IPS Engines and bigger boats

[Imperial One]

Following on from Dakas comments about the MBY IPS article I got to thinking about these engines and our own experience of them. Here are a couple of photo's I thought might be of interest to some forumites of one of our 20m boats fitted with 4 x IPS 600 (4x435hp) drives.
It was actually Volvo who recommended this option as opposed to 2 x bigger units. The owner is delighted with the performance of the boat - over 30 knots and the fuel economy is very low indeed. Certainly much better than his previous shaft drive boats. Interestingly, the owner has been told by an engineer that the fuel usage computer displays are "estimating" the fuel rate used and are apparently based on a sports boat usage He kept a note of the gauge readout figures and when he filled the tanks up it took about 20% less than he expected to fill the tanks!
That aside, when the power is delivered very smoothly and she runs extremely quietly at all speed ranges. Our talks with Volvo and subsequent experience have shown that these multiple installations do work very well. On our larger boats, like the 23m Flybridge, we are fitting three larger IPS units with equally good results. Apart from the very easy handling, the real spin off is the engine room is right aft and that gives huge additional space forward for other use and an added benefit of over 2m standing height in the engine room as in the second photo.

 

[BartW]

While I'am a big fan of twin engined boats, compared to a single engine,
I have never understood the logic behind a quad engine boat,

more wear and tear, more drag, more sophisticated controll systems, more maintenance,
and I can see only one benefit, more usefull space, but even that benefit is small when you compare with V-drives

can you explain or tell me if I'm missing something ?

 

[rafiki_]

Bart,

The benefit for the boat builder is the space that is freed-up when fitting IPS or stern-drive powertrains. As a result a much bigger master cabin can be built, as you don't have to package the larger engines and shafts. This gives a bigger showroom or boatshow WOW factor.

The builder will also quote periferal benefits for IPS and some sterndrives with vectoring of the drives, giving advantages for close manouevering. Efficiency is better, as the props are at a better angle, and no need for rudders, that cause drag, so fuel consumption is reduced.

Of course, these systems are mechanically, and electronically more complex, with higher maintenance costs. The builder isn't concerned, as he does not see this cost.

We are seeing more and more sub 45 feet boats with IPS or sterndrives because of the packaging benefits.

Still, when you have an ocean liner like Blue Angel, packaging is less of an issue?

 

[BartW]

Bart,

The benefit for the boat builder is the space that is freed-up when fitting IPS or stern-drive powertrains. As a result a much bigger master cabin can be built, as you don't have to package the larger engines and shafts. This gives a bigger showroom or boatshow WOW factor.

The builder will also quote periferal benefits for IPS and some sterndrives with vectoring of the drives, giving advantages for close manouevering. Efficiency is better, as the props are at a better angle, and no need for rudders, that cause drag, so fuel consumption is reduced.

Of course, these systems are mechanically, and electronically more complex, with higher maintenance costs. The builder isn't concerned, as he does not see this cost.

We are seeing more and more sub 45 feet boats with IPS or sterndrives because of the packaging benefits.

Still, when you have an ocean liner like Blue Angel, packaging is less of an issue?

well actually I was (still am) a fan of pod drives for the reasons you mention,
also some modern big cruise and cargo ships use pod drives,

but I'm wondering about the quad configuration, I think the benifit of efficiency is lost by the extra drag,
and space can be equalled with a twin shaft drive on V-drives ?
or recently, some bigger pod drives became available ?

 

[rafiki_]

Bart, I think there is a limit at the moment on the torque that the IPS and Merc systems can accommodate. I guess these will grow with time, but not yet.

 

[Deleted User YDKXO]

While I'am a big fan of twin engined boats, compared to a single engine,
I have never understood the logic behind a quad engine boat,

more wear and tear, more drag, more sophisticated controll systems, more maintenance,
and I can see only one benefit, more usefull space, but even that benefit is small when you compare with V-drives

can you explain or tell me if I'm missing something ?

