Originally Posted by SaltyMonkey
That is absolutely NOT correct about the difference between a sea anchor
and series drogue
. A sea anchor
SHOULD allow elasticity and movement through a wave by the bow just as you are proposing a series drogue
does in your explain. You need to make sure you choose the correct size of sea anchor
This elasticity is what results in damaged rudders and parted lines while riding to a sea anchor
, and are two of the problems that the series drogue was designed to fix. The third being large damaging forces transmitted to the boat. Evan's website reviews
that issue. Roth's book gets into that also.
People who have used both the sea anchor and the series drogue report radical differences in the ride, all from how the braking effect differs between the two. The sea anchor brakes much harder, thereby transferring much larger loads to the boat. The essence of the series drogue is the reduction in forces to the boat. The cones slide through the water much more than any nylon rode can stretch, yet brake enough to prevent pitchpoling
Originally Posted by SaltyMonkey
In either case, a passive defense from the stern of a boat is highly dangerous unless your boat is designed in means to be defended in this way, and even then it is suspicious. The stern of a boat (incl cockpit), unlike the bow, is not designed to take on breaking waves at sea as you suggest; moreover the mass is not distributed to the bow of the boat and the windage correct to be able to make the stern of the boat face into the waves automatically and without risk of massive swamping or rolling. This is especially true in a cross sea. It's irresponsible to suggest otherwise.
I agree to a certain extent; nor have I ever suggested otherwise. But many boats have used the series drogue with great success, greater success than sea anchors in fact, which suggests that it can be used with many boats. I'm fortunate to have a steel
boat that offers great strength, even in the stern.
Here are some reports about the use of the series drogue: http://www.jordanseriesdrogue.com/D_2.htm
Here are the designer's comments about your concerns
Series Drogues and boat design
With a series 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
in a breaking wave strike should not be excessive. 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 fill 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 ft./sec.
When a boat is riding to a series 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