boat design - art or science?

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.

 

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)

 

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.

 

Safety factors

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 ?

 

"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"

 

"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

 

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.

 

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 !

 

"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.

 

Art and necessity.

 

SES with aesthetics...?

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 !

 

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.

 

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.