Flush Dinghy Outboard Motors While Cruising

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Manoeuvring toward the man overboard

The major problem is that multihulls are more affected by drift and windage at low speeds. A line towed astern may drag the person along, further weakening them and dragging them under. If they are in a sling or lifering get them to face backwards and shorten the line as soon as the person is attached.

Multihulls also lose way very quickly in any chop. Have motor power ready to help hold station.

Of all the seamanship safety techniques that should be practised the man overboard recovery is the most important. Every multihull differs in its speed, layout of equipment, manoeuvrability and drift. Practice on a regular basis the recovery of an object as quickly as possible. Time yourself and your crew.

Going aloft

The motion of a multihull mast has both advantages and disadvantages when it has to be climbed. At sea this is a potentially dangerous exercise. The mast, although remaining mainly upright, is prone to rapid movements in any direction as the multihull goes over waves.

Try to avoid going aloft. Have a spare halyard available for headsails. Regularly service blocks and sheaves so the risk of a wire halyard jumping a sheave and jamming is reduced.

If you have to go aloft prepare well first.

Multihull Seamanship Rule:

If you have to go aloft at sea, sail in a direction that has the least jarring motion.

Downwind is usually the best. Have all tools held by a lanyard. Secure the bosuns chair with D Shackles - not snap shackles. A safety harness and lifeline is needed as a back-up to the halyard. At every opportunity secure yourself to minimise any drop. Use a harness line with three attachment points so you are never unattached.

Pad your body well with jumpers, tracksuits and a helmet if you have one. Stuff numerous towels down your pants as the crutch is a prime injury point. Assist the person winching you aloft by hauling yourself where possible. Always hold on by two hands until at the level where you need to work. Wing masts make it difficult to grip the mast with your legs so wedge yourself firmly against any rigging and work quickly.

Before any offshore trip, do a run up the mast and check out the rig and your climbing gear.

If you have to go aloft and you are sailing solo, then plan the sequence carefully.

You will need a four-to-one purchase system and a bag on the bosuns chair to catch the tail of the rope as you climb. If you don't catch the tail, it will probably tangle somewhere and leave you dangling alone up the mast.

Mast steps

Mast steps are suitable for in harbour use only. They must be used in conjunction with a safety harness and line. The line should have three attachment points - you and two for the rig - so that you are never not connected.

Rotating masts

A rotating mast increases the rig efficiency. The mast presents less drag at sea and on the mooring and they can be amateur built. There are various grades of rotating rigs. At one end of the spectrum are the wing sails, a total aerofoil section with little or no soft sail. In the middle are wing masts, having a large fore and aft length. When these are scaled down to a size that is manageable in a gale (e.g. mast area less than 10 percent of the total sail area) then the term rotating mast is aptly applied.

The danger point of a rotating mast is the mast spanner. During a tack or gybe, if the spanner is not released, when it does fly free it may smash the ankle of someone standing adjacent.

If the mast spanner (the rotation control) is not released during a tack the sails may be damaged by the diamonds.

Always do a regular check on the attachment point of the three stays. This is an area of high load and should be heavily reinforced.

Multihull Seamanship Rule:

Check the rig by going aloft after each gale and before sailing offshore.

The leeward stay is often slack on a rotating rig. Have an elastic cord secured from each sidestay to the deck a few metres up so it does not whip about and increase the fatigue at the turnbuckle or wire attachment.

Multihull Seamanship Rule: Scan the rigging before each tack.

On a rotating rig there is a higher chance that running backstays will be caught around a spreader. Tacking will pull the spreader arm off. A glance skyward will reduce the risk of a problem. At night use a torch.

Rotating wing masts must be set up perfectly to work better than a fixed rig. There is more work required to get that improvement in performance. Because a rotating wing mast causes some increased windage and 'sailing' on moorings, they are not ideal for cruising multihulls.

Masthead tricolour lights

Masthead navigation lights do not work on a rotating rig. A solution is to fit two masthead tricolour lights, one for port tack and the other for starboard tack. After tacking, turn one off and the other on.

If you have your navigation lights mounted on the hulls, then an all round white light (designed for when at anchor) will signify your presence when at sea in an emergency. So will shining the spotlight on the sails and turning on all cabin lights. If all else fails try a white flare.

Conventional masts

Multihulls do not spill the wind when hit by a gust so the mast should be strong enough for the loads generated. Ensure your rigger is aware of this. Spreaders are needed if the stays are not separated wide on the beam. If the stays are spaced outboard on a rigid beam multihull (such as a bridgedeck catamaran) then spreaders can be done without. If the beam has any flexibility, then a series of short spreaders and a single cap shroud is a better arrangement. The mast then remains stiff if there is any movement in the beam.

Outboard motors

The light weight and long narrow hulls of a multihull are easily driven. For these reasons outboards are popular. The advantages of outboards on multihulls include ease of servicing access, lighter weight, manoeuvrability if steerable and initial cost. The disadvantages are exposure to the elements, weight at end of hulls, potential propeller ventilation, high fuel consumption and fuel flammability.

