Saildrives?

[catsrule]

Originally Posted by georgetheleo

It may sound silly but Im afraid of and irrationally opposed to saildrives. Bascally all I really know of them is: the larger Yamaha ones develope slipping "cones" and need special tools and big bucks to repair.what if you are in timbucktooo? The smaller Yamahas dont have this problem but are limited to 30hp. The Volvo saildrives are much more reliable but the volvo engines are not and parts cost a fortune. Why cant saildrives be converted to straight shat drives if there is room? What about those Beta saildrives and engines? Comments please--- Thank You

I agree with you. I had a Belize cat with the Yanmar SD50 and had lots of trouble cost me shed loads of money to get them replaced. We are looking at an Isara 45 catamaran which has shaft drives and mid engine. A lot less hassle.
I would not buy a cat with sail drives again. .

[Cotemar]

Originally Posted by catsrule

I would not buy a cat with sail drives again. .

Sort of like saying that you wouldn't buy another car because you had one with a bad engine. 99.9999% of all production boats have sail drives that work perfectly.

All those defective Yanmar SD 50 with bad cone clutches should have been recalled by Yanmar. It's clearly a scare on there reputation to sell defective sail drives and not recall and repair them. Shame on them.

[ggray]

Andrew, looks like you have given this a good study. I haven't looked through your numbers carefully, but assume they are correct.

I wondered about the CoE of oil, but never went to the trouble of finding it. My theory was just speculation, and whether it was fact or not would have no bearing on anything I might do about the saildrive. I was already developing the idea of the expansion tank to relieve pressure differentials from any cause.

But one thing I think your analysis of a simple shape might miss is that the housing is not a uniform shape. The key thing is that the area of the top surface of the oil is small, if the picture in my mind of the upper leg is correct, as compared to the rest of the oil "vessel". Sort of like (but not so extreme) the magnified rise and fall of the liquid in a glass thermometer.

Originally Posted by Andrew Troup

This is my second attempt at this post.

When I pressed "Submit", the forum software evidently thought I was intending to surrender, and decided I wasn't logged on, and tossed my first submission out the air-lock into cyberspace.

(... even though I had just logged back in after the site came back after a maintenance period, and my name appeared at the top of the same page)

Sigh...

I did a quick calc to make sure my intuition here was not off-beam.

Conveniently, because the coeff for alu is double that for steel, and the latter similar to oil, I was able to do the calc for a steel sternleg containing a fluid with a zero coefficient. The answer should be about the same.

(Alu: 20 millionths linear expansion per deg C; Steel and Oil: 10 millionths)

The volume of a 100mm cubic (1 litre) steel container, for 1 deg C increase, would grow to about 1.00001^3 of the original size, or ~ 1.00003
Hence a volumetric increase of 1.00003 – 1 , or 0.00003 litres

so for a 30 degree C rise, the volumetric increase would be thirty times this, or 0.0009 litres, say 0.001 litres, or one-thousandth of a litre

Which would *roughly* be a level change of one tenth of a millimetre in the original container. (because 100mm level change corresponds to a whole litre)

in US customary units: a change in level of about four one-thousandths of an inch, for a temperature change of about 85 degrees F.

[smj]

I wouldn't let saildrives stop me from buying a cat I really wanted, but I would much rather have straight shaft. Saildrives to me just don't make sense.


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[dennisail]

I'd rather a light cat that sails very well and use outboards.

[houlihan1941]

In 2009, I thought I had some clutch slippage in my saildrive, and was concerned about slipping while bashing up the Baja coast to San Diego. I had the cones (catamaran) replaced in Mazatlan.
The result was an addition recommended by the mechanic. I added Mercury reservoirs to each sail drive mounted higher in the boat than the prop shaft was below the water line. Each reservoir was partially filled with SD oil with a drain tube to the top of the SD.

The result was that if the prop shaft seals began to wear and leak, I would see in the reduced level of oil in the reservoir. If leaking was discovered I could just add more oil until I was at a place to haul the boat or otherwise address the seal replacement. This totally eliminated salt water getting into the lubrication system in the SD and prevented any damage resulting from SW intrusion.
I have heard there my be objections to this, but have not aware of such, but would welcome those with more experience. The current owner has the boat in the south pacific and I imagine still has the system in place.

[Dogscout]

Since a saildrive is essentially the lower end of an outboard and we all know how those new fangled outboards are just a fad, you can never trust one. And props falling off all over the world will surely result in you being eaten by sea creatures.

Saildrives fail, transmissions fail, engines fail, props get installed by ham fisted mechanics, hell all mechanical things have a life expectancy. Stuffing boxes fail, exposed shafts get hit and bent on rocks, shift bushings fail, metal corroded, etc etc.

Pick your poison. Maintain your boat.

