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Old 02-01-2014, 08:58   #16
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Re: sail drives..like em?

The Pretorien was designed by Holman and Pye for a saildrive. The engine space is so designed, and if you look at the boats with a shaft, it is at a very steep angle that puts the prop angled quite downward.

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Originally Posted by robert sailor View Post
In the past you could buy a Wauquiez Pretorien 35 in either a sail drive or shaft. You could buy a Niagara 35 in either a sail drive or shaft. I am very familiar with these boats and they are at the top of the list for good older boats to take offshore in this size range and you had a choice when you bought them but the shaft was quite a bit more yesterday and today.
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Old 02-01-2014, 09:52   #17
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Re: sail drives..like em?

And your point is??
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Old 03-01-2014, 17:29   #18
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Re: sail drives..like em?

I have always really wanted to buy this Wauquiez Gladiateur 33, but was always been warned not to buy a boat with a Saildrive.

The one on this boat is almost new and the funny thing is it looks like most of the lower units on all the many outboards I've owned and never had a problem with.

http://www.yachtworld.com/boats/1983...s#.UsdUvXoo4fS
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Old 03-01-2014, 18:06   #19
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Re: sail drives..like em?

Other reasons why I think Manufacturers like them, is flexibility with placement, more aft they can still keep the propeller wet (matters with broad stern), more fwd advantage with centering the weight. Longish saildrive gets the propeller away from the hull, makes the water flow more even, (closer to the hull the slower the water speed), also the angle of attack varies by the upwelling water alters the angle of attack between top and bottom of propeller swing. What does that mean? less noise, more bight, less aeration, maybe efficiency gain. I'd say if the manufacturer has got it right and you follow the recommended maintenance, it could be a very sweet installation.
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Old 03-01-2014, 20:10   #20
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Re: sail drives..like em?

I was dead set against sail drives when looking for my first cat 9 years ago. I had lots of experience with straight drives and really liked the simplicity. Unfortunately, I liked the Privilege 37 more than any other cats I found and decided to bite the bullet on the sail drives.

Now after 9 years with Volvo SD120 sail drives and 10's of thousands of miles on them, I have grown to like them. I never did enjoy the alignment issues on straight shafts and don't miss that job anymore. I have changed the lip seals and o-rings in my drives 3 times and it's no big deal. I just changed them 2 months ago and the bearings and races on the prop shafts looked to be in excellent condition despite being 16 yrs old. I have had no galvanic problems because I do change the zincs every 2 years.

I also changed the large rubber grommets on my drives that keeps the ocean out of the boat. That job is a big deal and involves sliding the engine forward on the mounts and removing the drive from the boat. The recommended change cycle is 7 yrs, but mine were 14 years old when I changed them and yes they really needed changing by then. That was the only serious maintenance I had to do in 9 yrs.

I also changed the sea water cooling circuit that sucked water through small holes in the saildrives (similar to outboard motor). I wasn't happy with this set-up becaues the holes were susceptible to blockage by marine growth and the intake hose was over 6ft long and created unnecessary resistance to water flow. I installed a new thru hull/seacocks in the hulls under the raw water pump. The intake hose was reduced to 18 inches and I put a plug in the sail drive. Works better and engines run cooler.
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Old 03-01-2014, 21:38   #21
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Re: sail drives..like em?

Ive always thought less was better!! Less parts less chances of failing parts! I will take a shaft drive everytime! But then I am old fashion, but it has worked for me for a long time! The few times I have driven or deliverd boats with the other type of drives I felt I was not as much in control as I am with shaft drives, they just did not seem to handle as well as a shaft drive boat ! But that just might be my lack of experince with these type of drives ! Just my 2 cents
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Old 03-01-2014, 23:30   #22
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Re: sail drives..like em?

My biggest reservation with the saildrive is corrosion, I've had many boats with shaft drives and only have had one corrosion issue, mainly due to bad electrics at the marina, lost a prop but no further damage. Saildrives on the other hand have had issues with corrosion.
Having run outboards on homebuilt hydroplanes in the past I know lower units well, which is pretty much what the business end of a sail drive is, personally I wouldn't reccomend one for a cruising yacht, for a sport boat, no problem, they get hauled regularly. A shaft drive may be more costly originally but will make up for it over the long run.
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Old 03-01-2014, 23:36   #23
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Re: sail drives..like em?

Calling them 'sail drives' was real genius, because they are 'sail drags', not sail drives.
Like slavery is the new freedom. A sailboat should have propellers that don't produce drag when sailing. But hey, they are really easy to install.
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Old 04-01-2014, 05:02   #24
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Re: sail drives..like em?

All propellers produce drag whether they are on a saildrive or a shaft drive. Saildrives have the same options for folding and feathering propellers as shaft drives. For both folding and feathering props, the drag presented by them in their lowest drag modes is proportional to their non-normal angle to the water. Since a saildrive presents them normal to the water, then they have the lowest drag on this compared to an angled shaft.

If by drag you mean the actual drive leg itself, then one needs to ask why do the fastest racing boats in the world fit saildrives instead of shafts on their boats? If they thought they could gain a fraction of a knot fitting shaft drives, you can bet they would have shaft drives.

Does anyone bashing saildrives here actually have any knowledge or real experience with them?

