Parachute sea anchor

[crisjones]

None of this is about willy waving, it is about common sense.

Furthermore it is about not expending unnecssary energy.

As the Seabrake dogue has several functions, one of these is to reduce rolling at an anchorage by hanging it from the end of the boomed out boom, so one sunny calm day in the open Atlantic in the Azores High, we decided to carry out a practical experiment...

Instead of deploying it from the stern we decided to deploy it from the bow, as if it were a para anchor. We brought down all sail...

The result was startling.

The water was very clear and we could look all the way down the tow and could see the drogue clearly.

What happened was this:

The drogue and chain fell vertically. To our surprise it began to be pulled by the current at an angle underneath the boat. There was no wind.

So we pulled it in. As we did so a very big fish followed it to the surface and swam away before it broke surface.

We came to the conclusion that streaming from the bow is pointless.

We then deployed it from the stern. The current began to tow it backwards gently. As there was no wind and the sea was dead flat, it didn't matter.

But we reasoned that if the wind arrived, ther drogue was already in the correct place to be efficient.

It is so obvious I cannot understand this persistence in clinging to outmoded ideas.

I cannot see much "common sense" in this post from VO5, perhaps I am not looking at it from the right angle???

Quite what is going to be proved by deploying a Sea Brake in flat calm, windless conditions, I do not know. The device is designed to be used as a braking device in bad conditions.

VO5 states that the current pulled the drogue under the boat when it was streamed from the bow and the current pulled the drogue behind the boat when it was streamed from the stern. What would have happened if the boat had been turned through 180 degrees and the experiment repeated??? Almost certainly the results would have been the exact opposite. Quite clearly if the only force acting on the drogue is the current, then the drogue will always be pulled in the direction of the current, regardless of where it is attached to the boat.

As we have already said - a drogue is designed be attached to the stern of a boat and is put there to slow the boat down and maintain directional stability. A drogue should never be deployed from the bows. A parachute is designed to anchor the boat to the sea, ie to effectively STOP the boat, as such it should be deployed from the bows in the same way as you normally deploy a steel anchor and warp.

VO5 is certainly entitled to his opinions based on his own experience, however he does need to accept that his conclusions are not neccesarily correct for anyone else. There is no one solution to managing storm conditions on a small boat. Some of his posts even seem to be in direct contradiction to the information posted on the Sea Brake website - I would suggest that the manufacturer of the device is much better informed about his product than one single user (even if he is a satisfied user)

 

[VO5]

That is not what is said though. It's being implied, clearly from the VO5 text, that a device from the bow, can be pulled by the current in a direction towards the boat which is not favorable if you wish to have the device streaming out and away forward from the bow. Whether or not the observation in calm weather weather is valid or not for sever weather can not be determined just from the text.

The implication though is that hanging from a device where the current may pull it in a direction that you dont want, in heavy weather, is important and may be a reason for some descriptions of snatch loads on parachute anchors contributing to their ineffectivenss. Conversley a moving vessel with a device trailing from the stern will tend to maintain that device directly behind.

Later in his text it can be implied that this current carrying away the device astern is favourable for an early deployment in preparation for heavy weather of a stern bridled device.

This current effect could also be a reason for a bridle on a bow deployed device being used to align a vessel at an angle to the sea anchor. The bridle for a stern deployed device can do much the same if the bridle arm length can be adjusted.

I have read V05's points and I cant help feeling that he is being crucified because of his particular flamboyant and intransigent style of expression. So what, its a dumb ass forum of mixed ability contributors, not the definitive source of world expert opinion on seafaring skills.

I have gleaned, and continue to glean, a lot of information from this thread. Comparing this with Heavy Weather Sailing and Storm Tactics, amongst others, will be a worthwhile investment.

Exactly, precisely,

Here is another point to consider:~

If in open water with a flat or flattish sea with no wind or very little wind, does it matter to be drifting backwards ? Does it matter in which direction the drift is ? Even does the rate of drift matter ?

What does matter is that the vessel is put in a state of instant readiness with minimum exertion should conditions deteriorate.

Surely to have a vessel additionally put into a state of instant readiness as a by product, must be a major component of prudent seamanship.

