Use of drogue/parachute anchor on Catamaran

[thinwater]

Originally Posted by Don C L

Actually, nothing against these techniques, but you CAN steer a sailboat without a rudder by a combination of the right areas in the headsail and main and with sheeting. It is something fun to experiment with on any boat. On a 65' boat I crewed on that lost its rudder we found that we could maintain and steer fairly well between a close reach and broad reach in about 15 kts of wind. The problem was neither tack took us to a very friendly shore! We tried rigging, well, no, thought about rigging, the spinnaker pole athwartships aft to hold out line and bridle for a drogue steering, but it was just too much boat for that and way too dangerous.

Yup, it was a jammed rudder that got me thinking about this in the first place, and my solution was trim.

However, in the case of a rudder jammed to the side, trim is not going to do it. Also, the seastate matters; a drogue method is FAR more stable in rollers.

Finally, trim only works on certain headings and depends on the boat. Some like it, and some hate it.

There is NO NEED for a spin pole to rig a bridle. The trick is to right the lines near the keel (center of resistance). IMHO, using a pole is pointlessly dangerous and I have no idea why it is suggested.

[Don C L]

Originally Posted by Steady Hand

Good post.

But, I think the line that says "If you deploy a drogue from the bow and the boat is allowed to be thrown back, there is a very good chance you'll damage/break/snap off the rudder" could also include "sea anchor or parachute" in addition to the "drogue."

My point? Any boat thrown backwards on its rudder from a wave from the bow is likely to suffer damage, regardless of what kind of device is hanging off the bow.

Oh sure, absolutely. But if the parachute is properly sized there is supposed to be very little motion. In fact one of the reasons the line and cleats or other fittings need to be so robust is that they may be holding the displacement force, or more, of the boat as it pitches. Oh BTW, the OP should also check out the book by Adlard Coles, "Heavy Weather Sailing." and another btw, nice to see you back Steady!

[Don C L]

Originally Posted by thinwater

Yup, it was a jammed rudder that got me thinking about this in the first place, and my solution was trim.

However, in the case of a rudder jammed to the side, trim is not going to do it. Also, the seastate matters; a drogue method is FAR more stable in rollers.

Finally, trim only works on certain headings and depends on the boat. Some like it, and some hate it.

There is NO NEED for a spin pole to rig a bridle. The trick is to right the lines near the keel (center of resistance). IMHO, using a pole is pointlessly dangerous and I have no idea why it is suggested.

I think the skipper's hope was for more leverage. But it only took a few minutes of trying to LIFT the pole into position that we saw that was a bad idea. I hope I did not come across as advocating that!

[Steadman Uhlich]

Originally Posted by Don C L

Oh sure, absolutely. But if the parachute is properly sized there is supposed to be very little motion. In fact one of the reasons the line and cleats or other fittings need to be so robust is that they may be holding the displacement force, or more, of the boat as it pitches. Oh BTW, the OP should also check out the book by Adlard Coles, "Heavy Weather Sailing." and another btw, nice to see you back Steady!

I agree.

As I recall, Jordan mentions something about that too in one of his articles (seen via the link I posted earlier).

The forces on the GEAR (rope, fittings, deck fittings, deck itself) created by a parachute style sea anchor could be immense, and the size of the sea anchor may need to be very large too. To me, those sound like a forecast for breakage of something at the worst time.

And I think that is shown in anecdotes too, as I recall reading about boats that deployed sea anchors but later their gear snapped and the sea anchor was lost, as the wind and wave forces increased (that is, at the WORST possible time).
------

Don,
I am glad to be back on CF,
and thank you and others for the kind welcoming words too.
back at ya!

[rabbi]

Originally Posted by Steady Hand

The designer, Mr. Jordan, wanted all sailors to have access to the design, so they could make their own. It requires the use of a sewing machine and simple materials and some hours.

Small correction: Many, many hours.

For our previous boat we bought the cones here. Quality was good.

IIRC they were much cheaper back then.

[SVNeko]

Originally Posted by Revelations

We have 2 x Shark Drogue (model L Shark) devices on board our 50' catamaran. Although we have never used these devices in a true high wind situation, we did test them whilst sailing from St. Helena to Brazil.

The drogues were pre-rigged to specially constructed stainless steel attachments bolted onto the aft of the yacht (port and starboard respectively) with 140 meters of rode each. Each rode consisted of 1" x 50 meters Polyester joined with 90 meters of 1/2" Dyneema. The deployment and later retrieval was really easy. We also attached about 2 meters of 1/2" chain behind each drogue to help keep it submerged.

With 18 knots of wind from the aft port quarter, spinnaker flying, the yacht was doing 13 knots. We first deployed one of the Shark Drogues and when the rode was fully extended, the yacht slowed down to an average of 9.4 knots. After a couple of minutes, we deployed the second Shark drogue and the yacht further slowed down to an average of 6.2 knots.

