Catamaran beam vs trimaran beam

In terms of ORMA60 trimarans the beam and LOA are almost equal , when you look at catmaran's the same trend doesn't seem to be true.... for example the G class cats are as wide as long... why is this?

 

Stability is the key

I don't know about the G class cats but usually cats are not very wide compared to tris. There seem to be a few reasons for this.

Stability needs to be balanced sideways and fore and aft. If you go too wide then your sideways stability will be high but your fore and aft stability will be relatively low. If you put a rig on the boat that is designed for the sideways stability then when you bear away and fore and aft stability is required you are prone to nosediving and capsize.

Trimarans have more fore and aft stability as they have three bows and therefore more volume up front. They are therefore more stable fore and aft. Trimaran float bows can also be wave piercing so that the boat doesn't trip over the bows when they go under the water surface.

Another cause is probably something to do with wetted surface and weight. As tri floats are pretty small and light compared to a cat hull tris will have less wetted surface even before they fly a hull. Cats really need to start flying a hull to reduce wetted surface. Going too wide means the cat can't do this. Also the super stable cat will be hard to gauge when pressed hard - tris and normal cats have a more even stability curve.

John Shuttleworth designed a Formula 40 back in the 80s which was narrower than the rules allowed to get hull flying earlier. It was designed to be lighter and faster in normal conditions than other cats.

cheers

Phil Thompson

 

Cat beam/Tri beam

These specs are interesting:
--Banque Populaire V -LOA 131' Beam 75' foil assist
--Sodebo(tri)-LOA 104'-Beam 55'
--Groupama(tri)-LOA 103' Beam 73.8' foil assist
--OrangeII (cat) LOA 121' Beam 59'
--Hydroptere(trimaran foiler) LOA 59' Beam 80' --Parliers Cat LOA 60' Beam 49' foil assist
--WSL super cat LOA 70' Beam 39.4' foil assist
--ORMA TRI's LOA 60 Beam near 60 or 60 foil assist
---------------
Phil is 100% right and one of the design features that can help a tri(or cat) explore wider beam is the use of hydrofoils for both pitch control and reduced wetted surface. Groupama and Parliers Cat use foil assist and ,of course, Hydroptere is a full flying foiler with excelent pitch stability.
And all of the ORMA Tris use foil assist; foils can reduce the risk of pitchpole on very powered up multihulls. Their use in both foil assist and full flying incarnations is bound to spread as the technology is better understood. The newly announced WSL supercats will also use foil assist
and there have been successfull uses of rudder t-foils on beachcats to increase pitch stability.
I believe the utilization of foil assst on a tri design under 20' can produce a trimaran substantially faster than a beachcat because the foils will allow the boat to use its beam for power w/o fear of pitchpole.
-----
Just to add: one of the differences between cats and tris with very wide beam is that the tri is generally designed so that the amas never touch the water at the same time whereas, of course, the cat hulls do and tend to slow down tacking. But probably the biggest problem with wide beam on a very big cat is structural though the "Decision" type cat with a non-floating "hull"- like structure down the middle may reduce that problem. It appears from the sketches that the WSL supercats will utilize such a structure.

 

This is all rather amusing in its insistence that the suggested method for better boats is through the use of foils and foil assist. Some would tell you otherwise. The marketplace would also tell you otherwise. Take a look at the raging success of the Hobie Trifoiler and the Windrider Rave. Yes, I guess you'd have to say from those two examples that foiling solutions have emerged and are being championed throughout the sailing world due to their overwhelming success in the marketplace.

Some on this Forum would have you believe that Int. Moth foilers are flying out the door at a frantic pace in support of the hyped claims of a foiling revolution. Unfortunately, not one of these over-cooked claims has been backed-up with solid, verfiable numbers. Of course, the claimants could always step-up and produce said verifiable data and take the hype out of the equation. We're all waiting for that miraculous day.

Interestingly enough, I found this rather poignant and parallel quote regarding the applications of emerging technologies for everyday solutions in our lives.

Transportation in 2000 A.D. (1966)

This interview from the 1966 radio documentary by the name of "2000 A.D." asks William Ronan, chairman of the New York Metropolitan Transportation Authority, about our transportation needs for the future. An excerpt appears below:

"I think we're going to find new types of transportation. I think the vertical rise aircraft is just about to come into its own, so that we'll be able to have airports which will be close in to the central parts of our cities. And these vertical rise aircraft will take very little space. They'll be able to take-off and carry people and I think they're going to prove to be answer to what some thought the helicopter would be able to produce for us in the past."

