FD Main changes ?

[Marc NED 32]

Below an article found on sailinganarchy. (http://www.sailinganarchy.com/index_page1.php)

What do you guys think about the idea of increasing the main sail area ?

Marc
Ned 32


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.



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 3x1.2 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 ()

02/26/10

[Jonathan Clapp]

A full batten flat top, like the A-cats have now? hmm....

[sparky]

Hi everybody,I think that the next step possible, without distorting the boat, is the switch to mylar sails.
I have made a genoa in mylar and the performances are increased.
Actually we have mast,boom,centreboard,rudder, carbon-made, everything very expensive,but the sails are still in dacron with the excuse that they are too expensive.
A good dacron it's not more expensive than a good mylar,with a good performance boost as well as having better and more technologic appearance, everything at an equal cost or even less than the dacron.
I think that the dimension of the actual sailplan is right.An increase of the sailplan would make the FD very difficult to sail in extreme weather conditions, or in less extreme conditions (over 18 knots)for light crews.
5o5ers have mylar sails and alu mast,but they are thinking to the switch at carbon mast.
We want to get us through once again by cousins of the 5o5?

I think that the time to change is arrived.

[Neil Pye]

I'm totally unconvinced that any extra area in the mainsail would be beneficial or desirable. If the extra area is not needed upwind, surely all it would do would be to increase drag and therefore slow the boat down? Off the wind it might have a tiny effect on performance in marginal planing conditions. Lets face facts though, nobody rejects the FD because it's too slow!

As for the Mylar debate, I'm not a sailmaker so I may be completely wrong, but I see two major issues with mylar sails:

1. Unless we go to pretty exotic materials, are they not heavier and less adjustable than Dacron?

2. I'm not convinced the life of a laminate genoa would be as long as that of our current Dacron. Think about the battering the genoa gets through tacks and gybes, and the extra stresses of rolling all that area.

I don't have any fundamental objection to film sails, but we'd have to be sure it's right for the class. If we're only changing for the look of the things, why bother?

[Toby]

I am completely unconvinced by the idea of 'laminate' headsails... A vast majority of this early topic is based on the 5o5's. They have tried laminate cloth for headsails and they simply do not last. I conceed there is a possible speed advantage but this is very short lived and the sail soon goe's 'off' due to wear and tear caused by tacking and flogging. I cannot see how an FD genoa would last better than these... A number of other classes have also tried this route and come to the same conclusion. All are now using laminate mains and Dacron headsails.

Mainsail shape on the otherhand is an interesting point...

There are a large number of mathematical models that show the increased efficiency and power of quare top sails over 'pin head'. But rather than try and go into details , I would simply point out that virtually without exception any boat that wants to go very fast has 'fat head or 'square top' mainsails, from Moths and windsurfers through International 14's, 49ers and 18' skiff right the way up to Volvo 70's and G-class Tri's. I think the current trend says it all on it's own... however if anyone is really interested I might be able to persuade someone to do some comparative figures for the current main and a new big main and get the results for all to see.

Toby

[Marc NED 32]

Would something like this work ?

NZL FD.jpg (36.72 KiB) Viewed 728 times

[sparky]

I'm totally unconvinced that any extra area in the mainsail would be beneficial or desirable. If the extra area is not needed upwind, surely all it would do would be to increase drag and therefore slow the boat down? Off the wind it might have a tiny effect on performance in marginal planing conditions. Lets face facts though, nobody rejects the FD because it's too slow!

As for the Mylar debate, I'm not a sailmaker so I may be completely wrong, but I see two major issues with mylar sails:

1. Unless we go to pretty exotic materials, are they not heavier and less adjustable than Dacron?

2. I'm not convinced the life of a laminate genoa would be as long as that of our current Dacron. Think about the battering the genoa gets through tacks and gybes, and the extra stresses of rolling all that area.

I don't have any fundamental objection to film sails, but we'd have to be sure it's right for the class. If we're only changing for the look of the things, why bother?

