The secret of Tornado

[Ivan Adamis]

Hi to ALL,
I am brand new here from Hungary.

I am having hard time to find any articles on the WEB answering my fundamental question, which is:
how come that such an old design (1966), even with all those nearly continuous development can still keep up with the brand new design power cats, whose design is based on new fundamentals, trends, CFD aided researches? As far as I know a state of the art Tornado can fly over 30 knots. (But at least 25+) None of these hi-tech speed machines (in this size range) can significantly exceed this, if at all.
This gives me the impression that 1.) the designer of the tornado must have been a genius, 2.) the researches have rached the section of a convergent function (in Y dierction), where to reach a bit of a progress costs lots of efforts.
How come, that recent significant changes in hull shapes brings so little relative to little older "fashions"?
This reminds me to tyre pattern design. Completely different patterns end up in quite similar performances. Which has the message, that this is either far from being the optimum, or this is not the point at all. (Of course there are well proven elements, but it still seems to be a whitchcraft than an exact science.)
In F1 design I have the same feeling. There is a constant urge and constraint just to change something and only relatively few of them establish something imperishable. I am a development engineer, and what I see in automotive industry is an obsessive change than real development. (Honour to the few revolutionary exceptions).
So. Why is the good old Tornado is still a one of the fastest multihull, in its range?
Thx a lot!

[Stumble]

Ivan,

In large part it is because there really isn't a demand for a higher performance cat. Once the boats get fast enough, most people just don't want to spend the money to go faster, and so as the price point for each increase in speed goes up exponentially, fewer and fewer people are willing to spend the money.

In addition the best competition all race Tornadoes so if you want to win competitive events it doesnt matter what you sail, as long as everyone is on the same boat.


It would be absolutely easy to design a faster production cat, but if it is three or four times the price, who would buy it? Or if it took significant support to own, say with a wing, where would people keep it.

[CatBuilder]

Stumble: When he's asking about the Tornado, isn't he really asking about the general Tornado hull form?

I mean, my designer designs fast catamarans using a modified Tornado. The Gunboats, though carbon, use the same basic hull form.

Isn't the OP asking why this hull form is the de facto high speed catamaran hull form when it would seem someone would have come up with something faster?

The only thing I can really think of that may be faster would be those new America's Cup AC 45's that flatten out at the stern. Maybe. No idea if it's true.

However, it seems nobody has come up with a faster, more easily driven design. Maybe we have reached the limit? I think that's what the OP was asking about.

[Ivan Adamis]

Thanks Stumbel and CatBuilder for the quick answer.
Stumbel, you are more-ore less touching my guess: "to reach a bit of a progress costs lots of efforts" (and money, of course.) However, the question is still hanging there. I know that the rig and the sail have changed, but the hull - not really. So, why have we spent this enormous amount of work just to reshape the hulls reaching basically nothing in speed? To have a cool, modern look? If not the speed, there must yet be some benefits we have gained by all these continuous changes?
At one point I must disagree with you. I am chasing the speed. So, to me, it DOES matter whether I am racing in a slow one design yolle or in a one design cat. And you are not going to convince me that for you it makes no difference!
I am not sure, though, that under these size and handling constraint it would be that easy to build a significantly faster cat. (Look at the wing sailed C class. They are absolutely extreme design, but in heavy wind conditions the break apart. So, their top speed is around 25 knots. Which is double the true wind speed, I know.)

CatBuilder, you have gotten my point. The hull. Look at the Tornado's one and take a look at a modern 20ft cat's one. Two different world. And yet, their performances are very much alike. What do I miss here? What do WE miss here?
BTW, I am planning on building a hydrofoil cat (or tri?), but it is not knocking on my door yet! I may wanna use my Dart18 for the first trials, to see, if I am capable of doing the basic calculations to make it fly at all. (Originally, a I graduated as an aeronautical engineer, so I still know some basics) I would first mount the foils on the (extented) beams outside of the hulls, not wanting to destroy them first. As a prototype A.

