Naval Ship Technical Manual Chapter 81

Question 1

What type of fouling?

Normally slime and grass. Slime consists of bacteria, fungi, protozoa, Algae; commonly present within a half hour of wetting the surface, can be felt by hand within an hour. Grass is a form of multicellular Green and brown algae, forms most heavily near the waterline, less evident as depth increases and color changes from green to brown.

Answer 1

Softfouling

NSTM CH 81 1.2

Question 2

What type of fouling?

Normally barnacles (acorn) and tube worms (serpulids). Barnacles have conical hard shells with jagged tops. Tube worms form intertwined tubes lying along or projecting out from the hull.

Answer 2

Hard fouling

NSTM CH 81 1.2

Question 3

What term?

A result of an active cathodic protection system is deposits of magnesium and calcium carbonate on bare metal surfaces. The bare nickel aluminum bronze surfaces of a propulsor are highly susceptible to a uniform accumulation of deposits. Thickness will depend upon Time from last cleaning and functionality of the cathodic protection system.

Answer 3

Calcareous deposits

NSTM CH 81 1.2

Question 4

What type of fouling?

In advanced stages, mature barnacles and tube worms maybe present along with calcareous bivalve organisms such as musssels or oysters, hydroids with calcareous cellular structure (coral or anemones), and tunicates (sea squirts).

Answer 4

Composite fouling

NSTM CH 81 1.2

Question 5

Fouling on the propeller can account for as much as?

Answer 5

Fouling on the propeller can account for as much as 50% of the increased energy demand associated with a light to moderately fouled hull

(NSTM CH 81 1.3)