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10-11-2018, 08:35
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#196
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Registered User
Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,916
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by Palarran
IMO there should be no such thing as passive handling of a catamaran in survival conditions. That is a huge difference between cats and mono's.
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Many cruising crews consist of husband & wife only. Often -like in our case- this means a singlehandling skipper with a helping deckhand who can do a watch in nice weather only.
Survival conditions means very strong winds for days. Reality for us would be that active handling of survival conditions just ain't gonna happen, as the skipper will be totally exhausted after some hours.
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10-11-2018, 08:51
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#197
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Registered User
Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,916
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by thinwater
The cones are 5 inches, so about 6 times that many.
The effect of shape is minor between these, but the fact that the cones run in each other's wakes is major; the drag per cone is less when there is a string.
Based on testing, the answer is many thousands and a string a mile long.
The larger issue is that a long JSD towed at VERY low speed droops, and so it is not as "stiff" when it takes a hit. It tends to give a little. This is good for a drogue, but very bad for a chute, for reasons others have explained.
A long JSD is going to behave VERY differently from a chute.
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From memory I'd say the cones I used to assemble my JSD were about 20cm
or 7,7 inch in diameter so a bit larger than that.
Anyway, it's going to be a huge number of cones to match the drag of a sea anchor.
But you are right that it will behave very different from a sea anchor if the tail's cones are allowed to sink. I think this catenary creates most o the bungee feeling associated with the JSD.
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10-11-2018, 09:09
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#198
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Elvish meaning 'Far-Wanderer'
Join Date: Jan 2008
Location: Boat - Greece - Me - Michigan
Boat: 56' Fountaine Pajot Marquises
Posts: 3,489
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by rabbi
Many cruising crews consist of husband & wife only. Often -like in our case- this means a singlehandling skipper with a helping deckhand who can do a watch in nice weather only.
Survival conditions means very strong winds for days. Reality for us would be that active handling of survival conditions just ain't gonna happen, as the skipper will be totally exhausted after some hours.
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I know what survival conditions means, but it doesn't have to be strong winds for days. The OP was interested in what to use for offshore sailing. If the crew isn't prepared to do what is necessary to safely sail their boat offshore, they shouldn't. For sure their are excellent sailors who can singlehand catamarans across oceans - but they are rare. A crew of 3 with 2 being competent sailors to me is a comfortable minimum.
__________________
Our course is set for an uncharted sea
Dante
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12-11-2018, 03:16
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#199
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Registered User
Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,916
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by Palarran
If the crew isn't prepared to do what is necessary to safely sail their boat offshore, they shouldn't. For sure their are excellent sailors who can singlehand catamarans across oceans - but they are rare. A crew of 3 with 2 being competent sailors to me is a comfortable minimum.
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That may be your comfortable minimum but for us and many other cruising couples reality is different. Since we can't just spawn some trained crew when needed we have to accept that we have to deal with storms on our own.
After a couple of hours actively sailing in a building storm any single/short handed crew will be exhausted, possibly when the worst part of the storm arrives. So passive storm tactics are a necessity for shorthand / singlehanded sailors.
That may not be the ideal situation but the alternative is to stay home (or get crew, which opens another can of worms).
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12-11-2018, 04:02
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#200
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Registered User
Join Date: Sep 2014
Location: On the boat
Boat: LAGOON 400
Posts: 2,347
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Re: Drogues or sea anchor or neither
Dont forget good AP could be 1 crew member. They are critical in such conditions. Need to have gyroscope. Set to very high sensitivity. Drove us beam on up tp 5m waves for 2 days without a single glitch. Cant match AP precision manually.
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12-11-2018, 07:29
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#201
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Registered User
Join Date: Jun 2018
Location: liveaboard - since 2022 Caribbean
Boat: Privilege 435 Catamaran
Posts: 109
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Re: Drogues or sea anchor or neither
Increase of drag by adding holes is done by the increase of water turbulence when water flows through the holes. Turbulence works as a break; see the YouTube videos on airplanes. Without turbulence after every airplane fuel consumption would decrease a lot. Spoilers at race cars have also the purpose to reduce turbulence, thus increase speed.
Going to the extreme makes the problem easier to be understood.
