Re: Modern design + full keel?
I got interrupted by having to go work. LOL> What I am saying is, a long keel is not the only type of full keel. It's one design. And, really, the long keel on a modern cruising sailboat is a lot different than the long keel on the Swallow, from that book about swallows and amazons.
The cruising sailboat usually will have a displacement hull with a good bit of non-keel hull below the water line. It's keel will be deeper and fuller than on the 1800's style sailing dinghy. The keel will also tend to be a triangular affair, wider at the hull than the bottom of the keel. The dinghy, by contrast, will tend to be beamy with a full entry and a moderate amount of draft. It's keel will be shallower and not have much taper in cross section; having nearly vertical sides. The keel will tend to get wider towards the stern. The rudder attached to the keel.
Go back in time further, to the Germannic boats of the Viking age. There, you have a hull which is close a modern racing hull. It has a narrow entry ( and stern, as well ) and a fuller mid section.
It carries very little draft. The keel, shallow like the Swallow, will be deeper in the middle of the boat, than at the ends. The rudder is a steering oar, off on the starboard side, which is how starboard got it's name.
This full keel looks nothing like the cruising sailboat and the hull is very different than either of the afore mentioned vessels. The Viking ship is a great example of exactly what I am getting at, in my previous post.
While we have hulls left, in various conditions, no Viking sails have been found. In the late 1800's, in Scandinavia ( Denmark, I believe )i a replica of a longship was built to sail to America as a poke in the eye to Columbus, on Columbus day. Time was getting short and the builder/captain cut corners by taking the tall, square sail, off of a tall ship he owned, and fitting it to the longship. He sailed it to America. Now, since then, all ( but one ) longship replicas have used a tall, square sail, even though there is no evidence for this.
Even with such an inefficient sail ( although the beitass used by the Vikings really helps out a square sail, when sailing to weather ), these replicas have such an efficient hull design that they can sail upwind. I believe it's something like 50 to 55 degrees from the wind, which is better than the tall ship the original sail came from.
However, Viking age artwork shows a different type of sail. It shows a low, rectangular sail, wider than it is high ( a 3 to 1 ratio ). One replica, the Sigrid Storrada, was built to this spec. Interestingly, that sail answered a few questions about the Gokstad ship, which had gone unanswered with the allk, square sails. Despite being supported by the Viking's own art and despite the lack of evidence supporting the tall, square type of sail, this sail choice is still very controversial. Go figure.
Anyhow, the same hull, built like the Gokstad ship, with this "new" sail, is reported to sail 45 degrees to weather at around 5 knots, in 'average' winds. Quite acceptable, even by modern standards.
The only difference? The better sail. The "new" sail, when tacking, dips it's yard, like a balanced lug. It's a far better sail, on the wind, than the tall, square sails.
So, what I am getting at is that people judge the individual elements, of a certain design, by the qualities of the design it is used on. That's not really fair. All of the elements of a design work together, in concert, each to give the whole a certain quality of performance. A great hull, hampered by a poor sail, will not perform as well as it should. A great sail, like a sprit sail, hampered by a poor hull, will not perform well.
For instance, sprit sails were popular during the golden age of sail. They were a working sail on working boats. Working boat hulls are designed to carry big loads or to dredge for oysters or to fish from. They aren't necessarily designed for top performance. On the other hand, great racing boats aren't good for much else. I think the story of the Bluenose and how she came into being illustrates this well.
Life is full of compromises. You can have a racecar. You can have a luxury car. You can have a truck. You can have a fuel efficient economy car. But you can't have a vehicle that is all of the above. You have to decide what your purpose is and design for that.
People tend to always put Bermuda sails on performance hulls and sprit sails on 'traditional' hulls. Then they want to say that the sprit sail is not as able as the Bermuda sail, to wind. But that's comparing apples to arranges.
Everyone says that the same boat, with a full keel, will not perform as well as it did with a skinny fin. But where is the evidence? Where is the modern racing hull with a full keel? In order to prove something, scientifically, you need controls to rule out other possibilities.
Plus, there are so many different full keel designs. Which one is most efficient in which kind of application? To get a real answer, you'd have to take a number of boats, with that modern racing hull, and try different keel designs and then compare the results.
Of course, you also have to consider rudder design.
You have a rudder hung from the end of the keel, at the very stern, on a long keel, in a modern cruiser. You have the starboard mounted rudder on a longship. You have the keel mounted rudder, mounted deep under the boat, on one of those 1920's racing boats. You have the type of keel rudder combination that has the bite out of it, to reduce wetter surface, in front of the rudder. And, you have a transom hung rudder, like my boat is now, that is a foot from the keel of the boat, because the keel ends at the waterline and the stern is an inch out of the water, when the boat sits balanced.
The rudder has a big effect on how the underwater 'foil' performs.
So many possible combinations of elements, yet so few have been tried. You really judge any one design element until you have seen it perform with, at least, the majority of possible combinations...or at the very least, you can't compare the abilities of a full keel, on a 'traditional' hull to the abilities of a skinny fin on a performance hull. It would be like putting an airboat and a cigar boat on the water, in a swamp, and using that to judge which is the better boat.
Myself, I was willing to experiment...and I have been rewarded for it.