I have been lucky to receive an early sample of the new construction of the Quobba fins: a mix of carbon and glass fibers instead of only glass, with the same shape. Here are my impressions:
At first I was a bit skeptical, as I do not like too stiff fins. I am a kind of fin hoarder that can never find the will to sell used fins, the only exception were the FCII carbon fins (performers) that I found too stiff and re-sold: they made the board slower and "dead" underfoot for me.
I guess the slowness of too stiff fins is due to the fin resisting too much water pressure and creating turbulence, a bit like in the Oak and the Reed fable.
So I was a bit wary of carbon in fins. I guess I am not pro-level aggressive enough in my surfing to need very stiff fins. To be frank, I Quobba had better work first on quad sets than carbon versions.
On reception, by flexing them by hand, I was pleasantly surprised: the carbons flex less than the regular glass Quobba, but still have some noticeable flex. I'd say roughly half. Perhaps this is due to the FCS1 system, the small tabs providing always some flex? It may explain why I loved carbon FCS1 H3 nexus fins, but hated the FCSII ones...
My first test was on slow thigh high waves. I could not really feel a difference, but at least they did not perform worse than the glass ones. No slowness or stiffness experienced.
By today was classic Hossegor: powerful fast overhead lines, with offshore winds. And in these conditions, the carbon Quobba shone! The main advantage is the precise driving: I got positive, instant feedback on my legs pushes, providing a noticeably better control. I think I got more speed out of turns, and on fast sections, but it is only subjective, I don't know for sure. Anyways, the board felt like a rocket on these fast racetracks...
There was some chop on some waves, due to the strong offshore winds, but the carbon fins seemed to handle it as well as the glass ones, the ride was not rougher.
The fins were L fronts with a M rear, whereas I use an all-L set on this board. But I experienced no drift of the rear fin nor spinouts, the carbons seem to hold splendidly.
So, nice work, these are definitely an improvement on the standard fins in powerful conditions. I immediately ordered two more carbon sets to that I could equip all the boards I use in powerful conditions. But I do not feel worth it to replace the regular Quobbas on my boards for slow waves, where I like the extra flex and do not mind a less precise feel.
In a nutshell: Carbon Quobba are great for aggressive riders and/or good conditions, and offer no disadvantages otherwise.