Yawing at Anchor, The Theory and The Solution

Back in 1987, Hurricane Emily hit Bermuda with wind gusts in excess of 100 knots. What made this unique, at least in modern times, was that due to the unprecedented and unpredicted speed the storm was traveling as it approached and crossed Bermuda, we had almost no notice of the impending hit.

When I went to sleep, along with the rest of the Island's residents, Emily had been a slowly dissipating hurricane well south of Bermuda, and no threat.

My phone went off at 04:00. It was my then brother-in-law who, at the time, looked after American billionaire Ross Perot's boat:

John, get your boat off the dock, Emily is coming to breakfast.

After a mad scramble to secure the house, I headed for the boat through the eerie early morning flat calm darkness. There was not a breath of wind when I left the dock bound for our hurricane mooring. Thirty minutes later, as I approached the mooring, it was already blowing a full gale, and by the time I got secured (on the third pickup attempt), it was clear that I was staying aboard for the duration.

The good news was that, due to Emily's speed of advance, the storm only lasted about three hours, with a short lull in the middle as the eye passed over.

I spent that time standing looking out the companionway, not that there was a lot to see. When it's blowing that hard the point where the sea ends and the air begins gets blurred with blowing spray.

Still, I learned three things that day:

  1. Introduction
  2. 4 Vital Anchor Selection Criteria and a Review of SPADE
  3. SARCA Excel Anchor—A Real World Test
  4. SPADE, SARCA Excel, or Some Other Anchor?
  5. Rocna Resetting Failures and evaluation of Vulcan and Mantus
  6. Some Thoughts On The Ultra Anchor, Roll Bars and Swivels
  7. Specifying Primary Anchor Size
  8. Kedge (Secondary Anchor)—Recommended Type and Size
  9. Third Anchors, Storm Anchors and Spare Anchors
  10. Anchor Tests—The Good, The Bad, and The Downright Silly
  11. Making Anchor Tests More Meaningful
  12. We Love The Way Our Anchor Drags 
  13. Things to Know About Anchor Chain
  14. Selecting a Chain Grade
  15. Anchor Chain Catenary, When it Matters and When it Doesn’t
  16. Anchoring—Snubbers
  17. Anchor Rode Questions and Answers
  18. Q&A: Hybrid Rope And Chain Anchor Rodes
  19. Anchor Swivels, Just Say No
  20. A Windlass That Makes The Grade
  21. The Perfect Anchor Roller
  22. Install A Wash-down Pump—And Save Money!
  23. Anchoring—Kellets
  24. Anchoring—Chain: Stoppers, Termination and Marking
  25. 20 Tips To Get Anchored and Stay Anchored
  26. Choosing an Anchorage
  27. Choosing a Spot
  28. 15 Steps To Getting Securely Anchored
  29. One Anchor or Two?
  30. Two Anchors Done Right
  31. It’s Often Better to Anchor Than Pick Up a Mooring
  32. Yawing at Anchor, The Theory and The Solution
  33. Yawing at The Anchor, an Alternative Cure
  34. How To Use An Anchor Trip Line
  35. ShoreFasts—Part 1, When to Use Them
  36. ShoreFasts—Part 2, Example Setups Plus Tips and Tricks
  37. ShoreFasts—Part 3, The Gear
  38. Gale And Storm Preparation, At Anchor Or On A Mooring
  39. Storm Preparation, All Chain On Deck
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Taras Kalapun

Hi John,
Very nice info!
Few times in Meds, during hard blow, I used full length of chain and tie the stern of the boat to the shore. In Meds, where space is premium, I had no other option. But it also reduced surging.
I would like to know more about your Dyneema shorefast setup. What kind of line do you use? Pure dyneema or covered? How do you attach it?
Thank you!

Martin Levesque

It would be great idea!
Always appreciate your articles !
Best regards,

James Greenwald

Hi John,
Based on the design physics you speak of; if I have this right would anchoring stern to wind help to alleviate if not remove yaw motion? Putting the CLR ahead of the CE?

Jim

James Greenwald

I know I read about this somewhere and will try to locate the data

Andre Langevin

Yes it was document on the oceanbrake web site relating the recommandation of Jordan. However for a pointed stern that is ok but for modern flat ender it is a nightmare to hear the flapping of the wave against the hull !

Matt

In theory, yes.
In practice, modern boats tend to have relatively wide, flat, low transoms, so you’ve replaced yawing & surging with being hammered flat-on by the whole wave at once, with a risk of the wave breaking into an aft cockpit and the rudder being slammed to its stops.
I think the riding sail is probably a better option.

