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  #31  
Old 01-27-2009
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Real space savings?

I have had boats with inboard diesels with traditional shaft mounted props and now have a saildrive. Each have plusses and minuses. For a boat that would stay in the water cruising for a long time, I believe the shaft and strut and prop are the way to go. For the performance boat that comes out of the water often, the saildrive may be superior. In either case, the engine and transmission take up roughly the same amount of room. Some boats are offered with either option. I do not believe that a properly designed traditional installation will take up any more considerable room that a saildrive. Look at the Beneteau and Catalina and Hunter boats. All the cruisers still use traditional installations while trying to maximize interior volume. I have not operated a large catamaran with saildrives but have operated a large power cruiser with twin traditional shafts as well as a large catamaran with twin traditional shafts. I cannot see how the low speed docking and manuevering control of each might be improved with a saildrive, but perhaps they can. I do believe that the saildrive provides better low speed manueverability in a single engine monohull though. Last, I believe that the three factors driving the saildrive choice are that they present less drag that traditional strut and shaft installations, that the saildrive can be placed in an optimal location as far as weight and distance from rudder is concerned and that they are so much easier to install than a shaft and strut on a new build that they provide a considerable savings to the builder in both materials and labor.

Good luck,

121 Guy
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  #32  
Old 01-27-2009
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An argument in favour of the saildrive is the ability to put the engine nearer the CG of a monohull, but I don't see many models that do this, nor would it be a huge advantage over putting a traditional engine right over the keel and running a shaft at a shallower angle out the back.

People have fairly fixed ideas about how they expect saloons to look, and even a low box in the middle of a saloon isn't going to find a big fan base, no matter how logical it is in terms of keeping weight out of the ends of the boat.

It may have been an Ericson or one of the old Wanderers owned by the Hiscocks in the '60s, but I recall one boat where the presence of a fully insulated engine box didn't impede getting around in the boat, and the full access made up for it. I also recall dimly one boat with an engine mounted in the saloon that ran some sort of hot water tubing that turned the box into a sort of ceramic Dutch oven affair that kept the cabin warm when the engine was on.
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  #33  
Old 01-28-2009
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There is not a sailldrive under the sun that will work with a long keel double-ender, so for me, it's orthodox propshaft every time.

I can get to the gearbox in an instant, I can check its temperature, I can see a gearbox oil leak promptly, and I can change the gearbox oil in about 20 minutes, and I can take the gearbox right off there in about 2 hours ( I had to do that about 5 times before I finally got to the reason why it was leaking)... all of those points begin to matter on an older motor.

And I like watching a propshaft spin.

Engine alignment takes longer though. Saildrive doesn't have to worry about that one much.

Rockter.
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Last edited by Rockter; 01-28-2009 at 04:51 PM.
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  #34  
Old 01-28-2009
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Re: alignment. Get soft mounts for your engine and a universal joint coupler and your alignment problems (along with stresses the gearbox with gear shifting) is a thing of the past as the thrust bearing takes "the shock" and not the transmission.

A drive saver disc or two helps here, but doesn't solve alignment issues, particularly running the engine at angles of heel.
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  #35  
Old 01-29-2009
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Quote:
Originally Posted by Valiente View Post
An argument in favour of the saildrive is the ability to put the engine nearer the CG of a monohull, but I don't see many models that do this, nor would it be a huge advantage over putting a traditional engine right over the keel and running a shaft at a shallower angle out the back.
Interestingly, this is exactly what I am moving away from with my saildrive conversion. The boat is a late CCA/early IOR influenced old ocean racer/cruiser, and the original design had a shaft drive sitting right on top of the keel. Great for performance, but takes up half the salon (boat is only 34 feet).

While putting a traditional shaftdrive under the companionway steps is an option, I'd be a bit worried about performance under power, given the need to have a pretty steep angle on the shaft and the fact that the prop would end up quite close to the skeg hung rudder. Couple that with the fact that I'll be hauling out every winter and my usage will be more like daysailing and weekending, and it became a pretty easy decision to go with the saildrive.
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  #36  
Old 01-29-2009
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If it's daysailing and weekending, why not save money and space and just have an outboard on the back?

No, I'm not joking! Conversely, you could have a fibreglass well built and drop an outboard in there for more protection and less weight off the end.

People used to scull boats up to the high 30s in length with 14 foot sweeps...but perhaps this is too much economy for the modern cruiser.

The rule of thumb for engines, shafts and prop clearance is 14-15 degrees of "tilt" and the prop needs 10% of its diameter in clearance from the hull.

I have a pretty similar boat, and for all its wonderful attributes in my mind, cutting a hole in the hull to drop in a new diesel saildrive would cost more than it is worth. But if you love the boat so much that you expect to have it 25 more years and never expect to recoup the cost of conversion, then it's not going to bug you.
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  #37  
Old 01-29-2009
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Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice
Off course, if I was dragging a 20.000lb long keel, and had a rudder behind all kinds of gimmicks, I wouldn't bother with a saildrive..

I'd be more concerned with other things to make the boat move by force of wind...such as sails, mast etc...the drag caused by a shaft wouldn't worry me...

Now...

LOOK BELLOW...look at the drag signature on this!!!

Tell me..look at the profile from the front..look at the minimal size, look at the cleanliness of the lines..and tell me..if you were really concerned with making the boat move by sailing...wouldn't you want a puppy like this saildrive???

Be honest!! Wouldn't you??





Different purposes with different systems

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Last edited by Giulietta; 01-29-2009 at 02:07 AM.
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  #38  
Old 01-29-2009
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Well...the sail drive makes sense but you need to get rid of that big shark looking thing...that has GOT to create a lot of drag!
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  #39  
Old 01-29-2009
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He did...the most recent photos have a plain white, boring, bulb....he thinks the shark was scaring off the dolphins...
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Originally Posted by camaraderie View Post
Well...the sail drive makes sense but you need to get rid of that big shark looking thing...that has GOT to create a lot of drag!
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  #40  
Old 01-29-2009
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Quote:
Originally Posted by Valiente View Post
If it's daysailing and weekending, why not save money and space and just have an outboard on the back?
Daysailing and weekending are the immediate future, but the boat was built for offshore. An outboard is not an option in my view for this particular boat and for my future (hopefully) usage.

Quote:
Originally Posted by Valiente View Post
I have a pretty similar boat, and for all its wonderful attributes in my mind, cutting a hole in the hull to drop in a new diesel saildrive would cost more than it is worth. But if you love the boat so much that you expect to have it 25 more years and never expect to recoup the cost of conversion, then it's not going to bug you.
Who said the cost doesn't bug me??? That being said, 90% of the cost is for the engine itself and would have been incurred for a shaft drive as well. Installation of the saildrive is actually pretty easy.
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