Motor sailing home from the race

When the wind dies, the motor starts. But Alan Lucas warns you can damage your engine with the wrong balance.

Sailing without the engine is one of life’s great satisfactions. Motor sailing, on the other hand, seems demeaning to both ship and crew. Nevertheless, when returning from a race motor sailing becomes inevitable for all but the engineless. It is a very real part of boat work, and one that can be improved upon by the right balance of machinery and canvas.

When motor sailing to windward, there are two distinct options. One is to carry all sail related to conditions and steer a typical course of around 45 degrees to the wind with the engine running as an ancillary force to maintain way and prevent the bow falling off during lulls. The other is to flatten the mainsail right in and lay a course of around 20 degrees to the wind, using the engine as the primary power source and the sail as little more than a steadying device.

At 45 degrees

At 45 degrees, the sails are set and trimmed exactly as for an engineless beat to windward, then hardened in just enough to reduce back winding as she motors through the lulls. Because engine power can periodically assume a secondary role to sail power in this type of motor sailing, a folding propeller may try to automatically fold whilst a variable-pitch type can be purposely coarsened. In the absence of these responses, short-term gearbox rattle and long-term cylinder glazing could result. If a fixed-blade propeller is involved, these ailments are almost guaranteed.

Gearbox rattle is a common phenomenon that happens when sailing speed reaches engine speed. Power transfer in the gearbox is negated, causing the meshed cogs to rattle against each other. In the absence of automatic or controlled responses through an articulated prop – or if a fixed-blade prop is involved – this can be tamed by increasing engine revolutions until the propeller regains dominance over the sails. The other problem – that of cylinder glazing - will be self-correcting by loading the engine because glazing is a child of under-loading over long periods of time.

Poor lubrication is another aspect of motor sailing that must be considered. Unlike the engines of racing cars hurtling around a track, or planes doing aerobatics, some diesel sumps do not have enough baffles to prevent low sump oil swirling away from critical pump inlets. This means that a motor-sailing vessel, heeled excessively for long periods of time, may cause the engine’s lubrication system to periodically starve. It is imperative to keep the sump filled to the dipstick’s top mark.    

At 20 degrees

When pinched up to around 20 degrees to the wind, an engine rarely suffers from any of the above maladies because it typically runs at full cruising revolutions with less angle of heel while the sail acts more as a steadying force than a driving force. In this instance, it is sheeted in as flat as possible, even to the extent of cocking the clew slightly to windward to prevent luffing. This firms the helm and allows the engine to be driven at cruising speed without being out-done by the sail.  

In this ‘strapped-in’ form of motor sailing, boomed sails such as mains and mizzens set the flattest, the mainsail being the obvious choice for a single-sail rig. But be aware that enormous strains are placed on the sail, potentially ripping older cloth and seams and even destroying track-slides. Motor sailing in this way demands a strong, healthy sail. If its strength is doubtful, lay the course off a little and ease the sheet to reduce strain.  

Regardless of the exact course and power-sharing balance between sails and engine, the steadying effect of a sail is always at its best when close-hauled, this being the reach most typical for motor sailing. As the vessel falls off the wind, this steadying influence diminishes until, when squared away, it disappears altogether. There are those who declare a mainsail kept strapped in flat dampens rolling when squared away, but if they are right, it is at the cost of considerable wear and tear plus the unbearable sound of the sail whip-cracking to the boat’s rolling. This has to be an individual’s decision, but I again warn that an old sail may not survive such torture.

Abaft the beam

Once the wind is abaft the beam, most of us are happy to either ghost along or furl the sails and revert to engine only. However, if the apparent wind continues to assist without inducing propeller over-run, then motor sailing remains an option. A useful trick is to keep the mainsail as full as possible and the headsail sheeted flat, to discourage back-winding and rounding up during gusts.

Twin-engine catamarans can run just their leeward engine to great advantage when motor sailing on a reach because, in the absence of the windward engine, more throttle can be applied to negate gearbox rattle whilst steering is more positive thanks to the leeward engine’s tendency to drive the vessel upwind. Being such easily driven craft, a multi-hull’s engines are likely to be shut down off the wind, although in beam winds many owners keep the engines running to reduce the time spent in uncomfortable ‘wave walking’ conditions.    

A motoring yacht is a motorboat

When a sailing vessel is using her engine, whether sails are set or not, she is defined as a motorboat and is obligated to observe the rules accordingly. When motor sailing, she should hoist an inverted black triangle to leave other vessels in no doubt as to her status. This shape should be set somewhere within the forward triangle or, if a headsail is set, wherever it enjoys prominence. Marine authorities rarely worry about policing this nicety, but without it you are automatically in the wrong in the event of a collision.

Today’s racing yacht, with its skiff-like hull and deep fin keel, is much stiffer and livelier than traditional hulls, making it a great candidate for motor sailing when returning from a race if only for the faster average speed in fickle winds. It is always a regrettable moment when the peace is shattered by the iron topsail, but the fact is it tightens the course and gets you home earlier and more comfortably, to say nothing of giving the engine a healthy work-out and the batteries a much needed top-up.