boat design - art or science?

[albentley]

which one do you think boat design is and why?

i would say that apart from a few cases boat design is an art in the same the way running a business is an art.

al

[FAST FRED]

I vote for ART , as a good designer needs to be able to "see" in 3D, and visualize what the boat does to the water.

The boats that were cranked out of a computer LOOK like the were .

The computer is GREAT for doing the grunt work , after an ARTIST does the real Art.

FF

[Vega]

It depends of the definition of Art. Etymologically Art means a very well done thing. Original meaning is still retained in the expression "state of the art".

Architects are the last descendents of the Humanists, in the sense that in that time, an Artist was also a Scientist and an engineer (Leonardo da Vinci, Durer). Architects are to my knowledge the only ones that still have in their curriculum (while at University) math’s, physics, humanistics, drawing, arts and technologic disciplines. I believe that is not by chance that designers of boats are Naval Architects.

[kach22i]

I'm the land lover type architect, but if Naval Architects face the same thing I do as a "Design Professional" then the "practice" is a business first. The goal of a business is to make money, which in a negative way means charging the most you can get while providing the least amount of service for that money so you can go on to the next project and the next fee.

Keeping the business side of things out of the discussion will be difficult as we all live in the real world.

I like what Vega has had to say, wish I was not so bitter at the moment..........darn deadlines.

[alan white]

I've never found a really great functional design that wasn't beautiful. I do find many if not most modern production fiberglass power boats ugly, but then if they were photographed upside down, my feelings might change.
All of the nonsense shapes above are now out of sight. The beauty has ended at the waterline. That's all.
The artist might aspire to make the rest of the boat as functional as the bottom shape.
In functional art, as in music, geometric laws apply. Discord is not a personal preference, but a real structural disintegrity and so "taste" has more to do with a person's recognition of geometric integrity than any bias.
It seems much of modern boat design brashly attempts to deny the very consciousness of whole meaning (which is expressed in undeniable geometric integrity), ending up with an expression of modern man's erroneous assumption that science is opposite art.
The two are the same. Even my dog can tell good music from bad, and I'd guess she finds certain boat designs more pleasing than others for the same reasons.
Just my two cents.

Alan

[albentley]

what about the idea that many years ago it was an art- but as the physics behind all the hydrodynamics etc has become better understood its turned into more of science. also similar to buildings there are ever increasing regulations which can limit the possibilities of a design. eg lloyds ABS etc

i have studied both architecture and naval architecture and definitly from a university curriculum point of view they are completely different. naval architecture is essentially engineering whereas architects spend the first year practically doing an art course!

i'm not sure if any of you have seen the ghost ship which is labeled as a public art project, i feel this is obviously an exception to a normal ship but still interesting!
http://www.ghostship.org.uk

Al

[Leo Lazauskas]

I think that ship hydrodynamics and memetic algorithms are far more beautiful than actual ships.

[SailDesign]

I'll go for an "Artistic Science"
And FastFred - I'll be talking to you later...

[RatliffFranklin]

which one do you think boat design is and why?

i would say that apart from a few cases boat design is an art in the same the way running a business is an art.

al

Your question assumes it's an either/or situation.

A better question would be "Is boat design a scientific art or an artistic science?"

[RatliffFranklin]

what about the idea that many years ago it was an art- but as the physics behind all the hydrodynamics etc has become better understood its turned into more of science. also similar to buildings there are ever increasing regulations which can limit the possibilities of a design. eg lloyds ABS etc

i have studied both architecture and naval architecture and definitly from a university curriculum point of view they are completely different. naval architecture is essentially engineering whereas architects spend the first year practically doing an art course!

i'm not sure if any of you have seen the ghost ship which is labeled as a public art project, i feel this is obviously an exception to a normal ship but still interesting!
http://www.ghostship.org.uk


Al


I once saw a documentary where it was suggested engineers and scientists rather than art historians should be the ones examining the approximately 30,000 pages of surviving Da Vinci notes and drawings.

Just because something looks like art doesn't mean it's not science.

On the other hand, simply because something is science doesn't mean it can't have a sense of style.

[Tim B]

Da Vinci was a polymath, but predominantly an engineer. Give an artist Da Vinci's work on aeroplanes and they'll not make head nor tail of it. Show the same to an engineer and he will stand in awe. The same goes for Da Vinci's explanation of valves in the heart and many other examples.

Getting back to the original subject, Boat design is a science, but it's a misconception that in a science there is only one right answer.

As an aside: The word "science" comes from the Latin infinitive "scire", meaning to know. And more directly, "sciens", the present active participle of the verb [scire], the direct translation being "currently knowing". Interestingly, the direct translation of "Science" (as we understand the word) raises both "scientia" and "ars". Re-translation of "scientia" returns "knowledge, science, skill" and re-translation of "ars" returns "strategem, skill method, science, technique, art, conduct, character, craft". It is thus fair to conclude that, just from the language, the romans described "art" as a general ability, and "science" as a particular knowledge or skill.

Interesting stuff, linguistics,

Tim B.

[RatliffFranklin]

Da Vinci was a polymath, but predominantly an engineer. Give an artist Da Vinci's work on aeroplanes and they'll not make head nor tail of it. Show the same to an engineer and he will stand in awe. The same goes for Da Vinci's explanation of valves in the heart and many other examples.

Getting back to the original subject, Boat design is a science, but it's a misconception that in a science there is only one right answer.

As an aside: The word "science" comes from the Latin infinitive "scire", meaning to know. And more directly, "sciens", the present active participle of the verb [scire], the direct translation being "currently knowing". Interestingly, the direct translation of "Science" (as we understand the word) raises both "scientia" and "ars". Re-translation of "scientia" returns "knowledge, science, skill" and re-translation of "ars" returns "strategem, skill method, science, technique, art, conduct, character, craft". It is thus fair to conclude that, just from the language, the romans described "art" as a general ability, and "science" as a particular knowledge or skill.

Interesting stuff, linguistics,

Tim B.

Neat.

Thanks.

[bhnautika]

For me its always been both, science is the frame or skeleton that the art puts flesh on. I find design is about problem solving in an artistic way and that the two must move together and not get to far apart.

[tri - star]

If the N. A. Herreshoff museum in the US East coast is still open, you will
find an answer. There I found one for myself.
As it's easy to understand why his boats won so many races - when you see
them close up. Every line and shape having a purpose - and flowing in
harmony with each other.
Went I was there at America Cup time - it was like visiting the Sistine Chapel !
Herreshoff truly intregated eng. and art.

The rest of the story is also instructive:
His brother was a very effective businessman.
I don't think the firm kept their clients very long after the brother passed on.
Which indicates, that there is a gulf between art/science and business, that
is hard for one man to bridge.

Cheers !

[Raggi_Thor]

It's an interesting topic, design of real objects has to be both art and science or engineering. During the last 50 years architects (in Norway, on land, buildings) have lost a lot of control/power/influence because they have chosen to let engineers do the less artistic work like heat & ventilation, dimensioning, project management etc. Now I think some of them (the architects) regret, because they have lost the freedom to create ¨what they want. SO, to be an artist in yacht design, you need to know your engineering, or you will become a stylist or interior decorator.

[Leo Lazauskas]

Da Vinci was a polymath, but predominantly an engineer. Give an artist Da Vinci's work on aeroplanes and they'll not make head nor tail of it. Show the same to an engineer and he will stand in awe. The same goes for Da Vinci's explanation of valves in the heart and many other examples.

Getting back to the original subject, Boat design is a science, but it's a misconception that in a science there is only one right answer.

As an aside: The word "science" comes from the Latin infinitive "scire", meaning to know. And more directly, "sciens", the present active participle of the verb [scire], the direct translation being "currently knowing". Interestingly, the direct translation of "Science" (as we understand the word) raises both "scientia" and "ars". Re-translation of "scientia" returns "knowledge, science, skill" and re-translation of "ars" returns "strategem, skill method, science, technique, art, conduct, character, craft". It is thus fair to conclude that, just from the language, the romans described "art" as a general ability, and "science" as a particular knowledge or skill.

Interesting stuff, linguistics,

Tim B.

Linguistics certainly is fascinating, but your conclusion is not really valid. In practice, most people do not know, nor care, about the etymology and history of the meaning of a word when they use it. When someone uses the word "science" today it makes no difference what the Romans thought the term implied 2000 years ago.

Leo.

[Tim B]

I agree, few people care about the original impressions or usages, but how much has it actually changed?

Unless I'm much mistaken, sciences are still considered to be a deeper understanding of (an aspect of) a problem.

Besides, now you can be informed about the language you use. It may not be of much use, but then again....

Tim B.

[PAR]

Some of the finest yachts ever conceived, weren't bellied around with a virtual panning tool. In fact these craft were understood to be beautiful, just by their plan, profile and section drawings, to those that penned them or understood the lines. Many fast, weatherly and able vessels, perform incredibly and are butt ugly, even if quite functional.

An engineer is structurally educated and experienced, a businessman has successfully kept themselves fed and an artist is the one who sees a yacht's wake and instantly understands how the boat will perform and why, because they've developed what few have had enough experience to, an eye. Not for the beauty of the thing, but that good form will provide good function, particularly if the businessman and engineer in them permits sufficient latitude to provide some grace to the form.

[Leo Lazauskas]

An engineer is structurally educated and experienced, a businessman has successfully kept themselves fed and an artist is the one who sees a yacht's wake and instantly understands how the boat will perform and why, because they've developed what few have had enough experience to, an eye.

So why did artists miss the existence of boundary layers for hundreds of years? Can artists see the vortices behind bird wings? :)

[PAR]

Da Vinci did see vortices in both bird wings (through smoke I'd guess) and with his extensive experiments with water. He clearly noted both in severial drawings.