Maxime Gérardin

Wow, your experience with the mooring plus a shorefast is quite extreme!

May I add that if possible, mooring stern-first rather than bow-first is very likely to solve the issue? Of course only to be done if you can protect yourself from short steep waves hitting the bow, which seldom is the case.
(By the way, in my opinion, knowing what amount of short waves hitting the stern your boat can handle is good seamanship, because, when possible, removing all sails and backing with the engine towards the MOB (with tailwind, of course) is, to my knowledge, the best way to rescue a man overboard.)

About furler headsails, a friend was once advised by offshore racer Michel Desjoyaux to avoid unwanted unfurling by wrapping a spinaker halyard around, if removing the sail is not a possibility. I personally have never tried.

Colin’s solution seems briliant. With the existence of that plus riding sails, there’s no excuse for being caught in the trap!

If the engine was to be used, only reverse could help! But that would be a last resort thing, and as I just wrote, there’s no excuse for being forced there.

Stein Varjord

Hi Maxime,
The advice from the amazing sailor Michel Desjoyeux, nickname «Le Professeur», about wrapping a spinnaker halyard around a furling head sail is a good one for two reasons. Firstly, it prevents the sail from unfurling, of course. (Removing the sail is obviously better.)

Additionally, and this is also valid for an empty head foil, it much reduces the tendency for the whole stay to vibrate, which causes wear on end terminals etc. The reason for this is that it creates a horizontally asymmetric shape to prevent that the wind builds an oscillating pressure field around it. That’s why many very tall industrial chimneys have a spiral shape on the outside. Without it, they might come down in a blow.

The last 3-4 weeks have been very stormy in Amsterdam. I’ve saved two unfurled sails on other boats from turning into tatters. 4 others have been saved by others in the same period, in a 300 boat harbour, so this is a quite normal thing to happen with furling headsails…. I’ve tried my best to roll up the sail as well as possible, which was not very easy in a blow with a sail having come out in the top more than further down. Then using a halyard to wrap it all up and securing it. Quite easy and effective.

Since both got me out of bed in a hurry around 4 in the morning, in cold heavy rain and wind, I felt that another necessary ingredient was creative colourful linguistics, but it might work also without this. 🙂

On my own boat, the head sail comes off in the winter. Previous years I’ve had a rope pulling sideways, like the genoa sheet would, to stop head foil vibrations. This works OK, but this year I wrapped the spin halyard around it. About 8 wraps I think, on a 22 meter foil, and pulled tight. Has worked perfectly.

Maxime Gérardin

Hi Stein,
many thanks for the very fine piece of advice and explanation! I was totally unaware of the anti-oscillation effect.

Andre Langevin

Hello it is on my plan to buy a FinDelta to stabilize the boat at anchor (double furling headstay has its disadvantage). For those who can read French, Pierre Lang has cruised the Mediteranee for a long time and being an engineer, he had several occasions to think about the problem of boat surging at anchor. He offer on his web site (low cost book) a windage calculator that is very indicative of the forces involved with a boat exposed to wind (frontal + lateral) and he came to the same conclusion, that an anchor sail should be flown at the stern to survive the notorious Sirroco and Meltem in the Greek island.

In his book he demonstrate with calculations the reduction of the angle of oscillation with an anchor sail and the reduction of the forces on the chain.

http://www.thoe.be/2016-mouillage/home-site.php

John Tully

I have just finished a hardtop on our Bristol 45.5 . We are just moving on to the canvas part of the setup . It looks very similar to yours . I am curious about how it will perform at anchor in a blow hopefully stop the surging as yours did .
Regards John
S/V Salserenity
https://www.youtube.com/channel/UCCC0iDST14BzzTGJM3YJSTw

Brent Cameron

I suspect you are right about the effectiveness of a stern arch and the usefulness of a FinDelta. I was crewing on an Amel Super Maramu with a big arch (and an enclosed pilothouse/enclosed bimini) during quite a few big blows in St. George’s Harbour in Bermuda this last fall (some with 45kts+). With the standard Amel pilothouse/fully enclosed Bimini, we wandered all over the anchorage – even though it is well back of the CE – but the moment we unfurled a tiny bit of mizzen (less than a square metre from inside the mizzen mast), the boat snapped to attention and tracked the wind like it was on rails. Moving that CE back made all the difference in the world.

