Hull shape how aware are you ?

[Portofino]

Maybe Portofino's right, crappy hull

The low deadrise , cos of extra wide beam , the added fixed permanent trim cos of V drives shoving the engines back ,8uggering up trim --
Dosen,t bode well . but par for the course balancing accomodation and hull form .
Did it ride bow high ? Needed + ve trim most of the time and rolled at bit @ anchor . Not that roll @ anchor is a deal breaker - just an observation .

Average engine Hp --- it's never gonna see any benefit of "strakes " taken all the way back to the transom sub 30 knots

 

[Deleted User YDKXO]

Well, you live and learn, as the saying goes!
I've seen several Ferretti hulls (150, 165, 175, 185, 53, 550, 57, 590, 620, 630 - and I'm probably forgetting others), but never came across the 46.
I'd be curious to know their rationale for both choosing first, and afterwards abandoning that solution...

I'm guessing here but maybe on the F46 fitting the rudders under the hull would have put them too close to the props? Is there a minimum distance between props and rudder for any reason?

 

[Deleted User YDKXO]

The low deadrise , cos of extra wide beam , the added fixed permanent trim cos of V drives shoving the engines back ,8uggering up trim --
Dosen,t bode well . but par for the course balancing accomodation and hull form .
Did it ride bow high ? Needed + ve trim most of the time and rolled at bit @ anchor . Not that roll @ anchor is a deal breaker - just an observation .

Well we've acknowledged that Ferretti hulls are crap and no sane person would drive them on anything but a lake but you should know that as far as weight distribution is concerned, the engines might be further aft because they are on V drives but the fuel tanks are always forward of the engines along with other heavy stuff like generators and the water tanks are also always well forward too. None of my 3 Ferrettis has run bow high, in fact just the opposite. As for the trim tabs it is true that you get more speed with +ve tab at slow planing speeds but the hulls are optimised for fast planing speeds of 25kts+ at which you need zero tab to optimise speed. As for rolling at anchor, I've had quite a few boats and one of the things that I do like about Ferrettis is that they do seem to roll a bit less at anchor than other f/b boats I've had. Whether thats their heavy weight, the wider than normal beam or weight distribution I dont know but I'm only speaking as I find. As you know they've built thousands of boats so I guess they've learnt a thing or 2 over that time. And one more thing; all Ferrettis are classified Cat A under the RCD which means that in theory they are designed for offshore use in sea conditions with wind speeds exceeding F8 and wave heights exceeding 4m. Now that may be a bit of marketing BS but it does demonstrate that Ferretti have confidence in their hulls despite them being apparently flat bottomed and with their engines in the wrong place

 

[Portofino]

It's my understanding ,that if the rudders are too close they are in more turbulent water created by the props ,so much so they are more likey to stall , sooner than they would if further back , bit like an aircraft wing wanting clean /clear air .

With a v drive g box and engines aft as far as they dare in the interest of boat show deal clinching accomadation ,
As minimal shaft angle ,if you can is important .To try and max out on fwd propulsion and save wasted energy of the stern gear trying to change the attitude of the boat .
So with the props so far back , there,s not many options on rudder placement --- just the stern left .

How many Hp did it have ? -- guessing less than 500 ?

 

[Portofino]

Well we've acknowledged that Ferretti hulls are crap and no sane person would drive them on anything but a lake but you should know that as far as weight distribution is concerned, the engines might be further aft because they are on V drives but the fuel tanks are always forward of the engines along with other heavy stuff like generators and the water tanks are also always well forward too. None of my 3 Ferrettis has run bow high, in fact just the opposite. As for the trim tabs it is true that you get more speed with +ve tab at slow planing speeds but the hulls are optimised for fast planing speeds of 25kts+ at which you need zero tab to optimise speed. As for rolling at anchor, I've had quite a few boats and one of the things that I do like about Ferrettis is that they do seem to roll a bit less at anchor than other f/b boats I've had. Whether thats their heavy weight, the wider than normal beam or weight distribution I dont know but I'm only speaking as I find. As you know they've built thousands of boats so I guess they've learnt a thing or 2 over that time. And one more thing; all Ferrettis are classified Cat A under the RCD which means that in theory they are designed for offshore use in sea conditions with wind speeds exceeding F8 and wave heights exceeding 4m. Now that may be a bit of marketing BS but it does demonstrate that Ferretti have confidence in their hulls despite them being apparently flat bottomed and with their engines in the wrong place

No Mike the engines in my view are not in the wrong place , on your hull .
It's all a complex combo of the right mix of ingredients .Bit like walking down a super market isle filling your trolley to create a great meal.
As long as it tastes nice ,that's all that matters .
I,am just asking why ? - rarther than just complimenting the chef -- and going home ,not critical in any way .

