Saba 50 vs Antares

[2Hulls]

Originally Posted by smj

I wonder which would flood quicker, losing a shaft in a shaft drive or losing both seals in a sailsdrive boat.

Well, let's explore that.

Which sail drive seals are you talking about?

"Both seals" to me means the two seals on the prop shaft, which if both happened to completely fail - however remote that may be - would result only in the sail drive fluid getting contaminated with sea water and losing sail drive oil to the sea. Nothing, however, gets into the vessel. If the boot seal or "bellows" fails, the engine room would be flooded up to the water line. The rest of the boat - assuming a separated engine room - may not even know it happened.

Dave

[smj]

Originally Posted by 2Hulls

Well, let's explore that.



Which sail drive seals are you talking about?



"Both seals" to me means the two seals on the prop shaft, which if both happened to completely fail - however remote that may be - would result only in the sail drive fluid getting contaminated with sea water and losing sail drive oil to the sea. Nothing, however, gets into the vessel. If the boot seal or "bellows" fails, the engine room would be flooded up to the water line. The rest of the boat - assuming a separated engine room - may not even know it happened.



Dave

I was talking seal and bellows but wouldn't count on the assuming part

[downunder]

There have actually been cases of ropes around saildrive props sinking vessels.

[2Hulls]

Originally Posted by smj

I was talking seal and bellows but wouldn't count on the assuming part

OK, on most sail drive boats the sail drive and bellows is in an isolated engine room. That's the case on my boat. If the bellows fails, the engine room gets flooded up to the water line + a little more. On my boat that wouldn't even disable the engine, much less swamp the boat.

For a failed shaft, the flooded volume would have to be similarly contained. This may be easily achievable, but how often is it?

Dave

[smj]

You have more faith than I.

[2Hulls]

Originally Posted by smj

You have more faith than I.

In what way - hoping shaft failures would be contained? If I was designing a shaft drive boat that's the way I would do it.

Dave

[smj]

Faith in your engine not taking on water. Maybe in calm water.... But I would doubt it.

[BigBeakie]

Originally Posted by downunder

There have actually been cases of ropes around saildrive props sinking vessels.

Witness the case of the Lagoon in Thailand that sunk because the engine compartment was not waterproof and flooded the hull. Then long legal battle ensued.

Anyone with saildrives would do well to make sure their engine compartment is water tight and that the manufacturer guarantees, in writing, that it is.

[2Hulls]

Originally Posted by smj

Faith in your engine not taking on water. Maybe in calm water.... But I would doubt it.

Well, come visit and see for yourself. The starter might get wet........

Dave

[DotDun]

Originally Posted by smj

I wonder which would flood quicker, losing a shaft in a shaft drive or losing both seals in a sailsdrive boat.

You need to worry about the extent of flooding the entire hull vs. an engine room with solid bulkheads fore/aft of the engine. I lose both seals on my saildrive and take on maybe 40-50 gallons of water (to the top of the engine oil pan). The Antares loses a shaft and has a completely flooded hull (covering the engine, living space, etc.).

[BigBeakie]

Originally Posted by DotDun

You need to worry about the extent of flooding the entire hull vs. an engine room with solid bulkheads fore/aft of the engine. I lose both seals on my saildrive and take on maybe 40-50 gallons of water (to the top of the engine oil pan). The Antares loses a shaft and has a completely flooded hull (covering the engine, living space, etc.).

Just curious, what would cause the loss of a shaft? What circumstances would that occur under?

Tearing the boot of a saildrive I get, but what would tear the shaft out of a boat? Assuming it's correctly engineered in the firstplace, naturally.

[smj]

Originally Posted by DotDun

You need to worry about the extent of flooding the entire hull vs. an engine room with solid bulkheads fore/aft of the engine. I lose both seals on my saildrive and take on maybe 40-50 gallons of water (to the top of the engine oil pan). The Antares loses a shaft and has a completely flooded hull (covering the engine, living space, etc.).

I'm sure it wouldn't be a problem to drive a wooden plug into the empty tube of a shaft drive. Saildrive, maybe a bit more of a problem. We've owned a Saildrive driven catamaran as well as shaft drive, stern drive and outboard. We never had any catastrophic problems with the Saildrive but it would be my last choice. Something about a large chunk of aluminum sitting in the water 24 hours a day exiting through a large hole in the boat doesn't sit well with me. But don't get me wrong, if that's the only way my dream boat came I would accept it.

[DotDun]

Originally Posted by smj

I'm sure it wouldn't be a problem to drive a wooden plug into the empty tube of a shaft drive. Saildrive, maybe a bit more of a problem. We've owned a Saildrive driven catamaran as well as shaft drive, stern drive and outboard. We never had any catastrophic problems with the Saildrive but it would be my last choice. Something about a large chunk of aluminum sitting in the water 24 hours a day exiting through a large hole in the boat doesn't sit well with me. But don't get me wrong, if that's the only way my dream boat came I would accept it.

As with everything, saildrives present trade-offs. Aluminum housing full of shafts, bearings, gears, and oil hanging in the water enables engines to be placed outside the living space in a dedicated engine room. No diesel or oil smell, no heat, and less noise in the living space. And yes, easier and cheaper installation.

Driving a wooden plug into an empty shaft tube might be possible (wearing goggles and snorkel ), but a properly designed engine/saildrive space flooding due to a failure of multiple seals/boots is simply not a catastrophe, i.e., not requiring immediate action to save the boat from sinking.

Yes, slightly more maintenance than shafts, saildrives require proper care. But, 30+ years have proven they are very reliable and trustworthy.

[smj]

Originally Posted by DotDun

As with everything, saildrives present trade-offs. Aluminum housing full of shafts, bearings, gears, and oil hanging in the water enables engines to be placed outside the living space in a dedicated engine room. No diesel or oil smell, no heat, and less noise in the living space. And yes, easier and cheaper installation.

Driving a wooden plug into an empty shaft tube might be possible (wearing goggles and snorkel ), but a properly designed engine/saildrive space flooding due to a failure of multiple seals/boots is simply not a catastrophe, i.e., not requiring immediate action to save the boat from sinking.

Yes, slightly more maintenance than shafts, saildrives require proper care. But, 30+ years have proven they are very reliable and trustworthy.

You hit it on the head when you said easier and cheaper installation. In my opinion that's why the manufacturers use them.
I'm not sure about the reliable and trustworthy statement. I've seen my fair share of saildrives that have corroded completely through and having to replace cone clutches every few hundred hours on some of them? They have found their place in the market but I personally don't care for them.

[DotDun]

Originally Posted by smj

You hit it on the head when you said easier and cheaper installation. In my opinion that's why the manufacturers use them.
I'm not sure about the reliable and trustworthy statement. I've seen my fair share of saildrives that have corroded completely through and having to replace cone clutches every few hundred hours on some of them? They have found their place in the market but I personally don't care for them.

That's why they still make transmissions and shafts.

FWIW, improperly maintained transmissions/shafts are not trouble free.