Accordingly, one of the hot topics of discussion at the regatta was the use of class-legal asymmetrical spinnakers. The Mumm 30s are relatively unique among the offshore one-design classes in allowing both symmetrical and asymmetrical spinnakers in either masthead or non-masthead configuration. Class rules specify the dimensional limits of these sails, both in the length of the luff, leech, and girth, and in total sail area. This gives sail designers parameters within which to find a solution for the critical trade-off between a sail's size and speedlarge sails generally prove faster, except when the air gets very light and then smaller sails are usually better.
Asymmetrical spinnakerscommonly referred to as A-sailshave received tremendous attention over the last few years as wind-tunnel tests and events like the Whitbread and America's Cup have proven their use to be faster than conventional symmetrical spinnakers in many conditions. In fact, most easily-driven offshore yachts, such as Volvo 60s and turbo-sleds, only have A-sail spinnakers in their off-the-wind inventories. Because theyre also fast, easily-driven boats off the wind, Mumm 30s would also seem ripe for A-sail use.
Class rules for the Mumm 30, however, also specify that each competitor must declare before the regatta which sails he or she will use, forcing those with A-sails to effectively put their money where their mouth is by leaving their masthead symmetrical kites at the dock. (While class rules allow fractional spinnakers, it's acknowledged that the breeze must be really howling25 knots or morefor their use to be competitive on windward-leeward courses.)
|"If A-sails are so fast, why don't more sailors use them?"|
According to Jodi Davis, the bow person aboard Phil Garland and Rich Shulman's Mumm 30 Trouble, the North American Champion: "We also get someone to run aft with the clew of the sail on the new side, bringing as far back as the shrouds so that the sail snaps through the rotation. This allows the sail to fill on the new jibe faster." During this stage, Jodi releases the inboard end of the pole from the mast, and then outboard end from the old afterguy, and rotates the pole end-for-end, attaches the new afterguy, and pushes the pole forward before re-attaching the inboard end to the mast. All that time, the A-sail luff load is supported by the tack line, which is never looser than a foot or so off the bow. The tighter the tack line, the easier it is for the sail to rotate and avoid twisting into an hourglass.
Once on the new jibe, the tack line is eased as the afterguy is brought back to take the sail and pole to the new position. The topping lift and foreguy are never moved (except when needed to move the afterguy), and the pole remains about half as high off the deck as it would if it were supporting a symmetrical spinnaker. A variation on the end-for-end pole rotation is that used on larger boats where the pole is detached from the mast, shoved aft, the afterguys are switched, and then the pole is shoved forward and re-attached to the mast. This is particularly important when the pole length is long relative to the foredeck, as it is aboard most turbo-sleds, Volvo 60s, and Americas Cup boats.
So, while there are many considerations involved in evaluating the efficiency of using A-sails, "it comes down to mechanics and possible tactical considerations in a large one-design fleet," says Flynn. He also points out that there can be other negative factors, such as "intangibles like the crew's psychology which might be overcome with better jibing and takedown techniques."
As it turned out, in Miami Beach Vincenzo Onorato's winning team aboard Mascalzone Latino never used an A-sail at the Worlds, and only two of the top-10 finishers Trouble in seventh and Steadfast in eighthused A-sails at all. Nonetheless, with the promise of better speed as an incentive, look for further developments to come with these sailsin the Mumm 30 Class and wherever else their use is allowed.
Suggested Reading List
- Using the Asymmetrical Spinnaker by Brian Hancock
- Spinnaker Fundamentals by Steve Colgate
- Spinnaker Trim for Performance by Rich Bowen
- SailNet Buying Guide - Spinnaker Poles
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