HELLO to all catsailors !

In a previous topic named "speed", WOUTER replied about maximum speeds that could reach beach cats...and supposed they could hit sometimes 30 kt !

Well, the only reliable figures that were registered decently came from english Weymouth & french Brest SPEED WEEKS. These 500m track average speeds were recorded with the help of the ISAF's WSSRC measurement devices, including cameras with virtual lines and high precision chronometers.

The highest 500 m speed ever recorded for a standard catamaran was at Brest on a Tornado skipped by Yves LODAY which reached 21.34 kt. All other beach cats, HC 16, NACRA 5.8, Supercat were hitting always 18 kts to 20.5 kts approximatively.

Standard catamarans could hit 1.2 to 1.5 times TWS at the maximum polar extent around 115 to 125° TWA, with a flat drifter, high-ozed sails and a lot of twist in main !

The quickest "beach cat class" is certainly the "C-Class" with average speeds of 22,5 to 23 kts on a broad reach course of nearly 2.5 miles in ONLY 12 kt TWS ! I was following 1991's LAC event at Melbourne with Christian Février, the french reporter and the boats could reach easily 2 times TWS with their double-slotted wings !

Even with "C-Class", standard hulls are progressively sucked down in water dur to hull's curvatures and the boat stop accelerating when the Propulsive Force reaches 1/3 to 1/3.5 of the maximum Side Force that could hold the cat. Duncan Mac Lane himself told me that his "Patient Lady 5" never run over 26 kt !!!!

FRIENDLY YOURS,
Frenchie

Good post ,-thanks Frenchie ,

http://www.speedsailing.com/

That must have been so much fun to see and experience .
The C Class specs as I recall are 25 L -14 FT b -300 sq ft Sail Area . some standard sails ,-some wing sails ,
these certainly have more speed potential .

Funny side note ,-our current P-rating has a dpn handicap number for C Class catamarans at {60.5} ----and for comparison the Inter 20 at 59.7 ,---the inter 20 being somehow faster !!! --

Hope your not laughing too loud ,

Happy New Year -
Carl

just throwing this out there - were those speeds with spinnakers? The Tornado has only seen a spinnaker configuration recently.

500m is a long way to average 20+knts under the condiotions of whatever day they decide to run the trials on. I'd say wooter is not far from the truth. I have seen first hand a Nacra 5.5 w/spi steadily running at 26.??knts under GPS (more accurate than most would think). Years aggo I saw an article in a "Multihulls Mag" stating a SC20 hitting 33knts ?? One more ... The record for sailing around Texel is I think about 2 hours 9 minutes for what they say is a 60 mile trip. Oh and that was also a SC20. Not sure either what is realistic for top speed on a cat but I hope to find out next summer :-)

Marc ... yeah I guess another frenchie

Hello dear Marc,

When speed topics come out, there's a great stuff of SILLY FANTASY that also surges out from minds...

Of course, with very flat waters, a good drifter that pushes well, the crew hanging back with their feet near the transom, +4° bow-up trim, 25kt could be hit sometimes. The spanish Olympic Team was a specialist of "everyone sitting back the rear beam" attitude to make Tornado planning and so go beyond 21 kt...

14 years ago approximatively, a inter-series Challenge was put up by an aussie newspaper to point out what's really the quickest dinghy down under. 18ft skiffs, Tornado with spis, NACRA and so on were all here...with "The EDGE", the 1987 C-Class of Lindsay Cunningham...when the first Tornado crossed the line, C-Class crew was enjoying big fresh "FOSTER's" cans at beach's bar till 13 minutes....

BUT 33 kt, it's PURE FANCY !!!!! I have reliable speed records on ORMA 60 big trimarans like SODEBO, GROUPAMA, ect... and maximum top hit was 32.4 kt !

I am ready to register anyone with a SC 20 that could hit 30 kt and send him a "Cordon Rouge" MUMM Jumbo Magnum Bottle of Champaign !!!!

