Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-04-2007, 16:01   #31
Registered User
 
Benny's Avatar

Join Date: Jan 2007
Location: St Catharines ON, CAN
Boat: Irwin 37 CC ketch 'Ta-Keel-Ah'
Posts: 396
Has anyone out there actually used one or have a story to relate of a boat having used one in a severe storm. Horses mouth testimony would help us determine if they are worth using or have one just in case of the last resort.
__________________

__________________
Randy Benoit
I37CC 'Ta-Keel-Ah'
Benny is offline   Reply With Quote
Old 09-04-2007, 16:06   #32
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2005
Boat: Outbound 44
Posts: 4,569
There are first hand reports and analysis in Dashew's book Surving the Storm..

Paul L
__________________

__________________
Paul L is online now   Reply With Quote
Old 09-04-2007, 16:25   #33
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Whangaparaoa,NZ
Boat: 63 ft John Spencer Schooner
Posts: 956
I used something like the Abbott drogue, but all I did was attach a long piece of line to the head of my stern anchor then toss the lot over the stern. Brought the two tails to the primary winches then "trimmed" till I had a speed I was comfortable with in the conditions. Worked fine in some seriously extreme weather.
Over a period I got so fond of it I would use it even when conditions were less than extreme, e.g. beam reaching in fresh conditions and waves the self steering would drop below the wave crests and the boat could wander, chuck out a little bit of drogue and keep sailing like you are on rails.
Anything away from land and I would suggest you take the advice given and get below, having first done everything to help the boat ( drogue being my choice of weapon when it gets really ugly). You read about more boats being lost through fatigue of the crew than being overwhelmed by wind and wave.
__________________
dana-tenacity is offline   Reply With Quote
Old 10-04-2007, 00:54   #34
Registered User

Join Date: Dec 2006
Posts: 249
I don't know if I quite agree with some of this although my oceanography is very limited.
I don't think the boat is actually moving at wave speed except in certain limited conditions, because the wave motion is only passed on to the water to a very limited extent. That is a cork moves up and down and to a limited extent back and forth.
The Jordan drogue is designed for breaking waves ie to cope with that force which is about 10 x that normally encountered.
A wave will break when its height/wavelength is > 7. Obviously when it nears shore this condition applies.
However although the Coastguard tests were done in near shore shallow conditions, one would not be using a Jordan drogue approaching a lee shore.
In offshore conditions where it would be deployed one would require around 50 knots of wind over a long fetch to give a wave height of 10 m with a wavelength of 160 m.
In moderately deep water this would give a wavespeed of approx 36 mph for a freak wave and half this for most.
These are not true breaking waves under the above formula although the tops may be blown off.
What I think happens is rather than reaching wave speed, when the wave is high enough the boat is lifted and then begins to accelerate under gravity and fall down the 10 m. If the boat was say 10 m long it would it would be on the wave for around 1.5 sec or rather more because it would be moving with the wave, say 2.5.
The acceleration due to gravity is 10 m/sec/sec. Being on a slope the boat in effect slides down it. My physics after all this time is a bit rough but I think the maximum speed it could reach is the same speed as if it fell the full 10 m so the slope doesnt effect the end speed rather the acceleration. So it would hit at most 20mph and probably half this because of drag say 10 plus maybe the initial speed say 7 giving 17 knots.
when it hits the trough there is some major impact of deceleration which could slew the boat if it wasnt square on which is very likely and that broach leaves it vulnerable to inevitable rolling by the next wave.
Hence I think the key is to slow the boat in ordinary circumstances ie not breaking waves as the worst possible case but in pretty extreme circumstances, and this can be done by a long drogue preferably weighted so it goes down quite deep compared with the wave height. It may be preferable to be multiple but I think lesser means than full deployment of a Jordan drogue may be generally useful.
Conversely if you actually slow the boat too much, presumably it could slide backwards down the rear of the wave and a windvane wouldnt realise you were in reverse so turn the wrong way making you again vulnerable to a roll.
__________________
chris_gee is offline   Reply With Quote
Old 11-04-2007, 09:30   #35
Registered User
 
Jimske's Avatar

Join Date: Jul 2006
Location: Connecticut
Boat: Brown Searunner 31 #108 - Drole D'Oiseau
Posts: 333
Various Comments

Maxingout - Great informative website! Do I see a documentary in the making? Nice!

Chris Gee - Jordan's discussion would agree with you on a lot of points. But the JSD may not be able to actually stop the boat to a point where it actually moves backwards. Given the weighted tail, part of the drogue collapses as the boat slows making the boat speed up. When it speeds up the drogue fills and slows the boat down so it seems that the boat will never be static but in a constant state of forward motion between design speed parameters. Can a forward moving sea be harnessed to pull a vessel backwards?

