Shaft drive future?

Just a short answer on the IPS, they have much bigger ones today; http://www.volvopenta.com/volvopent...enta_ips/engine_range/Pages/engine_range.aspx

'Flybridge boats over 50 feet' isn't very specific, so any answers or opinions will be rather generalized. There's so much more involved in your question than just the pros and cons between 'pod' drives vs props on shafts.

Hull design plays a massive part in a comparison such as this. If you had a specific hull design or type in mind, any answers or opinions would be more focused to a specific application....for instance a round-bilged flybridge yacht would attract a different set of opinions to a deep V hulled yacht. Are we talking displacement, semi-displacement or planing ?

A skegged, round bilged hull would indeed prove tricky as a platform for triple 'pod' drive installation, and not just because of the skeg. A deep V hull on the other hand could accommodate a triple installation and still retain most of its 'keel'. There are infinite hull design variables in between, each with a specific set of parameters that could affect the installation, and the performance achieved.

Gyro stabilization is currently used on both shaft and 'pod' drive vessels with various hull designs for at-anchor stabilization. This has more to do with perceived comfort on board whilst consuming lobsters and Chianti than performance dynamics. Gyros are not used to achieve directional stability when moving forward with the speed potentially achieved with shaft and 'pod' drive installations... this is more the job for the hull design and the characteristics of the drive system and stern gear itself.

Deadweight / displacement of the craft in question is another aspect that will not necessarily push the decision between 'pods' and shafts. You may for instance be surprised at how the weight of an IPS installation can be identical if not more compared to a shaft one, when all the components and structural requirements are taken into account.

'Pod' drives have been proven to be more efficient in terms of max speed and fuel consumption for specific applications. However it's not as simple as assuming this is due to weight alone. The efficiency gains are first and foremost down to the propeller configuration and design. Simply put, a good 'pod' drive installation can get more of the engines crankshaft power converted into propulsive force than most shaft / submerged prop installations with similar power. This can achieve, like for like, either more speed with the same horsepower, or possibly the same speed with less horsepower. Fuel consumption can improve accordingly, depending on the power required to suit the overall design and installation package and performance envelope. Other pros and cons include the question of draft / handling /maintenance / price / serviceability etc etc. A massive topic on its own.

In general, shaft drive installations suit a multitude of current and historic hull design / displacement packages, whilst 'pod' drives work best when the hull design / displacement package is designed from the outset around the 'pod' drive characteristics. Your question as to whether 'pod' drives are the future and shaft drives are soon to be a thing of the past cannot be answered without answering first a parallel question...will all boats in the future suit all the commercial and geographical markets in the future, if they are all designed around the rather specific qualities required to optimise the benefits of a 'pod' installation ?
No. IMO, as it is today, 'pods' will continue to offer an alternative within an ever changing segment of an ever changing global market. Their share of the market will grow, but then advances in hull design, 'engines' and construction techniques may also become the topic of a similar question sometime soon. There's more to our future than just propeller efficiency.

IPS is not designed for trawler type use. It's dockside maneuverability can be handled as well and cheaper with thrusters, and it wouldn't do much (if anything) for economy. So the keel isn't really a concern. From what I hear it also sacrifices some economy in 3+ configurations. I think that the big arena where you'll be seeing the shafts disappear is in the 40'-60' cruisers, but there will always be a place for them.

So in your opinion then, two Zeus drives w/contra-rotating props would be of no particular benefit to the economy/range/maneuverability of, say, an 86-foot Nordhavn? That's disappointing news, but that's also why I post/lurk on this forum: to learn. Many thanx for your experienced input.

Whoa Cap! Where did you get this info? Just because a thru-hull mount or specific output engine hasn't been designed for a round bilge, trawler yacht installation, doesn't mean that IPS or Zeus pod systems are not adaptable. There are plenty of azimuthing systems on tugs and they are more maneuverable than conventional strut & thruster systems.

86 Nordhaven is beyond my experience, but I can't see the benefit for a 9 kt. boat. DK if anybody's even thought of trying it. Lazarra got some big boats with triple IPS and I believe 4, but they're looking for speed, high speed maneuvering, and fuel savings as well as maneuverability at the dock. Can't see what the NH would get that it can't get from conventional shaft drives with a thruster. Currently equipped: "Twin MTU Series 60 engines rated at 600 hp each spinning 48-inch propellers through 4.59 to 1 reduction gears allow a transatlantic cruising speed of 10 knots. With over 7,000 gallons of fuel aboard and throttled back to the 9 knot range, this new design can run roughly 4,000 miles before refueling."

