Parachute sea anchor

[westernman]

here's a video that illustrates where i'd be wanting some extra assistance from a drag device!

Interesting video. That sea looks rather nasty and confused. And there seems to be almost no wind.

I personally have never been in anything resembling that.

The poor boat is being pushed around by the waves and is not really making any significant head way. A drogue over the stern is not going to make much difference as the boat is hardly moving. Without the boat moving the drogue is not going to exert any force.

He needs more sail - but not the main as the it will be crashing around and will break something pretty quickly.

So what would you guys do if you were on that boat in the video (apart from throwing up)?

 

[VO5]

so you keep saying....

but WHY does the seabrake exert a downward force where the JSD doesn't?
Surely if the angle is the same on the line basic schoolboy maths means that the direction of pull on the stern is identical with either device?

and WHY does the seabrake impart directional stability where the JSD doesn't?
directional stability is surely a function of ensuring the pull on the stern is maintained?... where I could see a strong argument for a JSD achieving just this by constantly having part of the device in operation, whereas the seabrake will lose pull when their is no load on it, thus allowing the stern to wander

You need to explain the reason for your statements rather than just repeat them over and over again.

The Seabrake exerts a downward force because once the drogue is deployed
it sinks, fast. As the Drogue is filled with water, it still remains submerged.
When it is towed it still remains submerged.
As the tow effort is increased it swells, but still remains submerged, the difference being that it adjusts to the tow, instead of not adjusting, which is why ordinary cones, tyres, and simple weights break surface.

THe Seabrake does not spin at all. It does not wander underwater because the pull is direct from the brace throught the towing line and the chain to the drogue. Therefore the Seabrake assembly does not and cannot snake.

Does this satisfy your query ?

 

[bbg]

As an observer to this thread, I was inspired to check out the Sea Brake website. I can't find that the manufacturer makes any of the following claims:
- that the cones swell when extra pull is exerted (and, frankly, I don't see how this can be the case unless they are made of elastic material, or partially collapse when there is less pull)
- that the Seabrake is "well dug in" (the website says that, properly deployed, it will be "just below the surface - 3-5 feet")
- any reference to keeping the stern down, or the importance of doing so

 

[VO5]

so you keep saying....

but WHY does the seabrake exert a downward force where the JSD doesn't?
Surely if the angle is the same on the line basic schoolboy maths means that the direction of pull on the stern is identical with either device?

and WHY does the seabrake impart directional stability where the JSD doesn't?
directional stability is surely a function of ensuring the pull on the stern is maintained?... where I could see a strong argument for a JSD achieving just this by constantly having part of the device in operation, whereas the seabrake will lose pull when their is no load on it, thus allowing the stern to wander

You need to explain the reason for your statements rather than just repeat them over and over again.

When the Seabrake is deployed, the weight of chain pulls it down vertically to start, submerging the drogue.
When the tow is exerted the drogue remains submerged and the drogue swells but does not spin or wander.
When the tow is increased the drogue swells.
The angle of slope of the tow may increase with speed, but basically the drogue remains embedded.
As the line from the brace to the chain and drogue becomes taut the pull on both cleats at the stern remains equal. Therefore the tension on the stern in a straight line remains taut, but taut by degrees as the Seabrake is made to swell and revert to its original shape. It does not spin. And it does not snake as the pull is loaded at the end, instead of being divided along its length.

Directional stability is maintained because the pull on the drogue being constant, the stern is kept square to the sea. But the icing on the cake is that tjhis drogue is able to swell when more pull is exerted on it, thus increasing the drag. At the same time, the stern is kept down.

The stern being kept down is crucial to maintaining directional stability.

If the stern is not kept down, the following sea will get under the gap between the rim of the stern where it meets the underside and shift it about.
This is not desireable as it leads to yawing and the risk of broaching.

As the benefits are contained as a result of a cluster of features, just explaining each separately does not give you a reality.

It is not possible to explain all of them, all together, all at once.

Therefore you would have to experience its use at sea in bad weather in order to make a valid comparison against past experiences using other devices.

I have that experience.

You would have to have experience of it to allow you to arrive at conclusions based on your experiential evidence yourself as it is evident that the written word here cannot seem to convey the concept sufficiently realistically to satisfy you, try as I might.

 

[VO5]

so you keep saying....

but WHY does the seabrake exert a downward force where the JSD doesn't?
Surely if the angle is the same on the line basic schoolboy maths means that the direction of pull on the stern is identical with either device?

and WHY does the seabrake impart directional stability where the JSD doesn't?
directional stability is surely a function of ensuring the pull on the stern is maintained?... where I could see a strong argument for a JSD achieving just this by constantly having part of the device in operation, whereas the seabrake will lose pull when their is no load on it, thus allowing the stern to wander

You need to explain the reason for your statements rather than just repeat them over and over again.

