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Thread: Drogue or Sea Anchor? What and When?

  1. #41
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    Default Re: Drogue or Sea Anchor? What and When?

    Quote Originally Posted by ForumAdmin View Post
    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.

    Paul ...... If your boat is 'standing still' in relation to the wave, you will be going downwind at at least 20kts. You will not advance or retreat from the wave crest in front ..... on an idealised wave system of course!

    If you anchor youself with a parachute anchor you will subject your boat to collisions with the wave crests that are travelling at 20kts or more.

    Maxing-out Dave ..... what conditions were relevant during the parachute and drogue deployments?

    I have just discussed this forum with a friend of mine who helmed her 41'? daggerboard cat through a cyclone last year. She headed downwind, oblique to the waves ..... I believe they were 50' ish .... at times reaching speeds of 27kts. AP was off. She stuffed the bows in once due to fatigue and running too directly down the face of the wave, but the boat recovered with no problem. She says 27 kts .... not again! She's interested in getting a Jordans series drogue but not a parachute.
    She now has better experience that I in these conditions. I hope to encourage her to add her own comments to this discussion.

  2. #42
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    Default Re: Drogue or Sea Anchor? What and When?

    If you anchor youself with a parachute anchor you will subject your boat to collisions with the wave crests that are travelling at 20kts or more.
    And if I move into those crests that are being blown off the waves, I will be hitting them at their speed plus my speed relative to them!
    Nor are they travelling at 20 knots. The waves are not breaking in the traditional sense - they are having their tops blown off - unless you are in shallow water of course.

    I have just read page 388 - yes, very concerning and I need to sort it out.
    I am willing to change my mind but just cannot appreciate the physics!

    Your friend, who is very welcome to join the discussion, did not deplpy a parachute.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  3. #43
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    Default Re: Drogue or Sea Anchor? What and When?

    Paul ...... agree with using the motor to motor into the waves will increase the forces on the boat, but motoring away will reduce it.

    You should read Dashew's analysis of the mechanic of waves from page 215. This is pretty much what I understand to, any differences are pretty immaterial to this discussion.

  4. #44
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    Default Re: Drogue or Sea Anchor? What and When?

    I will read the lot!

    The Catana that capsized we know little about - sounds as if the rode snapped. This is the problem we do not know enough.Other boats (monos) were smashed to bits and sank.

    What I have done is 'heave to' and qwhen I do it seems to switch off the sea.

    When running downwind at an angle you are still hitting the non=breaking waves at the speed of the boat.

    Are you saying that running downwind in such conditions should always be done with a drogue?
    Safe Sailing
    Paul
    Blog: www.suliere.com

  5. #45
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    Default Re: Drogue or Sea Anchor? What and When?

    Quote Originally Posted by ForumAdmin View Post
    I will read the lot!

    The Catana that capsized we know little about - sounds as if the rode snapped. This is the problem we do not know enough.Other boats (monos) were smashed to bits and sank.

    What I have done is 'heave to' and qwhen I do it seems to switch off the sea.

    When running downwind at an angle you are still hitting the non=breaking waves at the speed of the boat.

    Are you saying that running downwind in such conditions should always be done with a drogue?
    I have an open mind on drogues. What I would want to prevent is overtaking the crest and crashing off the top. I have done this in rather smaller waves in current ..... not to be recommended!

    There are many ways to operate the boat in conditions up to the severe conditions of a cyclone, and indeed not all cyclone conditions will be the same. There are other conditions that are just as severe, if not worse. I've sailed through some pretty atrocious conditions off Start point for instance.

    Heaving-to is great in certain conditions ..... but I'll keep an open mind on whether it would be appropriate in extreme weather with large breaking seas.

    Parachute anchors have their place under certain circumstances ..... but I am convinced that they can be dangerous in severe weather and I doubt there will come a time where I would use one ..... unless I thought that it was my best defense against runny onto a lee shore.

    When you are running downwind you are hitting the crest at the crest speed minus the speed of the boat (vmg in direction of the wave of course). You can assume that THE CRESTS ARE MOVING AT THE SPEED OF THE WAVE TRAIN

  6. #46

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

    Quote Originally Posted by tradewindsailor View Post
    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!
    The bridles are 20m, the rode 100m. Yes, the rode is pretty heavy, especially when it's wet. I estimate around 40-45kg.

    This is the correct rode/bridle according to my sea anchor's manufacturer. Maybe 150m that Catana had was too long? Or the sea anchor too small?

    If a boat on a para anchor could be capsized bow over stern, it's hard to see why it wouldn't go over frontways on a drogue, given that by definition the sea anchor has more holding power, and would be preventing the bows from lifting, as well as the fact that the bows themselves are less buoyant than the sterns..

  7. #47

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

    Quote Originally Posted by tradewindsailor View Post
    Paul ...... If your boat is 'standing still' in relation to the wave, you will be going downwind at at least 20kts. You will not advance or retreat from the wave crest in front ..... on an idealised wave system of course!

    If you anchor youself with a parachute anchor you will subject your boat to collisions with the wave crests that are travelling at 20kts or more.
    The waves move, but the actual water in them does not. (Unless you're in very shallow water.)

    I also happen to believe the front end of a boat is DESIGNED to be constantly colliding with the water, whereas the rear end is not.

    I'd prefer to have waves breaking over the front end than into the cockpit.

  8. #48
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    Default Re: Drogue or Sea Anchor? What and When?

    Doesn't seem much point answering this yet again.

