cornwallis said..
Anyone willing to explain the larger chord, thinner more refined foil section and extra camber on this foil? In terms of what each element is designed to achieve?
The main reason to go mid-aspect on a surf wing is to reduce the wing span which reduces the roll resistance. I believe a responsive roll rate is the main component that makes a foil feel carve-y.
If you reduce the span you will need to increase the chord to increase the surface area and hence the lifting surface of the wing. Larger chords have more surface drag per lift than higher aspect ratio wings which makes them less efficient but they do increase the pitch stability of a wing.
Camber improves the low end lift of a wing (like airplane flaps going down during landing and take off) at the detriment of drag which will reduce the top end speed. Lots of high camber sections can get quite draggy At high speed and can be hard to control the lift spikes with changes of angle of attack. What makes armstrong's camber unique is that it remains very controllable at high speed.
A refined foil section, or thinner foil section reduce the frontal area and overall drag of wing which makes it faster usually you lose some low end with a thinner foil and your useable angle of attack range reduces as you can stall at lower angles of attack. This MA is thin overall but also has a particularly thin leading edge which helps shed bubbles quickly and re-attach water flow to the foil greatly increasing your chance of recovering from a breach. A thin leading edge is also more prone to stalling at lower angles of attack.
As you can see all these design changes are there to balance out the shortcomings of each other but also makes you realize how difficult it must be to find the right balance to make everything work in harmony.