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At random: "He is the Submarine Sailor who served in silence, but in his silence, has heard the laughter of future generations.” -- Glenn Harris
Science Stuff
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GaryKC
Posted 2018-06-24 8:07 PM (#89547)


COMSUBBBS

Posts: 3660

Location: Kansas City Missouri
Subject: Science Stuff

https://www.onr.navy.mil/en/Media-Center/Press-Releases/2018/Navy-Developing-Ship-Coatings

https://www.youtube.com/watch?v=JeEV7x3iuSQ
rover177
Posted 2018-06-25 2:39 PM (#89550 - in reply to #89547)
Master and Commander

Posts: 1576

Location: Wollongong, NSW
Subject: RE: Science Stuff

Only problem with these sorts of coatings is that they are easily damaged by contact with a foreign object - think of a pile or fender. The drag resistance at that damaged area is far more out of proportion than is the case for normal drag on a hull. My father worked on this type of stuff (and alloys) for advanced aircraft design.
fortyrod
Posted 2018-06-25 3:00 PM (#89551 - in reply to #89550)
Great Sage of the Sea

Posts: 848

Subject: RE: Science Stuff

rover177 - 2018-06-25 2:39 PM
The drag resistance at that damaged area is far more out of proportion than is the case for normal drag on a hull.


I do not comprehend or understand what your saying. Can you elaborate (keep it simple, I'm a snipe)
rover177
Posted 2018-06-26 2:14 PM (#89558 - in reply to #89547)
Master and Commander

Posts: 1576

Location: Wollongong, NSW
Subject: RE: Science Stuff

The water flow (air flow - aircraft) over a surface will have drag from friction. That drag can cause heat and a loss of speed - more energy is required to travel at the same speed.

Anything done to change that airflow - intentional with aircraft flaps for example, will cause a change in performance. Small boat hulls are often designed for planing purposes - less surface area in contact with the water.

Think of a ship when it turns, the rudder is stuck out to one side and the water flow changes. With a smooth hull, the flow is uniform. If the hull surface is damaged, little eddies (circular whirls) will occur and this drag will affect the performance and at the same time, produce "detectable" flow noises; think of cavitation as an extreme.

On a pure hull, the coatings can be very worthwhile but the cost in money and time to keep the flow "pure," is generally not worth the effort.
fortyrod
Posted 2018-06-26 4:01 PM (#89561 - in reply to #89547)
Great Sage of the Sea

Posts: 848

Subject: RE: Science Stuff

Aha, got it. Thanks
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