How it’s made: rough sea in the stern

Dolceriva 48, this open is the latest Riva speedboat
27 December 2019
Mr Evinrude and the first outboard engine, born because of an ice cream
28 December 2019
mare

 

rough seas from the stern

The rough sea is always a problem and if the rough sea is in the stern. And you can’t always decide to tackle it in the best conditions for the boat and the crew. That’s why you need to be ready to deal with the situation when instead of coming from the bow or from the mascone, the wave comes from behind. In this case it initially strikes the stern sections, the most voluminous.
Again, the trim tabs help us. The appendages attached to the transom not only serve to get into the glide faster or to save fuel, but are one of the most important (and often unknown) accessories to improve the operation of a motor boat. And it doesn’t matter if it’s a fast sports boat or a heavier cruiser. So here’s how to act to deal with the sea in the stern in total safety.

 

With the sea moved in the stern

The wave motion coming from the stern tends to lift the stern and make the right side of the bow sink too much. In these conditions, where the forward part is very immersed, the efficiency of the rudders is low and steering a boat when descending from a ridge becomes sometimes difficult. Raising the trim tabs completely, and then squeezing the stern down, can mitigate this effect. It is also essential to keep the boat on course to optimise the efficiency of the rudder blades.

The boat must be faster than the waves that arrive

The rough sea in the stern is undoubtedly the most difficult situation to manage. Of course, you would think that it would be sufficient to reverse the regulations that are used with the sea in the bow. No, because there is no single criterion to be applied to all boats. If your destination forces you to face the stern waves, the best thing to do is to zigzag, following a route that allows you to face them in the garden rather than directed on the mirror. Generally, the bow should be lightened (perhaps by draining any water tank, often positioned from half the hull forward).

Outboard trim and trim tabs should be adjusted to ensure that, when the boat descends into the cable, the bow is raised and thus prevent the wave from entering the cockpit. Finding the right balance is difficult and changes depending on the type of wave: the steeper the crest, the more difficult it is to manage the situation. Usually it is necessary to act alternately on the trim and the trim tabs to get to reduce the pitch of the hull.

 

aft sea rough sea from the stern

 

The importance of speed

A fundamental function to be able to steer correctly in these conditions is speed: the pace must be sufficient to keep your boat on course so that you never lose control. Why? Simple, the effectiveness of the rudders depends precisely on the difference between the speed of the boat and that of the wave; if you reduce your speed too much, the thrust of the waves would risk having the upper hand over the governability and would cause some “beautiful” yaw (ie the sudden rotation of the boat on its axis that generates a strong heeling, resulting in a nice scare).

 

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