420: Anchor Antics

[PiratePete56]

Looking for advice on anchoring an early L420, we have had for 3 years now. I suspect advice from other model owners will apply. We seem to “ Sail” all around the anchor in lighter and medium wind conditions , often with the anchor behind us ( marked by a small float on a recovery line) . No, I am not anchoring with sails up, detailed in some other threads! This often results in chain contacting the hulls, chain grab releasing, and violent jerks when the boat oscillates from side to side. Also chain twist from multiple rotations if we hang in the one spot too long. The boat seems to be pushed forward with the wind on a rear quarter. These boat have a lot of aft windage, not helped with clears around the cockpit.
A Drouge helps if a current present, but otherwise creates problems getting wrapped around rudders ect. Rudder position experiments don’t see to work. Tried a second small anchor that can get dragged around, but this risks gets tangled with the main rode. Forward yoke size about 7 meters, but shortening no help either.
Is this a characteristic of all cats, or Lagoons in particular? Any suggestions or hints welcomed.

[billknny]

Are you saying the anchor is behind the boat, even with no significant current? Just wind pussing the boat around? That seems...odd.

All boats will behave in unpredictable ways if the wind and current are from different directions. That is just the nature of the beast. No general rule is applicable, you have to deal with the situation as it comes up.

Aft windage should HELP the problem you report by assisting the bows pointing into the wind.

To avoid the "chain grab" releasing, attach with a rolling hitch. It is as strong as a chain hook and FAR more reliable at staying attached.

Catamarans with a properly set up bridle should sail back and forth at anchor LESS than other boats, not more. You say that shorter bridle legs haven't helped, and I would not have expected them too. Have you tried LONGER ones?

[Bean Counter]

Where are you anchoring, in a river?


Most catamarans will point into a strong current rather than the wind direction, until the wind has a stronger influence. When wind and current are balanced the cat can sit right on top of the anchor and point in any direction. In a swirling current with eddies like in the bend of a river the boat can do 360s. If however there is no current/tide effect then a cat on a bridle will sit pretty stationary pointing into the wind out in the open. If anchored close in the lee behind a cliff or high hill there can be a back wind affect on the boat, the mast top indicator will show one direction and the boat will be angled differently.

[PiratePete56]

Will try a longer bridle, but when its under the boat, not sure how this will help.

Probably should have added this is an intermittent effect, but once it starts up, I want to know how to stop it !

I guess there may be a current component in the behaviour. Happens a lot in rivers, but also in reasonably sheltered ( enclosed ) anchorages. Currently North of Cairns, AU inside the Great Barrier Reef, that creates tidal currents all over the place.

It feels to me to be more the wind, especially when gusty. That shoots the boat off in one direction to the limit of the rode. Jerk, rotate a bit then take off in the other direction to repeat. Luckly the anchor seems to set itself quickly.

In crowded anchorages I take care to keep well away from the neighbours, as often we lay in opposite directions to others.

Maybe its a curse from my ex wife ???

Thanks for the thoughts Guys, some things to think about here.

[meirriba]

Use longer bridle. Should be made of about 2 x 6 m lines + 4-5 meters tail. About 10m in total length.

[Sardean]

We have two 6m lines on our bridle, and found letting out a big loop of of chain (about 10 m) between bridle and boat greatly reduced our sailing around on anchor.

[meirriba]

Originally Posted by Sardean

We have two 6m lines on our bridle, and found letting out a big loop of of chain (about 10 m) between bridle and boat greatly reduced our sailing around on anchor.

Sure. It pulls the chain down, rather like a kellet/anchor angel changing the catenary.

[PiratePete56]

That sounds like it might help. Many thanks!

[clownfishsydney]

Where are you anchoring? Most cats have problems where tide/current is strong and opposite or at right angles to wind.

[PiratePete56]

Thanks for all the input on this. I now understand the problem a little better! Its occurring in low current / higher wind situations. Directions will have an influence but near opposites seem to be when I get the anchor out the back with boat oscillations across the wind. Bow stays pointed in the downwind half throughout the process, hence chain against hull and jerks when the rode limit reached.

Having some success with a undersize drogue but again tangling can still be a problem. Will be looking at some "small area sail" experiments next. Its a matter of influencing current or wind effects so that one dominates over the other.

Appreciate everyones input. Great resource this forum!

[PiratePete56]

Advice from another Cat owner provides I believe the best fix for this situation.

Tie 2 drogues between the hulls, at both bow and stern with a yoke. At the back keep the rope short enough to stop it fouling in the props or rudder. Still seems effective like this. I also cut the webbing at the tail of the rear drogue, so that the tail can brush against running gear without catching. The yoke at the front can be longer.

Didn't mention at the beginning of this thread, I was having this problem in the rivers in Far North Queensland, Croc country! So not fouling the prop was important.

Method seems to work!