Jordan Series Drogue

What is it ?

Performance at Sea


Design Loads and Attachments

Launching and Retrieval

About the Designer

About the Builder

Storm Waves

Wave Science

"The Loss of the Winston Churchill"

Coast Guard Report CG-D-20-87

Mooring and Anchoring

Printable Versions

Soundings-May 2006

Ace Sailmakers: Jordan Series Drogue Pricing and Order Form


We now have enough information that we can apply the same analyses to the Winston Churchill.

We can estimate the speed of a breaking wave (but not a non-breaking wave) if we know the height of the wave. The breaking wave that destroyed the Churchill was estimated by several observers to have a height of at least 45 ft. Such a wave would be moving at about 30 mph. Therefore, when the boat had been picked up by the wave it would be moving at that speed..

As the Churchill slid down the face of the wave on its side, there would be very little friction or drag, because the water supporting the boat would be moving at the same speed and would accelerate with the boat. With no friction the boat could reach a speed of 67 mph by the time it reached the trough. If we assume only half of this speed increase, the boat would strike the green water in the trough at over 50 mph.

This velocity is equivalent to a free fall from over 70 ft. This clearly explains the sequence of events which destroyed the Churchill. A boat striking green water at this speed can incur a force of over 200,000 lbs.

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Winston Churchill With Drogue
It is not feasible to design a drogue which will prevent a boat from being picked up by the wave and carried up to wave speed. The loads would be prohibitive. Therefore it is necessary to design a drogue which is capable of decelerating the boat to a low speed before it plunges into the trough.

Fig . 4 shows the Churchill in the trough of a 45 ft breaking wave. A series drogue has been deployed and the boat is dead in the water. The wave face is moving toward the boat at over 30 mph. The drogue device consists of 164 5in. diameter cones concentric with the towline and attached to 348 ft.of double braided nylon line tapered from 7/8 to ¾ to ½ in.diam. A 30 lb. weight, usually a length of chain is attached to the end.

Fig. 5 shows the boat as it reaches the wave face. A heavy boat such as the Churchill is not thrown ahead of the wave but is caught up by the wave and brought up to wave speed. The loads on the boat when struck by the crest are not high enough to cause damage. The boat rides up the face and is near wave speed when struck by the moving water at the crest. In the more than 15 years that the drogue has been at sea, no boat has ever been damaged. In particular the rudder, transom, cockpit and companionway doors have all been unscathed.

At the position shown in Fig. 5, the drogue has picked up a load of approximate 5000 lbs.

This is sufficient to avoid yawing and broaching but not sufficient to prevent the boat from being driven up to wave speed.

Fig. 6 shows the Churchill surfing down the face of the wave. The crest has broken and the surface water is moving with the wave. Without a drogue the boat would accelerate rapidly. However, at this point the drogue has straightened out and is reaching the peak load, approximate 25000 lbs or half the displacement of the boat. The boat now decelerates and reaches the trough at a moderate velocity and with little roll or yaw.. No high loads are imposed on the hull or rigging.

Fig. 7 shows the Churchill without a drogue impacting the trough at a speed of over 50 mph. This is why the crew reported that "It felt like we had struck another boat".

The wave characteristics discussed here and shown on these figures are taken from a computational fluid dynamics simulation. Although actual storm waves will have local surface variations, the energy level and dynamic behavior of large waves such as those that struck the Churchill are now well understood and predictable for engineering purposes.

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Jordan Series Drogue  | What is it?  | Performance at Sea | TechnologyDesign Loads and Attachments | Launching and Retrieval | About the Designer | About the BuilderStorm Waves Wave Science | "The Loss of the Winston Churchill" | Coast Guard Report CG-D-20-87  | Mooring and Anchoring | Retrieving The Drogue | Printable Versions | Soundings-May 2006| Ace Sailmakers: Jordan Series Drogue Pricing and Order Form

If you have any comments or questions on drogue sales or configurations, please email them to or call us at (860) 739-5999. On drogue design or technology, please email them to or call at (860) 633-1702.

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Trademarks cited are the property of their respective owners. Last modified: February 2, 2007