In at least three of those gales, we had wind shifts of 180 degrees over a very short period. During the first one, our very well set Rocna popped out and we dragged as it never reset until we literally hauled it up and did a full reset procedure using the motor to hold our place and give the anchor time to set. The very next morning we put on the brand new Mantus the skipper was planning on using as an emergency anchor and stowed the Rocna. The next two gales with wind shifts every bit as severe (and winds even higher) never budged that Mantus. I got an opportunity a few weeks after that to dive on the anchor in Martinique after such a wind shift and it was obvious that the Mantus turned and buried itself within a length of itself so it made me a real fan. That was the second time I’ve been on a Super Maramu which dragged on a 180 degree shift on a Rocna. I know it is anecdotal but really believe there is a problem with the Rocna in that it really needs time without load to bury its point (which it doesn’t get on a reset caused by a significant wind shift) and I am putting a Mantus on my next boat.

Richard Elder

Great video about surviving a Cat 4 hurricane while hanging to a large Mantus.
The singlehanded skipper did almost everything right.
https://www.youtube.com/watch?v=52vu7bbvqC0

By the way his boat is a very ordinary plastic production boat that he paid $3,000 for. It’s been home to he and his partner for eight years and taken them through the Caribbean,
Canada, and across the North Atlantic.

David Steele

Please comment, if you can, on use of the mizzen as riding sail. Our 20 ton center cockpit cutter/ketch seems to ride better with it partially unfurled, but too little doesn’t seem to have an effect and when enough is deployed to make a difference (@50%) it catches the wind alternately on both sides, so the stern is yawing back and forth instead of the bow!

PS- removed our jib from the furler before the last storm and didn’t seem to make much of a difference so we’ll remove the staysail from its furler, as well as the whisker pole from the mast next time and see what happens. We do have a large hardtop over our center cockpit with 2 large solar panels mounted on it, nice to know it can actually help! Perhaps I need to add wings to it…

Dick Stevenson

Hi David,
I sailed a yawl for years and one of the things I loved about it was that we would anchor, leave the mizzen strapped down tight, and we would be weather-cocked to the wind with no sashaying about at all. When we went to a fully battened mizzen, we further enjoyed a steadying sail that was absolutely quiet. We had deeper reefs put in than was “sailing” necessary to enable using the sail at anchor in storms and high wind. It takes surprising little sail area to keep the boat perfectly pointing to wind.
I have no experience with roller furled sails in a mast, but I suspect that a deeply reefed sail might have too much “belly” not to fill one side to another. I wonder whether a really flat riding sail might be quite effective and easier to rig in the mizzen triangle and leave the mizzen sail rolled up.
Enjoy this aspect of a mizzen.
My best, Dick Stevenson, s/v Alchemy

Marc Dacey

Another reason to love AAC: not only have you employed techniques to solve passagemaking problems, but you’ve thought why they work. I knew about the Fin Delta solution, but we have a signficant solar arch (four panels) over our aft helm, itself aft of our pilothouse. I have no data points as yet of whether this will retard yawing and surging, but I see that the Fin Delta appears to be set up at boom end, presumably hauled on the main halyard with the “delta fins” taken to the stern quarters.

Any thoughts on a flat, heavy riding sail sheeted in tight? I could do that tomorrow, save that I have two backstays going to our stern quarters and thus any flat sail would be angled to the deck of the boat. Conversely, I could do Drew’s solution over the boom and get a sail flat over the boom, perhaps on a wire strop attached to the main halyard and terminated at the deck level.

Very interesting topic few broach. Thanks, John.

Matt

A tight, flat riding sail is likely better than no riding sail at all.
The flat sail doesn’t create any significant drag or lift while the boat is directly head-to-wind. Its drag (directed roughly aft) and lift (directed to starboard, if the boat yaws to starboard) increase with the yaw angle.
The FinDelta shape, by comparison, presents a roughly constant drag force over a large range of angles. Its lift should be zero when head-to-wind, increasing with the yaw angle, but not proportionally – I’d expect a rapid rise in lift with the initial deviation from 0° and then a relatively gradual increase beyond about 5°.
I haven’t calculated this quantitatively, but a few quick sketches suggest that if you size a FinDelta sail and a flat sail to provide the same yaw moment at, say, 20° off the wind, the FinDelta shape should be quicker to develop that yaw moment (i.e. it should arrest the boat’s yaw more aggressively) at low angles.

Marc Dacey

Thanks, Matt. I wasn’t making a case for or against the Fin Delta over a flattened riding sail, but merely that the flattened riding sail might be qualitatively better than no riding sail at all, particularly as I have an existing solar arch (it’s even cambered like a bimini) that may help to dampen wild yawing.

John Tynan

Hi John,
Do you think that hanging a weighted bucket over the bow and under the water would dampen surge movements?

Mike Drummond

A hull at an angle to the wind has opposite transverse forces near the bow and stern which causes the yawing moment.
It is called the Munk Moment and is unstable – more angle = higher moment.

