In your proposition, when the mast is in one of the hulls the boat should be called a proa and when it is "parked" in the middle of the beam it is a cat again.

Proas don't have "transversal travelling" masts and in fact it is not likely that anyone will develop one soon.

But what you suggested makes sense - it is like Team Philips with taller masts, using one sail in each tack. Not very practical, but still a great design.

(You know who loves proas and can tell you all about it - Chiodi)

I know I don't trapeze off my wings all the time because theres not enough wind to do so.

Ahhh, the great debate, and the often heard excuse "is not "rule efficient".

Tell me Luiz (and forgive me for contininuing with me cynical tone) how does one seperate brute force solutions from creative solutions if no limits are set ?

I mean without any limits Club Med, Playstation, Kersausons Tri geronimo and a whole lot of other boats would simply blow away all of the ARC cats right ? Would that mean that the are superior in design to the ARC designs ?

No true creativity is found in limiting rule systems like A-class, and to some extend F18 class. Here there is no easy way of the brute force methode, just the path of refinement.

The flyer A-cat design was able to to make a mark in the A-cat class under the given conditions. Spinnaker shapes development jumped in the F18 class. Anyone with a model 95 spi will be blow away by new spi designs. In open classes they would just have grown bigger not more refined.

To look more closely at your bow example. If a straight bow is better for a given maximum length of hull than when will a non straight bow be better than a straight bow ? Think about it, if it is faster for a given length than what is holding it designers back from using it in their designs. If the max length is holding it back than by the same measure the maximum lenght is ALSO holding back the straight bow.

Same applies to sloop rigs, If the jib is such a aerodynamical bad thing than why haven't both the tornado class and F18 class evolved into uni-rigs with just the mainsail of maximum size ? I mean there are not rules prevent crews from sailing with less sails than allowed ?

The only answer is that the used setups are faster. Maybe not very much faster but faster nevertheless than their round bow and uni-rig alternatives. Now some will argue that when you place the jib area into the main that you'll have a better boat. But then I answer that when I fit a jib to this new setup I will even be faster then the one without a jib.

Don't you see that this is just a theme that can be repeated indefinately when there are nor rules ? However it doesn't really change the basic conditions underlying the performance. What is better under limits will be better when scaled up or down.

Think about it.

only resently the A-cat banned hydrofoils, but this happened without any design with foils proving to be faster. Some classes still do allow hydrofoils and we'll just have to see wether foiled designs are faster in these classes.

Wouter

Wow, it is so much fun listening to all you engineer guys argue. It makes me wonder -- if they put you all on one of those Survivor Islands, do you think you would all be able to agree on how to build a shelter?

Sorry, it must be the moon phase. I am feeling very contrary today, too.

Bill,

You talking about the CFR20 versus Tornado example that has been your favorite for some time now. What they did wrong is what most do wrong; the design looked at various ratios as being independent ratios that would all lead to higher speed. While doing so they overlooked the interaction between ratios and decreased rigting related power more than they decreased the drag. In the lower wind speeds righting is not limitind power and there the boat was fast.

The fact that a design screwed up here doesn't mean that only boats with increased in both area to weight and righting to area can go faster. It is one solution that works but not the only one.

I expect the M20 to go the same way when the design stays at 2.6 mtr width.

Wouter

Bill,

You may want to look at your numbers again.

I see you are use the third order power in your following statement

"An RC30 hull weighs 175 pounds rigged and painted; scale that down to 20ft and you get 52 pounds; scale it on down to 18ft and you get 38 pounds"

When you do this than your 18 ft boat will only have 20 % of the displacement of your RC30. Now when we take 75 kg's for the 18 footer (a-cat) then your RC-30 has a mimimum displacement of 375 kg's = 827 lbs.

After subtracting 2 fully fitted hulls of 175 lbs that leaves 477 lbs for just the beams, mast sails and trampoline. A bit much don't you think ?

You can't apply your 3 order shrinking formula here as the primatic ratio of your RC 30 hull is not the same as that of the imaginairy 18 footer. You example sounds good by has no meaning in the real world as cat design formula's aren't so easy.

Wouter

Seeker,

contact Tom Haberman at Aquarius Sails (.com) ...he e-mailed me a pre-production photo of a new Arc 17, complete with spin pole...it looks way cool; although I'm admittedly biased being a big Supercat fan.