[Leo Lazauskas]

Da Vinci did see vortices in both bird wings (through smoke I'd guess) and with his extensive experiments with water. He clearly noted both in severial drawings.

I've seen a couple of very early drawings with vortices behind people's legs when they were standing in water. But noticing is only part of the story. The key is to relate those vortices to drag losses, or in the case of sharp-edged wings, the additional lift that might result if leading-edge vortices reattach on the top surface. Artist schmartist, I say. They are, at best, only good for choosing the colour scheme of a boat

[RANCHI OTTO]

Boat design is for me a compromise between art and engineering.
Very often the rule is to put in the yacht a lot of beds and only then design all around the hull....

The boat is beautiful but....only to take a drink at port.

[BMcF]

An interesting argument, long debated. I've come to the conclusion that 'art', at the least in terms of what is 'pleasing to the eye', cannot be entirely ignored at the expense of 'form follows function'. To wit, one of my favorite examples follows and both vessels 'hit the water' at approximately the same time, so the comparison is valid in the sense that one would have to assume that all facets of both art and pure science/technology, that are (or are not) evidenced in each, coexisted.

The 'worlds fastest megayacht'...as once claimed anyway..
http://www.braa.no/spesielt%20interesserte/bilete/tumbs/moonraker%202.jpg


The worlds most efficient high-speed vessel in it's size range:

http://www.seariderinc.com/SES%20Photos/Sites-Images/17.jpg

The first relies in a hull design akin to a Hickman sled with a point stuck on it and thus has motions that will cause injury when operating at 50 knots in a 2 foot chop (not kidding..been there). At 116' LOA and roughly 100 tons, it made a little over 60 knots using two 16V396 MTU diesels and one TF40 gas trubine, all through KaMeWa jsts.

The second, an SES of 160' LOA and 220 tons, achieved 47 knots with only the two MTU 39616Vs and two 6V396 lift engines and would have achieved over 60 knots with same power as installed in the 100-ton yacht. Of more importance in my mind than the fact that we're talking twice the displacement as the yacht, the SES motions were acceptable, even under fairly high sea conditions in which the yacht would barely manage to slog through.

Post-script: The turbine has long ago been removed from that yacht and it now makes 35 knots with the twin 16V396 diesels.

The moral of the story?...the yacht 'looks' like a killer performance machine..the SES looks..well..just plain ugly. So in the years since both were on the scene, many Moonraker look-a-likes have been built and more will be; many with the same horrible hull designs..but very few vessels based on the SES and certainly none that were 'yachts' The superior performance of the vessel based only on 'best engineering and science' principles is not what people want to look at, own or operate apparently.

We've always lamented that we fail to find ways to do both well. If we could do so...the 'worlds fastest megayacht' would be once heck of a lot faster than they are now.

[kach22i]

Maybe the SES just needs the touch of a good Industrial Designer (or Architect) to make it more visually pleasing.

Link on that topic:
http://www.boatdesign.net/forums/showthread.php?t=16012

[PI Design]

Yeah, change the colour. Grey is so drab...

Ship design is definitely science, not art. Boat design? At the AC end, still science, at the dinghy end, I'd say science - with a lot of intuition rather than hard facts, and a bit of artistic styling sometimes thrown in.

[Leo Lazauskas]

Maybe the SES just needs the touch of a good Industrial Designer (or Architect) to make it more visually pleasing.


First step is to get rid of the humans on board. Most of that visual clutter above the waterline is to cater for fragile bags of water who need to see where the ship is going. High speed-vessels like that should be operated by robots. Think of the weight-savings for a start. And for SES, the cobblestone effect can't turn their kidneys into mush.

Then again, I'm not sure if I'd trust either humans or robots to operate a 20,000 ton SES travelling at 60 knots or more.

Leo.

[BMcF]

First step is to get rid of the humans on board. Most of that visual clutter above the waterline is to cater for fragile bags of water who need to see where the ship is going. High speed-vessels like that should be operated by robots. Think of the weight-savings for a start. And for SES, the cobblestone effect can't turn their kidneys into mush.

Then again, I'm not sure if I'd trust either humans or robots to operate a 20,000 ton SES travelling at 60 knots or more.

Leo.

LMAO. Great points. (Killer program you created in Michlet btw..kudos. It's recently served us well in a couple of problematic design tasks. Waiting breathlessly for R 2.0)

And what 'cobblestone effect'? I killed that little problem years ago.;)

-Bill

[kach22i]

And what 'cobblestone effect'? I killed that little problem years ago.;)

-Bill

All you have to do is take most of the mass out (weight) and lower the cushion pressure to almost zero - problem solved!:cool:

:D :D

[BMcF]

All you have to do is take most of the mass out (weight) and lower the cushion pressure to almost zero - problem solved!:cool:

:D :D

No no no. Tsk. You need only to supply massless air. Fortunately for my pocket book, the workable solution actually involves lots of fancy hydraulically-operated hihg-response cushion vent louvers (and/or variable-geometry lift fans) and a detailed knowledge of the spatial pressure responses, particularly those that are acoustic, and the ability to build a controller that can effectively resolve the whole mess through various filters originated by Kalman and others and kill the fundamental heave-bounce mode of the rather lively spring that is known, oxymoronically, as an air 'cushion'. (whew! that was a long sentence..) A 'cushion' it ain't...

[Leo Lazauskas]

And what 'cobblestone effect'? I killed that little problem years ago.;)
-Bill

Excellent news! That means you probably have lots of time to consider other difficult problems.

What do you think of the idea of an SES with a number of (typically three) sub-cushions, each at a different pressure?

Do you think that it is possible to have significantly different pressures? Or will leakage under the sub-cushions mean that the pressure will tend to be fairly even at the water surface?

Best of weekends to you all!
Leo.

[Leo Lazauskas]

LMAO. Great points. (Killer program you created in Michlet btw..kudos. It's recently served us well in a couple of problematic design tasks. Waiting breathlessly for R 2.0)
-Bill

If the objective is to deliver one million tons of material to anywhere in the world in 30 days, then carting extra weight around at high speed makes an extremely difficult task almost impossible.

Glad to hear that Michlet was of some practical use.
"...send gold, willingly, as much as you please."
Letter from Kadashman Enlil I, king of Babylon, to Amenhotep III...

[BMcF]

If the objective is to deliver one million tons of material to anywhere in the world in 30 days, then carting extra weight around at high speed makes an extremely difficult task almost impossible.

Glad to hear that Michlet was of some practical use.
"...send gold, willingly, as much as you please."
Letter from Kadashman Enlil I, king of Babylon, to Amenhotep III...

ALMOST impossible. Remember to keep using that modifier ...or ONR will cut our funding.;)

"Gladly pay you Tuesday for a [program] today". with apologies to Wimpy

[BMcF]

Excellent news! That means you probably have lots of time to consider other difficult problems.

What do you think of the idea of an SES with a number of (typically three) sub-cushions, each at a different pressure?

Do you think that it is possible to have significantly different pressures? Or will leakage under the sub-cushions mean that the pressure will tend to be fairly even at the water surface?

Best of weekends to you all!
Leo.

The concept that you describe has been found mathematically to offer *huge* potential drag benefits for very high L/B cushions. A certain LCS design was predicated on that feature. However, having personally been involved in divided-cushion tank tests...I can tell you that achieving effective cushion division is 'somewhat problematic', to use one of my favorite mealy phrases designedtoavoidscaringoffgovernmentfundingofcrackpotideas.

Why you ask?

[kach22i]

If a SES or Hovercraft's air cushion acts as an "air-spring", then having stacked springs of various frequencies is practical. The interactions of these springs to the surface and to each other is not something I'd be taking shots in the dark at. More science, less art.

I know people are working on this topic and have been.

[BMcF]

If a SES or Hovercraft's air cushion acts as an "air-spring", then having stacked springs of various frequencies is practical.

How you do dat?

[kach22i]

How you do dat?

You control the pressure by controling the rate of flow either through dampers or baffle valves (activators/louvers). Also I suppose if one could adjust the cross section geometry "at will" this would have an effect (reel in/expand out like a sail?).

I am not working on such a system, nor have I seen these "active" or reactive systems in use or tested. I'd say my guess is as good as yours BMcF, but I know it's not.:D

[BMcF]

I don't see how that is the same as having 'stacked' springs, which implies springs in 'series'; compliance thereof and the resonant responses easily calculated (and still dominated by the spring with the lowest 'K').

Cushion damping systems, or ride control systems (RCS), in use today do use active vent arrays commanded by 1s and 0s to add to the damping (modifying the 'b', not the 'K' in the simple resonance model) of the otherwise lightly damped and lively air cushion. The problem with doing that (for 'large' air cushion vehicles) is that the fundamental 'heave bounce' mode (related to compressiblity of the air) is not far removed from Helmholtz (acoustic) resonances in the cushion. The former is essentially spatially uniform throughout the cushion, the latter quite the opposite. Early attempts to control heave bounce (or cobblestone effect) were stymied by the fact that they often amplified - sometimes radically so - the acoustic responses. In the controls world, this called 'spillover'.

A rather savy Swedish SES captain once told me that he believed that "RCS" must be an acronym for "Rediculous Craft Shaker"...but that was before we got called in to replace a well-intentioned but poorly-executed prototype system with one that actually worked well.

Today's active cushion damping systems have reached the point where they are not only killng the fundamental heave bounce..they even kill the first and sometimes second modes of the acoustic activity. But the 'spring constant' remains unchanged....it's all about adding damping.

