Boardsurfr has just analysed my, Nina's and Stroppo's data from the good blast we had last Wednesday.
boardsurfr.blogspot.com/2019/
So it's fairly evident that Nina was on gear that was just too big for the stronger gusts.
But for me the big question is, would strop have gone deeper and faster on bigger gear, or would I have gone faster on a smaller gear adopting the "Stroppo curve" technique?
Interesting read, the problem with going larger is too fold. Harder to get into the course and more drag off the wind. As always it's a balancing act to get comfortable while going very fast.
The relitive sail sizing seems just about right from my experience. 
90Kg+ 5.7-6.3m, 75Kg 5.0-5.2, 60-65Kg, 4.4-4.7m always seemed to work in the 30-35 knots days here. (Cammed speed/slalom/race type sails)
All on speed boards of course.
All go down a size when it is 35-40+
Who knows if I would of gone faster with a bigger sail and the curve downwind is just me finding the right angle some of my lines go straight after a while once I've found the right angle of the dangle it's very easy to bare of to much to quickly and kill the power it feels like good control but it is not as fast as we know in this type of breeze the wind angle moves around a fair bit so you really need to sail by feel and alter your course accordingly.
Select to expand quotedecrepit said..
Boardsurfr has just analysed my, Nina's and Stroppo's data from the good blast we had last Wednesday.
boardsurfr.blogspot.com/2019/
So it's fairly evident that Nina was on gear that was just too big for the stronger gusts.
But for me the big question is, would strop have gone deeper and faster on bigger gear, or would I have gone faster on a smaller gear adopting the "Stroppo curve" technique?
Great analysis.
Select to expand quotestroppo said..
Who knows if I would of gone faster with a bigger sail and the curve downwind is just me finding the right angle some of my lines go straight after a while once I've found the right angle of the dangle it's very easy to bare of to much to quickly and kill the power it feels like good control but it is not as fast as we know in this type of breeze the wind angle moves around a fair bit so you really need to sail by feel and alter your course accordingly.
At 42 knots Strop it's not dangling any more 
Interesting read Peter and it's interesting that those that achieve 40s on a regular basis seem to of found a magic formula and keep hitting the mark while sailing less kms than most. For myself I'm still scratching my head as I hit 39.6 on the Tuesday night with a 7.0 but could only produce a 38.6 on the Wednesday with a 5.9 using the same fin/board combo.
Whilst Stroppo has a height advantage over me plus a couple of kilos we were on very similar gear with the exception of the fin where I used a Kestral 18 he would of had a bigger fin with less rake. Was the small difference in water condition the main factor here?
I actually did more speed runs than anyone else on the day but my speeds decreased as the day went on (possibly as the water levels rose) I'm generally a couple of knots slower than strop so probably only missing a knot of speed in the overall game. 
John, do you sail the 7.0 a lot more than the 5.9? I think familiarity with the gear and conditions is a very important factor. Stroppo and the other "regular 40-knot guys" probably have a lot more high-wind sessions under their belt than you.
Another factor may be that you are faster the more power you have. The wind was going down a bit in the afternoon, so that would explain your speeds going down. I noticed that many fast speedsurfers share your (assumed) preference for more power, while some prefer smaller sails and get the same speeds (even after taking body weight into account). A select few can get great speeds lightly and fully powered. I recon Stroppo is in the last camp, perhaps with a preference for smaller (or "just right") sail sizes?
Personally, I much prefer days where the wind builds, like when you sailed on Tuesday. That gives time to get the gear dialed in and the confidence up first, making it easier to not hold back in the strongest gusts. Maybe it's a bit similar for you?
Those Loft RBs of Peter and Nina have a fine leading edge. Good for cross wind but if you go too deep with a fine leading edge sail, it can stall not only loosing power but becoming unstable. If you look at Strop's sail it has quite a bit of depth up front. This is the way to go for deep off the wind. Although it makes it harder getting back upwind.
yoyo what you are saying makes sense, but the interesting thing about Stroppo's tracks was that he did not go downwind nearly as much as (for example) decrepit. I have felt the instability/stalling you described when going deep on nauti runs, but 125 degrees is usually not a problem.
At the Cervantes GPS challenge where Stroppo was second-fastest after Spottie (IIRC), I remember standing in the water and someone (Jonski?) commenting that Stroppo was not going as deep as others. That's what it looked like to me, too. But Stroppo also went closer to the shore than most others.
The Lofts are spec'ed for RDM and SDM masts, but take quite a different shape. They are a lot flatter on the RDMs (the ones listed on the sail as the suggested mast). On the SDMs, they behave like a very different sail. But I don't think I can blame the sail for being slow. The 5.6 I used when I was 6-8 knot slower than many others has done more than 50 knots in Luderitz - rigged on SDM, with Boro sailing, and with speed battens that we had to exchange when one of them broke.
I just noticed that the link Mike has posted goes to the 2019 postings, not directly to the post in questions, so it will drop as I post new stuff. It's already one post down. The direct link is:
boardsurfr.blogspot.com/2019/01/40-knots-or-not.html