Good anecdote. Thanks. Did you notice any steering effect deploying only one.

[Pieter]

Thanking all input and valued comments. Will sort through all of this info. I am very much a say defensive sailor...as in trying to pick the right weather windows etc.. but.. things can go wrong and so always good to be able to organize and deploy whatever at the moment and conditions i would feel the sensible thing to do .
thanks again for all of yr input.
Best rgds
Pieter
SV Lumina
Lumina Charters – Brazilian Coastal Catamaran Sailing

[FSMike]

From what I have read successful usage of a parachute sea anchor relies on two things: a properly sized sea anchor, and the correct length of line deployed from the bows.

The idea is to have the sea anchor on the crest of it's wave at the same time as the boat is on the crest of the wave it's on. The same applies to the sea anchor and the boat being in the trough of their own respective waves at the same time.
The object is to prevent the sea anchor from being jerked out of it's wave by being out of sync with the boat. That could result in the boat being flung backwards. Adequate extra rode should be provided so as to allow the sea anchor to be adjusted in position if the waves increase in size or distance from the boat.

John Casanova, the inventor of the parachute sea anchor, used the system successfully in severe weather off Cape Horn during the circumnavigation of the Casanova's trimaran "Tortuga Too".
In the story I read about it, he didn't mention much about drogues since he was primarily concerned with the parachute sea anchor.
That's probably why the USCG report referenced by Steadyhand didn't say much about anything other than drogues, mainly Jordan Series Drogues, since it was apparently co-authored by Donald Jordan.

If I was crossing oceans I'd prefer to have one of each on board.

[thinwater]

Regarding drogues...

a. With the exception of the JSD, other drogues cannot generate forces great enough to require special attachment points, In fact, this greatly reduces versatility. Winches and cleats should be fine, and if they are not, they need to be reinforced. Remember that with drogues there is no impact force per se; the drogue gives.

b. You don't steer by attaching to a fixed point. It needs to be a bridle that can be actively adjusted, and the stern quarters are generally not the correct attachment point (OKish for cats, not suitable for monos).

[SVNeko]

Originally Posted by thinwater

Regarding drogues...

a. With the exception of the JSD, other drogues cannot generate forces great enough to require special attachment points, In fact, this greatly reduces versatility. Winches and cleats should be fine, and if they are not, they need to be reinforced. Remember that with drogues there is no impact force per se; the drogue gives.

100%. I even think it applies to the JSD. Your cleats should be able to handle it and if not, fix it.

Originally Posted by thinwater

b. You don't steer by attaching to a fixed point. It needs to be a bridle that can be actively adjusted, and the stern quarters are generally not the correct attachment point (OKish for cats, not suitable for monos).

Is this easier said than done? I haven't deployed our drogue in anger, but in towing another boat I tried to adjust the rode. The tension was way too much to slack it off. It would have run out of my hand. I imagine a drogue might be the same.

[thinwater]

Originally Posted by SVNeko

100%. I even think it applies to the JSD. Your cleats should be able to handle it and if not, fix it.




Is this easier said than done? I haven't deployed our drogue in anger, but in towing another boat I tried to adjust the rode. The tension was way too much to slack it off. It would have run out of my hand. I imagine a drogue might be the same.

Actually, quite simple. I was single handing during most of the testing, up to 35-40 knots. Winches. Just use the spinnaker sheets, but lead them aft instead of forward. Done. That is what you see in the pics (post 12). For my cat, the leads worked without modification and provide enough purchase for any foreseeable wind force.

If the lines are cleated off, things get more complicated. Still, prusic hitches and winches. At some point, you simply head down wind and stop adjusting anyway.

At that point the key risk is pulling the drogue out of a wave and tandem drogues become interesting. Another story. Should be out late summer?

[estarzinger]

Originally Posted by FSMike

The idea is to have the sea anchor on the crest of it's wave at the same time as the boat is on the crest of the wave it's on. The same applies to the sea anchor and the boat being in the trough of their own respective waves at the same time.
The object is to prevent the sea anchor from being jerked out of it's wave by being out of sync with the boat. That could result in the boat being flung backwards. Adequate extra rode should be provided so as to allow the sea anchor to be adjusted in position if the waves increase in size or distance from the boat.

It sounds good in theory but really does not work that way in practice. For two reasons #1 at any given time in a storm there is a spectrum of wave lengths. They are not all the same size nor the same wave length. The range is pretty big. So there is no rode length that will have the boat and para-anchor on the crests at the same time for even half the waves. And #2 in a true storm, you really are not going to want to be up on the bow messing around with the rode as the middle of the low passes and the wind shifts from NW to SW and the wave length changes (because the fetch has just changed). The loads are going to be very high and the motion is going to be bad and there are going to be breaking water sweeping the boat.