Tom had the ARC17 in the Florida panhandle back in February for some testing. I saw it then. It is a nice looking boat. It will interesting to see it compete against the I17R.

Don

Wouter,
While on the subject of whats new in beachcat technology, I was suprised you made no mention of the Ventilo Zipo (http://www.ventilo.ch)or Mattia Dynacat and all those photos on your website. These have a totally diferent rocker profile to any other cat I have seen and have flat, assymetric hull bottoms. Have you any news as to how these are performing in races, or are they still too new to have any numbers on the scorecard?
They may be fast in certain conditions and crap in others - I don't know. How about putting the url to the photos up so we can get some comments from other people including Bill Roberts.

Simon Fisher

I have often thought that a sliding trap rack could be a cool thing on a cat. [img]http://www.intcanoe.org/cnew1.html[/img] [img]http://www.intcanoe.org/c3.html[/img] [img]http://www.intcanoe.org/a5.html[/img]
Hmmm, images aren't working. Try the attached files.

'nother image attached

3rd image

I was at Moss Landing the other day, near Monterey, CA. I saw what looked like a 16' production Proa. I was out of photo film, but who needs it with the internet! Attached is a picture of the Proa and here is a link to see it. California Coastline . com

I couldn't hang with engineering so I can't address the specifics Bill & Wouter and everyone else has layed out.

I know my SC17 is an excellent sailing boat and I love it. I have also seen the photos of the new ARC 17 and spoke with one of the "test pilots" from Pensacola....apparently it is awesome....I've made some mods to mirror the ARC (sq. top main & high aspect jib), now if I can just get it dialed in.....

Can someone give more details on the new ARC17? Links to pictures? I love my SC20 but I think it would like a younger sibling!

Eric F
SC20
H16

wow. Now I would watch that! (or would I be on it?)

The way I see it it will either be a little palace or a monster of a shack that leaks everywhere.

All though Bill and I don't really have a disagreement. I mean if he builds shelters like he build cats (Big, strong and fast) than he will not get any comments from me !

The discussion between Bill and myself is pretty much a debating discussion, all in good fun. I'm sure Bill and I would grap a beer afterwards if we were doing this face to face.

Not that serious really.

Wouter

Wouter

http://www.geocities.com/f16hpclass/F16HP_boat_show_ventilo_zipo.html

To answer your questions

>>I was suprised you made no mention of the Ventilo Zipo (http://www.ventilo.ch)or Mattia Dynacat and all those photos on your website.

That is because I partly forgot about then but also because if I had remembered then I would not have used these as they have still to proof themselfs.

Up till now I haven't seen any of these being listed in a the race result of any regatta. They are quite new indeed.


>> Have you any news as to how these are performing in races, or are they still too new to have any numbers on the scorecard?

I think so. I also found that people interested in them were in doubt about wether to go for them or not. That is people that contact me about them, they eventually went for a more conventional design.


>>How about putting the url to the photos up so we can get some comments from other people including Bill Roberts.

See beginning of the post.

Bill and others have been discussing planing designs many time before however.

Wouter

"Who knows of a 20ft beach cat built in Florida with prepreg materials, a superlight boat, unirig with spinnaker, everyone thought it was going to be a rocketship. It was very fast in light winds, 5 knots. When the winds got up to 10 to 12 knots, other 20ft boats pulled even with it. When the winds got up in the 15 to 20 knot range, the superboat fell behind. What is wrong with this design? What was the mistake, the error, the oversight in this boat's design?"

Right, I`ve followed the line of argument between Wouter & Bill, and I`m intrigued as to why neither of them have seen the obvious : Take both of their ideas / theories & build a boat that conforms to both sets of ideals : Wide is good, helps lighter crews hold down more power. Light is good, helps reduce drag. Combine the two & you have the best of both worlds. Perhaps that`s why everybody compares every other boat to the Tornado : It has all the hi-tech material advantages making it stiff & light, & is also wider than other boats in the same / similar class. Seems the Supercat range of boats are heavier, so need more sail area to compensate. Due to this they are more powerful, needing a wider platform to compensate for this.
Why not take the Supecat design philosophy, reduce weight using modern construction methods (the cost has reduced over the years), and you`d have a serious monster machine.
No need for new moulds & tooling.
If width is a problem for towing, design folding / telescopic beams that are easy to dismantle & reasemble.
If the R33 can do it, so can other designers / builders.

Any takers ?