Swinging at anchor

[cardude01]

I removed the paddleboard off the bow, increased the scope a bit and removed my snubber and it seemed a bit better.

Our first sailing "adventure". Weatherman said it was going to be squally all day so we planned to stay in the harbor all day, but we got bored. I figured, we are in the protected sea of Abaco-- how bad could it be?

Squalls are windy! I got caught in one not 30 minutes after raising all the sails. We were motorsailing nicely with about 12 knots on the beam, when I noticed the big black line of thunderstorms coming at us. I didn't reef I time and the boat was healing
over at an umcfortable level my crew let me know. Wind showed 25 knots on the guage. We turned into the wind to try to reef. The jib came in fairly easy but the main was flapping like crazy and in couldn't get it to furl in. Raining like crazy so I missed that I didn't release all the lines I was supposed to from the clutch things. When I did that I finally got the main in. Left about 1/3 out to help steady us. We are on a rocking mooring now realizing we need to pay more attention to these storms!

 

[twistedtree]

I went down this path a year or two ago. Our boat has a lot of windage and swings like others. Somewhere I found a good paper explaining the dynamics that cause swinging back and forth. It was the most credible source I could find as opposed to anecdotal information.

It has to do with the windage force point being forward of the boats pivot point. If the boat swings at all, which it will always do at least a little, the forward windage point want to push the boat around the pivot point. It's like moving the feathers on an arrow forward until it becomes unstable.

When facing into the wind, the windage is from the forward facing profile of the boat, so the forward hull and house face. As the boat starts to swing and presents itself more broadside to the wind, the windage becomes increasingly influenced by the side profile of the boat, and that typically moves the center of windage aft. As it moves aft, the swing diminishes, then reverses as the boat tries to tail into the wind. But because it's unstable, it just oscillates back and forth.

All his leaves three possible solutions, most impractical.

The fist is to move the forward facing center of windage further aft. Short of ripping your boat apart and rebuilding it, you can forgettaboutit.

The second is to move the anchor attachment point further forward. This creates less relative distance between the windage point and pivot point, and reduces the windage leverage. Again, short of building a long spar and anchor pulpit, you can forgettaboutit.

The third is to create more aft side windage so there is more to counter the swing and reduce it's magnitude. This is where aft steadying sails come into play. On some boats and for some owners, this might be feasible. But for most of us, I think you can forgettaboutit.

I tried bridle and no bridal, snubber and no snubber, uneven bridal and not, and even tying the snubber off just one side of the boat to unbalance the wind drag. None of it made any difference. So I finally decided to.... you guessed it .... Forgettaboutit, and just go cruising.

 

[psneeld]

I believe the fourth option is the unequal bridle or springing the rode.

This gives 2 attachment points and in a perfect world, no or less swinging.

Much like 2 bars under a seesaw, either it wont move at all or less than a full swing back and forth.

Has worked for me and others that have written about it. Not perfect but better than nothing when the swinging is extreme.

 

[Simi 60]

So I finally decided to.... you guessed it .... Forgettaboutit, and just go cruising.

Same for us. To much head, not enough tail.
Has not been a problem for us but probably gets those "to close anchorers" worried at times.

 

[twistedtree]

I believe the fourth option is the unequal bridle or springing the rode.

This gives 2 attachment points and in a perfect world, no or less swinging.

Much like 2 bars under a seesaw, either it wont move at all or less than a full swing back and forth.

Has worked for me and others that have written about it. Not perfect but better than nothing when the swinging is extreme.

This must get into the specific dynamics of a particular boat. I tried all of those to no avail on our boat.

 

[Nomad Willy]

What I am going to try the next time we're at anchor is to pull in some anchor line (from ahead of the bow) and tie another line onto the anchor line 15-20' down the line from the bow. Then tie the tag line at the stern. I could go 30' (the length of our boat) and then be broadside to the wind in light winds. Attaching the tag line closser in at about 15-20' would probably work better. I'll bet there will be no swinging then.

Obviously this idea is only for daylight hours in light winds.

