GPS plots over 22 Kts

I had my gps tell me I was doing 23knots once, but I didn't have a computer cable to record it with.

I can go ahead and forge one up if that'd work. (I used to work for CBS but we'll keep that on the d/l mmk?)

No. I want this 100% pukka.

I know the T is fastest, just got to prove it....

Bout 8 years ago, so old rig T. We were shy reaching in Pittwater in 15kts of breeze and had a coach boat tailing us very close, He had this stunned look on his face the whole way accross the bay. when we stopped he told us we were sitting on 20 - 22kts all the way accross. And we thought we were just cruising!

This is my whole point I am trying to get over to these people who will not believe how quick Cats are. Few years back I did a race in the UK which is basically 30 miles down wind and then 30 back again and (after an upwind start) we got the the end of the Downwind leg in 1 1/2 Hrs (gybing down wind) - so 20+ kts as-the-crow-flies, but no GPS.

ho-hum.....

I have some off the CFR of 18mph..... upwind in 20-25

I'd have to check the downhill numbers.....

I am headed out this Sunday on a N20 with a good wind forcasted (upper teens). I plan on having the GPS onboard. I also have skilled crew. I may need some help with the ploting.

Barry, It plots best if you set the GPS to do "bread crumbs" on a steady basis, like every 30 seconds or every minute.

I have a track showing 18 knots but do skiffies have proof themselfs ?

I can have a look where I have the 18 knot track but it is not spectacular as this was one of the first tries and it was the first time we sailed together so we were not a oiled machine or anything. More speed was in it.

Wouter

I do not have a gps track that has consistant speeds in excess of 22 knots. But I hope that this video might help you state your case.
Bacardi Blast

It's a big file. You might want to right click on it and go with "save target as."

GARY

Here is a link to take you to my favorite catamaran video. It is large, so use your "save as" function.
Spitfire Promotional Video "Want one yet??"

This video, at times has a data box in the lower left corner of the screen. It has two values shown in it. The boat speed in knots is on the left, while the wind speed is on the right. At one point, the boat decelerates from 21.4 knots to nearly zero, in just about a second. 3.5 G-force is claimed.

Music is good in this video; two songs are used. Be sure to view both halves of the production. It is beautifully crafted.

An oh... these are only 16 footers, I think!!

And here is one very fast H16! Please, please right click and save only on this one! Please, right click and save. Right click and save

GARY

seend the Spitfire Video, it's the Biz....

AS for the GPS, depending on make, set it to sample 1 second rate, you will then get a good plot that you can download ti excel tha twill look something like this :

In about 10kts of wind BTW

Sadly this following makes the claims a little dubious :

>>At one point, the boat decelerates from 21.4 knots to nearly zero, in just about a second. 3.5 G-force is claimed

1 G = 10 M/s^2 means a decelleration from a velocity of 10 mtr a second down to 0 mtr a second.

21.4 knots = 10.997 = say 11 mtr/sec velocity therefor a decelleration occuring during a whole second would only constitute 1 G and not 3.5 G.

3.5 G however would stop the boat dead in its track within 11/35 seconds = 0.31 seconds. That is only twice the amount of what a human being needs to react to the the decelleration. It would stop the boat within distance x = 0.5 * decelleration * Time^2 = 0.5 * 35 * 0.31^2 = 1.68 mtrs or 5 feet 6 inches. from full speed to zero within 6 feet. That is quite a "wall" you are hitting. Shock forces of about 250 kg are pulling on each person sailing this craft during this manouvre and I see the skipper remain on the trampoline ?. The total force required to perform "hitting" this wall is (130+150+ some sailforce)*3.5 = at least 280 * 3.5 = 980 kg acting on the rounded and smoothed bows.

Anyone else find this a bit 'out there' ?

I have never seen a catamaran do a full stop from full speed within a boatlength, let alone within 6 feet.

Think of it, coming to a full stop within 6 feet would not even allow the water to hit the mainbeam from the moment the bows submerge OR when the decelleration is caused by the mainbeam, allow the beam spray or wake to pass the rearbeam.

One more thing

The kinetic energy inclosed in the crew trapezing would be sufficient to sling him upward in front of the mast (remaining upright) to 6 mtrs. Or level with the attachement point of the trapeze hounds.

What do you think ?

Wouter

In the tornado clip they say the best time sustained an average speed over the measured distance 12.53 sec of 27 miles = 12.07 m/sec average over 150 mtr. = 23.45 knots.

The Hobie 16 video claims 20 knots speed for the Hobie 16 on a reach.

The Spitfire video claims 27.2 knot max speed.

Personally I'm very skeptical of any speed claims over 20 knots and that includes the claims made by skiffies.

Personally I only trust averages over at least 5 seconds (preferably 10 seconds !). Shorter measurement spans are to susceptable to freak occurances of various causes. Not to mention momentary surfing of a wave or something.