[smj]

Originally Posted by Dogscout

Since a saildrive is essentially the lower end of an outboard and we all know how those new fangled outboards are just a fad, you can never trust one. And props falling off all over the world will surely result in you being eaten by sea creatures.



Saildrives fail, transmissions fail, engines fail, props get installed by ham fisted mechanics, hell all mechanical things have a life expectancy. Stuffing boxes fail, exposed shafts get hit and bent on rocks, shift bushings fail, metal corroded, etc etc.



Pick your poison. Maintain your boat.

The lower unit of an outboard is kept clear of the water when it in use, huge difference.

[Sohum]

Originally Posted by houlihan1941

I added Mercury reservoirs to each sail drive mounted higher in the boat than the prop shaft was below the water line. Each reservoir was partially filled with SD oil with a drain tube to the top of the SD.

The result was that if the prop shaft seals began to wear and leak, I would see in the reduced level of oil in the reservoir. If leaking was discovered I could just add more oil until I was at a place to haul the boat or otherwise address the seal replacement. This totally eliminated salt water getting into the lubrication system in the SD and prevented any damage resulting from SW intrusion.
I have heard there my be objections to this, but have not aware of such, but would welcome those with more experience. The current owner has the boat in the south pacific and I imagine still has the system in place.

Im adding vent tube w/res. However, not adding gear oil, it’s to equalize pressures. Next gear oil change I’m gonna mix (smallcrank it container) used quicksilver oil and slowly add sea water to it, I hear “chocolate milk” similar coolant in oil. I have a feeling its not as easy to detect in QS. Maybe it is. This is my second haul bottom paint, definitely doing lower leg service as well. I lapped cones at 1700 hrs. No record from previous owner. It was straightforward. However I took the unit to a shop to zip the top locknut off. The assembly was slipping in the vice and I wasn’t about to clamp down more. I couldn’t find the lapping compound in Ft Lauderdale, not much help from shops. I ordered the right 1 online. Caution about reassembly, double check the shifter assembly fully seats in housing, proceed from there.

[SV WELDER]

To me sail drives seem like a solution in search of a problem. Why make it harder than it needs to be? I’d rather keep my gear boxes dry and indoors. If they are simply for the factories to save effort then that seems like a crappy thing to accept.

[Emmalina]

Stick out like a keel and supported by rubber No thanks Normally owned by people who live in Marinas so the anodes go. Seen to many with problems! Stuffing box is 41yrs old and perfect thanks

[SV WELDER]

Originally Posted by Emmalina

Stick out like a keel and supported by rubber No thanks Normally owned by people who live in Marinas so the anodes go. Seen to many with problems! Stuffing box is 41yrs old and perfect thanks

Totally agree. Reminds me of those who talk down on jet pumps also. Talking about efficiency and reverse etc but they overlook the mechanical elegance of having only one moving part in the entire jet pump. And that it doesn’t stick out at all. Okay, not very relevant to a sailing boat except for that toying sticks out part. That would be a fair hull. But no, we won’t go there. So, the next most elegant in my eye is a nice long keel that fully supports and protects the straight drive bronze prop. Something I can bang around a little, grind on, straighten, etc. and keep that tranny warm and dry.
Also in the elegance earned category for a cat might include twin outboards? There are definitely big pros and big cons with this setup but it is very interesting. Imagine your craft having three identical 15hp motors, one for the dink! Heck, keep a complete 4th as a spare. And the fairest of hulls when fully removed from water. I love a little basic diesel but I don’t think I’d mind the outboards either. Easier to find fuel also?

Lastly, is saildrives. They scare me to death. I bet they have those octopus arm water pumps like outboards do too don’t they? That clog and starve your diesel of cooling water? I’m just asking I really don’t know.

[tamicatana]

And here I am with a 30YO cat with its original saildrives; boat sailed across from France to Martinique where its first 10 yr was in charter; moved on her own bottom to the Chesapeake, where she lived on her owner’s dock; bought and delivered by me to our home in Mississippi 10 years ago; living full time aboard for last five years bt N. GOM, Keys and Bahamas; and my 1992! 120S drives are still going.

Please quit spreading crap about stuff you know nothing about. SD are higher maintenance, sure, but they are not going to dissolve, break off or leak with reasonable care given to them

[Luvboats]

Owned many boats
Some sail drives
Some shaft drives
Some outboards
Some oar powered
Some paddle powered
Some wind powered
All fun
All work
Some cheaper
Some expensive
Some filled with headaches
Some not

[belizesailor]

Originally Posted by SV WELDER

To me sail drives seem like a solution in search of a problem. Why make it harder than it needs to be? I’d rather keep my gear boxes dry and indoors. If they are simply for the factories to save effort then that seems like a crappy thing to accept.

Yes, they are mostly beneficial to builders, but most production cats use them. So, if in the market for a cat odds are high it will have SDs.