how to make a drogue or sea anchor

I have some strong fabric and an old singer sewing machine, said to be capable of heavy fabrics.
I want to make a couple different sized brakes. How should they be shaped?

 

The easiest is a couple of auto or truck tires towed astern with a VERY stout line.

No fabrication , no cost. Works great .

FAST FRED

 

Like this? Doesn't seem to slow him down a lot I think.

I am not sure whether a fabric sock, with "drawstring" closure at one end, and a 3 or more part bridle at the other, would collapse? It could have some pipe insulator foam along the upper front edge, and a weight at the bottom front edge. Couldn't that be pretty stable?

(pic from http://www.trim.no/images/artikkel/standard/bergemiddels.jpg)

 

The US Coast Guard has put forward a different approach. Trail from the rear a long line with many small 'chutes' sewn on. They have tested it too. Fairly damning of the big Parachute drogue. If I can remember the web-site?

 

Tough Issue

This is a tough one: there are a lot more opinions than experience out there. I will readily volunteer that I have an ear-bending volume of opinions, and I have done a substantial amount of offshore sailing, but I have NEVER used a drag device. -so, my comments are just theory.

I think that people will agree with the comment that the best storm device will vary depending upon the characteristics of the vessel, the weather/sea conditions, and the crew.

With that obvious declaration made, I can tell you where I've come out on trying to answer the same question: I go with the Jordan Series Drogue.

You can make one yourself, or you can purchase one at:

http://www.jordanseriesdrogue.com/

Here's some general drag device info:

http://seriesdrogue.com/coastguardreport/droguereport.htm

 

That babychute tail looks very neat! Can you explain to me how those little chutes are attached to the main rope so that I can make one?

 

sorry, I didn't "have time" to wade through the whole of the links before I posted. Great links! I think I know how to construct it now.
For continuity, here is the answer to my question:
http://seriesdrogue.com/coastguardreport/figure17.htm
Don Jordan answered me also immediately and gave more details.

 

Glad that the answer was available.

Since the load on any individual "pocket" will not be that great, the details of assembly should not be too critical and it's reasonable to take on the project yourself.

That said, I know I'm too much of a procrastinator and the drogue would live, half-completed, on my living room floor for months - I'll have the guys in Annapolis make one for me!

I'll be interested in your thoughts and experience. One of the questions that I haven't answered for myself is whether there's any meaningful value in rigging the drogue with a bridle - that is, whether a bridle-rigged series drogue would contribute meaningfully to maintaining the heading of the boat.

I think that Linda Dashew discusses making a series drogue in "The Offshore Cruising Encyclopedia" or "Survive the Storm".

There are also valuable references to the use of the series drogue and other storm devices in Allard Cole's "Heavy Weather Sailing", "Fastnet Force 10", and the several books on the '98 Sydney-Hobart Race, among others.

Best regards,
JPC

 

Drogues and sea-anchors

It's VIP to differentiate between devices intended just to slow the boat down, while still continuing to sail, and devices intended to STOP the boat.

The first group include 'towing warps', sometimes with tyres, anchors, conical drogues attached. This presents the stern to the following seas, which becomes problematic when the cockpit is regularly swamped by breaking seas. Catamarans with 'patio doors' are vulnerable to downflooding. Someone must remain at the helm, steering, hour after hour.

The second group utilises a much larger 'drag-generating' device, which grips a weight of seawater greater than that of the boat, while the bows are presented to the seas. A very long, 'elastic' nylon rode is used, which absorbs shock-loading, and ensures the drag device remains embedded in the body of a sea, two removed from the boat. A bridle arrangement is effective on a multihull, while less so on a monomaran. The idea is that the boat is stopped/'parked up', facing the seas, while everyone is below sheltering and resting.

Whatever system is chosen, it is essential that the gear used is well strong enough for the job, and is protected adequately from chafe. Loads imparted on the boat - and her fittings - are enormous.

The accounts of successful deployments stress this, while some accounts of unsuccessful encounters admit that the gear used was too small/too weakened by UV/chafed through/not strong enough somewhere.

There are lots of folk with strong opinions - and no experience - who haven't even studied the accounts of those who have serious and successful experience of survival storms using drag devices.

Try reading this stuff...

http://www.biggideas.com/sea-anchor/html/data.html

and 'Heavy Weather Sailing' published by Adlard Coles.

 

Controversial stuff for sure. I don't have any experience in more than 50kt, and we were sailing. One thing that tends to confuse my intuition a bit is that the water doesn't move a lot with respect to the ground, whereas the wind does. So eventually it does seem plausible that the boat will generally move to leeward with respect to the water, even with a huge sea anchor. Thus I would think that the bow should point downwind in order to have a steady yaw with the smallest drogue, thus lower loads. But as you point out some boats may not take this very well due to flooding of the cockpit etc. Jordan claims there has been no damage from using the aft-deployed series chutes.
Here is a quote from paratech backing up the idea that bow-deployed devices need to be draggier, and why they are needed (at least on some boats).

