File S/M-14, obtained from Walter Keintzel, Monterey, CA. - Vessel name Deanna, hailing port Monterey, "Carol" double-ender designed by Chuck Paine, LOA 24' 6" x LWL 20' x Beam 9' x Draft 3' 6" x 2.7 Tons - Full keel - Sea anchor: 9-ft. diameter BUORD on 300' x 1/2" nylon three strand with 1/2" galvanized swivel - Deployed in deep water off the central coast of California in low system with winds of 30 knots and seas of 10 feet - Vessel's bow yawed up to 80° - Drift was about 7 miles during 11 hours at sea anchor.
Victor Shane had the opportunity to take a close look at Deanna when she was moored in Santa Barbara harbor. This little pocket cruiser has a flush deck, with very low freeboard and a large full keel beneath. When Deanna is lying a-hull she is more or less anchored to the surface of the ocean by virtue of her big keel alone. Her rate of drift is further reduced because of her low freeboard. In general a yacht has to drift, to tug at a sea anchor, to cause it to fully inflate and function properly. In 60-knots of wind the same BUORD would have done a better job on this boat. A much larger parachute, say a 24-ft. diameter military chest reserve, would likely have pulled Deanna's bow up much higher into the wind as well, even in the given 30 knots. Here is a transcript of the feedback obtained from Walter Keintzel:
Location was 55 miles true west of Pt. Sal, measured by the Loran. I don't recall the barometer reading, but it was "normal." Don't recall the wave length & period, because when I deployed the sea anchor at 20:00 hrs. I was very, very exhausted & numb.
We lay at 80° to the nylon rode - almost parallel to the seas. I think this is because my flush-decked boat got lost in the troughs - not enough windage! With a riding sail on the back stay, I think it would work. As it was, it wasn't too bad.
Mainly the anchor kept me in place for a stormy night, and kept my physical condition from deteriorating to the point where I needed to call the Coast Guard. Next day I ran into Morro Bay for rest & repairs.
I'm very grateful for the parachute anchor. It was easy to deploy, but next time I'll certainly use a 300' trip line. Retrieval was like pulling a VW for fifty minutes!
File S/M-11, obtained from Harley L. Sachs, Houghton MI. - Vessel name Gamesmanship, hailing port Houghton, Venture 222 sloop, designed by Roger MacGregor, LOA 22' x LWL 18' 6" x Beam 7' 4" x Draft 4' 6" x 1 Ton - Centerboard swing-keel - Sea anchor: 12-ft. Diameter Para-Tech on 100' x 3/8" dia. nylon three strand rode, with 5/16" stainless steel swivel - No trip line - Deployed during passage of frontal trough in shallow water (7 fathoms) on Lake Superior with wind gusting to 20 knots - Vessel's bow yawed 10° with the swing-keel down and 45° with the swing-keel fully raised.
Way back in June 1988 Victor Shane sent a letter to the editor of Cruising World Magazine, asking for feedback on sea anchors and drogues. Mr. Harley Sachs read the letter and responded with the following feedback:
For your database: Vessel, MacGregor Venture 222 sailboat, swing keel, transom hung spade rudder, LOA 22 feet, weight about 2,000 lbs. Conventional wisdom (Chapman and the boating supply catalogs) suggested a 30-inch conical drogue sea anchor. This does not work with my boat.
My wife and I decided to test this equipment on a breezy day with four-five foot waves on Lake Superior. I launched the 30-inch cone from the bow on about fifty feet of line and lowered all sail. The boat assumed a position with the seas abeam and would not face into the waves no matter what the rudder position was. With the sea anchor shifted to the stern, the result was the same. The motion of the boat was violent and I could hardly move about on deck.
I hoisted a small riding sail on the back stay. This had an immediate, remarkable damping effect on the boat's motion but did not cure the beam-on attitude of the boat to the seas. The 30-inch conical drogue was pronounced a failure.
