Are IPS hulls shallower V than shaftdrive?

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I was reading the Beneteau Antares 12 mobo test in this month's Boats and Yachts for Sale and I was surprised to read that, for the IPS version of this boat, Beneteau flatten the aft end of the hull to give a shallower V. This is to provide more lift aft to compensate for the weight of the engines which are placed further aft in the IPS version. The standard shaftdrive version has a deeper V because the weight of the engines are further forward and, as a result, is considered by Dickies, the UK dealer, to be a better sea boat
Is it common that builders use a shallower V hull for IPS powered boats or is it just Beneteau with this particular hull? There have been comments in the press about IPS being less suitable for flybridge boats because the handling can be twitchy. So, does the panel think that flybridge boats are better having standard shaftdrive?
 
yes!
it has to be so especially on flybridge boats because of dangerous bending if you do an agreesive turn which might end up ugly
the engine weight problem Dickies say exists but is not so big as they make of it because I see many vee drive aft positioned engined boats who have a deep vee, Sunseeker is one of them....
Suneeker has normally 20 deg aft what is start to be considered as deep
for IPS flybridge the vee has to be -15 aft but also less deep in the mid 2/3 part of the hull
I think the new Astondoa and Rodman 42 launched in 2007 have 12 degrees aft deadrise
 
Unlikely to be the weight as the big issue, as Ferretti and Sunseeker have engines aft on some boats with V drives, and IPS will use smaller engines for the same performance (if you believe the hype).

It may be due to the shaft angle on shaft drive boats? As they point downwards, there will be some lift from the props, whereas IPS will rely solely on the hull for lift?
 
Is some of the 'claimed ' fuel saving of IPS down to hull design ?

Bayliner have a very shallow aft V which gives a much improved fuel economy.
My Bayliner was economic to run but @rap at sea keeping.

I hope IPS isnt going to encourage a generation of boats that are only suitable for the Solent/inland lakes /forums/images/graemlins/frown.gif

May as well order a shaft boat will a shallow V, benefit from improved fuel economy and leave all the disadvantages of IPS behind.
 
Possibly the outboard leg cavitates when turning as the hulls heel dramatically on IPS boats and the prop must be near the surface when it is the outer one of 4 in a row, so they had to get the outer legs lower in the water by reducing the V angle.
 
The article specifically quoted a Dickies guy referring to weight aft being the issue. The engines might be smaller and weigh less but what about the IPS drives themselves? They look pretty chunky. Anyone know what an IPS pod weighs compared to shaftdrive sterngear?
 
could the problem be connected to slow speed steering ?

If all the weight is at the stern , at slow speed the bow will be out of the water and will blow around in a side wind like a bit of polystyrene making the claimed easy berthing a nonsense unless a bow thruster is fitted .
 
As a matter of fact, there is an inherent flaw in using pod drives on any V planing hulls, not just flybridges: when steering, they generate rotating forces on the hull longitudinal axis, and the deeper the V, the higher the angle and the stronger those forces. There's nothing they can do to avoid that, aside from flattening the hull (which obviously has other disadvantages). They could have made the pods much longer, in order to allow them rotate horizontally instead of at the same angle of the hull, but surely there were other disadvantages, additional drag and draft being the most obvious that spring to mind.
 
In general the aft dead rise on IPS is shallower than trad shaft, this is partly to do with weight (the pods are heavy lumps of metal) and partly to do with the handling characteristics of IPS, the drives don't like being angled too far outboard, partly because if you have the response / speed setting wound up on hard lock you can pop a leg too close to the surface and loose drive and partly with the pods in a fixed position and no trim available from the pod they tend to pull the aft end down into the water, with a shallower V aft there is more lift than a very deep V. In our case a crank is introduced to the chines to give further lift and a more neutral balance. Trimmed and balanced correctly there is no reason why IPS is not as good in rougher water unless of course you plan on going airborne where the aft sections would be exposed to the rougher water. The forward section all the way to mid hull can be as deep as you like, the trick is the use of the Tabs and having powerful enough ones to keep the nose down at lower speeds in rough weather. IPS is very trim sensitive and some builders are still working on the basis of traditional drive configuration, an IPS hull has to be designed from the off as an IPS hull or it doesn't work.

Average deadrise at the stern for IPS is 15 degrees so not really shallow more like medium V at the aft and deep V at the pointy end or 'modified deep V ' .
 
Is this a nail in the coffin of Flybridge boats , or will it be a further distinction between Flybrdige sea boats and Sports boat Day boats
 
Not sure what you mean there, there are flybridge boats that are woeful in any kind of sea and there are sports cruisers that are like a knife through butter in lumpy stuff. What gets plonked on top of a hull be it a flybridge or an open/ hard top sports cruiser deck layout has nowt all to do with whether it is a good sea boat or not !.