There are solutions to the above disadvantages. Mount the outboard as far forward as possible and reduce the exposure to spray by building protective barriers e.g. on a trimarans back beam alongside the central hull.

Fuel flammability is lessened if shut off valves are close to the motor and the tank and all fuel lines fire resistant. Ensure portable fuel tanks are not near gas bottles.

Position the outboard motor so it can be placed in the water and started without any crew member having to be substantially outside either the pushpit, guard rails or lifelines. An alternative if this is not possible is to only operate the outboard while wearing a safety harness.

Extra long shafts should be used to put the propeller as far under the water as possible. As the stern lifts clear of the water air may be sucked down to the propeller causing ventilation and loss of drive.

Ensure the motor and propeller are appropriate for the cruising speed and load of the multihull.

on the spot. The shallow bilges on a multihull even allow the mounting of outboards in an internal well. From these the outboard can be lifted clear when not in use and the underside of the vessel closed flush.

Mounting a single diesel in a catamaran can work by either positioning it in central nacelle (with a drop down outboard leg) or in one hull. The off-centre motor still works well although manoeuvrability requires practice. Twin, inboard diesels give excellent control in tight situations.

The drag from a permanently mounted propeller increases with increasing boat speed under sail. If you are serious about performance then incorporate a folding or feathering propeller. Either way some protection will need to be made so the propeller is not the first thing to hit bottom. A small skeg will make a difference.

Standard outboards have small, high speed propellers that produce very low thrust at yacht speeds. Special high thrust yacht auxiliary outboards are far superior although beware of some 'yacht' outboards which may not be ideal because of the ease with which the hulls are driven. Many motors are designed for heavy displacement vessels.

The ability of an outboard to pull up your multihull in reverse is dependent on the propeller function. Reverse exhausting propellers are more efficient in reverse than standard propellers.

Inboard motors

Diesel inboard motors are lighter and more powerful than in years past. They need only 30% of the fuel store of a two stroke petrol motor or 60% of a four stroke petrol motor for the same work. They have the advantage of being able to provide power for generators and refrigeration.


There are times when you may need to move your multihull under your own muscle. If you only have dinghy oars then rowing works. Expect to have a maximum rate of 1 -2 knots in very light conditions and only be able to maintain this for an hour or so per rower. Should your multihull be fitted with long rowing oars then these can be mounted on the sidestays and by walking backwards and forwards give an extra half knot. If only one sculling oar is on board then sculling off the back beam works also.

If you are in a race that allows man-driven power then a most efficient device is a propeller that is chain driven and geared onto a tandem bicycle. Paddling using small paddles is almost useless.

There are a number of seamanship features of multihulls that only become a concern in the racing environment. Every other chapter in this book is relevant to the racing multihull but none more so than capsize risk.

The majority of multihulls that capsize do so while racing in winds around 30 to 40 knots true. Squalls and rogue waves are the environmental triggers but there are a number of other factors involved depending on the sailing angle.

Racing downwind

The large roach, high aspect multihull mainsail has a lot of power and can cause the capsize of a multihull. This capsize effect is increased in fractional rigged multihulls due to them carrying relatively higher masts.

Multihull Seamanship Rule:

Reef the mainsail if surfing is occurring.

You will still surf under the power of the spinnaker. The spinnaker sheets should be able to be quickly released and power lost rapidly. Downwind the mainsail power is not as easily able to be dumped by releasing sheets or traveller.

The danger situation is when surfing and the bows bury into the wave ahead, stalling the multihull and dramatically increasing the apparent wind force.

Wind power (force) increases to the square of the wind speed. This means that going from a wind of 10 knots apparent to 30 knots apparent increases the force on the sails nine times.

When surfing, a multihulls top speed can be limited by the towing of a drogue or anchor warp and chain. It is possible to tow a drogue while sailing under mainsail and spinnaker. The right set-up can allow constant sailing at 15 - 20 knots and become rate-limiting by increasing the drag at higher speeds i.e. no excessive surfing and thus no bow burying.

When racing you need to know the designed displacement of your multihull. not overload it. An overloaded multihull usually needs more sail to get it up to speed and accelerates slower. Therefore when it stalls downwind the wind force is higher as recovery is slower.

Trim is an important feature in burying the bows. Weight should never be moved forward to increase the ability to surf. Weight forward increases the risk of nose-diving into the wave ahead. Altering trim may be illegal under race rules. A racing seamanship feature would be to have the multihull trimmed to surf with the weight as far aft as possible. Ensure any heavy loads are well secured. An outboard motor on the hull floor or loose water containers increase the capsize force if they slide forward.

Skipper and crew fatigue is higher in the racing situation. At all times a sharp crewman should be responsible for seamanship decisions.

Multihull Seamanship Rule: If you think a safety thought do it.

Remember that mistakes are often made toward the end of a watch or the end of a stint on the helm. A surprising number of accidents occur within sight of the finish line or home port.

Speed downwind is achieved through utilising the high apparent wind a multihull generates.

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