Sachs turned out to be a multi-faceted sailor who was, among other things, writing a book on nautical humor (Irma Quarterdeck Reports, Wescott Cove Publishing, 1990). Shane mentioned the similarity between his disappointing experience with the small cone and those documented by Adlard Coles in Heavy Weather Sailing, and then asked if Sachs would consent to trying out a 12-ft. diameter parachute sea anchor. This was to be a "controlled experiment" - same boat, same conditions, but a much larger sea anchor. He agreed, and Shane sent him the sea anchor. Three months later he tried it out in similar conditions and sent back the following report:
Subject: Test of 12-ft. diameter para-anchor. With westerly winds gusting to 20 mph after the passage of a cold front, we motored offshore to a point outside the Lower Entry harbor on Keweenaw Bay of Lake Superior. With the engine shut off we drifted about 1 knot downwind with the wind and waves off the stern quarter, the same attitude I experienced when unsuccessfully testing my 30-inch conical drogue.
About a mile offshore, in about forty feet of water, I set up the 3/8" laid nylon rode to launch the para-anchor.... As instructed, I launched the float first, which functions as a pilot chute, drawing the para-anchor away from the boat as the boat drifts downwind. This could hardly be easier, for the chute slid overboard and in two or three minutes filled beautifully. Once it filled, it stuck in the water almost like a post and the Venture 222 bow came right up into the wind exactly.
With the keel down the Venture did not yaw more than 10°. With the keel retracted, there was 30°-45° of yaw, as the Venture bottom has almost no lateral resistance with the keel retracted. Rudder was tied amid-ships. When retrieving the sea anchor, one cannot pull the anchor to the boat. One pulls the boat to the anchor, and that takes strength. I'm glad it wasn't a three ton vessel! Once I could reach the parachute strings, it was dead easy to spill the water out and haul it aboard. Took no effort at all, pulling one string. Once spilled, the para-anchor is a limp sack.
We did drift slightly with the anchor. In six minutes the bearing on the lighthouse half a mile away had shifted by ten degrees.... In spite of the holding power, the para-anchor is in a fluid, and the force exerted against it will cause it to slip through the water.
Apart from showing the improvement that can be expected with the use of sea anchor that is large enough, this file reveals something important about centerboards and swing keels as well.
It was previously thought that sailboats would yaw less at sea anchor with their centerboards and keels raised. Not so. At least not on this boat. Apart from tripping on the rudder as the boat surges backward, the CLR moves aft as well. With the CE now so far forward the bow will tend to yaw excessively. When the swing keel is again lowered, however, the CLR moves closer to the CE and the wind doesn't have the same lever. Notwithstanding, boards - and swing keels - should NOT be lowered all the way down in storms.
CAUTION: Lowering board/s and keels, or lowering them all the way, may give the yacht something to trip over in life-threatening storms. By and large, and as an important rule of seamanship, boards and keels should be raised in heavy weather. Or at least raised enough so that the yacht can "slip-slide," and not have a large appendage to hang up on and trip over.
File S/M-3, derived from writings of Lin & Larry Pardey - See article on "Heaving To" in August '82 issue of Sail Magazine, also pages 268-274 of Seraffyn's Oriental Adventure (W.W. Norton & Co., 1983) and the Pardeys' book entitled Storm Tactics (Pardey Books, 1995) - Vessel name Seraffyn, pocket cruiser, built by Lawrence F. Pardey, LOA 24' 7" x LWL 22' 2" x Beam 8' 11" x Draft 4' 8" x 5 Tons - Full Keel - Sea anchor: 9-ft. diameter Naval Ordnance (BUORD) parachute on 250' x 5/8" nylon three strand rode with Pardeys' own bridle arrangement & 3/8" galvanized swivel - No trip line - Deployed in the Gulf of Papagayo off Mexico and in the North Pacific during storms with winds of 40-70 knots - Bridle arrangement held the bow 50° off the wind - Drift was estimated to be about 5/8 of a knot.
Blue water veterans Lin and Larry Pardey have been using para-anchors since 1970. The one they used on Seraffyn was BUORD MK 2 MODEL 3. This parachute is government surplus and has been in use by fishermen for decades. The canopy is fabricated from heavy, nylon mesh material and it has sixteen shroud lines of 1000 lb. Dupont braid. Patrick M. Royce, author of Sailing Illustrated, did a series of tests on this parachute in 1969 and nicknamed it Two Pennant Storm Anchor (see page 157 of Royce's Sailing Illustrated).
