MARINTEK VERES: catamaran seakeeping calculations

You posted that with the intent to provoke envy..right?

 

And sympathy. My family have banned me from nipping down to the shop in pyjamas until I become a full professor.

 

Seems a bit unfair and overbearing to me. Now if you were doing that still with your bunny slippers on....


Switching gears (much needed..I'm all out of mind's-eye bleach): It baffles me no end that the most energy efficient form of high speed marine transport..the SES..recieves so little attention and has been nearly written off in this brave new world of "anything green".

 

I think you're going to have to define what you mean by most energy efficient

 

Even using the more refined definitions of transport efficiency that Colen Kennel developed as an extension of the Gabrielli-Von Karman boundaries..the SES still dominate the higher Froude number region by significant margins. And that was before the extreme L/B Sea Train number was plotted.

So..my submerged-hull loving friend..what choo got?

 

I can think of a few reasons for their lack of acceptance.

First, think of how long it took for catamarans to be
accepted as a realistic form of high-speed transport.
SES are more complex and will take longer IMO

How many NAs/engineers are familiar with SES operations/design?

 

Well, this is the trouble with paper jockeys comparing figures of their own methods.

Take CK's here:



His results are very different to these:



It is down to how "they" define their models for transport efficiency.

I take a somewhat different view.

What is the payload to lightship ratio....ie how much can it carry compared to its own weight. Then what is the weight of the lightship, at its given deadweight, compared to other vessels of same size and then speed and then power.

ACV/SES have significantly higher lightship weight. Just on that point, they are poor. Not to mention maintenance cost of all those fans buzzing about and the thirsty GTs etc.

So i take a dim view of these Transport Efficiencies when they rarely have an injection of real design parameters other than what is published publically, which is often inflated at best and woefully inaccurate at worse.

I prefer things in skirts that walk and smile

 

Leaving aside your trips to Thailand for a moment...
Is there any alternative to SES for speeds > 60 knots?

 

Well, yes and no.

As always it depends on the SOR...what is the vessel for?

If it is to carry a small number of heavily armed personnel under the radar, then there are plenty of interceptor type vessels that can and do over 60knots.

If you want to carry say 400 passengers, it starts to get tricky. Standard 40m cat's can easily do 40-45knots. If you want to go faster then you're into GT's and really need to make the vessel longer. One of our 40m cats did 53knots on sea trials...so pushing it, it could be done. But at what compromise and how would it compare, weight, running costs, deadweight, available route and seakeeping etc etc to a similar size SES, hard to tell.

If really big then of course the Fn number gets less, but you're talking very large vessel with huge amounts of power anyways.

But that of course leaves out WIGs too.

So, like with all things design, it is not so much can you go over 60knots, it is really a case of why and what are you doing at those speeds...that dictates the design rather than a singular parameter.

But if your skirt inclined, then it shall always be SES regardless

 

Bill might have others, but the SORs I work to in my (obviously
non-practical) research were defined in several CCdoTT and other
documents.

Then there's the "100 knot navy?" fantasy requirement:
250,000 tonnes delivered in 7 days to anywhere (let's
say coastal areas) in the world. And 1 million tonnes
in 28 days.

I do take your point on the dodgy estimates of lightship weights
some people use. But, hey, how else are they going to get that
grant?

Where did you get CK's figure from? Was it from the "pig face" talk
(or variant thereof) I have attached?

 

No, from this interesting paper, which reviewed several ways of looking at "transport efficiency" and comparing them

View attachment HSMV_Proceed55.pdf

 

Thanks. I do have that one, but I didn't have time to trawl through the
dozens of others like it before posting.

 

Nothing tricky about that particular point of comparison at all..and I've personally tested many of both. The SES versions burn 35-40% less fuel doing it...simple as that. Its that efficiency we are talking about.

 

More recently..the USN commissioned the design of a high-speed ocean-capable transport vessel that could achieve 45-50 knots in SS5 conditions or thereabouts.

Multiple contract awards were made to numerous NA firms and the program continued ofr several years through three phases.

The hands-down winner was segmented SES design; its power requirements were within the realm of OTS propulsion equipment whilst that of the competing designs was off the charts.

Note: no idea why I quoted my prior post..and too lazy to fix, so call me a narcissist.

 

But that's my point. It isn't just about burning fuel.

What was the lightship of the equivalent 40m SES and what was its deadweight?

Nothing wrong with quoting yourself...so long as you reference it properly