If you forgive the commercialisim, this knocks seven shades of poo out any planning flybridge I have driven in really rough stuff.

sog2.jpg
 
nice Sogica 55, you saw the new 47 launched in Naples with IPS...
would be interesting to see how they compare to an Abs from your point of view
an Italian surveyor told me Abs is among the best balanced of all the IPS boats he sea trialled, with only the the Abbate G46 feeling better
as for the pods, I think the ZF Zeus pods being aft looking, on a flat surface and in tunnel pockets are a lot easy to put on todays mono planning hulls
an other advantage from ZF Zeus is that you can put any deep vee to it or so they say...
 
I was trying to say

If every one wants IPS but IPS turns an IPS flybridge boat into a poor seaboat then no one will order a flybridge boat and the flybridge boats will die.


I went on to say in my opinion

sports boats in the UK make a good day boat due to poor weather.


Flybridge boats tend to handle rough weather in more comfort.


One of two things can happen

either flybridge boats will cease to be ordered

or

Flybridge boats will be ordered with shafts for boaters who want to go out offshore in rougher conditions.

IPS sports boats will be economic and popular for day hops round the solent
and an occasional hop across the channel in perfect conditions.


(35-45 ft boats)
 
Ah I see what you mean, personally I think the traditional flybridge builders have some way to go yet with IPS or Zeus for that matter. IPS was adopted by the sports cruiser builders long before many of the flybridge builders and have in some cases four years history / development with IPS. It will come and with the larger engines available now with IPS within a few years mid sized flybridges with be norm with IPS or Zeus. The advantages are too heavily weighed in favour of pods for it not to become acceptable. Fuel burn will be a critical issue in time to come and everyone wants to be in the efficiency team not only from a marketing point of view but also on the eco (if that is a term you can use with boats) band wagon. FB builders haven't cracked the efficiency thing yet with pods as generally they are using modified shaft drive hulls which as we know are not best practice or offer the efficiency gains associated with pure IPS developed SC's.

I would also say comfort in bad weather is not restricted to FB, in some cases HT SC offers a better solution. Better vision, lower C/G etc. We all know of the dreaded bow to the stars scenario with some FB's once you knock the speed down and the only safe way to helm is from outside which kind of defeats the whole FB comfort thing. Again I wouldn't put FB ahead of SC in their ability to head offshore, i have done both in bloomin awful conditions and when it gets really hairy I have felt more secure and confident in a SC than a FB, partly because when you are down to displacement speeds the FB tend to roll alot more and with the better vision on a SC you get a better feel for whats going on around you and certainly with OD's much more responsive helm, you can dodge around the really bigger stuff much quicker.
 
[ QUOTE ]
, you can dodge around the really bigger stuff much quicker.

[/ QUOTE ]

Thats pretty much what I was saying..

The big stuff being around the Shingles for a trip out to the needles on a nice day.

The Big stuff to a Flybridge boat starts at Dogger and Ends somewhere in the German Bite, long things called waves, how can you dodge round 200 nm, a Flybridge boat would run out of fuel with its poor shaft drive economy after two wave dodges /forums/images/graemlins/grin.gif

Not meant as a serious post /forums/images/graemlins/wink.gif
 
[ QUOTE ]
I wouldn't put FB ahead of SC in their ability to head offshore, i have done both in bloomin awful conditions and when it gets really hairy I have felt more secure and confident in a SC than a FB, partly because when you are down to displacement speeds the FB tend to roll alot more and with the better vision on a SC you get a better feel for whats going on around you and certainly with OD's much more responsive helm, you can dodge around the really bigger stuff much quicker.

[/ QUOTE ]Agreed.
For a given hull shape, size, etc., I'd rather be out there in a SC with HT than in a FB.
With a big but: when conditions require a planing boat to throttle down at displacement speed, that choice is a bit academic, 'cause the only smart one is to leave them both securely tied to the dock!

PS: not to mention at night, when the last of your points doesn't count.
 
Ah yes assuming of course one is smart enough to leave it tied to the dock unlike myself who is as thick as a plank ! :-) In my defense after last pounding across the Irish sea the forecaster was more inept than myself :-( thankfully I was in one of the best handling SC's an ABS 45 , ha ha never miss an opportunity for a plug :-)
 
[ QUOTE ]
and with the better vision on a SC you get a better feel for whats going on around you

[/ QUOTE ]

I agree with the rest of your comments, but can't see how you get better vision from a SC than from the flybridge? In bigger seas one of the main advantages of a flybridge is you can see over the top of the next wave, so you know what's coming.

Oops, should be a reply to Nautical.
 
Abs 45... No HT, as I recall.
And you crossed the Irish sea in conditions where you had to slow down at displacement speed? Wow, how many times have you been in green water up to your knees...? /forums/images/graemlins/shocked.gif
 
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