Heaving to for power catamaran

[mcarthur]

Are there any experiences people have for heaving to on a power catamaran (as against a sailing cat)?
For example, keep engines on and hold position via autopilot while resting (remember powered vessels often have different autopilots than sailing) versus putting out a drogue front or rear (like JSD)?
Is it better to keep some way on using the engines rather than just hold position?
This is apart from the usual when "do it when you personally feel the need to", or the angles to the weather that a catamaran has different to a monohull.

[StuM]

Strictly speaking, heaving too is a sailing manoeuvre. In a powerboat, it depends on what sort of propulsion you have. Do you have rudder(s) or steerable drives? Can your autopilot control engine thrusts independently?

[Dsanduril]

Well, speaking from the sailing perspective it sounds like you're asking about "heaving-to" vs. "fore-reaching". They're similar maneuvers, but fore-reaching keeps on minimal way to windward. In general I personally find fore-reaching to be more comfortable and to offer better control and more consistent angle to the seas. Zero experience in a power cat, but that's our experience in a sailing cat, so I'd start with trying to keep 1-2 knots at somewhere between zero and 45 degrees angle to seas. A power vessel does offer some wind/sea angle options that simply aren't available to us rag boats.

[Simi 60]

I take it this is a well offshore on passage situation?

Parachute anchor off the bow.
Turn engines off
Sleep.

[Paul Howard]

I have hove-to and lay ahull with sailing catamarans as well as hove-to with 55 to 65ft heavy displacement trawler yachts.
In my catamaran I try to lie with the longest diagnol presented to the waves. Depends on your beam, windage forward and windage aft, etc., but with engine(s) at fast idle, helm steering into the waves/wind, about 45degrees from the wind, gusts will push your bows down wind and the rudders and engines will bring you back to lying as previous to the gusts. Your boat will be side-slipping through the waves and fore-reaching.

It is something you will have to try to work out, as each boat is different.

[Slainte1]

if conditions warrant it a series drogue from the stern is the safest option and the most comfortable

[Shrew]

No, there is no way to 'heave to' in a power vessel. You can deploy a sea anchor (parachute) to hold your bow into the waves. You could deploy a drogue, which would be holding your stern into the waves.

If you have enough fuel to make long passages, people typically remain underway on autopilot and rotate shifts.

[Paul Howard]

Originally Posted by Slainte1

if conditions warrant it a series drogue from the stern is the safest option and the most comfortable

A series drogue from the stern is for vessels in high winds and large seas to be underway down wind, to prevent run-away surfing, severe broaching and pitchpoling. It is good for sailing vessels who fly a storm jib in conjunction with the series drogue, maintaining steerage. It must remain along the water surface and not sink, as if that happens, the stern might not rise to a large overtaking wave and be swamped.

If you want to simply stop the boat, parking it on the water without any way on, a parachute sea anchor from the bows works well. I have used one on my catamaran to great effect in high winds and waves. The motion is gentle, the waves tend to break at the parachute so the bows lift to the large swell but there is no slamming and spray comes onboard but no heavy water.
Heaving to as I described in an earlier post, is also a viable alternative.

Handling all the gear for a sea anchor or a drogue is a chore. For ordinary gales at sea, up to 60knot gusts, sustained winds no more than 50knots, heaving to or lying ahull would be my choice.

[RaymondR]

If you have a plotter connected to the auto pilot and the autopilot will reliably steer the boat at very slow speeds setting a route on the plotter and having the engines idle the boat along the track to a way point would probably be the safest action. Half a knot to a way point five miles away gives you a ten hour nap.

[CassidyNZ]

Acknowledging up front that I have no experience with cats, power or sail, I have had the good fortune to survive some serious conditions at sea. With that as a background I believe that simply stopping a power cat in serious conditions (lying a-hull) would place the vessel at considerable risk.

Even hove-to on my sailing boat saw us smacked on the beam by very large swells with broken seas at the top, knocking us down and almost rolling us. One occasion was with me on deck in daylight motoring into the seas. The other was lying a-hull in the middle of the night.

The day-time knockdown was a wall of white water probably 10 feet deep rolling onto the boat, taking us to within a whisker of a full roll-over. Even with my limited understanding of catamarans, I believe that event would have rolled a cat, even a big one, over which as we know is a relatively terminal condition.

So in my opinion, if I was in charge of a big motor cat in serious conditions I would have someone at the helm at all times using the power and manouverability to avoid breaking seas. Lying a-hull would simply not be and option. And even the smallest risk of the boat surfing would need to be strictly avoided so any motoring would be into the seas.

