series drogues

[bryanglover]

I was cruising to Deal Island, in Bass Strait, when a gale caught my two sons and I by surprise. The 3 of us are inexperienced sailors, and confidently left Port Phillip heads with good weather reports. We deployed a series drogue, and spent 6 hours in the cabin in 50Knot winds on the 40 degrees south line. This was a life changing experience and since then i have started making series drogues in Melbourne. If anybody is interested in representing me in the UK please contact me at seriesdrogue@hotmail.com
regards

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[MIKE_MCKIE]

Series drogue?? Please shed some light on this new (to me) term.
Brgds

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[Guest]

Would it be sea-anchors in series ? nm

*

<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Benbow]

Re: Would it be sea-anchors in series ? nm

Series drogues are - well - drogues in series. Lots of small cones sewn down the length of rope and trailed invariably off the stern to survive extreme conditions. They are said to have much more 'give' and be more manageable than a single huge drogue usually deployed off the bow. I believe that a US CG study found them to be the best means of survival in a small boat.

Details of both systems <A target="_blank" HREF=http://www.cruisinghome.com>here </A>

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[bryanglover]

the US Coast Guard report can be seen http://home.swift.dsl.com.au/~jack47/drogue
regards

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[Talbot]

Your link does not work.

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[kimhollamby]

Note to Bryan

Bryan, this edges up to our Ts and Cs regarding commercial advertising but you seem to have aroused some interest among users of this forum regarding the exact nature of what you say saved you.

If you come back and explain in more detail what it is you are producing and how it works without trying to flog it to death I'll let this run for a bit.

Fair?

Kim (forum admin)

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[bryanglover]

Re: Note to Bryan

sounds fair kim
the US coast guard looked at existing storm tactics ( lying ahull, heaving too, running) and equipment ( cone drogues and large sea brakes from bow etc.)and decided all had flaws, for small boats in storm/breaking sea conditions.
the coast guard and an engineer named jordan spent 5 years developing and testing the series drogue. in their final report they state no yachts would have been lost in the terrible fastnet race of 1978, if series drogues had been deployed by competators.
my boat asgard is 28ft 4500kg, the series drogue i use, is 100 5inch ripstop nylon cones attached to a 75mtr double braid nylon line, with the anchor attached to the end. the near end is attached to a bridle, which is in turn attached to port and starboard genoa tracks.
it was very easy to deploy feeding slowly out the stern, the storm lasted about 6hrs, and we steep waves with no backs, some breaking on occasion. the stern rose to every one, we took one large wave into the cockpit, no damage. over the six hours, we difted 9nm, loads on equipment is low, because if boat slows, anchor starts sinking keeping line tight, so there is no jerking associated with other drogues and sea anchors. i have rings built into the bridles and ran lines to sheet winchs and found i had some steerage.
I need someone in the UK to help me organise
regards bryan



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[AndrewB]

DIY version.

Pushing your luck, Bryan! While I agree with you about their efficacy, they are quite easy to make, which is what most people do. The US CG approved pattern was published in PBO a few years back, and is similarly available <A target="_blank" HREF=http://www.sailrite.com/PDF/DrogueKit.pdf>HERE</A>. A popular made-up version has been available from the US for some time, and can be obtained in the UK (I won't advertise it, but its Googled easily enough).

 

[bryanglover]

Re: DIY version.

andrew, i can not agree that cutting out 100 or more 5inch cones, and making 800 runs on a sewing machine, on slippery ripstop nylon can be called easy. you have not made one your self, have you. my product is half the goggle price. because of the low aud

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[AndrewB]

Err ... yes. Well, partly.

<blockquote><font size=1>In reply to:</font><hr>

<font size=1>you have not made one your self, have you. </font size=1>

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For many years I've carried a 150 meter 3/4" three-strand warp* with a length of chain spliced on, to use as a drogue as was at one time recommended. It did not offer sufficient braking when used in bad weather. I was impressed by the US CG report of the series drogue reviewed in PBO, subsequently amply supported by tank tests at the Wolfson Unit in Southampton, and recommended in "Heavy Weather Sailing". So I started to add cones following the PBO instructions. Making them is one of those really simple repetitious tasks suitable for idling away quiet time on watch on long passages. Tedious perhaps, but no worse than say knitting a jumper. I have to admit that so far only a few cones have actually been fixed on, but even that would be helpful, though I've not tried it in anger.

