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Thread: Drogue or Sea Anchor? What and When?

  1. #21
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    Default Re: Drogue or Sea Anchor? What and When?

    I think I can explain this another way .....
    First consider a simple wave without a breaking crest and your boat is anchored by the parachute anchor. In this situation the parachute can be assumed to be anchored at a particular position relative to the long. and lat..
    Initial case : boat in trough = no load, no tension in the tether
    As the crest of the wave approaches the boat ... the boat climbs the leeward side of the wave towards the crest. Gravity is trying to send it down into the crest. The tension in the tether increases.
    As crest passes under the boat, the tension reduces until such point as the boat is helped by gravity towards the parachute anchor and the rode slackens.
    By the time the trough is again under the boat the boat is moving toward the parachute anchor. It shouldn't ever reach it as the rode should be long enough to be at least two wavelengths to windward, and the wind resistance should keep it back.
    The danger, even in this simplified case of a simple wave, is that there is enough slack in the rode that the bows are pushed around by the next crest so the boat is beam on. This does happen .... and the Dashew's book refers to it.

    Now add a breaking crest. By definition the crest is traveling at the speed of the wave and has broken away from the mass, falling towards the boat with the help of gravity. It is this that is the most damaging.

    Take the other situation where the boat is travelling with the wave system but at half the speed of the wave system, preferably oblique to the waves:
    The frequency of encounter ... the time it takes for the crest to reach the boat .... has halved, giving twice the time to steer away from the damaging breaking crests and, since the boat is now heading in the same direction of the crests any forces imparted by the crest will be much reduced .... as the velocity of encounter is reduced by half. The energy will be reduced significantly ......in part because of the kinetic energy = 1/2 mv^2.

    Don't ask me to quantify it ..... it's way too complicated, but you must surely see now what I am getting at.

    If the boat is travelling just a little slower that the wave there is much more opportunity to steer clear of the damaging crests. If one does hit the transom, it will tend to push the boat forward ...... impact loads are much reduced.

  2. #22
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    Default Re: Drogue or Sea Anchor? What and When?

    Ok, I agree with the initial part of your post about the breaking wave that has broken away from the rest of the wave etc. I agree with the tensioning and slacking of the parachute rode BUT we are talking about a bridle on any proper parachute set up on a multihull that helps takes care of that tensioning and de-tensioning. Even the Pardy's in their Storm Tactics video have a bridle on a monohull. So I do not see how its possible with a proper set up for the boat to broach. There is a book I have on the boat that is the detailed record of very single use of a parachute ever reordered and not one mentions this issue in practice.

    So what exactly are you suggesting you do to minimise this tension/de-tensioning? Slack off to a still as the crest approaches and motor down the trough? It seems to me no matter what speed you adopt forward you make matters worse, not better.

    As regarding motoring at angles in rough conditions... yes I have often done it in rough weather but not in survival conditions .... even then you are adding the kinetic energy of there boat to the energy of anything hitting you.
    You are still better off not having any energy from the boat providing your set up can avoid broaching which is why the para anchor comes in.

    The parachute anchor was developed after the second world war using proper parachutes. It was used by North Atlantic fishermen to stop at sea and rest in even very bad storms they could not run from.

    Stopping in the form of heaving to has always been considered to have 'switched off the sea' suddenly things change to a much more peaceful situation. However in the bigger storms this may not be enough ... hence as far as I can see and going on all the experiences of those hundred or so written accounts of parachute use, the parachute is the way to go.

    The dashews were on a mono - were they using a bridle like the Pardy's?
    Safe Sailing
    Paul
    Blog: www.suliere.com

  3. #23
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    Default Re: Drogue or Sea Anchor? What and When?

    Responses in italic below.

    Quote Originally Posted by ForumAdmin View Post
    Ok, I agree with the initial part of your post about the breaking wave that has broken away from the rest of the wave etc. I agree with the tensioning and slacking of the parachute rode BUT we are talking about a bridle on any proper parachute set up on a multihull that helps takes care of that tensioning and de-tensioning. Even the Pardy's in their Storm Tactics video have a bridle on a monohull. So I do not see how its possible with a proper set up for the boat to broach. There is a book I have on the boat that is the detailed record of very single use of a parachute ever reordered and not one mentions this issue in practice.

    The book you refer to is probably the Drag Device Database by Victor Shane ...... I have always believed that the DDDB was biased. Some of the cases that you say do not exist are detailed in Dashew's Surviving the Storm ... By the way I have asked Paratech to state if Victor Shane had any financial interest in their business. I am awaiting there response.