To have a vessel put into a state of complication through obstinate persistence by slavishly adhering to the contents of a textbook that does not include the latest and most efficient technology available must be imprudent seamanship, I respectfully submit.

 

[robertj]

This post has without a doubt been excellent! The differing of opinions certainly provokes healthy debate and for me, a fantastic learning curve to, not take everything as gospil.

 

[VO5]

I cannot see much "common sense" in this post from VO5, perhaps I am not looking at it from the right angle???

Quite what is going to be proved by deploying a Sea Brake in flat calm, windless conditions, I do not know. The device is designed to be used as a braking device in bad conditions.

VO5 states that the current pulled the drogue under the boat when it was streamed from the bow and the current pulled the drogue behind the boat when it was streamed from the stern. What would have happened if the boat had been turned through 180 degrees and the experiment repeated??? Almost certainly the results would have been the exact opposite. Quite clearly if the only force acting on the drogue is the current, then the drogue will always be pulled in the direction of the current, regardless of where it is attached to the boat.

As we have already said - a drogue is designed be attached to the stern of a boat and is put there to slow the boat down and maintain directional stability. A drogue should never be deployed from the bows. A parachute is designed to anchor the boat to the sea, ie to effectively STOP the boat, as such it should be deployed from the bows in the same way as you normally deploy a steel anchor and warp.

VO5 is certainly entitled to his opinions based on his own experience, however he does need to accept that his conclusions are not neccesarily correct for anyone else. There is no one solution to managing storm conditions on a small boat. Some of his posts even seem to be in direct contradiction to the information posted on the Sea Brake website - I would suggest that the manufacturer of the device is much better informed about his product than one single user (even if he is a satisfied user)

I omitted in my post to mention that we were so puzzled that we tried it.
We tried all angles on the rudder. No response. The current still dragged the towline under the boat. My fear was possible damage to the impeller.

Then we started the engine and turned her round on the opposite heading. The heading reverted to the original heading and the towline went under the boat again.

We now streamed the drogue from the stern. The towline now streamed away from the boat and with te rudder midships went astern in a straight course.

Variations in rudder angle had no effect whatsoever.

What did have an effect however, was alternate alteration of brace lengths.

 

[VO5]

As a further comment, which I think you will find interesting, when the drogue was streamed from the bow, the towline was first of all deployed by placing it singly over the bow roller.

As the boat refused to pay off at all there was no point we thought of using the brace (by securing to the bow cleats and through the fairleads).

When we turned to boat round, we did this. The result was the same.
Fearing damage to the impeller, we brought it in again and reverted to the original idea. This did not work either.

The boat swung round again and began to go backwards with the towline again under it.

It was then that we decided to stream from the stern, with the results posted above.

 

[VO5]

As one last comment, because I have used it in angry seas situations 8 times, the Seabrake was never again streamed from the bow.

In every case, it was streamed from the stern with its brace.

And in every case it streamed astern without any problems, and the moment it bit, the boat settled noticeably and kept its heading in front of the seas that followed.

Recovery was very easy in every case. Took just minutes. The towline was winched aboard using the sheet self tailing winches with not much effort, even with the vessel still making some way in the water, as the boat tows the Seabrake, and not the other way round.

 

[crisjones]

I omitted in my post to mention that we were so puzzled that we tried it.
We tried all angles on the rudder. No response. The current still dragged the towline under the boat. My fear was possible damage to the impeller.

Then we started the engine and turned her round on the opposite heading. The heading reverted to the original heading and the towline went under the boat again.

We now streamed the drogue from the stern. The towline now streamed away from the boat and with te rudder midships went astern in a straight course.

Variations in rudder angle had no effect whatsoever.

What did have an effect however, was alternate alteration of brace lengths.

VO5, thank you for posting this extra info that was ommitted originally, however I must still respectfully suggest that experimentation in calm windless conditions proves very little about how things will work in storm conditions.

When wind and waves build up the forces acting on the boat itself become the dominant factor, not any underlying current (unless such current is faster than the boat is moving). If a boat is stern to the wind and waves, ie running before, then a drogue streamed off the stern will do the job it is designed for. It would not work streamed off the bow.

