NEW MBY and IPS

[DepSol]

Just glancing over the articles(s) (as there are going to be many more by the look of it) on IPS in MBY....it seems they no one has really asked the question about the drive coming off.

This is an important part to the whole concept as the drive cant kick back it just sheers off. Also they say its only for twin engine installations where if they cut a recess they could it it into a deep V on a single. Is the reason they arent fitting single installations because the drive shears off so easily it would leave the single engine man high and dry?

I think its a really good concept and I am all for new technologies but these "articles" are more Aditorials in my book as they dont seem to be answering the main question on everyones lips....how much is a drive to replace and why cant we have a safety line so we can recover them.

Also at what force does the drive shear 10 newtons 20 30 40 50 100 what? I mean if it was 50 newtons would it not shear a 49.5N but only shear off at 50. There must be some footage pics of the drive shearing off but this sees to be the bit that the press and Volvo are avoiding. I am going to go read the article in its entirety just in case I am missing something.

Whilst we are on the subject of new technology it seems that someone has come up with counter rotating shafts in other words duo prop pfor shaft that can be fitted to existing shaft driven boats. This seems to have taken back stage to Volvos (the great advertiser) IPS system. Is it because they have not fully released the information or is it not totally ready or fully tested yet? Ths seems like a good idea to me and you dont ave to buy a new boat to get it. Why cant we have 4 page articles on this one too....PLEASE. Unless Jake or Hugo are going to beat you to it Tom !

If these are sheduled to be covered in the next articles then can you please let us know. I like the new Mag which is satisfying as I recently took out a subscription please keep it going with the same enthusiasm that is bursting out of the latest edition.

 

[DepSol]

Just read section 6 of the YBW report which does cover this quite well but more questions need answering rather than trying to turn a negative into a positive by saying cos it drops off it is safer.

They claim Volvo have a video wonder if its available on line? The replacement cost of the ddrive probably going to be about 8k as the nybrol props are nearly a grand on their own.

Dom

 

[Mike21]

Read the article, they suggest that the force required to sheer off the drive would be a high speed impact, which if on a shaft drive would be sufficient to cause severe damage to the p-bracket and hull and possible loss of shaft.
They also suggest thst a lot of the improved efficiency is due to the fact the props
are not at an angle

 

[DepSol]

thats fine but I still think more definition is required, what do you call high speed I say its 30 knots plus but what do they call high speed may be 20 knots? lets put a figure on it and put our minds to rest.

Why does the drive and props have to be lost? 8k a pop is pretty expensive in my book. n Jst questions I think the journos should be asking.

 

[kimhollamby]

I wasn\'t at the Volvo launch...

...but it would have been crawling with journos from all over Europe and therefore quite difficult to corner the right peeps - these things rarely have a press conference in the accepted Q&A sense.

I'm sure these questions will be posed by the mags in some detail over the next few months.

Incidentally I understand the security leash idea but in reality have you thought through the implications of having a substantial lump of bronze swinging around on a tether underneath the boat with no control? There are some things about that I wouldn't personally want to contemplate...especially if trying to use the other leg to get me home.

I agree one has to hope the forces involved to break the leg off are indeed of the magnitude of the same forces that would mash a shaft and possibly rip it out (in which case you would be looking at a very ill boat indeed...).

 

[Its_Only_Money]

Re: I wasn\'t at the Volvo launch...

Surely the shearing forces will be designed around the need to protect the IPS joint through the hull - to maintain a watertight hull, this may or may not give a comparable level of impact with an equivalent shaft setup.

Also I don't think it will be possible to give a "shearing speed" except as a per boat model figure/range, a lighter boat may have a higher shearing speed due to the energy equations involved, taken to extremes a IPS in 20ft rib may need to be at 50kts+, whereas the QM2 may only need to be doing 0.0025Kts....assuming the drive hits an immovable object...???

 

[petem]

Re: I wasn\'t at the Volvo launch...

What no one else seems to have pointed out is that surely the draft must be increased by having a big vertical 'leg' hanging down. Therefore the likelihood of touching the bottom is also increased.

I would not have one of these IPS systems if it was supplied for free. Nor can I see many traditional shaft owners opting for them.

 

[DepSol]

Thanks Kim the idea of a lanyard would be to actually pullthe drive aboard once it had sheared off so a line would run to say underneath the bathing platform where you could then lift the live with your boat hook then haul it in. I certainly agree with you that carrying it around would onot be a good idea but some sort of recovery system would be good. If there is as little in the drives as they claim then it wouldnt be too hard to clean them an reinstall them.

I like the idea of IPS very much but dont like the idea of losing a drive especialy in the CI where we do go through some narrow and shallow channels. Fine its better than having the prop go through the hull but that takes a large force to do that is it the same force to break the IPS. All I am looking for is some kind of example say the one in their video how hard did they hit something what speed and how easy did it shear. Could you hit something with enough force to smash the props up but still keep the drive intact? I know its oing to be different for every boat but a rough idea would be nice.

Kim what are your thoughts on the counter rotating shaft drive system?

Dom

 

[kimhollamby]

Re: I wasn\'t at the Volvo launch...

[ QUOTE ]
Surely the shearing forces will be designed around the need to protect the IPS joint through the hull - to maintain a watertight hull, this may or may not give a comparable level of impact with an equivalent shaft setup.

[/ QUOTE ]

Agree - also that seems to infer there needs to be a careful correlation between that and the structural hull design.

 

[Mike21]

Suspect if you hit something hard enough to shear the drive, it may not be worth salvaging. As for pricefor replacement, don't think there is one at the moment is there?
It could be Volvo will have the video at LBS and you could always ask them at the show.

