Lagoon Sail Drive Placment

[PaulinOz]

Quote "Steering cable and pulley routing are not complex, certainly less complex than a Lagoon flybridge."

The steering cables to the fly bridge wheel just go vertical for an extra meter compared to the non-fly bridge version eg L400 /L421 etc. No increase in complexity at all.

As you say though "It's all a trade off isn't it?"

[arsenelupiga]

rudders behind propeller is safety issue.

In rough large seas, if boat slides in reverse on large wave, rudders normally suffer. If propellers behind rudders, twisted rudders disable propellers and therefore engines, and one has only 'mayday' option left.

[CatNewBee]

I don't think so. Even with no rudder you can steer with the two engines pretty well.

When docking a cat, you would turn off the autopilot, fix the rudder straight ahead with the nut on the wheel and steer only by the engines like a caterpillar / tank. You do not use the rudder for this purpose.

When sailing, the folding props just go out of the way and the vessel is a sail boat. This is most of the time the case. When you are motoring, you usually not reverse over the ocean, and in most cases you do not turn - so the propellers are not an issue. Besides that, you do it normally only with one engine for fuel economy.

Even in large seas, when you need both engines, you would go forward and not reverse over the waves.

[CatNewBee]

The main danger of the sail drive aft is, the props are very close to the bathing ladder and you can be sucked in into the propeller easily - especially in MOB situations if you do not shut the engines / the gear properly. A position behind the rudder would save your life.

Also they are more exposed to serious damages when backing up and hitting something.

[arsenelupiga]

Originally Posted by CatNewBee

I don't think so. Even with no rudder you can steer with the two engines pretty well.

When docking a cat, you would turn off the autopilot, fix the rudder straight ahead with the nut on the wheel and steer only by the engines like a caterpillar / tank. You do not use the rudder for this purpose.

When sailing, the folding props just go out of the way and the vessel is a sail boat. This is most of the time the case. When you are motoring, you usually not reverse over the ocean, and in most cases you do not turn - so the propellers are not an issue. Besides that, you do it normally only with one engine for fuel economy.

Even in large seas, when you need both engines, you would go forward and not reverse over the waves.

it is a problem when sailing in large seas and boat slides back on back of a wave. Rudders twist towards propellers and if unlucky disable propellers. So you do not have rudders and engines to move. This actually happened and there is a thread on it in CF. Crew was luckily saved by large ship.

[Factor]

An oft overlooked benefit of sail drives in front of rudders is the ability to bring the boat stern or bow to the dock, when departing a berth with a boat of this configuration, I end with, in the case of a boat that is stern to, a stern line only and engines idle forward to hold the boat, simply by turning the wheel away from the dock I can bring the stern to the dock to aid boarding etc or get me closer to the dock cleat.

[tuskie]

Much discussion about reversing with saildrives aft of rudders. Most motoring time is usually spent in forward gear where the aft saildrive is more efficient as the propellor thrust is not impeded by a closely spaced rudder. Not only is the aft saildrive position more efficient in forward thrust but it allows fitment of either folding or feathering propellors.

Lagoon could have easily placed the rudders aft of saildrives if they had chosen to do so, without moving the engine compartment bulkhead and reducing accommodation. There are plenty of examples of other designs where this has been done. On some of these designs, folding propellors cannot be used as they would interfere with the rudder.

[Tornadosailing]

Originally Posted by tuskie

Much discussion about reversing with saildrives aft of rudders. Most motoring time is usually spent in forward gear where the aft saildrive is more efficient as the propellor thrust is not impeded by a closely spaced rudder. Not only is the aft saildrive position more efficient in forward thrust but it allows fitment of either folding or feathering propellors.

Lagoon could have easily placed the rudders aft of saildrives if they had chosen to do so, without moving the engine compartment bulkhead and reducing accommodation. There are plenty of examples of other designs where this has been done. On some of these designs, folding propellors cannot be used as they would interfere with the rudder.

I can attest to this. I fitted Brunton Autoprops on my FP with rudders behind. It's apparently a freak coincidence that this particular FP model and Brunton Autoprops don't get along if you put the motors in neutral when sailing. The props don't hit the rudders, but they do create such a disturbance when freewheeling that the rudders become ineffective and the boat rounds up.