No, I agree with you. A quad IPS boat is going to be a maintenance nightmare for the second and subsequent owners of this boat and for that reason alone, it might be difficult to sell on the secondhand market. I'm also interested to know how the weight of 4 engines + drives affects the trim of the boat

 

[Imperial One]

Hi all,
Thanks for the very good points and questions raised. I will try to answer them.
Van der Valk have a long history of working with Volvo and their new engines. We were I believe the first yard to have a pair of the D9 500hp on trial to see how they went before general release and these were put into Mr van der Valks own boat so there were no clients used as guinea pigs!
When the quad drive boat was originally specified we spoke to Volvo who said that he bigger engines were OK but that they thought the boat would be better suited to a quad installation. It proved correct and the boat trims very flat naturally, so hardly any trim input is needed. This would indicate that the weight of the 4 engines is not an issue.
Recently, the larger IPS drives have proved to be stable and hence we are now fitting these more often. We do still offer shafts and V drives if a client prefers and on our Continental 1 Steel models, the smaller shaft drive engines make perfect sense.
We have not seen any problem selling pre-owned multiple engined boats as the ease of use of the IPS systems does seem to be a real plus for many owners who can now cruise short handed or even single handed.
As Bart said, many if not most, modern cruise ships use pod drive systems for the same reasons of easy handling. The drag caused by a shaft, prop and rudder is considerable and all our experience shows that he IPS boats are very economical compared to traditional shaft systems and in truth they seem to have a greater speed ability on the same hull, so the drag must be less.
I am not a Naval Architect, just a humble Boat dealer who loves his product so cannot comment with any degree of authority on the issue. But, the facts do seem to speak for themselves.
MBY are due to test the current 23m triple engined boat shortly so hopefully they will have some input in a future issue of the magazine. Engine room photo attached. It will be interesting to see what comes out of the test both speed, acceleration and consumption wise.....although on this point I refer you to my OP where it seems the usage gauge may not be entirely accurate and give an over assessment of actual use.

 

[rafiki_]

yes, very tidy installation.

 

[Neil_Y]

Very nice but as yet you can't fit a decent rope cutter to an IPS! we could adapt the outboard quicKutter but Volvo have shown little interest to date.

If one unit fails can you drive home with full power on what is left?

On the losses there are also added transmission losses with IPS as there are extra gears and changes of shaft direction, these aren't ever mentioned. They are also quite wide when compared to a shaft/P bracket. I'd like a Naval architect to give an opinion on actual data and not read material produced by Volvo.

Nice boats and good marketing though

Interestingly we had similar or better efficiencies using Seatorque drives on a twin 2000hp 70' boat, around 6-8% over trad shafts. Very simple and nothing to go wrong. This comparison was with the same boat.

The trouble with all the comparisons/and data is I don't think IPS units have been exchanged for shafts on the same hull and every vessel/hull shape is different. It would be pretty involved but that would be interesting. Maybe IPC have a few 00,000 in their gear test budget?

The big benefit is to the boat builders and I think Volvo marketing has helped Joe public the buyer believe they are the best option, I'm still not so sure, even though they are very nice pieces of engineering and electronics.

 

[Imperial One]

Rafikki,
Thank you for your kind comment Sir, most generous of you.

The trouble with all the comparisons is I don't think IPS units have been exchanged for shafts on the same hull and every vessel/hull shape is different. It would be pretty involved but that would be interesting. Maybe IPC have a few 00,000 in their gear test budget?

Neil_Y,
We used the same hull with both shafts and IPS - it was much better with the IPS drives. So, sorry to say but it has been done - by Van der Valk - there we go ground breaking again!

 

[MapisM]

Interestingly, the owner has been told by an engineer that the fuel usage computer displays are "estimating" the fuel rate used and are apparently based on a sports boat usage He kept a note of the gauge readout figures and when he filled the tanks up it took about 20% less than he expected to fill the tanks!

I heard other boaters with VP engines reporting that the actual fuel burn is significantly lower (10% being already significant imho - even more so for 20% of course).
But I always thought that it was just a matter of having set the algorythm with a degree of caution.
And after reading what you're reporting, I still tend to trust more my own guess, because the explanation given by that engineer doesn't hold water at all.