One result from theory is the moment exists with angle alone – the boat doesn’t have to be moving sideways to have the yaw moment. So I don’t think the CLR position matters in initiating yaw and surging.

The riding sail moves the aerodynamic centre aft enough to have a stable aero moment. Probably, there are rules of thumb for the sizing of the riding sail.

Mike Drummond

Hi John,
Yes I was saying the same thing, just pointing out for interest the yaw moment phenomenon.
Reading Colin’s report and looking at the Fin Delta, it seems to me the riding sail is pretty good prevention; and the drogue is an effective cure.

Thanks for your articles, always interesting.
regards
Mike

Stedem Wood

Hi John,

Another vote for the shore-fast article……

Colin Speedie

Hi John
having used the drogue attached to the anchor chain off the bow a few times now I’m more that convinced that it works well, at least for our boat which has a relatively shallow underbody. It really reduces the impact of the worst gusts and so (I believe) lessens the effects on the anchor. It’s also has a calming effect on the nerves, for the same reason.
Riding sails need to be set tight and flat or vee style two sided shapes preferably with some form of pole in between the two clews to keep then set in the correct manner and small – unless you can reef a mizzen with a flattening reef they are too big and flog horribly to the detriment of the sail and civilised existence on board.

Colin Speedie

Hi John
not as many times as you might (and I certainly did) expect. I have experimented with the length of the strop and also the distance that it’s attached from the bow. The strop length can be adjusted by extending the distance from the chain hook, but this seems to have less effect than the need to get the distance from the bow right. In strong conditions it is important that the drogue is around 1 meter below the surface so that (a) it remains immersed and (b) is not so far from the boat that a form of ‘hinge’ develops where the the boat starts to swing more, pivoting on the position of the drogue, which is what the system was conceived to avoid! This isn’t entirely ideal as conditions vary – but for the most part I’m impressed enough to use it when necessary and consider it a worthwhile addition to our arsenal of storm tactics at anchor. For example, we used it in a tight creek in the Bras D’Or a couple of years ago, in very strong and gusty conditions, when without it we would have been at risk of swinging into shallow shelf areas – as it was the drogue helped to limit our swinging radius, which was all we needed to feel relaxed about the situation.

Colin Speedie

Hi John
I should have added that I now use a heavier weight attached to the drogue which seems to have reduced the drogue wrapping on the cable.

Bill Attwood

In the absence of a v-sail would a flat sail sheeted to one quarter work? This might encourage the boat to lie to one “tack “ and stop yawing. Perhaps trysail or spitfire jib set flying on main halyard, with tack strop attached to mainsheet horse?

Colin Speedie

Hi Bill
I don’t know about the other options, but the V sail works (at least on some boats). As explained to me by the veteran commercial yacht skipper I saw using one, it needs to be small, tough and with a pole to keep the clews apart, then hoisted low aft and all set good and tight – it looked amazingly effective.

Dick Stevenson

Hi John,
Although it may not fit the technical definition of a riding sail, the mizzen on my yawl would go up at the beginning of holidays and not come down for weeks at a time. As said before, it was full battened, therefore quiet, and I had deeper reefs than sailing demanded, so it stayed up even in high winds. It made a huge difference: we were always facing directly into the wind and very comfortable: absolutely no slewing about. On the rare occasion that we had waves/swell that did not match the wind, we could pull the mizzen to one side and mitigate rolling. It also made anchoring in our crowded New England anchorages much easier in that I did not have to anticipate our sweeping around and probably kept me out of the fusses that sometimes developed between two boats swooping through 30+ degrees and sometimes getting so close they could pass hors d’oeuvres to one another (more likely annoyed comments about who came first).
I see no reason that well-designed riding sail would not perform similarly: the only difference (possibly significant) might be that my mizzen sail was pretty far aft.
We used a friend’s riding sail (flat and off the backstay) on a Sabre 28 (in late 1970s), a far more skittish boat, and found only a moderate difference and ultimately decided not to get one: too fussy. I also felt that, not having a rigid leading edge, that the flat riding sail would catch the wind and “belly” out in a not great way: not a deal breaker, but I wondered what would happen in high winds. This may be less of an issue now: I am referring to days before high modulus lines and sailcloth: now one can get an almost rigid leading edge.
My best, Dick Stevenson, s/v Alchemy

James Evans

I used a riding sail regularly on my old Boat, a lightweight 1/4-tonner. The sail was the top of an old jib, with plenty of hollow in the (new) luff and foot, hanked to the back stay by the original luff and sheeted forward to the foot of the mast.
It absolutely transformed a boat which was formerly an embarrassment in a crowded anchorage. I particularly remember a night of 55-knot squalls in Marsh Harbour when it sat quietly while I lounged below listening to the mayhem on VHF!
My last boat didn’t have a back stay or I would definitely have made another riding sail; I tried one set on its own halyard but it shredded itself before I had time to sort it out.
Riding sails are brilliant. In my experience they need to be flat but don’t have to be heavy (except for the luff if set on their own halyard).