Increase the size of the holes that there is only one hole left, thus no fabric anymore and the water flows with little turbulence through the hole and has a only tiny little bit of drag.
Close all holes and as soon as the drogue is filled with water there is only the friction of the water at the fabric outside the drogue causing drag.
Thus, it is necessary to get the right size of holes to create the maximal turbulence, thus the maximal drag.
For my feeling 1cm holes could be pretty good, but I don't know what is the optimal size of holes. Mathematical simulation are not really possible because the turbulence is difficult/not possible to be simulated. A series of test is needed. Cost a few (5???) drogues but would end in a drogue with maximal drag for its seize and material.
As written earlier, the skipping on the surface can only be avoided by weight. The parallelogram of forces shows this clearly.
As for the JSD, all the little parachutes create a lot of turbulence, thus the JSD slows down a boat.
I would prefer a shark drogue with holes because it is small and easy to handle.
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12-11-2018, 07:35
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#202
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Registered User
Join Date: Jun 2018
Location: liveaboard - since 2022 Caribbean
Boat: Privilege 435 Catamaran
Posts: 109
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by arsenelupiga
Dont forget good AP could be 1 crew member. .....
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What is an "AP" please?
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12-11-2018, 08:23
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#203
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Registered User
Join Date: Mar 2018
Location: UK
Boat: Freedom 40
Posts: 116
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by p435
What is an "AP" please?
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Auto Pilot?
__________________
Beyond
Freedom 40 CC
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12-11-2018, 13:43
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#204
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Registered User
Join Date: Jun 2018
Location: liveaboard - since 2022 Caribbean
Boat: Privilege 435 Catamaran
Posts: 109
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Re: Drogues or sea anchor or neither
Auto Pilot - this makes sense. Thanks!
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12-11-2018, 13:49
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#205
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Registered User
Join Date: Jun 2018
Location: liveaboard - since 2022 Caribbean
Boat: Privilege 435 Catamaran
Posts: 109
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by rabbi
Fully agree.
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Maybe I'm completely wrong but that would be my attempt at building a drogue: Three daisy chained elements connected by dyneema.
A three element drogue should be much easier to deploy, retrieve and stow than a JSD - and at the same time almost as powerful and dependable.
It wouln't offer the dynamic breaking power adjustment (more speed => more cones active => bungee like feeling) that the JSD has but I have no idea if this would really be a problem.
I like the shark as it's design holds a lot of water (further reducing the risk of pulling it out of the water), seems designed for daisy chaining and it's a neat package.
However pricing makes a three element shark drogue very hard to swallow. Not to mention that I don't want to give business to folks like Fio.
.....
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3 drogues daisy chained makes a lot of sense. Unfortunately you are also correct about the price.
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12-11-2018, 14:28
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#206
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Writing Full-Time Since 2014
Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,569
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by p435
3 drogues daisy chained makes a lot of sense. Unfortunately you are also correct about the price.
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If you get a chance, take a close look at how a Delta Drogue is built. Scaled down, it is a pretty simple fabrication, no more complex to sew than a cone of the same size, but far more stable.
One of the keys to the JSD is a cone design that is cheap. At the scale you are contemplating, the Delta Drogue is the next simplest design.
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13-11-2018, 01:55
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#207
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Registered User
Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,916
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by p435
Increase of drag by adding holes is done by the increase of water turbulence when water flows through the holes.
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you are trying to increase / optimize drag of an exisiting design by a few percent. It might be easier & cheaper to just make the drogue a bit larger to achieve the same thing.
The drawback: Every hole in a uniform industrial fabric will create a weak spot where fraying and tearing can start.
The effort to make 100 or so tiny holes and ensure that the edges are perfectly sealed so they don't fray will be huge. Much more effort than to just make the drogue a bit larger.
Risk of catastrophic failure will be much greater than a larger version of the drogue.
Quote:
Originally Posted by p435
As written earlier, the skipping on the surface can only be avoided by weight. The parallelogram of forces shows this clearly.
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Skipping on the surface can only be avoided by spreading the load over multiple drag devices over a long distance. Weight alone will only aid by letting the drogue run a bit deeper.
See picture taken from Victor Shane's Drag DB:
As the pic says: "Drogue is secure in the back of the wave".
