Multihull storm tactics?

[Mick C]

Originally Posted by Kettlewell

Why do you denigrate parachute sea anchors when you have no experience with them? I have used one numerous times on a 32-foot cruising catamaran. I carry one on my 38-foot monohull, though I have never used it on the mono. In my experience, the parachute brought our cat under control in Force 9-10 offshore conditions, allowing us to leave the boat to tend herself while we rested. The parachute has also been used several times to steady the boat while conducting repairs to the steering system offshore. I believe a parachute sea anchor, properly deployed, is a safe method of dealing with heavy weather on a multihull. In every case I have read of where the sea anchor has failed, it was improperly deployed. The most common scenario is not letting out enough scope (300-400 feet minimum in a Force 9-10).

In the spirit of learning what is the pros and cons of serial Vs parachute drouges? Why would one go for one over the other in a catamaran?

[danielamartindm]

Originally Posted by Quiet Riot 420

I think Cat man do and other that criticize the vertical windows on a Lagoon, are missing a very important point. When a breaking wave does come crashing down on the the bow of a cat. it most likely will not be coming down on the boat at right angles to the vertical windows, more likely in will come crashing down at right angles (the most force) to the slanted back windows, therfore making them take to full force of the wave and possibly blow out. So, under the right conditions your slanted back windows are just as vulnerble to a breaking wave as any other cat!

Fair Sailing _(\_
Quiet Riot 420

I think the unpredictability of wave strikes makes the point of window angulation moot; but vertical windows definitely decrease greenhouse heating of the bridge deck interior- a not insignificant thing, and I personally like the esthetics of vertical windows.

[Just Another Sa]

Originally Posted by Mick C

In the spirit of learning what is the pros and cons of serial Vs parachute drouges? Why would one go for one over the other in a catamaran?

A parachute sea anchor stops your boat with the water, and therefore pulls you with any current. You practically speaking don't drift downwind towards any land with any wind, no matter how strong it might be. It does matter what the phase of the waves is at the location of parachute relative to the phase of the waves where the boat is. A long stretchy rode obviously helps, but the effect is still there.
It gives some challenges when you want it up again to continue sailing, as you can't just shorten the rode until you can pull it up, because it still has full force and with short scope it will pull your bows down with big rollers still there whenever your boat is at the wave crest and the parachute is at the trough. You could try using a separate retrieval line, or tie a small buoy to the rode and try using a dinghy to go around to the other side of it, but that's not safe either with still a high seastate. Some claim a retrieval line can become messy during use, I don't know if that is due to misuse or not.
Using too short rode certainly is misuse, and it will cause problems, possibly dangerous.


A series drogue does not stop you with the water, it drifts with slow speed. For a longer time period you will have to make sure you still have some searoom left to drift. It's very easy to pull off when you want to continue sailing by moving the boat towards it, as the amount of drogues continue to diminish so does the force it can provide. The drogues close to your boat have relative small force and thus can't pull your bows down. The ones further off will not pull vertically due to their location. Since it drifts it won't hold your boat as closely to the wind direction as a parachute will. It allows your boat rotate more and take wave at an angle, less comfortable, but still safe for a cat. A series drogue also allows adjusting the force generated and thus drifting speed, if you just want to limit surfing rather than stop the boat. In other words, you can even continue sailing with reduced speed, like 5...7 knots if you want to, just connect the drogue (or rather a part of it as you still need rode) to the sterns instead of bows. It will also help to steer the boat, by adjusting the bridle connection to the boat.
Changing rode & bridle connection from transom to bows might not be easy or even safe during a heavy storm. Backing up to pull up the rode & drogue is most likely undoable with a high seastate.

[Just Another Sa]

Originally Posted by danielamartindm

I think the unpredictability of wave strikes makes the point of window angulation moot; but vertical windows definitely decrease greenhouse heating of the bridge deck interior- a not insignificant thing, and I personally like the esthetics of vertical windows.