Ok, I must reply in two posts because long ones keep getting disconnected.


Part 1...Directional Stability.

In order to achieve directional stability the pull on the stern must be even, this is the key.
As the Seabrake adjusts to the pull by swelling when the pull increases the tow line remains relatively taut.
Additionally the drogue is kept submerged by the weight of the chain, which is pre calculated for the size of drogue, length of tow, vessels's tonnage, LOA, etc.,
The chain length is calculated to guarantee the drogue remains submerged always.
Additionally this drogue does not spin or wander because of its unique design and construction.

 

[VO5]

Part 2.

Downward force is a component of directional stability because two things are needed, one is to keep the stern down, the other is to keep the drogue submergedand the line taut.

The line is kept taut by the pull exerted on the drogue as the boat moves through the water. The drogue is kept submerged by the weight of chain.
The weight of chain, as an afterthought can be increased by shackling on extra chain.

The question is that the effort involved is to pull one single drogue in a straight line between the brace and the drogue itself.

The effort is not subdivided between many cones, just one very big and efficient self adjusting double bucket drogue at the end.

 

[VO5]

As an observer to this thread, I was inspired to check out the Sea Brake website. I can't find that the manufacturer makes any of the following claims:
- that the cones swell when extra pull is exerted (and, frankly, I don't see how this can be the case unless they are made of elastic material, or partially collapse when there is less pull)
- that the Seabrake is "well dug in" (the website says that, properly deployed, it will be "just below the surface - 3-5 feet")
- any reference to keeping the stern down, or the importance of doing so

The last time I looked at their website was about 4 years ago.

At that time they had a short video explaining the concept. In another section there was a table of details for the sizes, length of tow, shackle sizes etc., and various other applications.

I suggest you try again.

 

[webcraft]

As an observer to this thread, I was inspired to check out the Sea Brake website. I can't find that the manufacturer makes any of the following claims:
- that the cones swell when extra pull is exerted (and, frankly, I don't see how this can be the case unless they are made of elastic material, or partially collapse when there is less pull)
- that the Seabrake is "well dug in" (the website says that, properly deployed, it will be "just below the surface - 3-5 feet")
- any reference to keeping the stern down, or the importance of doing so

How dare you interrupt VO5's stream of consciousness!

- W

 

[VO5]

How dare you interrupt VO5's stream of consciousness!

- W

Webby, everyone is free to do what they like, of course.
But I was introduced to this Seabrake concept by an old friend, a Master Mariner, who told me all about it and his experiences with his boat, over dinner.
I agreed to try it.
I have tested it several times in angry seas.
I must report as I find.
My findings are that this new type of drogue is way ahead of anything else.
That is why I am willing to pass on my experience for the benefit of others.

 

[bbg]

In order to achieve directional stability the pull on the stern must be even, this is the key.

Their website says that, in extreme weather, the Seabrake should be streamed from one quarter or the other - not evenly.

As the Seabrake adjusts to the pull by swelling when the pull increases the tow line remains relatively taut.

You keep saying it "swells" - how? Which dimension changes?

Additionally the drogue is kept submerged by the weight of the chain, which is pre calculated for the size of drogue, length of tow, vessels's tonnage, LOA, etc.,
The chain length is calculated to guarantee the drogue remains submerged always.

But what happens if the whole part of the wave that the drogue is in, starts to break?

You suggested I "look again" at the website. I have, and can't find any support for your claims of this device. I'm not saying it's good or bad, just that what you are saying is not what the manufacturer says.

 

[bbg]

My findings are that this new type of drogue is way ahead of anything else.
That is why I am willing to pass on my experience for the benefit of others.

Have you tried the Jordan Series Drogue (or any other series drogue)? If not, your conclusion that the Seabrake is "way ahead" is speculation.
I welcome anyone who comes onto the forum and gives the rest of us the benefit of their experience. By all means share with us your experience of the Seabrake.
But - to take a page out of your book - if you want to express an opinion on the relative merits of Seabrake vs. series drogue, go out there and put out a series drogue in an F10+, then come back and tell us how they both performed.

 

[crisjones]

Having read most of this thread I must say that I believe VO5's explanations to be a misleading - perhaps he is a politician . I am not disputing that he has real life experience of using a Sea Brake drogue in adverse conditions and furthermore more this experience proves the Sea Brake to be effective. This experience does not show that any other design of drogue is inferior.