FRIENDLY YOURS,
Frenchie

The Tornado class held a Worlds in Bermuda in 1997, after each race they had a thing called the Bacardi Blast, they had set a 100m course up just off the harbour wall, on the faster days it was boling offshore 20 -25 knots, water was perfectly flat. It was a beam reach and most teams recorded speeds of around 30 mph I think the top speed was a about 33. I don't know how acurately they measured the course, I was surprised at the speeds, but they were all consistent.

John

Frenchie...You indicated in your first post that a catamaran's speed is limited by the hulls being 'sucked' down into the water due to the hulls curvature. I would have thought that the higher the speed the more the hull would be pushed up out of the water, even curved hulls like ours. Can you explain please...Thanks....Dan

Hello Frenchie-

Having owned a Tornado, SC20, & ARC22; I can say that I never hit 30knts over the last 35 years. Last year [on a demo sail on my ARC22] we hit over 25-27 in a real blow [20-30] on flat lake water on a close reach in lee of the dam. The water was absolutely flat. The reason I say this is because a mechanic working in a Cigarette Awesome was following us back to shore. He clocked us at that speed??? I have no way of knowing how accurate that reported speed was but he races that boat alot and did appear to be moving at the same speed we were. I asked Curry if he believed that speed could be reached and he indicated yes.

I have heard claims of going 1.5 times the wind speed but have never experienced it on the cats I have sailed.

thom

,-great posts by all ,-

On speed theory and comparing performance of catamaran design --
Is there a generally accepted formula in design that compares all small cat design based on L B W and S A
Length Beam Weight and Sail Area

Numerous partial comparisons are made ,-weight to sail area ratios ,-stability and righting moment with sail area . etc.

this is listed on the Texel site
There are 20 elements of speed, according to Olin Stephens (1972).


length
sailarea
displacement
prism. coeff.
asp. ratio rig
ratio main/jib . .
beam
wetted surface
center of effort
draught
ballast
combined 1 - 12
fulness ends
weight distribution
freeboard
windage rig
motor
material
course stabil.
steering stabil

6.

There are 7 elements of speed which have nothing to do with the design.

helmsman
crew
organization
condition of sails
condition of bottom
tactics / strategy
luck
7.

Follow the "KISS" principle, "keep it simple stupid", for formulas. There are 4 formulas available to approximate the performance. Bruce nrs (1967), IOMR (1968), KSP since 1976, Texel Rating since 1984 Edmund Bruce, pioneer of Amateur Yacht Research Society, died 1973.
IOMR = International Offshore Multihull Rule (California, 1968).
KSP = Kelsall Shuttleworth Performance. (MOCRA formula, around 1978).
TR = Texel Rating by Nico Boon, 1984, slightly modified in 1993.

8.

IOMR, KSP and TR use length, sailarea and weight (displ.) only..

RL = rated length, RSA = rated sailarea, RW = rated weight. (kg.).

General form of these formulas : 100 / (c * RL p * RSA q / RW r).

Bruce (metr.) =2.5209 * RL 0 * RSA 0.5 / RW (1/3 ).
Bruce (imp. ) = 1 * RL 0 * RSA 0.5 / RW (1/3 ).
MOCRA (metr.) = 100 / (2 * RL 0.5 * RSA 0.5 / RW 0.5 ) .
MOCRA (imp. ) = 100 /(0.5 * RL 0.5 * RSA 0.5 / RW 0.5 ).
TR (metr.) = 100 / (0.99 * RL 0.3 * RSA 0.4/ RW 0.3)
TR (imp. ) = 100 / (0.3397* RL 0.3 * RSA 0.4 / RW 0.3).
IOMR (metr.) = 100 / (1 *RL 0.311 * RSA 0.42 / RW 0.318).
IOMR (imp. ) = 100 / (0.3275 * RL 0.311 * RSA 0.42 / RW 0.318).

IOMR here, is a "translation" into a powerformula of the IOMR formulas.

9.