[kach22i]

add to the damping (modifying the 'b', not the 'K'

I'm going to work on my hovercraft now, it's just warm enough to scrape off the snow.

I'll be thinking about the "b" or as seen in the drawing below the "C" factor.

http://www.signalysis.com/press/sensors0899_1.shtml
http://www.signalysis.com/press/sensors0899_fig1.gif

[Leo Lazauskas]

If a SES or Hovercraft's air cushion acts as an "air-spring", then having stacked springs of various frequencies is practical. The interactions of these springs to the surface and to each other is not something I'd be taking shots in the dark at. More science, less art.


I've had a crack at the problem from a non-artistic point of view,
but I was wondering whether the results are realisable.

"Free-surface pressure distributions with minimum wave resistance"
E.O. Tuck and L. Lazauskas, ANZIAM Journal, Vol. 43, 2001.
http://www.cyberiad.net/library/pdf/tl01.pdf

Potters, sculptors, daubers: any opinions?

[BMcF]

I've had a crack at the problem from a non-artistic point of view,
but I was wondering whether the results are realisable.

"Free-surface pressure distributions with minimum wave resistance"
E.O. Tuck and L. Lazauskas, ANZIAM Journal, Vol. 43, 2001.
http://www.cyberiad.net/library/pdf/tl01.pdf

Potters, sculptors, daubers: any opinions?

I couldn't understand it..half of it is in Greek.:p

As I alluded to earlier, your work and Larry's were used (somewhat liberally extrapolated) a few years back to predict that the use of different pressure 'patches' along the length of the cushion in a very high L/B 'fast ocean transport' SES concept could produce huge reductions in resistance relative to a 'single cushion' under the same concept. The 'how to do dat' part is still untouched. I'm working now with an SES design of 11:1 L/B (!) ...same issues are extant.

[BMcF]

I'm going to work on my hovercraft now, it's just warm enough to scrape off the snow.

I'll be thinking about the "b" or as seen in the drawing below the "C" factor.

http://www.signalysis.com/press/sensors0899_1.shtml
http://www.signalysis.com/press/sensors0899_fig1.gif

I'm old..it was always 'b' when I was a young lad attentively copying from the professor's chalk board. Somebody must have decided along the way that the damping term was due to be incremented one letter.:D

http://www.calpoly.edu/~fowen/me422/eqmotmbk.html

[Leo Lazauskas]

I couldn't understand it..half of it is in Greek.:p

As I alluded to earlier, your work and Larry's were used (somewhat liberally extrapolated) a few years back to predict that the use of different pressure 'patches' along the length of the cushion in a very high L/B 'fast ocean transport' SES concept could produce huge reductions in resistance relative to a 'single cushion' under the same concept. The 'how to do dat' part is still untouched. I'm working now with an SES design of 11:1 L/B (!) ...same issues are extant.

Thanks BMcF.

A L/B=11.0 SES is certainly an unusual beast.

Just for fun, here's a plot of my calculations of the (Newman-Poole) wave resistance coefficient, C_NP, as a function of Froude number, F, for a "pure" hovercraft with the same L/B.

C_NP = rho*g*R/(B*p^2)
where
rho = water density
g = gravity
R = wave resistance
B = beam
p = mean cushion pressure.

Note that I've set the origin of the graph at C_NP=0.95
to emphasise the humps and hollows in the curve.

Regards,
Leo.

[tri - star]

To messers:
RANCI OTTO, BMcf, Kach22i and Leo Lazauskas.

Tending to work from the intuitive and then go to the computer and the math
- I'm a little nervous bantering with you guys.
However, Leo invited any potters or sculpters....to jump in.
So here goes:
Having produced a few vessels that operate effectively in " ground " or
surface effect, I can bring some imperical, experience to the table.
Not just as an aesthetic imbellisher.....

- Although we have noticed, that Ferrari Red paint in our tests:
- makes boats go .07% faster than Olive Drab......

On SES.
We did some work with Ulstein and others, a while ago. And we are aware
of the distance that has been experienced between practice and theory.

Some thoughts:
To maximize load and deck space people often come up with rectanguler
ships. Especialy tempting when twin hulls are used.
Now I know one of you published a paper that states that aerodynamics
has a minor effect with conventional craft at displ. speeds. Or words to
that effect.
However, it was also noted, that as Multi - Hulls have less boat below
the water line proportional to the total surface area - aerodynamic concerns
will become a greater concern.

We agree. So wind tunnel tests were done to test a theory of ours.
Not too Earth Shaking. Basicaly, that square boats will be less
stable than ones with pointy ends, as speeds increase.

Results were better than anticipated. So a working prototype was built.
With field tests supporting the lab work.

The people that worked on this project and myself, found a suprising
lack of rigerous inquiry into aeodynamics, re: ship design.

Another interesting consideration re: SES
Given:
That these ships are in " effect " - more low flying aircraft than
canal barges.....
That a safety factor closer to a plane is required to maintain useful
cruise speeds....
Are all composite hulls going to be the way to go ?

Cheers All !

[BMcF]

To messers:
RANCI OTTO, BMcf, Kach22i and Leo Lazauskas.

- Although we have noticed, that Ferrari Red paint in our tests:
- makes boats go .07 faster than Olive Drab......

We did some work with Ulstein and others, a while ago.

Are all composite hulls going to be the way to go ?

Hey now..I painted my Donzi 'Fountain Red' Imron because Reggie found out the same thing as you with regard to 'speed vs. paint color":p

Who is 'we'? ..I was on the original UT904 SES design team..much to my later chagrin, I might add. We (Loheed, Gore and I, working with Phil Curran's gang) did get that design fixed before/when it was later built as the UT928 by Oceanfast in Oz.

Every SES I have designed has included the effects of aero drag in the lift-moment-balance calculations and air tare measurements are always done during tank tests. It is indeed important..just hard to reconcile with the shapes dictated by the need to make it carry lots of cattle.. er..passengers..whatever.

SES are not quite in the realm of 'surface effect' as it is now more commonly known as relates to WIGS or air-entrapment hulls. As long as you supply the air from the forward end of the cushion to avoid 'presssure-gradient-induced tip-over', they otherwise operate at extreme speeds without drama. I could go in to a lot more detail about how high speed affects the distribution of cushion pressure and how aero drag affects running trim...anyone want to be bored to tears about the subtle niceties of SES design?

Unfortunately for me..I am not a member of the famous "100 MPH' SES club..those who got to hit that speed on the ole SES -100B got nice lapel pins to prove it. Fastest I have ever been on an SES is 59.8 knots..but she was 47m long, 260 tons, and rock stable doing it. No drama.

Composites?..they're great. So is aluminum. To be perfectly frank, I think both have their merits and both have their drawbacks..and both have been badly used to equal degree in high-speed ship construction.

The UT904 sure was a pretty thing though..all sandwich composite contruction too, as were all the Aa boats ever built.
http://www.braa.no/Produkt/snoggbaatar/bilete/tumbs/ses.jpg

[kach22i]

Potters, sculptors, daubers: any opinions?
Looks like I'm busted - working with clay.

My hovercraft study model, foam, clay, plastic sheet, and followed by many paper skirts fitted with pins like a taylor.

http://www.hoverclubofamerica.org/forum/index.php?showtopic=412&st=135
http://www.hoverclubofamerica.org/forum/uploads/1160490670/gallery_181_6_59642.jpg

http://forums.pelicanparts.com/showthread.php?threadid=297431&perpage=20&highlight=hovercraft&pagenumber=2
http://www.hoverclubofamerica.org/forum/uploads/1160490670/gallery_181_6_85772.jpg
http://www.hoverclubofamerica.org/forum/uploads/1160490670/gallery_181_6_17015.jpg
http://www.hoverclubofamerica.org/forum/uploads/1160490670/gallery_181_6_21583.jpg

http://www.hoverclubofamerica.org/forum/index.php?showtopic=962
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I'm still fitting the skirt using an artist method of what feels right. I make many mistakes this way, each mistake I learn something new. It's the process not the end results I enjoy.

The next skirt will be drawn using 3D computer software (for a cutting pattern), I imagine in a slightly different direction what the other two skirts before it were, yet building on my experiences and drawing upon them.

In the end it will have to be science, the begining must be artistic, at least for me it's more fun this way.

[DanishBagger]

Remarkably, there's a phrase in the ad in th epicture where you hold the model upright, that states "Jetted Tubs"

- somehow that seems fitting to such an awkward (but fun, might I add) project as a hover craft.

[FAST FRED]

That a safety factor closer to a plane is required to maintain useful
cruise speeds....

Aircraft only have a safety factor of 10% or 15%,

most boats use 300% to 400% to account for age , misuse , inexpensive design , construction mistakes ,battle damage etc.

HECK of a difference!

FF

[BMcF]

That a safety factor closer to a plane is required to maintain useful
cruise speeds....

Aircraft only have a safety factor of 10% or 15%,

most boats use 300% to 400% to account for age , misuse , inexpensive design , construction mistakes ,battle damage etc.

HECK of a difference!

FF

Exactly what I've been saying all along. If we could just get DnV to understand that difference and let us use airplane design safety factors..100 knot boats would be EASY! (not that I would actually ride on one though):D

[Leo Lazauskas]

I could go in to a lot more detail about how high speed affects the distribution of cushion pressure and how aero drag affects running trim...anyone want to be bored to tears about the subtle niceties of SES design?


In the words of Iggy Pop, "C'mon, bore me".

In return you might like to be bored to see the size of the hole in the water produced by our so-called "optimum pressure distributions".

"Wave patterns and minimum wave resistance for high-speed vessels"
E.O. Tuck, D.C. Scullen and L. Lazauskas.
Proceedings 24th Symposium on Naval Hydrodynamics,
Fukuoka, Japan (2002)
http://www.cyberiad.net/library/pdf/tsl02b.pdf

Leo.