Yup to ferretti knowing a thing or two about FB,s :encouragement:

 

[Deleted User YDKXO]

How many Hp did it have ? -- guessing less than 500 ?

440hp a side

 

[MapisM]

I'm guessing here but maybe on the F46 fitting the rudders under the hull would have put them too close to the props?

Naah.... They could have placed the whole propulsion a bit further forward, at design stage.
Judging from your pic, I don't think the transom rudders were an afterthought.
It's more likely that they designed the hull with the overhang keel extension from the beginning, hence allowing a shift astern of the whole propulsion (which in principle is more efficient - see the Itama proprietary propulsion in the couple of pics PF previously posted), and the transom rudders just followed as a logical consequence.
But I'm also guessing. As I said, I'd be curious to hear their reasoning behind that solution, as well as why they seem to have abandoned it afterwards (afaik).

 

[MapisM]

No Mike the engines in my view are not in the wrong place , on your hull.

You can bet that they are not.
Your comments on the engines placement and V-drive usage are based on a rather common old wives' tale, i.e. that the heavier bits in a boat must be placed as near as possible to the CoG.
Don't be mistaken: V-drives became popular well before the practice of designing the interiors first, with the hull following.
And originally, their raison d'être had much more to see with weight balancing, rather than space maximization.
In fact, what you want to place as close as possible to the CoG are the bits whose weight is not just relevant, but above all is variable.
This is the only way to minimize the effect of weight changes on the boat trim, because the difference between a light and a heavy boat is as neutral as possible to the weight distribution.
Now, have a look at the F46 floorplan and guess why you don't find the engines amidship...?

 

[MapisM]

and rolled at bit @ anchor

Porto, 'fiuaskme, you'd better not insist that the lower the deadrise the higher the roll at anchor, 'cause that is total BS, plain and simple.
And don't waste time googling for webpages where someone wrote that this is true, because it wouldn't change the fact that it doesn't make any sense, neither theoretically nor based on empirical observation and experience.
But of course, you are free to argue that what I am saying is as much BS as what anyone else can say on t'internet!

 

[Portofino]

Porto, 'fiuaskme, you'd better not insist that the lower the deadrise the higher the roll at anchor, 'cause that is total BS, plain and simple.
And don't waste time googling for webpages where someone wrote that this is true, because it wouldn't change the fact that it doesn't make any sense, neither theoretically nor based on empirical observation and experience.
But of course, you are free to argue that what I am saying is as much BS as what anyone else can say on t'internet!

As I said its no biggie ---so many variables --- since you have raised it ----
Nope no need to research this one -- common sence .
As allready agreed a bit back a vertical pole is less likely to roll .
The lower down you can get kg s like engines ,tanks etc the better --and keep lower down as much as poss any weight .
Reduce top heavey ness .

Paddle boarding --- weight 20kg kg ---ave man 85kg
On its own ,20kg ( flat low deadrise thing ) it v stable just rises up and down with a wave .
Lay flat on it -- fine ,just sinks a bit draft increases only .Total weight now 105 kg
Kneel on it ,starts to get a bit tippy but need minimal balance .You can move about a bit on you knees ,you can move the 85 kg around a bit -- all ok reasonable stable .Away you go have fun keep dry
Stand up ie substantially raise the CoG over the centre of buoyancy ,one wrong move it cap sizes ,very unstable ,requires skill to balance it ,the85 kg is now far too high !- one wrong move you get wet ,your in it capsizes .
Before it does that you rock n roll all over the place .

So in a boat anything even the slightest thing you can do to lower the CoG in relation to centre of buoyancy is good .

The Deeper V "Ray Hunt " method allows you to site engines etc lower **than the flatter aft /mid sections .
Eg the 500 L water tank is triangle shaped fitted in the centre of the V under the companion way steps ,as low down as you can .The black tank in the centre often in deep V between the engines ,
Fuel tanks also have asymmetric bottoms fitted to the hull shape --drain cock at the bottom of the lower triangles -ideal spot .
Of course there are load of other ingredients too to lowering the CoG eg solid hull ,and cored superstructure ,if you have a superstructure like a FB .
With a flatter hull you loose out a little on mounting Kg,s lower in Cog terms .

The more wider the paddle board like your hull is ,the lower you can get even the slightest shift makes a huge stability difference .

Kids ,shorter and lighter 40kg at say 1.4 M stand up easier than a 1-9 M at 90kg bloke .Static
When you get moving the faster you go more stable the board becomes ,it stiffens up .