Eric Klem

Hi John,

Interesting subject.  I will admit that my temptation has long been to try to move the CLR forward as the solution.  However, I don’t know how to do it without moving the rode to the stern, adding a daggerboard to the bow doesn’t seem like the greatest idea nor does finding a way to stick a pole down into the water with a drogue on the end.  I have been on and seen a few boats that were bad enough that I would absolutely think adding a forward daggerboard for use at anchor would be worth it.

You have me once again thinking that maybe I should try a riding sail.  If we didn’t have hank-on sails, I suspect that we would have already been forced to take this step but our boat is adequately behaved tacking through only 60 degrees or so by the time the wind is 30 knots.  I will have to see if I have enough sail material kicking around to make one and do a bit of experimenting (if I really needed it, then I would be purchasing).

The theory on the design of the findelta makes sense.  My only question is whether the single leading edge with effectively zero thickness ever makes an annoying amount of noise as opposite sides of it fill.

Eric

Eric Klem

Hi John,

If I try it, I will certainly report back.  While our boat sails more than I would like, comparatively it is not that bad so not the greatest testing platform.  We have a Hunter (not sure which model but probably early 2000’s) on a mooring near ours and watching it dance around is truly frightening and I can’t imagine sleeping aboard.  I have run a lot of boats with varying behavior at anchor but never something that bad.  Since I would often only be on a boat for a short period of time, my solution then was always an anchor spring but that has its own issues.

I only became aware of the Fin Delta several years ago and prior to that I had always written off riding sails as they looked noisy and ineffective to me.  To me, the Fin Delta has 2 clever features.  First, they figured out how to get it to spread without using a pole.  Second, the design of it is clever enough that the aerodynamics should make it more effective than a simple V shape of the same size.

I haven’t truly given Colin’s method a proper try, I used a bucket once to some success.  I see the 2 methods as trying to attack the problem differently and potentially useful in different situations.  The riding sail is all about trying to align the CE and CLR so that the torque they produce in the yaw direction always restores you to bow facing in to the wind.  The drogue is trying to do 2 things: add another force component that produces a yaw torque and act as a damper.  At the first, it is imperfect as the angle of the force means that not very much of it goes to torque but still more than a rode without the drogue.  As a damper, it is definitely useful in conditions where the snubber is not yet stretching a lot and the chain still has some catenary but if the chain is not moving a lot, a drogue won’t add much.

Having never really tested either, my inclination is to first try to solve the CE + CLR relation problem.  Then, if there is still a dynamic problem because you are anchored at the base of a mountain with alternating gusts or something, I think that the drogue could really help with the dynamics.  It isn’t that the drogue won’t help in constant conditions, it certainly will but it requires the boat to be sailing back and forth some to be able to apply its restoring force.

Eric

Colin Speedie

Hi Eric
Totally agree – you’re quite right. For what it’s worth we adopted that method partly because setting up a V sail on an Ovni with the arch etc seems to be too much like hard work – we might well have gone down that route if it had been simpler.

Marvin Hamm

I think I can mentally imagine your Nail the Bow idea, but a graphic would really help.

Ernest E Vogelsinger

I tried to create a sketch of how I understood Johns instructions – @John, is this somehow like you did it?
https://imgur.com/gallery/wIY15tX

Philippe Candelier

The feathers at the aft of the arrow are not decorative. Their reason for being there is for the exact same principle: move the CE backward. It basically allow the arrow to travel straight.
Adding a riding sail or anything that put lift at the aft makes perfect sense to me.

Drew Frye

Fun stuff.

As for nomenclature, the title threw me off. Surging is fore-aft movement, whereas we have been talking about yawing (rotation on the z-axis), although they certainly combine. Boats can surge-only using rope rode, which stretches.

It’s all about balance. One of the most common offenders I see, as John pointed out, is a tender on the bow. It’s like a riding sail at the wrong end.

The few dragging episodes I have experienced were all early in my sailing career, and they were all the result of excessive yawing. I can’t sleep if the boat is yawing more than 30 degrees or so. Just think of how it is wiggling the anchor.

