Site preparation
3-10 Chapter 3: Installation 98-141779-G
The tables in the next sections give suggested design values for the free mast length.
The following tables show the minimum dimensions for an ADU mast with and without
stays or wires. Note that the values are only guidelines - always consider the environment
and characteristics of the ship before deciding on the mast dimensions.
Figure 3-10: Free mast length and example bracing for a tall mast
Make sure that there is free space below the drain tube. See also Condensation,
water intrusion and deposits on page 3-15.
The tables list the values for steel masts. For aluminium masts, the free mast
length is reduced to 75% of the values for steel.
Bracing and rigid masts can still not prevent vertical vibration if the mast is
attached to a deck plate that is not rigid. Make every effort to mount the mast on
a surface that is well supported by ribs. If this is not possible, provide extra deck
plate propping.
Mast without
braces
Max. free mast
length (steel)
Outer
Diameter
Wall
Thickness (mm)
Weight
(kg/m)
0.4
a
m (1.3 ft)
a. The height of 0.4 m is not recommended to be used as it will make access through
the ADU’s service hatch difficult.
200 mm (8 in) 5 mm (0.2 in) 24.0
0.6 m (2 ft) 220 mm (9 in) 5 mm (0.2 in) 26.5
0.8 m (2.6 ft) 250 mm (10 in) 5 mm (0.2 in) 30.2
1 m (3.3 ft) 270 mm (11 in) 5 mm (0.2 in) 32.7
Table 3-2: Mast dimensions without braces
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