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Gross engine-compartment volume is then:
8.2 ft. long x 10.6 ft. beam x 4.45 ft. average height = 387 cu.ft.
We need to subtract permanently installed items such as:
Engines
Tanks: fuel, water, etc.
Generators
Batteries
Accessory equipment and machinery like water systems, air/conditioning units, compressors, etc.
We
cannot
subtract items that may be stowed in the space but removed, such as:
Docking gear: fenders, line, etc.
Anchors and line
Stowed furniture or food
Anything else that may be removed from the compartment
The volume of the permanently installed items is:
5 batteries x 0.5 cu.ft./battery
2.5 cu.ft.
2 large V-8 engines x 5.5 cu.ft./engine
11.0 cu.ft.
340 gal. fuel x 0.134
45.5 cu.ft.
12 gal. calorifier x 0.134
1.6 cu.ft.
20 gal. black water x 0.134
2.7 cu.ft.
Other machinery
4.0 cu.ft.
Total
67.3 cu.ft.
Net engine compartment volume is then:
387 cu.ft. – 67.3 cu.ft. = 319.7 net cu.ft.
Powered Ventilation is Required
Every gasoline-engine boat
must
be ventilated by a powered exhaust blower. These
must
be ignition-protected, (non-
sparking) exhaust vent blowers. The rate of flow in CFM (cubic feet per minute) is determined based on net compartme
volume based on the following table:
NOTE 1: The net compartment volume includes all the volume of any compartment that opens into the compartment th
contains the engine, unless the area the engine-compartment connects to is “open to the atmosphere,” as described
above; however, long, narrow compartments need to have openings at both ends or along much of the sides to qualify
open to the atmosphere.
NOTE 2: “The 2% Rule:” Adjacent compartments do
not
need to be included in the net compartment volume if the open
ings in the bulkhead or panel between the compartments are less than 2% of the total surface area of the bulkhead or
panel.
For our
Rocket X-32
the gasoline blower requirements are as follows:
Gasoline Blower Requirement Table (CFR 183.610)
Column 1
Column 2
Column 3
Net Compartment Volume (V)
Rated Blower Capacity (Fr)
Blower System 0utput (Fo)
Cu.Ft
.
CFM
CFM
Less than 34
Fr = 50
Fo = 20
34 to 100
Fr = 1.5V
Fo = 0.6V
Over 100
Fr = (V÷2) + 100
Fo = 0.2V + 40
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