Average Range of Yawing at Anchor in Storms

[contrail]

Although I never never done this, I have observed another cat with a very assymetrical bridle, in other words, with one leg much longer than the other, and it did seem to ride very quietly. But this was in tradewind conditions, not a storm. Take this for what it is worth.

[Benz]

In a steady wind with no current, my boat (heavy full keel) yaws only slightly, even if on my nylon storm rode, but if there's a current, or the wind is flawing, it tends to ride around. How are you cancelling the effect of current and flaws in your testing?

[roland stockham]

The only time I get problems with yawing is when wind and tide are in conflict. One one occasion in Langfort UK I set a drogue as we finshed up spinning a full 180 with about 4kn of tide at right angles to a full gale. If you are having problems in a specific location maybe check what the tide is doing. Underwater hull shape as much as weight and windage seems to be a significant factor. I am aslo curious about your comment about 'when the chain is lifted of the bottom' surly if all the chain lifts you are in danger of dragging and need to let out more chain? I have anchored in 50kn+ without the chain lifting.

[robert sailor]

In winds to 20 knots we sail very little at anchor but as the wind increases so does the sailing. In 40 plus knots we can sail thru 120 degrees with heavy snatching at each change however after purchasing and using a riding sail it reduces it by about half with no snatching when we change direction. Our boat is 42 feet and medium displacement. Lots has to do with topsides as a sistership sails much less than we do at anchor.

[Cheechako]

Originally Posted by thinwater

It is about balance, not weight. In fact, yawing through large angles is a common problem with >50,000 ton ships! Billknny's boat isn't light.

https://www.piclub.or.jp/wp-content/...l.25-Light.pdf

Yeah, probably true. Most "yawers" I see are fin and spade. My heavy ish boats were longish keels, although my Cat didnt yaw either. Not more than 5 degrees +/- I would guess on any of them.

[thinwater]

a. The test area has very little tide, generally less than 0.2 knots, and generally less than that. I've been on boats doing 360s every few minutes, and that is a whole nuther' topic.



b. Unless you are anchored in very deep water, very long scope, and grotesquely over-sized chain, the chain is coming off the bottom at 50 knots. I have not implied that it is straight, only that no more than a few links remain and that they cannot be pressing into the bottom with more than a dozen pounds of force, quite near the anchor. This is a the engineering of it, and the math is well established , enough to have built magnificent suspension bridges. It has also been measured on boats and observed directly. In shallow water with short scope, this can happen in as little as 15 knots (personal observation). In 20 feet and 7:1 scope with BBB chain it will take 50 knots (also personal observation). But even if there are a few links on the bottom, that won't be enough to damp yawing. There is likely enough catenary to damp impacts, but catenary does not prevent yawing. If the boat does not yaw, that is because of other balance factors, not the chain. Same with kellets; they are off the bottom in strong storms.



Balance varies greatly between boats, according to keel shape, rig, gear on deck, and canvas. I'm not seeing a single factor that promises no yawing. It's a combination of factors. I'm also pretty sure I could make any boat yaw or stop any boat, with some adjustments.


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So the question is, how much can a riding sail help, and which ones are best? I've done a few tests, suggesting traditional riding sails are like CQR anchors; they kind of work, they were good in their day, but they have been surpassed.

[tomlisasail]

What's the issue with yaw at anchor? Is it comfort or ability of the anchor to hold. I have a Rocna 25 on a Catalina 36 which weighs 14,000 lbs..

[tomlisasail]

Never mind Thinwater answered my question. I don't understand why deep water makes a better holding situation during heavy winds.

[MJH]

Originally Posted by thinwater

How much does your boat yaw at anchor when it's really blowing, enough to get the chain just off the bottom (at least 35 knots sustained)? Have you looked at the compass, perhaps trying to separate wind shifts? I've watched my compass and I have observed others, but I never really focused on others.

