When France Helices installs an SDS on a vessel, we always include operator training as paart of the package. Operating a vessel at 30 knots is a very different skillset than operating a vessel at over 50 knots.

Why?

Well, there are many reasons, but one of the things that often confuses crews new to the SDS is the concept of drive trim. The trim of the drives is critical when operating the SDS. Remember in an earlier article that we stated that one of the functions of surface drives is to provide lift.

The SDS literally lifts the stern of the vessel out of the water, thus allowing much easier planning of the vessel, reduced hull resistance, and hence, greater speed. The greater the trim angle of the drive, the greater the amount of lift. Likewise, a reduced trim angle, or trim fully up, results in less lift. Of course, the complication arisesin that how much lift is enough? Too much lift for too long can result in the vessel “porpoising”, or trying to dive. Too little, and the vessel struggles to plane. Autotrim uses a computer and sensors to automatically adjust the drive trim: No user input is necessary.

We can always train vessel crews how to use the trim. Indeed, if becomes second nature, given adequate practice.

However, late last year we started offering computerized auto-trim as a featured option on all SDS models: Particularly on commercial or recreational vessels. Very seldom are government entities interested in this feature. Why? The answer is that most government agencies prefer manual control, since fewer computers mean reduced failures.

Of course, we build adequate redundancy into the autotrim. However, for this reason, we continue to offer both automated, and manual, trim controls per the customer’s requirements. Both will function for many trouble-free years.

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