Lately I read people saying minimal distance between the mast and the deck is important for a more responsive board.
But I'm wondering if maybe they are confusing the better performance of the thinner board, could be more due to it's improved aero dynamic shape, moving through the air? Or could it be that it being just because effectively acting like a shorter mast ( less distance between the foil and the deck.) Or maybe a little of both and nothing to do with the distance of the mast to the deck.
Anybody have any thoughts on this?
If everything else is equal, then a thinner board means a shorter lever from your feet to the foil (as you say, like a shorter mast). But that doesn't necessarily mean better performance because everything else isn't equal - it depends on the rest of the board. My Axis Tray is 20mm thickness, but it is not going to be a viable option for most runs with zero buoyancy.
At the moment I'm riding the Amos Sultan, its very thick (6 1/8"), but it is 18" wide, and the performance is leagues above my thinner, wider board as I'm able to cant the board around its longitudinal axis with my feet very easily.
Personally i don't think thickness is a factor for choosing a board - that is what you're left with after you complete the rest of the square. Length, width and volume will drive how you get up on the foil - choose those and the thickness is what it is. The benefit of foiling is that you don't have to weigh off responsiveness of the board in the design, you just make it as stiff as you can with weight and material limitations - unlike a surfboard where you have to make a few more hard decisions.
With the thinner boards you get 2 things , firstly like you said better connection to the foil and secondly it lets the shaper give you a better rail more pulled over rail profile . This plays a big part in touch downs and bouncing off foam balls. The chunkier fat rails tend to stick at certain angles. I'm talking prone boards.
I definitely feel that thinner is better but it's all a matter of finding the right balance for what you want to achieve.
I've often heard people say a thicker board is the same as a longer mast but I totally disagree. Firstly the thicker board puts you further away from the foil but doesn't give you the clearance of a longer mast. Secondly I think it changes your point of leverage a bit, thicker flat decks can have a rolly disconnected feel.
Of course if you want to go narrower you'll need to go thicker. Narrower boards are so much nicer, more responsive especially in the roll axis also faster and more efficient. I find the narrow boards really help hide the thickness. Of course most would love to be on narrow thin boards but then there wouldn't be enough volume to work for a lot of foiling genres.
I think the more offset your stance the better a thin board feels. But that's based on winging with quite a lot of offset.
I think there are so many factors it's hard to truely prove. You thin out the same shape board and the board becomes lighter reducing swing weight which impacts the ride. We have built boards that are the same shape but different weights and the lighter one always feels more responsive. Also how stiff the board is massively impacts the ride. there are just too many factors and in general a thinner board is going to be lighter.