While on the water it certainly feels like you're doing 100 at least but when you look at real measurements you are often disappointed. Breaking through 20 knots is quite a feature and you are often marginally in control. Any water that hits your feet will throw you of the boat at these speeds. Hobie 16's doing 20 knots or more. I want to see that and and see the GPS plot of two runs back and forth (currents !). Looking at the wake a Hobie makes in such conditions I doubt it. But that could be just me.

Here I have a Taipan 4.9 (165 kg on board = overweight, no spi, on a lake = no currents)) GPS plot in a good force 5 blow (20 knots). Geert and I were sailing the boat and were new to eachother never sailed together. Thing that surprised me was the fact that we achieved the same maximum speed on a 45 degree upwind beat + a downwind leg as we did on a flat reach. The wind was gusty and we were hanging on from time to time. Geert has only one functioning arm and our styles were conflicting here and there so it was a wild ride.

The cel width = 10 seconds. So each colom shows the averaged speed over 10 seconds. Therefor points 1, 8 and 14 show stretches were we averaged at least 28.5 km/u for 20 seconds = about 160 meters (about 15.5 knots). Our best average was 30 km/u = about 16.2 knots over 10 seconds = about 85 mtr.

When taking the light blue and red together at point 14 we have on average 26.7 km/u over 60 seconds = 450 mtr = almost official speed record distance and here was AVERAGED 26.7 km/u = about 14.5-15 knots in about 20-22 knot winds. It was gusty so min and max speeds may swing a little around this average but I don't think we ever came past 18 knots. All the mono's in this race where WAY behind.

This is the best I have. Other plots show speeds at less windspeeds (and therefor boatspeeds) and aren't of interest to you. The other times we or I went out in these strong winds we/I didn't bring a GPS unit.

Wouter

Wouter,

don't suppose you have the max of the red ones (28kmh is only 15kts+) ?

>>don't suppose you have the max of the red ones (28kmh is only 15kts+) ?

We have lost the max speed readout as that was not logged. I remember it as being less than I expected it to be. Hence my comment that I don't think we ever passed 18 knots THAT DAY. This is not to say that the boat couldn't be sailed faster just that we didn't do it that day and that we don't have any GPS plots/tracks of others day where we may have sailed faster.

As a Dutch person I'm very experienced in cycling and 30 km/u on a bike requires some very serious paddling. The speed sensation you get from that makes it feel like you are going very fast. Same with boats.

In all honesty I have yet to find any convincing proof that cats sailed faster than 23.5 knots under sailpower alone ever. Claims of 20-25 knot are mostly anecdotal and rarely, if ever, substantiate by dependable data. Often these claims are so badly supported that effects like currents (easily some 3 knots) and momentarily surfing of a large and fast wave can not be ruled out. Actually the tornado claim of 23.5 knots(as calculated from the vid commentary) is the only claim above 20 knots that has some credit. ALL others involved phrasing like :"We went really fast and when I looked at my handheld/etc GPS it said "**" knots topspeed, WOW !". The 5 or 10 second average may well have been significantly slower but is never reported.

We all know how dependable momentary acquired maximums are. Afterall they are derivatives of a measured travelled path and so some significant errors may exist if things like waves and currents can be assumed to not have influenced the read out. Averaging the speeds of a period of time is the only way to acquire dependable measurements. 5 seconds is the minimum timeframe for that.

Yet many classes claim regular speeds of 30 knots or even more. Skiff sailor make even higher claims.

Havig said this I think we could have travelled a little faster during the race where I supplied to plot from but not enough to reach anything near 22 knots.

I proposed that we contact the skiff sailors and agree upon a universally applied format.

Something like.

-1- we all set our GPS cel widths (average times or sample times) to 10 seconds.
-2- we regard the acquired average speed of these sample times as a measure for top speeds even though peak speeds may be a little higher as the min speeds are a little slower.
-3- We agree that this cancels out most electronic, alorgarithmic and freak off set and errors except currents.
-4- We agree only to acquire test series on lakes without currents or by validating the speeds on a return leg (2 legs opposite to one another.) In locations with currents this means that we average the speed of both runs to get the final measurement
-5- We most supply a traveller path plot with each speed data. Like I did. So we can see on what course the record was set and wether current or something was present.

This will also allow relatively cheap GPS units to be used as the sample time of 10 sec will average out most of the errors than the cheaper units are linked with due to their cheaper components.

Over time we will achieve a good picture of the differences and who is fastest.