Big Damaging Seas - Driving a Catalina 42 in the Gulf Stream I encountered very large seas. I've heard that one cannot judge wave height from a boat so I don't know how high they were though they seemed to be at least as high as the mast when in the trough. The surprising thing to me at the time was how very frequent they were. I would have guessed that seas that big would be far apart and not so steep. Each wave was breaking and somtimes I caught the part of the wave that broke while other times I was at the crest just prior to it breaking. We took all the waves just off the stern as they picked the boat up. When the wave boke it broke about 5 or 6 feet over my head while standing at the helm. My reaction was to drop to my knees and hold on to the wheel until the breaking portion past. The force of the break hitting the companionway slats was relatively minor though the boat eventually got a bit wet inside. So from this sole experience I concurr with Jordan that the breaking waves being aerated cause no damage.

I did not deploy any drogue or sea anchor. But there was no way I was going to attempt to surf down these steep inclines. We allowed the boat to get picked up to the crest. The Catalina turns on a dime. As the crest passed we turned the boat and "walked" down the back of the wave at about a 45 degree angle. Once in the trough we turned the boat with the wave and allowed it to pick us up again. We continued this very tiring maneuver for many hours (fortunately it was daylight) switching on and off every hour between two people.

During one of these wave "events" I failed to turn the boat properly and was about to broach. This ws scary. My reflex was to turn the boat into the wave which was even more scary. The boat felt like it was going straight up in the air and I turned the boat at the crest and walked down. phew. I was really worried (perhaps unnecessarily) that the boat would fall off the back of the wave.

If this every happens to me again - I would readily deploy the JSD. I would have been happy to keep from surfing, slamming into the trough, and take breaking waves over the stern of the boat.

Jim
__________________
Jimske is offline   Reply With Quote
Old 12-04-2007, 19:48   #36
Registered User

Join Date: Dec 2006
Posts: 249
Interesting account of the walking.
I didn't mean that the drogue would bring the boat to a complete stop so it would then fall backwards.
If the boat is slower horizontally across the ground than the wave eventually passes under it.
There are two motions in a wave. The wave moves but the water within it largely does not. However there is a cyclic particle motion within the wave.
If the wave is moving left to right, then at the crest the particle motion is horizontal clockwise ie to the right, the reverse in the trough.
At the crest I calculated recently that at F9 with a 500 mile fetch ie approx 40 ft waves the water speed would be around 10 knots plus in that circular motion. I can't locate the formula I used but the other notes I have from the time seem accurate (hopefully).
Therefore if the boat is moving at at the crest at say 7 knots the water is moving horizontally at 10 the flow across the rudder is 3 knots in reverse.
As the boat starts to go down the back the forward flow of the water is less, until in the trough it is in the opposite direction. The boat speed is also slowed by maybe a knot or two by backward acceleration due to gravity, giving say 5 knots over the ground. My main point is that near the crest the water flow across the rudder will be reversed. The drogue would help keep the boat in line, but a windvane would accentuate rather than correct any veering ( so too probably would a helmsman).
I would agree that a drogue would be helpful, because the faster one goes on the wave front the less the relative speed of the wave, and the longer the wave takes to pass, so the greater the acceleration as the boat is accelerating through gravity for longer. As it slides down the slope the slope keeps moving along with it.
A heavier boat may reach a limiting speed and always be slower than the wave whereas a cat or light boat may go faster end up in the trough decelerate, then rise up the same wave front again.
Staying significantly slower than the wave seems a good idea.
__________________
chris_gee is offline   Reply With Quote
Old 13-04-2007, 03:20   #37
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Whangaparaoa,NZ
Boat: 63 ft John Spencer Schooner
Posts: 956
The idea of the flow across the rudder is interesting, but in reality I have never experienced it.
__________________
dana-tenacity is offline   Reply With Quote
Old 13-04-2007, 08:34   #38
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2005
Boat: Outbound 44
Posts: 4,569
Quote:
Originally Posted by chris_gee
...
Staying significantly slower than the wave seems a good idea.
I'm not so sure about this. If the waves are not breaking, then keeping the boat at a drivable speed and under enough control so as not to broach is key. The real danger starts once you are dealing with breaking waves, and I'm not sure your analysis holds there.