I've seen light boats with dinghies on the bow sail though more than 120 degrees. I've seen lots of boats sail through over 90 degrees. My PDQ, with a long bridle was about 35 degrees, but without it she was all over the place, more than 100 degrees. My tri is about 30 degrees with bridle and rudder up, but as much as 130 degrees anchored by the bow alone. My impression is that in strong conditions, 50-80 degrees is pretty common among monohulls, although I don't think they all realize it ("it's the the other guy"). These same boats may sit still when they have some chain on the bottom.

Please only comment if you have studied the compass bearings during strong conditions, or if you anchor using rope. In lighter winds, with chain on the bottom, you won't yaw much.

(I'm testing three riding sail designs on a nervous boat)

I previously owned a San Juan 28 sloop for 10 years. As a fin keeled boat it would dance about while at anchor. I had a riding sail (10'x9'x5') made and it made a significant difference while at anchor. It would hank to the backstay, lift with the main halyard, and anchor forward to the cabin top (no dodger); it worked very well. The most extreme wind experience I had was at Port Hardy, BC where I recorded 39K winds at anchor. It was a bumpy ride but with minimal yawing due to the riding sail.

I now have a larger Tayana 42 cutter and considering a riding sail for it. With her long fin keel and skeg rudder she dances more than I would like despite her heavier weight. However, as someone has already mentioned, I'm also concerned about lifting with the main halyard due to my backstay SSB antenna wiring, the 16.7' boom, and dodger with solar panels in the way...it would have to be rigged very high which, I feel, would significantly reduce the desired calming affect.

~ ~ _/) ~ ~ MJH

[wsmurdoch]

Originally Posted by AndyEss

I hope to add data logging to my nav system so I can research how to optimize my cruising experience.

I am using NavMonPC from NavMonPc to plot data from my boat's electronics via NMEA 0183. You can see my data display by following the link in post 5. I don't recognize what billknny is using, but it looks interesting.

I am always looking for better.

Bill

[Montanan]

I have heard but have no direct experience that if one uses a long bridle and ties it off further back from the near bow that the bridle rode acts like bookends to mitigate the bow from turning abruptly as the bow has to push against one or other of the length of bridle and the side unto which it pushes becomes tighter as it tries to form a bend and pulls against the tie off more on that leeward side of the vessel.

Perhaps attaching the bridle to midship cleats or to winches would enable constraining the movement between the long formed rode:

/\

[contrail]

One other thing that I have found, which seems to help, is to drop a lot of chain between the anchor roller and the point where the snubber or bridle attaches to the chain. By a lot of chain, I mean enough to drag on the bottom. Whether it is the dragging on the bottom, or the kellet-like effect of all that weight pulling down at the snubber chain junction, I do not know. Probably both. Never measured it, however. And it is probably not good for the bottom, though no worse than anchoring by chain, in the first place.

[Montanan]

I have read that if one ties one leg of a bridle toward an aft position and then tighten that bridle to cause the vessels stern to shift [bias] to windward that it will ride at an angle to the wind and then not yaw as much. Probably somewhat similar to tying off a riding sail so as to be off center so as to bias the boat to an AWA.

[olddog57]

Forgive me this theoretical consideration: after a wild night at anchor in my very heavy long keeled 34-foot motorsailer (almost 12 ton) with not so much (30-35 kn) wind I thought on this issue, and decided to use asymmetrical bridle (still did not check if it helps)

Sailing at anchor is a kind of self-oscillation.
With an (almost) symmetrical profile and even an (almost) constant wind direction such oscillations are easy to start, as to sail out of the equilibrium state (the chain and the boat both along the wind direction) not much force is needed - say slight wind change is quite enough.
If the profile exposed to the wind is significantly asymmetrical, then the equilibrium state is much more stable - hence any yawing has to be reduced.
So, any asymmetric setup (different length bridle lines, riding sail set at a substantial angle to the center-line) should abate yawing

[Dockhead]

Yawing at anchor is a good way to jerk the anchor out of the bottom, or chafe or break your ground tackle. My philosophy has always been -- just don't do it. Therefore, I can't answer your question.


I rig an anchor spring line when it gets boisterous. If that were ever not enough, I would rig some kind of riding sail off the backstay. I would not let it happen. It's not good.