You need less area for the windows for the same visibility if they are vertical or close to that. As a result less weight for the same strength to stand up against wave strikes. Vertical windows do have more windage reducing upwind performance.

[DavefromNZ]

A sea anchor is attached to the bow a drogue to the stern. Once set neither will ever be changed to the other end in a storm. You will not reverse using engines in a storm and the dingy will not be used to recover a sea anchor or drogue.

[Mr B]

A drogue attached to my stern in big waves would sink my boat,
Maximum freeboard on my transom is about one metre,
Many tons of water on my transom steps and a cockpit full of water from following waves, I dont think I would last long,

[Just Another Sa]

Originally Posted by DavefromNZ

A sea anchor is attached to the bow a drogue to the stern. Once set neither will ever be changed to the other end in a storm. You will not reverse using engines in a storm and the dingy will not be used to recover a sea anchor or drogue.

You will not even try to recover either parachute or drogue during a storm, but after it has passed. At such time, there is typically still a heavy seastate.
If you had used a long series drogue from the stern to slow you as much as possible, not a short one with long rode just to reduce max speed peaks down, you will not be able to recover it without backing against the waves unless you change attachment to the bows first and then power forwards against the waves and towards the drogue. You can not just pull it in easily as the forces needed are massive and so is the work needed to do that. Engine and propulsion system can easily provide the work needed.

Ps, there is no law against using a long series drogue from the bows during storm. If you do not have a parachute, it's also the wise thing to do if searoom downwind is limited. It's also not dependent on phase of the wave, and thus no adjustment is needed to match the rode length to multiple of wavelength, unlike in the case of a parachute.

[Just Another Sa]

Originally Posted by Mr B

A drogue attached to my stern in big waves would sink my boat,
Maximum freeboard on my transom is about one metre,
Many tons of water on my transom steps and a cockpit full of water from following waves, I dont think I would last long,

That depends on the usage/size of the drogue. If it's dimensioned and used to prevent boat speeds exceeding for example 10 knots rather than stop you from drifting, it'll probably be fine and not sink your boat. At least as long as the waves are not breaking. The intent in that case is to prevent stuffing the bows under and pitchpoling after surfing down waves.

[Mr B]

Originally Posted by Just Another Sa

That depends on the usage/size of the drogue. If it's dimensioned and used to prevent boat speeds exceeding for example 10 knots rather than stop you from drifting, it'll probably be fine and not sink your boat. At least as long as the waves are not breaking. The intent in that case is to prevent stuffing the bows under and pitchpoling after surfing down waves.

I gave that a lot of thought after I was standing up to my knees in water in a full cockpit from following waves, Twice,
I can keep my boat under 10 knots by going sideways across the waves,
I never surf down the waves either, Ever,
Then it all depends on what some people call big waves,

The only time Im drifting, Is in an ocean that has no wind, dead calm and I havent turned the motor on,
I just like the serenity of being in an empty ocean then, Its very relaxing,


As for pitch poling in my boat, Thats wish full thinking, Its just not going to happen,
Over sideways, Yep, Thats a good possibility if I do some thing stupid,
But I also need some very big waves for that to happen again too,
Learnt my lesson on that one, too, hahahaha
Some people are still advising others to keep the Leeside board down in big seas, When its a real, No No,
Thats a very good tripping hazard if the board digs in and dont slip,

Ive sailed thru some medium sized waves, up to 20 footers, But I have decided I wont use either drogues or parachutes,
Neither are feasible or practicable, for me,
Running before a storm for me is a nice easy ride,
But this is for my specific boat, 34 foot cat, I have proven it for me,
What other people do, Well thats up to them at the time,

[longjonsilver]

Steve and Linda Dashew's books now available free online

http://www.setsail.com/PracticalSeamanship.pdf

http://www.setsail.com/OCE_bookdocs.zip

enjoy,

jon

[UFO]

Originally Posted by Mr B

Some people are still advising others to keep the Leeside board down in big seas, When its a real, No No,
Thats a very good tripping hazard if the board digs in and dont slip,

I was under the impression that the Lee Board should be fully up and the windward board partially to fully down depending on conditions and sailing angle to wind/swell? Is that correct?

