The two conventional drogue
configurations are the cone drogue and the parachute drogue. Both types
have been used successfully in a variety of applications. A third type of
drogue called a series drogue has been developed as part of this
investigation. The series drogue is intended to provide near optimum
performance under storm conditions and to avoid some of the problems
encountered with cone and parachute drogue.
The series drogue offers the
following desirable features:
- If pre-rigged and coiled down into lazeret, the drogue is simple and
safe to deploy under difficult storm conditions. The boat, under bare
poles, will be either running off lying ahull. The anchor can be slipped
over the stern and the line payed out. The drogue will build up load
gradually as it feeds our.
- It is almost impossible to foul it or entangle it enough to make the
- The drogue ride-s beneath the waves and is not affected by the
following sea even f a wave should break in the vicinity. There are
cases on record where a cone drogue has been pulled out of the face of a
following wave, and even instances where the drogue has been catapulted
ahead of the boat. It is difficult to weight a cone or parachute drogue
so that it will ride at a sufficient depth to avoid the wave motion. As
discussed previously in this report, a weight causes the drogue to
collapse when the towline goes slack.
- When the boat is in the trough of a large wave, the towline tends to
go slack thus permitting the boat to yaw. With the series drogue, the
anchor sinks pulling the drogue backwards and taking some of the
unwanted slack out of the towline.
- When a breaking wave strikes, the drogue must catch the boat quickly
to prevent a broach. The series drogue, since some of the cones are near
the boat where towline stretch is low, will build up load faster than a
conventional cone or chute at the end of the towline. A computer study
shows that two seconds after wave strike, the series drogue will develop
40% more load than an equivalent cone or chute. Similarly, if the
breaking wave strikes at an angle to the towline rather than directly
astern, the series drogue will build up load much faster than the
- The series drogue is durable as demonstrated by the testing
described in this report. The load on each individual element is low. No
single failure can make the drogue ineffective.
- The series drogue can double in function as a spare anchor line and
can use the boat's regular anchor as a weight. All 90 cones weigh only