Sail Drives VS direct drives

[smj]

Sure love my outboard!


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[Captain Bill]

Originally Posted by jmschmidt

Do you think your keel will protect your sail drive if something (another boat) hits you from the side near the stern? Or a heavy, barely floating object contacts the side of the boat, slides along the water line and get sucked into the sail drive when boat and object are moving at relatively high speed. Or you're under power trying to stay to windward of some coral heads and crosswinds blow your stern and sail drive onto a submerged one. There are many more ways to sink a boat than by a head on collision.

In my boat the sail drives are located approximately 3 feet from the outside of the hulls. If something hits me so hard as to bust through to the saildrive the hole made by the saildrive will be the least of my problems. Where they exit the hull is almost 2 feet below the waterline so I'm not worried about "floating objects too much. If I'm moving at high speed I'm sailing and the props are not sucking anything. I once picked up a large string of lobster pots in Maine while sailing at 9 knots and it dragged me down to 3 knots in a heartbeat. There was no indication at all that the saildrive mounts were even stressed. Knocking 6 knots off of a 20000 lb boat doing nine knots takes an awful lot of force not to mention dragging that line of pots until I could determine which engine was fouled, start the other one, get the sails depowered etc. Sail drive mounts do not break easily and if the mount doesn't break the seals are not going to fail. They are very tough. I replaced mine after 10 years and there was no sign of any wear, cracking, crazing, brittleness, or any other signs to impending failure.

Oddly enough your coral head description closely fits an encounter I had in a channel at Pennekamp park in the Florida keys this summer. I was forced to the side of a narrow channel because a tourist catamaran insisted on entering the channel when I was 3/4s of the way through it. The tide was running across the channel as well. In any case I had to keep my speed up to maintain steerage in the cross current and hit a rock with my keel which lifted the starboard hull several inches and dropped the sail drive on top of the rock. The actual sail drive did not hit the rock, but I did bend one heavy stainless steel blade from my autostream feathering prop. I had the boat hauled and the significant damage to the keel repaired and the prop blade straightened. I had the sail drive inspected and there was no detectable damage, There was certainly no sign that the mounts or seals were damaged.

[smj]

We have owned 10 cruising catamarans and just about any imaginable drive configuration that could be installed on a catamaran, and I still can't understand how people could stand behind the sail drive as their choice. A chunk of aluminum installed below the waterline full time with a large hole cut in the boat protected by a rubber gasket? So many points where it could fail with catastrophic outcomes yet it is pretty much the industry standard. It's the industry standard because it's easy and inexpensive to install. That being said, we owned one catamaran with sails drives. Although the sail drives showed signed of corrosion, we never had a problem. I don't believe the person we sold the boat to had any problems either. I personally wouldn't let sail drives stop me from buying the boat of my dreams, but they most assuredly wouldn't be my first choice by far.


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[Thumbs Up]

Sail Drives are pretty much standard on 35'-45' cats. The answer is obvious, just buy a big catamaran.

[rabbi]

Originally Posted by DotDun

As long as both engines are running......if you have one engine down, you have no steerage until 1-1.5kts of speed.

That's certainly true. But at least to me not an important consideration. how often does one have to maneuver with just one engine?

[rabbi]

Originally Posted by Palarran

In this specific instance, the saildrive was torn off by the line, but the boat sank (flooded more appropriately as it didn't sink) because they had drilled holes through the watertight bulkhead and didn't seal them.
.

Lagoon and Fontaine Pajot are built differently, at least the ones i owned.
FP has watertight bulkheads with no penetrations below bridge deck level.
Lagoon has penetrations even in the deepest bilge area for houses, wires and fuel lines, somewhat sealed using PU spray foam.

[yeloya]

Originally Posted by roland stockham

You missed what is for me the clincher. With a sail drive the integrity of the hull relies on a large rubber seal around the leg. to make it worse it is a long leg. Even a small impact at the prop risks breaking that seal and no pump system will stand a chance if it fails. On a mono where it is behind the keel it has some protection but on a cat there is probably nothing.

This not true for the cat. Yes, if it happens on a mono , it takes you less than 10 min. to sink. (no positive buoyancy)
I had a bent rudder shaft in the middle of the Ocean in a 43 cat with a sail drive and the water was freely filling the engine room. But the water was just 2-3 inches, and never passed the floating level of the boat.
Actually I continued using my engine until I was back home.
If I was to buy a mono, I would go for a shaft but on cats sail drive is much better for many reasons already explained. Remember on the other hand that sail drive can be installed up to 80 HP engines. Beyond that you don't have a choice other than shaft.