[44'cruisingcat]

Originally Posted by UFO

I was under the impression that the Lee Board should be fully up and the windward board partially to fully down depending on conditions and sailing angle to wind/swell? Is that correct?

If it's survival conditions, both boards up.

I rarely have any board down unless I'm sailing upwind. I hear the claims that the autopilot works better with board down on broad reaches or whatever, but it hasn't made any difference on my boat.

And if you're in surfing conditions, adding drag forwards would be anything but beneficial.

[Mr B]

Originally Posted by 44'cruisingcat

If it's survival conditions, both boards up.

I rarely have any board down unless I'm sailing upwind. I hear the claims that the autopilot works better with board down on broad reaches or whatever, but it hasn't made any difference on my boat.

And if you're in surfing conditions, adding drag forwards would be anything but beneficial.

Do you have dagger boards or centre boards,
I have centre boards,
Mine work better with the windward side down and the Lee up,
I learnt my lesson with the Leeside board down, It dug in and I nearly went over sideways, I wont be doing that again,

With no boards down the Autopilot works very hard to keep it in a straight line,
Mine slithers all over the place with the boards up,
I only have a two foot draught fully loaded and Im only 14 feet wide,
So its entirely a different boat,
Yours is a lot wider, So the seaway would be different on yours,
Your draught is deeper too,

[mark_morwood]

Originally Posted by Just Another Sa

...

Ps, there is no law against using a long series drogue from the bows during storm. If you do not have a parachute, it's also the wise thing to do if searoom downwind is limited. It's also not dependent on phase of the wave, and thus no adjustment is needed to match the rode length to multiple of wavelength, unlike in the case of a parachute.

No law against it, but all the recommendations I have read are to not use a drogue off the bow. The reason being a drogue is designed to slow you down, not stop you, so with a drogue off the bows, even a long Jordan Series Drogue, you may be going 3 or 4 knots in reverse in storm seas, which is unlikely to end well. Rudders in particular are not designed to handle that, and you are also likely to have the bow blow off on one tack or another, leaving you exposed on one side or other to the seas.

All the cases I have read of, were parachute off the bows, or drogue off the stern. They are very different things with very different use cases and their characteristics and are in no way directly interchangeable.

[Just Another Sa]

Originally Posted by mark_morwood

No law against it, but all the recommendations I have read are to not use a drogue off the bow. The reason being a drogue is designed to slow you down, not stop you, so with a drogue off the bows, even a long Jordan Series Drogue, you may be going 3 or 4 knots in reverse in storm seas, which is unlikely to end well. Rudders in particular are not designed to handle that, and you are also likely to have the bow blow off on one tack or another, leaving you exposed on one side or other to the seas.

All the cases I have read of, were parachute off the bows, or drogue off the stern. They are very different things with very different use cases and their characteristics and are in no way directly interchangeable.

You got everything else correct (mostly repeating what I wrote in my post #183), except just one thing.
The rudders are designed for a certain load, not for a certain speed. The rudders can develop more load when going forwards than backwards (if at the same speed), because the max lift coefficient is significantly higher when going forwards, just like most airfoils or hydrofoils. Therefore they can tolerate a little faster speed going backwards than going forwards (in order to have the same load). Since everything is symmetric structurally, the direction of drag force or lift force relative to the boat makes no difference whatsoever.

As long as we are not talking about storm or survival conditions, you might claim that you can limit lift coefficient to something less than max when going forwards, reducing the loads when going forwards, but that would no matter be possible when conditions really become tough, resulting different but still maximum lift coefficient for both directions at some point in time anyway.