[tri - star]

To FAST FRED:

It is not so much as to wether it's I0% or 400%
There can be a relatively, big difference between a disposeable fighter
aircraft and a commercial pass. jet,

However, all planes share a commonality.
If the Safety Factor is too large, a plane will simply not be able to:
- get off the ground. That's the main reason for such low S. Margins.
Some thing to ponder at 30,000 ft.....
When you feel a strange vibration.

Whereas; with a slow, ballasted sailboat, one can have pretty wide margins.
With liittle effect on speed.

Given that an SES ship, is in some ways, a failed air craft.
Desperatley trying to get back into the air........
It serves to make it as light as possible.

So as alum. or composites may be close in terms of weight savings....
Which gives the best choice in terms of:
Costs and / or aesthetics ?

[DanishBagger]

"disposable fighter jet"? Who makes one of those? Weapons' systems are rather expensive. So expensive, in fact, that I doubt very much that such a thing exist in this day and age. I can only think of the biplanes of WWI as "disposable fighters"

[FAST FRED]

"So as alum. or composites may be close in terms of weight savings....
Which gives the best choice in terms of:
Costs and / or aesthetics ?"

In aircraft at least that battle is being decided by Boeing and Air Bust as we type.

Boeing is in the all composite camp , Air Bust in the low tech mixed "composite" part aluminum part glue camp.Air Bust blew their weight goals , and the wing being tested BROKE early , but the French Gov rewrote the rules , giving them a "pass" on the 380.

The biggest difference between boats & aircraft is the level of engineering in the initial design and the more known quality of traditional AC construction and materials.

With enough CASH a really great light weight boat can be created , but as the racers prove , with multiple failures , its not a science ,just yet.

FF

[kach22i]

Art or Science...................

1. Contract for commision of original Art; if you knew exactly what you were getting, how it would be done and what it would look like, it would NOT be ART.

2. Contract for commision of original Architecture; you have some idea but not exactly what you are getting, know somewhat how it would be done and what it would look like before it is built, it is half ART half SCIENCE. That is if you accept science as engineering.

3. Contract for commision of engineering, engineering research and or science; you have a very good idea but not exactly what you are getting, know pretty much how it would be done and what it would look like before it is built, it is SCIENCE based, and proceeding towards pure engineering as you deal more and more with "knowns" verses "what if's" and waiting to see what will happen next as in science.

[tri - star]

DanishBagger,

you are missing the point.
If you read the fine print - when you sign up for the militatry
- it is commonly understood, that you do indeed;
become disposeable.
Wether private or officer - your duty is to serve.
Prepared to give up your life; to protect family and country.
Can you argue with this ?

The cost of a chariot or high tech. plane is irrelevent.
It will be quickly sacrificed - to the greater good.

Whereas; the millions of passengers on commercial jets have no
such expectations. - As demonstrated, by the fact that insurance
companies pay out compensation for deaths on civilian aircraft.
- And I'm sure it's rare for them to do so, for military personal.
Can you argue this ?

The point is that:
- It would be very suprising, that a fast military plane would be
designed with a greater safety factor - than a considerably slower,
civilian pass. aircraft.

The point is that:
- There is a long gradient curve re:
the Safety Factor used for designing a 6 knot sail boat to that
used for designing a Mach I fighter.
- With a DIRECT, unavoidable relationship between said:
- Safety Factor and the intended speed of the craft in question.

The point is that:
Given: That as the speed zone of an SES will approach the
take - off speeds of aircraft....
It must follow:
That the Safety Factor in designing, said SES, will be closer
to a plane; than that of a canal barge.

Or do you have some secret knowledge regarding the
Laws of Physics - that we simple souls are not party too ?

Or maybe, the subtleties of ironic humour, wizz right by you ?

Cheers !

[BMcF]

In the words of Iggy Pop, "C'mon, bore me".

In return you might like to be bored to see the size of the hole in the water produced by our so-called "optimum pressure distributions".

"Wave patterns and minimum wave resistance for high-speed vessels"
E.O. Tuck, D.C. Scullen and L. Lazauskas.
Proceedings 24th Symposium on Naval Hydrodynamics,
Fukuoka, Japan (2002)
http://www.cyberiad.net/library/pdf/tsl02b.pdf

Leo.

"The secret of being boring is to say everything."
Voltaire

I had that paper already. I have most of the papers the you, Tuck, Doctors and others have produced. ;)

The results, while very intriguing, remain elusive in practice due to our inability to design a workable mid-cushion pressure 'barrier' that is effective. The tests that I have done in the model tank (including one very recent one just last December) with divided cushions have proven that pressure differentials between cushion segments of more than a few percent are about all we can achieve with what we have 'in hand' for seal technologies. I should note that the objective in the tests we completed was to produce a 'cushion-based' pitching moment for motion control..nothing to do with drag modification/reduction...but the problem is the same.

[westlawn5554X]

Art and necessity.

[tri - star]

Thankyou FAST FRED:

Maybe; I will follow Boeings lead - and go for an All Composites design.

- As BMcF:

We have been requested to consider the challange of producing a
yacht, that pays attention to aesthetics - and also - uses
air cushion(s) too advantage.
( Putting aside for the moment, the concerns of using said, cushions to
maintain pitch control. - Which I have some thoughts on.)

The question to me is:
Not just can it be done - but is it worth doing ?!

Exactly akin - to the connumdrum posed originaly on this Tread.
Art and / or Science ?

Cheers All !

[Leo Lazauskas]

The results, while very intriguing, remain elusive in practice due to our inability to design a workable mid-cushion pressure 'barrier' that is effective. The tests that I have done in the model tank (including one very recent one just last December) with divided cushions have proven that pressure differentials between cushion segments of more than a few percent are about all we can achieve with what we have 'in hand' for seal technologies.


Thanks, BMcF, that's pretty much what I thought could be achieved.

Leo.

[BMcF]

Thanks, BMcF, that's pretty much what I thought could be achieved.

Leo.

Invent an effective way to partition the cushion to withstand +- 50% pressure differentials and you can retire from your life as a peanut-butter eating poor academic and snack on caviar. :p

[BMcF]

Thankyou FAST FRED:

Maybe; I will follow Boeings lead - and go for an All Composites design.

- As BMcF:

We have been requested to consider the challange of producing a
yacht, that pays attention to aesthetics - and also - uses
air cushion(s) too advantage.
( Putting aside for the moment, the concerns of using said, cushions to
maintain pitch control. - Which I have some thoughts on.)

The question to me is:
Not just can it be done - but is it worth doing ?!

Exactly akin - to the connumdrum posed originaly on this Tread.
Art and / or Science ?

Cheers All !

IMHO there is only one major reason to design and build an SES..to go much faster over longer ranges with less power. That said, I fail to see why guys that develop very high speed megayachts, like John Stallupi for example, ignore the SES when their stated goal is to go 'the fastest'. Beyond that however, the rather harsh ride and noise levels associated with an SES are problematic..and certainly not 'yacht like'..and then there is the issue I raised earlier about how one makes an SES 'look' like yacht is 'supposed' to look.

To play from both sides of the court: I can say from first-hand experience that traveling 50 knots on a 'flat-bottomed' 35m megayacht was worse in terms of ride quality AND ambient noise as compred to traveling the same speed in a 40m SES passenger ferry (in rougher sea conditions too). But there are some 40 knot yachts that do ride very well, so my particular comparison is biased.

You could design a 30 knot SES that would have twice the legs (or even more) of a 30 knot monohull yacht of the same displacement. Might make sense..but when you arrived at your destination with the SES, you then have the fun chore of swapping out the tips of your bow seal fingers (said items less than 1000 operating hours at 30 knots..500 hours at 45 knots) and changing out that rather expensive blob of rubber in back called a stern seal about every 3000-4000 hours.

[Verytricky]

Art is making a pretty boat.

Engineering is making a boat that works.



A true genius marries the two.

[DanishBagger]

Tri-star

I take it you have to be an american to think of "signing up for the military" as "becoming disposable".

You're rewriting the meaning of the word "disposable" in order to defend the constellation "disposable fighter", although most fighters cost the farm, or actually, many farms.

In reality, there are no such thing as a "disposable fighter" - ask around.
And the people that sign up for such service aren't disposable either, hence catapulting seats, so they can get out alive.

I'm thinking - I'm pretty much willing to bet that if you had the same amount of engineers and scientists working to manufacture a boat of a given design, that that boat could be much better than the civilian race-editions.

But, and I see this as the crux between boats and planes: THe forces acting on a plane is much more predictable than that of a vessel in water.

[bfisher33]

to agree with other members, Boat design is an artistic science. You have to be able to visualize the boat first, but then you ahve to make it work. Then you have to sell it. And to sell, it needs to look good. Unless its the navy. Or Exxon.

[Leo Lazauskas]

Invent an effective way to partition the cushion to withstand +- 50% pressure differentials and you can retire from your life as a peanut-butter eating poor academic and snack on caviar. :p

Firstly, I am not, nor ever have been, an academic. I just happened to work in a university maths department.

Secondly, macaroni cheese is the staple diet for students and hydrodynamic bums here. (On special occasions it's eggs and toast slices - aka googs and soldiers.)

Thirdly, in a recent paper, (Sept. 2006) Lawry Doctors and Chris McKesson used a 2000t SES as an example vessel. The air cushion is 72m X 17.5m and the cushion pressure is 12800 Pa. That's about 178 Pa/m. Does that seem high to you? When I last paid attention to achievable pressures, the "state
of the art" was about 165 Pa/m.