Regarding riding sails, testing convinced me that V-sails are certainly more effective than flat sails, but like sails, the best choice may come down to what sets well on your boat. A low boom and plentiful beam favors a V-sail rigged over the boom. It is VERY strong, very well supported, and easy to rig, which are all good things. If you have a high boom, a hard top or big bimini a Fin Delta may be more practical.

The other common misbehavior is hobby horsing. It can be a factor if the boat is at short scope and the waves match the period of the boat. Probably the only thing you can do at the time is add scope, although floats on the rode may help.

Terence Thatcher

We have a Fin Delta 2 for use on our Morgan 382. We have never had to use it in conditions above about 25 knots, so I can’t give a good report on its effectiveness in significant wind with roller furling sails removed. (And I carry a hard nesting dinghy on the cabintop forward of the mast.) My experience in winds up to 25 knots is this: (1) it is not difficult to set up once you get the lines measured and attached to the sail; (2) my vessel is not wide at the stern (designed in 1978) and I have solar panels on an arch above the short aft deck, so it seems to me that I never get the aft “fins” spread out as much as I should for optimum performance nor is it as far astern as might be optimum; (3) it makes some noise because I cannot take all slack out of the aft fins, but it is not so loud as to be annoying; (4) it reduces yaw, but does not eliminate it in the way that a mizzen on a ketch or yawl seems to do; (5) it may work better in constant and higher winds; each time we have used it, the winds were gusty and somewhat affected by landforms; thus, the boat would be in 10 knots and then suddenly 25 knots, which caused the boat to yaw in response to the changing wind speeds. Had the wind been constant enough to blow hard on the aft fins without regular lulls, it might have held the boat steadier. As always, thanks for raising important issues. I might try using my Shark Drogue in Colin’s way next time we are anchored in wind.

Charles Starke MD

Dear John
I’m wondering if there isn’t an easier way than a riding sail to avoid yawing. If we use a double snubber from the chain directly to both sides of the bow about 1/3 of the way back from the bow (forward of the center of effort), each leg of the snubber would quickly give a force to keep the bow into the wind. We don’t have cleats in that position, put could put snatch blocks in right position to lead the line inboard to midship cleats.
We would have to try nylon, Dacron or dyneema snubbers to lessen any bounce, but I suspect nylon would put less strain on the anchor.
Any comments and can anyone try this now?

Best wishes,
Charles
Charles L Starke MD FACP
s/v Dawnpiper

Eric Klem

Hi Charles,

From a practical standpoint, I have not had much luck with this on monohulls but it is extremely useful on multihulls.

If you used a dyneema bridle, you could think about it as wherever the bridle meets, that is the equivalent of where a single line snubber goes through the first fairlead.  Having this point further forward is always good as it means that the restoring force has a greater lever arm so produces higher restoring yaw torque.  The tricks are:

You loose the benefit if the boat ever yaws enough that one leg goes slack.  Otherwise you would simply making a really long bridle but unfortunately, most monohulls would be limited to the benefit from a relatively short one.  However, a multihull can use quite a long bridle because it spreads the legs so far apart so it can really move that point way out in space.

Our hypothetical dyneema bridle only makes sense if we are anchored on a rode with give.  In practice, we usually use a nylon bridle so that it acts as a spring because anchoring with just the chain catenary and elastic stretch yields high peak loads.  The result of this is that the geometry of the bridle changes which means that the point in space where the legs connect is no longer truly fixed, it moves around a bunch.  The result is that this is not as effective as you might otherwise think, it is still helpful on a multihull and a few monos that have a lot of beam forwards.

Eric

Stein Varjord

Hi Charles,
I’ve actually tried some alternatives in this line of thought and found that on a monohull it was hard to notice any difference. On a multihull, however, it has a very significant effect, to the degree that I feel a riding sail might be mostly not necessary on our cat. We always use a two part nylon snubber.

The reason for the lacking efficiency on monohulls is the insufficient width, of course. When the boat yaws, the tension difference between the two parts needs to be quite immediate to stop the yaw at the start. The pull needs to be applied as far forwards and to the side as possible. I guess that could be remedied by rigging booms to each side from the bow, to make artificial width. Probably that’s too cumbersome to become popular.

Marc Dacey

Stein, your comment has made me think of rigs such as “flopper stoppers”, which are meant to lessen roll at anchor (see https://www.cruisingworld.com/how/reduce-boat-roll-flopper-stoppers/). I wonder if such a setup could be used in a slightly different form to tame yaw? Probably too much bother, as you suggest, but it does address the lack of comparative beam on a monohull.

Stein Varjord

Hi Marc,
You’re probably right. Several monohulls also have booms to run two headsails wing-on-wing. I guess they could also be used for something like this, with quite a bit of effort…

Marc Dacey

Thanks, Stein. Your comments from the “catamaran in the Baltic” point of view are always informative.

