Drogue

A drogue (also known as a storm drogue) is a device external to a boat, attached to the stern and used to slow the boat down in a storm and to keep the hull perpendicular to the waves. The boat will not speed excessively down the slope of a wave and crash into the next one nor will it broach. By slowing the vessel in heavy weather, the drogue can make it easier to control. A drogue is usually constructed to provide substantial resistance when dragged through the water, and is trailed behind the vessel on a long line. A properly functioning drogue should also prevent .

Most drogues are best deployed out of sync with the boat by one-half of the length of the prevailing waves; thus the drogue climbs a wave when the boat slides down a wave. Nylon rope is widely used for hauling drogues since it best absorbs the shock loading by stretching. However, new research indicates that using rope with less stretch accompanied by chain weight helps to maintain constant force on the deployment rode rendering storm drogue use more effective.

Weights such as chain are also employed to keep the drogue from breaching the surface of the water and skimming across the top. In addition, experienced boaters add a floating trip buoy so that the drogue can be deflated before recovery. The trip buoy line is a floating buoy attached to the top of the parachute cone which collapses the cone when pulled. In the case of series drogue lines, they are attached to the end of the line. Trip lines are especially helpful on series drogues because of their difficult recovery. Although the trip line concept is a derivative of the parachute sea anchor, evidence demonstrates that such a setup is not effective with the storm drogue.

While similar in design, the sea anchor is quite different in application from a drogue. The sea anchor is usually much larger, is intended to slow the vessel to a near complete stop, and is usually deployed off the bow (front) of the boat so that end is presented to the oncoming waves.

Speed-limiting drogues are single-element devices. They come in several varieties of canopy shapes that are circular in shape like a big round basket. Some are built with solid fabric while others are open in design to permit water to flow through them more readily. Holes or strips are usually cut in the drogue for stability, to reduce loads on the material, or both. Currently, the speed-limiting drogue is the most commonly used storm drogue with many designs available in the market place. See also drogue parachute.

...
Wikipedia