<font size=1>*I've since heard it said that plaited rather than three-strand is preferable to avoid any tendancy to rotate.</font size=1>

 

[bryanglover]

Re: 3 stranded rope

andrew, another problem with 3 stranded rope, with cones plaited into each strand by 3 tapes leading from cones, under very high loads the rope can unwind. i have done some tests using heavy duty nylon ring clamps, to hold cone tapes to 3 stranded rope, seems to work ok. tapes are knotted on ends, to prevent slippage.
regards

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[AndrewB]

Re: 3 stranded rope

I've sewn, as well as spliced, the ends onto the rope.

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[Whoosh]

There are alternative drogues worth considering...

I'm a little disconcerted to see my U.S. Coast Guard being accepted as a foremost authority on drogue use aboard small yachts, as they have limited expertise in this area. The testing they did was limited and not comprehensive; this doesn't mean the Jordan drogue's results are invalid...just that there's far more to the story.

First, I would suggest that anyone wanting to make knowledgeable decisions about drogue selection should review the Drag Device Data Base (4th Ed. I believe) by Victor Shane. This is uniquely and exceptionally helpful because it includes anecdotal reports from a large assortment of vessel types, as well as theoretical info and supplier info. Personally, I think Earl Hinz offers the best single overview on drag devices (altho' it is conceptual and does not include first-hand reports); Earl spent many years cruising in the Pacific. The best theoretical + practical text IMO is VanDorn's Oceanography & Seamanship; VanDorn was both a long-term yachtsman and an oceanographer with UC San Diego. But despite expertise like these two authors offer, Shane's DDDB is essential reading.

Why are anecdotal reports critical? In a nutshell, the satisfaction one finds in a given drogue will depend on how it performs for the type of sea presented to the type of vessel one is aboard. IOW we're not talking about a 'drogue' but rather a 'system' (sea state and wave form; wind strength; vessel; drogue characteristics) which is variable over time and all inter-related. The USCG testing has verified that the series drogue will offer very little 'give' as wave energy impacts the vessel; far less than most other types of drogues. And we all know a storm can be short-lived and also relatively benign...or sustained and storm force. Previous sea conditions on top of which the storm's waves present themselves, depth of the water, length of time and strength of the wind...there are a lot of variables operating. Similarly, what's the aft end of the vessel like (since one must present that to the storm when using a series drogue)? Canoe stern? Big broad flat transom like Whoosh. How much reserve buoyancy does she have? How absolutely strong is the companionway, against which a boarding wave will strike in steeper seas with more wave energy? How watertight? How large the cockpit?

This is why Shane's review can be so helpful, as we can match up the effects of different drogue devices on vessels similar to our own and gauge what we think about their suitability for OUR use, not relative to some theoretical or average reference point. Personally, I think the best single drogue product to be used across a wide array of boat types and sea states is a Galerider. It's absolutely tough, lightweight and easily stored, not too expensive and, most importantly IMO, it allows the yacht to 'give' in proportion to the amount of wave energy presented to the vessel. But that opinion can also be tested against the empirical info available in the DDDB.

I suppose as in many other aspects of sailing, there is no simple 'fix' for a broad array of circumstances when it comes to drogues.

Jack Tyler
WHOOSH, currently lying St. Kat's, London

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[bryanglover]

and in the blue corner....

Jack,
I agree that anecdotal experience over time is best, but, there are about 1000 series drogues on blue water yachts today, i havnt heard any bad reports. I also believe that the lack of "give" is one of its strongest points, because the line is relativly tight, there is no build up of boat speed, as wave passes, so no damaging snap of the line when load is applied. There is a shock absorber effect, as drogue line extends from the stern in a sine like curve, straightening as force is applied, also nylon double braid has a lot of stretch.
as far as taking seas on the aft end, this is the most buoyant part of the vessel, the coast guard tested 3 different types of sterns over 5 years, i am not qualified to dispute the science.
If you have doubts about your companion way/cabin you dont need a drogue you need a new boat, CG suggests the jet from a high pressure fire hose is a adequate test.
anyway jack, would i be right in thinking you dont want a series drogue



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[AndrewB]

Thanks, that\'s very helpful. (nm)

nm

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[Whoosh]

Re: and in the blue corner....

Here's my reply, sent to Bryan by email...

Bryan, thanks for the note.

"...there are about 1000 series drogues on blue water yachts today, i havnt heard any bad reports."
Where have you looked? Perhaps a good place to start would be in the DDDB, or perhaps Hinz book. Not everyone is in love with them; they're just one method.

