Article - application of "Froude Number" analysing a boat I worked on

Article - application of "Froude Number" analysing a boat I worked on.

"Hydrodynamics, Froude number and a clever vessel design"

I knew this in late March 2022, but wrote the article on New Year's Eve when had a virus and was alone until it passed.

A non-technical friend said "This is >>>*not*<<< trivial!" and helped me straighten-out the language to try to make the story accessible.

What they have achieved is astonishing.

These boats are about the size they need to be at about 25m length. But has a speed up 26kt - which should be infeasible - they've "ripped-up a rule-book".

26kt is the domain of significant-sized military vessels and hundred-of-metres long streamlined container-ships carrying high-value time-sensitive fully-manufactured cargoes at premium speed.

The boats are no panacea - they have a very limited application (eg. their cargo capacity is minimal for their size). But for this one application of servicing offshore wind-farms they are pretty-much a panacea. A crucial advantage is they ride the waves by hardly moving at all, which makes transfer over the bow to wind-turbine towers do-able in quite fearsome seas.

Regards, Rich Smith

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The RMS Mauretania needed to be very narrow and 240 meters long to cross the Atlantic at 26 kts, a record she held for 20 years. Although ~100 feet longer, RMS Titanic was designed for less extravagant fuel consumption and did 22 kts.

meter waterline length, 40 kt speed, but it didn't protect her from 400 kt aircraft.

In a print article about a racing boat attempt to set the Atlantic crossing record they joked that they might still need a rear view mirror to show an overtaking USN aircraft carrier.

The 5 meter (16') long Hobie Cat sailboat can reach around 23~24 kts.

The old-time clipper ship speed record is 22 kts, and fast sailing ships may return:

<snip>

I remember hearing of hybrid sailing cargo ships coming soon years ago. Seems like a good idea to me but doesn't seem to gain much traction...

We have a car ferry not too far away in Muskegon, MI that claims it can hit 34kn (39mph):

Wiki mentions long slender hulls can exceed the traditional hull speed see here

. I guess that's why the ship can go as fast as it does.

Leon Fisk snipped-for-privacy@gmail.invalid on Sat, 7 Jan 2023 15:10:52 -0400 typed in rec.crafts.metalworking the following:

The issue remains as it always has: schedules, and "time sensitive" cargos. If you're moving bulk cargo, it can make sense. But with "just in time" global supply chains, "it positively absolutely has to be there in two months". Like wise, as cool as it might be to take a cruise on a sailing ship, there is the small issue of "T be back at work, I have to catch a flight in 10 days. Arriving on the next tide doesn't cut it." (I had a friend who took Amtrak to Disneyland, and flew back. The train was delayed, so 'half' the first day at Disneyland was lost because the train was late. If there is a next time, she'll fly down, and take the train back. Amtrak is by and large about the trip, more than getting there.)

That's also escaping the Froude hull-speed concept.

(mps2knot (v-from-froude-number 0.4 9.81 58.40) ;; 9.574165237763552 ;; m/s ) ;; 18.610688367142973 ;; kt

It was exciting for me to work out this, but it is obvious - make a catamaran with largely submerged hulls and you start with a new hydrodynamic "rulle-book".

Leon Fisk snipped-for-privacy@gmail.invalid on Sat, 7 Jan 2023 15:10:52 -0400 typed in rec.crafts.metalworking the following:

The issue remains as it always has: schedules, and "time sensitive" cargos. If you're moving bulk cargo, it can make sense. But with "just in time" global supply chains, "it positively absolutely has to be there in two months". Like wise, as cool as it might be to take a cruise on a sailing ship, there is the small issue of "T be back at work, I have to catch a flight in 10 days. Arriving on the next tide doesn't cut it." (I had a friend who took Amtrak to Disneyland, and flew back. The train was delayed, so 'half' the first day at Disneyland was lost because the train was late. If there is a next time, she'll fly down, and take the train back. Amtrak is by and large about the trip, more than getting there.)

That's also escaping the Froude hull-speed concept.

