Foil acceleration through turning.
Something I've been noticing - acceleration boosts when carving, apparent even on tiny swells.
The foil speeds up when arcing into a turn.
Discussed by Erik Antonsen in his latest Progression Project podcast - his shows are awesome for those that like to geek out on foiling.
13 mins in - excerpt;
"the front and back wing in combination have a radius of turn through the water. Leveled out going straight the foil wants to lift, putting more weight forward increasing drag to flatten out where the foil actually wants to go, but when you allow that foil through a turn to express the arc that the two wings in combination want to follow, you're actually decreasing drag so you're more efficient through the water.
So that a front wing that's balanced for more lift is actually balanced for a tighter arc, the more you keep that turning you're more efficient, you're faster through the water so you're actually accelerating the whole time plus you're picking up the power of the wave by going back and forth across the face"...
..."the foil is more efficient as you're turning, so by continuously turning you're going faster through the water - and you're also able to go back and forth across the power of the wave so there's more speed there as well"
podcasts.apple.com/au/podcast/the-progression-project/id1206097336?i=1000483633491
Slowed up the GoPro video I posted a couple of days ago - I think I can see little speed boosts in the turns 
Interested in what others have experienced?
The good news in all of this is that you are doing a really great job of foiling nice deep S-turns.
My S-turns are still wimpy and shallow.
If you really want to see about speed, you have to somehow get GPS into your video in real time. Use a GPS-enabled camera or a watch and then synch the GPS to the video and show the speeds on the screen.
www.seabreeze.com.au/forums/Windsurfing/Review/GPS-Cameras-and-Overlay-Rendering-Software?page=1#10
Keep in mind that drag reduction, acceleration, and speed are related but not necessarily the same thing.
A turn at constant speed IS acceleration and requires either less drag or more power.
If this podcast is right (seems legit) then in a turn you can reduce drag, add in even a small wave and you are adding power.
I know personally that when I've lined up a gybe with a quick carve on a wave I've come out the other side with what feels like a lot more speed and almost zero power in the sail.
I use turns for both boosting speed, and for losing it, on Supercruiser- no idea how exactly - turns can act as a brake if I accelerate rapidly toward losing control eg. down a swell/wave or in big gusts 
Completely different on race foils - mostly manage speed by pointing higher or lower
Yesterday at my go to spot it's always a bit gusty and holey even with a 4.2. Normally when I see that a hole is coming up I would just bear off and glide through witch the 76 wing does quit well instead I tried carving kind of big S turns and it seemed as I was gaining a little speed. This was on an upwind tack, downwind it felt a little different.Every time I go out I see that their is still a lot to learn.
There's probably more of a contribution from swinging through a broad reach when you carve, and the sail being more powered up.
Is there the same boost as you are going through the middle of a gybe? I don't really feel it. But my gybes are fairly garbage at the moment.
Interesting, thanks for the replies 
I think I notice acceleration in the turns more on the Infinity 65 than the 76, so perhaps it's speed-related.
Guessing I'm doing about 20 knots in the turns on the 65, maybe a couple of knots less on the 76.
I'll check out Segler's suggestion to get GPS speeds on the screen - be kinda cool.
Plausible that an unrestrained Infinity 65 foil setup going fast would arc into a turn, so to keep it in a straight line we're applying drag?
Am wondering: Does the S-turn work like a pump of the foil?
Kind of like snow skiing, accelerating off the inside edges.
Select to expand quoteoscardog said..
Am wondering: Does the S-turn work like a pump of the foil?
Kind of like snow skiing, accelerating off the inside edges.
I think so.
During the S-turn there can be a slight pumping of the foil as you ride the swell and turn.
Adding to the inherent acceleration as the foil arcs into the turn (as discussed above).
There's a lot happening when the wind and swell is up and you're doing 20 knots through the turns, so it's hard to quantify.
That's why it's interesting to hear other's experiences