    If you have a bridle connected to the bows of a cat, you either have to ensure that it is absolutely chafe free or inspect it regularly for chafe. This is not something that I would undertake in true survival conditions.

    If the bridal is taken aft so that it can be adjusted ..... as is recommended by many informed advocates of PA's you still have a connection at the bow that either needs to be checked or is guaranteed to be chafe free. Any breaking of the rode will bring the boat to at least beam on.

    The nylon rode ..... usually three strand ..... undergoes up to 30% stretch before failure. The stretching process induces heat into the rode .... partially offset by cooling by the water .... but the rode will chafe in itself. Three strand also has a habit of cobbling.



    So what exactly are you suggesting you do to minimise this tension/de-tensioning? Slack off to a still as the crest approaches and motor down the trough? It seems to me no matter what speed you adopt forward you make matters worse, not better.

    I am saying that I would prefer to run before the weather than be tied in place to a parachute anchor.

    I don't believe an engine ... or two ... would make any significant difference to the tensions in the rodes or the forces on the boat in these extreme conditions.

    I can well believe that lying at an angle by either using an asymmetric bridle may reduce the acceleration/deceleration ... and hence reduce the forces on the boat and the stretching of the rode


    As regarding motoring at angles in rough conditions... yes I have often done it in rough weather but not in survival conditions .... even then you are adding the kinetic energy of there boat to the energy of anything hitting you.
    You are still better off not having any energy from the boat providing your set up can avoid broaching which is why the para anchor comes in.

    I tend to sail if there is wind ..... and adjust my sailing speed and hence forces on my boat by varying how much sail I have up and in what direction I sail.

    Assuming that I have no choice but to head into extreme weather, I would certainly consider using some sort of drag device ..... but as a last resort only. The trouble with heading into the waves is that it becomes almost impossible to get out of the way of any breaking waves as the encounter frequency is much increased. Certainly a large drogue or parachute anchor would make getting out of the way impossible ..... although of we are told to expect the dangerous waves to collapse due to the protection of the parachute and the wake (I find this to be very questionable when in a mixed developed sea). I cannot conceive a situation where I would put myself and my boat in this vulnerable position though


    The parachute anchor was developed after the second world war using proper parachutes. It was used by North Atlantic fishermen to stop at sea and rest in even very bad storms they could not run from.

    Stopping in the form of heaving to has always been considered to have 'switched off the sea' suddenly things change to a much more peaceful situation. However in the bigger storms this may not be enough ... hence as far as I can see and going on all the experiences of those hundred or so written accounts of parachute use, the parachute is the way to go.

    The dashews were on a mono - were they using a bridle like the Pardy's?

    You have raised various questions about the Dashew's .... and yet you state that you have read Surviving the Storm. Reading it again and understanding it should answer your questions.
    Last edited by tradewindsailor; 13th September 2013 at 11:34 PM. Reason: trying bold to denote my reply

  4. #24
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    Default Re: Drogue or Sea Anchor? What and When?

    We are talking about extreme conditions. I have been in very rough seas and adjusted the speed and angle of the boat dodging the worst waves etc BUT I have never been in such conditions requiring the use of a parachute anchor. Hence I have read and read all I can on it - I did this some years ago.

    I will re-read Dashew and come back to you on this.

    Members of this forum have used a parachute and spoken highly of it.

    I just do not agree with your logic so can only read more and get back to you on it.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  5. #25
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    Default Re: Drogue or Sea Anchor? What and When?

    I've just had a reply from Para Tech Engineering.

    I quote in full :

    Your question was in regard to FINANCIAL interest by Victor and is direst - a little too direct which is why I needed some clarification. His company - PARA ANCHORS INTERNATIONAL was a dealer in our products and when he decided to go full time into writing he sold the name to us which was mainly our purchase of "good will" associsted with the name. He and I do stay in touch.

    Don Whilldin, President
    PARA-TECH ENGINEERING

    End quote.

    ........

  6. #26
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    Default Re: Drogue or Sea Anchor? What and When?

    Interesting although it does not change the logic that stopping the boat is the least energy absorbing solution for the boat.

    What it does show is that there person who wrote the book had an undeclared interest and so his writing has to be treated with more caution ...... I hope we can agree on that?
    Safe Sailing
    Paul
    Blog: www.suliere.com

  7. #27
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    Default Re: Drogue or Sea Anchor? What and When?

    I agree with the caution on the DDDB.

    I do not believe that stopping the boat with a parachute anchor minimises the loads on the boat. It certainly does not.

