Late to this thread, but it has the most careful set of V1 against V2 reports I've seen anywhere, so here is what they say when you put them through a model. Background: I've been building a free Onshape tool that designs hydrofoil wings and runs a performance sweep on them, and I modelled the Silk V2 range off AFS's published numbers and renders. AFS don't publish their sections, so those are guesses, and everything below is steady-state, flat water, wing and stab only. Treat it as arithmetic on your reports, not as a ride report.
How it was done, since "a model" can mean anything: the tool's performance maths (lifting line for wing and stab, trim about the balance point, section polars from XFoil) also exist as a Python twin that runs a flight solution in milliseconds, checked against the Onshape original to within 1 % on drag, glide and balance. For this post it compared 24 wing-and-rider combinations (the six V2 sizes and the two V1 sizes with published numbers, each at 85, 97 and 100 kg) and 11 stab and fuselage set-ups on the 1050, about 2,100 trimmed flight solutions in all, each size's minimum speed found by bisection. Behind that sits the tuning of the 1050 + U Surf 135 set itself: about a thousand sweeps the first time and 69,000 parameter sets in a rerun at the lower turbulence levels water has, which is where the "half its lift limit" usable-speed rule came from.
1. The 950 V2 against the 1050 V1 low end. Labskaus and Velocicraptor say the 950 V2 drops off earlier than the 1050 V1; Jeroensurf says the 1050 V2 is at least as good as the 1050 V1; PWDW says the 750 V2 has the 850 V1's low end. All three are the same statement: the low end goes with area, not with the version. Same area, same minimum speed, within what a different section could change. Each 100 cm² step is worth about half a knot. At 97 kg the model's minimum usable speeds (where the most loaded part of the wing is at about half its lift limit, which is where a previous rider's GPS put the point a tubercled Silk starts to sink) come out as 750: 12.1 kn, 850: 11.4, 950: 10.8, 1050: 10.2, 1150: 9.8. At 100 kg add 0.2. So if you want the V1 1050's low end in a V2, it's the 1050, and the 950 gives it away for glide. Jeroensurf's call to keep the cm² rather than the span is the right one for the low end.
2. The speed. Jeroensurf's 2 to 3 km/h higher average and top, sunsetsailboards' 1 to 2 kn over the V1 850: the plan form change on its own (AR 8 to 9 at the same area) does not give you that. In the model it is worth about 5 % of glide at 20 km/h and nothing at 30. So the top-end gain you are all feeling is coming from the section, the smaller tails you moved to, or the new fuselage geometry, and that is useful to know when choosing between the V1 fuselage and the Advanced.
3. Jeroensurf's tail comparison on the 1050 V2 is a nice test, because the three U stabs have almost the same area times arm, so a symmetric stab would trim the same in all three cases. What separates the U Carve is its section. An owner on another forum described it as flat on one side, which means it is cambered, and AFS's own page says the camber was tuned. A cambered tail mounted flat side down lifts, and a lifting tail does three things at once: moves the balance point back (your mast 1 to 2 cm forward), cuts the pitch stiffness (your "sensitive in pitch"), and adds glide (your "a bit more glide"). With a stand-in section of about 2 % camber the model gives 25 mm, a static margin a fifth of the U Surf's, and two points of glide, which is your report in order; the size of each depends on the real camber, which I don't know, but the directions don't. The other way up it would do the opposite of all three, so your report also says which way the camber faces.
4. The mast an inch further forward on the V2 with the same tail. That one the model does not explain: a V1 1050 and a V2 1050 balance within a couple of millimetres of each other relative to their own quarter-chord line. So the shift is in where AFS put the mount hub relative to the lift, not in the shape of the wing. If anyone has a V1 and a V2 of the same size side by side, the distance from the leading edge at the centre to the front of the mount flat on each would settle it, and I'd gladly add it to the notes.
5. How it scored against this thread, since a model nobody here has seen should earn its place. I turned 26 statements in the thread into checks the model had to pass, each with a number and a tolerance. 15 it reproduces: the 950 V2 against 1050 V1 low end (both reports), the 1050 V2 matching the 1050 V1, the 1150 V2 having the 1050 V1's speed with more low end, the weight effect, Jeroensurf's light-wind session on the 1050, the V2's better glide at cruise, all three of Jeroensurf's U Carve observations, the U Glide at the same mast position, sunsetsailboards' small stab taking more attention, the short fuselage loosening things, and a 95 kg rider's minimum speed on the same wing from another forum. 6 it fails: PWDW's 750 V2 matching the V1 850's low end (the model has it 0.7 kn short), the V2's top-end speed gain, the U Glide having the most glide, the 1 cm mast move for the small U Surf (right stab effect, wrong size), the 750 V2 with the 135 feeling like the V1 850 with its 142 (close but outside my tolerance), and the V2 wanting the mast an inch forward of the V1. 5 it cannot address at all: pump drive, breach recovery, turning feel, mast stiffness and the new fuselages. The fails are the interesting part: four of the six point at the same two things the model doesn't have, the V2's real section and where the mount sits on the chord.
Caveat on all of it: steady state, flat water, the stall numbers are where the wing starts to run out, not where a good pumper gives up, and the sections are mine not AFS's.
If anyone wants the sweep for their own weight and size, say so and I'll post it.
