What is Sail Drive? I am looking for a new boat and in the past have had Hunters with a Yanmar with a normal shaft etc. I see some boats have "sail drive", even with a Yanmar. Hate to be ignorant on this point, and hope to no longer be so, once one of you kind people explain the diference to me. Also any advantages/disadvantages?
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A sail drive looks like..........
..... an outdrive on a power boat. There is no external shaft,cutlass bearing or strut. The "outdrive" simply hangs down from the bottom of the boat. I suppose that the advantages are no shaft, cutlass bearing, or strut. Less vibration, and, a more direct route for the power to get to the prop. Jeff
..... an outdrive on a power boat. There is no external shaft,cutlass bearing or strut. The "outdrive" simply hangs down from the bottom of the boat. I suppose that the advantages are no shaft, cutlass bearing, or strut. Less vibration, and, a more direct route for the power to get to the prop. Jeff
Disadvantages abound.
Playing devil's advocate here. Be sure to do some Google work and understand the disadvantages as well. Seems awfully good at first. But just watch how much lower drive work goes on around the marina on the stinkpotters. You have an aluminum housing and a gear box hanging under your boat. And most sail drives come with a Volvo engine. Again that seems like a good thing. But they have a terrible reputation among sailors.
Playing devil's advocate here. Be sure to do some Google work and understand the disadvantages as well. Seems awfully good at first. But just watch how much lower drive work goes on around the marina on the stinkpotters. You have an aluminum housing and a gear box hanging under your boat. And most sail drives come with a Volvo engine. Again that seems like a good thing. But they have a terrible reputation among sailors.
Saildrive
Remembered an article in Sail Magazine last year on this subject. I believe it is Feb 2004 issue. Suggest you get a reprint. Also, did a quick Google and came up with these comments: my editing "decreases turbulence around the rudder and virtually eliminates "prop-walk" when in reverse" "Saildrive units not common in cruising boats...downside is large hole below waterline and need to haul boat to work on lower end of transmission...efficiency and simplicity more than compensate for this inconvenience. " "Sail drives similar to outdrives in appearance...inboard engine coupled to drive leg; but, unlike outdrives, sail drive non-steerable...power transmitted to the propeller through two 90° bevel gears...only available for engines under 30 hp...simple for builder to install, requires no shaft or stuffing box...drive can be positioned with limited restriction...throws prop wash over the rudder...often used in boats that normally use outboard motor...frees helmsperson from wrestling with both an outboard motor and the tiller during complicated maneuvers...major disadvantage is difficulty to seal...rubber gasket in bottom of the boat and under considerably more head than stern drive gasket...[could]flood boat quickly...regular replacement of seals not trivial job...requires adequate cathodic protection. Finally, unlike the outboard usually found on these boats, the engine cannot be removed for maintenance. Ocean Navigator Nov/Dec 1996" Ed Note: this latter article could be outdated - check the SAIL article for more current poop...
Remembered an article in Sail Magazine last year on this subject. I believe it is Feb 2004 issue. Suggest you get a reprint. Also, did a quick Google and came up with these comments: my editing "decreases turbulence around the rudder and virtually eliminates "prop-walk" when in reverse" "Saildrive units not common in cruising boats...downside is large hole below waterline and need to haul boat to work on lower end of transmission...efficiency and simplicity more than compensate for this inconvenience. " "Sail drives similar to outdrives in appearance...inboard engine coupled to drive leg; but, unlike outdrives, sail drive non-steerable...power transmitted to the propeller through two 90° bevel gears...only available for engines under 30 hp...simple for builder to install, requires no shaft or stuffing box...drive can be positioned with limited restriction...throws prop wash over the rudder...often used in boats that normally use outboard motor...frees helmsperson from wrestling with both an outboard motor and the tiller during complicated maneuvers...major disadvantage is difficulty to seal...rubber gasket in bottom of the boat and under considerably more head than stern drive gasket...[could]flood boat quickly...regular replacement of seals not trivial job...requires adequate cathodic protection. Finally, unlike the outboard usually found on these boats, the engine cannot be removed for maintenance. Ocean Navigator Nov/Dec 1996" Ed Note: this latter article could be outdated - check the SAIL article for more current poop...
Saildrive discription
These are a truncated version of an outboard motor, where the lower unit of an outboard sticks through the hull behind the keel and forward of the rudder. While the powerhead and the rest of the outboard sat inside the boat surrounded by a big rubber seal. Simple in concept, but troublesome to maintain as corrosion and seal leaking makes these units hard to maintain. Not my particular choice as a powersource.
These are a truncated version of an outboard motor, where the lower unit of an outboard sticks through the hull behind the keel and forward of the rudder. While the powerhead and the rest of the outboard sat inside the boat surrounded by a big rubber seal. Simple in concept, but troublesome to maintain as corrosion and seal leaking makes these units hard to maintain. Not my particular choice as a powersource.
Hype
Don't believe all the propaganda. 1) Throws LESS prop-wash onto rudder because it is normally further away so less low speed steering. 2) Needs a new rubber diaphragm every 7 years - Volvo. This means engine out. 3) Diaphragms are not cheap and are really a yard job. 4) I have seen a rubber technologists report of a 7 1/2 year diaphragm and the canvas insert was damaged and it was about to rupture. Then you will need a VERY big bilge pump. 5) Cannot change oil in sail-drive leg with boat afloat. 6) Yanmar has a double diaphragm with a water detector in between and no replacement period. Very clever unless the inner one perforates first. 7) Leg is aluminium and painted so any bare chips fizz like mad and people get VERY concerned about their special expensive anodes. However they are simpler and cheaper for the builder and have no shaft log, stern gland or alignment problems. Yes, shafts have problems too but Mr. Average can deal with them himself.
Don't believe all the propaganda. 1) Throws LESS prop-wash onto rudder because it is normally further away so less low speed steering. 2) Needs a new rubber diaphragm every 7 years - Volvo. This means engine out. 3) Diaphragms are not cheap and are really a yard job. 4) I have seen a rubber technologists report of a 7 1/2 year diaphragm and the canvas insert was damaged and it was about to rupture. Then you will need a VERY big bilge pump. 5) Cannot change oil in sail-drive leg with boat afloat. 6) Yanmar has a double diaphragm with a water detector in between and no replacement period. Very clever unless the inner one perforates first. 7) Leg is aluminium and painted so any bare chips fizz like mad and people get VERY concerned about their special expensive anodes. However they are simpler and cheaper for the builder and have no shaft log, stern gland or alignment problems. Yes, shafts have problems too but Mr. Average can deal with them himself.
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