Since we have the benefit of many years of retrospective observation to get a handle on this one, the irony is obvious. Techno solutions of the foiling type are not necessarily the answer to better boats. God knows we've somehow managed to get along without hundreds of vertical takeoff and landing aircraft buzzing a round us like insects. Don't ask me how we did that because techno proponents such as Doug Lord would have us all believe that foiling boats are an absolute inevitability. I believe the phrase often uttered is: "It's only a matter of time." In the case of the VTOL craft supplanting helicopters with landing pads on every corner... time is still waiting.

Yet, here we have a guy making pronouncements of an equally grand scale from 40 years ago. A guy who has a good deal of credibility in his field. An educated, connected guy from one of the largest cities on the planet and he's not only wrong about whizzy technology as the Messiah of our desperation... he's embarrassingly wrong.

Better boats have safety, simplicity, less windage, more efficient sail systems and less expensive manufacturing techniques associated with their design process. Whizzy techno products do not, in and of themselves, make for solutions with lasting value. It's just far too easy to create yet another, technology flavor of the month, that will soon replace what was so absolutely necessary last year, leaving the previous owners with nothing but vapor for promises and a dwindling value for their investment. Improved technology can be an enhancement for many products, but it is not a complete solution and never will be.

 

Beam / foils

--Banque Populaire-LOA 131' Beam 75' FOIL ASSIST
--Sodebo(tri)-LOA 104'-Beam 55'
--Groupama(tri)-LOA 103' Beam 73.8' FOIL ASSIST
--OrangeII (cat) LOA 121' Beam 59'
--Hydroptere(trimaran FOILER) LOA 59' Beam 80' --Parliers Cat LOA 60' Beam 49' FOIL ASSIST
--WSL super cat LOA 70' Beam 39.4' FOIL ASSIST
--ORMA TRI's LOA 60 Beam near 60 or 60 FOIL ASSIST
---------------
The relationship of foils to beam is that the foils make the beam more effective and allow more sail to be carried than would otherwise be possible. The widest boats for their length in the list above all use foils.
Foil assist is not really new technology- it is race proven technology that most of the fastest and largest trimarans use and have used for years and that is being adopted by the one-design WSL catamarans and at least one of the new "G" class tri's.
Foil assist has been tried on a limited basis on some small beachcats recently with good results but the class rules prevent it in the Tornado and A-class cats.There is a lot of room for experimenting with foil assist in smaller boats -particularly trimarans- based on the proven results already achieved.
There are new ways to use foil technology combined with planing hulls as has been experimented with on Parliers Cat. Whereas in the past three or four foils were considered a "multihull configuration" for full flying Kotaro Horiuchi is experimenting with bi-foil technology on a small tri.
Its the vision of many of the designers and sailors experimenting with new technology that has led to the successful,proven, application of foil assist on larger boats. There is no reason that this technology won't 'trickle down' to smaller- under 20'- multihulls as its already starting to do.
In the 20-30' range there are the examples of the Catri 27 and Exploder that are both
designed to utilize foils to lift to one degree or another.
So from the perspective of "foil assist" its not new technology but proven technology that has been around for years and is now begining to be applied to more boats than ever for one reason: it works.

 

Spinning away with the foily thing

Let's get back to Seadog's original question before this amusing thing about foils and the need for foil assist takes us too far astray, shall we.

Here's his original query..

The truth, Seadog, is that each and every boat has a design sweet spot within which, it is hoped, it will operate at max efficiency. Keep in mind virtually every one of the boats you mention, as well as those shown by Doug Lord, are racing machines which are meant operate at the very thin edge of what can work optimally and what will fail if pushed one degree too far from the design envelope.

The Catri tri is the exception here, but it continues to suffer from low built numbers, a lack of popularity among multihull enthusiasts and a distinct aversion by those seeking to build a new boat in the face of other boats in the general cost/benefit class.

Ultimately, consumers dictate the recreational products which are the most successful and not the guys who espouse techno solutions for better boats. Apparently, the consumer has already spoken when it comes to the Catri recreational boats and the use of trick lifting foils on same. It's kinda weird, actually, that Doug would knowingly include a rec boat of dubious value and extremely limited interest to make a point, simply because it has a set of foils. But then, that's our Doug. Foilmania Boy to the end. Even when it doesn't make any sense at all.

