With apologies to Mary, who raised this question a while ago :

"I hate to revisit this topic after the last thread where I got a little upset about people saying that small catamarans (20-foot max) cannot go faster than 22 knots. Now I have to say that this claim about 33 knots also seems totally unrealistic at the high end. The following is quoted from a story on the US Sailing website:

"The Tornado sailboat has the ability to reach speeds of 15-18 knots upwind and downwind, and 33+ knots reaching!"


Having read the ensuing replies, I could only find one or two posts that stayed on topic, as usual it was hijacked and went off in a direction of technical gadgets and how to keep Ni-cad batteries working etc, but not much on the subject of speed, and how fast a catamaran can/should/would/could go. In defense of the hijackers, Mary did ask how we could get an accurate measuring method, so all the techno-device junkies came forward.

Here I will probably get some disbelieving folks, but here`s my take on things from one case.

“1 nautical mile = 1.85200 kilometers”
"A knot is a nautical measure of speed, one nautical mile per hour"


Almost every country has a “Round The Island Race”
South Africa`s version is not as exciting as the UK`s, it happens on an inland dam and isn`t really a long-distance race, unless the wind is very light. Then “distance” can become a different perception, how far you drift in one hour rather than a physical measure. The race does, however, attract between 400 and 700 boats, and has become a cult following.

From the organising club`s web-site :
“The record was set by Eric Cook and his daughter Julie in 1998, with a time of 1 hour, 1 minute and 27 seconds (24 nautical miles). Every boat finishing before the cut-off time of 17h00 receives a certificate, and we have approximately 30 trophies to be won. A special prize of R10 000 is up for grabs by the first boat to break the one-hour elapsed time mark.”

This record was set on an old-rig Tornado, before the new rig was introduced (in SA at least.), without a spinnaker.

That gives an average speed of 23,43 knots, over a one-hour period, including an upwind leg of approx. 4km, which works out to a distance of 5,65km upwind, or 3,05nm, when considering they had to tack several times, so assuming they sailed the distance to the island and then the distance back in a dead straight line, they would have covered closer to 25nm in the hour.

So, to open up the debate on “how fast can catamarans sail over a 500m course”, I`d have to disagree with some that the fastest a Tornado can sail is 23knots, since this speed seems to have been sustained over a considerable period of time. What`s more is that this is the official race time, I remember a few years ago that some Tornado and Hobie Tiger sailors broke the hour by several minutes, claiming an unofficial time of 49minutes, but on the Saturday before the race. This is a big claim, since it puts the average time close to 30knots.

So, unless the organising club has the distance all wrong, or their timing was horribly out, I`d have to believe that Eric & Julie sustained over 23 knots for an hour. Since they had to tack, gybe and fight their way through some 400 other boats (the catamarans start last), they must have reached speeds well in excess of their average to sustain that.
The rough distance from the North end of the island on the Vaal dam to the start line is 22km, measured on the road parallel to the shoreline. Double that for the return trip and add 4km for the upwind leg behind the island gives you 48km, or 25,91nm, so I`ll believe they`ve got the distance right.
So in my book a Tornado with old rig can sustain over 23-25 knots for long periods of time without the spinnaker, and must have reached speeds in the upper 20`s (ie 27+) at times. (Spinnakers would have been no use in this race, it was a beam reach to the island, a beat up the back of it, and a close reach back to the finish.)

I`m sure there are many other cases where cat-sailors sailed a known distance between two points in a given time, so their average speed over that distance can be calculated ? Then we don`t have to get into lengthy conversations of how GPS do/don`t work, their accuracy, battery life, etc ! What about historical data from legs of the Worrell / Tybee 500 / Atlantic 500 races, which are sailed on damn fast boats ?

Steve