IPS? ouch...

[PowerYachtBlog]

This is what happens to an IPS propelled boat when it hits a rock!
Note the packing hanging from the front edge of the mounting plate. This was to stop the water flooding into the engine room. The rubber gaskets which are supposed to do the job of flood prevention, obviously do not. The drives are supposed to shear off under high impact and the gaskets are supposed to seal the water flow off. They don’t!
The high speed impact pushed the rear end of the drive unit into the hull of the boat as can be seen from the white mark. Fortunately the hull of this brand new (less than 10 hours on the log) Sunseeker Portofino 47 was strong enough to take the impact without any damage. The surveyor checked the hull with Ultrasound to verify this. Luckily the impact also failed to move the engines on their mountings. Note the “cabbage head” props.
This particular accident happened in the early evening but by next afternoon the engines had been removed for repairs. The whole engine room was flooded with both engines under water and had it not been for some quick thinking by the captain and crew, considerably more damage could have occurred if the engines had not been shut down so swiftly.
Conclusions.
The damage from this accident will require the engine electronics and engine room wiring and battery chargers, to be replaced. The Kohler Generator will also have to be replaced completely as everything was under water. Luckily this boat is built with a watertight compartment enclosing the engines and drives. If the boat had not had this feature then it would have sunk before help could have arrived. This leads me to believe that a shaft and strut system would not have sustained the same vessel threatening damage and the repair bill would be considerably less. The other thing to consider is the possibility of the loss of life under different circumstances.
http://www.thailandboating.com/page1/page1.html

 

[gjgm]

mind you, driving any boat onto rocks isnt a good idea... whatever the propulsion system.
I m not convinced that this one incident demonstrates the concept doesnt work.. only that it didnt in this example.
Not good after ten hours of fun, though- Ouch.

 

[mjf]

Wow! Thats an interesting post.


Just shows that my continued concern about IPS is well founded still. The w/t ER compartment is clearly a must if you must have IPS drives.

 

[RobWales]

Interesting that the prop cones remain undamaged?

With these forward facing props it suggests that it was only by the depth of the prop blades that they were too shallow?

Bet the skip was well pissed off!

 

[timtap]

It makes the case for dumping the IPS concept in favour of the the older and reliable outdrive system with the collision kick features that are built into them

 

[PowerYachtBlog]

I would worry about photo 2...
look at the structure of the boat seperating, I am still not convinced of the surveyor views after the utrasound testing that noting happen there...
I think 90% of IPS has been a good marketing exersice...
Can I have a lesson please!!!!
Hope the electronics on these fair better to the other Volvo systems....

 

[RobWales]

I was tempted to say the same as you but when you save the pic and blow it up I reckon it is water running out of the break in the sealing area and running down the hull, check out the drip from the keel area!

 

[KevB]

If this was a "high speed impact" onto rocks I am amazed there is no damage to the skeg on the drive? I'd say it was an impact with a sandy bottom in shallow water.

 

[Nautical]

I guess this is what the doubters have all been waiting for and it sure does look heart breaking to see such.

However, before everyone decides to do some serious IPS kicking one would need to know a lot more about the incident. What was the impact speed?, was the boat stuck fast and bouncing up and down on the drives in a swell, if it had been shafts would it have punched a big hole in the bottom with the P bracket and the flooding been even faster, would the engine damage been even greater, a list of probables and maybes could be as long as your arm.

Personally this does not look like a high speed impact into rocks, more in line with some speed but into sand or shingle but certainly not huge impact forces and perhaps not enough of an immediate torsional force to separate the drives from the hull.

Bashing into rocks or running aground sand or otherwise at speed in any vessel is not a good idea and will almost undoubtedly result in serious damage.





Because this happens on a shaft drive boat and the boat ends up a total loss do we abandon shaft drive forthwith ?

Even if the drives did not perform as expected it still does not detract from the other benefits such as reduced fuel consumption, quieter running, less smoke , less vibration, joy stick control, station holding etc.

 

[Nick_H]

If the boat had been on shafts, it could well have ripped the shafts, p brackets or rudders out, and the boat would be just as likely to have sunk. I agree it shows that the shearing function on IPS doesn't work in every circumstance, and it's not the first time it failed. In fact does anyone know of an occurrence when they did shear as they're supposed to?