"Please Note: Although it is much easier to pull the stern of the boat into the seas(even with a smaller Sea-Anchor) we consider it unwise in heavy weather situations. Because 99% of present day boats are designed to take the seas on the bow, we likewise have designed our present day Sea-Anchors for use off the bow only. They are true offshore anchors and as such are not to be confused with speed-limiting drogues used off the stern."

Another situation may be if you have a multihull where you can raise the appendages. Then the bows, being sharpest, would be the most effective "feather", and the whole problem of going backwards likely diminishes. I experience this effect even in the little fat europe dinghy - it hates to be towed straight forward because of the sharp bow - but towing it backwards tends to be stable.

There is one thing I feel certain about in mooring, at sea or elsewhere, and that is the importance of stretch in the system, in other words to even out the loads over time. this does decrease the max loadings. The babychute tail looks like it can do this in an elegant way. I don't see any reason why one style of drogue should be limited to deployment from only one end of the boat. both styles could be sized to do either.

Don't talk to _me_ about procrastination!

 

Does anybody have an opinion on the size of drogue for a 20' cat with no mast? say 300-500 kg?

like I said, don't try to out-procrastrinate the pros.

 

JPC - Thanks for providing the links to the US Coast Guard's report on the series drogue. I had forgotten

No seriously - they have it covered. It is all there.:idea:

 

Caution

I would urge caution on those who would extrapolate from the 'US Coastguard' so-called test report, to use on real boats and real seas.

First, the report is dated 1987 and is written by a Mr Jordan - who has a vested commercial interest.
Second, the report confuses the different roles of a 'drogue' ( slows the speed of drift, while vessel continues ) and a 'sea anchor' ( vessel is stopped ).
Third, the large-diameter parachute sea anchor, used now by hundreds of cruising yachtsmen, is neither tested nor discussed. It is simpy ignored.
Fourth, the 'experimental' basis for the report's conclusions is a computer simulation model, and some measurements related to a small model boat in sheltered conditions. Hardly capable of scaling-up to survival storm conditions i.r.o a cruising yacht.
Fifth, no mention is made of the body of experience of the use of such devices which has built up over the decades, including that of the RNLI cox'ns who have used conical drogues in breaking seas, for all of the history of that service. N.B. The lifeboat crews use of drogues is restricted to speed- and broaching control, in the final approach to a harbour/bar where breaking seas are encountered. Elsewhere, the vessel's manoeuverability and bouyancy is sufficient.

By all means carry and use a Jordan Series Drogue system, or a small-diameter drogue. But, be aware of the limitations.

 

Caution

I would urge caution on those who would extrapolate from the 'US Coastguard' so-called test report, for use on real boats and real seas.

First, the report is dated 1987 and is written by a Mr Jordan - who has a vested commercial interest.
Second, the report confuses the different roles of a 'drogue' ( slows the speed of drift, while vessel continues ) and a 'sea anchor' ( vessel is stopped ).
Third, the large-diameter parachute sea anchor, used now by hundreds of cruising yachtsmen, is neither tested nor discussed. It is simpy ignored.
Fourth, the 'experimental' basis for the report's conclusions is a computer simulation model, and some measurements related to a small model boat in sheltered conditions - hardly capable of scaling-up to survival storm conditions i.r.o a cruising yacht.
Fifth, no mention is made of the body of experience of using such devices which has built up over the decades, including that of the RNLI cox'ns who have used conical drogues in breaking seas, for all of the history of that service. N.B. The lifeboat crews use of drogues is restricted to speed- and broaching control, in the final approach to a harbour/bar where breaking seas are encountered. Elsewhere, the vessel's manoeuverability and bouyancy is sufficient.

By all means carry and use a Jordan Series Drogue system, or a small-diameter drogue. But, be aware of the limitations.

These have been highlighted again recently by the published experiences of designer Richard Woods. A 'too small' drag device, set off the bows, fails to hold the bows directly up into the wind and seas. The result is that the bows fall off, the vessel drifting bodily downwind about beam-on - exactly what one is trying to avoid....

IMHO, one may set a drogue, or Jordan Series Drogue, off the stern and continue steering downwind at reduced speed ( seas will break into the cockpit ) OR set a large parachute sea-anchor off the bows and entirely stop the boat ( seas will break over the bows ). Either way, all the gear used needs to be well strong enough for the very substantial loads that will be encountered.

 

Please read the report. The reason for the report was stated as:

OK - so they experimented with something that just might be easier to use - deploy and then put away again -. not just for professionally trained Royal navy coxwains in 50knts and 4m seas - but us bumbling cruising folk.

They examined the differing types and came to the conclusion that the Parachute would need to be very big and 'could' become difficult to successfully engage (remember us bumblers). Why not shrink the size - place as many cones as to equal the volume of a Parachute and place it on ONE line to help deployment.

They made one up - yanked it around the sea in a 42 foot Coast Guard Vessel to see if it would stand up.

The bloke started selling the 'jordan series drogue' after the report - it was not developed before the report.

I have read many stories of parachute anchors failing and sailors failing to use them properly. I can now use this report to determine just how long my drogue needs to be to stop my boat in the water. A hell of an easier thing to use. Thank you US Coast Guard.