Doubt if we're going to anchor out before I'm in a sling though. Would only take a few minutes to rig up so I'm hoping someone will try it and report.

 

[bayview]

Twisted: In your case I would try a riding sail set at the aft end of a stay from the mast to the aft end of the boat deck.

 

[AusCan]

I removed the paddleboard off the bow, increased the scope a bit and removed my snubber and it seemed a bit better.

Our first sailing "adventure". Weatherman said it was going to be squally all day so we planned to stay in the harbor all day, but we got bored. I figured, we are in the protected sea of Abaco-- how bad could it be?

Squalls are windy! I got caught in one not 30 minutes after raising all the sails. We were motorsailing nicely with about 12 knots on the beam, when I noticed the big black line of thunderstorms coming at us. I didn't reef I time and the boat was healing
over at an umcfortable level my crew let me know. Wind showed 25 knots on the guage. We turned into the wind to try to reef. The jib came in fairly easy but the main was flapping like crazy and in couldn't get it to furl in. Raining like crazy so I missed that I didn't release all the lines I was supposed to from the clutch things. When I did that I finally got the main in. Left about 1/3 out to help steady us. We are on a rocking mooring now realizing we need to pay more attention to these storms!

REEF EARLY.

The single most important thing to remember when sailing.

 

[Wataworld]

Nothing to input judt say hi i am across the way at Man a War

 

[Simi 60]

Twisted: In your case I would try a riding sail set at the aft end of a stay from the mast to the aft end of the boat deck.

And how much will that cost for a problem that isn't really a problem?

 

[Peter B]

I went down this path a year or two ago. Our boat has a lot of windage and swings like others. Somewhere I found a good paper explaining the dynamics that cause swinging back and forth. It was the most credible source I could find as opposed to anecdotal information.
I tried bridle and no bridal, snubber and no snubber, uneven bridal and not, and even tying the snubber off just one side of the boat to unbalance the wind drag. None of it made any difference. So I finally decided to.... you guessed it .... Forgettaboutit, and just go cruising.

There is one other thing that works for this. We discovered it by serendipity, in a way. If you look at our avatar pic, the extended canvas canopy down the side decks, and covering the whole cockpit, which we added to try and achieve the nice extra cover from sun and rain that the new models have as hard-top, accidentally also solved the sailing side to side at anchor issue as well. The structure acts like Twisted's example of arrow fletching, and that added windage holds us straight into the wind.

 

[cardude01]

Nothing to input judt say hi i am across the way at Man a War

Hello! We are heading back towards FL today unfortunately. Going to stop at Manjack today.

 

[Northern Spy]

http://alain.fraysse.free.fr/sail/rode/dynam/yawswing.htm

 

[Wataworld]

Us to going to stop at green turtle than on to great sale than west end than west palm

 

[Nomad Willy]

Whataworld,
Whata that have to do with swinging at anchor????
This is a thread on Trawler Form about swinging at anchor.
We stay on topic on TF.

 

[1Sailor]

They make a "riding" sail that sets on your backstay that would help. It acts a little like a Mizzen.

 

[Wataworld]

Whataworld,
Whata that have to do with swinging at anchor????
This is a thread on Trawler Form about swinging at anchor.
We stay on topic on TF.

Well thanks I should have used a private message did not mea n to offend your delicate nature

 

[ranger58sb]

We stay on topic on TF.

Yeah, right.



-Chris

 

[Jeff F]

Sydney has mooring areas catering for sailboats and powerboats, it is recognized that sailboats and powerboats swing differently, space has to be allowed for that to happen to avoid collisions.

I helped manage a mooring field when I was a kid. We were in a river mouth with the prevailing wind against the current. The sailboats would generally all point the same way, and their moorings could be closely packed. But the powerboats would often be pointing in the opposite direction from the sailboats in the transition zone between wind and current dominance, as they had more windage and less underwater. That's a case where short scope and/or a Bahamian moor really helps, limiting the distance of the swing when a 180 degree shift takes place regularly and minimizing the problems caused by differing boat characteristics.