Andrew Climie

I have a riding sail on my Cole 43. Forefoot very much cut away, twin headsails on furlers (Slutter), so used to yaw badly. I did some homework, had a riding sail made by the local Doyle’s loft to my specs.. . It is small, heavily cambered, set quite low on back stay with hanks and pennant, and importantly, sheeted through a block on the rail, not midline. I started sheeting midline but boat would search back and forwards; sheeted to the rail she sits quietly weathercocked just a little.
When leaving boat on mooring for a while, I remove headsails and don’t set the riding sail. Less to go wrong.
I had a folkboat years ago with 20m chain/nylon rode set up. Yawing was much worse as the nylon acted like bungy cord. A less stretchy rode would have been preferable.
I can look for photo of riding sail if anyone is interested. Cheers

Stein Varjord

Hi Andrew,
I found myself slapping my own forehead for not thinking about what you mention: Setting the riding sail at an angle to the boat centre line. This should give a similar effect as the two element Findelta riding sail. The angled riding sail will constantly push the boat a bit to one side of alignment, and the non aligned boat hull will constantly push a bit the other direction. The two small pushes will always seek to balance each other. This seems more stable than a single aligned flat riding sail, which has to “tack” constantly. I obviously haven’t tried this, but I will make one, as I’m confident that it’ll work. Even though our cat is fairly stable with a bridle, I think a riding sail can make it even better.

William Murdoch

I have a flat cut traditional riding sail and use it. It cuts the boat yawing (as measured by changes in the apparent wind angle) in half.

I sheet the riding sail tightly on the boat center line. As the boat yaws and the wind crosses the bow, the sail snaps from one side of the boat to the other and the sail immediately begins to resist further yawing in that direction. I find sheeting in the center line to be superior to sheeting to the midship rail.

My data is in post 1 and a photo of the sail is in post 7 of this thread. https://www.sailnet.com/forums/pacific-seacraft/191562-riding-sail.html

In Drew Frye’s Practical Sailor comparison of a Sailrite flat sail to a Fin Delta, the Sailrite sail was 20.5 sq ft and the No 2 Fin Delta is described on its website as “8′ along the bottom; 8′ high” making it larger even ignoring that it has two sides.

Bill

Howard Peer

I’ve not read all comments yet so apologies if this has bee covered.

A question and some musings.

44’ steel center cockpit, arch with 2 big panels, plus 5’ sprit. She yaws more than I would like.

1. Have added, welded on, a second eye at the cut water. 1/2” SS plate. I think moving the attachment point back and lower would help the geometry. I would likely have a 2nd attachment behind that as a back up.
2. I have heard it suggested to drag a 2nd anchor off the bow. Our primary is a 125lb Mantus. I could drag the 66lb spade. Should do something positive?
3. Split backstays. I carry a small hanked in riding sail. I haven’t tried it yet, keep forgetting it. I may use that as a stabilizer. It would bias things to one side, might make it worse. Will have to try.
4. I have a Sea Break sea anchor. Musing how that would work as a riding sail? Tie it off to the arch. (1-1/4” schedule 40 electrical conduit- strong). Let it sail in the wind. May do something. Worth a try?
5. Off topic. Windless night, we were riding to the current but had a substantial swell coming in 180° to the current rig he on our transome. The pitch was awesome. I rigged the Sea Break with a 15lb dingy anchor and deployed it from the arch. It reduced the pitch considerably. Without the anchor as weight the current just drug it behind us and made it useless.

Toby Sylvester

Hi John,
I was interested to read your comments on the Hallberg Rassy 38 responding so well to a riding sail. I had a backstay sail made a few years ago for my HR 382 but I think it was too small to be effective. I am currently confined to the boat at anchor in Turkey where we have been having some gusty conditions with a lot of uncomfortable yawing. Having just spent the afternoon trying to resolve the issue with what we have on board the solution has been found! Our paddle board strapped horizontally to the backstay provides the perfect aerodynamic fin. Without this we had been yawing 60 degrees off the 25knt gusts; with the paddleboard in place we are now only yawing 30 degrees, making an enormous difference down below. I think a market for solid honeycomb material inflatable riding sails is waiting to be exploited! Here is a picture if the link works. https://ibb.co/QNmGt7f

Best wishes
Toby

Stein Varjord

Hi Toby,
That’s good creative use of items onboard! If all items have more functions, we can make do with fewer items. Fewer items mean fewer repairs, as items we don’t have won’t fail. 🙂 (The KISS principle). I notice that your boat has two furling head stays, the mast reasonably far fwd and a sprayhood also fairly far fwd. All contribute to push the centre of windage fwd too and give a poor balance with the boats under water areas, as John has explained.

