Much has been written about storm survival tactics, and much of it is about the different systems of sea anchors. Sea anchors have the function to enable the boat to hold position in a storm, and keep the hull in a direction towards the waves to minimize the chance of serious damage due to breaking waves.
There are basically two main schools of thought, each with their own supporters. One camp favours deploying a parachute type sea anchor from the bow, the other system consists of a series of small cones deployed from the stern. I will not go into all the pro’s and cons of either system, but refer to the website of Melbourne based Bryan Glover, where this series drogue system has been documented in detail.
I will buy a series drogue system for ‘Waratah’ from Bryan, once I am ready to sail. The system for my boat will consist of 139 nylon cones, spread out over almost 100 meters.
I asked Bryan to send me something for my blog, and he was kind enough to write this article about his own boat ‘Asgard’.
I bought Asgard in May 2000, she is a sloop rigged 28ft Swanson, 10 ft
beam with a 20Hp Bukh diesel, built in in 1982, 18mm fiber glass,
built like a tank. Asgard was in and I planned on sailing her
home to , the route was much the same as the 1998 Syd – Hobart
disaster except I would turn right into Bass Strait and follow the 40deg
south line. I had some dingy sailing experience but no blue water, and
since I intended going solo I needed something to stop my eye from
Voss, and David Lewis “Ice Bird” relied on drogues as do retired old
salts you find mumbling obscenities in boat yards, problem fixed, heavy
warps, or large cone or Delta drogue or drogue chute or para drogue or
Galerider or tires or drogue stones, they all have vocal supporters
which is perplexing because like all single unit devices logic dictates
the tow line will go slack when the vessel is in a tough, or pull out of
the face of a wave and kill you (RNLI life boat team) or tumble forward
in a breaking wave causing slack in the line and possible broach.
Trucking from was even money, until I read the US Coast guard
report CG-D-20-87 all about the series drogue and its ability to save a
vessel in a once in a life time wave strike, this put a spring in my
step, my eye began to perform as designed and I started eating again.
The Jordan report told me for Asgard’s 4500
Displacement I needed a 100 cone series drogue, with a 10 to 15 kg
weight on the end that would sink when the vessel was in the trough of a
wave preventing slack developing in the line. I would travel through the
storm at 0.5 to 6 knots averaging 1.5 knots. The drag produced by the
drogue would be:- Volume (0.27) x no of cones x speed in knots Squared =
drag in lbs
@ 1 knot drag = 12 kgs
@ 2 Knots drag = 48 kgs
@ 3 Knots drag = 108 kgs
@ 5 Knots grag = 300 kgs
@ 6 Knots drag = 432 kgs
@ 10 Knots drag = 1200 kgs
@ 15 Knots drag = 2700 kgs
Donald Jordans research and development of the drogue giving specific
data which allows us to construct drag to a given displacement, not
relying on a single unit, but spreading the stress loads over 100 or
more units was survival poetry.
I had a wonderful sail home, nearly hit by a ship off Port Kembla, blown
semi out of control into , ran aground in mud at Eden, spent 3
nights at Refuge cove Wilsons Prom, managed to pump all 200 liters of
fresh water into the bilge, ran out of gas, spent 5 blissful nights
sheltered behind Erith Island in Kent group, fishing, reading, cooking
on the beach and exploring this uninhabited Bass Strait island group.
When I glided into my berth in and tied up I felt blissful, I
had completed a journey, overcome a fear. I didn’t have to use the
drogue on that trip but I had in my own way.
Last but not least I want to share this picture about Bryan’s special ‘dry-testing’ method for series drogues.