If the boat is head into wind and waves then the forces will be trying to blow the boat backwards and hence a parachute off the bows will hold the boat in this attitude as it is designed to do. Should you stream a drogue off the bows in this situation (NOT recommended) then the fact that the boat is being pushed back by wind and waves will ensure that the drogue streams out in front of the boat, not underneath as your experiment in calm conditions showed. I accept that the boat will not maintian this attitude with a drogue off the bows, simply because the drogue is not big enough to hold the bows into wind, very soon the bows will get blown off and she will broach or capsize. Even if the drogue does hold the boat head to wind she will still be allowed to go backwards quickly enough to risk major rudder damage.

In your other post you seem to sugest it is prudent seamanship to have drogue streamed ready in anticipation of worsening weather, even though you are sitting in calm conditions - why would you want to do this???

Surely you would not want a drogue deployed until conditions start exceeding F7 or F8, why spoil a lovely F5 sailing wind by towing a drogue? Perhaps you meant to say that the drogue should be fully rigged and ready in the cockpit - that is indeed prudent seamanship, but that is not what your post suggests.

And in your final post you say that you would never again deploy the Sea Brake off the bows - in that you are quite correct, but you should never have expected it to do any good off the bows. It is not designed to be streamed from the bows, no drogue device should be deployed from the bows, ever.

A parachute is the only device designed for deployment off the bows and this MUST be big enough to ANCHOR the boat to the seas.

 

[JayBee]

And in your final post you say that you would never again deploy the Sea Brake off the bows - in that you are quite correct, but you should never have expected it to do any good off the bows. It is not designed to be streamed from the bows, no drogue device should be deployed from the bows, ever.

Regardless of the strongly held and forcefully expressed opinions here, there is a certain amount of selective reading of the Seabrake manufacturer's info on their website.

They state quite clearly that the Seabrake can be deployed as a sea anchor off the bow and claim that it has "twice the drag of a conventional sea anchor............".

 

[JayBee]

A parachute is the only device designed for deployment off the bows and this MUST be big enough to ANCHOR the boat to the seas.

This is certainly at odds with the Pardeys' use of a sea anchor, which uses the orientation and downwind drift of the boat to create a "slick" in which the advancing seas do not break.

 

[crisjones]

Jaybee,

You are quite right about the suggestion on the Sea Brake website, I am not sure it is a good idea to stream it off the bow.

Because of the design of the Sea Brake it will always move through the water, regardless of where it is attached to the boat. If I am going to deploy something off the bows I want it to effectively stop the boat or at least slow it down to a very slow rate of drift such that there is no risk of rudder damage. I am sure nearly everyone would agree that you cannot afford to risk rudder damage.

Sea Brake claim it provides twice the drag of a conventional sea anchor - yet do not quantify this in any way. The Sea Brake may well provide twice the drag of an "identically" sized sea anchor - however a parachute needs to much bigger than a drogue for the same size boat.

Sea Brake recommend a GPL30 for our boat, 30" diameter, The recommended para anchor is 18 feet in diameter. So even if you double the Sea Brake actual diameter you still only get an effective 5 feet when used as a sea anchor. I think you can see that the Sea Brake cannot possibly provide the same holding force as a 18 ft parachute.

Maybe if you have a vastly oversized Sea Brake it will work as well as a parachute, but if you have a drogue sized sea brake it will not be man enough to work safely as a sea anchor.

However we are all entitled to consider all the advice, experience and recommendations available to us before we make a decision on what storm management devices to carry and deploy. I believe you should carry a purpose designed drogue AND a purpose designed para anchor if you are going offshore sailing - do not expect one product to do both jobs. You should practice using them in average to rough conditions whenever you can to see how they perform and then when you really need either of them you have a much better chance of making the right decision and safely surviving any storms you encounter.

 

[Boo2]

I accept that the boat will not maintian this attitude with a drogue off the bows, simply because the drogue is not big enough to hold the bows into wind, very soon the bows will get blown off and she will broach or capsize.

My understanding is that it does not much matter how big the drogue/sea anchor is, it is the underwater shape of a modern hull which prevents it lying head to wind. An example of this is the "sailing at anchor" effect of a boat on the hook in a harbour in strong winds.