The idea of holding the stern down seems to be confusing quite a few people - the tow line to the drogue device is likely to be about 10 - 20 degrees below the horizontal so the downward force component is fairly small the tow line would need to be at nearer 45 degrees below horizontal to give a significant downward component - all basic physics. When the Sea Brake and chain and rode are deployed the weight of chain may well cause the drogue and line to sink to quite a depth, but as soon as everything is taut and the boat is pulling the drogue at 3 or 4 knots the drogue will rise towards the surface so the line is much nearer the horizontal. The weight of chain may well keep it down somewhat but not too much unless you have significant weight of chain. The Sea Brake website states the device is normally 3 -5 feet below the surface and this will equate to the tow line being less than 5 deg below the horizontal - more confirmation that there is minimal downward force component.

What is actually happening is that the drogue is exerting a significant braking effect on the stern of the boat, hence stopping the boat accelerating down a wave and allowing the wave to pass under the boat. This braking effect probably does give the impression of pulling the stern down, but it is not due to a downward force, merely the drag on the back of the boat.

In order to prevent a boat surfing down a wave or allowing the stern to be pushed sideways as a wave passes under the boat you need enough drag on the stern of the boat. What is enough drag ?? This depends on the size and weight of the boat, the sea conditions, the wind speed, steepness of waves etc. If you have a drogue that is not big enough to provide sufficient drag then the boat may get pushed sideways or may surf down the wave face - this is irrispective of the type of drogue being towed. If it is not big enough it will not work properly to keep the boat in line to the waves.

The Sea Brake is a different design to other cone type drogues and alot of the drag is caused by the water being forced out of the gaps between the two sections, this creates large amounts of turbulence and hence drag. It may well create more drag for a given size than other designs (it probably does), however I can see nothing in the design that allows it to expand or contract to vary the drag.

The variation in drag force is related to speed through the water, the faster you go the more force the drag device exerts. Try towing a bucket through the water, very easy at very low speeds, increasingly difficult as speed increases. This is true for every drag device regardless of design - higher speed equals higher drag force. As a boat tries to accelarate down a wave any drag device will increase the braking force being applied to the stern. If the drag device can provide sufficient braking force to keep the stern from slewing sideways or accelerating down the wave then it is doing the job it is there for - again the device must be big enough for the boat and conditions.

The attachment of the tow rope to the boat via a bridle is common to all drag devices - if you use a bridle with the attachment points on the boat as far apart as possible then you will have more directional stability than a single point attachment. This is true for all drogues.

In conclusion - if you have a drag device that provides sufficient braking force for the boat and conditions and it is properly attached to the boat via a widely spread bridle then you have what you need to help you stay safe in storm conditions.

This can be provided by any drag device - Sea Brake, JSD, Standard Drogue, long warps, car tyres - whatever. Provided it gives suffiecient braking force it will do the job. Modern drogue designs are made to give maximum drag for a given size - this is why a drogue is more efficient than towing warps - it simply gives more drag. The design of modern boats means that they need more drag than old, heavy, long keel boats in order to keep their speed down to safe limits in storms.

The Sea Brake may well be a better design than some others, and may well give more braking force for a given size but it does not do anything different to any other design - it simply gives a braking force to the tow line. If you tow a JSD that gives the same braking force as a Sea Brake the boat will behave the same in similar conditions.

VO5 may never have had a Sea Brake pull out of the wave face but it is a risk when you only have one element in the water, the chain may help prevent it but the risk still exists. The 3.5 x boat length tow rope gives a length of 140ft for a 40ft boat - as wavelength increases you have the likelihood that the boat is on the crest of one wave and the drogue is on the face of the following wave, there is a real possibilty of the drogue coming out of the wave face and all drag being lost. Most drogue manufacturers say the drogue line should be 1.5 times the wavelength so the drogue is in the trough behind the following wave to minimise the chances of pull out. Unfortunately in long duration storms the waves build and the wavelength increases, it is very difficult to vary the line length when using a bridle so it is always best to put out as much line as you have. The JSD overcomes this by having many cones over a long length so it will never come out completely.

I am not saying one device is better than another, I am just trying to explain in simple terms how drag devices work and what you need to achieve maximum safety. There will always be conditions where one device may appear to be better than another, but a change in conditions may well mean a different design works better.

But above all you must have a device that produces enough drag for the boat and conditions, and it must be securely attached to the boat.

 

[bbg]

crisjones,
thanks for taking the effort to write exactly what I was thinking.

