Weaving Back & Forth at Anchor

[Bash]

Originally Posted by Joli

As Bash said, cockpit enclosures may help if it moves the center of resistance aft.

When I specified that weather cloths had helped, what I'm talking about is much less aft resistance than a full cockpit enclosure. As a matter of fact, our weather cloths are less severe than most, because they only extend between the top and middle lifelines, while most weather cloths go down to the toe rail.

Hard to believe, looking at the photo below, that such a slight remedy could make a difference, but in our case it certainly did.

[GMac]

I've clocked over 4kts a couple of times while at anchor. I use rope and chain and like plenty out which certainly doesn't help. I tried locking the rudder in differ places, made no difference really. Tried hanging stuff off the back again without great success. I don't like riding sails and heavily suspect that would only increase my speeds. One evening I got a tad wild so grabbed a bucket and had a play.

Hmmm.... off the bow seemed to work so I played with it a little until I have my current drogue type arrangement. Still wonder a little but no where near as far or at the big speeds.

The problem I have and the main cause of my sailing is the keel. It is a long way forward in comparison to most boats so once I get a little cocked to the wind off I go and at the end of the arc the stern sort of 'flicks' around and automatically aims us at a nice angle to sail all the way back again. We easy out sail most multis at anchor, that's how bad we have/had it.

The drouge does work and works well. Whether it will work for every boat, not having tried I don't know but it could be worth a try if you have run out of other options. Start just with a bucket and that should give you a bit of an idea whether it may or may not. That's how I stumbled across it, that and a nice bottle of red wine

No I'm not going to shift my keel

[swagman]

Originally Posted by lancelot9898

Agree with your conclusions, but the idea that a drogue would work is doubtful in my mind since its usefulness would depend on the speed that it's pulled through the water. When my boat "hunts" at anchor it goes slowly from one side to another. Even with full gale force winds I don't think the speed throught the water is sufficient to make much difference. When I was anchored in a Cat 1 hurricane...yes then the speed through the water is there, but then a second anchor on a very short scope would probably be more useful in limiting the "hunting". I do see some improvement in the hunting by locking the rudder amidship and by using a short bridle. Not sure if using a short scope in much benefit since a long scope would have more chain on the bottom and offer more drag, however I can understand that argument in that it limits the distance of the arc.

Good to see the debate continues but I can only smile.

A wide variety of input is always invaluable but when some advise 'I've NOT tried this and I think' and others advise 'I've DONE this and I think' then guys, you decide who you'll listen to.

Just like GMac above, I can't speak for every boat. I have absolutely no idea if on any other boat the drogue works better or worse than a riding sail, dodgers, a drogue over the back, shortening or lenthening scope etc. But I do know on a Hanse 461 the drogue from the chain worked better than all the other proposed solutions.

And as the first question was about a yacht of similar design, I suggest the skipper tries the drogue in this way and gives us all feedback.

BUT PLEASE REMEMBER - we did try the drogue attached to the bow of the boat as well - and it DID NOT work as well as when attached only to the chain. For me 1 - 2 metres below the waterline worked.

Cheers
JOHN

[Sandero]

There is a no one size fits all solution to the class of problems as there are multiple factors and obviously different underbody, above waterline hull form, deck configs and rigs.

The solution for your boat will begin by carefully observing its motion in different wind conditions, depths and current (of it applies).

On my boat the yawing, or sailing about on achor increases with wind speed and begins when a puff or wind shift comes from off the bow. It appears that since the bow is the secured point the boat will try to weathervane or make the smallest presentation to the wind and will try to pivot around the bow. The pull of the anchor is no longer aligned with the CL as the anchor aligns it gives the bow momentum and it passes through the wind. Depending on how strong the force of the wind and the underbody resistance and its location and the windage fore and aft will determine the magnitude of the oscillation of the yawing.

Deep fin keels and spade rudders high aspect will offer less resistance below the waterline. To slow the movement of athwartship you can add drag below the waterline to resister the pressure above the water. A drogue deployed off the stern will slow the athwartship movement of the stern, resistance added at the bow will help resist the bow moving off CL.

You could drag a bucket full of chain or weight from either or both location or a drogue if you can get it to work effectively.

Other strategies involve balancing the windage above the waterline a to assist in weathercocking the boat. This usually means adding windage aft, such as a riding sail and the area of added windage will vary with the wind force you are dealing with I suppose

For Shiva in winds less than 10k the yawing is acceptably small,. but more than full keeled and or fetich rigs. At 10-20k a riding sail is my preferred solution. I can rig it pretty quickly and it also assists in anchor retrieval so I might not drop it until the anchor is up and I am underway. I would be more concerned with fouling the rudder or even the prop with something rigged below the waterline deployed aft.

Here's a handing program I download some time ago which models the yawing of a boat on anchor. Plug in your numbers and see if it works
-Yawswing.xls- but you'll have to email or message me to get it, because it's too large to upload as an attachment.

[Extemporaneous]

Originally Posted by defjef

Here's a handing program I download some time ago which models the yawing of a boat on anchor. Plug in your numbers and see if it works
-Yawswing.xls- but you'll have to email or message me to get it, because it's too large to upload as an attachment.

