Why aren't sail drives more common ?

[rslifkin]

Some friends had their season interrupted for a while due to fishing line getting wound into the seals of the IPS pods on their Palm Beach.

The efficiency and how flat their boat runs is really remarkable compared to the tsunami of a wake we tend throw with the inboard props on our EB47.

But when I ding a wheel it's only a few hundred dollars to have the pulled and turned. I never asked what the pod adventure cost them.

That could be as much due to differences in hull design as drive system.

 

[Art]

Dyslexia conquer the boating industry?

Folks, regarding shaft/prop position on a boat "Angle of the dangle is directly proportional to the hypotenuse of the triangle."

In other words... shaft-props coming out of boat bottom in a "down" angle should tend to push the bow downward, not upward.

Therefore: Hull design [and load-trim factors] are the culprit for boats that have bow high and transom down while cruising. Trim tabs can help overcome a boat's hull design and trim factors "angle of the dangle"!

 

[Benthic2]

The boat I saw them on had twin keels to protect the drives and also had traditional rudders. The drives did not pivot like pods or IPS.

 

[ben2go]

Saildrives have to be completely isolated from the engine to prevent corrosion. It's a big deal in salt water or they will eat themselves fairly quickly. I've seen them completely gone from mid leg down on some boats that were pulled out of the water. Mads talks about the issue in his video.

 

[CarlF]

The other poster was right that the majority of sailing cats use twin sail drives. The biggest you can go is about 100hp with a 20" prop. These all have separate rudders.

You have to pay attention to the corrosion risk. But thousands of these boats have been in the water for many years with very few corrosion issues - and those were usually due to poor practice/maintenance by the owner.

As to reliability, you have to remember that the sail drive replaces the transmission, shaft, stuffing box, and cutlass bearing - all of which are common problem areas on conventional shaft boats. I'm not sure there's really a big difference.

IPS drives are a different beast - I don't have any experience with them.

 

[Brooksie]

Because they embody all the bad features of both outboards and outdrives and none of the good ones.

 

[ProMaritime]

Wow Benthic2 did you ever get the straight word on sail drives. Almost unanimously junk. Only one poster had anything moderately good to say about them.

These things should should be relegated to trailer boats and should be pulled out of the water after every few hours of use or else they will turn into aluminum oxide in short order. Hit anything even slightly solid and you will have a big hole in the bottom of your boat. Builders should require that they be mounted behind a water-tight rear collision bulk head to keep the boat from sinking if something is hit.

The Volvo forward facing, counter rotating system is even worse in my opinion.

 

[diver dave]

My 15 y/o saildrive was just surveyed. No detectable corrosion, with original paint still under the AF paint and oil analysis normal. Clearly an act of God at work, but i will take it. 100 % salt. And engine with little rust as well, thanks to no stuffing box aerosoling the ER with sodium chloride.

 

[psneeld]

Buddy has 2 on his 12 year old sailing cat. His rig is so tall he spends most of his time offshore as he can't fit under many bridges including all the ICW ones. Also spend all year in salt water.

Hasn't had any corrosion issues I am aware of and does spend a fair time of motoring.

Many aluminum issues in salt water I think have been overcome through many engineering advances in the last 2 decades.

 

[Hippocampus]

Saildrives may produces less parasitic drag, are cheaper for the builder and maybe more efficient in some settings but risk with catastrophic failure is more severe. . Water intrusion into the drive and worse of all failures of drive/hull seal. Even an exposed shaft, strut and screw is less of a danger striking debris than a sail drive. Water intrusion and you end up with no power train. Fine for racing sailboats. Not good for a cruising boat either power or sail.

 

[diver dave]

Mine r above and behind the rudder and keels.

 

[DDW]

For all the predictions of disaster above, there are literally tens of thousands, and probably more than a hundred thousand, of these drives installed in sailboats. Starting more than 40 years ago. In theory they can sink a boat, but instances of the latter are extremely rare, much more so than the number of leaking shaft logs sinking boats. They can corrode, and yet replacements are not frequent and actually somewhat rare.

So while you'all may not like the idea, the proven track record does not support the predictions of doom. The one on my sailboat now 12 years old with zero issues. Never had a shaft log drive that long without issues. Leaking seals, scored shafts, loose cutlass bearings are among the problems eliminated. If they would only make the saildrive leg from bronze or SS, it would be better than a shaft in almost every way.

 

[diver dave]

Another curious “advantage” is the RW seacock is just above the waterline. I dont make it a routine turn off. In addition, there are several water pickup points. I think even a plastic bag may have difficulty blocking much water flow

 

[Jeff F]

I think much of the bad rep on these in North America comes from the early units from OMC and Volvo in the 1970s. They didn't have great track records, and parts got scarce.

I have a Yanmar saildrive on my sailboat. Happy to have it. These are well proven units.

 

[Hippocampus]

Yes single engine sailboats have them behind the keel where they are well protected. Still, have acquaintances on cats where one was struck requiring an urgent haul out. Yes, like dripless shaft seals much talk of catastrophic failure but little seen. But have heard of more expensive repairs with entanglement than with a standard set up. Admittedly, my limited knowledge is with small units which often have folding props used behind high aspect deep keeled sail boats or small twins on multihulls placed way aft. However, on mono hull power they present another issue. The farther aft you place a heavy engine the more you’ll have difficulty getting a decent gyradius. The more weight near the ends the more difficulty designing in a decent ride. There been multiple reports in sailboats where engine access had been quite problematic when at sea. For safety’s sake the sail drive/engine installation is aft with a watertight bulkhead just forward of it. Access is only via a hatch. In a seaway this presents a down flooding risk. Boats have been abandoned when this has occurred. Admittedly, this is rare but is not a problem with conventional steering and engine set ups. So for nearshore boats that are seasonal hauled with the units rigorously following service schedules perhaps risk is minimal. But for power seaboats a conventional shaft avoids all these complexities and risks. I’d rather deal with alignment and cutless bearing(s) which are serviced when the bottom paint is renewed.

 

[psneeld]

Design and compromise.....sounds like all aspects of just about anything.

Anything can have negatives, pros can outweigh them. So in some boats as long as the corrosion issues are low, and in a proper design layout...pros can win.

 

[Art]

Mine r above and behind the rudder and keels.

Photos of boat and drive??

 

[diver dave]

I will try. Been driving her 8 hour days since sat.

 

[ak-guy]

I don't know about ships in general but azimuth drives are common in the cruise ship industry. They are electric so the drive has a electric motor in it. I would think this would be great in a small application. You eliminate the complicated mechanical transfer of power to the prop. Very small options are available for a few hp.

 

[Hippocampus]

https://www.zeelander.com/

Look at the Volvo ips system in these boats. Not electric but a big step up in handling from a simple sail drive at the expense of added complexity. Props lead not follow. More efficient but more exposed.