34' x 16' x 5.5 Tons
9-Ft. Dia. BUORD
Force 9 Conditions
File D/C-3, obtained from Thomas W. Kintz, Groton, CT. - Vessel name Sundsvalla, hailing port East Lyme, MA, Snowgoose catamaran designed by the Prout brothers, LOA 34' x Beam 15' 8" x Draft 3' x 5.5 Tons - Drogue: 9-ft. diameter BUORD on 350' x 3/4" nylon three strand tether, with bridle arms of 45' each and 1/2" galvanized swivel - Deployed in a gale about 60 miles west of Cape Finisterre, Spain, with winds of 40-45 knots and seas of 20-25 ft. - Vessel's stern yawed up to 90° off to each side - Drogue was eventually tumbled and rendered useless - Drift was about 30 nm during 18 hours of deployment.
Sundsvalla crossed the Atlantic in August 1987. On her way down the Iberian Peninsula she ran into a northeasterly gale about sixty miles west of Cape Finisterre. She used the same parachute drogue used by Echo in the previous file (D/C-2). The behavior of Echo was satisfactory. The behavior of Sundsvalla was anything but satisfactory. She would not lie to the relatively large drogue by herself. She had to be steered manually down the steep wave faces. And she kept doing the same thing that Galliard did in file D/T-2, i.e., surge forward and then snap back on the elastic rode. Later on, when the line had temporarily gone slack, a breaking wave threw the drogue and tangled it around itself.
What was the big difference between Echo and Sundsvalla? Sundsvalla has her mast stepped aft (most Prouts catamarans do). Any sailboat with her mast stepped aft will behave relatively well when using a sea anchor off the bow, but relatively poorly when using a drogue off the stern. The opposite is also true, of course: any sailboat with her mast stepped well forward - cat-rigged - will behave relatively poorly when using a sea anchor off the bow and relatively well when using a drogue off the stern. Transcript:
On passage from the south coast of England to Bayona, Spain. Encountered "dry" gale from the northeast. Sailed in rising wind/seas all day under staysail alone. Near dusk, wind rose to Force 9 and occasional seas began to break. Took down all sail and deployed BUORD off stern. No problem with deployment, but vessel would not lie to the parachute by itself - it had to be steered. Line would go slack periodically. Could not keep bows pointed downwind all the time. Finally, a breaking wave caught the drogue and tangled it around itself. We left it deployed, but effectively lay a-hull all night and into the next day. Took several breaking waves over the boat - not recommended! Recovered BUORD after gale subsided and continued to Bayena.
PROBLEM: The Prout Snowgoose 34 catamaran has the mast stepped way aft. I believe that this is what caused our problem. The center of effort of the boat's aerodynamic drag was so far aft that it would yaw from side to side. This allowed the tether to go slack and ultimately tangle.
SOLUTION? The next time on a vessel of this type, I would use a storm jib hanked onto the forestay and sheeted athwartships. I believe that this would keep the bows pointed downwind by moving the center of effort forward. This would allow the helm to be untended and the tether to remain taut. Although I haven't tried it, a large para-anchor deployed from the bow should work very well because the aft mast position would increase yaw stability. [Note that a large diameter para-anchor did work well off the bow of the Prout Snowgoose, Rhayader, in File S/C-3.]