Disclaimer: This is an account of a single
deployment of a JSD, with conclusions drawn by a troubled mind. As such, it is presented not as dogma, but as a basis for discussion.
We recently had occasion to use our JSD in force 9 conditions off the coast of Japan
. We were eastbound 5 days out of Yokohama when we were overtaken by the remnants of TS Leepi, which had become a fast-moving extra-tropical cyclone. The wind
was in the high 40's, gusting into the mid 50's with seas of approximately 5-7 meters. The boat was under autopilot
, our speed was 9-11 knots under bare poles and, although an occasional breaker would push the stern around a bit, the boat was handling the conditions comfortably, taking the seas in a dignified manner off the starboard quarter,. However, as the wind
continued to build, the boat began to plane on the gusts. The autopilot
continued to handle it well but the sun had set, the wind was building and it was time to slow the boat. We had pre-rigged both the JSD and parachute anchor
prior to leaving Japan
. I chose to deploy the JSD rather than the parachute anchor
as we were traveling in the same direction as the weather
with 4,000 miles of sea room and I expected the gale to pass by us quickly. Deploying JSD off the stern was simply a matter of dropping the chain overboard
. The drogue
ran out smoothly and behaved brilliantly, slowing the boat to 3.5 – 4.5 knots as the stern lifted gently over the seas. We turned off the autopilot and settled in. The gale continued for 2 hours then began to abate. By sunrise the wind had dropped to a light breeze and we retrieved the drogue
and carried on.
A few points are worth commenting on.
First, the forces exerted on the boat by the drogue were truly impressive. The pull from the JSD, while gradual, would cause us to stagger if we were not holding on.
Second, one often hears that a disadvantage of the JSD is that they are difficult to retrieve, but in this particular case we found it fairly easy. Before deployment I had rigged a long pendant to one of the bridle
arms. When it came time to retrieve the drogue we simply led this line forward to the bow roller, released the bridle
arms and motored slowly forward, pulling the drogue in by hand. The whole operation took about 15 minutes.
Third, and most surprising, was that when we retrieved the drogue in the morning we found that most of the cones had frayed badly, particularly those closest to the boat that, presumably, were subjected to the most stress and turbulence,. The leading edges were most affected, but the trailing edges were frayed as well. This was after only 2-3 hours of gale force conditions.
Fourth, I was a bit surprised at our speed while lying to the drogue. After reading many accounts of monohulls lying to a JSD I expected our speed to be around 2-3 knots. We averaged 4 knots, which may have contributed to the rapid degradation of the cones.
Things I will do differently in the future;
I will replace the nylon rodes with Dyneema
(SK-75). I believe the elasticity of the nylon rode
allowed the boat to acclelerate on the gusts before all the cones were brought into play and the boat could be slowed. Many believe the elasticity of the nylon is a crucial component of the drogues function, providing elasticity and decreasing shock loads as with a parachute anchor. However, in the case of a drogue, I believe that the elasticity of the nylon is unnecessary as the resistance of the drogue is limited by it's smaller surface area in comparison to a parachute anchor. Further, as the boat is moving the rode
is under constant tension so there is no shock loading even as waves strike the stern. In addition, it is possible that an elastic rode may ultimately result higher loads on the boat. Recalling that Force = Mass x Velocity squared, the loads multiply very quickly if the boat is allowed to accelerate. I believe that, in our case, this contributed to the fraying of the cones closest to the boat. I will likely keep the nylon bridle arms, but only as they serve double duty as anchor bridles and docklines. (As an aside, our 22mm, 3 strand nylon bridle arms were both badly hockled. I will replace them with double braid nylon in the future.) Weight is another consideration. Our drogue consists of 167' of 3/4” and 167” of 5/8” nylon double braid, with 45' bridle arms and 20' of 10mm chain attached to the end. This is very heavy, bulky and clumsy to move around deck
. When wet, it is more that I can manage without pain medication. Dyneema
would be far less bulky and much lighter, particularly as it does not hold nearly as much water
as nylon. When sized for equivalent strength, Dyneema single
braid can be found for roughly the same price
as Nylon double braid..
I will also consider adding more cones. We used 150 cones, the recommended number for a multihull
our size, but I feel that the recommendations for multihulls, with their greater windage, may be not be conservative enough. We have about average windage for a bridgedeck saloon
cat our size, but the JSD still allowed an average speed of 4 knots. This speed may have contributed to the rapid fraying of the cones.
When we rebuild
the drogue we will reinforce the edges of the cones. This could be done either by hemming or gluing a strip of cloth to the edge with GM 5200 or similar. It is possible that a simple bead of 5200 along the edge could be sufficient. My wife put ours together from a Sailrite
kit, which uses lightweight ripstop polyester for the cones without reinforcement. Had the gale lasted longer, it is conceivable that the cones could have failed completely. This gale occurred in the first week of a five week passage
and, had we needed the drogue again, it would not have been available.