There is no way this can be achieved with a single device drogue in non-uniform wave lengths.
All you can do is to spread the load over multiple drag devices located in different sections of the wave train.
EDIT: I should add that this is just my personal view and not based on any type of research. Just simple physics. Some other poster might jump in to tell you that this doesn't apply to their drogues because of X or Y and lots of research.
BTW: Still no answer from Fio.
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16-11-2018, 08:35
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#208
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Marine Service Provider
Join Date: Apr 2010
Location: Newport Beach, California
Boat: Beneteau Oceanis 35
Posts: 236
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Re: Drogues or sea anchor or neither
As already mentioned in post #167 why would you want to modify the Shark Drogue or any other drogue? For one, why modify something that works? Two, tampering with a drogue likely nullifies any warranty a manufacturer offers.
Whether you use a single or multiple drogue set up anything can be partially or completely pulled out of the water. However, this kind of action is not the norm. Want to reduce this unlikely problem then add plenty of weight and pay out long lengths of rode. As shown in YouTube video.
Offering untested solutions combined with suggestions of modifying manufactured equipment that’s been effective for decades makes no sense. It only complicates storm drogue deployment. Something we feel is pretty straight forward. The U.S. Coast Guard has deployed para-anchors and speed-limiting drogues from their vessels for years. Wouldn’t they have mentioned something by now if there was anything to be concerned about?
Morgans Cloud provides an interesting perspective.
“#11 Beware The Forums by Morgans Cloud
If ever there was a cauldron that boils up “the sum of their fears” and then serves the result up in an ugly soup of terror, it’s the modern sailing forum, in which posters keep adding their own fears to a subject until the thread is scores (or even hundreds) of comments long.
Much of it is simply oft-repeated memes without much rational thought about validity. And a distressing amount of it is simply other cruisers trying to puff up their egos, or dampen their own fears, by telling the rest of us how smart and well prepared they are.
(By the way, although I don’t hang out on forums, I’m sure I have been guilty of the latter two sins here in the comments. I will try to do better in future.)”
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16-11-2018, 08:49
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#209
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Elvish meaning 'Far-Wanderer'
Join Date: Jan 2008
Location: Boat - Greece - Me - Michigan
Boat: 56' Fountaine Pajot Marquises
Posts: 3,489
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Re: Drogues or sea anchor or neither
Quote:
Originally Posted by Fi2010
Morgans Cloud provides an interesting perspective.[/FONT]
“#11 Beware The Forums by Morgans Cloud
If ever there was a cauldron that boils up “the sum of their fears” and then serves the result up in an ugly soup of terror, it’s the modern sailing forum, in which posters keep adding their own fears to a subject until the thread is scores (or even hundreds) of comments long.
Much of it is simply oft-repeated memes without much rational thought about validity. And a distressing amount of it is simply other cruisers trying to puff up their egos, or dampen their own fears, by telling the rest of us how smart and well prepared they are.
(By the way, although I don’t hang out on forums, I’m sure I have been guilty of the latter two sins here in the comments. I will try to do better in future.)”
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Wow - Great quote and I couldn't agree more.
The fear happened to me in my first two or three years here. Still, there is a lot of good info to be gained so it's worth sorting through the BS.
__________________
Our course is set for an uncharted sea
Dante
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16-11-2018, 08:53
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#210
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Writing Full-Time Since 2014
Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,569
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Re: Drogues or sea anchor or neither
Just for context, 2 weeks before "11: beware of forums,", Morgan's Cloud posted a full article titled "Just Get a Series Drogue Designed By Don Jordan... Damit."
Both are good reading. He's one of the smartest writers out there.
The way I see it, speed limiting drogues, the JSD, and chutes are 3 different tools. Like most tools, you need to learn how to use them and then decide which tool fits the job. Perhaps none. Perhaps more than one. All three are good tools.
As a coastal sailor, the only one I have ever really needed was a speed limiting drogue for emergency steering. I managed my steering failure by jury rigged drogue, but a Shark or other sure would have been nice. Thus, my opinion is colored by what I see as the most probably use (since most of us are coastal sailors, at least most of the time, and that's where most of the logs are).
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