Hi,currently the new laminate is not heavier than the dacron one,at equal weight laminate mylar is stabler than dacron,and It's no longer as stiff as it once was.A good dacron (Contender 4.46 oz)is more stiffer than mylar and this causes breakage of the tissue, especially when you roll it (for example when you disroll the genoa and the spi sheets are in the middle).
A question: who use one genoa more than one season? If you use a medium dacron genoa (4.46 oz) for 6-10 races in medium conditions (12-18 knots),at the end of 10th race you will have the clew destroyed,as with a mylar genoa,but with a mylar genoa you would have had better performances.

[Jonathan Clapp]

Would something like this work ?

NZL FD.jpg

When Hideo did this experiment, I recall reading his notes. Marc, Do you know where that text is, of his findings? I cant find it.



I have one rather obvious question, how does the larger main affect righting moment?

[Toby]

Hi,currently the new laminate is not heavier than the dacron one,at equal weight laminate mylar is stabler than dacron,and It's no longer as stiff as it once was.A good dacron (Contender 4.46 oz)is more stiffer than mylar and this causes breakage of the tissue, especially when you roll it (for example when you disroll the genoa and the spi sheets are in the middle).
A question: who use one genoa more than one season? If you use a medium dacron genoa (4.46 oz) for 6-10 races in medium conditions (12-18 knots),at the end of 10th race you will have the clew destroyed,as with a mylar genoa,but with a mylar genoa you would have had better performances.

Agreed at the front end of the fleet the competitive life of a headsail is no more than a season, but I would argue that for the majority of the fleet this is not true and that they keep sails for use for 2 or 3 years. In addition no cloth is going to stand up to the abuse of unfurling or furling through the spinnaker sheets or the spinnaker halyard. The only way to avoid this is massively over engineer a sail making it very heavy!

What cloth are you proposing to use for a 'mylar' headsail?

There appear to be some big holes in your arguement... firstly, the wind window you mention is quite small and whilst most of us would love to be able to sail in 12-18 knots every time we launch this is far from the case in reality. What would you use for a light airs sail? Still Dacron? If so why have a laminate medium/heavy sail? I'd not want to use any cloth in the region of 4.5oz in less than 10 knots.

Also, the stability of the Dacron compared to the 'Mylar' is very much dependent on the cloth used. There are a wide variety of yarn layouts and film thicknesses that have wide range of applications and performance for a very similar appearance. Do you actually use a sail with Mylar yarn or is the sail a laminate with different fibres in which many people still refer to as 'Mylar'. From personal experience Laminates do not generally like being furled unless they are quite heavy wait.

If you can let me know the cloth being used I will be able to get the performance test data for the cloth and compare it to the Contender 4.46 Polykote you mention.

The other big factor has to be cost. Quite simpy any decent laminate sail will cost more than the equivalent Dacron sail quite simply because the cloth costs more. Is this an additional cost that the fleet want to bring in? The class is not cheap now!

Just for the record some cloth manufacturers are now starting to produce Dacrons with a softer finish that maintain the perfomance of the current range of 'hard finished' Dacrons. I am currently testing one on my boat and I have been delighted with the results to date. Please contact me directly for more information.

[sparky]

Hi Toby,i propose this range like a medium range,you taught me that the sails made in laminated fabric use range much greater than those made in Dacron.The laminate that i have used for trial have very good performances also in light wind and it's no heavier than a Contender 3.8 oz.
My sailmaker, Be1 sails,can offer the same price for laminate sails than a dacron sails,with the experience derived from America's cup in San Diego with North Sails and more more sails maked for IRC and ORC,and told me that a good dacron costs more than a good laminate.
If you're a racer, now this is happening in Italy, at least every 2 seasons the sails are changed by almost all the crews, and the best crews change them every season,and I think that the same happens in Germany or in Nederland.
Next week we will made a complete set of laminate sails at same price than dacron for trials.