I can only speak of scenario 1 based on personal experience. With a 900/1000 cm2 race foil, easily off the water with 7.7 freerace or 8.0 full race. In colder, denser winter air, I can probably do that with a 6.7. This assumes your pumping game is good, though.

That is pretty good work XavierFerrer - congrats. We have a very diverse range of sailors where I sail - I am interested in the limitations for the different weights and at what point a larger sail does not help. eg if a 100kg sailor was on the same gear with the same conditions would a 10-meter sail work or does diminishing returns kick in earlier?

I'm 100kg on a 91cm, 163 liter board, intermediate foiler. I can't yet foil up in 8 no matter what but can stay on foil easily in an 8kt lull. I can pump up in 9 with an 8.5 (pictured in my avatar). The 8.5 is a very light Foiling-specific sail. I don't get up on foil any earlier on a very light 10.0 HSM although it will plane earlier on a fin than my 8.6.

Am 68kg and 1m86 tall
Future fly 145 foilboard + starboard carbon race foil.
1000 / 115 black fuselage /255

7,7 Ga sails cosmic 2cam freerace

Pump up in 7kn/8kn no problem at all and keep flying in less.

Good question. We all talk about wind speed. Anemometers at anywhere from 1 meter to 20 meters high, located everywhere. In the middle of a body of water, edges, even behind buildings or trees in some cases. For that matter, how many anemometers are even calibrated?

Windsurfers seem to have figured out, over years of history and discussion and debate, about how much wind translates to how much whitecapping, and about how much wind translates to how much pull on a given sail size and type and cut and draft.

See? It's all VERY simple, huh? Very empirical and very subjective. That's about as good as we can get it, I think.

I know what 15 mph wind looks like and feels like. There ya go. Scientific.

Yeah a lot of my knowledge about windspeed, short of an anemometer on the shore, is site and direction specific. One wind meter reads about 5kts above reality on the water, but the trend and direction is indicative. Also, some spots are so turbulent in some directions that you can't even stay planing long without a lot of effort. Foiling makes it easier but timing the pump for a good gust in confused swells makes it a challenge.

I've recently got new batteries for my anemometer and what I was thinking 10kts was lower than that. At least the water state usually tells me about what to expect, unless it gets to about 6.0 fin weather and below. Then I just rig and find out.

For me, i look at the water and if i can see enough wind to feather the surface slightly in the gusts, i can get flying on the 9m HGO with my IQ foil set up. That usually equates to between 6-8 knots on the anemometer readings at my local spot on seabreeze.

60kg when fat. In single digit winds I use my "large" sail. 5.5M but a huge wing. The SS HG84. 5kts requires a bit of effort (proper pumping)to get up foiling. ~7kts is realistically needed to get easily on the foil.