 

[VO5]

Have you tried the Jordan Series Drogue (or any other series drogue)? If not, your conclusion that the Seabrake is "way ahead" is speculation.
I welcome anyone who comes onto the forum and gives the rest of us the benefit of their experience. By all means share with us your experience of the Seabrake.
But - to take a page out of your book - if you want to express an opinion on the relative merits of Seabrake vs. series drogue, go out there and put out a series drogue in an F10+, then come back and tell us how they both performed.

Yes I have. Never again.
I have also tried buckets with and without holes, rubber tyres and ordinary cone shaped drogues.
All of them have gone in the bin, in case you want to know.
If you want to seek a 10 just to stream a series drogue, you go ahead, not me.

 

[bbg]

Yes I have. Never again.

Can you expand? Circumstance, conditions, and what didn't you like? Was it a Jordan Series Drogue, or something else?
I'd be interested to know why not, because many other people extol their virtues.

If you want to seek a 10 just to stream a series drogue, you go ahead, not me.

But that is what you were suggesting people do, before they were allowed to express an opinion on this thread.

 

[VO5]

Having read most of this thread I must say that I believe VO5's explanations to be a misleading - perhaps he is a politician . I am not disputing that he has real life experience of using a Sea Brake drogue in adverse conditions and furthermore more this experience proves the Sea Brake to be effective. This experience does not show that any other design of drogue is inferior.

The idea of holding the stern down seems to be confusing quite a few people - the tow line to the drogue device is likely to be about 10 - 20 degrees below the horizontal so the downward force component is fairly small the tow line would need to be at nearer 45 degrees below horizontal to give a significant downward component - all basic physics. When the Sea Brake and chain and rode are deployed the weight of chain may well cause the drogue and line to sink to quite a depth, but as soon as everything is taut and the boat is pulling the drogue at 3 or 4 knots the drogue will rise towards the surface so the line is much nearer the horizontal. The weight of chain may well keep it down somewhat but not too much unless you have significant weight of chain. The Sea Brake website states the device is normally 3 -5 feet below the surface and this will equate to the tow line being less than 5 deg below the horizontal - more confirmation that there is minimal downward force component.

What is actually happening is that the drogue is exerting a significant braking effect on the stern of the boat, hence stopping the boat accelerating down a wave and allowing the wave to pass under the boat. This braking effect probably does give the impression of pulling the stern down, but it is not due to a downward force, merely the drag on the back of the boat.

In order to prevent a boat surfing down a wave or allowing the stern to be pushed sideways as a wave passes under the boat you need enough drag on the stern of the boat. What is enough drag ?? This depends on the size and weight of the boat, the sea conditions, the wind speed, steepness of waves etc. If you have a drogue that is not big enough to provide sufficient drag then the boat may get pushed sideways or may surf down the wave face - this is irrispective of the type of drogue being towed. If it is not big enough it will not work properly to keep the boat in line to the waves.

The Sea Brake is a different design to other cone type drogues and alot of the drag is caused by the water being forced out of the gaps between the two sections, this creates large amounts of turbulence and hence drag. It may well create more drag for a given size than other designs (it probably does), however I can see nothing in the design that allows it to expand or contract to vary the drag.

The variation in drag force is related to speed through the water, the faster you go the more force the drag device exerts. Try towing a bucket through the water, very easy at very low speeds, increasingly difficult as speed increases. This is true for every drag device regardless of design - higher speed equals higher drag force. As a boat tries to accelarate down a wave any drag device will increase the braking force being applied to the stern. If the drag device can provide sufficient braking force to keep the stern from slewing sideways or accelerating down the wave then it is doing the job it is there for - again the device must be big enough for the boat and conditions.

The attachment of the tow rope to the boat via a bridle is common to all drag devices - if you use a bridle with the attachment points on the boat as far apart as possible then you will have more directional stability than a single point attachment. This is true for all drogues.

In conclusion - if you have a drag device that provides sufficient braking force for the boat and conditions and it is properly attached to the boat via a widely spread bridle then you have what you need to help you stay safe in storm conditions.

This can be provided by any drag device - Sea Brake, JSD, Standard Drogue, long warps, car tyres - whatever. Provided it gives suffiecient braking force it will do the job. Modern drogue designs are made to give maximum drag for a given size - this is why a drogue is more efficient than towing warps - it simply gives more drag. The design of modern boats means that they need more drag than old, heavy, long keel boats in order to keep their speed down to safe limits in storms.

The Sea Brake may well be a better design than some others, and may well give more braking force for a given size but it does not do anything different to any other design - it simply gives a braking force to the tow line. If you tow a JSD that gives the same braking force as a Sea Brake the boat will behave the same in similar conditions.

