PY / Top Speed formula?

Mean speed around a course should be proportional to 1/PY, but the question actually asks for top speed.
Top speed will vary by more than the ratio of PY I think?

I believe RS400's have been GPS'd at around 20knots top, and B14's at about 29?
That's near 50% for only a 9% difference in PY 870 vs 947

It would be interesting to look at the polars and see what the VMG's were, assuming it was a true leeward leg.

Originally posted by RS400atC Mean speed around a course should be proportional to 1/PY, but the question actually asks for top speed. Top speed will vary by more than the ratio of PY I think? I believe RS400's have been GPS'd at around 20knots top, and B14's at about 29? That's near 50% for only a 9% difference in PY 870 vs 947 It would be interesting to look at the polars and see what the VMG's were, assuming it was a true leeward leg.

Sounds like a load of s**t to me. Top speed so far of a moth in UK waters is 30.6kt (10 sec run at 28.1kt), I very much doubt a B14 will hit 29kt! I thinking about 20 ish max for a B14 and probably about 15/17 for RS400? (it always feels a lot faster than you think). I've done about 25kt in an Extreme 40 and that was seat of the pants stuff.

EDIT: Maybe a 400 is a little quicker than that? I've never pulled out much downwind against one in a B14 in a blow...

EDIT 2: Are you going to go quicker in a blow without the kite up, bearing in mind we are not looking for top leward mark VMG?


Edited by tgruitt - 13 Mar 13 at 5:53pm

Originally posted by tgruitt Originally posted by RS400atC Mean speed around a course should be proportional to 1/PY, but the question actually asks for top speed. Top speed will vary by more than the ratio of PY I think? I believe RS400's have been GPS'd at around 20knots top, and B14's at about 29? That's near 50% for only a 9% difference in PY 870 vs 947 It would be interesting to look at the polars and see what the VMG's were, assuming it was a true leeward leg. Sounds like a load of s**t to me. Top speed so far of a moth in UK waters is 30.6kt (10 sec run at 28.1kt), I very much doubt a B14 will hit 29kt! I thinking about 20 ish max for a B14 and probably about 15/17 for RS400? (it always feels a lot faster than you think). I've done about 25kt in an Extreme 40 and that was seat of the pants stuff. EDIT: Maybe a 400 is a little quicker than that? I've never pulled out much downwind against one in a B14 in a blow... EDIT 2: Are you going to go quicker in a blow without the kite up, bearing in mind we are not looking for top leward mark VMG?

Personally, I have not got around to fitting a GPS to any dinghies, but I've been paced in the 400 at over 15 knots sustained, while needing to look for height rather than speed. No tidal stream involved, clocked by a rib following me for probably 1/4 mile. I find the RIB driver's statement that I was doing over 15knots to be credible. It was in the harbour, in a Northerly, but with some waves, I guess the fetch is 3 miles or so, so the kind of waves you might get in a fair sized lake.
I know I've been faster in the 400, and I know there are faster sailors than me.
There are certainly people who go out in more wind than we do.
The 20knots I quoted was a vague memory of GPS speeds that used to be on the CA website, so it's hearsay, but ties in with what I've seen.

I think the B14 number is something I've read, not my own observation. I think a similar 'what can you get on your Garmin' game.
I've chased a few in RIBs and could believe the number if everything fell into place.
It's different from what you can do on demand.
If this is to be any sort of contest, we need to be clear about the timeframe speed is averaged over, it's quite a lot tougher to average over a mile than the duration of a gust, and jumping off a wave might get higher numbers still!

Moths have a very low PY, but they are stupidly fast upwind when other boats are only doing 6 knots. I could believe their top speed is not as impressive as their PY?

There must be people out there with a lot more data?

FWIW, the most memorable time I've thought 'this is the fastest I've ever been under sail', probably would not have won on GPS, as we had about 2 knots of tide against us, giving a wicked short sea to jump from wave to wave. I really was getting concerned about being able to turn around or take the kite down.

Anyway, what models of GPS store a peak speed sampled over a sensible time/distance?

Originally posted by 2547 Originally posted by iGRF  Strava is an app the roadies use, I love using it on the sea next to where they ride, it really freaks them out. Especially when they can't come and get a KOM (King of the Mountain) it's like a rider challenge you could do it on your water set a course between two fixed buoys and challenge each other.. Strava is a website used by those too afraid to enter a real race ...

So not unlike PY- a spreadsheet for those afraid to enter a proper race also?

Originally posted by RS400atC I think it's a shame people don't run some 'normal' dinghies through the Portland speed traps.

It used to happen, but the results were so embarrassing and so at variance with the big fish stories that they gave up. I think an FD managed 11 knots or something. Nowadays the entry list is full with board and kite sailors.