(mps2knot (v-from-froude-number 0.4 9.81 58.40) ;; 9.574165237763552 ;; m/s ) ;; 18.610688367142973 ;; kt

It was exciting for me to work out this, but it is obvious - make a catamaran with largely submerged hulls and you start with a new hydrodynamic "rulle-book".

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These creatures know the rules:

I was just reading about what is the fastest animal. Apparently the record of 242 MPH is shared by a sky diver and his pet peregrine.

"Jim Wilkins" snipped-for-privacy@gmail.com on Sat, 7 Jan 2023 17:27:53 -0500 typed in rec.crafts.metalworking the following:

Ufda. There were reasons one didn't sail in winter if one could avoid it.

Fully submerged and that is a completely new hydrodynamic "rule book".

Submarines - military application - they go to enormous lengths to optimise form, I gather. Liquid helium test tanks for scale models, etc.

Fish - well, didn't know of these. They must be super-efficient. Puts our "swimming" in perspective. Feels good though on a warm summer's day... :-)

Everyone - I have to accept that I learned a lot and contributed little writing that article.

You've caused me to look-around, recalling the Irish Sea service, and with one thing and another I come to Incat

I think I have handled cut Ali profiles for ships which have come from Australia...

Seems there's been quite a lot of twin-hulls around slicing the water efficiently since at minimum the 1990's.

Regards,

"Jim Wilk> Le>

Fish - well, didn't know of these. They must be super-efficient. Puts our "swimming" in perspective. Feels good though on a warm summer's day... :-)

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In the 1600's Samuel Pepys described a proper underwater hull shape as having the form of a codfish.

Ufda. There were reasons one didn't sail in winter if one could avoid it. pyotr filipivich

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There are reasons other New Englanders call Maine residents "Mainiacs".

<snip> <snip>

I quickly learned that taking very busy time constrained vacations wasn't for me. Always planned an extra day to both start and end. Didn't try to fit a whole bunch of must sees together...

The job hassle was knowing there would be a bunch of stuff waiting for me when I got back. Because there was nobody else that could do them while I was away. Which was better than having to smooth over the ones where they did send someone who screwed up...

I never really thought that I was that good but rather that the others didn't care or try that hard. Pay was the same either way...

You eloquently describe in few words the entirety of how things do and don't work.

There's those who believe systems deliver (many - from "managerialists" to "communists" they all share that core belief) There's those who believe individuals deliver (not many, and you'd find them here :-) )

Best wishes everyone,

There's those who believe systems deliver (many - from "managerialists" to "communists" they all share that core belief) There's those who believe individuals deliver (not many, and you'd find them here :-) )

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After my father was chosen for a high level position in NH State government he took management classes and told me what he'd learned. One was that many skills and tasks could be treated as commodities, like hiring a temporary plumber or welder or tax preparer. The unstated assumption is that the hiring person can distinguish good from bad candidates for a job they can't do themselves. We cynically say those who can, do, those who can't, teach.

He had come up the hard way, from barefoot farm boy to cotton mill worker to the mill's cost accountant, and during WW2 was pushed hard into Officer Candidate School and became a Company Commander in the Air Corps, so he knew better from his own experience. But that was the accepted wisdom.

I wonder how business school professors would like being treated as equally paid interchangeable commodities, with their individual accomplishments (or lack of them) ignored, the way proponents of social equity demand of students. The socialists have no rational answer to why Asians do so much better here than other historically disadvantaged minorities.

Social pressure to not achieve more than and embarrass your peers: As an Army sergeant with a college degree I had to learn to "code switch" to the level of the troops. wasn't really aware of it until I was translating directions for friends from a German girl who asked why I mispronounced "Mannheim" in English but not German.

Everything I see from the Left appears based only on wanting to feel superior without the effort. When they have the opportunity to actually accomplish what they demand they change the subject instead. Do you see them drying their laundry on clotheslines to reduce their fossil fuel consumption? Are they teaching legal immigrants English or helping the homeless gain life skills?

The founding tenet of "management".

The founding tenet of "management".

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So they go with what they know and select the smoothest talker, repeatedly, until they happen on one who can also do the job. I spent 9 years doing the work of two techs because they couldn't find another with my combination of experience and abilities. Some of the most skilled artisans I've known were the least articulate.