 

[MapisM]

[ QUOTE ]
I guess this is what the doubters have all been waiting for

[/ QUOTE ]Well Trev, surely those doubters wouldn't be waiting for that, if VP didn't promise miracles, in the first place...?

 

[DAKA]

The difference between IPS and prop shaft being ripped out in my opinion is

IPS leaves a hole for water to ingress.

Shaft leaves a hole backward facing that acts as a bilge pump as long as there is some forward momentum such as single engine or tow.

I agree with you that it does add more ammunition for the IPS kickers.

It has made me decide that I definitely do not want IPS on my next boat.

I buy secondhand which means that even owners who are prepared to endure the extra risks of sinking to save a few gallons of fuel a year they will have to put up with reduced residual values of IPS boats as many will not touch them with a barge pole.

I also feel the light prop damage indicates shallow water and not a Rock outcrop .

 

[Nautical]

Not quite with you on that one, a hole in the bottom of your boat is a hole, never heard of a backward facing hole ??

Your logic suggests that you would have a shaft drive boat because there is less risk of sinking your boat given a heavy impact, so you would buy the Corvette 320 pictured previously because after a heavy grounding on rocks you would have a backward facing hole instead of a hole. That C 320 was a complete right off and went to the bottom the S/S with IPS didn't and is probably back in the water now sailing.

 

[Nick_H]

Hmm, that theory might work at planing speeds, but it's gonna be difficult to plane when one of your shafts, with prop attached, is sitting on the seabed.

 

[Nautical]

I guess if one were easily swayed by advertising and PR and of limited intelligence to disseminate common sense from blurb one might be jumping for a baseball bat to batter the bejeezus out of VP IPS.

I would never sell IPS on the basis you would come off better after an accident such as grounding against rocks, its other benefits are of far more interest, I think VP were ill advised PR or otherwise to use the shearing of the pods as a sales tool, real or not.

I never believed Coca Cola was the 'Real Thing' either but I do like the taste !

 

[DAKA]

Self bailers work at 2-3 knots.

Anyone can experience this by using a seatoilet on the move in a Harbour, you do not have to pump out as the suction will empty it.

a prop hole will act as a bailer as long as there if forward momentum.

You do not need twin shafts for this to work.

 

[DAKA]

I do not know enough about the C320 ??

Does not look like a standard tunnel shaft boat and it is in appropriate to use it as an argument against shafts on fast sports/cruisers.

I have been out with a cruising companion who had the shaft ripped out.
carried on with one engine.
i stayed close by.
the boat did not start to sink until stationary in the marina.
Water ingress was slow as the hole was small compared with a 2 1/2 foot ips hole

 

[TigaWave]

That boat has got a horizontal grounding plate that would have given extra leverage to do the damage.

Most shafts that have grounded round off props and bump over logs or sand bars, as the gently sloping shaft transfers the horizontal momentum and energy into a vertical component. Snag a vertical set up as you have shown and the forces are far greater with huge leverage on the hull fixings of the bracket or pod.

 

[Nautical]

I don't think tunnels are standard on all sport crusiers , I would say they are in a smaller number. Your assumption is that you have one engine operating after an impact, if it were as the in IPS case both engines were kaput you are still going to sink, you have no forward momentum. It may well be the IPS stays afloat longer as the drive pods are still more or less in tack albeit bent to hell, on a shaft drive the P bracket could have gone straight through the bottom.

Personally I think it pointless to argue in favour of one or the other in the case of grounding against rocks or otherwise. Every senario / situation will be different, differing speeds, different sea conditions, different sea bed, different boat manufacturer, different layout and engine configuration, the computations are endless.

I think it best not to try run your boat aground in the first place !

 

[Nautical]

I don't think that the case, the point of impact may have been lower (level with the keel) but the forces would be fairly industrial (given the way the shaft has bent) if they impacted on the prop, perhaps even worse damage as the plate probably disapated some of impact into the keel.

The pic was only illustrative, I've seen lots, with shafts gone, rudder torn off, P brackets through the bottom etc.