IPS and other drive options

[MapisM]

Well, when hitting a rock, damaging the hull, the transmission(s), the rudder(s), or the stab fins, it's all just a matter of luck. I don't think I would accept an oceanic passagemaker with no stabs just for the fear of hitting a rock with one fin...
Nonetheless, if structural strength is your main concern, Nordhavn is far from the top choices in this type of boats imho, for a very simple reason: they're built with the wrong material.
If you must dream of a really safe passagemaker, dream of a steel boat.

Re.sterndrives, actually IPS was never meant as an alternative to them, being the replacement of shafts their unique objective.

 

[Nick_H]

[ QUOTE ]
I agree shafts are the worst case

[/ QUOTE ]

Uh? when I said the same you disagreed

You both seem to have glossed over the design feature of IPS that allows it to shear off and leave the hull watertight. This might be expensive, but surely makes it safer than any other drive system in the event of an impact?

 

[Deleted User YDKXO]

codprawn, I believe that the failure mechanism by which the IPS leg breaks off without ripping a hole in the boat has already been tested in an accidental grounding in the USA. In that sense, it's safer than traditional shafts because, in a grounding, the shaft and P bracket are likely to be ripped out of the boat leaving a hole. However IMHO, IPS legs are more exposed during a grounding simply because they are physically larger and protrude further than a traditional shaft system

 

[Deleted User YDKXO]

[ QUOTE ]
The hull/keel doesn't protect the props on shaft drive planing boats

[/ QUOTE ]

That's not entirely true, houghn. For example, Broom hulls which are very definitely capable of 20kt+ planing speeds, have a quite substantial keel specifically designed to protect the props. I've grounded 2 boats during my time in the UK. The first was a Princess with shafts in tunnels and I hit the bottom in Poole harbour at very slow speed. It was a very light grounding but both props were quite badly damaged. Obviously the tunnels provided little protection. I also grounded a Broom in Chichester harbour once and, although it was also at slow speed, it was a harder grounding. Luckily it was on a rising tide so I was able to reverse off a few minutes later but I was really surprised that the props appeared to be undamaged. I had the boat lifted a few days later and, certainly, the keel had taken the impact but, the hull and props were undamaged. Brooms are designed for both inland and coastal cruising and the ability to withstand a light grounding is one of their selling points

 

[Deleted User YDKXO]

Thanks

 

[Deleted User YDKXO]

Surely, if you rip a stabilizer fin or prop shaft off a boat, it does'nt matter whether it's steel or grp, it still leaves a hole. I do agree though that, in a straight hull impact, steel is obviously better

 

[MapisM]

Agreed. But name me a grp boat built like this one if you can...
...with apologies to Nordhavn if that makes their boats look like children's toys.

 

[Deleted User YDKXO]

Blimey I'm surprised the thing floats with all that pig iron fixed to it /forums/images/graemlins/smile.gif

 

[PowerYachtBlog]

I tend to disagree with IPS being the replacement of shafts

the way Volvo marketed them IMO it started as sterndrive replacement for 40 - 50 foot sports cruisers,
rememeber sterndrive have been used in this size, but they are a pain for marina manovring plus the advantage of similar but a bit higher fuel consumption
what was the IPS marketing about, all how you can play around with your boat in tight marins thanks to the joystick

if IPS wanted to replace shaft I am sure Volvo would have started with a higher HP, still this is the future take of IPS as Volvo know there is a market for bigger sizes, especially for the sportier boats

 

[MapisM]

Yeah, isn't the power of Archimedes' law amazing?
75T - mind, for (just) a 55' - and she still floats....

 

[Deleted User YDKXO]

Can't agree with that at all, poweryacht. Volvo have clearly targeted IPS as a replacement for shafts rather than sterndrives. This is a quote from their website

[ QUOTE ]
Volvo Penta IPS – Inboard Performance System – is a revolutionary new propulsion system. With dramatically increased efficiency compared to inboard shafts

[/ QUOTE ]

And just look at the designations. For example IPS400 has a 300hp engine but Volvo calls it IPS400 to indicate that it should give a similar performance to a 400hp shaftdrive set up

IMHO, IPS gives no efficiency advantage compared to sterndrives so it could not replace sterndrives. Anyway Volvo are now introducing more powerful IPS drives which are very definitely in 50ft+ shaftdrive territory

 

[PowerYachtBlog]

[ QUOTE ]
Can't agree with that at all, poweryacht. Volvo have clearly targeted IPS as a replacement for shafts rather than sterndrives. This is a quote from their website

[ QUOTE ]
Volvo Penta IPS – Inboard Performance System – is a revolutionary new propulsion system. With dramatically increased efficiency compared to inboard shafts

[/ QUOTE ]

And just look at the designations. For example IPS400 has a 300hp engine but Volvo calls it IPS400 to indicate that it should give a similar performance to a 400hp shaftdrive set up

IMHO, IPS gives no efficiency advantage compared to sterndrives so it could not replace sterndrives. Anyway Volvo are now introducing more powerful IPS drives which are very definitely in 50ft+ shaftdrive territory

[/ QUOTE ]

now yes but before introduced to the market it was not

Stern Drives in fact are more efficent

big IPS are being delayed month by month don't know what the problem is there, may be some Volvo insideer can tell us more
Zeus has introudced new 700hp Pods

 

[TigaWave]

They might have to re think the word dramatic soon, or only refer to unsupported shafts rotating in the water flow before the props!

Risk wise, is it knocking bits off on rocks, control system failure or debris wrapped around your props that will spoil your outing?

Volvo were offered rope cutter technology for ips but showed no interest, Seatorque have incorporated it in their design.