In actual practice you put out a whole bunch of rode and leave it out. Hold just a little in reserve for "what if" plan b.

In a simple gale you might well adjust the rode, to move a chafe point, But the wave lengths will still be in a spectrum and not allow one "perfect" rode length, and in a true breaking wave storm you will not want to try to adjust it unless really really really necessary. These sorts of survival conditions are very rare . . . . But they are the ultimate reason most people are carrying these sorts of drag devices.

[Don C L]

Originally Posted by estarzinger

It sounds good in theory but really does not work that way in practice. For two reasons #1 at any given time in a storm there is a spectrum of wave lengths. They are not all the same size nor the same wave length. The range is pretty big. So there is no rode length that will have the boat and para-anchor on the crests at the same time for even half the waves. And #2 in a true storm, you really are not going to want to be up on the bow messing around with the rode as the middle of the low passes and the wind shifts from NW to SW and the wave length changes (because the fetch has just changed). The loads are going to be very high and the motion is going to be bad and there are going to be breaking water sweeping the boat.

In actual practice you put out a whole bunch of rode and leave it out. Hold just a little in reserve for "what if" plan b.

In a simple gale you might well adjust the rode, to move a chafe point, But the wave lengths will still be in a spectrum and not allow one "perfect" rode length, and in a true breaking wave storm you will not want to try to adjust it unless really really really necessary. These sorts of survival conditions are very rare . . . . But they are the ultimate reason most people are carrying these sorts of drag devices.

Approx. how many feet/meters is "whole bunch?"

[maxingout]

Impressive wind and seas in the Video. Thanks for posting it.

I used a drogue once and a parachute sea anchor once on my catamaran when sailing offshore.

Here is what I have learned in my own experience:

SAILING UNI- JOIN TEAM MAXING OUT AS THEY SAIL AROUND THE WORLD ON THEIR PRIVILEGE 39 CATAMARAN - EXIT ONLY

SAILING UNI - JOIN TEAM MAXING OUT AS THEY SAIL AROUND THE WORLD ON THEIR PRIVILEGE 39 CATAMARAN - EXIT ONLY

The first link is about the Abbott Drogue.

The second link is my take on storm management.

[estarzinger]

Originally Posted by Don C L

Approx. how many feet/meters is "whole bunch?"

Lets start with a little science

Deep water ocean waves in storm conditions will have a period in the 10 - 16 second range (we have excellent data on this from all the ocean buoys). The accident investigation team for the low speed chase incident used 13 seconds as 'typical' (large waves were the 'cause' of the incident).

Wave length (in deep water) can be derived from period: L = g T^2 / 2 pi. Using this formula 13 seconds corresponds to 260m wave length. This will be affected by water depth and ocean currents, but in any case it is longer than most people think, longer that most all rodes people are carrying.

You can put aside the theoretical answer of '2 wave lengths back' and move on to the more practical trade-off . . . which is between two objectives:

#1 you do still hope that when you are in the breaking portion of the wave, your para-anchor will be behind the white water in more stable water. This implies that as you are on the leading edge of the wave, you hope the para-anchor will be some where near the trailing last 1/3 of the wave. This means about 175m/600' of rode.

vs

#2 you do not want too much slack to develop nor too much 'spring back' to occur as you pass out of the breaking portion and the loads come off the rode. This is perhaps the most dangerous portion of the cycle - because if big slack develops AND another breaker hits you right then, you could be turned sideways and rolled before the rode takes up again. There is no math to help here - it is a 'feel' and experience thing. Somewhat lower stretch rope (either dacron or bigger nylon) is probably better than somewhat higher stretch to reduce spring back. Experience might suggest about 1/3 of wave length, or say 100m/300' in our prototype 13 sec wave, as the area that reduces slack while still keeping the para-anchor mostly out of the breaker when you are in in.

So . . . bottom line . . . . . the most expert people I know suggest carrying 600' (remember those 16 second waves will be 400m long! - but yes 600' is a **** load of line) and then trying to put out enough to balance the above two factors (slack developing vs keeping para-anchor in different portion of waves) in the particular conditions you are in - and that might mean starting with as little as 175' in quite short waves or 300' in more typical ocean waves or 450' in longish waves (like southern ocean long fetch). I personally would error of putting out more than less, because it is going to be highly loaded and difficult to adjust once the **** hits the fan and it is worse to have the para-anchor in the same white water as the boat than to have a bit of slack develop between hits (neither is great but that is your trade-off).

There is a theory that if you sink the para-anchor deeper you can both keep it out of the white water and keep it closer/shorter rode thus getting less slack (eg the best of both worlds) but that theory runs into two 'science problems' In that these big breaking waves actually churn up quite a depth of water and because of the loads involved the para-anchor really really wants to come to/is pulled to the surface. So, in practice this is pretty much impossible to pull off.