Training, Installation & Service Manual - Livewire Connections Ltd

Site preparation
3.2.6.2 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. It is recommended to shorten the mast length as much as
possible to obtain higher frequencies. Preferably, mount stays or
wires to stabilize the mast further.
Free mast length (m)
Figure 3-10: Free mast length and bracing for a tall mast
Note
Make sure that there is free space below the drain tube. Read
also Condensation and water intrusion on page 3-17.
The tables in the next sections give some suggested design values
for the free mast length.
Note
The tables list the values for steel masts. For aluminium masts,
the free mast length is reduced to 75% of the values for steel.
Note
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.
3-10 Chapter 3: Installation 98-133966-E2