Paul L
__________________
Paul L is online now   Reply With Quote
Old 13-04-2007, 15:13   #39
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Whangaparaoa,NZ
Boat: 63 ft John Spencer Schooner
Posts: 956
If the waves are not breaking there is no problem, though you may choose to employ a drogue to improve steering .
__________________
dana-tenacity is offline   Reply With Quote
Old 13-04-2007, 21:15   #40
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,864
Images: 4
I've experienced reverse flow across the rudder. This was approaching San Francisco, near the infamous "potato patch' just outside the dredged ship channel, where the bottom rises from about 100 ft to a shoal of 20 ft. The conditions were moderate at worst, with swells only about four or five feet.

However, there was an ebb current running out of the bay, and the swells were quite steep. This is pretty common as you enter S.F. Bay.

No big deal, but as we ran in, with the swells and wind behind us, from time to time the helm would go very light and I believe the flow did reverse slightly. Our keel kept us on track, but the rudder was best kept centered during the flow reversal.

These were far from "deploy the drogue" conditions, but I can easily believe that flow reversal occurs under some circumstances.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 09-09-2009, 10:50   #41
Senior Cruiser
 
sandy daugherty's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: near Annapolis
Boat: PDQ 36 & Atlantic 42
Posts: 1,178
I respect your experience, Dave, but the Coast Guard report addresses each of your points, with objective tests. In my mind, if a vessel has room for only one system, I see greater advantage in the series drogue.

I've looked for a situation where the chute, with its difficulties, is superior to the series drogue and can imagine only one, where (as in the grand banks) water depth and bottom structure could allow the series drogue's anchor to catch and create an overwhelming shock load to the system.

Please point out what I am missing here.
__________________
sandy daugherty is offline   Reply With Quote
Old 09-09-2009, 11:22   #42
S&S
Registered User
 
S&S's Avatar

Join Date: Jul 2009
Boat: 48' 1963 S&S yawl
Posts: 851
Images: 6
I don't see a situation where i'd really want to "stop" the boat. It would be nice to keep the speed at 5 kts. or so. In 50 kts or so w/ short period 20' seas she liked to pick up speed and bury her nose into the wave in front of the boat. No damage but it was creepy waiting for the nose to rise. It was also very wet. I'd like to keep the ability to steer away from steep or breaking waves as we got "clipped" a couple of times by the breaking jet and needed hard rudder to keep from getting spun broadside into the breaking wave. If we were going too slow we probably would have damaged the rudder .
__________________
S&S is offline   Reply With Quote
Old 09-09-2009, 11:47   #43
Senior Cruiser
 
Talbot's Avatar

Cruisers Forum Supporter

Join Date: Jun 2004
Location: Brighton, UK
Boat: Privilege 37
Posts: 3,579
Images: 32
Quote:
Originally Posted by sandy daugherty View Post
I've looked for a situation where the chute, with its difficulties, is superior to the series drogue and can imagine only one, where (as in the grand banks) water depth and bottom structure could allow the series drogue's anchor to catch and create an overwhelming shock load to the system.
Under those conditions, I would assess it as far more likely that the 18ft of parachute plus water depth, would mean that the parachute would tangle with the bottom long before the chain on the end of the series drogue was in any danger.

I believe that the one condition where I would consider the parachute before the series drogue is where the drift has to be minimised. The series drogue will cut speed down to 1-2 knts, but I would expect the parachute to be less than 1 kt - and there have been conditions where the current has been up-wind, and the boat on a parachute has actually achieved a VMG to windward
__________________
"Be wary of strong drink. It can make you shoot at tax collectors - and miss."
Robert A Heinlein
Talbot is offline   Reply With Quote
Old 09-09-2009, 12:23   #44
Registered User

Join Date: Nov 2005
Location: Ohio
Posts: 2,313
We have a drouge but the thought of using it and loading the steering gear is more frightening. To be totally honest we probably run off and hope the waves remain managable. If it reached the point where that was too scary we would cycle back fore reaching with a very small storm jib on the inner forestay.
__________________
Joli is offline   Reply With Quote
Old 09-09-2009, 14:08   #45
Senior Cruiser
 
Talbot's Avatar

Cruisers Forum Supporter

Join Date: Jun 2004
Location: Brighton, UK
Boat: Privilege 37
Posts: 3,579
Images: 32
Quote:
Originally Posted by Joli View Post
We have a drouge but the thought of using it and loading the steering gear is more frightening.

I think you need to do more research. The drogue will not load up the steering gear, in fact it is more likely to reduce the loading on it. The jordan series drogue website shows video of how it works in tank tests and reality. I suggest you look at those videos. I also suggest you read the USCG report.
__________________

__________________
"Be wary of strong drink. It can make you shoot at tax collectors - and miss."
Robert A Heinlein
Talbot is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Heavy-Weather Tactics: GordMay General Sailing Forum 25 28-10-2003 16:44



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 03:46.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.