Your author refers to these parachutes as "BUORDS" because they were originally developed for anti-submarine warfare use by the Navy's former BUreau of ORDnances - now Naval Sea Systems Command. Carrier-based S-3 Viking aircraft use such small diameter, heavy gauge parachutes to deliver torpedoes and other ordnances from the air. On page 269 of Seraffyn's Oriental Adventure the Pardeys show two photographs of the BUORD MK 2 MODEL 3. There is also a picture of Larry Pardey holding one up on page 36 of Storm Tactics.
In their original article in SAIL, Lin and Larry reported using this para-anchor in conjunction with a steadying sail in the Gulf of Papagayo (off Mexico) in gale force winds. The steadying sail would luff and flog violently as the boat was frequently pulled head-to-wind. Then it would fill and the head of the boat would fall off. This cycle would repeat itself once every four or five minutes - an uncomfortable and noisy affair. So Larry Pardey later rigged up an adjustable fairlead that kept the bow some 45-50° off the wind, at the same time causing the triple-reefed main to fill quite nicely and dampen the roll. This made the boat heel and lie much more comfortably. As a bonus, Larry found that in this attitude (45-50° off the wind) the boat would "scrape her keel" as she slid slowly downwind, leaving in her turbulent wake a significant "slick" that smoothed the seas, lessening their effect on the boat and gear. "You would be amazed at how this slick breaks down waves and steals their power," wrote the Pardeys to your author. Here is an excerpt from subsequent correspondence (reproduced by permission):
We have a preference for the BUORD surplus chute because 1) it is heavily built, with shrouds on our's almost strong enough to lift Taleisin, 2) it can be purchased quite inexpensively second hand, 3) as it is heavy weight fabric it does not have a tendency to fill with wind when you are deploying it, 4) we have used it since 1970 without problems, and finally, 5) because its fabric stretches when unusual strains come on it, the fabric becomes porous and lets some water sieve through, this absorbs shock loads.
Add this to the stretch of the nylon anchor line and we feel that the catenary curve-effect of chains or weights is redundant. We prefer a dead simple system - no floats, no trip lines, no catenary chains. We are also concerned about the move to bigger and bigger chutes. The bigger they are, the harder they are to store, handle and use. We are not sure they stop drift much better - once a chute is 8 to 15 feet in diameter, the drifts recorded by us on our boats, and during tests with modern sailboats off the Cape of Storms [South Africa], showed that the drift rate with the relatively small BUORD chute was about the same as that listed throughout the Drag Device Data Base for boats using much larger chutes, a drift of between 5/8 and one knot. For monohulls laying at a hove-to position, a smaller chute, combined with the considerable drag of the keel, as shown in the diagram, will produce a wide, effective slick. We can see that multihulls laying head to wind would need the largest chute possible as only the sea anchor is working to create a protective slick.
A further thought on chain. As chafe in the bowroller or fairlead is a major concern with any nylon anchor rode (onshore or offshore), we have considered using a 30 foot length of chain for the inboard end of the rode. But as we have not yet done so, we can make no actual comment on this idea.
Sea anchor rode is led off the bow. Pennant line from cockpit winch causes the bow to lie 50° of the wind. Storm trysail is set and the tiller lashed to leeward. As the boat is pushed downwind her keel begins to shed vortices, which gradually merge into a turbulent field upstream. The intense mixing effect of this turbulence will tend to cancel molecular rotation - the stuff that waves are made of. Note that this strategy requires square drift. The boat must not forereach - sail out of her protective "slick." The Pardeys have practical suggestions for ensuring that it does not in their book, Storm Tactics - required reading.
To what extent does the turbulence generated by the square drift of the keel affect the shape and ferocity of the waves? The "slick" mentioned by Lin and Larry Pardey is not to be confused with the superficial effects of oil on the surface of the water. It is a more profound phenomenon. It has to do with the turbulent field created by a succession of vortices, technically known as the Von Karman Vortex Street.
Vortices are eddies, created by the motion of irregular shapes in fluids. They flow away from the boundary layer and gradually merge into a homogeneous turbulent field in which the turbulence in one part of the field is the same as that in any other part.
Since non-homogeneous ocean waves are created by the orbital rotation of water particles, anything that interferes with that rotation can have an effect in a seaway. Logically, and if the interference is great enough, the resulting turbulent field can de-stabilize - or at the very least smooth down - the wave formations directly ahead of the boat.
Using Parachutes, Sea Anchors and Drogues to Cope with Heavy Weather – Over 130 Documented Case Histories