on it's halyard and projecting aft of the masthead (along with the weight of the boom's aft section) that keep the sail from collapsing and the yard from trying to "dip" itself.

What I'm getting at with all this mumbo-jumbo, is that there is a point on any lugsail where too steep an angle on the yard ceases to do it's part of the rotation thing and the whole configuration becomes unstable any time the mainsheet is eased. Instead, it wobbles or tries to dip or rotate to vertical and the luff tension is lost. I don't know whether anyone has ever scientifically tried to figure out just where that point is, but I don't think I'd go much steeper that the yard angles of boats like Romilly or the Caledonia Yawl which have proven to work well and also are very good looking.

There are people who have spaced-out the parrels and even the downhaul systems so that the sail doesn't touch the mast on either tack and who claim it works. On a boat this size though, sail handling might be easier with the yard and boom kept close and I'm not sure it will make much real difference in efficiency or boat-speed. Likewise, from what I can tell, much of the dreaded "hindered tack syndrome" where the sail is flying free on one tack and disrupted by being plastered up against the mast on the other isn't much to get alarmed about. I have yet to sail a boat that sails great on one tack and poorly on the other for that reason.

I do think full battens in a western-style (cambered) balanced lug may create some tricky problems. If they get forced against the mast on one tack you can wind-up with pretty strange sailshape half the time you're sailing. It kind of depends on how much of your balanced lug is actually in front of the mast, which in many of these boats isn't much. The Chinese lugs are cut flat and their heavy battens pretty much stay that way, even though the mast is farther back. Look at the battens on that schooner that TimothyB posted in the other thread and how little they're flexing. They're much of the reason for the increased weight aloft on Junk rigs, but most of their owners claim that the entire sail is so stable and user-friendly that it's worth the extra weight. On a western balanced lug, I lean toward no battens and if their primary function is to aid in reefing, I'd do my best to figure out a different system and ditch them.

As Ed said, I don't think you'll need to make any kind of drastic change in boom angle to keep it out of the water. Reef lines are normally raised a bit on their aft ends anyway for that reason, so you should have more clearance when it's blowing and you're reefed down. The raked masts on these boats also help a lot, since the boom's aft end lifts naturally as the sail swings out over the water.

[Aramas]

Thanks guys - lots of food for thought in there.

Ed - Romily is an interesting comparison with my design since she's about the same length but half the designed maximum displacement. She looks like she'd go like the wind with the high aspect ratio rig and foil. I bet she surprises a few 'conventional' boats.

I'm having trouble visualising the yard parrel you're describing - do you mean that there's a line from the front of the yard that goes around the mast and joins the halyard close to where it attaches to the yard? Kind of like on junks but it's tensioned by the halyard?

I've looked at the pictures of Romily on your site, and it looks like the halyard goes from the yard, through a block at the top of the mast, back down to a block near where it started, then around the mast and through another block further along the yard.

Todd - I actually managed to follow that smile.gif I'm sort of thinking along the lines of having 2 separate lines for each reef that will replace the outhauls when reefed (so 6 lines for 3 reefs), and since the whole arrangement is off-centre I can't see any way of leading the lines off the rig without tension changes as the rig rotates. So I guess that leaves all the reefing gear (including a small winch) on the boom. Then of course there's what to do with the ends of the reefing lines - boombags perhaps? Sounds messy anyway smile.gif

I've been looking at the fruity reefing arrangements that Baden-Powel drew in Kemp's book, and I can't help but wonder if he had shares in a rope company. I don't think there's much I can use in there.

It's rather disappointing that development of alternative rigs more or less ceased when the bermudan rig became widely adopted as the 'international standard'. It would be hard enough to find a sailmaker that didn't laugh on seeing a lug sailplan, let alone finding one that can turn out some fine sailmaker's art for such a rig.

[ 12-19-2003, 09:43 PM: Message edited by: Aramas ]

[Ed Burnett]

Aramas,

O.k, I'll try to describe this parrel system, although I ought to just post a picture....

The starting point is a three part purchase for the halyard, ie. double block at the masthead. Normally, one would put a single and becket on the yard and that would give you the purchase, however, rather than a single and becket, we place two singles on the yard at the usual place (+/- 1/3 of the yard length from the forward end). The end of the halyard that would normally be made fast to the becket, passes through the second single block, goes around the mast and is made fast to the yard. Thus, tension in the halyard holds the yard in against the mast.