Regards,
Leo.

[BMcF]

So, Leo, you are a poor peanut-butter eating marine designer like me then?

20+ years of trying and I still can't get Larry to spell his name correctly. :p

I have always defined/used the cushion loading 'charateristic length' as the square-root of the cushion area. Using that definition, 300 Pa/m has stood up well over time as a good threshhold or target and the SES that Chris and Lawry are talking about comes in at about 360 Pa/m using my definition. A bit high, yes, but still 'OK' perhaps. The

In historical review, all the 'good' SES performers were at or below 300 Pa/m..some of the 'bad' ones, and there were many, exceeded even 400 Pa/m and were dogs. Looking at three of the 'best', the 40m SEMO SES ferry is at 293 Pa/m..the RNoN Skjold at 303 Pa/m..The SES-200 at 306 Pa/m.
( By 'best' I'm referring to where they fall on the Gabrielli curve in terms of transport efficiency..each of these three falls 'above the line')

I have not tried to see how a loading factor based on simply actual cushion length holds up against the data.

[Leo Lazauskas]

Looks like I'm busted - working with clay.


They have concrete canoe races, so why not clay hovercraft.

When you finish the real thing (or even before) I'd be happy to use it as an example for calculating resistance and wave elevations if you don't mind providing some dimensions and other variables I would need.

Regards,
Leo.

[Leo Lazauskas]

So, Leo, you are a poor peanut-butter eating marine designer like me then?

20+ years of trying and I still can't get Larry to spell his name correctly. :p


No, I'm not an engineer. It's you guys who keep us applied
mathematicians from having to get our hands anywhere near
high-speed machinery. Thanks for that.

Thanks also for the rule-of-thumb cushion pressure target.
I have seen Pc/Lc used by some Spanish and some Korean SES
designers. Pc/Lc=165 was considered as a maximum "state of
the art" ratio by Lindez, J.G. and Villa, F.M.G. in
"Fast Cargo Vessel: Concept Assessment", FAST 2001, pp.51-61.

I'm trying to put together a small set of SES designs to
illustrate some calculations of drag, wave elevations and
bottom pressure signatures. Eventually I would like a
reasonable range of vessels from existing small recreational
hovercraft and fast ferries to sci-fictional one million ton
SES. I used to have a "bestiary" of multihull arrangments
somewhere on the net: this would be a sort of air-supported
counterpart.

L.J Doctors is affectionately known as Lawry here. Come to
think of it, I've never heard of anyone in the U.S. with the
nickname Lawry. Perhaps Larry is the non-metric equivalent.

Leo.

[BMcF]

The Spanish did some good baseline work with their 'Chaconsa' SES testcraft program..but no Korean SES deisgns were ever built. There were of course, SES vessels built in Korea..but they were designed by 'others', like ourselves. As is so often the case in this bidness of 'boats what ride on air'..most of it is 'hot' air since we (the community of 'we') seldom get the opportunity to prove previous theories or expand upon new ones.

Fast 2001..I never received the proceedings from that one. I attended the first two 'Fast' conferences (Tondheim and Yokohama) and that was about it.

Does your program predict with or even deal with the effect(s) of water depth on ACV/SES drag? I've always had a hard time explaining to folks that air-cushion vessels have lower drag in shallow water than in deep water...and then follows the inevitbale questions about 'how shallow' and 'how deep'

[kach22i]

t.When you finish the real thing (or even before) I'd be happy to use it as an example for calculating resistance and wave elevations if you don't mind providing some dimensions and other variables I would need.

Regards,
Leo.
That would be great, it's kind of a cat with a front drape and seperate stern bag which I'm struggling with. I also have in model form (3 ft long) a kind of tri-hull hovercraft (one up two back) design. I'm not going to post that one, as I expect it to go straight but not turn well, I'm constanly re-thinking it.

About Korea (old post of mine):
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1042&hl=Korean

As Korea's first shipbuilding company with 6 decades of experience, Hanjin Heavy Industries is leading the world's shipbuilding, construction and industrial plant technologies.

http://www.hanjinsc.com/english/sub/industry/in_01b_e2.html
http://www.hanjinsc.com/english/sub/industry/images/in_02b_en03.gif
http://www.hanjinsc.com/english/sub/industry/images/in_02b_en05.gif
http://www.hanjinsc.com/english/sub/industry/images/in_02b_en07.gif
http://www.hanjinsc.com/english/sub/industry/images/in_02b_en09.gif
http://www.hanjinsc.com/english/sub/industry/images/in_02b_en01.gif

http://www.hanjinsc.com/english/sub/industry/in_01b_c1.html
http://www.hanjinsc.com/english/sub/industry/images/in_02b_cn01.gif

[BMcF]

Yes, the Koreans have done a lot with 'other folks' help to start with ..and have certainly expanded on the designs in some areas. I worked with some of those projects that you illustrated. HoverMarine (HM) SES designs from Tattersall and Lewthwaite..the 'baby' LCAC hovercraft developed with help from the USN LCAC design community, etc. Korea Takoma (the builders of the HM designs in Korea under license before they went Tango Uniform and were absorbed by Hanjin) was also negotiating to build Cirrus (Norwegian) 35m SES ferries at one point. And did you know that more HM-derivative SES' were produced - by far - than any other type before or since? Still quite a few of the 218s sporting around Hong-Kong and Macao, I believe.

[kach22i]

Yes, the Koreans have done a lot with 'other folks' help to start with ..

I'd like to know more about the Spanish efforts, I could not find much on the topic 'Chaconsa' SES.

Found this:
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1087

[BMcF]

That was in the 80s....not a lot of information out there from that period except what little was published 'on paper'.

[Leo Lazauskas]

Does your program predict with or even deal with the effect(s) of water depth on ACV/SES drag? I've always had a hard time explaining to folks that air-cushion vessels have lower drag in shallow water than in deep water...and then follows the inevitbale questions about 'how shallow' and 'how deep'

Yes, my programs can handle finite depth. Here's a plot of
the Newman-Poole wave resistance coefficient C_NP
for the "pure" ACV with L/B=11 I showed in a previous post,
but here finite depth results are included.
This (rectangular) pressure distribution has L=76.4m and
B=6.95.

I can also model how viscous layers on the surface of water
(e.g. oil slicks or ice slush) affect wave-making. It's
probably too weird to be of much use to anyone until the
icecaps melt, partially. When specialist SES are needed to
rescue floundering polar bears, I'll be ready!

It's probably easier to use displacement hulls to show that
the wave resistance in finite depth can be less than in
infinite depth. If people don't believe computed results
from, for example, Michlet, show them the experimental
results in the other graph attached to this post.

Leo.

[BMcF]

But..if I'm reading your graph correctly, it shows resistance increasing with decreasing depth...as one would expect with a 'normal' ship hull.

[tri - star]

To DanishBagger:
you make people's heads spin.....

Since; from at least Spartens days - all things military are expendable.
Remember, in school, the story of the Sparten boy - who dies rather
than to let on, to his superior that he has an animal under his cloak.

This story told, to show how a good soldier will die, rather than break
ranks and the incredible discipline expected in Sparta
- of even the youngest cadet.

Calling me an American - won't change history.
Or insisting that the sky is green.

Also, I'd gently suggest, that insulting Americans by inference, does
you little credit.

Finaly, your OWN words; support my arguement.
- And defeats yours.
i.e.
"......no such thing...." disposable fighter "..."
"......catapulting seats....out alive...."

What else is the pilot doing when he presses the ejection seat button ?
- But; turning his now - pilotless, Billion Euro / Dollar aircraft into -
" disposable " scrap.

' Regards.

[Leo Lazauskas]

But..if I'm reading your graph correctly, it shows resistance increasing with decreasing depth...as one would expect with a 'normal' ship hull.

Thanks, Bruce, you've jogged distant memories regarding some
anomolous results for finite depth I saw many years ago. (I
forgot all that at 6am when I posted.)

I've attached two graphs that show different results for a
L/B=2 rectangular pressure distribution.

The scanned plot is from:
Barratt, M.J., "The wave drag of a hovercraft",
J. Fluid Mech, 1965, vol. 22, part 1, pp. 39-47.
It was also reproduced in:
Doctors, L.J.,
"On the use of pressure distributions to model the
hydrodynamics of air-cushion vehicles and surface effect
ships", Naval Engineers Journal, March 1993.

The other is my calculation for the same pressure distribution
and plotted on the same log y-scale as used by Barratt. One
shows the result you want, (i.e. lower drag in shallow water),
the other doesn't. I'm not sure if the differences were ever
resolved. Maybe some good experiments could help, but they'd
have to be conducted in a very long, very wide basin.
Leo.

[Verytricky]

Also, I'd gently suggest, that insulting Americans by inference, does
you little credit.


Yes, but as you must realise - its soo much fun to do so, especially when they dont realise you are doing so....:P

[DanishBagger]

To DanishBagger:
you make people's heads spin.....[quote]

Why thank you. I really do try to look my best every day. Especially the lassies like my kilt, or rather what's under it.



[quote]Since; from at least Spartens days - all things military are expendable.
Remember, in school, the story of the Sparten boy - who dies rather
than to let on, to his superior that he has an animal under his cloak.

I'm sorry, but what you were taught as a child about ancient times about this has very little bearing on todays military efforts. There is a difference between, say, giving a child a sword, a pad on the shoulder, and off he goes to war, and todays war scene were a fighter jet cost up to a dizzying 330 million US$. Those planes aren't "expendable". I'm sorry to say.



This story told, to show how a good soldier will die, rather than break
ranks and the incredible discipline expected in Sparta
- of even the youngest cadet.

