APPENDIX F of the Offshore Special Regulations

TERMINOLOGY
The term "drogue" generally means a device dragged from the stern of a vessel which continues to make steerage way through the water but at reduced speed. The term "sea anchor" generally means a device streamed from the bows of a vessel practically halted in the water by the action of the sea anchor.

LIFERAFTS
Every liferaft has a sea anchor supplied as part of its equipment. A sea anchor is critical to the safe use of a liferaft and dramatically reduces the chance of liferaft capsize. Its secondary function is to limit drift. A spare sea anchor may be carried in a grab bag. Sea anchors in liferafts should comply with ISO 17339 and the opportunity should be taken at service intervals to ensure this.

DROGUES ON YACHTS
A number of research programmes have been conducted including one for the RORC by the Southampton University Wolfson Unit. In tests drogue deployment repeatedly prevented typical yacht forms from being slewed sideways and rolled in heavy breaking seas.

Deployment of a drogue over the stern means that heavy water will break over that part of the yacht, so all openings must be properly secured shut.

A "series-drogue" invented by Donald Jordan has the ability to continue to provide drag even if part of the device is "surfing" under a wave crest.

SEA ANCHORS ON YACHTS
The most common form of sea anchor for yachts is the "parachute" anchor developed from aviation parachutes. Specialist manufacturers have accumulated much data to demonstrate the effectiveness of the device which can enable a vessel to take seas bows-on, reduce drift to the order of one knot, and resist capsize.