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Encyclopedia > Drogue

A drogue is a device to slow a boat down in a storm so that it does not speed excessively down the slope of a wave and crash into the next one. 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 B-52H Stratofortress from the 5 Bomb Wing deploying its drag chute for landing Apollo Command Module splashdown A drogue parachute is a type of parachute designed to be deployed from a rapidly moving object. ...

Contents

Use

Most drogues, are best deployed out of sync with the boat by one-half of the length of the prevailing waves, so that the drogue climbs a wave as the boat slides down a wave. Nylon rope is widely use for hauling drogues as it absorbs the shock loading best by stretching. For other uses of this word, see nylon (disambiguation). ...


Weights such as chain are usually 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 bouy so that the drogue can be deflated before recovery. The trip buoy line is a floating bouy 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.


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. A sea anchor is unlike a normal anchor, in that it is not made of metal and does not dig into the sea floor. ...


Parachute variety

Drogues come in several varieties. Of these the parachute variety is the most common commercially manufactured type. A parachute drogue is generally constructed of heavy flexible material in the shape of a cone. Holes or strips are usually cut in the drogue for stability, to reduce loads on the material, or both. Unless two such drogues are deployed in series, the length of the tow line must be adjusted as the distance between the waves changes.


Series drogue lines

Retired Aeronautical Engineer Don Jordan is widely agreed to be the inventor of what are now known as series drogues. However, before his invention, numerous mariners had experimented with pulling several large drogues in series. Jordan expanded upon this idea, and affixed a very large number of small parachute drogues upon a nylon rope. The large number of smaller drogues results in there always being a drag force on the line; it does not have to be adjusted to be in phase with the waves as the drag is spread out over many waves. Because the drogue line is prevented from becoming slack there is no jerking or snapping of high loads on the line. This reduces damage to deck fittings and reduces the chance of breakage.


The series drogue is advantageous in that it does not have to be adjusted during a storm. This is an excellent feature as sea conditions requiring a drogue are usually hazardous to be on deck. However, recovering a series drogue is difficult, but it can be winched in on sheet winches if the cones are small enough to travel around the winch drum without jamming[citation needed]. They are more difficult to inspect and maintain because of the many working surfaces. The series drogue is currently made by 2 manufacturers, one in Australia and one in the United States.


Homemade drogues

Studies undertaken by the U.S. Coast Guard have indicated that homemade drogues made of old tires, long lengths of chain, etc. are not effective in slowing most vessels. Old tires may skim along the surface at storm speeds. Extremely long lengths of chain are required for any appreciable drag effect from chain alone. Nevertheless, these drogues continue to be used.


References


  Results from FactBites:
 
Drogues (855 words)
There are many references to drogues and sea anchors in the literature of the sea, going all the way back to ancient times.
One very experienced sailor has developed a system of three drogues streamed simultaneously: a spinnaker pole and small anchor at 200 feet, two tires and medium anchor at 300 feet, and two tires and a heavy anchor at 400 feet.
As part of this report it is important to consider the question of why drogues have not been developed and accepted as a standard item of emergency equipment up to the present time.
Pilot Attached Drogue (2038 words)
Unlike the keel-stabilized drogue, this canopy is unstabilized and will bump around in flight, which can be annoying, but the effect is minor and well within the scope of the landing conditions that we all have to deal with in hang gliding.
The pilot-attached drogue chute is intended to be a convenience, not an emergency device, since it cannot be relied upon to deploy with complete reliability or promptness in critical situations.
The drogue can be attached to the harness anywhere in the center back of the harness, but the easiest setup is to attach one end of chute bridle (the Fastex Clip) to the lower end of the main harness suspension webbing where it meets the main body of the harness, or thereabouts.
  More results at FactBites »

 

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