Swinging at anchor

[aitchw]

I am aware of the problem with sailing boats and this year will try lashing tiller dead ahead and hard over to see what works best but what I want to know is if a small (5m) mobo with a fair amount of windage will have similar tendencies to range about and if so, in the absence of a rudder what do you do to minimise it? The boat (mobo) is cathedral hulled.

TIA

 

[oldharry]

2 anchors ? Any small boat - and some not so small will range around at anchor given the right conditions, and lashing the rudder doesnt make any difference except to save wear on the rudder pintles!

 

[harvey]

The surefire answer for us raggies is to run a steadying sail up the backstay and heave it as flat as possible (at the mast foot at a block?) . You hardly ever see a boat at anchor with one hoisted but it works extremely well and takes huge pressure off the holding gear. Without it my old boat used to swing 30 degrees either side of a 20 knot wind and with it the swing was 10 degrees. Much quieter at night too.
John

 

[duncan]

trail a small drogue/ bucket wiith middle missing sort of arrangment. If there is any tide/current running this will pick it up and will keep you more aligned with those more significantly keeled craft.

 

[andy_wilson]

The swinging is caused by the wind playing on one bow then the other. You may bring it under control by running an extra line from a side cleat or whatever you have available, and attaching it with a rolling hitch to the anchor cable, and adjusting this so that you encourage just one bow to play to the wind - effectively anchoring at an angle.

Alternative - try a bucket streamed astern if there is any current, this will encourage the boat to lie more to the current and less to the wind.

 

[craigsmith]

[ QUOTE ]
I am aware of the problem with sailing boats and this year will try lashing tiller dead ahead and hard over to see what works best but what I want to know is if a small (5m) mobo with a fair amount of windage will have similar tendencies to range about and if so, in the absence of a rudder what do you do to minimise it? The boat (mobo) is cathedral hulled.

TIA

[/ QUOTE ]Lashing the tiller or wheel will help on a sailboat; it obviously keeps the rudder in one position which adds resistance to the stern sweeping sideways, rather than just swinging out of the way.

Mobos do tend to "sail" worse, particularly speed-boats, as they tend to be more light-weight, higher wooded at the bow, and have lower underwater profile so skate about more easily.

I am unsure how a cathedral hull would behave compared to a conventional V. Either the extra geometry will add better sideways resistance and so help, or the hull is essentially a flatter profile than a deeper V would be, and so hinder. /forums/images/graemlins/confused.gif Probably it doesn't make much difference.

On any boat the use of long lengths of rope rode exacerbate the problem, especially stretchy stuff like nylon. An all-chain rode will not let the boat sail as much. Failing this, you could try a rode kellet placed reasonably close to the boat which would dampen things a lot.

 

[KevB]

Lets it swing. If you try and stop yours you will be facing a different direction to the vast majority who do nothing. Mobos and yachts more often than not swing in the same direction.

 

[brianrunyard]

It's not the swinging he wants to stop, it's the ranging about.

 

[aitchw]

OK, so I now have a range of posible courses of action which is great. I can get set up to try those that need a bit of preparation and just try some of the others. I usually have my anchorage to myself so a failed attempt at reducing it isn't going to harm anything except my warp and that's unlikely as I protect it with flexible pipe on the bow roller.

I have for some time considered making a small triangular panel to attach to 'fill in' at the aft end of the boom between boom and topping lift. With the boom locked centrally it should act to keep her head up to the wind but wonder what would happen in wind opposing tide/current with the possibilty of her 'sailing over' the anchor. Any risks I should be aware of?

 

[William_H]

My sail boat lives on a swing mooring and it has a swing up rudder. I tried once to leave it with the rudder up to minimise fouling. The boat was a maniac in wind ranging around costantly. With the rudder down and lashed midships it is far more stable. .... olewill

 

[Ships_Cat]

As Craig has said the best solution on a bigger boat is an all chain cable.

For small MoBos such as the 5m one you mention I have never found myself or seen much problem of them ranging around (I have spent many hours anchored in small MoBo's fishing and we see lots of anchored small MoBos). There again some movement is not something that bothers me. I would not use a second stern anchor for reasons below.

In case not known, and only talking small MoBo's such as you mention here, if wind and seas build avoid any situation that may get you ending up stopped with stern to waves (eg if using second anchor, or recovering anchor over stern) as small MoBos, especially if have heavy outboard, are prone to swamping over the transom.

Similarly, avoid breaking out the anchor over the side unless the anchor is broken out of the bottom and the sea relatively calm as they are also prone to capsizing with the force on the rode, a wave and sudden weight movement in the boat. A good boat, even if partly decked, will always have a safe means to access the bow to retrieve the anchor over it.

John

 

[aitchw]

Thanks for the warning about vulnerability to swamping over the transom. The boat in question does not have much freeboard there and with 35hp main and 5hp auxilliary I will take a very close look at how she sits and make adjustments to weight distribution accordingly.

 

[oldharry]

I once saw a nice little 16 foot drop keeler obviosly with a smooth bottom and everything up, ranging around quite nicely on her mooring during a severe squall - so what was unusual? She was dried out on the mud..... /forums/images/graemlins/crazy.gif

Windspeeds were reported as 60 - 70 kts at the time.