There are complications....

As described, tension in the halyard would mash the yard against the mast to the detriment of both, so, you need to tie a stopper knot in the halyard to come up against the single block such that it tightens only so far. You also need some parrell beads on the halyard between the stopper knot and the end of the halyard where it is made fast to the yard.

As I mentined previously, there is another key piece of line. This goes from the forward end of the yard, around the back of the mast and back to the forward end of the yard. The length of this should be such that it just goes slack when you tension the downhaul. Its job is to stop the yard swinging forward too far, in effect it keeps the yard peaked up as you hoist and lower. This gets around the usual problem with lugs, which is that when you ease the halyard to lower the sail the first thing that happens is the peak of the yard drops down and clonks you on the head.

Another couple of optional bits of string.....

A couple of loose gaskets from the luff of the sail around the mast can be worthwhile. These should go slack when the sail is set, but keep the luff under control when hoisting and lowering.

Remember the line that stopped the forward end of the yard from going too far forward? Now, if rather than tying it off at the end of the yard you put a little block there and run it down to the deck, you have another tweaking tool for sail shape. This does the same thing as the peak halyard on a gaff main, ie. by pulling the forward end of the yard down and aft, it peaks up the other end and moves the draught in the sail forward. It's more gear, and not worth it on little boats, but it's fun. You have to tie a stopper knot before the block so this bit of rope still does its job when hoisting and lowering without being tended.

So much for a simple rig....

As for the reefing, I would suggest you start by having just two reefs, that will save gear and string straight away. With Romilly, all the reefing gear stays on the boom, but you can still reach it standing at the forward end of the cockpit. Single line may be worth the effort, but I doubt it, and trying to get it all down to the deck to run aft would be a nightmare.

Romilly slips along nicely enough, but I wouldn't say she was a rocket ship. At the end of the day she is not a particulary powerful boat and that is one of the main reasons for adopting the lug rig. If I may make a suggestion regarding your new design, it would be that you have a quick look at some weights and centres and work through to some sort of stability index. Dellenbaugh angle is quick and pretty useful, although the chart in Skene's suggests figures for small boats that are a little on the high side. Your sections are pretty round, she isn't deep, and you will need a fair bit of sail to move that displacement. You may well have this in hand, in which case ignore me.

Happy Christmas!....

[Aramas]

Ed - Believe it or not I think I followed that. I hope it sounds messier than it actually is smile.gif At least I know that it's at least feasible. 2 reefs is probably a good idea - I'm starting to appreciate just how much string is involved, but I think I can probably defer worrying about that for a while - as you pointed out I have more immediate concerns.

Gwenda is kinda round - if I had to give her another name it would probably be Baby Fat. I did an early stability run some time ago but there was a certain amount of guesswork in the location of G. Once I get some minor tweaking on the backbone done (which will take ages of course) I'll redo all the internal panels and do a more accurate weight calculation. She's probably not as bad as she looks - she has around a tonne of lead between around -0.50 and -0.55m. If I have to firm the bilges up a bit to carry enough sail then so be it, but I hope it won't be necessary. Compared to some production trailer sailers I've pottered around in she's a rock smile.gif

I'm somewhat dubious about the Dellenbaugh angle and the WPC in Skene's - I have no idea how they're derived. I assume they're empirical? And anything in archaic units makes my head hurt. I'll probably run them anyway (that's what I did last time), but I thought I'd just work out the wind pressure normal to the sail (taken as a force acting at the centroid) at 10 knots and 30 degrees, then just keep modifying the sailplan until the heeling moment is close to the righting moment. I figure that if it heels 30 degrees in a static wind loading condition with the sails sheeted flat then she will probably need reefing around 15 knots or so.

Of course then I have to look at proportioning the 2 sails to keep it balanced when reefed, but I have an idea for doing that with a spreadsheet. It might even work smile.gif

And thanks for the feedback - at college there wasn't a single lecturer who didn't smile condescendingly at the mention of sailing boats, so what I did figure out I had to do by myself. Fortunately the AMC has a good library. I wouldn't have any trouble doing a trim and stabilty booklet or DNV scantlings for a bulk carrier, but funky old sailing stuff just wasn't on the program.