Very interesting topic and it lead to questions, questions and more questions...

So is there a hull shape that IPS drives work best with?

I read about a wooden Huckins that had been repowered with Volvo IPS drives. Assuming increased efficiency is the goal, would IPS drives work well repowering other old classics or is that also dependant on hull type?

Finally, have hybrid diesel/electric IPS drives been developed yet? If so, would they make sense for repowering an old classic (Say a late 1950's Chris Craft Connie or a pre-war Elco) to reduce fuel consumption or would that depend on hull type and length of boat?

When it comes to hull shapes for IPS, Volvo Penta recommends the same as for sterndrives, but with not too deep V aft. But of course you can have them on most planing hulls made for shafts as well. We will probably see special IPS drives for slow going boats later on.

Diesel electric pods are common in bigger applications and I think hybrids on IPS will also come, but only for slow speeds when running electric. The benefits are that you can run quiet in harbours, the high torque at low revs is also ideal for tight manoeuvring. And just the word hybrid makes it politically correct...

I'll beat Judy to the punch here: see Cape Horn trawlers with their fully-azimuthing single drives. 10+ years ago before any IPS/Zeus stuff came out.

You know, I was going to suggest that they could go to an azipod, but he was asking about Zeus & Nordhaven and didn't want to confuse the issue or go into a subject that could be better answered by others. Azipod has different objectives and operates different than Zeus & IPS.

This is untrue, the 41' Grand Banks Europa is power by Cummins Zues drives and provides better maneuverability, and fuel economy is much improved. It also eliminates a need for a bow thruster. It has also freed up interior room due to using smaller engines.

You may have missed this:

At 19 kt cruise and 20.5 kt WOT I'd catagorize that GB as a cruiser, not a trawler.
BTW, you can put IPS/Zeus on most anything I'd imagine. It's just a matter of whether the economy is worth it. I'm sure some will opt for it to experiment or just for the maneuverability dockside, but it won't take over as the power of choice if it doesn't make financial sense.

Such is true, but economy at displacement speeds is still much improved. I think a set of pods on a true displacement boat, with the proper engines to just achieve hull speed, would still see a good amount of fuel economy over traditional props,shafts, struts, rudders hanging in the water. Also I like that everything is integrated (steering, autopilot, gears, etc) so it makes for a clean lazzarette that you can truely take advantage of for storage. Tugs and cruise ships wouldn't all be going to them if they didn't see fuel economy improvements (albeit not exactly the IPS and ZUES we are talking about.)

Just my observation, but it appears as though the push to the pod solutions (IPS or CMD Zeus) are for boats geared towards owner-operators. The big advantages appear to be ease of operation with the joysticks as well as a more compact packaging of the powertrain, allowing more living space. As mentioned earlier, this appears to be in the 40-60 foot range. Lazzara, however, is using the the pods in their later designs (75 to 120 feet).

It's a big albeit. If you look back into the IPS threads you'll see it noted quite vehemently that they are not nearly the same. As noted, the Seline is using the azipods.

From what I'm reading, the jury is still out on how the economy works out with these, but it's an interesting future we're moving towards and Lazzara seems to be leading the way in this category. Exciting.

In a PMY test from 2009 of the GB 41 and Zeus I see the economy at displacement speeds as disappointing: 10.8 knots yielding .84 nm/gal, 11.3 knots yielding .62 nm/gal.
Compared to a PMY test of a 45 Mainship with in-boards: 10.7 - .98 and 12.1 - .78.

The GB a knot faster top end (23 knots) but the Mainship more fuel efficient at any speed, at some speeds half the fuel burn.

Karl

2 different hulls designs. The Grand Banks is more of a planing hull. Displacement speed on the old Grand Banks 42's was 7.5 knots. So I'm guessing the 41's would be very close to that and very very efficient. Once you get past the displacement speed, you're pushing a lot of water until the boat is on plane.

The Mainship is most likely a lot lighter than the Grand Banks. I know that it is physically a lot smaller especially when it comes to beam. And, a different hull design........

Understand and agree but still not impressed with the fuel consumption with Zeus given the size/weight of the GB.

At 6.8 knots 2.2 nm/gal for the GB (according to PMY), at 6.4 knots 4.92 nm/gal for the Mainship (according to PMY).

Karl