I hope to talk to you both again.

Ivan

[Stumble]

Ivan,

I see what you are getting at. I think part of the issue is that cats in this size range when flying a hull have such a high length to width ratio that shape isn't that big of a concern since the boats even at high speed can operate in displacement mode. I am not a designer, so I can't say for sure, but with a length of 20' and a width of say 9" they have the ratio is like 30:1, which is just ridiculous. So only until the boats are traveling at ridiculous speeds does shape matter very much (so long as drag is minimized).

This is just conjecture, so maybe Richard will get on here and make some comments.

What I was trying to get at about the relative speed is that no one is pushing the small cat class to increase performance. The money just isn't there. Let's say to rebuild the Tornado out of Carbon Fiber would increase the price of the boat by 5 times. And would increase average speed of the boat by 1%. For me at least that would be a hard amount of money to justify for that moderate speed increase (these numbers are name up by the way).

To me this has been the problem in beach cat development. The next round of advances comes at a price that there isn't a market for. Which is the same reason there aren't very many 20' keel boats made out of carbon. The incremental speed increase just isn't worth it.

On monohulls however thirty years ago a boat that could plane was unheard of, or at least extraordinarily rare. In large part this was due to the lead being drug around that hampered the boats ability to get on top of the water. Modern bulb keels however changed this dynamic, and so we have seen a radical increase in monohull top speeds as a result. No one yet has come up with a corollary or an inexpensive technology that immediately increases speed potential in small cats. Though foils and curved boards seem to be headed in that direction.

What I see is historically boat speed is pretty flat, then some new technology comes along and drives it up quickly over just a few years 10-20) then there are modest increases in refinement until the next revolution. In monohulls there just have been some relatively major changes that occurred all at once (bulbs, canting keels). Where for cats, other than square top mains I can't really think of one.

What I am curious about is if small cats will be able to maintain a speed advantage over cats as foil technology advances, and wings get wider and wider. Modern Moths for instance While not quite up to the speed of a Tornado, are faster than the last generation of Tornados. And the Moths are continually getting faster, while the Tornados have pretty much maxed out.

[Steve W]

Ive always marveled at the same thing, but when you think of it the Tornado has pretty much semicircular hulls so, about as low resistance as can be had, plenty af sail area and light weight, oh,and 10ft beam so more righting moment than an 8ft beam cat so more ability to use that sail area whether you are on the traps or not. Thats pretty much the formula for cats, you can manipulate things around the edges which such as lighter weight (at great cost) bigger sail area, plumb bows which will give you a longer waterline, different rocker, more or less beam, but just about everything you do outside the basic formula will likely just improve the boat for one set of circumstances at the expense of another. Tornados, while the hull shapes have remained constant for 45yrs have had the benefit of the areas where design has improved such as sail design and construction and the same for hardware so i imagine a 2011 version would be quite a bit faster than a 1966 version.
Steve.

[Doug Lord]

Originally Posted by Ivan Adamis

Thanks Stumbel and CatBuilder for the quick answer.
Stumbel, you are more-ore less touching my guess: "to reach a bit of a progress costs lots of efforts" (and money, of course.) However, the question is still hanging there. I know that the rig and the sail have changed, but the hull - not really. So, why have we spent this enormous amount of work just to reshape the hulls reaching basically nothing in speed? To have a cool, modern look? If not the speed, there must yet be some benefits we have gained by all these continuous changes?
At one point I must disagree with you. I am chasing the speed. So, to me, it DOES matter whether I am racing in a slow one design yolle or in a one design cat. And you are not going to convince me that for you it makes no difference!
I am not sure, though, that under these size and handling constraint it would be that easy to build a significantly faster cat. (Look at the wing sailed C class. They are absolutely extreme design, but in heavy wind conditions the break apart. So, their top speed is around 25 knots. Which is double the true wind speed, I know.)