VO5 may never have had a Sea Brake pull out of the wave face but it is a risk when you only have one element in the water, the chain may help prevent it but the risk still exists. The 3.5 x boat length tow rope gives a length of 140ft for a 40ft boat - as wavelength increases you have the likelihood that the boat is on the crest of one wave and the drogue is on the face of the following wave, there is a real possibilty of the drogue coming out of the wave face and all drag being lost. Most drogue manufacturers say the drogue line should be 1.5 times the wavelength so the drogue is in the trough behind the following wave to minimise the chances of pull out. Unfortunately in long duration storms the waves build and the wavelength increases, it is very difficult to vary the line length when using a bridle so it is always best to put out as much line as you have. The JSD overcomes this by having many cones over a long length so it will never come out completely.

I am not saying one device is better than another, I am just trying to explain in simple terms how drag devices work and what you need to achieve maximum safety. There will always be conditions where one device may appear to be better than another, but a change in conditions may well mean a different design works better.

But above all you must have a device that produces enough drag for the boat and conditions, and it must be securely attached to the boat.

Misleading you say...

Aren't you funny ?

Then you go and contradict yourself throughout your post.

Incredible. It seems that no amount of explanation will suffice.

 

[VO5]

Can you expand? Circumstance, conditions, and what didn't you like? Was it a Jordan Series Drogue, or something else?
I'd be interested to know why not, because many other people extol their virtues.


But that is what you were suggesting people do, before they were allowed to express an opinion on this thread.

Because a catamaran has two hulls, not one.
What is more, it has two sterns and two bows.
All four have to be in the water for the vessel to have directional stability because all you need is for one of the bows to dig deeper and the opposite stern to lift higher and you potenrially have a disaster imminent with a large following sea.

Simple.

Now a vessel with one keel and one bow and one stern is a different proposition altogether.

How many times has something have to be explained as clearly as possible for iit to be understood I wonder.

 

[crisjones]

Misleading you say...

Aren't you funny ?

Then you go and contradict yourself throughout your post.

Incredible. It seems that no amount of explanation will suffice.

I am now convinced VO5 must be a politician because he seems to be sure that he is always right!!!!

All I was trying to do was explain a few things that quite a few people seemed to be struggling with - the main one being your concept of "holding the stern down". It is quite obvious that a drogue of any sort does not hold the stern down - even Sea Brake accept this with their statement that the Sea Brake is only 3-5ft deep.

As I said, a drogue supplies sufficient braking force to keep the boat directionally stable, so preventing the stern being pushed across or preventing the boat accelerating. The drogue does this by applying a braking force to the stern of the boat in an almost horizontal plane - not vertical.

I can accept that when a wave passes under the boat and the boat is just at the crest, the boat will almost certainly be pointing steeply downwards because of the angle of the wave face. At this point the drogue will be pulling the stern of the boat back into the wave, hence giving the appearance of "pulling the stern down", however the pull from the drogue is still predominantly horizontal, it is the fact that the boat is NOT horizontal that is changing the angle of pull relative to the boat.

I was not trying to belittle your experience, perhaps it would have been better to say your explanations were not as clear as they might have been - this should have been obvious from the number of queries raised about your explanations. Your explanations may seem to be as clear as a bell to you - that does not mean they have the same clarity to everyone else.

 

[bbg]

Because a catamaran has two hulls, not one.
What is more, it has two sterns and two bows.
All four have to be in the water for the vessel to have directional stability because all you need is for one of the bows to dig deeper and the opposite stern to lift higher and you potenrially have a disaster imminent with a large following sea.

Simple.

Now a vessel with one keel and one bow and one stern is a different proposition altogether.

How many times has something have to be explained as clearly as possible for iit to be understood I wonder.

VO5, you haven't answered a single question that I asked. I asked them because I am interested. Perhaps I can be more clear:
- when did you try a Jordan Series Drogue?
- what was the boat, specifically (make, model, length etc or a description)?
- what were the wind and sea conditions?
- how was the JSD deployed? (length of warp, from which part or parts of the boat etc)?
- why was it deployed (what problem were you trying to address? e.g. going too fast and risk of pitchpoling? yawing and broaching?)?
- how did the boat respond to the deployment of the JSD?
- what specific problem did the JSD have that convinced you not to use one again (e.g. didn't slow the boat enough, kept pulling out of wave faces?)?

I'm genuinely interested.

 

[westernman]

Misleading you say...

Aren't you funny ?

Then you go and contradict yourself throughout your post.

Incredible. It seems that no amount of explanation will suffice.

I saw nothing contradictory in Crisjones' post. It all seemed clear and logical to me. Perhaps you would like to point out those contradictions to the rest of us who did not manage to spot them?