But what the story is really about is telling the soldiers that they're figthing for a "greater cause", not telling them that they are expendable.

Warfare has changed from the days of Troja just like no huge building projekt will be built like the great wall of china was.


Calling me an American - won't change history.
Or insisting that the sky is green.
Nope, but "ancient history" (which, btw, your story isn't - the story is just that - a story, a myth with a morale, not history) Has little bearing on todays costs of war, and what weapons systems (and -carrriers) are "expendable"



»Also, I'd gently suggest, that insulting Americans by inference, does
you little credit.«

well, you know, americans are the worst - I mean, whenever I go there, the women can't stop themselves from slipping their hand up under my kilt. "Just curious," they claim, but I know better. I know they can tell I'm a real viking. And as you know, vikings conquered a lot of england, not by means of the sword, but by taking a bath once every week, and so they wooed the women. ;-)



»Finaly, your OWN words; support my arguement.
- And defeats yours.
i.e.
"......no such thing...." disposable fighter "..."
"......catapulting seats....out alive...."

What else is the pilot doing when he presses the ejection seat button ?

He is saving himself. Two reasons for this. Noone would be a fighter pilot, if they were killed because they couldn't get out. Secondly because people are worth more than the plane in the end. But there's a reason they don't use it, until they really do have to, and not at the first sign og trouble. If they were "disposable", they would simple just push the button at the first sign of trouble. "Disposable" have the connotations "single-use", "low quality", "if slight defect, toss away" and so forth. Fighter jets aren't disposable.

- But; turning his now - pilotless, Billion Euro / Dollar aircraft into -
" disposable " scrap.


Nope, that is false argument. That is like saying that because the fire brigade that tried putting out fires in both XX and the next door house, YY, and they at some point had to choose, because of lack of water or firemen, then the house that couldn't be saved, say, yy, was then a "disposable" house. Sorry, but that is simply not true. A house, doesn't become "disposable" because it couldn't be saved. A disposable house would be a house, where there from the get go to the designing of it, would have a huge lack of features in order to save money, so it could be cheaply replaced, and if damaged, tossed away, and built to last for a very short time period. Such a house would propably have lacquered card board as roof, egg-crates for walls, heat would be a wooden stove, the toilet a ditch outside, the kitchen would consist of a pot on said stove, and the water would be run on footpumps in a portable watertank. Electricity? A single lightbulb in the roof, run by a small solar panel on the roof.

(To the americans, don't take the jabs at americans too seriously - especially the viking-stuff).

[BMcF]

Thanks, Bruce, you've jogged distant memories regarding some
anomolous results for finite depth I saw many years ago. (I
forgot all that at 6am when I posted.)

I've attached two graphs that show different results for a
L/B=2 rectangular pressure distribution.

The scanned plot is from:
Barratt, M.J., "The wave drag of a hovercraft",
J. Fluid Mech, 1965, vol. 22, part 1, pp. 39-47.
It was also reproduced in:
Doctors, L.J.,
"On the use of pressure distributions to model the
hydrodynamics of air-cushion vehicles and surface effect
ships", Naval Engineers Journal, March 1993.

The other is my calculation for the same pressure distribution
and plotted on the same log y-scale as used by Barratt. One
shows the result you want, (i.e. lower drag in shallow water),
the other doesn't. I'm not sure if the differences were ever
resolved. Maybe some good experiments could help, but they'd
have to be conducted in a very long, very wide basin.
Leo.

Err..it's Bill..not Bruce. Bill McFann..;)

The shallow-water effects are well-known to operators, but not well-characterized in the 'science'.. The USCG guys used to 'cheat' the shallow water in the Carribean with their BH110 SES patrol craft to gain speed; during builder's trials, we used to routinely run the 50 knot SEMO 40m across a known shallow bottom area to gain as much as 4 knots on the top end when 'showing off'; I used to bring my SH-2 5-pax hovercraft in close to shore and shallow water to gain a 'lift' and get the thing back over hump and accelerate faster..etc. My 'best guess' was that the phenomenon had to do with the bottom, in shallow water, restricting the formation of the cushion wave depression as deeply as it is in deeper water.

[BMcF]

[QUOTE=DanishBagger;129170
(To the americans, don't take the jabs at americans too seriously - especially the viking-stuff).[/QUOTE]

Hard to get this American riled up about stuff like that...but you could have left out the part about the kilt..:eek:

[Leo Lazauskas]

Err..it's Bill..not Bruce. Bill McFann..;)

The shallow-water effects are well-known to operators, but not well-characterized in the 'science'.. The USCG guys used to 'cheat' the shallow water in the Carribean with their BH110 SES patrol craft to gain speed; during builder's trials, we used to routinely run the 50 knot SEMO 40m across a known shallow bottom area to gain as much as 4 knots on the top end when 'showing off'; I used to bring my SH-2 5-pax hovercraft in close to shore and shallow water to gain a 'lift' and get the thing back over hump and accelerate faster..etc. My 'best guess' was that the phenomenon had to do with the bottom, in shallow water, restricting the formation of the cushion wave depression as deeply as it is in deeper water.

Sorry, Bill, I don't know where I got "Bruce" from. It's
worse with your offsider, Loheed. Every time I see his name
in my email box I whacky-parse it as Lockheed and imagine
offers in the millions.

The differences in the results for shallow water might just
be a failing of linear theory. Perhaps lubrication theory
is more appropriate in some cases, or perhaps non-linear terms
are required. But I take your point about shallowness tending
to suppress the formation of a large depression. Maybe that's
what I need to prevent the 36m hole under our "optimum"
pressure distribution. I'll see what Ernie Tuck has to say on
the matter when I see him next.

Modelling in shallow water (and towing tanks) is further
complicated by the formation of a bottom boundary layer,
but that would normally increase drag.

I have long suspected that builders use tricks during trials
to increase speeds by a few knots. In modelling the
performance of an Australian catamaran I found that the
claimed top speed of 52 knots seemed achievable, (and was
achieved in practice), but only in the empty condition, and
only because in that condition dynamic sinkage and trim let it.
But with a fairly small load in my model, the cat just didn't
seem able to get into the right attitude to reach 52 knots.
Maybe it is Ok to describe it as a 52kt cat. Or maybe it's like
60 Minute Drycleaners - it's just the name of the shop. It
doesn't really mean that your clothes are ready in an hour.

Leo.

[BMcF]

Rick's last name used to be Lockheed..but he changed it so he would stop getting all the junk mail queries asking for large donations of cash. :p (kidding)

'Tricks' to inflate speed numbers?? I have no clue what you are talking about. ;) Although I must admit found it a bit odd that we achieved speeds in whisper-calm fjords in Norway that were 'seldom seen' ever again after delivery.:) Probably something to do with the wind shear off the sides of the fjord cliffs..or maybe the water runs downhill a bit as you are headed toward the North Sea. One thing is certain..it wasn't shallow-wter effects in that case. But runnign speed trials in amongst the archipelago of islands off the southern tip of Korea..whole different story.

[Leo Lazauskas]

Although I must admit found it a bit odd that we achieved speeds in whisper-calm fjords in Norway that were 'seldom seen' ever again after delivery.:) Probably something to do with the wind shear off the sides of the fjord cliffs..or maybe the water runs downhill a bit as you are headed toward the North Sea. One thing is certain..it wasn't shallow-wter effects in that case.

And then again it might have been. :) Depends on what lane you were driving in.

[tri - star]

To DanishBagger:

Glad to see you are now in agreement with me.
" .....people are worth more than a plane in the end."
As you say; people are less disposable than a plane is.

However; we all trying to grasp how you intend to tie:
kilts, fire brigades, American women, card board houses
and a small solar panel - into the original question ?
i.e.
".....art or science ? "

- To the Moderator:

When on these Forums does:
".....just kidding with you."
- Go over the line to; off - colour, rude and insulting ?
- To off - topic ?

With Regards.

[PI Design]

Military planes/ships/subs are certainly not designed to be disposable. They are designed to the very highest standards and place an enormous emphasis on protection and survival. If commercial ships were designed, built, operated and maintained to the same standards as naval ones there would be far fewer accidents and lost ships (but the would be prohibitlvely expensive...).

Low Safety Factors do not mean taking greater risk with the deign. They imply a better understanding of the loads, material properties etc, so that the designer has more confidence in the precision of his sums. Aircraft loads are more predicitable and more research has been undertaken in aerospace than yacht design, so aerospace safety factors are lower (which they need to be).

[DanishBagger]

Tri-star,

If you can't take a good-humoured jab, then I'm sorry.

The kilts, women and so forth tie in with the topic, just as much as your own remark that fighter jets and military personel are disposable. If you actually read what I wrote, then it might be a bit clearer, dear.

Again, I'm sorry that you feel the need to cry "moderator" because I, from the first remark simply disagreed with you that people and fighter jets were "disposable". But then again, I see you're out of reach, and that you will not accept being countered. Not to mention that you think you can speak on behalf on everyone (i.e. "we all trying to grasp").

Don't worry, you'll be ignored by me from now on.

Edit: I am certainly not in agreement with you. You're twisting my words, in an effort to make it look like you're right. It's a strawman. (and before you ask "how strawmen tie into the discussion", look it up.

[dccd]

An interesting argument, long debated. I've come to the conclusion that 'art', at the least in terms of what is 'pleasing to the eye', cannot be entirely ignored at the expense of 'form follows function'. To wit, one of my favorite examples follows and both vessels 'hit the water' at approximately the same time, so the comparison is valid in the sense that one would have to assume that all facets of both art and pure science/technology, that are (or are not) evidenced in each, coexisted.