"as far as taking seas on the aft end, this is the
> most buoyant part of the vessel..."
I think if you'll reflect on that for a moment, you'll recognize that there are more factors involved than simply buoyancy...and in any event buoyancy varies greatly by design from one vessel to another. (There's a nice little Victoria 30 across from me at the moment, and I doubt her stern is where most of her buoyancy resides at the moment). When a drogue, as one author states it, "holds the boat for a punch", the aft end of the coachroof, the largest opening in the boat (companionway), and serveral broad, flat surfaces are all presented to the equivalent unyielding mass of several tons of wet cement hitting them at some speed...IOW its the least suitable area to take that loading, no matter how strong in an absolute sense it is built.

I guess my main point is that one needs to be thoughtful about drogue choices just like any other aspect of equipping a blue water boat. IMO and based on my research, which isn't limited just to USCG studies, a series drogue is more or less suitable depending on the nature of the boat, the storm and the crew. One size doesn't suit all...

Jack

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[AndrewB]

\"One size doesn\'t suit all\"

To be honest, I thought the idea was that it does. A larger, heavier yacht will need more resistance = a longer drogue, but that's all.

The film of the tank tests conducted by the Wolfson Unit shows that all types of hull shapes, including multihulls, seem to benefit from the series drogue holding the stern firmly to the direction of the breaking wave, resisting the yacht's tendency to lose grip, broach and be rolled. With a drogue, a yacht will resist broaching in waves over double the height. The drogue doesn't hold the yacht absolutely still, there is a certain amount of give as the breaking wave carries it forwards.

Clearly from the same film, pooping is highly probable. I guess you are right that if the yacht is not capable of coping with this, then a drogue might be a bad choice. But any serious off-shore cruiser ought to be: small cockpit, large drains, high bridge-head, tough washboards, sealed lockers etc being desirable. The experiments seemed to imply that within the normal limits of yacht design the amount of stern buoyancy shouldn't make a real difference to the decision to use a drogue, though plainly excessive stern buoyance will always increase the risk of broaching if the stern is held to the sea.

My understanding is that a drogue is less suitably used from the bows. The yacht will tend to fore-reach over it weakening its restraining influence. It will also tend to be thrown backwards by waves putting excessive loadings on the rudder, specially if unsupported. It is harder to deploy and recover the drogue from the bows.

I'd like to test out these theories, but a survival storm is not a time when one feels like experimenting!

 

[Whoosh]

Re: \"One size doesn\'t suit all\"

My note to Alan, sent to him by email but posted here as well...

Andrew:

"I'd like to test out these theories, but a survival storm is not a time when one feels like experimenting!"
Well, I surely agree with you there! In fact, this is a topic that abounds in opinion far more than experience, which is one of the difficulties in sorting thru it effectively.

I don't think I ever challenged the purpose of a drogue to hold the vessel against broaching or rolling, as you suggest. The issue, broadly speaking, is to what degree a drogue allows the vessel to give - for a given sea state - and to what extent it protects the vessel from giving too much. Series drogues are shown to resist or 'give' to a much greater degree than some others, e.g. the Galerider just to offer one alternative example, which is reported to perform in a more 'adjustable' manner without permitting the vessel to founder.

It's unfair to talk about parachute anchors being ineffective if placed poorly WRT the wave train, as this is certainly true for non-series drogues, as well. I think in all these discussions, to explore what works in what fashion, we have to assume proper deployment...otherwise any/everything is suspect.

"...though plainly excessive stern buoyance will always increase the risk of broaching if the stern is held to the sea."
To the extent stern buoyancy contributes to broaching, I concur. That is in fact one of the concerns with the series drogue - that as the sea state builds and the loading on the drogue increases, it yields less and less to the force, resulting in more force being delivered against the flat backsides of the vessel.

"My understanding is that a drogue is less suitably
used from the bows."
The conventional use of the terms as I understand them is that a parachute or sea anchor is deployed off the bow, while a drogue is used off the stern. When a vessel uses a bridle line in conjunction with a sea/parachute anchor off the bow, such as the Pardeys have advocated and shown in their videos, it would be incorrect to refer to that as a drogue. Drogues are for dragging.

Jack

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[bryanglover]

only god will save you

it seems we are all in agreement, that a drogue from the stern is best pactice in storm conditions. its down to what type of drogue. When i get to this point, i have to go with uscg because of the research and hard science, anything else is a hunch.
thats why people buy para sea anchors, they seem like a good idea.
the galerider is good, but has no thumbs up or down from a harsh institution. do you add a weight to yours, to keep it below wave action.

Drogue 1725 (of unkn. origin.)
1. Whale fishing. A contrivance attached to the end of a harpoon line to check the progress of a whale.
shorter oxford

regards
bryan




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