Just think about it: the electronic of modern engines can sense the engine load at any given moment/RPM. Such load can vary of course depending on each hull, but even for the same hull the load is not driven just by the throttle/RPM. There are different parameters to consider, like the boat load (fuel, water, etc.), to start with. And also the sea conditions: climbing or descending a wave does make a difference!
The ECU can take all that into account dynamically, deciding how much fuel the injectors must squeeze into the engine at any given second.
With such fine details available, why on earth the fuel burn should be "estimated" on the basis of some standards?
That would be like having a cray computer already up and running and use a mobile phone to make a rather tricky calculation...
If VP would have programmed their ECUs in the way that engineer described (and I don't think they did), that would be a very poor show in technical terms!

 

[Imperial One]

I agree with you and the report from the engineer certainly does need further investigation - but who to ask for a truthful answer?
The boats owner was already very happy with the economy of the boat during his first two years of ownership and was calculating this fill up quantity based on what the gauges were telling him he was using on the voyage.
He was surprised to find that the estimate of fuel used was somewhat higher than actual and was most pleased with this......who wouldn't be?
He questioned the VP engineer on next service and was told as I reported.
OK so it is second hand but it is from an owner who is a most fastidious record keeper.

One thing is for sure, all the IPS powered boat owners report good economy compared with shafts.

 

[Bajansailor]

Re the photograph in your original post showing the four engine installation - how much room is there for access / maintenance between the engines?
Can an average girth person get between them, or do you have to be very skinny?

The access on the 23m with the triple engine installation looks like you have much more room available.

 

[MapisM]

but who to ask for a truthful answer?

Good point, I actually don't know.
I have a good technical contact with Cat, but none with VP.
Maybe I'll ask that Cat engineer anyway, the next time I talk to him.
He probably will not have a "truthful" answer specific for VP, but he surely knows how these instruments work in principle.
And of course, we're not talking of rocket science, which can be known to just one builder and not to another one...

 

[Imperial One]

Thanks MapisM. It would be interesting to hear what he thinks. My bet is they are/were just showing an odd reading even though it was on the high side as opposed to the (more expected) low side!
I don't suppose any VP engineers will stick their necks out in public anyway......will they?

 

[penfold]

Presumably if it's a fully automatic digital engine control system, the fuel estimation will be calculated from the 'on' signal sent to the injector pump/fuel rail and the nominal flow of the injectors as designed; that's how the Cummins QSB system was explained to me, it estimates the usage rather than measures it with flow meters, unless the injectors/pump are knackered the estimate should be pretty accurate.

 

[Imperial One]

Maybe it is something to do with the fact that a diesel pump always puts more fuel down the lines than needed and the unused fuel gets returned to the tanks. Perhaps the gauges are measuring pumped fuel as opposed to used fuel?
Irrespective of the reason, one thing is certain, the IPS engines are seemingly very much more fuel economic than shaft drives seem.....even when double the number of engines are used.

 

[Bajansailor]

Originally Posted by Imperial One
"but who to ask for a truthful answer?"

Re my query above about access in that quad engine layout shown in the photo earlier?
It does all look very neat and tidy, but also diabolical to work on, although I hope that Imperial will correct me on this.

 

[Imperial One]

Originally Posted by Imperial One
"but who to ask for a truthful answer?"

Re my query above about access in that quad engine layout shown in the photo earlier?
It does all look very neat and tidy, but also diabolical to work on, although I hope that Imperial will correct me on this.

Sorry Bajansailor, I should have replied yesterday but got sidetracked! I apologise
There is absolutely LOADS of room to get round the engines.....all of them!
I am somewhat wider than I should be and have no issue at all. This comment is re a 4 engine installation.
As for the 3 engine one on the 23m this is easier still. Engine room height is well over 2m - on top of the engines - so you can stand up full height between them and you can get at everything with considerable ease.
As mentioned earlier in the thread, MBY are testing this boat in a week or so's time and will no doubt have something to say about access to bits and pieces - they normally do. Dave Marsh did actually look over the 4 engine one at SIBS a few years ago and somewhere I have a photo of him between the engines but I cannot locate it just at the moment but will post it if i can.
Hope this answers the query...off to look again for that photo.

 

[Bajansailor]

Thanks for that update above - sorry, I only asked because the photo of the 4 engine installation seems to be rather deceptive re how it looks as if if it would be very difficult for a person to get between the engines.
But that is good news re the excellent access all around.