Saildrive vs Shaft Drive

[Tropic Cat]

I agree that shafts and propellers are preferred.

The latest trend in installing sail drives well aft in catamarans is troubling. I understand the builder's layout reasons; yet on some cats the engines are so far aft as to be accessed by lifting the transom steps. Hasn't anyone (other than me) had to change out fuel filters in lumpy seas?

I wouldn't consider an aft mounted saildrive Cat as I'm not nimble enough to want to attempt servicing at sea.

[GordMay]

Has anyone used the Hübner-Braun “cycloidal” (fixed or retractable) propeller (similar to the larger Voith-Schneider system)?

[cchesley]

In a perfect world, I'd prefer shaft drive. But I bought a boat with saildrives. Why? The everyday advantages of layout, performance and convenience trumped the few days that I might have where I'm ticked off and frustrated with the cost/hassle of repairing the sail drive. It's not the 'hill to die on' for me. Everything is a compromise. Pick your poison.

[Whimsical]

Originally Posted by rickm505

I agree that shafts and propellers are preferred.

The latest trend in installing sail drives well aft in catamarans is troubling. I understand the builder's layout reasons; yet on some cats the engines are so far aft as to be accessed by lifting the transom steps. Hasn't anyone (other than me) had to change out fuel filters in lumpy seas?

I wouldn't consider an aft mounted saildrive Cat as I'm not nimble enough to want to attempt servicing at sea.

Another problem with engines so far aft is the tendency to increase hobby horsing
Mike

[scotte]

Originally Posted by tyrntlzrdking

I am also concerned about headroom on the P39's saloon. I am 6'1 and would like to be able to stand erect. How much room do you have?

I'm 5'11" and I'd say the saloon headroom is 5'11" - I just checked . The hulls have quite a bit more. Definitely could be an issue for some, I don't find it an issue, I just don't stand there, and it doesn't seem to be bad while walking/moving around. I don't have answers to you other questions, sorry!

[Factor]

Of course there is another option - outboards. You wont find too many in bigger cats (though I know some 43 foot Peter Kerr Aluminium Cats that run diesel outboards) that are production based but there are plenty in large one off boats. The outboards don't have to be dragged in the water when sailing, they are easily removed for servicing, they way less than inboards. On the down side you need to ensure they are located in a place that limits cavitation and more importantly VENTILATION. Some people say that you need inboards for the alternators - if you have air-conditioning and similar mobile home luxury that's a distinct possibility but if you have a sane low spec system and good solar and wind capability then its not such a big deal, particularly with the lectrical efficiency that you can get these days with LEDs and other appliances.

Also petrol outboards on cats are usually a reasonable deal, safety wise as the tanks and motors can all be mounted where there is an ability for the fumes and gases to dissipate harmlessly.

For me outboards will be the preference if I get a choice, if I don't then I don't and that will usually mean I dont get a choice of sail drives or shafts etc etc.

[tyrntlzrdking]

Thank you all for your input.

Factor, I agree. Outboards are a good option for me over saildrives.
If I cannot find a good used ocean crossing boat with shaftdrives, then I may start out with a smaller boat with outboards for cruising the Great lakes and along the coasts of America.

I have been leaning towards the Tomcat 9.7.
The outboards are located in the hulls and can be retracted out of water.
I hope this would not cause cavitation problems? The Tomcat has 24" of unobstructed bridgedeck clearance.

Some boats with outboards have the engines located under the bridge deck surrounded by an encloser. This interferes with bridgedeck clearance, and I assume would not manuver as well at slow motoring speeds.

Jeff

[Eleven]

'amarinesurveyor' is accurate in what he says. Remember that most cats can be beached at high tide to give good access to all underwater areas. Routine maintenance is not a problem, just watch the stated draft of your choice.
The good old Prout's use a hinged sail drive leg which gives you a permanently mounted engine as usual in the centre of your cat, and a drive leg that is raised when not in use. Prop fouling seal changing etc are possible off of the deck.
It also means that you are not dragging the gear in the water which seems to be worth at least half a knot! x 24 hours x 24 days = 288nm extra. FREE.
See also the Autoprop thread. They help to reduce drag and are a definite noise and fuel saver. I experienced an odd problem that I haven't got to the bottom of yet but experienced others swear by them.
If your are looking to keep costs down the snowgoose 37's are cheap, very sound and very safe for a solo. 20 + years old and you'll need a good surveyor for peace of mind. For two up look at the Event 34's with 2 big beds, airy conservatory for living quarters. Then compare new boats on price! Most secound handers come with lots of kit that you'll have to add to a new boat, just allow for updating half of it.
Just please don't bid on the one I want!
I've found it really usefull to view older boats to see what mods have been done and which might be worth having.
Long journeys - keep the weight down, keep spares to a minimum. Your motor is a back-up device, don't go where you can't sail away from!
See you out there -