The 'worlds fastest megayacht'...as once claimed anyway..
http://www.braa.no/spesielt%20interesserte/bilete/tumbs/moonraker%202.jpg


The worlds most efficient high-speed vessel in it's size range:

http://www.seariderinc.com/SES%20Photos/Sites-Images/17.jpg

The first relies in a hull design akin to a Hickman sled with a point stuck on it and thus has motions that will cause injury when operating at 50 knots in a 2 foot chop (not kidding..been there). At 116' LOA and roughly 100 tons, it made a little over 60 knots using two 16V396 MTU diesels and one TF40 gas trubine, all through KaMeWa jsts.

The second, an SES of 160' LOA and 220 tons, achieved 47 knots with only the two MTU 39616Vs and two 6V396 lift engines and would have achieved over 60 knots with same power as installed in the 100-ton yacht. Of more importance in my mind than the fact that we're talking twice the displacement as the yacht, the SES motions were acceptable, even under fairly high sea conditions in which the yacht would barely manage to slog through.

Post-script: The turbine has long ago been removed from that yacht and it now makes 35 knots with the twin 16V396 diesels.

The moral of the story?...the yacht 'looks' like a killer performance machine..the SES looks..well..just plain ugly. So in the years since both were on the scene, many Moonraker look-a-likes have been built and more will be; many with the same horrible hull designs..but very few vessels based on the SES and certainly none that were 'yachts' The superior performance of the vessel based only on 'best engineering and science' principles is not what people want to look at, own or operate apparently.

We've always lamented that we fail to find ways to do both well. If we could do so...the 'worlds fastest megayacht' would be once heck of a lot faster than they are now.A true SES' (not air-lubricated Burg or Harley stuff) have all suffered from an "almost usable deck 5' to 7' deep, of cross structure under the first deck, this results in a very tall/large frontal area compared to a conventional hull/superstructure. In the speed range everyone agrees a SES should shine >50knts, it is the massive aerodynamic drag that is the great majority killer of a common SES's efficiency. The speed range demands a sleek profile which is also absent from previous designs.

In my new design I applied a wave parting centerline keel to reduce that extra structural deck height and cut the total aerodynamic drag. True, the center hull will add some drag in a seaway but the preponderance of it remains out of the water. The side hull drag is also reduced 80% due to the short sponsons, which still lend the stability and directional assist that remains an advantage over full hovercraft.

Your insight and educated comments regarding this concept are most appreciated see the basic design shape at: http://www.industrialobject.com/50pb.html

[Leo Lazauskas]

That's a nice looking boat, but your central hull is just a
variation on a theme used for many years by Incat. Whether
you can get away with a lighter cross-structure really depends
on the mission. A large cross-structure might be unavoidable
if SES are required to carry very dense loads such as army
tanks or some presidents.

Your point regarding air drag is certainly valid.

Here are a few numbers to consider (when you get past the
dazzling artistry of my drawings).

My example hybrid vessel has similar proportions to a
260t Skjold SES. As you can see it has a fairly large
frontal area.

Drag components (non-dimensionalised by the weight) are
shown for an on-cushion condition with 80% of the weight
supported by the cushion. I had to estimate the skirt clearance
height hskirt and a few other air cushion parameters, but they
shouldn't be out by too much.

I've used an air drag coefficient of Cdair=0.4 in the drag
calculations which is probably a bit low. As you said, above
about 50 knots air drag is significant, more so if a larger
value of Cdair was appropriate.

I'm still not sure if your idea of tucking some above-water
volume under the wet deck will reduce the drag by very much.
I'm also not sure how strong and heavy the central hull must be
to withstand the wave loads it might be subject to. Will the
central portion weigh the same as the material you save by
reducing the height of the superstructure? Or will it be
heavier?

Also, what do you mean by "The side hull drag is also reduced
80% due to the short sponsons"?

Good luck!
Leo.

[dccd]

Yes the central hull is like the Ncat, but when on cushion only the aft end of this hull skims the surface with allocation for the propulsion units. Structural weight as a function of pressure loads calculated by DnV rules are not really driven by speed. Off cushion slam loads are the pressure driver, so the weight is similar as if flat, just increased in depth at center minimized on ends like a good girder span should be.

Side hull wetted surface is going to be cut significantly compared to a standard SES, these sponsons are shorter.

As a yacht, this vessel is not "demand" operated, they can choose to avoid the roughest water, where the centerline hull form would be most wet, however it would still be less drag/hull weight overall than a wave piercer.

I have been intimately involved with the LCAC, Bell Halter 110 and 70', Destriero design and a dozen other exotic hull forms real and imagined, so it is a compromise as they all are, but one geared for a earth ranging yacht. Efficient high density loads will always be in the domain of a sea plow.

Here are a few dimension for your measure:p : cushion hgt 12',

main deck, cushion to bridge dk 10.5', bridge 8.5' And a picture of the primary skirt, w/o cvk and transverse divider. Thanks

[Leo Lazauskas]

Here are a few dimension for your measure:p : cushion hgt 12',

main deck, cushion to bridge dk 10.5', bridge 8.5' And a picture of the primary skirt, w/o cvk and transverse divider. Thanks

Thanks for the dimensions, but they aren't much use on their own :)

Will this vessel have conventional skirts fore and aft? I couldn't see their arrangement from the drawing on your www site.

Regards,
Leo

[kach22i]

Your insight and educated comments regarding this concept are most appreciated see the basic design shape at: http://www.industrialobject.com/50pb.html

I trust you don't mind me taking a shot at it.

The concerns I have of your design, I have of my own design (on paper and as foam model three feet long).

The stability comes from craft length in a straight line, and from width in a turn.........in a very simple argument model, right? And also a three-legged wheelbarrow is a rather unstable configuration.

I see your design doing pretty good in a straight line; it's the first turn, which turns me pale with fear. Mind you I have the same reservation with my design, which is pure amphibious hovercraft, using inflated tri-hull sponsons. My side sponsons are twice the length of yours, and the center front sponson is half as long (more or less). I have a double bag stern skirt planned (built one on my 10' hovercraft to get the feel for) and over sized giant fingers for the in-between bow seal and compartmentalization underneath connection between all inflatable air cushion sponson bag skirts.

I see the design you linked to dccd, performing much like a mono-hull until in a turn the drag or torque generated by the inside side sponson kicks the stern around in a unpredictable way. I hope I’m wrong, because it would only help my own design to be so.

Cheers, George/kach22i

[BMcF]

A true SES' (not air-lubricated Burg or Harley stuff) have all suffered from an "almost usable deck 5' to 7' deep, of cross structure under the first deck, this results in a very tall/large frontal area compared to a conventional hull/superstructure. In the speed range everyone agrees a SES should shine >50knts, it is the massive aerodynamic drag that is the great majority killer of a common SES's efficiency. The speed range demands a sleek profile which is also absent from previous designs.

In my new design I applied a wave parting centerline keel to reduce that extra structural deck height and cut the total aerodynamic drag. True, the center hull will add some drag in a seaway but the preponderance of it remains out of the water. The side hull drag is also reduced 80% due to the short sponsons, which still lend the stability and directional assist that remains an advantage over full hovercraft.

Your insight and educated comments regarding this concept are most appreciated see the basic design shape at: http://www.industrialobject.com/50pb.html

I would have to ask the same questions as Leo did..i.e. I can't quite envision how you are integrating seals and air supply in that concept.

I don't quite agree that aero drag is as big a factor..at least not in the range of 60 knots. Having a Cd of 0.25 vice 0.5 might mean halving the aero drag component, of course, but that component is still a very small part of the total drag. That's not to say that I think reducing aero drag is not a good goal..and a 'sleek' design is always going to be viewed more kindly than one that looks like a BH 110. :D That was the point of my earlier post, after all.

Our paths must have crossed at some point or other..since I worked on all the same vessels that you mentioned. When I'm feeling verbose, I'll tell the story of my miserable 'encounter' with a Burg 'SES' design - longest short boat delivery trip I've ever made.;)

[kach22i]

When I'm feeling verbose, I'll tell the story of my miserable 'encounter' with a Burg 'SES' design - longest short boat delivery trip I've ever made.;)

But this sounds like the skirtless SES cat you seemed to favor?

http://www.seacoaster.com/High-Speed-SeaCoaster.htm

Things did not go as planned I assume?

[BMcF]

But this sounds like the skirtless SES cat you seemed to favor?

http://www.seacoaster.com/High-Speed-SeaCoaster.htm

Things did not go as planned I assume?

I seemed to favor that thing??..au contrare mon frer! (pardon the Spanish) ...where would you ever get that idea? The concept is notable however..notable in the number that have been built but didn't work. I've never seen a 'concept' that had legs like that one..it's as if nobody wants to admit it's crap and are hell-bent on building one after another to 'get it right' someday.:rolleyes:

[BMcF]

The patent for the SeaCoaster hullform is held by Air Ride Inc in Miami in the US. Don Burg of Air Ride, who invented the hullform, has successfully applied it to a variety of craft, including a 65ft SeaCoaster catamaran ferry that remains in operation - Island Express Boat Lines has been operating a 149 passenger SeaCoaster ferry on Lake Erie since 1999.


..said passenger ferry being up for sale in Boats and Harbors rag for..just about forever. Fire sale price..:D

[kach22i]

I seemed to favor that thing??..au contrare mon frer! (pardon the Spanish) ...where would you ever get that idea?
Sorry, maybe you just said some people were working on eliminating skirts altogether for maintenance reasons.:)

[BMcF]

Sorry, maybe you just said some people were working on eliminating skirts altogether for maintenance reasons.:)

Not 'some people'..just Don. The skirtless SES has been his 'Holy Grail' for as long as I've known him (20 years). Don's a great fella..just permanently fixated on the idea that somehow the SES would be better if it had no flexible seals. I have to disagree with that..and always have. The 'proof' has been visible to all..there are plenty of true SES vessels that worked well.