At rest a wider board is more stable than a narrow board too for the same kg,s like Deleted User s Ferrettis
But a shorter 90 kg person on a board is more stable as well compared to a taller 90 kg person .Its all about lowering the CoG
I ,ve noticed women that are the same height as blokes are more stable ,less tippy --they have a lower Cog

Infact so much so they make Ski,s for blokes and women differently to reflect thelower CoG in the women .The mounting plate for the bindings are further fwd to help them balance ,when they squat they lower the Cog and a greater proportion ( hope thats reasonable PC ?) of there kg goes back .
While a blokes heavier in the shoulder and generally up top - it goes fwds .

Idea is to get the Cog as near as poss to the centre of turning on the ski
Ifs it not its harder to turn ---properly .

With a boat it helps together the Cog as close to the centre of buoyancy in a vertical plane to make it less unstable .
I would have thought less tippy .
Flatter hulls could by there very nature have a higher raised centre of buoyancy compared to the deep V ,
It's about getting the Cog and centre of buoyancy less distance apart .
A deeper V gives the designer more options to achieve that .


In a flatter hull likey to have off the peg tanks rectangles rarther than fitted to hull form as there is little to be gained cos it's pretty flat inside , more likely to have outboard tanks as little to be gained by placing in the centre ,it not that much lower .
Out board in a deep V and you are increasing height significantly ,less so in a flatter hull .

Of course a flatter hull gains a huge lift advantage = less Hp with lower fuel burn .
Ferreti 46 - 440 hp ? 4.6 m beam
Itama 46 -- 800 Hp ----,23000 kg dry. 4.45 Beam

** lower in relation to the water line with sufficient beam to enable

 

[Deleted User YDKXO]

In fact, what you want to place as close as possible to the CoG are the bits whose weight is not just relevant, but above all is variable.

Well yes Ferretti do always say that they put the fuel tanks over the CoG so that variable fuel load doesnt alter the trim of the boat and in my experience that works in practice. But IMHO there is another reason they put the fuel tanks forward of the engines and thats to put the fuel load as low as possible in the boat. I'm guessing here but the CoG of the fuel tanks on a Ferretti must be anything up to a metre lower than the CoG of wing tanks outboard of the engines on other boats. That may be part of the reason they get past the stability tests for Cat A RCD. Just guessing here so happy to be flamed on that

 

[MapisM]

Yup, agreed.

My point when posting the previous F46 drawing was that the overall e/r wouldn't have stolen more space to the cabins section, also if the engines were on straight shafts.
Just imagine swapping their position in front of the V-drives, placing the tank astern: easily done, at design stage.
But the weight distribution would have changed a lot, between empty and full tank.
That's just to avoid dismissing V-drives as a trick to gain space: that's IPS stuff, let's not mix the sacred with the profane...

PS: Otoh, there is actually one thing I don't like of V-drives: the poor accessibility to the shaft seals, but that's another matter altogether.

 

[Deleted User YDKXO]

Yup, agreed.

My point when posting the previous F46 drawing was that the overall e/r wouldn't have stolen more space to the cabins section, also if the engines were on straight shafts.
.

Yeah I understand that but actually I think that V drives do release a bit more space forward compared to straight shafts even with the fuel tank forward but yes you are right, not nearly as much as pods

 

[piratos]

Well yes Ferretti do always say that they put the fuel tanks over the CoG so that variable fuel load doesnt alter the trim of the boat and in my experience that works in practice. But IMHO there is another reason they put the fuel tanks forward of the engines and thats to put the fuel load as low as possible in the boat. I'm guessing here but the CoG of the fuel tanks on a Ferretti must be anything up to a metre lower than the CoG of wing tanks outboard of the engines on other boats. That may be part of the reason they get past the stability tests for Cat A RCD. Just guessing here so happy to be flamed on that

To be Cat A RCD compliant, full fuel tanks certainly can not be a condition. Whether tanks are full or empty boat should still be able to comply !

Itamas
you are going a little too far claiming "So in a boat anything even the slightest thing you can do to lower the CoG in relation to centre of buoyancy is good"
Best is to have the boat loaded homogenously (which is the reason a ship loaded with steel take ballast in wing/toptanks to compensate for the weight of the cargo loaded very low in the ship)

Maybe I misunderstand you, but as I see it a boat (same Beam and draft) with a flat bottom will have more space in the engine room that a deep V has. The distance between the deep and the flat V is lost space.

+

Have a nice day

 

[Deleted User YDKXO]

To be Cat A RCD compliant, full fuel tanks certainly can not be a condition. Whether tanks are full or empty boat should still be able to comply !

Well thats the point. I assume that the boat has to be within the stability requirements whatever the level in any of the tanks so certainly the position of the tanks is important

 

[MapisM]

As promised in another thread....

Ok, here's a few hull pics, for Portofino (and anyone else, of course) evaluation.