    Go to sea. Anchor your self with parachute anchor in say 35 knots and then tell me that the breaking crest don't move!

  9. #49
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    Default Re: Drogue or Sea Anchor? What and When?

    Or save yourself some hassle and look at the wind driven crests on the duck pond ...... same principle.

  10. #50
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    Default Re: Drogue or Sea Anchor? What and When?

    Quote Originally Posted by ForumAdmin View Post
    I agree with that.
    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.
    Note that the drogue used by Dave was quite different from a Jordan Series Drogue.

  11. #51
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    Default Re: Drogue or Sea Anchor? What and When?

    Go to sea. Anchor your self with parachute anchor in say 35 knots and then tell me that the breaking crest don't move!
    I am not disputing that they move but only a short distance and they are basically wind blown tops (providing you are in deep water). Yet there is no doubt that when sailing down and across you are moving into the waves and hitting them with great risk of one breaking over the stern.

    Also the parachute by all the accounts I have read including the Pardy's seems to avoid breaking waves which break either side of the boat and not in the path that is relative to the wind.

    I live on a lake and any fishing boat drifting down always leaves a long slick of calmer water behind it.

    I am looking forward to studying the Dashews this week.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  12. #52
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    Default Re: Drogue or Sea Anchor? What and When?

    A parachute anchor will be directly upwind .... especially with catamarans that have no keels. I hope we can agree on that?

    Waves are produced not only from the prevailing wind direction but also from all other recent directions that the wind was blowing. Agreed?

    When a front passes through there is usually a very large shift of wind direction, 90 deg is not unusual. Agreed? And the wind is usually quite a bit stronger too.

    So now we have the new waves just being generated due to the new direction of the wind ..... BUT the previous fully developed waves are still there and beam on to your boat. Agreed?

    Now how is the wake of the parachute anchor going to protect the boat?

  13. #53
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    Default Re: Drogue or Sea Anchor? What and When?

    In offshore engineering a great deal of time, trouble, and money goes into the development of ways of calculating the loads imposed on offshore installations by breaking waves. This is a reasonable example:
    http://www.sintef.no/home/MARINTEK/P...atform-column/
    Frankly, apart from the structure being heavy and unable to react as quickly to the wave crest as a multihull, I don't see a great deal of difference for the parachute anchored multihull.... oh, and look at that wave crest ... looks to me that it imparts some impact loads.

  14. #54
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    Default Re: Drogue or Sea Anchor? What and When?

    A parachute anchor will be directly upwind .... especially with catamarans that have no keels. I hope we can agree on that?
    Agreed.

    Waves are produced not only from the prevailing wind direction but also from all other recent directions that the wind was blowing. Agreed?
    Agreed.

    When a front passes through there is usually a very large shift of wind direction, 90 deg is not unusual. Agreed?
    Agreed.

    So now we have the new waves just being generated due to the new direction of the wind ..... BUT the previous fully developed waves are still there and beam on to your boat. Agreed?
    Partly agreed.

    We are really talking about very strong winds here - over 50 knots. The prevailing wind at the time will dominate over the previous wave systems and the only breaking waves (really wind blown tops) will be in the current direction of the wind. The previous waves will be there but not breaking and nowhere near dominating the wave pattern.

    I have fished countless times with a drogue and found that the calm lane does work very well.The Pardy's put their mono at an angle to the wind so as to create a wide a lane as possible with a mono.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  15. #55
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    Default Re: Drogue or Sea Anchor? What and When?

    I don't see a great deal of difference for the parachute anchored multihull.... oh, and look at that wave crest ... looks to me that it imparts some impact loads.
    The difference is that there is a static object taking all the load but witrh the boat it rises up and down with the water and hence avoids the vast bulk of the imposed load. A lighthouse can have breaking waves higher than its own height but that would not be the case if to floated .... promise.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  16. #56
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    Default Re: Drogue or Sea Anchor? What and When?

    .... except that of course the breaking part of the wave crest is on the surface .....

  17. #57
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    Default Re: Drogue or Sea Anchor? What and When?

    Your strategy as I understand it and correct me if I am wrong:-
    1. Run with the sea searching for the non breaking crests.
    2. Stay with the weather so that you prolong your time in the storm by travelling with it.
    3. Risk breaking waves over the stern as you dodge and adjust speed to avoid them hour after hour.
    4. Have no parachute on board so when you run out of sea you turn into the wind and probably sink
    Is that correct?
    Safe Sailing
    Paul
    Blog: www.suliere.com

  18. #58

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

    Quote Originally Posted by tradewindsailor View Post
    Doesn't seem much point answering this yet again.

    Go to sea. Anchor your self with parachute anchor in say 35 knots and then tell me that the breaking crest don't move!
    Actually I've been anchored in 35 knots on a lee shore with about 30 miles fetch, after an unforecast change at Cape Bowling green. Have you?

    It was surprisingly comfortable. We eventually left, not due to discomfort, but because I couldn't sleep on a lee shore, so figured I might as well be sailing. Made a coffee, had some breakfast, no problem. If it hadn't been a lee shore I could have slept.

    Very little of the water in waves is moving horizontally. Even though it looks like it must be, it isn't. That's just a fact you need to accept.

  19. #59
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    Default Re: Drogue or Sea Anchor? What and When?

    Was that anchored with a parachute or just anchored?

    In either case of course you are reasonably still. If anything it would be worse with an anchor as you then would have any current effect.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  20. #60

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

    Just anchored. We were very surprised at how comfortable it was, given the wind strength and how rough the water looked.

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