 

[twistedtree]

Nothing to input judt say hi i am across the way at Man a War

I agree it could be done, and it might help, but it's not a big enough issue to go through the hassle of rigging and experimenting to see if it helps. And even if it does, I don't want to be putting a stay sail up and taking it down every time I anchor.

 

[twistedtree]

There is one other thing that works for this. We discovered it by serendipity, in a way. If you look at our avatar pic, the extended canvas canopy down the side decks, and covering the whole cockpit, which we added to try and achieve the nice extra cover from sun and rain that the new models have as hard-top, accidentally also solved the sailing side to side at anchor issue as well. The structure acts like Twisted's example of arrow fletching, and that added windage holds us straight into the wind.

We have considered enclosing our cockpit, and I have wondered how much it might help reduce swinging. But I think I would take it as a pleasant side effect rather than a primary reason the enclose.

 

[Nomad Willy]

So twistedtree are we swingers or not?

The only objection I've got is that the scenery is in almost constant motion. Gets to the point that I don't want too look out the window.

I think bridals work well. I've seen power boats w bridals sit motionless when we were swinging a lot. I've seen bridals that were attached to the boat through chocks that were too close to the bow and hense too close together. That would be the case w our boat. Anything aft of there that would be further apart and probably work well but it may put heavy side loads on the stanchions for the life lines. I have samson posts midships but the lines may abrade against the hull. Oh well I can't rig a bridal anyway unless I change to chain. I lost my chance to do that when I bought my 2nd capstan.

 

[tadhana]

Our Helmsman does not seem to swing unusually compared to other boats. However a bridle almost eliminates any swinging. Due to the bow flare, our bow chocks are nearly 3 feet off the center line. This give the bridle a wide base. As soon as the bow starts to move to port, the port bridle line takes the load, the starboard leg goes slack, and it stops the boat moving to port. The reverse to starboard. So I cannot explain why your IP is swinging differently from other sailboats, but a bridle, particularly if the two legs are widely separated, will reduce the swinging.

 

[Woodland Hills]

In my experiences and what I have read, to help prevent swinging, you use a bridle but with uneven legs.

With the attachment point right in the center, the wind can get to either side and the tiniest push stats the back and forth. Once itvgoes to the farthest point, it now has the momentum to get not only to center but beyond. Andvthen it starts all over again fartherst point to farthest point. By offsetting the bow with unequal legs, you stop some of the swings entirely and make the swing to one side less (at least in theorry....but I too have noticed less to that one side in real life).

So try a bridle both ways and see what happens. Just use a coupke dock lines to see if the bridle helps, but if only the uneven legs help, and no better than your current setup, then a riding sail or a drop weight (similler to a sentinel/kellet) off your bow might be the next moves.

Bingo! This has been my experience as well. I find that an off center tie allows the boat to take a set against the wind or current to one side or the other and mostly stay there.

 

[McGillicuddy]

Hello! We are heading back towards FL today unfortunately. Going to stop at Manjack today.

Don't do it! Remnants of TS Emily in your path! I know your family do not enjoy uncomfortable rides.

 

[FF]

"And even if it does, I don't want to be putting a stay sail up and taking it down every time I anchor."

With all that windage fwd , a sail would have to be huge.

Anchoring by the stern might work with least effort.

 

[cardude01]

Us to going to stop at green turtle than on to great sale than west end than west palm

Sent you a PM. We are in GTC in White Sound.

 

[cardude01]

Don't do it! Remnants of TS Emily in your path! I know your family do not enjoy uncomfortable rides.

We are in a protected spot in GTC waiting on weather. It was bad yesterday and supposed to be bad today, but according to Chris Parker supposed to be nice from Wed-Sat for a crossing back to FL. Hope he's right.

Two of my family had to fly back home so just me and my eldest son now.

This was yesterday. Winds around 25-30. Anchored in an unprotected spot to ride it out because I couldn't see to get into the sound, and it sucked. Put out all my chain and the Rocna finally caught after dragging 100' or so. Glad wife wasn't aboard for that episode.

 

[bayview]

Sometimes all it takes is a large flag aft to kill the sailing at anchor. IMO there are no universal solutions.
A sun screen aft would also add windage.