And at last, the wind blew. Although it was 33 degrees C today, I rigged this improvized sailboat for the first time after recent upgrades, and from the very start, tried to sail upwind through the narrow sleeve of the lake towards the place where it broadens. Since in that sleeve there is only 200-300m from one shore to another, and narrowing as I went, winds are weak, gusty, and unpredictable - more vortexes from trees and hills than steady wind. It was very difficult to keep steady pace, but I learned as I went, made adjustments to sail shape (with recent additions, I now have traveler, cunningham, outhaul and boom vang, which make wonders of the sail shape), made center of mass adjustments to lift the stern as rwatson suggested, and eventually, I understood what drives this boat forward. One thing I really learned - keep the speed up no matter what. With speed, I couldn't see any drift at all (these high aspect ratio leeboards work like a miracle once speed is gained) - but if I let boat stop, it goes sideways in seconds. It was quite hard to accelerate and cover enough upwind distance before I had to tack again, since it was a 50 meters bottleneck between shores where the sleeve ended (just before exiting it) and unpredictable gusts didn't help either.
But when I finally left the sleeve, entered broad waters... And felt like the king of the seas (sorry, lakes). With no nearby shores anymore, there was steady force 1 or 2 wind, and sailing upwind became so easy, that I almost cried of joy. Such freedom, such a wonder... After a while, wind went below 2m/s with rare gusts, but with steady direction, I was still able to make it upwind, just a bit slowly. Even when there was so little wind that I couldn't feel it on my face anymore, boat still made upwind distance. So I went hunting for ripples on the water, sometimes no more than 10-20m wide "corridors", and sailed in them from place to place.
Later, when hands got tired of holding the tiller and the mainsheet, I rigged an "autopilot" - just lashed the tiller and clamped the mainsheet. And because boat was so balanced and stable on the reach, it went for about 10 minutes in steady speed and direction without ANY intervention - I might as well jumped out, it would probably sail by itself (unless changed weight would change directional balance)! In the meantime, I re-tensioned stays, made a boom vang, answered the call of nature, and, standing on the bow deck, waved to some beautiful girls on shore who looked with awe, as they probably saw a sailboat for the first time in this lake (I think no one wants to fight gusts and vortexes in these narrow sleeves).
And then, when I felt that wind is about to die, I sailed back downwind towards our berth. Strange, though, that sailing downwind, boat balance changed - it wanted to turn upwind, even though mainsheet was almost all the way out, so, CoE went forward. I expected it to act vice versa. As I approached the berth, I rigged autopilot again to have free hands so I could raise the leeboards (they run more than 1 meter below waterline, and could break if boat went grounded), and then, even with heavy drift, manuevered into the narrow berth under sail.
I don't know if there is any other feeling in this world that could compare. Sense of achievement, of freedom, of something else that I can't put to words. At last this sailboat is good enough and I control it well enough (although I'll strive to do better) to sail anywhere with almost any wind. As sharpii2 said, it certainly has this "small groove" conditions in which everything works, so it is very difficult to sail (to keep speed up) for a novice like me, but on the other hand, maybe these are the best conditions to learn.
I can't tell how happy and proud I am now. Thank you. Thank you all who helped, inspired and supported me. I couldn't have done this without you. At last, all the hard work paid up.
Two days from now, and experienced sailor will come here, and will evaluate my sailboat and sailing first-hand. It will also be the "official" launch, a shakedown run, with spectators, photoshoots, and so on (I just pray there would be any wind that day). After that, I will upload these photos for you to see.
Thank you again. Due to your support, I finally saw my dream come true.