Above Beaufort 5 or 6, stability of a design is the limiting factor for speed. A rating has to be calculated then by using the smaller sailarea making heeling moment = righting moment. No other formula required..
In very light winds use TR (metr.) with c = 0.89 and RSA ^ 0.5..
(rev.7/96).

end Texel -info

A different approach to rating catamaran design in concept is to have a base equation that does not attempt to handicap design ,--but only compare it to scale of design variation of
L B SA and W .
This would provide information on the most effecient design type in each size for racing , results varying with race conditions and teams abilities as always.
For handicap racing an efficiency factor could be added to this base equation .
This may be based on improved yardstick system numbers ,Again as a percentage of this base rating applied to handicap racing only.
The base rating would provide a beginning number for new design . Be readily available to calculate modification of sail or spin sizes .Could be applied accurately to distance racing w spin non spin classes.

Ideas -concepts added -
thanks

Dan

the reason cat hulls are sucked into the water is that as they go forward they displace water. Some of this goes sideways and makes a wave and some gets fired up in the air making spray. Newtons first law, every force has an equal and opposite force applies here. So if the hull is shooting water up in the air, the water is pushing the hull in the oposite direction.

John

Hello to Dan Ward & Carl-Sail6000,

Thank you indeed for your enthusiast and curiosity...

About hulls that are being sucked down at high speed...well, it's rather complex...the speed-pressure Bernouilli's law coupled fields that build up around slender hulls are divided into 2 main domains ( with a physical continuity between them of course ):

1st domain : the neighborhood of free surface that is Froude Number dependant, Froude = Vboat / sqrt( gravity x LWL ) and from where most of the waves and spray generating phenomena originate.

2st domain : The "more constantly" deeper immersed part of the hull where the pressure-field remains more stable ( not completely, it would be too simple and stupid...)

So, if you take a look at a standard Tornado or NACRA 5.5 hull, the 2nd domain is the keel line and the middle sections, buttocks and waterlines that all show a certain degree of curvature...it's like the bumped upper side of a NACA cambered profile running upside down...

When the hull, an "upside down cambered slender body" is running into water, low pressures establish themselves just at the locations of higher curvatures and especially back them. This leads to a "negative lift", i.e. a suction that could reach beyond 20 kts, 15 to 20 % of total displacment..its value increases at a rate of speed squared ( what is called dynamic pressure )

The boat's total apparent weight becomes 875 lbs ( or more )instead of 725, and it dives even more.

About the huge amount of SPRAY, the previous reply is also quite true...all the water that is thrown up in the air contributes to a ( few percentage however ) more diving attitude...and the final "coup de grâce" is given by the propulsive force moment from the rig that buries even more the fine entries of bows and increase the whole vicious circle...that STOPS ACCELERATION !

I have read with enthusiasm what Carl-Sail6000 tried 17 year ago but some explanations about his concept seem not very clear. Noticeably, what's the interest of extreme canard bow rudder foils and high canted bottoms ?

Could Carl post some pics of his marvel boat ?


FRIENDLY YOURS,
Frenchie

Ya know- this is really quite a funny post. Have you noticed that some of you mention mph ( mile per hour ) and others mention kts ( knots ) and that there is considerable difference between the two?

I have little doubt that some beach cats have managed to hit 30mph, but I find it difficult to believe they've reached 30kts.

And powerboats, especially big racing ones, tend to be calibrated in MPH so the average spectator can accurately understand and compare the speeds involved.

Here's a question for you- at what speed does the Hobie Trifoiler cavitate and come down off the foils? Is it in the 40mph range, or 40kts range?

Hi Frenchie

You,ll find a number of accomplished catamaran designers post occationally here on Catsailor along with a number of others like me who just enjoy design ideas and discussion more from a sailing amature design perspective .
Marc has a really good looking project going as you can tell from his section drawings on his post pic . John is a really excellent designer builder from the U K and has a number of excellent catamaran designs to his credit. The Supercat designer Bill Roberts will often post information . We have a number of other really interesting posters that build boards rudders masts and some boats . Dave C built a foiler A Class cat , really interesting project.
Many brilliant people who sail catamarans in all fields.

Enjoy discussing design ideas ,-some are just for fun.
The older boat was an early attempt at something too experimental . You learn a great amount from the experience.I have some old 35 mm slides ,thats about all.
What I was trying to descibe in the other post was a newer concept for planning hulls with more cant along with forward molded in foils .
Pure foilers seem to fall off plane and break ,or have a difficult time in seas . Think the ideal hull shape may be a planning type with smaller forward foils that will not be subject to breaking but still provide some lift .They would also benifit C E to CLR with the chute up allowing a longer spin pole ,increased luff angle for the chute more like skiffs, that would also really help provide lift and still have a reasonabley balanced helm.
The ideal amount of hull cant may be much more than is currently used , the flat bottom forward hull sections of this type of design may use a small foil that would be an extention of it increasing the area for lift to a sufficient amount . Without having huge forward planning hull form .

Enjoy ocean distance racing so like design for that purpose.
Sailing is just a fun sport , though did race ProSail and the Ultimate Yacht Race series in 88 , Professional racing series .--pretty tough to make a living sailing or racing though some do.

Just a fun sport to partisipate in-- Fun to dream sometimes .
Really am getting the bug to build one again but will just have to settle for forum discussion for now. I have learned a great amount .

Hope you will post more often
we need more good design info .
All the best
Carl

Hi Syc

Was thinking the same thing ,-10 knots =11.5 MPH
Killometers also to convert ,-miles and nautical miles ,-
knots are in nautical miles --not mph ,-etc etc -
It is confusing and people often confuse the terms or forget to convert one to the other and misquote speed .

How fast are the Tri Foilers ,-

Carl

I always tell folks that if they want to brag, just convert to MPH (30 mph sounds a good deal better than 26 knots.)

You know, you should realy sign your posts with 'Frenchiely yours' :-)

As I pointed out, I am not ready to bet my life that anyone has hit >30knts on a <=20' cat. Just having fun with this :-O

From what I understand speed trials have mostly been a measure of average speed of 2 runs, one in each direction over a 500m dist (total 1km). This is not nesc an indication of top speed in any way close.
In the same respects, if a boat can travel ~695 nautical miles in 24 hours what would you say it's top speed could be.

"Longest Distance Run in 24 Hours
By any yacht, any number of crew
Maiden 2 owned by Tracy Edwards GB. Sailed by Brian Thompson, Helena Darvelid, Adrienne Cahalan and a crew of 7, Catamaran, 33.5m, North Atlantic, 12-13 June 2002
694.78nautical miles, 28.95 knots. "

******* Just to bring figures up to date(http://www.sailspeedrecords.com/500.html)

ISAF / WSSRC Current World Records: 500 Metre Course
Class Name Boat Speed Date/Venue
10 Sq M Thierry Bielak, FRA Windsurfer 45.34 kts Apr 1993, Saintes Maries
10 Sq M Women Babethe Coquelle, FRA Windsurfer 40.05 kts July 1993, Tarifa
A Class Russell Long, USA Longshot 43.55 kts Jul 1992,Tarifa
A Class Women Caroline Ducato, USA Longshot 17.81 kts Mar 1992, Brest
B Class Simon McKeon, AUS Yellow Pages 44.65 kts Feb 1993, Sandy Point
C Class Simon McKeon, AUS Yellow Pages 46.52 kts Oct 1993, Sandy Point
C Class Women Jean Daddo, AUS Yellow Pages 17.38 kts Oct 1993, Sandy Point
D Class Navarin/Columbo, FRA Techniques Avancees 42.12 kts June 1997, Toulon
Outright Simon McKeon, AUS Yellow Pages 46.52 kts Oct 1993, Sandy Point


The Course of Half a Kilometre(I know the 2 run thing isnt talked about here just something from the past)






1. General

The purpose of these rules is to enable attempts to be made on the World Sailing Speed Records in any part of the world under comparable conditions. They do not form the conditions of any prize or trophy, nor are they sailing instructions.

World Sailing Speed Records can only be established under the jurisdiction of the ISAF / WSSR Council, who shall appoint ISAF / WSSRC Commissioners to monitor all record attempts. Only Commissioners directly appointed by the Council shall have this authority. (See Rules 12 and 13.)

The official language of the ISAF / WSSR Council and its Rules is English.

The record in each class shall stand until it has been exceeded by the appropriate margin. Every request to ratify a record shall be considered in time and date order. The time used for this purpose will be Greenwich Mean Time. The time the competing craft enters the course will be considered to be the time of the run.