[Davey1000]

Originally Posted by never monday

I can't remember if it's the tin or copper based paint that is banned here.

In the class of boat your looking at 35-40ft it realy is of minor consequence which drive config is in place. Both have advantages, both have disadvantages.

Accept that there is no perfect boat and accept the comprimise. To get something sea kindly, you loose pointing, to get something that point, you'll loose tracking ability.

A shaft "can" be hard to align. but it's easier than stopping the leak from a torn boot. A new shaft and prop might cost 800, a new SD unit can go above 2000 quickly.

Re shaft alignment, there are solutions to this. For small errors one can use the Vetus "Bullflex". For larger errors there is the "Aquadrive" constant velocity joint. The enormous advantage of the Aquadrive is that the propeller does not push the engine. This enables soft engine mounts to be used. IMHO the advantages of shaft drive are numerous. The water intake for example can be a major problem on sail-drives. With shaft drive it is possible to arrange the intake to suit local conditions. The waters off Portugal for example are infested with swarms of jellyfish at times and these will clog water intakes. If one has a proper basket-type filter, the jellyfish tentacles can be prevented from reaching the engine. Good luck!

[captain58sailin]

I don't have any personal experience with sail drives, but I have read a large number of posts on this forum, complaining about the high maintenance issues with sail drives. Me I go with the K.I.S.S. philosophy. The simpler the better, especially when contemplating a round the world tour. I am a proponent of the straight shaft / prop school, with the dripless shaft glands, I have used them for years in some of the toughest envirnoments in the world with no problems. If you are worried about the dripless glands then go with conventional glands and one of the modern packings that are available that work quite well. As far as shaft alignment goes that is not an issue unless you have to replace the engine or transmission or both, then some feeler gauges and some patience will sort it out soon enough, and they do make these nifty nylon doughnuts that you can bolt to the shaft flange to smooth out any minor imperfections in the alignment or flange faces.

[fotografipro]

Hi all, for me the issue is simple. Anything required on a yacht that requires a bloody great hole cut through the hull is a no no for me! I'll remain shafted..;-)

[Thalas]

Originally Posted by amarinesurveyor

Sail drives have some advantages - they are less drag than a straight prop and strut, the prop thrust is horizontal and not on an angle as with a shaft drive, they take up less space, and they are less labor to install than a shaft drive.

You forgot a HUGE one... livability. On modern Cats, sail drives allow for aft placement of the engine. You are not sleeping ON (Cats) or NEXT TO (Monohulls) the engine as on shaft drives. Quieter. Less heat. More comfortable. Those are huge factors. Yes, maintenance is increased, but they have come a long way (like automatic transmissions getting better over time vs manual). And when you need to work on engines, you are bringing all of those greasy parts into a dedicated engine bay and NOT into a bedroom with the mattress lifted out of the way.

[valhalla360]

Originally Posted by fotografipro

Hi all, for me the issue is simple. Anything required on a yacht that requires a bloody great hole cut through the hull is a no no for me! I'll remain shafted..;-)

Of course with shaft, you have two holes (prop shaft and water intake). If either opens up, it can easily overwhelm a bilge pump.

No perfect solution though I am partial to outboard as being the lowest maintenance. As long as the boat is designed for outboard power (not just bolt one on the stern and hope for the best), it's probably the best option.

[JohnT]

All the old Simonis designed Leopard cats were shaft (38, 42, 43, 45 and 47). All the Leopards from the M&M designs to the present Simonis designs are SD.

[Heath68]

Does anyone know why manufacturers don't use V drives? I would have thought this would be the best of both.. all the holes/maintenance/reliability? advantages of a shaft drive and the ability to (almost) locate where a saildrive would normally sit.

Does anyone know if many manufacturers offer this alternative?

Heath