Raymarine LIGHTHOUSE 4, Operation Instructions Manual

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• Maximum vessel draft — the distance from the waterline to the lowest
point of your vessel’s hull/keel.
• Safety margin — an adequate clearance below the hull/keel to allow for
draft variation and changes in water or bottom conditions.
1. Waterline
2. Maximum vessel draft
3.
Safety margin
4. [Minimum safe depth]
Minimum safe depth calculation guidance
The information below is provided for guidance only and is not exhaustive.
Some influencing factors can be unique to certain vessels and/or areas of
water and may not be listed below. You should ensure you account for ALL
factors that apply to your current situation when making calculations.
Some of the factors that can influence how much a vessel draws are shown
below:
•
Vessel displacement (weight) — A vessel’s draft will increase when it is
fully laden when compared with its unladen displacement.
• Water type — A vessel’s draft will increase by approximately 2% to 3% in
fresh water compared to seawater.
Some of the factors that should be taken into account when calculating
a safety margin are:
•
Vessel maneuvering characteristics — A vessel’s draft increases due
to squat, trim, roll, pitch and heave.
• Chart accuracy — The electronic chart depth may not be accurate or the
true depth may have changed since the last survey.
• Weather conditions — High air pressure, and prevailing wind strength
and direction can affect wave height.
Minimum safe height
During the start up wizard you can set a minimum safe height for your vessel.
The minimum safe height can also be added or changed at anytime from the
[Boat details] setting menu: [Homescreen > Settings > Boat details] .
A suitable value for minimum safe height can be established by identifying
your vessel’s maximum height from the waterline and adding a safety margin.
• Maximum vessel height — the distance from the waterline to the highest
point of your vessel e.g.: top of the mast.
• Safety margin — an adequate clearance above your mast to allow for
height variation.
1. Safety margin
Getting started
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