Andy - thanks for the link. I got sidetracked and forgot to mention it earlier smile.gif

[ 12-22-2003, 01:46 PM: Message edited by: Aramas ]

[Ed Burnett]

Aramas,

Dellenbaugh angle is no more than the ratio of heeling moment (using 1 lb per sq.ft. wind pressure) to righting moment (at 1 deg.). The number you get out is just a number - some refer to it as some sort of heel angle, but that takes it a little far I think.

If you want metric...

Dellenbaugh angle = 274 (As * HA) /(m * GMt)

Where: As = sail area (m^2), HA = heeling arm (m - generally taken to 1/3 draught), m = vessel mass (kg), GMt (m). 274 is the fiddle factor to give you the same number that you would get with the imperial units.

It is an almost entirely empirical thing and useful only as a means of comparison with other boats, but then again this is what makes it worthwhile. You can take a purely theoretical approach and do sums till the cows come home, but if you don't lift your head from the calculator now and again and take a look around you risk finding yourself out on a limb in design terms.

Have fun....

[Aramas]

Ed - Having a bad day? Christmas shopping can drive you nuts if you leave it too late, and I must confess the prospect of not spending christmas with my family for the first time in several years leaves me feeling strangely relaxed smile.gif

What I find irritating about the WPC and Dellenbaugh angle methods is that they're of the paper design era and as far as I can tell they don't take into consideration free trimming to the designed displacement when heeled. Whether a boat rolls up or down when heeled isn't compensated for, and consequently the displacement might be much more or less than it should be if worked out according to Skene's - which makes comparisons somewhat suspect imho. Still, if it works it works, and I realise that's the convention and the trim and stabilty documentation for ships is usually done that way, but the 'real' stability is also done - and I know which one I pay attention too. I would be uninclined to describe trying to develop a deeper understanding of a system as taking "a purely theoretical approach and do sums till the cows come home, but if you don't lift your head from the calculator now and again and take a look around you risk finding yourself out on a limb in design terms.", but hey - what do I know? smile.gif

Sure I'll use the old methods, but I'll also play around and see how the actual physics of it work out. If it falls in an acceptable range using the Dellenbaugh angle and it's balanced according to simple statics then where's the harm? When I do the spars I'll use FEM, but I'll also check to see that they meet whatever rules of thumb I can find. I find both the process and the product to be more satisfying if done that way.

I'm not trying to sell anything to anyone, nor am I trying to convince anyone that I know better than professional designers. Gwenda is a personal project of mine and is being done entirely for my own benefit and experience, and I'm sure I'll learn a lot as she develops. I'm much more interested in the art than the number crunching, which I find tedious and menial, somewhat like cleaning up afterwards. Still, someone has to do it and I don't see any volunteers leaping out of the woodwork smile.gif

[ 12-23-2003, 10:03 AM: Message edited by: Aramas ]

[Ed Burnett]

Well, I thought I was having a pretty nice day really!

It was not my intention to question your judgement, and please forgive me if I gave that impression. I was just trying to be helpful by giving you the metric version of what I find to be a pretty useful little formula in its own, albeit limited way.

I don't think anyone would claim Dellenbaugh Angle to be the be all and end all of stability indices, although to be honest, I don't quite see the relavance of your argument for doubting it's applicability. Like all these things, if you take it for what it is and know its limitations it can give you a valuable comparison with boats that you know work, and also those that you know to be less than perfect. That's the "take a look around" bit that is in my view one of the most important aspects of designing in what is, after all, a pretty well trodden area.

Anyway, it sounds like you have it all in hand so I'll leave you to get on with it in peace. Have a good Christmas.

[Aramas]

lol - the joys of sleep deprivation smile.gif

I was reading an article recently about how creativity emanates from the same area of the human brain as insanity, and that if inspiration is pursued unchecked then one can become detached from reality. Still, when the creative juices are flowing then one must milk them for all their worth. tongue.gif

So I apologise in advance for any behavioural peculiarities while I'm doing all-nighters :rolleyes:

I hope everyone enjoys the holidays.