Besides, could I resist the temptation to throw in a STB? 'Course not!
To make things simpler, I am telling all the boat names but.... Can you match the letters with the numbers?
Some are very easy, but the virtual keg will go to the first who will get all the matches right! :encouragement:

a) VZ 16
b) DP 55
c) Ferretti 165
d) DP 58
e) Abbate G 36
f) Ferretti 681
g) DP 80
h) Aicon 56
i) DP 72
j) Riva 68 Ego

#1

#2

#3

#4

#5

#6

#7

#8

#9

#10

 

[Portofino]

Re: As promised in another thread....

Thx MapisM --there was really no need .
Hull Pics are Allways difficult to actually see the angels subtle angels IMHO -that my cop out folks .

My favourite are pic 4 and 9-- look deep deadrise ,have lifting strips taken to the transom ,and another clue I like them to have the trim tabs mounted hanging off .
I think those that intergrate them are x compensating some hull design flaw -like rides bow high / stern heavey - needs more stern lift ,most of the time ,in other words relies on the tabs to get the correct attitude ,or better attitude is a more acurate phase ..Wider trim tabs send me alarm bells -why so wide ? See pic # 2

Any how each to there own
Abbate is the outdrive pic #5 -deepest V and full use of lifting strips as expected to add back lift @ speed - reducing drag

Don,t like pic #1 and 8 -- too flat -relying on lift from the flatness and not enough depth -V - in the middle the strike area .

Others are all much of a much ness boggo mid 20 to high 20's knot sluggers

How ever pic # 4 would be the one I would choose if you said I could have one based only on those pics alone only -no other info.
I like the sharp forefoot -bow ,
I like the deep V deadrise
I like the double stern lifting strips
I like subtle obs the wide hard chine taken all the way back .
I like the props and rudders most rear wards -as far back -rudders esp
I like the low ish shaft angle ( compared to some others )
I like the V @ the area in front of the shaft exits -still sharp the strike area -- this should not slam -nice ride

What is pic# 4 ?

 

[jfm]

Re: As promised in another thread....

I'm not going to have a long debate, but for the record ref Porto's post immediately above, "lift strips" or "spray rails" do not produce lift. The angled hull that would be there without the strip produces exactly the same lift as the strip. The strip is to cut off spray, which reduces drag thus making the boat go faster and indirectly producing lift due to the extra speed, but obviously that is pointless at a permanently submerged transom. Spray rails taken to the transom do a useful function only on a pretty fast boat where the chines are lifted above the water when planning.

I don't have time to look properly but here is a quick guess - some I'm not at all sure about so definitely guessing:

a) VZ 16 4
b) DP 55 2
c) Ferretti 165 1
d) DP 58 3
e) Abbate G 36 5
f) Ferretti 681 6
g) DP 80 9
h) Aicon 56 10
i) DP 72 8
j) Riva 68 Ego 7

 

[MapisM]

Re: As promised in another thread....

Wow J, 7 out of 10 on the first attempt is a great result indeed! :encouragement:
I'm not going to spill the beans for a while about the 3 missed, 'cause that would make the virtual keg far too easy to win...

But just to answer PF last question, #4 is one of the 7 which you got right - btw PF, yep, VZ hulls indeed have a pretty good reputation.
Just to throw in another hint, I promise you to not tell Mr. DP that you confused an Aicon hull with one of his babies.
He doesn't exactly hold in high esteem the Aicon 56 hull behavior, to put it politely. :ambivalence:

Ref. higher lift of horizontal vs. angled parts of the hull of equivalent horizontal surface component, I did re-check the IT abstract of Levi's book that I previously quoted, but I couldn't find any physical justification of his reasoning behind attributing ALSO (not only) a higher lift to rails, hence his suggestion to bring them to the transom.
But pretty sure the reasoning was not restricted to racing hulls - in fact, he also built some not so fast boats, but all sticking to the same philosophy.

Just one thought: don't you think that there can be a higher newtonian lift with rails considering that the water flow under a P hull is not just longitudinal, but follows a sort of "V" shape, from the keel outward, and that's particularly true in the stern section?
For this component of the water flow, surely a different hull angle exerts a different resistance, hence lift, for any given horizontal surface component.
And "a fortiori", the same is bound to be true for rails, I reckon.
After all, they wouldn't have invented flaps, if it were just a matter of horizontal surface component...

 

[Deleted User YDKXO]

Re: As promised in another thread....

Oh blimey I'm feeling terribly under endowed now. I only have 2 spray rails each side on my boat and they only go half way back on the hull. Also my hull seems terribly flat and it doesn't protrude as far downwards as I would like. Is there any kind of medication or cosmetic enhancement surgery I could have?