Might be the same, along with other worksheets?

http://alain.fraysse.free.fr/sail/rode/synthesis/synt.htm

Regards,
Extemp.

[opsailor]

With the advise given above, we have just ordered this sea anchor from Defender to use as a drogue on our anchor line. Wish us luck; we won't know how it works until we get to the Bahamas in January.

http://www.defender.com/product.jsp?...87033&id=87172

[Sandero]

Extemp,

Correct... That's the spread sheet reference.

[Extemporaneous]

Along with using a Sea Anchor off your bow to combat your boat sailing around at anchor, I also wonder if a Sea Anchor could be placed half way down your anchor rode in order to help (not replace) your snubber for shock/energy absorption/dissipation. If one had 150 feet of chain out (fairly bad seas) and while running it out, attached the snubber 50 to 75 feet from the anchor. I'm thinking this may have benefit with an all chain rode, working with the catenary curve of the chain. It would/could? keep some of the greatest forces more horizontal on the chain/anchor and help alot with shock loads on your boat.

Perhaps this approach has been/is used, but I haven't done this or read about it.

Your thoughts?

Regards,
Extemp.

[svHyLyte]

I suspect this is your situation (Image on the left):

See How Banner Bay Pointer Works

And I suspect this is your solution:

https://www.bannerbaymarine.com/stor...red&prevstart=

See the following:

YouTube - How to raise the FinDelta anchoring sail.

Works for us.

FWIW...

[Extemporaneous]

Originally Posted by Extemporaneous

Along with using a Sea Anchor off your bow to combat your boat sailing around at anchor, I also wonder if a Sea Anchor could be placed half way down your anchor rode in order to help (not replace) your snubber for shock/energy absorption/dissipation. If one had 150 feet of chain out (fairly bad seas) and while running it out, attached the snubber SEA ANCHOR 50 to 75 feet from the anchor. I'm thinking this may have benefit with an all chain rode, working with the catenary curve of the chain. It would/could? keep some of the greatest forces more horizontal on the chain/anchor and help a lot with shock loads on your boat.

Perhaps this approach has been/is used, but I haven't done this or read about it.

Your thoughts?

Regards,
Extemp.

Just corrected the oringinal post. I meant to say Sea Anchor not snubber. (see above).

Regards,
Extemp.

[thinwater]

Originally Posted by Extemporaneous

Just corrected the oringinal post. I meant to say Sea Anchor not snubber. (see above).

Regards,
Extemp.

be too great, but what if there were a drag devise shaped something like a radar reflector that could be slid down over the chain, just below the waterline? It would be like having more keel forward and would slow all chain movement.

Just a tickler. I can't see it, yet.

I have a cat, and with a wide bridle, I don't move. However, in the soft Chesapeake mud, a 2nd anchor on nearly vertical scope seems most plausible. Lots of side-to-side drag.

[swagman]

Originally Posted by thinwater

be too great, but what if there were a drag devise shaped something like a radar reflector that could be slid down over the chain, just below the waterline? It would be like having more keel forward and would slow all chain movement.

Just a tickler. I can't see it, yet.

I have a cat, and with a wide bridle, I don't move. However, in the soft Chesapeake mud, a 2nd anchor on nearly vertical scope seems most plausible. Lots of side-to-side drag.

What? You mean like hanging a drogue from the anchor chain?



JOHN

[Extemporaneous]

Originally Posted by Extemporaneous

Along with using a Sea Anchor off your bow to combat your boat sailing around at anchor, I also wonder if a Sea Anchor could be placed half way down your anchor rode in order to help (not replace) your snubber for shock/energy absorption/dissipation. If one had 150 feet of chain out (fairly bad seas) and while running it out, attached the snubber SEA ANCHOR 50 to 75 feet from the anchor. I'm thinking this may have benefit with an all chain rode, working with the catenary curve of the chain. It would/could? keep some of the greatest forces more horizontal on the chain/anchor and help alot with shock loads on your boat.

Perhaps this approach has been/is used, but I haven't done this or read about it.

Your thoughts?

Regards,
Extemp.

Originally Posted by Extemporaneous

Just corrected the original post. I meant to say Sea Anchor not snubber. (see above).

Regards,
Extemp.

Originally Posted by swagman

What? You mean like hanging a drogue from the anchor chain?



JOHN

Well that's certainly what I was thinking. The exact shape yet to be determined. I do agree that what ever shape it would have to be maintained open somehow.
This would slow and make more uniform the energy when your chain anchor rode transitions from a Catenary shape to a straight chain position.
It may also have some benefits in side to side motion, but that likely depends on how far down your anchor rode it is.

Now on occasion I do come up with some stupid stuff, but what's the head banger on this one?
Let me know, I can understand words better than icons.

Extemp.

[eyschulman]

I repeat what works- riding sail-2nd anchor-anchor spring line-in settled weather light wind stern to anchor(use bow anchor line extended to stern so if wind picks up release to bow)- in north west(steep bank) stern to with land line.

[Extemporaneous]

Originally Posted by eyschulman

I repeat what works- riding sail-2nd anchor-anchor spring line-in settled weather light wind stern to anchor(use bow anchor line extended to stern so if wind picks up release to bow)- in north west(steep bank) stern to with land line.

Okay everyone that's it, see above for the only thing that works!
I guess were done here.

Extemp.