And not experience of the type "I was on a boat with one once and it felt funny", unless you were talking about comparison of exact boats fitted with two different drive systems.

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Old 04-01-2014, 06:40   #25
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Re: sail drives..like em?

Quote:
Originally Posted by colemj View Post
All propellers produce drag whether they are on a saildrive or a shaft drive. Saildrives have the same options for folding and feathering propellers as shaft drives. For both folding and feathering props, the drag presented by them in their lowest drag modes is proportional to their non-normal angle to the water. Since a saildrive presents them normal to the water, then they have the lowest drag on this compared to an angled shaft.

If by drag you mean the actual drive leg itself, then one needs to ask why do the fastest racing boats in the world fit saildrives instead of shafts on their boats? If they thought they could gain a fraction of a knot fitting shaft drives, you can bet they would have shaft drives.

Does anyone bashing saildrives here actually have any knowledge or real experience with them?


And not experience of the type "I was on a boat with one once and it felt funny", unless you were talking about comparison of exact boats fitted with two different drive systems.

Mark
Mark, I'm with you. Lots of pontificating without any facts or experience!

My last post shows 3-bladed prop in the folded position. The sail drives have airfoil shapes which minimize drag unlike conventional stuts or the "dead wood" mounts behind skegs or keels. I believe drag is significantly less with SDs than conventional shaft drives. Would be interested to see some real data on the drag differences.
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Old 04-01-2014, 06:54   #26
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Re: Sail Drives..Like em?

We've had cats with saildrives, shaft drives, Sonic drive leg and outboards. My favorite would be outboards my least saildrives. The negatives for Saildrives to me are corrosion, drag and the fact you have to haul out every 100 hours to properly maintain them. We also had problems with the shaft seals. The outboard and Sonic drive sit out of the water so no problems with corrosion or drag. You can also easily change the lower unit on either while in the water.
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Old 04-01-2014, 07:14   #27
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Re: Sail Drives..Like em?

Corrosion on SD's is mostly a problem with hot marinas or wiring/bonding problems on the boat. Yes, if these problems are present, then both shaft and SD's will incur damage, but the remediation will cost more for the SD.

SD's, despite common opinions, do not just fizz away when they get wet. Even when the zincs are long gone, the galvanic corrosion rate is very, very low. It would take years to corrode a saildrive through galvanic means, if even possible - they are electrically isolated from both the engine and prop and primed and coated with epoxy.

Saildrives differ in quality and maintenance periods by manufacturer. Volvo oil changes are 200hrs. Yanmar has well-known shaft seal problems (actually the shafts themselves), while this is mostly unheard of in Volvo. Same with Yanmar cone clutch models.

Both brands are now able to change oil from the inside, as well as having easily replaced split zincs that do not require pulling the prop. You can maintain these drives forever without hauling the boat.

I fail to see how a saildrive presents more drag than most shaft drives.

Your points on outboards and sonic legs are well-taken. However, they have the same advantage over shaft drives. They are also not very good solutions, if even possible or practical, for many boats. On a 10M Seawind, outboards are brilliant solutions.

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Old 04-01-2014, 07:18   #28
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Re: Sail Drives..Like em?

I have my first saildrive. The drive and motor are new and I know I will maintain them. They should last (fingers crossed). My biggest worry right now is corrosion. I had the yard do 5 coats of epoxy barrier coat and two coats of non copper bottom paint. I have never been super keen on the idea of a saildrive. When installing the drive and looking at the double seals on the technodrive, i felt a bit reassured. I also feel nice about not having a gray saildrive (or a green motor).

I have had issues with shaft drives. I was moving my old boat to it's winter storage spot upwind in 35 knots of breeze. After about 2 hours of motoring my shaft/coupler/key failed. It trashed my stuffing box and the boat began taking water. I was able to slow the leak enough with a few rags and duct tape and sailed the rest of the way with a double reefed main and blade. The thing is, I wonder if I could stop the flow of water as easily with a saildrive failure? probably not.
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Old 04-01-2014, 07:28   #29
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Re: Sail Drives..Like em?

If my dream boat came along and it was equipped with saildrives there's no doubt I would buy it. It's not a deal breaker but definetly not my first choice. I had forgotten about the huge hole cut in the bottom of the boat. I guess they are more serviceable than they used to be, but if you get some monofilament line caught on the shaft chances are its time for a haul out as your seals are probably wasted. With two similar boats, one saildrive and the other shaft drive, what would be the difference in maintainance costs?
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Old 04-01-2014, 07:28   #30
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Re: Sail Drives..Like em?

Having seen the rubber gasket/boot of my Volvo saildrives, first I'd say… wow, what a catastrophe it must be to wreck that thickness of rubber. I should think you'd have holes in the hull as well, like as in, you've run aground on a reef type stuff. Secondly, it would only take some thought to concoct a kit (similar to the idea of having bung plugs laying about) which would be capable of plugging your saildrive boot. Say, a blanket or a large beach towel. Thirdly, since I have a catamaran, I probably wouldn't sink in any case, and honestly the idea of a great huge lump of lead taking me to the bottom is far more scary to me than the saildrive aperture, and there are certainly plenty of boats carrying huge lumps of lead weight and they're doing ok :-)

…and, like cattales' pic above, we've fitted a fairing boot which is additional insurance or at least some reduction of inflow.
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