Catamaran sinking article

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spannerman

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Was just reading the article about the catamaran sinking in Febs issue and I think the proof readers missed something.
The owner said he couldn't understand why the IPS drive didn't break off as it was supposed to when it hits something, the reason was he didn't have IPS. Volvo don't make IPS with so few horsepower as he had, what he had were two D 3's with sail drives which is a popular choice on powercats, but a saildrive is not designed to shear off under impact, so thats why it punched upwards no doubt ripping the rubber diaphragm out on its way thus the rapid ingress of water.
Either he was mistaken or they sold him something which actually isn't available.
 
Yup, I think you're right there spannerman. As you say, saildrives are popular on cats but are not designed to snap off.

Edit - have read subsequent posts confirming IPS - happy to stand corrected therefore
 
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I don't think you're right.

The Africat Marine website, (Very dodgy website, riddled with adware, do not visit) shows twin Yanmar 315 as standard for the 420, with an upgrade for IPS500 available for the princely sum of $75,000.

For the drive to snap off, the surrounding fibreglass has to be strong enough to take the shock load: surely Volvo Penta must specify this somehow?
 
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They do fp, I was discussing this with a dealer engineer yesterday aboard an f42, the lay up must be correct.

As a designer there should be no way a sail drive should be fitted into the path of an underwater object, look at most yachts, the keel is forward of the sail drive , way deeper than the drive itself.

The rubber surround is only there to make a seal not to take the full load as its supported from the engine to the engine bearers, direct to the hull.

I'm not sure on this one now, was it I p s or a sail drive ?
 
I would have thought the owner would know what drives he had. In any case, I still struggle with the concept of pods pinging off in teh event of a collision. The sums have to be pretty good, and the manufacture of both the pod and the hull have to be well matched to deliver. It also feels like a £20k problem for pinging a bit of sh!te. Not sure its a risk I fancy!
 
The IPS 500 is rated for 370hp, I can't believe they are offering two D6 370's in a 42 ft catamaran! I doubt there'd be enough space or bouyancy in the hulls for two IPS 500 units.
And they can't mean you can have IPS with Yanmars as it needs the full EVC pack to work. So the the website does indeed appear misleading.
 
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Option for 315hp Yanmars is on shaftdrive.

>>I can't believe they are offering two D6 370's in a 42 ft catamaran
I can :D


.
 
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Oh well looks like maybe he did have IPS after all then, doesn't say much for the construction of the boat if the hull gives way before the IPS breaks off as its designed to do.He states he was doing 15 knts which may be too low a speed for the shock to shear off the leg, so the hull broke instead....
 
spannerman said:
Oh well looks like maybe he did have IPS after all then, doesn't say much for the construction of the boat if the hull gives way before the IPS breaks off as its designed to do.He states he was doing 15 knts which may be too low a speed for the shock to shear off the leg, so the hull broke instead....
Click to expand...

When designing the installation, surely you cannot decide that the pod will only shear off above x knots? Not a good basis from considering the FMEA.
 
LOL!

All these people asking if you can have larger engines in cats!!!

No wonder the things aren't so successful in the UK.

Some of the best boats afloat are cats and many of those are capable of well over 30 knots.

They don't all pop along at 6 knots at WOT.
 
rafiki_ said:
When designing the installation, surely you cannot decide that the pod will only shear off above x knots? Not a good basis from considering the FMEA.
Click to expand...

I guess they have to draw the line somewhere otherwise the the drive would break off at the slightest impact, or even shifting hard from forward to reverse! Its a bit like karate where the guy hits a piece of 2"x2" hard and fast and it breaks cleanly, whereas if he hit it slowly it wouldn't.
All in all it doesn't inspire confidence in that boat/transmission combination IMHO.
 
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