Correction to Earlier Posts on Oil Condensation

[Roger Long]

Since the initial drying out of my engine after the installation of the new head gasket, I have not seen a hint of moisture in the crankcase breather trap. Things I said last spring and summer about the water I was seeing demonstrating how much moisture diesel engines generate from blow by on start up were wrong.

The moisture I was seeing was the first indication of seepage from the failing head gasket. I think this alone is sufficient value to have one of these installed (as long as you remove the filter element) aside from diverting oil that will otherwise end up coating the intake manifold and making smoke.

Another thing I have learned recently about my engine is that there is a lot of blow by, as seen by outflow from the oil filler cap when it is removed, at idle. It drops off to almost nothing at cruise speed. The effect may be exaggerated by the extreme installation angle of my engine but I think this shows one of the reasons why prolonged idling for the purpose of charging batteries and refrigeration is hard on engines.

 

[sea_casper]

The effect may be exaggerated by the extreme installation angle of my engine but I think this shows one of the reasons why prolonged idling for the purpose of charging batteries and refrigeration is hard on engines.

How long will it be before engine manufactures design engines to meet the way they are actually used by the customer? Most everybody with sailboats, too small to have a genset, use their engines to charge their batteries, electricity utilization on boats has gone up, especially in the last ten years, and that trend will continue as us baby boomers demand some comfort while cruising.

Why are engines still canted to match prop shaft angles, why hasn't automotive CV joint technology been adopted, at least? Newer boats are evolving to sail drive setups but perhaps diesel/electric is the way to go for re-powering sailboats of all sizes.

 

[Stu Jackson]

Newer boats are evolving to sail drive setups...

Worst idea of them all. I wouldn't want a huge hole in the bottom of my boat that requires regular maintenance including the all important seals. A stern tube and a stuffing box are far simpler and safer, IMHO.

As far as Roger's "engine angle" he's already discussed that and noted it is way more extreme than almost any and all others.

 

[xcyz]

I for one am interested in knowing just what that angle is.

Roger, can you share that with us? I haven't been able to find it in any of the older postings. Perhaps a picture as well?

Thanks

 

[kloudie1]

I definitely agree with Stu re saildrives..
Shaft angle/engine angle.. I'll bet most of those are design "Ohhhh sh$$%*" meaning that the specified engine with a high angle output on the transmission couldn't be sourced at the last minute .. or got to be too expensive ..
There are a lot of Endeavour 32's around I've not heard of this problem but I'll bet all of 'em that I know about have never been operated like Roger's.. I designed a couple of mud drives for duck boats that used CV joints to get the engine level .. It worked fine but required some custom machining to make the bits work together.. Would be expensive for a boat builder to undertake.. Most builders are at the mercy of the engine vendors because the builders can't afford to have a proper power-train engineer work the issues.. also why the sail drives are becoming much more common.. The builder has to only supply a hole in the bottom and some plain platform mounts..no worries with how strong the beds have to be and what angle they have to be installed .. and prop clearance and strut mounting ... and shaft sealing ... etc..
EDIT: I believe a well made saildrive would be a fine piece, however.. If the drive were made of a non corroding material like one of the strong engineering plastics and if it were set up to be serviced from the engine room without having to pull the boat.. and had a pressurizing oil standpipe so that seawater could not seep into the lower gear even if a seal started failing..reinforced Viton for the diaphragms.. No one seems to be interested in doing those improvements..

 

[Bill Roosa]

You could always us a hydraulic pump and motor!
You could place the engine where it would help stability or make maintenance easy and put the motor in "just the right place" (they are quite small for a 50 HP motor) to give the prop shaft a nice horizontal line of thrust.
Then you could put another motor (and valves to control it) where ever you wanted and power a genset........and jib furler, and winches, and windlass......
things that make you go "hummmmm"

 

[anchorclanker]

How long will it be before engine manufactures design engines to meet the way they are actually used by the customer? Most everybody with sailboats, too small to have a genset, use their engines to charge their batteries, electricity utilization on boats has gone up, especially in the last ten years, and that trend will continue as us baby boomers demand some comfort while cruising.

Why are engines still canted to match prop shaft angles, why hasn't automotive CV joint technology been adopted, at least? Newer boats are evolving to sail drive setups but perhaps diesel/electric is the way to go for re-powering sailboats of all sizes.

Diesel electric is no where near as efficient as direct drive. And a CV joint also takes power to operate, increasing in power as the angle increases. The only reason trains are diesel electric is to be able to operate as smoothly as possible. Shifting gears in a locomotive would be a very scary thing to consider. There are no gears or other great power losses in a directly driven propeller, and its the most efficient design possible. The angle isnt great enough to be a factor worth considering.

 

[Bill Roosa]

It is also kinda hard to make a 50 HP motor (designed to move the boat) work efficiently when it is driving a 3 HP alternator (at anchor) no matter what type of drive system you have.

 

[Tom J]

Diesel electric is no where near as efficient as direct drive. And a CV joint also takes power to operate, increasing in power as the angle increases. The only reason trains are diesel electric is to be able to operate as smoothly as possible. Shifting gears in a locomotive would be a very scary thing to consider. There are no gears or other great power losses in a directly driven propeller, and its the most efficient design possible. The angle isnt great enough to be a factor worth considering.

Yeah, but wouldn't it be great to have that heavy little motor down low in the middle of the boat, or any where else you'd like, where maybe it would be easy to get to?

 

[Roger Long]

Yeah, but wouldn't it be great to have that heavy little motor down low in the middle of the boat, or any where else you'd like, where maybe it would be easy to get to?

It can, and has, been done. This schooner I designed first had twin screws with hydraulic motors driving the props. They were more efficient and sophisticated than the usual hydraulic motor, having been developed to move the control surfaces on the Saturn moon rocket and were being marketed for marine use.

It didn't work out that well because the twin props were too close together to exert any turning force with differential "throttling" of the motors or even putting one in forward andone in reversed. Without prop wash over the rudder, there wasn't as much control under power as usual.

My primary reason for the arrangement, to avoid having a hole in the rudder which creates drag and reduces steering effectiveness, was considered secondary to having more control in the tight marina where the boat was kept. Eventually, a conventional aperture was cut in and a new engine with a solid shaft installed.

Back in the 1970, liveaboard silversmith John Lewis of Boston installed a hydraulic drive in his British cutter Rose which can still be seen in Boston. I don't remember what he used for a motor but the Volvo diesel was tucked up into a cockpit seat locker which opened up a lot of useful space down below where the engine originally was. As far as I know, that installation was entirely satisfactory although it makes the effective price of diesel fuel 20 - 50 percent higher depending on the quality of the hydraulic components used.

 

[kloudie1]

Yup.. One of the big catamaran producers today uses one diesel engine driving a hydraulic motor in each hull.. Probably one of the best applications I've seen..

 

[Captandrew]

Why are engines still canted to match prop shaft angles, why hasn't automotive CV joint technology been adopted, at least?

I have just returned from a delivering an 1983 Irwin 52 that has exactly that. The engine is mounted horizontally and there is a universal joint to the shaft. I believe that all the larger Irwins have this feature.

 

[sea_casper]

Diesel electric is no where near as efficient as direct drive. And a CV joint also takes power to operate, increasing in power as the angle increases. The only reason trains are diesel electric is to be able to operate as smoothly as possible. Shifting gears in a locomotive would be a very scary thing to consider. There are no gears or other great power losses in a directly driven propeller, and its the most efficient design possible. The angle isnt great enough to be a factor worth considering.

I prefer not to hijack this thread, on this forum, but will debate on the "Engines and Propulsion Forum", where I am prepared to back up my opinions with facts and figures and not feelings and opinions on Diesel/Electric efficiency, CV joint losses, sail drive versus angled shaft, gears vs direct drive, and how that effects "the most efficient design possible".

 

[anchorclanker]

Nothing to debate. Simple physics. Anytime energy is transfered, energy is lost in the form of heat. If its using power, its using energy, and if its using energy its using fuel and is therefore less efficient. Period. But your certainly free to start a thread there to debate it if you like.

 

[Roger Long]

The engine is mounted horizontI believe that all the larger Irwins have this feature.

"U" joint or CV joint? A single universal joint or a pair in which the shafts before and after the joints are not parallel will do terrible things to your transmission over time and can even break the shaft due to fatigue. Ask the Clearwater folks who have left a few props in the mud over the years.

CV stands for "Constant Velocity". The simple universal joint speeds up and slows down the shaft it is turning. By using two and keeping the input and output shafts parallel, the effect is canceled out. Imagine the strains trying to speed up and slow down a prop every revolution.

Only CV joints can be reliably used in a prop application unless the purpose it to only raise or lower the engine and not change it's angle relative to the propeller shaft.

BTW the last research vessel I designed does have a Carden shaft, two "U" joints with a splined drive shaft between, but it is simply to lower the engines since the water jets are higher in the stern.

I designed another research vessel with CV joints in the drive train back in 1984 while VP of another firm.

 

[sea_casper]

Nothing to debate. Simple physics. Anytime energy is transfered, energy is lost in the form of heat. If its using power, its using energy, and if its using energy its using fuel and is therefore less efficient. Period.

An appropriately sized CV Joint would use less power, than a misadjusted stuffing box, or a misaligned engine/propshaft.

From Wikipedia, Constant-velocity joints (aka homokinetic or CV joints) allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play.

 

[Captandrew]

"U" joint or CV joint? A single universal joint or a pair in which the shafts before and after the joints are not parallel will do terrible things to your transmission over time and can even break the shaft due to fatigue. Ask the Clearwater folks who have left a few props in the mud over the years.

CV stands for "Constant Velocity". The simple universal joint speeds up and slows down the shaft it is turning. By using two and keeping the input and output shafts parallel, the effect is canceled out. Imagine the strains trying to speed up and slow down a prop every revolution.

Only CV joints can be reliably used in a prop application unless the purpose it to only raise or lower the engine and not change it's angle relative to the propeller shaft.

HMMM! now you have me thinking. The joint in question was just like the joint under my car, which I have always called a Universal joint but others have often called a CV joint.
In any case the problems I had came from the missing blade on the prop not the joint. And the joint had been running since 1983 quite successfully.

It was essentially like this.

 

[Roger Long]

I have always called a Universal joint but others have often called a CV joint.

That is a Universal Joint. A CV joint is different (see animated picture in post above). U joints must always be used in pairs as they are in car real wheel drive trains. CV joints are used in front wheel cars because the shafts can not be parallel.

If the prop shaft is large enough, the stresses of the changes in rotational speed with improper "U" joint installation may never cause a problem. You may never know that your gear teeth wore out a few hundred hours sooner than the might have.

It's hard to know ahead of time though if a single U joint or U joints used with non parallel shafts will cause a problem.

It's possible you lost your prop blade because of fatigue created by the speeding up and slowing down.

 

[Captandrew]

Truthfully Roger I believe that the blade fractured after a period of electrolysis and perhaps a strike of some kind, though I cannot imagine what. The prop was a high tech folding prop and was relatively new. It is now with the owner and the manufacturer of the prop to sort it out. The previous and current (again) fixed prop had given many years of trouble free service. The break looked almost identical to yours, last year.