o’ duchtman

o’ duchtman

SA’er ‘Longshot’ with an excellent op-ed piece on how to improve the speed of the classic Flying Dutchman.  Worth reading, and be sure to browse much more from Doug at the California Flying Dutchman site.  

The objective of this page is to explore avenues for improving FD performance relative to the 5o5. There are generally three avenues to increase a boats performance: #1:increase horsepower (sail area); or #2:reduce weight; or option #3:change the hull shape. For my purposes, redesigning the hull, blades, or other details is expensive and pointless. While redesigning, why not add racks? Therefore, only option 1 and 2 are being considered. This author believes increasing mainsail area is the obvious solution, as reducing weight may not be possible for many boats.

Increasing spinnaker area
The Flying Dutchman is already well up the performance scale, but there is still room for improvement. Using the tried and true Horsepower to Weight ratio (Sail Area/Weight), this leads us to two obvious ways to improve performance: increase sail area, or reduce weight. Focusing first on sail area, upsizing the spinnaker is pointless – it is already at the symmetrical spinnaker upper limit. One could argue for an asymmetrical, however the obvious answer is go get a skiff that already has one. Increasing spinnaker size reduces enjoyment, while increasing the risk of capsize and breakage, and probably would not increase overall speed much. Indeed, a larger spinnaker might cause crews to sail deeper courses, thus counter-affecting any speed benefits from the larger spinnaker. There are also legitimate concerns about the affect on the new carbon masts, and whether they would need to be modified. I suggest leaving the spinnaker alone.

Increasing genoa sail area
Likewise, the genoa is already at its upper limit. The jib halyard sheave could be moved up the mast, but to what purpose? Sail area near the top of the jib adjacent to the mast is inefficient, probably useless. In fact, the top of the current jib could probably be whittled back, improving airflow at the top of the jib, without any loss, and possibly some gain. The foot could be lengthened, but why? It is already huge, and making it larger would not amount to an improvement, indeed my crew already complains about how much sail he has to haul around. No one is interested in a larger genoa, so, moving on…

Increasing mainsail area
The mainsail could be made larger, without sacrificing manageability.

Add roach to the top of the mainsail and down the leech. On a 20 foot leech that amounts to 6 inches of extra cloth along the leech. This is an oversimplification, but essentially how it would be done. In light to moderate conditions, this would be a hands down improvement. But if designed properly, the extra roach could bleed itself, as the FD top sail area is already designed to do. Were this done, and one sailed in strong winds, the sail area at the top ‘goes away’ while sailing upwind, but comes back when sailing off the wind. My suggestion is to increase the mainsail area by 15 square feet, by adding roach at the top, and modifying the class rules regarding battens. This would be a small change in sail design, but a huge improvement in performance. Please read my comments on owning a Thistle, where the roach was increased in the fashion I am recommending.

Thistles have gone to a larger mainsail. Their luff and foot are the same, but they have more roach near the top. The difference is dramatic, and quite manageable. This is the path I am suggesting – not a huge increase in sail area, just a little, like the Thistle.

Reducing weight
The other option is to lighten the boat. This can be accomplished by adopting a new weigh-in strategy: simply weigh the entire boat, ready to go sailing – it should weigh 335 pounds. They could remove the weight from wherever they choose. In fact, this weigh-in strategy is worth doing regardless. Currently at 350 pounds, the FD is comparatively Much heavier than the 5o5 or 49er. Yes, both are shorter, but that alone does not account for their lighter weight.

The 49er is 16.1 feet long, and 210 pounds. That’s 13 pounds per foot. The 5o5 is 16.5 feet long, and 280 pounds all up, therefore 16.96 pounds per foot. The FD is 19.8 feet long, and 350 pounds all up (See Weight Underway at left), therefore 17.67 pounds per foot. If the FD used the same weight ratio as the 5o5, it would weigh 335 pounds – i.e. 15 pounds less than it does. And the 5o5 is not an especially light boat.

	Weight		Sail Area			Upwind		Downwind		Average		DPN
	Crew	Boat	Main	Jib	Spinnaker	SA/D	BN	SA/D	BN	SA/D	BN
49er	360	291	161	65	420	0.35	1.73	.89	2.78	.62	2.26	68.2
5o5	360	295	132	53	220	0.28	1.57	0.54	2.16	0.41	1.86	79.8
Both ideas FD	360	335	125	90	220	0.31	1.66	0.50	2.10	0.40	1.88	{79.7}
Big Roach FD	360	350	125	90	220	0.30	1.64	0.49	2.08	0.39	1.86	{79.8}
Lightweight FD	360	335	110	90	220	0.29	1.60	0.47	2.05	0.38	1.82	{80.0}
Standard FD	360	350	110	90	220	0.28	1.59	0.46	2.04	0.37	1.81	80.1

Notes:
BN=Bruce Number= square root of Sail Area divided by the cube root of displacement (Weight).
Boat Weight is the fully rigged weight of the boat, as if it were sailing, not including crew.
Crew Weight is the weight of both crew, assuming 180 pounds each.
Upwind S/A is upwind sail area, the area of the mainsail and jib combined.
Downwind S/A is Downwind sail area, the area of the mainsail and spinnaker combined.
SA/D is the Sail Area divided by displacement (Weight).
Big Roach FD assumes a 15 square foot increase in mainsail area.
Lightweight FD assumes 15 pounds are taken out of the boat.
Both Ideas FD assumes 15 pounds are removed from the boat, and 15 square feet are added to the mainsail.
DPN is Dixieland Portsmouth Number handicap, a US Sailing handicap system.
Numbers in braces are estimated DPN, predicated on the Average Bruce Number (Average BN).