Wouter

This cat will do 25+ knots, Mr Parlier says it will do 40Kts.
You dont need no GPS logs to see that this little cat realllyyy flies...
And yes, it IS a beachcat ;-))

http://www.parlier.org/hydraplaneur/images/images_evenements/139_ev12_010704parlier.jpg
http://www.parlier.org/hydraplaneur/images/images_evenements/170_ev13_230804parlier.jpg

Anyway, the fastest I've logged was 17kts in a gust going dead downwind with just the main. Although I am sure I've hit the 18-20+ mark more than once with the chute up. IMHO the times when you go fastest is when you forgot to take your GPS 😉

/* Tony_FX1
The Netherlands */

Nice piccies, but not quite what I am looking for.........

1997 Bermuda World Tornado Championship, during an event called the Bacardi Blast sprint. A timed run between gates that were 500 feet apart.

The Record stands at 27 MPH or 23.5 knots average over the 500 foot course. Completed in 12.53 seconds.

You acn find some footage here on John Forbes web site http://www.acay.com.au/~gonzo/tornado.mpeg

This was the days of the old rig with no spinnaker.

"This was the days of the old rig with no spinnaker. "

Looking at that video clip, I believe that`s a GOOD thing !!
Wonder how long it would have taken them to get it upside-down with the new rig & spinnaker on that course - much less than 12.53 sec is my guess.
Love the end, where Mr. Forbes (I presume) is just hanging around in the rigging.

Cheers
Steve

>>UK which is basically 30 miles down wind and then 30 back again and (after an upwind start) we got the the end of the Downwind leg in 1 1/2 Hrs (gybing down wind) - so 20+ kts as-the-crow-flies, but no GPS

Land miles or nautical miles ? Current ? How many gives where required ? Was the bottom mark perfectl downwind.

Land miles ? = average 17.4 knots
Current helping ? = deduct 1 to 2 knots => 15.4-16.4 knots
Bottom mark not prefectly downwind => more and more equate the 'as the crow flies" speed to real boat boat speed despite gibing downwind.

And this is why GPS readings are so important. Especially as the show what the current was by looking a drift right before the start.

Wouter

Simon,

On the Marstrom web site they caim that downwind the M20

See
http://www.sailcenter.se/administration/Boats/M20/index.asp

and follow the about M20 link

Perhaps you need to contact the company about this to settle your argument.

I am sure there are many on this site that would like to see the proof of this

All the best

Gareth

I know most of the discussion has centered around cats 20' and under but I thought this might be interesting to add. I copied and pasted this from the Aquarius Web Site (ARC Catamarans).

"In 1984 Bill [Roberts] started designing and developing the RC-27, a design which would set the standard for many boats well into the future. Throughout the 1980s and 1990s the RC-27 set numerous records in the US and Europe. In 1989 Bill, his son Eric, and Peter Zboyan set the record for the lowest elapsed time in the Miami Key Largo race at 1 hour 44 minutes for the 45 mile course, that is an average speed of 26 knots! "

If the average speed was 26 knots, can you imagine what maximum speeds they were hitting in short bursts? And this was on an actual open water race course ... not some 500 meters of dead flat water in a ditch or lee side of a sand bar. Must have been a wild ride!

Regards,
Bob

I have not only seen it, I've done it. It's called a pitchpole Wouter you should have known!

My G-Cat 5.7M pitchpoled well within a boat length. Once that front trampoline dug in, the bow turned submarine and the stern turned catapult. BOTH bows went in up to the mast beam and the boat hit a 75 degree verticle angle before laying over on its side.

Just to bring this back up the radar, I know have a plot of me doing 22.7 mph ~ 18 kts last weekend without the kite up and I am hoping to be out tomorrow too. Anyone else ?

I'm trying but weather overhere is not really helping. Either lightwinds or it is very strong and blowing from the North. It is bloody cold overhere. Only several degrees over freezing. We still have mild frost over night which is very strange for the Netherlands in this time of year. We are still wearing wintercoats. Has been like that for weeks. Water temp is just as low because the air temp was too low to warm it.

My best speed, with GPS on board, is still 16 knots. Was on a reach without a kite bank in 2003. Had one or two promising runs since then but GPS logger died. My logger has a very sensitive back light switch. When it is on than it drains to batteries in about an hour.

Can you publize your GPS plot Scoob ?

Wouter

OK, I will have to withdraw my claim of 22.7 as the GPS plot only records the actual average over the same course(I could take a Digital picture of the GPS Screen I suppose...), however I can claim 20mph (17.38 kts) for 24 seconds :

Paste of the plot log (edited for clarity, I can post all 566 plot polint if anyone wants):

Image from my PC attached :

Night all. Off to bed after spending the last 36 hours re-boulding (well trying to) my Hard disk on my PC.

See you in the later morning, it's 01:11 here and I am sleepy !

Personally I think momentary (display) speeds on a GPS are highly undependable. The minimum average time should be 10 seconds. I think your 24 seconds is small enough to get a good average speed reading. 17.38 knot (European Inter-17 singlehanded no spi) is the current top score.

What were the winds and sea conditions, on what course did you achieve the top speed (reach, broad reach?)

Thanks,

Wouter