What's the fastest human powered watercraft?

K1 WR at 1000m is 3:21. Single scull record at 2000m is 6:30. Unfortunately they don’t compete at the same distance. They are sort of the same speed. It’s not like comparing SUP and k1. On the other hand, a scull in a 1000m kayak race could come across the finish line with an impressive 5 second lead and then carry on and do another 1000m even faster than the first kilometer.  I have to say though that when I looked up those records was surprised the gap wasn’t bigger.  I would have expected the scull to be much faster than it is. 

Hmm, single scull length is 8.2m
K1 length is 5.2m

Yes, the single scull should be a lot faster. I suspect they have hit the limit where skin drag is overtaking wave-forming as the major limiting factor.

As both a rower/coach and paddler, I dug into this a bit a while ago...

Basically, rowers can't produce the same explosive acceleration or achieve peak speed as quickly as a paddler can- the primary limiter being stroke rate (boat weight also probably plays a role- Olympic K1 kayaks are 10-12lbs lighter then a racing scull by design rule). But as the distance increases, the greater efficiency of the rowing stroke takes over. 

For roughly equivalent athletes, the K1 will win to distances somewhere around ~250-300m. Between ~300-500ish the two will be very, very close. And past 500 the rower will start to gain an ever-increasing advantage. This holds true as you add athletes (ie, K2 vs Double or K4 vs. Quad). 

Interesting youtube of a (totally informal) race between a couple of French athletes as an example... 

That is interesting Sam. I wonder what would happen if the k1 was not length limited? Making a k1 longer i think would make it a bit slower off the line but a bit faster at top speed. 

I'm a rowing coach, not a hull design expert, but I suspect any difference would be marginal at best. I think the hull designs have been pretty close to optimized both in K1 and in rowing. I think the majority of the difference you're seeing has to do with technical/physiological factors vs the design of the boat- although I DO think that the weight makes a difference at the highest level.

Has nobody ever tried to PADDLE a ROWING hull? Unfortunately our relation to the neighboring
rowing club is not good enough to ask them for a naked boat, and up to now I
couldn’t get my hands on a cheap one to buy. I would love to see (if need be
with a small outrigger for stability) how fast an average paddler can get in a
boat with such a little wake, though the results surely will be different for
the top athletes.
By the way, I remember there were kayaks longer than 6 m for
long distance races, but somehow I cannot find neither the shapes any more nor
any results?!

Extra length on a  K1 may not buy you anything. When I interviewed Ted Van Dusen a couple of years ago for an article in Canoe News magazine, Ted (who produces rowing shells, K1's, and the Mohican flat-water ski)  told me the Mohican was as fast as a K1 up to about 8 mph, at which point the K1 would be faster. This surprised me, since I assumed the longer hull length would be faster at higher speeds. He explained that a strong paddler in the shorter K1 could power past the theoretical hull speed, but it would take too much power in the longer  Mohican. 

The formula of 1.34xsquare root of waterline length gives a speed of 10.3kph for a K1.
Since even a lame duck like me can sustain (for over an hour) 11kph and sprint at 16kph, a modern K1 isn't operating as a classic displacement craft. So I don't know what rules apply here!

mrcharly wrote: The formula of 1.34xsquare root of waterline length gives a speed of 10.3kph for a K1.
Since even a lame duck like me can sustain (for over an hour) 11kph and sprint at 16kph, a modern K1 isn't operating as a classic displacement craft. So I don't know what rules apply here!

This idea that a displacement boat can't go faster than it's hull speed is not actually a hard rule,  more a rule of thumb.  What's happening if you go faster than the hull speed is that the wave making resistance start to rise fairly sharply - nothing more dramatic than that.  For many types of boats the rise is so sharp that, in practice, there's no point in trying to go faster - even a little higher speed would require an enormous increase in fuel consumption. But given enough power, in principle, any boat can go faster than the hull speed. And if the length of the boat if big compared to the size of the boat otherwise (typical of kayaks, esp. fast ones), the rise in wave making resistance won't even be that sharp, in which case going faster than the hull speed isn't even that hard.

And this - for  bit of fun Rowing 4 vs K4 in Melbourne a few years back: