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Minicat 420 - Tips, tricks, tuning?
by midraed. 10/06/20 09:56 AM
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Re: The I4C (LAC) C-Class Championship [Re: Timbo] #216347
07/22/10 01:50 PM
07/22/10 01:50 PM
Joined: Nov 2005
Posts: 1,203
uk
TEAMVMG Offline
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TEAMVMG  Offline
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uk
Because moths can alter their degree of heel to alter the angle of lift off of the T-foil. They can heel to windward to get windward lift.

A cat can only sit upright in the water once on t-foils. This is why we are mow seeing curved foils starting to make a showing.


Paul

teamvmg.weebly.com
-- Have You Seen This? --
Re: The I4C (LAC) C-Class Championship [Re: Timbo] #216349
07/22/10 03:17 PM
07/22/10 03:17 PM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
Carpal Tunnel
Jake  Offline
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Joined: Jun 2001
Posts: 12,310
South Carolina
Originally Posted by Timbo
That's interesting that even up on foils they were slower, but maybe the foils were too small and required too much angle of attack (and thus drag) to get it airborne? Of course if you go with longer foils you also incure more drag...it sure seems to work for the Moths, I wonder why not for the cats.


Weight is one big thing working against the catamaran....it does have twice the hulls...and if you think about it, if you're going to try and spend most of your time airborn, why have two hulls?

Next you have a LOT of power in the rig. The foils have to resist that power that tries to press the leeward hull into the water (and tries to lift the windward hull)..so the lifting force required by the foil increases dramatically because of the lever between the foil and the sail power (beam). As a result, having to lift more weight means the foil has to be larger (or at an extreme angle) and more inefficient. A moth foil doesn't have to deal with but a fraction of the leverage forces since it is mostly in column with the sail drive.



Jake Kohl
Re: The I4C (LAC) C-Class Championship [Re: Jake] #216368
07/22/10 07:53 PM
07/22/10 07:53 PM
Joined: Sep 2006
Posts: 613
New Hampshire, USA
windswept Offline OP
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windswept  Offline OP
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Posts: 613
New Hampshire, USA
Here's a quick video from Steve from their first sail on Aethon. Hopefully more to follow. I hope to get done next week to look at the boat up close. Will see what time allows.

http://www.youtube.com/watch?v=_Vln5YWsXC4


Tom Siders
A-Cat USA-79
Tornado US775
Re: The I4C (LAC) C-Class Championship [Re: windswept] #216374
07/23/10 02:50 AM
07/23/10 02:50 AM
Joined: Nov 2002
Posts: 612
Cape Town, South Africa
Steve_Kwiksilver Offline
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Cape Town, South Africa
Steve Killing (The designer for the Canadian team, I think) wrote a 16 page article which I found somewhere on the net (I`m really good at finding stuff, and really bad at remembering where.)
It was titled "THE 19th CHESAPEAKE SAILING YACHT SYMPOSIUM" - ANNAPOLIS, MARYLAND, MARCH 2009 - ALPHA AND ROCKER - Two design approaches that lead to the successful challenge for the 2007 International C-Class Championship.

It is a fantastic article, detailing almost all the aspects of the design of both boats (They are actually identical - one foiling, one not. They tested them both against eachother and chose the faster boat (non-foiling) to challenge Cogito.
It is amazing how much info he is prepared to share, quoting Naca specs for the foils & daggerboards, Lift/drag charts, Data tracks, construction details, GPS Polars, and more.
Some of his comments :
"Two boats were designed for this challenge - the first
was Alpha, a wingsail catamaran, which incorporated some
new thinking on sail configuration and hull shape. This
made it a successful evolutionary, but not revolutionary,
step from the current state-of-the-art boats. Compared to
Cogito, the main rival, she had a taller, narrower and
thinner wing, lighter construction and more circular hull
cross section. The second was Rocker, the bold hydrofoil
catamaran, using hulls from the same mold as Alpha and an
identical wingsail as the driving force. The daggerboard
hydrofoils automatically controlled the ride height with
trim tabs, while the control of the rudder elevators was left
to the helmsman. Although she flew well, was very
controllable, and was spectacular to watch, Rocker could
not match the 20 knot plus speed of Alpha." and :
"After this fairly careful experiment in foiling, we are
comfortable concluding that hydrofoils donít perform in
this configuration on a C-Class catamaran. There is no
doubt that fine-tuning our parameters could increase
Rockerís speed, but it will take more than fine tuning to
make the required leap in performance. We encourage
other teams to learn from our experiments and go forward
to find the solution that will push hydrofoiling catamarans
to the next level of performance."

I hope he doesn`t mind me quoting this here, but if you have a real interest in this I`d suggest trying to find a copy of the full article. I think it may have appeared on Sailing Anarchy or Boatdesign.net, but I seldom remember anything past last week Wednesday.

Re: The I4C (LAC) C-Class Championship [Re: Steve_Kwiksilver] #216386
07/23/10 10:53 AM
07/23/10 10:53 AM
Joined: Sep 2002
Posts: 3,222
Roanoke Island ,N.C.
Team_Cat_Fever Offline
Carpal Tunnel
Team_Cat_Fever  Offline
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Joined: Sep 2002
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Roanoke Island ,N.C.


"I said, now, I said ,pay attention boy!"

The cure for anything is salt water - sweat, tears, or the sea
Isak Dinesen
If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most.
E. B. White
Re: The I4C (LAC) C-Class Championship [Re: Steve_Kwiksilver] #216387
07/23/10 10:54 AM
07/23/10 10:54 AM
Joined: Jan 2005
Posts: 6,046
Sebring, Florida.
Timbo Offline
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Timbo  Offline
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Sebring, Florida.
Thanks for posting that Steve, very interesting.


Blade F16
#777
Re: The I4C (LAC) C-Class Championship [Re: Timbo] #217206
08/05/10 03:17 PM
08/05/10 03:17 PM
Joined: Sep 2006
Posts: 613
New Hampshire, USA
windswept Offline OP
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windswept  Offline OP
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Joined: Sep 2006
Posts: 613
New Hampshire, USA
An update from Fred with his new wing on the new plarform Caanan. Hopefully Steve will unveil his wing this week.
http://www.youtube.com/watch?v=JRYZjE6dpJI
http://www.youtube.com/watch?v=2u3nnP9W34Q
From Inviticus.
http://www.youtube.com/watch?v=zskN0rsdRfc
From Steve.
http://www.youtube.com/watch?v=_Vln5YWsXC4

Attached Files
Last edited by windswept; 08/05/10 03:28 PM.

Tom Siders
A-Cat USA-79
Tornado US775
Re: The I4C (LAC) C-Class Championship [Re: windswept] #217207
08/05/10 03:27 PM
08/05/10 03:27 PM
Joined: Sep 2006
Posts: 613
New Hampshire, USA
windswept Offline OP
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windswept  Offline OP
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Posts: 613
New Hampshire, USA
Steve's new platform Aethon with Cogito's wing.

Attached Files
Last edited by windswept; 08/05/10 03:28 PM.

Tom Siders
A-Cat USA-79
Tornado US775
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