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Re: why boats point well
I'll give this a shot, but there are a lot of different ways to look at this.
At the most basic level, a boat points well when its sails and keel have a high lift to drag ratio, and the hull, deck, rigging, and everything else on the boat produces as little drag as possible. But, I suspect you are interested in a more detailed answer.
So here is a bit more detail. But remember, everything below are generalizations. I'm sure that in practice boats can be found that point well even if they don't have all of these characteristics.
First, sails, keels, and airplane wings for that mater, get more efficient as they get longer and skinner. Take a look at the wings on a sport glider aircraft. They are very long for a reason.
This means that sailboats with taller masts and deeper fin keels will tend to point better. But in addition to the length, the shape of the sails and keel are important as well. Most deep fin keels will have a decent shape, but some will still be better than others. The shape of sails on the other hand can vary a lot. If the best pointing boat has old stretched sails, it probably won't point as well as an average boat with a good set of racing sails. This is sort of a mid-level of detail answer.
An example of a even higher level of detail would be the chainplate/shroud position. Chainplates all the way out at the edge of the hull usually put the shrouds out far enough to keep the jib from being sheeted in as far as you would like for the best pointing angle. That is, effectively the wide shrouds block you from from getting the shape you want from your sails. There are way more details like this, most of which I don't even know, the will effect pointing ability.
But back to some more of what I am referring to as mid-level of detail answers.
Lower cabin trunks and lower sides to the hull will reduce wind drag and thus improve pointing. And things like dodgers or dinghies out in the wind will increase drag and hurt pointing.
The shape of the hull will also make a difference in drag from moving through the water, but I'm not qualified to say much on this except that the best hull design will be different under different conditions. Moving easily through flat water is quite different than fighting against large waves.
I'll just add one more thing about sail shape. If you have a wing sail that can maintain it's shape regardless of wind angle, like the main sails used on the last America's Cup boats, the boat may be able to sail very close to the wind. Angles of under 10 deg. to the wind are possible, BUT (and this is a big but), it will not likely be the fastest way to go to windward. Falling off and gaining speed will get you there faster.