Trim Of The Boat Roll (Transverse Movement) - Ockelbo B21 CAB Owner's Manual

Trim when running at speeds above planing:
 When the boat is running at speeds above planing, the trim also needs to be
adjusted. As speed, direction, load, wind or wave condition changes, new
adjustments may be needed.
 Use the trim up, to lift the bow up slowly without change of throttle position.
Follow the log to notice for how long the speed is increasing. When the speed is
not increasing anymore, the trim is in the most fuel-economic position. Then
lower the bow slightly to avoid the propeller loose grip.
 In head sea (boat running against waves), you may have to use the trim to lower
the bow down to soften the vertical motions but be careful not to lower it too
much due to the risk of a bow to plunge into waves.
 In the following sea, you may instead need to raise bow up to prevent nose-
diving.
 A safe ride is always more important than maximising speed/fuel consumption, so
always trim for safety first.
Trim when lowering speed to below planing:
 When you reduce speed below planing, or stop the boat completely, the trim
should again be adjusted to trim down position. This improves manoeuvrability
and makes the boat ready to accelerate fast next time.

2.6.2 Trim of the boat roll (transverse movement)

The boat is equipped with 2 Trim Tabs and a control unit for these (See also chapter
4.7). Trim tabs can help you control and adjust the boat's roll (transverse movement).
The boat's roll is affected by wind direction, wave direction, speed and how the boat is
loaded. Heavy crosswind usually affects the boat the most.
By pushing down the trim tabs in the water, the hull resistance increases, and the bow is
pushed downwards. By just pushing down one of the trim tabs, the boat can roll in the
desired direction. The trim tab is used mostly to compensate for crosswind or unevenly
distributed load, and thus avoid the boat tilting sideways.
The trim tabs can also be used to press down the bow in the water (the boat's attack
angle), but usually, it is faster and sufficient to use the engine trim for this (see chapter
2.6.1). However, the trim tabs can be used to adjust the angle of attack on a longer
journey under the same conditions, e.g. If you have much cargo in the bow. Fuel
consumption may then be lower than using the engine trim. A rule of thumb is "big
adjustments or long time with trim tabs, small adjustments or short time with the engine
trim".
Learning to handle trim tabs in a good way requires some practice, so if you are unsure,
you should ask someone who has experience for help. Proper trimming is essential for a
safe, comfortable and fuel-efficient ride. Always proceed from a neutral position (trim
tabs postponed) and then adjust a little at a time until the correct effect is reached.
2. OPERATING THE BOAT__PAGE 17