But that is just my uninformed personal opinion.

[Simi 60]

Originally Posted by CassidyNZ

Acknowledging up front that I have no experience with cats, power or sail, I have had the good fortune to survive some serious conditions at sea. With that as a background I believe that simply stopping a power cat in serious conditions (lying a-hull) would place the vessel at considerable risk.

:

Tank testing by the late great Loch Crowther has been done showing a small wave can roll a monohull whereas a considerably larger wave had little effect on a catamaran

. Note: reference source, Lock Crowther Designs

"This work (tank testing at Southampton Univ) has indicated that the well designed catamaran is remarkably safe in breaking waves up to considerable height, even when beam on, we were unable to capsize a power catamaran yacht in the largest wave which could be generated. This corresponded to a 52' wave for a catamaran of 40' beam. Scaling this down to a typical 24' beam cruising cat means she should be O.K. in a 31' breaking beam sea. An equivalent size mono-hull power boat was easily capsized by a 25' breaking sea, and in tests with conventional yachts after the Fastnet disaster, it was found that a 40' mono-hull yacht could capsized in a 12' breaking sea"

http://www.cruisersforum.com/forums/...ml#post2185465

[CassidyNZ]

Originally Posted by Simi 60

Tank testing by the late great Loch Crowther has been done showing a small wave can roll a monohull whereas a considerably larger wave had little effect on a catamaran

“This corresponded to a 52' wave for a catamaran of 40' beam. Scaling this down to a typical 24' beam cruising cat means she should be O.K. in a 31' breaking beam sea.”

Of course you (and the study quoted) are probably correct but I’m reasonably confident that the university were unable to generate a 52 foot wave in their test tank (note statement “corresponded to”), a catamaran with 40 foot beam is a very big catamaran and the extrapolation of this kind of data is often far from linear, i.e. scaling this kind of data may not yield the practical effects one would expect. Lots of speculation here.

Few things out at sea in really bad weather conform to linear predictions so whilst the study may give cat owners a sense of confidence, I just know I wouldn’t want to be lying a-hull on a cat in 50 foot breaking seas.

But that’s probably just me.

[Ungvar]

I have spent quite a bit of time station keeping in big commercial power cats. Just hold the bow into the wind with slow revs on and bursts of power. I kind of doubt most autopilots would be up to the job in most conditions that would warrant it, but no harm in trying. You could slow down to the minimum speed auto will keep you on course and just creep ahead.

A warp or drogue off the stern might work, but its a bit of farting around.

You could also try lying a hull.

I think my first choice would be keep on trucking in auto at minimum steerage way.

[Simi 60]

Originally Posted by CassidyNZ

Of course you (and the study quoted) are probably correct but I’m reasonably confident that the university were unable to generate a 52 foot wave in their test tank (note statement “corresponded to”), a catamaran with 40 foot beam is a very big catamaran and the extrapolation of this kind of data is often far from linear, i.e. scaling this kind of data may not yield the practical effects one would expect. Lots of speculation here.

Few things out at sea in really bad weather conform to linear predictions so whilst the study may give cat owners a sense of confidence, I just know I wouldn’t want to be lying a-hull on a cat in 50 foot breaking seas.

But that’s probably just me.

Perhaps you should enlighten yourself by reading about the Queens birthday storm off of NZ.

Monohull's rolled and pitchpolled
Multihulls found drifting relatively unscathed weeks latter.

https://pangolin.co.nz/queens-birthday-storm/

Multihull Dynamics, Inc. - News Article

[CassidyNZ]

Originally Posted by Simi 60

Perhaps you should enlighten yourself by reading about the Queens birthday storm off of NZ.

Monohull's rolled and pitchpolled
Multihulls found drifting relatively unscathed weeks latter.

https://pangolin.co.nz/queens-birthday-storm/

Multihull Dynamics, Inc. - News Article

Actually I have read the report of the Queen’s Birthday storm and in fact one of our sailing friends (recently deceased) was on one of the boats in that storm so we have been regaled in the first person, as it were.

As for multihulls being relatively unscathed, I clipped the following from the Pangolin report:

“At one time some yacht and personal gear was spotted, but a pharmaceutical label identified it as belonging to the catamaran HEART LIGHT. HEART LIGHT had broken up a day or so earlier after the crew or 3 had been taken aboard the New Zealand fishing boat SAN TE MARU 18.”

This may of course be incorrect as in the other report it is claimed that a Heart Light was rammed until she sank. I’m not sufficiently motivated to research it any further. I consider myself already suitably enlightened.