With a drogue deployed, a
well-designed and properly constructed fibreglass boat should be capable
of riding through a Fastnet type storm with no structural damage. Model
tests indicate that the loads on the hull and rigging in a breaking wave
strike should not be excessive.
There are three areas that
require special attention:
- The attachment fittings for the bridle of the drogue towline at the
corners of the transom must be capable of carrying 70% of the towline
design load. For a 7500 lb. displacement boat each fitting must be
capable of carrying 5300 lbs. Many yachts are equipped with a Genoa
track which runs aft to the transom. Such a structure, which distributes
load along the hull, could be provided with a special eye at the transom
for attaching the bridle.
If the nylon towline is led
through a chock instead of attaching directly to an eye, experience
suggests that chafing may occur even with good chafing gear installed.
Consideration should be given to the use of a short length of wire cable
running through a stainless steel chock before attaching to the nylon
- Many sailors are reluctant to deploy a drogue from the stern because
they fear that the boat may suffer structural damage if the breaking
wave strikes the flat transom, the cockpit and the companionway doors.
The model tests do not show this to be a serious problem. The boat is
accelerated up to wave speed and the velocity of the breaking crest is
not high relative to the boat. The stern is actually more buoyant than
the bow, and will rise with the wave. However, the boat may be swept
from the stern. The cockpit may f ill and moving water may strike the
companionway doors. The structural strength of the transom, the cockpit
floor and seat, and the companionway doors should be checked at a
loading corresponding to a water jet velocity of approximately 15
- When a boat is riding to a drogue no action is required of the crew.
The cockpit may not be habitable and the crew should remain in the cabin
with the companionway closed. In a severe wave strike the linear and
angular acceleration of the boat may be high. Safety straps designed for
a load of at least 4g should be provided for crew restraint. All heavy
objects in the cabin should be firmly secured for negative accelerations
and drawers and lockers should be provided with latches or ties which
will not open even with significant distortion of the hull structure.