I think your riding sail does look to small, as you suggest. I also think you might get a better effect from your SUP board if you angled the end of it upwards so it gets above the wind shadow of your sprayhood. That makes it start the corrective action earlier and also gives it more power.

I have not experimented with this, but in other comments in this thread some have reported success with putting the riding sail not aligned with the centre of the boat. I think this makes sense and might be worth trying. The riding sail (and SUP) at an angle to the centre line will try to push the boat into a bit of an angle to the wind, while the boat, having one hull siden more exposed, will try to push the opposite direction. A constant “power struggle” between the two. Each element always pushing, and always in one direction.

If they’re both centred, the riding sail etc will have to go through a zero position at every orientation change. That delays the corrective force. I think this “power struggle” principle is the reason why plow shaped riding sails seem to perform better than single layer sails. By using the boat hull as the other “sail”, you might get the same effect.

Toby Sylvester

Hi Stein,
Thank you for your comments, I will certainly try adjusting the sheeting angle of the sail and the height of the board tomorrow to see if that improves things any further.

Thomas Nygaard

I have very good experience with the FinDelta, just make sure to keep it tight. If not, just a lot of noise and flapping. When correctly set it allows a proper level sleep at night in a Force7-8, as opposed to almost falling out of your bunk by the heel in each yaw turn.

Chuck Batson

Back here following the mention of riding sails on the kellet article. I recently rigged a Fin Delta at anchor in around 20 knots of wind. I’m not clear on how it’s supposed to behave, but there was still plenty of “hunting,” maybe +/- 80 degrees to the wind at the extremes (yes, almost beam-on at times). It seemed that as the boat began to go off dead upwind, the orange leading edge of the Fin Delta (luff?) would fill and contribute to yaw, although I had the luff as tight as I could get it. Terence Thatcher’s experience (in an earlier comment) appears to confirm that yaw is reduced but not eliminated with the Fin Delta. I’m open to all possibilities, including that I rigged the thing wrong or not far enough aft, or that possibly its true utility is in much more substantial winds. I wonder, is there a video or detailed report somewhere on the use and expected behavior of the Fin Delta? The Banner Bay Marine videos have some useful tips, but don’t show it in action with a decent breeze. That’s been my one and only time flying the Fin Delta so far, so I’ve very limited experience with it.

Mike Drummond

Chuck,
The aero yawing moment is caused by the shape of the yacht above the waterline obviously.

In comparison to other yachts,
Do you have a high bow sheer? is there a dinghy stored on the bow? Mainmast large and forward?

I think the trend is that these are features that increase yaw moment, but I can’t offer a quantitative measure.

The balancing yaw moment from a riding sail is more effective if it is further aft.

Chuck Batson

Hello John and Mike, thanks for your thoughts. I’m in a Cabo Rico 34. Aside from it being cutter-rigged, and having a furling headsail, there’s nothing special to distinguish it from other sloops. I don’t have any reason to believe there’s any other cause of extra wind resistance up front (dinghy, freeboard, etc.).

The aft ends of the delta (the clews?) were maybe 5 feet forward of the backstay. Given the size and shape of the sail, and its placement, relative to the aerodynamic layout of the boat, I was definitely expecting very little yaw. I’ve been in contact with the manufacturer of the FinDelta, and they’re confident that what I experienced was not expected and could be resolved. They offered some suggestions I’ll try next time the opportunity presents itself. I’m proceeding on the assumption that I had it rigged incorrectly, and will report back here with learnings.

Chuck Batson

John – thank you for this. You may have cleared up some faulty logic in my mind. With the sails up, there’s a slight weather helm – CE just aft of CLR as designed. Without realizing it, I’d made the mental leap that the aerodynamics while at anchor would also be similar to other vessels, which as you point out, is not necessarily so. I’ll have to pontificate on this further. (A moment while I get my monocle and pipe haha…)

Andre Langevin

Don’t laugh but i was caught in the middle of the night by a catabatic wind in Deshaies, Guadeloupe, howling in the 32-35 range. No worry for the huge 105 pounds Mantus stuck under seafloor but quite annoyed by the yaw since boats around were very closed and catamaran are even worst. So i improvised…started the engine, put it on reverse at 1200 rpm. A little stabilization. Then at 1500 rpm and voila, the boat stays in the middle of the needle of the apparent wind. I have complete trust in my anchoring system and it seems a few hundred pounds pulling on the stern have made it. Of course i was on the helm at all the time and i would prefer the deltafin.