Boo2

 

[crisjones]

Boo2,

You are correct about boats sailing at anchor and I had overlooked that, mainly because we sail a catamaran and once you have a bridle from hulls to anchor chain then any "sailing" is pretty much eliminated.

Not sure how significant this "sailing" would be in storm conditions - my observations of anchored boats indicate that the sailing effect is very much reduced as the wind increases to gale force, I would expect much the same to be true when lying to a sea anchor in a storm.

Once again, though, this is another factor that skippers must consider when making their decisions - you need to know how your boat behaves when anchored (or sea anchored) in strong to gale force winds. Unfortunately only actual experience in your own boat can tell you this unequivocally, no text book, website or other skipper can do this for you.

 

[VO5]

VO5, thank you for posting this extra info that was ommitted originally, however I must still respectfully suggest that experimentation in calm windless conditions proves very little about how things will work in storm conditions.

When wind and waves build up the forces acting on the boat itself become the dominant factor, not any underlying current (unless such current is faster than the boat is moving). If a boat is stern to the wind and waves, ie running before, then a drogue streamed off the stern will do the job it is designed for. It would not work streamed off the bow.

If the boat is head into wind and waves then the forces will be trying to blow the boat backwards and hence a parachute off the bows will hold the boat in this attitude as it is designed to do. Should you stream a drogue off the bows in this situation (NOT recommended) then the fact that the boat is being pushed back by wind and waves will ensure that the drogue streams out in front of the boat, not underneath as your experiment in calm conditions showed. I accept that the boat will not maintian this attitude with a drogue off the bows, simply because the drogue is not big enough to hold the bows into wind, very soon the bows will get blown off and she will broach or capsize. Even if the drogue does hold the boat head to wind she will still be allowed to go backwards quickly enough to risk major rudder damage.

In your other post you seem to sugest it is prudent seamanship to have drogue streamed ready in anticipation of worsening weather, even though you are sitting in calm conditions - why would you want to do this???Surely you would not want a drogue deployed until conditions start exceeding F7 or F8, why spoil a lovely F5 sailing wind by towing a drogue? Perhaps you meant to say that the drogue should be fully rigged and ready in the cockpit - that is indeed prudent seamanship, but that is not what your post suggests.

And in your final post you say that you would never again deploy the Sea Brake off the bows - in that you are quite correct, but you should never have expected it to do any good off the bows. It is not designed to be streamed from the bows, no drogue device should be deployed from the bows, ever.

A parachute is the only device designed for deployment off the bows and this MUST be big enough to ANCHOR the boat to the seas.

Because not every expoanse of water is like the English Channel and the Western Approaches.

In other expanses you can experience sudden unexpected developments in minutes, such as line squalls developing out of nowhere, microbursts and waterspouts.

What I illustrated simply shows a willingness and an ability to quickly put in place a state of instant readiness.

I will give you three examples one of them tied up alongside, one in an anchorage and one in the open ocean.

The first occured tied up in a boatyard in the USA....Not a cloud in the sky. Sun blazing. Boom tent over the cockpit. But the barometer told a different story. It began to drop, fast.

I had a very obstinate crew member on board who refused to take down the boom tent, instead he went off to get a can of coke from the bar 150 yards away.

No sooner was he on his way back with his trophy than in seconds swirling purple clouds gathered quickly and it started to rain very heavily. Still on the pontoon, and 30 yards away suddenly thunder and lightning developed and the wind began to gather. By the time he was on board the gusts were 45 knots. To teach him a lesson, I left him to struggle with the boom tent in gusts now of 50 - 55 knots. The wind speed hit a shade under 80. It was all over in 20 minutes.

In an anchorage at night in Mudhole, the sky was completely clear. But again the barometer began to fall. In no time at all a line squall came over accompanied by thunder and lightning overhead, raindrops like marbles and powerful gusts. The ground was soft mud. The anchor was well dug in so the drag was minimal. Again, this was over in less than 1/2 hour and the sky cleared completely exposing a velvet sky in which the Milky Way was clearly visible.

The third example occured 80 miles north of Bermuda.