    Heading down wind at just under the speed of the waves reduces the loads on the boat ..... but this needs active control in order to dodge any threatening breaking crests. A breaking crest could knock the boat broadside and cause a capsize, especially with fixed keel multis that have more of a resistance to being pushed sideways.

    I must repeat I have never sailed in any conditions that I would consider to be 'survival conditions'. So far my sailing tactics have been developed at a comfortable rate from experience and reading as much as I can from informed sources .... which does actually include the DDDB, the Dashews, and many others. I don't intend to find a storm to prove my theories either.

    Let us please remember that not a year goes by without people and boats being lost at sea. The knowledge of how they were lost is usually lost with them. It is VERY important that we gain as much knowledge as we can from whatever source and open it to informed criticism. Thank you for the sounding board.

  8. #28
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    Default Re: Drogue or Sea Anchor? What and When?

    I have also never sailed in such conditions that would require a parachute.

    It is VERY important that we gain as much knowledge as we can from whatever source and open it to informed criticism.
    That we agree on... I will come back after reviewing Dashew.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  9. #29
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    Default Re: Drogue or Sea Anchor? What and When?

    OK, I'll throw a wrench in the works.

    Drogue or Sea Anchor? What and When?

    Neither, never.

    I don't carry either one.

    Advoidance and run like hell.

    2 Hulls Dave

  10. #30
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    Default Re: Drogue or Sea Anchor? What and When?

    IMHO
    Drogue when running with the weather in lesser than worst conditions .... but if it then gets very bad a paraanchor.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  11. #31
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    Default Re: Drogue or Sea Anchor? What and When?

    I have a Para-Anchor. I have never used it. It was on board when I bought the boat. I don't envisage getting rid of it despite it's weight and bulk ..... just in case.

    I also have the ability to fabricate a drogue from the warps I have on board. I have ideas on how I would put one together.

    I don't like the idea of restricting my boats maneuverability as I've said many times before. I would prefer to run downwind at an oblique angle to the waves ..... and get away from the system. This has worked for me.

    Hoving-to is a good way to get rest, repair, and cook food ... at least in moderately poor conditions. I would still be reluctant to use it where big crests are breaking.

  12. #32
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    Default Re: Drogue or Sea Anchor? What and When?

    Paul, how restricted is Suliere in heavy wind conditions into wind?

    I used to sail a SF mk1 44 .... that had such low bridge deck clearance that I had to reduce sail very early in order not to slam it needlessly into the waves ..... this made the passage from Margarita to Granada VERY arduous. I understand that the later versions don't have this problem.

    The limitation with my Catana 40 is probably a fully developed sea at 35 knots true .... hardly ever happens though. I just tend to ease off to a more comfortable direction or slow right down. I might use the engines to back up the sails to overcome the pitching.

    It's comforting to know though that these conditions are so rare that I have trouble thinking of incidences.

  13. #33
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    Default Re: Drogue or Sea Anchor? What and When?

    We have been in 35 knots a few times but with the seas not really developed and found the journey comfortable. In my 60 foot motor boat in the early days back in the UK, I once was hit by huge waves. Some 25 foot or so and pretty close together. So much so that the boat, all 26 tons of it went fully into the air because I was going too fast. I slowed down a lot, picked my waves and went at angles to the waves - then headed for sanctuary. Since then I studied the weather so much that I became the chap who the sailing club consulted on the weather and hence never found myself in such poor conditions again.

    Suliere does not really have too much of a problem as the bridge deck clearance is much better than the 44 but then I do all I can to avoid bad weather. The last high winds we were in was coming down the USA East Coast with winds of 30 knots behind and with Suliere surfing at up to 26 knots. It was comfortable.

    What are your views on the Pardy's? They use a parachute and the Storm tactics video features it use in some detail.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  14. #34

    Default Re: Drogue or Sea Anchor? What and When?

    Quote Originally Posted by tradewindsailor View Post
    ..... so what happens when a securing line parts on a given system : beam-to and capsize?
    You can take measures to eliminate chafe. On my system the bridles have eye splices with SS thimbles. The bridle attaches to purpose-built strong points. The bridles themselves are 22mm nylon, the rode is 40mm braided nylon.

  15. #35
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    Default Re: Drogue or Sea Anchor? What and When?

    IMO the Pardey's view on storm tactics is largely irrelevant to catamarans, particularly at the performance end. Their analysis and observations of how the parachute anchor works to protect boats is sound in as far as it goes.