This table shows several points:
The 5o5 main has more roach than the FD main, with the same luff and foot length. In fact, the 5o5 main fits right on the FD spars, adding about 23 square feet of sail area as roach. The larger roach is what I am after.

Both 49er and 5o5 are at least 70 pounds lighter than the FD, showing that the FD is overweight.  Obviously the 5o5 handles the larger mainsail just fine, likewise with the 49er with a Much larger mainsail, suggesting the FD would handle a larger mainsail just fine.  Finally, removing 15 pounds and adding 15 square feet is well within reason, and will keep the FD performance at the top of the dinghy fleet.

Therefore, my suggestion is to remove 15 pounds from the boat, by modifying the rules to stop weighing individual items like the mast, rudder and centerboard, and instead weigh the entire boat. It would have to weigh 335 pounds fully rigged, ready to go sailing. The boat could be weighed at the hoist, as it was launched. This would have an additional benefit: If a boat had an overweight mast (an aluminum mast), it could remain competitive with a carbon sparred boat by removing the extra weight from somewhere else in the boat. This simplifies the measurer’s job, and makes spot checks of a boats weight much easier.

So how would I remove 15 pounds from my boat? Replace the wood deck with a foam cored deck. That’s more than 15 pounds, but even if it weren’t: reduce hardware, reduce line size, get rid of superfluous double sided systems, build a new cored rudder that isn’t so heavy – plenty of options exist. And finally, for older wooden decked boats, how about modifying the deck rules, to allow less deck? The foredeck could be kept as is, but allow removal of deck aft of the mast. There is plenty of opportunity in this one item to remove 15 pounds from the boat.

I also suggest increasing the mainsail area. This can be accomplished by changing the rules regarding the length of the top batten and where it is placed, and increasing the leech length. Increasing the mainsail area makes much more sense than opting for a MUCH more expensive Mylar mainsail, with significant cost increase and marginal performance gains. Currently, the 5o5 class offers both Dacron and Kevlar mainsails. The North Sails Dacron model costs $925 (same price as the smaller FD mainsail), the Kevlar model costs $1426. A $500 cost increase, without any increase in sail area — $500 to remove 1 pound aloft, or $500 a pound! That’s a pointless arms race most in the fleet can not afford, it is also a deterrent to growth. The table shows that increasing the mainsail area by 15 feet boosts FD performance equal to the 5o5, a very cost effective approach to performance improvement.

Currently the 5o5 is out performing the FD in the lower wind ranges. Their handicap is changing in real time: the 5o5 handicap has dropped in each of the last several editions of the US Sailing handicap tables (from 80.2 in 1998 to 79.8 in 2008). During this same period, the FD handicap started at 80.2 in 1998, and dropped to 80.1, stagnating where it is today. This fleet should be concerned about letting the 5o5 become the faster boat, thus drawing people away from the FD and jeopardizing the future of the class. The proposals on this page would make the FD plane sooner, and get the crew on the trapeze sooner, while keeping the boat manageable in the upper ranges of wind speed. Most importantly, these are not expensive proposals. A larger mainsail would have a relatively small marginal cost – perhaps 10% more expensive – an extra $100. We’ve already super sized the spinnaker, why not the mainsail?

Racing 5o5’s
Another thought on improving performance: why not race against the 5o5’s straight up – with no handicaps?

When racing in open divisions against a variety of boats, competitors are scored using a handicap system. When racing dinghies, that system is the Portsmouth Handicap system, and usually the race committee chooses to use the DPN handicap (Dixieland Handicap Number) – a generic handicap roughly corresponding to 12 mph wind. Using this system, one can calculate – ahead of time – how much time one has to ‘give’ other boats. In other words, the number of seconds ahead of the other boat you need to be, in order to win.

So, for example, the 5o5 has to ‘give’ the Flying Dutchman 1.2 seconds every ten minutes. That means that if the race is 30 minutes long, the 5o5 must finish 3×1.2 seconds or 3.6 seconds ahead of the FD in order to win. If the 5o5 only crosses the finish line 2 seconds ahead of the FD then the FD won that race.

Not all boats perform the same, however. In this example, if the two boats started together, the FD would likely beat the 5o5 to the weather mark, but then loose ground to the 5o5 off the wind. So the FD would be wise to bank away as much as possible on the weather leg, and cover the 5o5 off the wind, to prevent them from making good on their off-wind performance.

These handicaps are so alike that this author thinks the two classes should race — straight up — against each other. 3 seconds is not an unusual time between boats within the same fleet, and the two boats performances are complimentary. On the wind, the FD represents a good match boat to race against for the 5o5, and off the wind, the 5o5 represents a good match boat to improve FD performance against.

Conclusion:
Increasing mainsail area makes a lot of sense, and is much cheaper and more effective than switching to a Mylar mainsail, or increasing spinnaker size. Decreasing weight would be nice, but there are plenty of boats that probably can not reduce weight, and even if they could, this amounts to a significant change that most owners would balk at. The 5o5 mainsail is a near perfect fit for a trial sail, and testing along this front should begin. The author has recently acquired a 5o5 mainsail in nice condition for this purpose. (2/16/2010). Generally the author believes FD’s and 5o5’s should race against each other, straight up, since in most conditions the handicaps are nearly identical.

Doug McWilliams, Longshot ()