I think one of the common misconceptions is that as recreational catsailors, we tend to take the fastest speed reading of our GPS on a given day and indicate that as the potential speed of our catamaran. While I'm no speed demon, I'm sure there have been times when My boat is hurtling upside down through the air that it seems faster than it really is. Notwithstanding that, I think the discrepancy between personal speed experience and the Quoted capabilities of our boats is basically a function of how we measure it.
As performance oriented sailors, we tend to think in terms of our best peak performance, not some averaged time over distance calculation that reflects not peak performance capability but something entirely different, averaged speed over distance. That's not for me. I'd rather tell the story that once I made my cat go 30 than if you averaged out all my true speed while I was racing on my cat. It would include those days with no wind, sailing the drifter, maybe time on the trailer, or number of leaves collected on the tramp over a season on those days I had to work, and that time I was late for a regatta driving 85mph to get to the start line on time. Averaged speed doesn't reflect performance capability. & who really wants to be average anyway?
All that considered, think I'll stick with remembering that time I went the fastest, & yes I was probably upside down and in the air, just for the scientific purpose of trying to eliminate that friction with the water component of the equation.
CARY