Cheers

Yeloya

[DotDun]

Originally Posted by smj

We have owned 10 cruising catamarans and just about any imaginable drive configuration that could be installed on a catamaran, and I still can't understand how people could stand behind the sail drive as their choice. A chunk of aluminum installed below the waterline full time with a large hole cut in the boat protected by a rubber gasket? So many points where it could fail with catastrophic outcomes yet it is pretty much the industry standard. It's the industry standard because it's easy and inexpensive to install. That being said, we owned one catamaran with sails drives. Although the sail drives showed signed of corrosion, we never had a problem. I don't believe the person we sold the boat to had any problems either. I personally wouldn't let sail drives stop me from buying the boat of my dreams, but they most assuredly wouldn't be my first choice by far.


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An analogy to your statement....."I can't understand how people can get inside an aluminum tube that take them up in the air! There are many points of failure with catastrophic outcomes!" Reality is saildrives, like flying, are statistically safe! Also, like airplanes, saildrives require routine maintenance, hence, almost every catastrophic failure of a saildrive can be traced to either deferred maintenance or operator error. If you don't want to maintain a sail drive, don't buy one!

[SVNeko]

Originally Posted by smj

We have owned 10 cruising catamarans and just about any imaginable drive configuration that could be installed on a catamaran, and I still can't understand how people could stand behind the sail drive as their choice. A chunk of aluminum installed below the waterline full time with a large hole cut in the boat protected by a rubber gasket? So many points where it could fail with catastrophic outcomes yet it is pretty much the industry standard. It's the industry standard because it's easy and inexpensive to install. That being said, we owned one catamaran with sails drives. Although the sail drives showed signed of corrosion, we never had a problem. I don't believe the person we sold the boat to had any problems either. I personally wouldn't let sail drives stop me from buying the boat of my dreams, but they most assuredly wouldn't be my first choice by far.


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All logical, yet catastrophic failures are exceedingly rare.

[dlockhart]

Lightning came through the ground side of our shore power and exited to the water through the sail drives. It blew chunks out of the housings and trashed everything below the water line. Replaced them both on a low tide with the SD25's and about $7K.

[smj]

Originally Posted by DotDun

An analogy to your statement....."I can't understand how people can get inside an aluminum tube that take them up in the air! There are many points of failure with catastrophic outcomes!" Reality is saildrives, like flying, are statistically safe! Also, like airplanes, saildrives require routine maintenance, hence, almost every catastrophic failure of a saildrive can be traced to either deferred maintenance or operator error. If you don't want to maintain a sail drive, don't buy one!

I've never seen an airplane that spends its whole life submerged in saltwater and is still in working order! I agree, any form of propulsion needs to be maintained but in my opinion the saildrive is very high maintenance.

[SVNeko]

What's all this maintenance people keep talking about?

[smj]

Originally Posted by SVNeko

What's all this maintenance people keep talking about?

Priming and bottom painting when hauled.
Changing the oil every 100-250 hours.
Changing the seals every 5 years.
Changing zincs before they disappear.
Changing shaft seals when needed.
Most of these items require a haul out.

[rabbi]

Originally Posted by smj

Priming and bottom painting when hauled.
Changing the oil every 100-250 hours.
Changing the seals every 5 years.
Changing zincs before they disappear.
Changing shaft seals when needed.
Most of these items require a haul out.

My experience is different:
Painting: yes!

Oil: Fresh oil when I buy a used boat, then just regular checkups. Fresh oil whenever there is just the slightest color change or it becomes milky (plus new seals as soon as possible). Otherwise fresh oil every few years. Certainly not every 100hrs. Easy DIY

Seals: Manufacturer spec as far as I remember is every 7 years. Reality is way more. While boat shopping I have come across only 2 boats that had them changed before age 15. And never heard of any failure. Not so easy DIY, but doable. Around 600 Euros just in parts per SD

Zincs: Mine were installed by the PO in 2012 and were at 90-95% when launched this year. Good for many years. Easy DIY

Shaft seals: Every few years, or ASAP if the oil becomes milky. OK for DIY unless seals got stuck which requires special tools.


The only regular maintenance required is checking the oil for water ingress, say every other week when in use. I just do it whenever I check the engine oil. So not what I consider a high maintenance item on board.


I'm not saying that a saildrive is my first choice, but its just one more compromise in the decision making process of selecting my next boat. Failures are so rare I don't care (plus I have had my saildrive incident, so statistically I'm safe for many decades )

[belizesailor]

Originally Posted by Palarran

I think a lot of the new cats have sail drives aft of the rudders and agree, that's not very good. ...

A number of Lagoon models do. The biggest pain is when backing a lot...the friction wheel locks they use are not strong enough to hold the wheel against the prop wash...esp on bigger Lagoons like the 50...PITA to keep fighting the wheel and working throttles while backing...usually in tight quarters of course. Ive assigned a crew member just to hold the wheel before, but dont always have one available.

Also eliminates the possibility of directing forward thrust prop wash with the rudders, but thats not something you do often on a cat anyway.