Too stiff to patrol fisheries

#21

I read it thus:

it was decided to drop the stabilizers to save weight and [thereby] reduce hull resistance

It may be only a few tons, but a 0.1% displacement increase is a big deal in a life cycle analysis. The mass of the stabilizers would also detract directly from how much fuel can be carried for a given freeboard.

The article could use a bit of clarity and detail…

#22

With regards to the motion of a stiff vessel, it’s not just big, quick rolls. Even in good weather the motion will throw the crew off balance. When I was on that cutter in Alaska my shins were always banged up from being thrown into things.

I’ve never heard of it till just now but it see in seakeeing it measured by “motion induced interruptions”, how many times a crew member is thrown off balance, trips or slips because of vessel motion.

This is from an article about the “Hero Class” patrol vessel:

The ergonomics of the kitchens are “compromised” and facilities need to be rearranged, the government has told potential contractors.

Ben Nelms/Bloomberg Ben Nelms/Bloomberg

The modifications will allow for safe cooking and will accommodate sudden movements of the vessels while conducting operations, industry officials have been told.

MOTION INDUCED INTERRUPTIONS AS SHIP OPERABILITY CRITERIA

An important goal of operability research is the development of quantitative seakeeping criteria to permit the effects of ship motions on operations to be assessed. This paper examines the problem of developing seakeeping criteria for deck operations. The lateral force estimator is generalized to permit frequency-domain computation of the incidence of personnel losing balance in the presence of non-zero vertical acceleration. The inadequacy of roll- angle based seakeeping criteria for deck operations is shown. Other possible criteria for deck operations are discussed, and it is concluded that a limit on the number of motion-induced interruptions during deck operations is most suitable, since it is platform- independent, and may now be computed in the frequency domain.

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#23

That could be. What I thought of was when I read that was the ship correlation factor. This from Reed’s Marine Architecture for Marine Engineers’ chapter on resistance:

The model is tested without appendages such as rudder and bilge keels. An allowance must therefore be made for these appendages and also the general disturbance of the water at sea compared with tank conditions. This allowance is known as the ship correlation factor (SCF)

They give the formula: effective power = resistance * speed * SCF, and use 1.15 as a value for SCF in the examples, so these things, I suppose, must typically add about 15% to the power requirement.

for sure. Its just the normal news for the normals to read.

#25

in the pic it looks like it could be uncomfortable, kinda small too. coast wise voyages along the shelf … the ship always rolls. anyway, the rolling will get to you. we were 3 weeks one time in the spring along the west usa coast. the crew were getting grumpy. not good. i was in the bottom so didn’t notice it as much. they should just sell them and let some mariners choose the next platform! refit with ‘fins’ … in the N. Atlantic? … IN WINTER!?! i’d be afraid they’d get sheered off. … well, noaa did about the same thing with the dyson class. The Navy wasn’t consulted, it was NOAA personel that decided : galley way up fwd. Ladders over bulkheads instead of water tight doors, … etc.