Along the horizon to the south very far away there was a thunderstorm, so far that the flashes were visble but the thunder could not be heard.

Ahead were inoffensive little cumulus clouds.

But again, the barometer began to fall very sharply, 5 millibars in as many seconds.

In no time at all the weather turned filthy. We went through strong turbulence accompanied by strong gusts and heavy rain. Again, this was very brief. The ensign frightened itself and had wrapped itself round and round the flagstaff like a barber pole.

I do not agree with your last sentence.

Another reason against para anchors is the huge strain they exert not only on the deck hardware but on the towline itself. Parting of the towline is not unknown through fraying, beyond protections taken against chafe.

 

[westernman]

Assuming we have a sea anchor being used as a sea anchor, and not as an aid to get the boat to heave to properly (which is my understanding of the Pardey's technique), then I assume there is a wind strength (nothing to do with waves) at which its size is no longer adequate to keep the boat from moving backwards too fast.

My understanding is that potentially this is what happened to the catamaran which flipped with a sea anchor deployed asymmetrically off the bows which I cited in a earlier post in this thread. The boat ended up almost broadside onto the waves, with enough wind to heel the boat considerably - the sea anchor streaming off the windward bow and the boat drifting side ways and backwards out of control. Then a wave came along a finished it off.

My feeling is that when this happens, you are in a pretty dire situation - you can't do much except may be get the drogue prepared and cut away the sea anchor to run away before the wind.

Fortunately I never been in winds anything close to where this would happen in my boat. She will reliably heave to in a F10 - the most I have been out in is in a F9. But things can always turn very nasty down here very quickly. Two years ago we had winds of 183km/h in the marina! Waves are obviously not the same size as in the atlantic or pacific, but they can very steep and confused (rather as in the video some one posted earlier of the yacht in a nasty sea with little wind).

So I will offer the opinion (never having been caught out that badly), that conditions can end up being too windy for a given size of both a drogue and a sea anchor. If you are lying a sea anchor which is too small for the conditions, you are doomed. If the drogue is too small, you still have a bit of margin to steer to avoid disaster and time to react and find some more stuff to stream from the stern.

 

[JayBee]

....Fortunately I never been in winds anything close to where this would happen in my boat. She will reliably heave to in a F10 - the most I have been out in is in a F9.

I hope this isn't nit picking, but if a F9 is the most you have experienced, how can you be sure that your boat will reliably heave to in a F10?

Just for interest, I have had a look at some numbers....

The mid wind speed in a F9 is about 50 knots and in a F10 it is about 59 knots. Doesn't seem like much of a difference, but the force of the wind varies as the square of the speed and this represents about a 40% increase in force.

 

[westernman]

I hope this isn't nit picking, but if a F9 is the most you have experienced, how can you be sure that your boat will reliably heave to in a F10?

Just for interest, I have had a look at some numbers....

The mid wind speed in a F9 is about 50 knots and in a F10 it is about 59 knots. Doesn't seem like much of a difference, but the force of the wind varies as the square of the speed and this represents about a 40% increase in force.

The previous owner assures me he spent two days hove to in a F10 in the Atlantic.

I agree, there is a hell of a difference between a F9 and a F10.

 

[Woodlouse]

Just for interest, I have had a look at some numbers....

The mid wind speed in a F9 is about 50 knots and in a F10 it is about 59 knots. Doesn't seem like much of a difference, but the force of the wind varies as the square of the speed and this represents about a 40% increase in force.

What you are saying is right, but I think your numbers are out slightly. I've always understood a F9 to begin at 40 knots and a F10 to take over at 50. 59 knots is approaching an 11.

Having said that the Beaufort scale is more to do with wind and wave conditions combined than just simple windspeeds.

 

[JayBee]

What you are saying is right, but I think your numbers are out slightly. I've always understood a F9 to begin at 40 knots and a F10 to take over at 50. 59 knots is approaching an 11.

Well spotted.

I was using mph instead of knots, but it doesn't alter the outcome of the calculation - still a 40% increase in wind force.

 

[Sybarite]

http://www.youtube.com/watch?v=FwlCARfnO5s&feature=channel

See from 3min55 onwards.

http://www.seriesdrogue.com/vs/