2. World Records

The World Sailing Speed Record will be held anywhere in the world by the skipper who establishes the fastest speed which is ratified in accordance with these Rules.

In addition, records can be established in the following sail area divisions:


10 sq. m. Class - up to and including 10 sq. m
A Class - from 10 sq. m up to and including 150 sq. ft (13.93 sq. m)
B Class - from 150 sq.ft up to and including 235 sq. ft (21.84 sq. m)
C Class - from 235 sq.ft up to and including 300 sq. ft (27.88 sq. m)
D Class - over 300 sq. ft


3. The Course

The record shall be established over a minimum of half a kilometre on water (not ice).

The course may be defined by posts and transits ashore, or by buoys afloat. Transits shall not converge.


10. Crew

At least one person shall be on board from the moment the yacht acceleerates from rest until she has finished her attempt.

All competitors shall be positively buoyant during an attempt. Weight vests and weight harnesses with a specific density greater than the water sailed on are prohibited.

The highest speed I have known the Tornado to go was at CORK 1975.
A 40kn storm hit when the the fleet got to the reaching leg.
The peak of the storm must have hit, when the leaders got to
the jibe mark. At this mark a couple boats lost their new windward side stay,
one of them was Reg White who released the other stays, so as not to damage
the boat from the mast. Notary was there on "Salt Water Wine", Zutec & Smyth
must have been there too.
Anyway a Canadian destroyer radared the fleet at 28kn average.
I couldn't believe it either, that's 33mph average.
At that speed the boat was no longer in the water it went like a
skipping stone from crest to crest (~9 foot waves(3m) . It was amazing
the Tornado would skip the crests, and soar over the troughs.
It was madness, with some poet license here, we zoomed/sliced over 5 crests in
five seconds, and then the wind would calm down to 2 or 3 crests in 5 seconds
with some bucking bronco added, and then accelerate/zip again.
I will never forget the thrill, not to mention wondering will
the wind ever slow up. I recall a Tornado to windward of us,
and counting it cartwheeling about it's mast 3 1/2 times, and
the crew later righted the boat, unassisted. (unsealed masts back then)
Anyway, I would call it somewhere between sailing/flying & oh ____.

Great wind & waves,
Chris Stater

Hello dear Sycho 15,

About the Tri-Foiler, a study was carried out in the MIT Water Tunnel ( with a depressurized free surface ) in 1994 by C.Savineau and J. Paschkewitz on a model of the hydrofoil used on the Ketterman's boat.

The section was far from optimum, as simple NACA 2410, and cavitates beyond 37 kt for low Clift. Like 20% chord bubble for 39 kt, 60% at 45 kt and 100% ( supercavitation ) at 55 kt.

Take a look at the remarkable web site of T. SPEER.

When you seek for ultimate design for subcavitating sections, you "hit the wall" like "sound barrier" around 52 to 54 kt without swept back wings, even with ultra-thinned sections...beyond it's supercavitation which reigns...

Friendly Yours,
FRENCHIE

Frenchie,

Does Bernoulli's principle, applied to foils, not depend on the difference in pressure between two surfaces? My understanding is that it's not simply a 'sucking' effect. I.E...the low pressure on the curved side of an airfoil is only a low pressure as defined by the higher (normal) pressure on the opposite, or typically flatter, side. In analyzing a hull going through the water, there is no opposite flat side with which to establish a greater or lesser pressure (not technically - but the air difference is so negligible). I think any hydrodynamic effect of the hull being drawn deeper into the water at higher speeds, however great it might be, is negligible in comparison to the moment applied by the sail plan to the leeward hull when the wind is honking.

For Reference: Phantastic Physics

And even then you just put a spinnaker on a pole out front and generate enough vertical lift to raise the bows out of the water!

Jake...I think your onto something. This whole sucking effect thing is counterintuitive for me. I know if I hit a golf ball into the water hazard (which I do regularly) if the ball is going fast enough it does not get sucked under, it skips off the surface. I know the golf ball example is a bit extreme but wouldn't the same principals apply...Dan