 

[DepSol]

I certainly will be asking for a bit more info on this side of things as I am more than happy with the benefits of it. Only other down side is that unless you redesign beaching legs you cant dry out which in the C I means you lose the benefits of some beaches.


Dom

 

[Mike21]

Re: I wasn\'t at the Volvo launch...

Looking at the pictures in MBY, doesn't look like there's any real difference in draft and with the skeg underneath a gentle grounding would probably not do any damage to the props on the ips system, but would possibly do with shafts.
Personnally I like the idea of better efficiency, and the fact that you can use smaller, lower powered engines and get better performance, so I hope the system does work as advertised.

 

[Mike21]

Would have thought outdrives would still be offered as they will be cheaper than IPS , but with shafts you couldn't beach it anyway, could you ? /forums/images/graemlins/shocked.gif /forums/images/graemlins/wink.gif

 

[DepSol]

Oh yes I know that but like the idea of IPS. In Guernsey we have beaching legs for shaft driven boats (not al can use them) so the mae design I reckon can be employed for IPS systems where th front of the boat will touch and the back will rest on the legs keeping them 6 inhes clear of the deck.

Dom

 

[Mike21]

Looks like you,ve answered your own question, get a nice wee design in for beaching legs for IPS driven boats before anyone else /forums/images/graemlins/grin.gif

 

[kimhollamby]

IPS and RCD

[ QUOTE ]
Would have thought outdrives would still be offered as they will be cheaper than IPS

[/ QUOTE ]

They will but apart from a bit of crossover they will cover two different power bands. Outdrives will no doubt get beefier again to handle even greater torque but IPS is likely to go higher up again into diesel horsepower bands (currently) not at all possible for outdrives.

The real fascination will be to see how Cummins MerCruiser responds to IPS if it takes off.

One thing I think in favour of outboards, outdrives and IPS from here on in is that the new sound emission requirements of the Recreational Craft Directive are most easily dealt with by boat manufacturers by using 'packaged' powerplants. In a traditional shaftdrive arrangement where you have a bundle of components slung together the onus is much more on the boatbuilder to prove the package complies. It's not been said as far as I am aware but my guess is this gave Volvo Penta a lot of motivatiobn for producing IPS.

 

[Its_Only_Money]

Re: I wasn\'t at the Volvo launch...

Just a thought but this will men that volvo will have to "certify" the hull design in some way, won't it?

Otherwise they won't be able to ensure that impact loads up to the shear point will be correctly handled by the hull mountings an hull integrity maintained?

Wonder what the insurance position will be if a drive shears but the boat sinks due to the join not holding...won't insurance blame volvo for a design defect?

IMHO this drives brings worthy benefits but at some comprmises and additional risks...

Might be interesting to see a duoprop leg with the tractor props to compare on efficiency and manoeuverability while maintaining kick-up capability and a better ability to raise/clear a fouled prop.

Oh and interesting to see that the only steering link between the legs appears to be electronic???

 

[ari]

Re: I wasn\'t at the Volvo launch...

[ QUOTE ]

Might be interesting to see a duoprop leg with the tractor props to compare on efficiency and manoeuverability while maintaining kick-up capability and a better ability to raise/clear a fouled prop.


[/ QUOTE ]

But surely the idea of IPS is as a replacement for conventional shaft drive on boats too big for outdrives? So a comparison with outdrives is irrelevent as they wouldn't be an alternative? /forums/images/graemlins/confused.gif

 

[halcyon]

Missing out on some of the intermediate posts, a couple of thoughts.
Front facing prop will suck in any nets etc, no rope cutter, no lift up the leg, do you need to do get a diving ticket if you have this drive.
What happens if you hit a floating sleeper size piece of wood, p bracket and shafts may deflect it, leg will protect the prop.
What happens if you hit a bit of 2x2 (50mm x 50mm) and prop picks it up, what will happen to the hull in the area above. Mate's 195 once picked up his floating boat hook ( long story ), it shot under water, and came out like a Polaris missile, landed the other side of the marina.
What if you hit something and loose a blade, that leaving the hub at 3,000 rpm is go have some energy.
Why not just put the prop on the front of a outdrive leg, same configeration, blade clear of hull, can kick up to protect it's self, can be tilted to clear nets, etc from prop, can be tilted to allow drying out.
Reminds me a one firm that developed a new type of battery charger, when they had finished they did not like it, but they had now spent so much money on it's developement that they had to carry on and sell them and make it work.

Brian

 

[ari]

[ QUOTE ]

Front facing prop will suck in any nets etc, no rope cutter, no lift up the leg, do you need to do get a diving ticket if you have this drive.

What happens if you hit a floating sleeper size piece of wood, p bracket and shafts may deflect it, leg will protect the prop.

Why not just put the prop on the front of a outdrive leg, same configeration, blade clear of hull, can kick up to protect it's self, can be tilted to clear nets, etc from prop, can be tilted to allow drying out.

[/ QUOTE ]

Think you're missing the point, this IPS is a replacement for conventional shaft drive, not a new type of outdrive.

If you get a net round the prop of a conventional shaft drive you cannot tilt it up to get to it.

Putting the props on the other side of an outdrive is missing the point, this isn't an outdrive. An outdrive cannot handle the power and torque that this can.

The idea of this is to give some of the benefits of duoprop outdrives to a conventional shaft type boat. Less drag, props level, duoprops, etc.

If you take two identical boats that are small enough to be able to have outdrives but have the options of shafts (like Fairline Corniches) then the outdrive version with the same engine will be faster (or more economical at the same speed) due to less drag and greater efficientcy. The idea of this is to give those advantages to bigger boats that wouldn't take outdrives.