OK, I just got back in from an hour on the Hobie 14 in 23G28 (I just called the local airport to check). To get the most accurate GPS speeds possible I didn't even turn it on until I had the sail up, ready to go. The unit I have is a Garmin Legend ( the little blue, $200 one) I tied it to the hiking strap and laid it down face up, reset all the speed/track data, then launched.
After 4 reaching blast runs back and forth across my lake (about 2 miles each way) it said the distance was 8.2 knotical miles with a max speed of 16.5 knots. These numbers seem realistic. I turned it off as soon as I got back to the beach so as to not mess up the numbers while moving it around on the beach. The tracks looked right on.
So, with my lazy, fat (185lb.) butt on the little, very old H 14, it will go about 16.5 knts. With someone who has bigger balls, is lighter and actually good at racing a newer H 14, with a new sail and foot straps, probably a couple knots faster. An Olympic Gold Medal crew on a Tornado, same wind, probably twice as fast, maybe 30+ knots?
It was all I could do to keep the lee hull tip out of the water and they both went uner on a couple of waves. I was trapping all the way at the back, rear foot on the hull at the top of the rudder and the other on the rear corner peice of the tramp, slipping and sliding every time I took a wave over the hull. I am going to add some footstraps and non skid to that thing before I try that again!
I did manage to do something I've never seen before, I'll call it a wheelie capsize. As I was tacking at the end of the second run (I did a jibe on the first and third) as I passed under the boom, the thing stood right up on the sterns! It actually blew over backwards!
I'm thinking WTF?? as I quickly crawled up the tramp, came down on the inside of the now sideways hulls, reached through the tramp lacing to uncleet the traveler and main, flipped the righting line over the top hull and waited for it to spinn around so the wind would help right it. As the mast came up I jumped up onto the low side tramp to keep it from going all the way over the other way. But I never got my hair wet

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Even though I stopped about 5 minutes for this drill and I had to stop once to get a rudder back down, the moving average showed 10.9 kts. Great fun but I wish I had something with straighter, fatter hulls to play on! That rocking chair nose dive with every gust is a real pain in the butt!