A lot of this design thinking for tris and cats with regards to beam/length ratios is in the minds of the head designers at the various hot shops who punch-out these designs. I haven't seen much in the way of their open mic conversations on the issue so I'm going to assume that virtually all comments here, no matter the point, are on the speculative side of things with as much value attached.

I don't operate at that end of the boat spectrum and smaller, scaled down boats that mimic the ratios of the big rigs have inherent problems as functioning craft, so it probably is not wise to place too much on the revealed performance potential of a smallish ORMA 60. The big, fast boats can provide an interesting jumping-off point for studying possibilities, but the issues associated can get complex rather quickly. Remember... The smaller the boat gets, the more impact created by one single crew member. On the really big, fast boats, this is not so much of an issue.


Good question, though and it gave me pause as it applies to the small multihulls I like to draw.

 

Catri 27 Foil Assisted Trimaran

Running down the Catri trimarans is an unfortunate course to take.
Read what some who have sailed them say:
Home of Aegean Catri 27 - Hydrofoil Assisted Trimarans, Aegean, Inc.
Address:http://www.aegeanmarine.com/ Changed:12:41 PM on Tuesday, March 20, 2007

 

You're kidding right, Doug? Using Aegean Marine's own hype to substantiate the brand and not a review from an outside party. Yes, that's more than interesting.

In case you misread the original set of statements I made about the Catri...

"The Catri tri... continues to suffer from low built numbers, a lack of popularity among multihull enthusiasts and a distinct aversion by those seeking to build a new boat in the face of other boats in the general cost/benefit class."

No running down, as you called it there, Doug. Just stating obvious and well-known facts.

and,

"Ultimately, consumers dictate the recreational products which are the most successful and not the guys who espouse techno solutions for better boats. Apparently, the consumer has already spoken when it comes to the Catri recreational boats and the use of trick lifting foils on same. It's kinda weird, actually, that Doug would knowingly include a rec boat of dubious value and extremely limited interest to make a point, simply because it has a set of foils."

Also nothing here that isn't also supported by the lack of popularity in the marketplace. Don't let your love for foiling things cloud your otherwise precise and rapier wit about varying boat model success.

Now, perhaps you can illuminate the sales figures for the Catri and compare them to those of the Corsair line of like sized trimarans, especially the newest Corsair the Sprint 750. I'll just hang around watching the thread and you can show us that the Catri is a really big success with hundreds of units sold and dozens more under build around the world in private shops.

Using the manufacturers web puff for substantiation is, ... well, it's less than impressive. What do you think the dudes are going to say about their own boat... that it's fiddly, complex and highly susceptible to weed collections that eliminate the foil support?

Perhaps you are smarter than the buying public, Doug. In that case, get your own fiddly boat on the water in the size range and prove the buying boaters of this planet wrong.

I'll just wait over here.

 

Beam + Foil Assist

The buying public? Well,with the addition of the largest racing(sailing) trimaran(LOA 131' Beam 75') ever built to the list it's clear that those that spend the most for their multihull magic prefer foil assist designs
overwhelmingly.

 

I'm still waiting for your data on the Catri sales vs the Corsair Sprint.

So, is it more conjecture and hot air or do you, in fact, have the sales figures to support your claims?

You brought-up the Catri and now ya got nuttin' but a Red Herring. Interesting play, Doug. Fundamentally weak, but interesting.

A fresh bowl of Captain Crunch and whole milk should fix you right up.

 

Beam + Foils

Actually, I made NO CLAIMS WHATSOEVER for the Catri 27 except that it uses foil assist.
I have ,however, pointed out that those that speak of multihull design with their wallets speak loudly in favor of "foil assist" as a major ingredient in their quest for the fastest,safest and most technically developed multihull.
Besides the Catri 27 and the Exploder beachcats like the Stealth 16 and F14's are using foil assist in the form of rudder t-foils.
Utilizing foil technology on smaller boats is a natural progression with huge potential benefits in improving small multihull performance.
Why,ITS JUST A MATTER OF TIME before many more small multi's-particularly beachcat killer tris adopt the technology.....

 

Doug and Chris thank you both for your replies I think you have both provided me with an answer.
Cheers Peter