    Storm Tactics, if I remember rightly, was based primarily on there experiences with Seraffyn and other long keel and heavy monohulls. The Pardey's also pointed out in this book that their observations may not be relevant to the more modern lighter displacement boats with high aspect ratio fin keels and spade rudders.

    It should also be remembered that the Pardeys worked with Victor Shane at the Drag Device Data Base.

    I have not seen their videos.

    I think everyone, monohuller and multihuller alike, should read Storm Tactics and then read the Dashew's Surviving the Storm, and then progress to the many books on the Fastnet, the Sydney Hobart, etc, etc..
    I have read these all many times ..... and I am still a firm believer that the Dashew's books are far more relevant and better researched and with a higher understanding of the problems that any of the others.

    Disclosure .... I have never met the Dashews, and have and never have had any financial interest in their books. I am just an informed experience sailor who is impressed with their books.

  16. #36

    Default Re: Drogue or Sea Anchor? What and When?

    Quote Originally Posted by ForumAdmin View Post
    IMHO
    Drogue when running with the weather in lesser than worst conditions .... but if it then gets very bad a paraanchor.
    This is a commonly quoted opinion.

    IMO it's unrealistic. Lets say conditions get above 40-45 kts, and you decide it's time to run with a drogue. Then conditions deteriorate further - say 55+ kts. Are you then going to try to turn the boat around and deploy a sea anchor?

    We sailed in winds that for 4 days didn't drop below 30 kts. A couple of days constantly above 35, with gusts to 45, peaked at 48. Pretty uncomfortable and tedious but safe. We were sailing at just under 90' TWA, still on course to our destination, which was also the nearest shelter available.

    My thoughts were that if conditions reached the point where continuing toward our destination was no longer practicable, I'd deploy the sea anchor.

  17. #37
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    Default Re: Drogue or Sea Anchor? What and When?

    I agree with that.

    I do not think you can deploy a parachute when things are already bad - it has to be ready to be deployed.

    If you are running with it then its so easy to broach hence if running I would use a drogue but would in effect b y doing so discount using a parachute.

    If on the other hand I thought things were to get too bad for running with the system then I would prepare the parachute.

    I have a very robust parachute system with an adjustable bridle and all ends spliced with s/s thimbles - the chance of chafing is greatly reduced. Its a very robust system and the planned video features us deploying it foir the first time (not in very heavy seas) as a first time practice so that all the mistakes etc we make can be shown.

    I am going to read the Dashew book again but currently cannot see how moving a boat into any wave has less energy transferred to the boat than standing still in relation to the waves.

    Maxing Out (Dave) on this forum deployed both a drogue and a para anchor at different times. This was on a 39 foot cat and both system worked. The para was used in the much heavier weather of course.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  18. #38
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    Default Re: Drogue or Sea Anchor? What and When?

    Quote Originally Posted by 44C View Post
    You can take measures to eliminate chafe. On my system the bridles have eye splices with SS thimbles. The bridle attaches to purpose-built strong points. The bridles themselves are 22mm nylon, the rode is 40mm braided nylon.
    As for chafe you seem to have done as much as you can to eliminate it. How long is your rode? If it is long enough to do any good .... 40mm diameter and wet, ..... it will be extremely heavy and surely a detriment to the performance of your boat?

    This would suggest to me that you set the parachute symmetrically off the bows and have no means of adjusting you boat's attitude to it.

    Just a brief quote from the Dashew's 'Surviving the Storm' page 388 of edition 1 .... a partial quote from Erik Lerouge .....

    "A Catana 44 with exhausted and panicked crew rigged a para anchor from the bows and forebeam with a bridle and 490 feet (150m) of rope and went inside. They reported 70kt wind gusts. The boat was capsized backwards, bow over stern ......."

    I strongly suggest that you purchase a copy ..... and I hope the Dashew's won't be too annoyed with me breaching their copyright!

  19. #39
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    Default Re: Drogue or Sea Anchor? What and When?

    This would suggest to me that you set the parachute symmetrically off the bows and have no means of adjusting you boat's attitude to it.
    My system is attached directly to two strong points each end of the beam. There is 500 foot of rode. I can adjust the length of the ode because there is a huge snap block attached to one side of the bridle. It is also possible to adjust the angle to the waves but once set anymore adjustment would be very difficult indeed if not impossible.

    This is proving a very interesting discussion.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  20. #40
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    Default Re: Drogue or Sea Anchor? What and When?

    I have just checked and my copy of 'Surviving The Storm' is here in the UK with me and not on the boat hence I shall spend time this week reading it and come back to this thread after doing so.
    Safe Sailing
    Paul
    Blog: www.suliere.com

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