Ok I'm not looking for "there was this one day...." stories here.

Those of you with GPSs what speeds do you typically see upwind and down? I'm currently modelling the DS16's pitch motion and some real world values would be helpfull.

Thanks SC

one day, at band camp...
18-19 downwind, solo on the blade in slight chop... not really sustained for a long period though... I imagine you could really get going with completely smooth water but that would be kinda odd to have the wind to do it but not the water.

"standard" pointing speed is 9-10kn I would say, in 10-15 knots.

Last weekend I was doing 10-12knots upwind and 16-18knots downwind in about 15knots and flat water. This was my first time on the boat and i was sailing rather conservatively though.

When looking at my logs I usually hope to see 13-14 MPH up wind (12ish kts) and downwind around 25+ average (20 kts) and I sometimes get it really right and get 30+ MPH so that's around 28kts.

I had one 9 second run at Mumbles 33mph which converts to 28.67kts <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Looking at the plot, it's just before I fell in!!!!!!!!!

On the only two occasions that I've carried the GPS (both times winds were around 18-20knots) I was getting in the region of 9-10 knots upwind but downwind with spin was giving 16-18 knots with short bursts (2-3 readings) of 25knots plus.

Same here,

Upwind in the range 10-12 With sufficient conditions although this sadly doesn't include flat water in my situation (never took a GPS with me in high wind, flat water conditions)

Downwind, 16-18 knots; again with some waves.

This ratio corresponds closely tho the ratio I had measured between upwind and downwind speeds in the F18's class a few times. Also it is my experience that F16's are almost as good as level against F18's.

I always imagine that one or two knots could be pressed out of the F16's with flat water and a steady 15 knots of wind Sadly these are conditions I never encounter at my club.

I noticed at the Olympic Tornado medal final that these guys/boats do 12.5-13.5 knots upwind in a good seastate and 17.0-18.5 knots downwind. Sufficiently well sailed F16's are always close to the F18.s, F20's and Tornado's; so this Tornado data could well be a good upper limit for the F16's. At least on the (measured) data that I have, these numbers should be pretty close to the real life parameters.

Good luck with the DS16 ! I looking forward to seeing the final result !

Wouter

Tornado medal race. Sizable waves and only 13 knots of breeze. The guys were also trying to slow the boats down on the downwind.

From my experiences with F16s on my F18, the F18 is slightly quicker upwind. Downwing the sloop F16 is close to the F18 whilst the cat rigged F16 is simular speed but slightly better VMG. However, the sloop F16 and F18 have an advantage turning corners.

14s upwind. 16 to 18 down. Lots of crashing. Still waiting to go out in more than 15 knots of breeze! Whoops, wrong forum...

Well it depends TFC

Is that a photo-shopped image or is that a real -double moth- i.e. foiling cat?

Hi SC,

I am not sure if I understood your question right, but if you seriously build physical model I can support you with GPS data from a Dart 18 (cat and sloop rigged), a Javelin 16 with and without hooter and a Tornado (cat and sloop). However I am lacking reliable wind data to this measurements. Let me know, if this is helpful for you and I can send you the data.

If this posting is just an ambush I take knowingly the bait:
Top speed of fast beach catamarans is around 16-18kts depending on size, weather and your GPS setup (e.g. over what time or distance the speed is measured). Some claims like 25 or 30kts are just legends or examples for GPS inexactness...

Cheers,

Klaus

Hello,

I do have quite a lot of tracks from my blade, and also some tracks of other Blade's.
Upwind in good conditions is about 11 knots. Range would be 10-13 knots but 13 knots is only possible (at least for me) if there is some current involved or when overstanding the layline so not really upwind anymore.
Downwind between 15 and 18 knots. 18 only in relative smooth water, and still is an exception. All tracks 2-up.
Sure i've seen more speed on the gps or later on a track, but those were defintely "spikes". Am curious if anyone (on an F16) could hit 20 knots for say 30 seconds or more..

Most modern GPS units do have already smoothing algorythms to do away with the so called spikes, but due to our slowish speeds the actual GPS positional error can cause unprectable results. Have a look at the actual NMEA data stream if possible and you can see an additional field which gives the actual GPS error at the time of the sample or just eliminate the really fast sample points and do a bit of " smoothing " yourselves to get more accurate tracks.

Klaus,

this is to support some computer modelling. Its very easy to become complacent and rely on VPP results but I prefer to calibrate against "real world data".

With the info presented above I can now target 10-12 knots when optimising the up wind hull form and 16+ for downwind. The truth is I could have guessed this based upon F18 and Tornado experiance, but its nice to see it written down.

Hi SC,

if you want to calibrate against other boats to confirm your model, here are my numbers:
Dart 18 cat double handed, strong wind, flat water: 17.3kts
Tornado classic double handed, strong wind, waves: 17.9kts
Javelin 16 with hooter, medium wind, flat water: 16.5kts
all numbers are over a time interval of 10s and there was no significant current. These are top speeds of course.
For the windward legs, I have to dig in the data. Let me know if you need speed and vmg, and I will dig them out.

Cheers,

Klaus

No that is enough. I'm not using them for VPP work just to get a feel for the boat's actions through waves.

Shopped.

Say it aint so! Dougie is getting ready to post that pic ad nauseum! Shame on you TA.

LOL, get it over to SA before Doug does!!!!!

Hey Steve,

you have to much spare time since you sold your Cap. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
I think it would be fast though, only problem with them Moths, not enough hulls <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />Or enough hull length for that matter. <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />