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Shaft drive future?

Discussion in 'Technical Discussion' started by traveller, May 8, 2011.

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  1. yr2012

    yr2012 New Member

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    I'm looking over some new designs by Erwin Gerards http://egyachtdesigns.com who is doing work for Release Boatworks. They are using 480 Cummins with ZF drives but setting them about 10-12 ft apart. The drive is at the stern, but the engine is up at the cockpit. It is my understanding that ZF is making the Zeus drives for Cummins.
  2. AMG

    AMG YF Moderator

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    This is the same as with IPS in sportfish boats (with a cockpit) and also when you replace shaft installations with pods. Another application is with triple engines where the one in the middle can be forward of the other two for better access. It all depends on what boat it is.
  3. NYCAP123

    NYCAP123 Senior Member

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    One nice thing with IPS (and I assume with Zeus although I'm not as familiar with them) is that you can mount the engines pretty much anywhere you need to put them for weight distribution and run a log or short shaft back to the IPS drive unit.
  4. yr2012

    yr2012 New Member

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    IMHO - you really shouldn't have all the weight in the stern. The boat designer and builder need to cooperate to trim the boat properly.
  5. NYCAP123

    NYCAP123 Senior Member

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    Agreed, but it can be very nice to move the props back if you can have the engine weight forward. That co-ordination between everyone is imperrative.
  6. Capt J

    Capt J Senior Member

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    Actually the biggest advantage in regards to that is in a sportfish design. You can have more room under the cockpit for fish boxes and storage and such by having the engines foward, if the boat is built around the pods.
  7. motoryachtbill

    motoryachtbill New Member

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    Pods

    As I walk around boat yards I see them off of newer boats alot. I hear good things about the the service from most owners I have met, but they wish they did not have the problems to start with. Time will tell.
  8. Kafue

    Kafue Senior Member

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    The OP asked if the future of the old fashioned shaft and propellers was over in view of the new technology.
    So far most the posts regard the professional views on the most effective NEW systems IPS, Zeus, and hull design, boat length, HP versus length etc.
    Well, IMHO as an owner/operator of enough boats for enough years, a major issue is always maintenance costs of the new technologies. Yes, fuel economy seems to be better with pods, IPS, Zeus etc, but fuel is mostly NOT the major annual cost.
    With all the new technologies, the annual service costs can be staggering in comparison to simple reliable systems.
    Okay, the ease of use with the “joystick” docking and the wonderful application of being able to keep your vessel in the same exact position while in the ocean, fuel economy, space etc.
    It may be so wonderful when you have to moor on a windy day but wait for the bill you get when something goes wrong, and it WILL.
    I well remember the service cost I had when I owned a beautiful Italian boat with the latest electronic MAN engines!
    I soon forgot how great it felt when I pushed those throttles to the max and the turbos kicked in and I could feel the power as the boat surged to 40 knots.
    Then later the first problems arose. Electronic engines=technicians/engineers/mechanics to fix=$$$$$$’s and worst of all I had NO idea what they were telling me had just been repaired for these incredible costs. BTW, some items were still under warranty, luckily.
    I sold this boat before the warranty ran out.
    I am not saying avoid the new technologies. However, be aware of the whole issue when you embrace it.
    If you are the Skipper, Engineer, crew etc, well, different story.
    Owner/operator and it is so different. The less gear in the water the better. I’ll stick to 2 shafts, 2 props and worry about them not hitting the bottom over all that technology being attacked 24/7.
  9. NYCAP123

    NYCAP123 Senior Member

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    Kafue, you're taking the long (smart) view. Unfortunately, most people today think no further ahead than a flea. (Just look at our phones). The new toys are expensive, but that is spread out over 20 years, so most see it as only a couple of extra dollars per month. Future maintenance and repair costs are beyond most people's ability to comprehend. What they see is the immediate perks (ease of use and fuel savings). Plus, it's easy to rationalize that the fuel savings will off-set the future costs. I recently picked up a boat with Yanmars for a client. Those motors will only last maybe 2,000 hours. But we just had our 2nd fuel stop and computed their average fuel burn at 11gph (probably about 23gph @ cruise). 2,000 hours is 10 years away, and will probably be the next owner's problem. Those fuel savings are now. I don't see either technology disappearing, but what saves fuel will certainly continue to take more market share.
  10. Bill106

    Bill106 Senior Member

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    If, as I suspect, the OP was referring to sportfighing flybridge boats, there is one design aspect of pod propulsion that is causing problems with boats in this size range and that is the height of the drive unit itself. Engine height is also a big concern but jackshafting and moving them forward can alleviate that issue but it also removes one of the pod's benefits of freeing up interior volume.

    A VERY important design feature of a sportfish boat is having a cockpit low to the waterline to facilitate handling fish at boatside. Boats that have cockpits high above the waterline are shunned by crews and owners alike, at least here on the US east coast. The current size of the "smaller" pods units (under 600hp) necessitate using 3 or more units to achieve the normal speeds but that creates engine access problems. The soon to be released larger pods capable of handling over 1000 hp engines will help the engine access problems and allow a simpler setup of twins but they are so tall (based on preliminary drawings), they will not fit under most cockpit decks I am familiar with.

    While I am a huge fan of pod drives I just don't see them replacing conventional shaft systems on sportfish boats until they can get the drive height down considerably but I know they are working on it so maybe it won't be long.
  11. K1W1

    K1W1 Senior Member

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    Hi,

    Shafts are pretty basic and generally reliable, a damaged one can sometimes be straightened, re built or re made by some pretty simple machinery in the right hands.

    Pods on the other hand are a lot more complex piece of machinery, when they have problems they are generally big expensive problems. This applies equally to the big Pods used on commercial ships and from what I read about the smaller ones.

    Having said all that the simple shaft and submerged propeller can still take a lot of TLC and cause an elevated blood pressure problem for those who use them and have problems only to be told by the warranty dept that you don't.

    By this I mean there are a number of largish yachts out there with Oil Filled Stern Tubes, these are made by a few manufacturers so the choice of whose to use is not as large as one might imagine.

    Even with all the Technical Might of some of these manufacturers working away diligently to come up with a system that will offer long life and reliable operation the holy grail of achieving this seem to elude most if not all of them.

    One type has a small leak off tank that is connected to a space between the three seals at the aft end of the Stern Tube, these are nearly always filled with an Oily Water mixture and when things get really bad have to either be emptied every few hours or just let over flow into the bilge. The only way to change the oil on these babies is haulout or underway, Doing it underway can be a bit nerve racking as you have to remove the oil that comes out of the tube back to the header tank all the while topping up the feed side with new oil. It is not a job attempted solely by the OOW in the ER at 0300 as none I have ever met has enough hands or orifices alone to hold all the bits and pieces required to do this. These ones use a water soluble oil.

    Others have a charge of Lube Oil yes that's right the same stuff you use in your engines, great to know that you can be done for polluting the sea if it leaks underway isn't it.

    Some of them leak badly from day one oil out and or water in.

    Some of them have one side that leaks at certain revs and is fine at other speeds.

    There is my rant for the day :)
  12. Marmot

    Marmot Senior Member

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    I just wish everyone would stop calling these outdrive things "pods" because they are not a "podded propulsor." They are Z drives or azimuthing drives but they are not pods.

    There is no motor, electric or hydraulic, in the things. They are just a glorified version of an I/O drive that marketing types love to have people think are some kind of cutting edge propulsion unit when in reality they are no more than a consumer quality version of the Z-drives that tugs have been using for years.
  13. CODOG

    CODOG Senior Member

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    :) I'm 'afraid' its too late....the 'term' 'pod drive' has already become an 'accepted' 'group heading' for these 'things'....even for those, like me, who spend the time typing inverted commas when it would be just as quick to type a more precise description.
    The term is after all immediately recognised as being rather different to 'shaft drive' without having to complicate the issue. Sometimes that is all the information needed, to spark a thread, or to sign a sale.
    These days, the debate is over I-Drives vs Z-Drives or C-Drives, azimuthing or otherwise....Previously, we've deliberated over the choices between I-Drives, V-Drives and U-Drives. One day one of our RNLI friends got bored and used both I-Drive and V-Drive in the same boat. The odd S-Drive has pierced the surface every now and again, and one or two ferocious ally cats employed a very unusual L-Drive. I look forward to the opportunity of looking at a YY-Drive one day, perhaps combined with WJ+S-Drive. Shame I wont live long enough to debate the merits of ION-Drive, but I'm sure even then that 'shafts' will still enjoy a large market sector.
  14. NYCAP123

    NYCAP123 Senior Member

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    He's right. 1st of all, the definition of "pod" doesn't bear out your thinking. Not only doesn't a pod need to contain a motor, it can be empty or filled with anything. 2nd, if you Google "Pod drive" the type you refer to is pretty far down the list way behind Zeus and IPS. It's symantics. if you're in a commercial yard and say pod drive they'll instantly think of your item, but in a marina or recreational setting it will be the last thing on anyones mind. If someone goes to the wrong yard to place an order, wow will they be surprised and get what they deserve.:D Hey, horsepower once meant a team of horses (and still does on some ranches), but has a whole different use today. Pod drive is here to stay in referring to both types plus whatever comes next.