[dccd]

I feel I owe this thread some more on-subject comment:

Art Vs Science? My own interest in this thread was due to the mention that the SES hull is a technically better hull form, but was too ugly to sell as designed by engineers. I hope to show that my attempt to use the superior performance of a SES can be made aesthetically acceptable or at least not ugly with a little proportion and streamlining.

No dispute that a talected artist can sell a beautiful yacht design that is difficult to construct, but I have never seen one styled that could not be creatively engineered to work below the waterline. By the same token we have seen many expert engineered concepts with no mega yacht buyers (SES, SWATH, most Catamarans). I think this is the the frustration of many engineers in that they went to University and suffered to be highly trained in their "Art" but the "flighty artist" always gets the credit for the high profile yacht. They feel overlooked in the glamorus world of yacht design, Its the only reason for this debate

So IMHO, art or science is dependent on type of vessel. Mega yachts are sold by triggering some passionate response in the client due to a pleasing or sometimes bold form (well engineered always being assumed by the megayacht buyer), commercial boats are sold on cost, efficiency and utility, military on performance and reliability. Only in the motoryacht arena is the focus on art, when their are no more appreciative rich clients, the art of it will be gone. That has happened in land based architecture, I am sure their are talented artistic architects frustrated with no individualist capitalist clients looking to make a statement as in the 30's to 50's. Read Tom Wolf's "From Bauhaus to Our House" for more about that. I fear the day when mega yachts are designed by committe of number cruchers as all "mega" building are done today.

BMcF is very right about the other seal less SES's, the US Navy is still pumping money into many repeated public failures which only wound us in the marine design world. More private, I'll conceived "advanced" marine projects are presently in the works and I cringe for the repercussions coming our way.

Leo, I hope I managed to attach a new seal graphic in answer to your recent post, if not, stay tuned to my web site.


http://www.industrialobject.com/tech.jpg

A view of the perimeter seal, with sponsons and centerline hull removed, there is a center line internal web seal and a transverse seal about 1/3rd back from the bow, see orange lines.

[Leo Lazauskas]

Leo, I hope I managed to attach a new seal graphic in answer to your recent post, if not, stay tuned to my web site.

A view of the perimeter seal, with sponsons and centerline hull removed, there is a center line internal web seal and a transverse seal about 1/3rd back from the bow, see orange lines.

Thanks, dccd.

I think that the "equivalent lift" is going to be a greater problem that air resistance. Have you calculated the drag components yourself to estimate the power and the engine size you will need to get your beautiful set of teeth over 50knots?

[dccd]

Thanks, dccd.

I think that the "equivalent lift" is going to be a greater problem that air resistance. Have you calculated the drag components yourself to estimate the power and the engine size you will need to get your beautiful set of teeth over 50knots?


Yes lift is known, keeping the weight down is the typical challenge :rolleyes: . The seal design shown is a incomplete sketch, it will have closed fingers along the sides, open fingers forward. The new LCAC deep skirt is interesting in that they closed all the side fingers ,the side finger bottom planeing flaps fold onto the one aft of each other, sort of forming semi-ridged sidewall. Also removed the center longitudinal cushion divider and the drag went down considerably. only the mid transverse seal is left, a more simple fore and aft cushion cell design now. I guess the stiffer side seal/fingers make up for the loss of the centerline divider. All in all very interesting.

I will leave my cushion in a triple divided design one cell forward of the transverse, the center hull dividing the aft cushion into P&S cells.

[Leo Lazauskas]

Yes lift is known, keeping the weight down is the typical challenge :rolleyes:

I'm probably using the wrong terminology. By "equivalent lift" I mean the power required to sustain the cushion. This can be converted into a resistance component as shown in the graph in my previous post. To me it seemed that there would be greater losses because of the longer than usual perimeter. However, if your skirts are unconventional it might not be a major problem.

Cheers,
Leo.

[BMcF]

I will leave my cushion in a triple divided design one cell forward of the transverse, the center hull dividing the aft cushion into P&S cells.

I'm assuming that the fore-aft division is envisaged to be aprt ofthe felxible skirt system. Why do you have that added level of complexity?

Your design is certainly a 'looker', something always lacking in most SES concepts. About the 'best looking' we've ever come up with is shown below; it was part of a proposed demonstrator for a new propulsion system and the client wanted a vessel that would reach speeds that got a lot of attention for their new hardware. It was not an SES development effort..quite the opposite in fact - it was 100% grounded in prior art so that the actual vessel did not indavertently become part of the propulsion system development effort.

..based on a very conventional SES platform configuration. It still has a lot of the "BH110 slash commercial pasenger ferry" look to it.

http://www.supermotors.net/getfile/499773/fullsize/big4view.jpg

[dccd]

The complexity of my bi-furcated cushion is there for an additional measure of pitch stability.You represent, by way of good questions, the professional nature of this forum, it is like re-living the early design cycle questions we solved before moving forward. I'll answer as brief as possible since if I were to diagram it out, it would only invite more detail request and none of us have that much time.

The 110' SES was a great demonstrator (circa 1980), but built before its time, those old DD16v engines were half the power of the same weight of 4 stokes today. I also did a looker design based on the same 110' proven design for Trinity Yachts, back in 1989! (attached) It is showing a longer length due to the swim platform and a little sharper bow piece. As with my recent design, I think there are going to be sales for SES's as soon as we make something marketable for that clientele. I hope it also shows that the "proven art" can be made handsome too, I have seen a few Euro ferries adopt swept-form techniques like in this design since it was publicized 18 years ago (wow). http://www.industrialobject.com/110sessmall.jpg

[BMcF]

Diana Yacht Designs had a sleek SES on the boards..Cheoy Lee's was not bad looking but was, unfortunately, of Burg heritage..and you probably know all about John Conner and his Gentry project. So I know that the combination of designers and artists can get it done..but I'm only and strictly a designer..a techology guy.. I design whats below the gunwales (SEMO's 40m and the RNoN Skjold and MCMVs to my team's credit) but heck if I can make one look good.

I'd like to chat further with you about your approach to pitch stability..vice the single cushion with 'staggered LCG, LCB and LCF lift centers' approach that we evolved and is evident on Skjold, for example.

Who the eff are you anyway?..too many 'common' projects to not have run each other over at some point. Shoot me a PM.

For Leo: Lawry and Chris McKesson and I got to shoot the breeze yesterday..where were you?:D Just as well..yr eyes would have been rolling out of yr head as once again a bunch of ivory-tower computer guys explained in depth why linear simulations can't work for predicting vessel motions. What they have not explained yet is the apparent anomoly of why mine have worked so well for 25 years. Compare junk with data and ya got nuthin..I don't care if its linear frequency-domain stuff or not.:rolleyes: But I digress yet again in to a rant that 25 years of repeating has worn slap out...:D

[kach22i]

As with my recent design, I think there are going to be sales for SES's as soon as we make something marketable for that clientele.
Yes, I agree and see SES sales taking off long before fully amphibious hovercraft. The major reason being the SES looks and behaves much more like a boat. After isn't a SES a derivative of a fast catamaran?

Really nice design(s) dssd, did you get my e-mail?

SES pdf I just found in my computer, what timing.:)

What's the poop on the Harley SES? See pages 39 thru 43.

[BMcF]

After isn't a SES a derivative of a fast catamaran?


Actually no..the SES was around as the 'sidewall hovercraft' for quite some time before Westamaran debuted their frumpy-looking 'fast' powered ferry cats (W88?) in the 70s. The invention of the SES (patent-wsie anyway) is attributed to a good friend of mine, Al Ford...said patent granted in the 1950s. However, the first SES that I am aware of was invented by Thornycroft in the late 19th centry and the tow-tank model still exists. Of course, Herreshoff had his sailing cat at the same time..but the SES and cat designs never converged as competing (and similar looking) powered concepts until recent times.

[kach22i]

Actually no..the SES was around as the 'sidewall hovercraft' for quite some time before Westamaran debuted their frumpy-looking 'fast' powered ferry cats (W88?) in the 70s. The invention of the SES (patent-wsie anyway) is attributed to a good friend of mine, Al Ford...said patent granted in the 1950s. However, the first SES that I am aware of was invented by Thornycroft in the late 19th centry and the tow-tank model still exists. Of course, Herreshoff had his sailing cat at the same time..but the SES and cat designs never converged as competing (and similar looking) powered concepts until recent times.

I've always thought of the SES as a type of hovercraft, but marketing wise it's may be best to sell it as something more familiar (CAT).

Thanks for the history lesson BMcF, these names are all new to me (know "Thornycroft " though).:)

[AleX`G]

IMHO if you are building something that needs to serve a purpose then you need to base your ideas on science to make sure it works. Anything beyond that will affect how it works sometimes the raw design may look good as soon as designers add things they compromise even more on the efficiency at which the thing does its job.
I would say the same is true for buildings and boats as well as cars but buildings is more inclined towards art because they can get away with so much 'adding of stuff' that it will not compromise the efficiency of the building.

There is not much art in a plane because if there was it wouldnt fly. I would say on the other hand that art can inspire ideas and that in turn is science but people who actually practice art in this way are judging the efficiency of the thing on its effect on humans and our brains more of a mental efficiency more than a physical one.

Alex

[ssnoopys]

Hello,
I am totally agree with your opinion that boat design is an art but In now days it is running as a business in art.

[NADreamcatcher]

Perhaps artistic viewpoint belongs to the eye of the beholder but the focal point of view through a lens from the same point of view is science. Black is to white what economics are to desire.