Site preparation
3-10 Chapter 3: Installation 99-145912-A
Mast length and diameter
The placement of the ADU must ensure a rigid structural connection to
the hull or structure of the ship. Parts of the ship with heavy resonant
vibrations are not suitable places for the ADU. A small platform or short
mast shall provide rigid support for the ADU fastening bolts and a rigid
interface to the ship.
If it is necessary to use a tall mast, you must stabilise the mast with
bracing. Note that the design values given below depend on rigid ADU-
ship interfaces. The cross-sectional properties and the corresponding
maximum free length give a natural frequency close to 30 Hz. Shorten
the mast length as much as possible to obtain higher frequencies.
Preferably, mount stays or wires to stabilize the mast further.
The tables in the next sections give suggested design values for the free
mast length.
The following tables show the minimum dimensions for a ADU mast
with and without stays or wires. Note that the values are only guidelines
Figure 3-10: Free mast length and 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-
16.
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.
To Next Page
Loading...
Need help?
General