CatBuilder, you have gotten my point. The hull. Look at the Tornado's one and take a look at a modern 20ft cat's one. Two different world. And yet, their performances are very much alike. What do I miss here? What do WE miss here?
BTW, I am planning on building a hydrofoil cat (or tri?), but it is not knocking on my door yet! I may wanna use my Dart18 for the first trials, to see, if I am capable of doing the basic calculations to make it fly at all. (Originally, a I graduated as an aeronautical engineer, so I still know some basics) I would first mount the foils on the (extented) beams outside of the hulls, not wanting to destroy them first. As a prototype A.

I hope to talk to you both again.

Ivan

=======================
I think that back in the good old days of catamaran development Rodney March came up with a formula: 20/1 length/beam ratio, semicircular hulls that
is just scientifically correct and almost impossible to improve on -in terms of cat hulls. Sailboat design technology has improved by leaps and bounds with the little 11' Moth beating all beachcats and at least equal to the Tornado speed wise topping out over 30 knots these days-on hydrofoils.
I think speed improvements on multies are happening but not so much in hull design-foil design seems to be where some improvement is being made in the A and C Class cats, the NACRA 20 and others using curved lifting daggerboards and secondarily, rig design.
It seems to me that it is almost as exciting a time for design for speed as it must have been back in the "old days"!
Ivan, I'd like to hear what you have in mind with this
, why don't you start a thread in the "multihulls" forum describing what you're thinking about?
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Pictures: NACRA 20 foils, A Class DNA foils--
click on image--

[MalSmith]

An important difference between the Tornado and similar sized modern cats is that the tornado has an overall beam of 10 feet. Almost all comparable modern cats have a beam that is limited to 8 feet, for practical reasons. The problem with a 10 foot beam is that the tornado has to be towed on a special trailer with one hull up in the air, to meet the road trailer width regulations in most countries. What the 10 foot beam gives the Tornado, however, is more righting moment and hence a higher top speed. Added to this is 45 years of rig development which have kept the class current. The original rig did not have a spinnaker or square top mainsail.

[gonzo]

All the crude development and big advances in design are already attained in a boat like that. Improvements are now minimal at a great cost. It happens with every technology. For example, NACA foils, developed in the 30's are almost perfect. Improvements are also minimal and with little overall gain.

[Doug Lord]

To learn more about the state of the art in modern small cat design this article is helpful: http://catsailingnews.blogspot.com/2...n-fischer.html

[Gary Baigent]

The period when Rodney March designed the Tornado was a hot bed development time when Rod MacAlpine Downie was also designing his champion C Class cats with their, for the times, very advanced wing sailed rigs and they too, had a wide beamed platform at 25 x 14 feet; also there were the Manta designs, plus March's C Class Thunder, also the Cunninghams' were pushing new boundaries with their canoe bodied Quests while in the US, very advanced designs came from Steve Dashew with his Beowulfs all of them very similar hull designs to Tornado. That bunch was a brilliant bunch, decades ahead of their time and there's your answer, end of story.

[Ivan Adamis]

Thank you ALL, guys, I hve not even thought that such a powerful and interesting discussion will be generated from my post. However, since it's late and my only typing device is an iphone at this very moment, I get back to after I will have gotten at least a notebook.
I am looking forward to going on with you!
Ivan

[gggGuest]

The A Class and the C Class hulls have both changed shape and got a good bit faster than they were in the 60s s though: maybe its simply that there isn't that much development in the medium size range. I wonder too if the catamaran design space is a relatively simple one without quite as much scope for trading off design factors: in a monohull finghy for instance there are pros and cons to a shorter and wider hull - aspect ratio of planing surface, shape/behaviour wheen heeled, all sorts of things which don't seem to apply so much to a catamaran hull. Butt that might just be me shoqing my ignorance of catamaran design.

[BobBill]

I just spent some time looking for old article I saved about how Rod McAlpine-Downey's designs (Shark) set the standard for the Tornado and similar hulls.

Alas, I cannot locate it.


His Shark was wood, but it folded...and it virtually tried to fly on the water...

Old ideas can still do the job.