SOF Cassis to Rome delivery trip

[jfm]

the MAN D2842LE402 (1100HP) data sheet tells me:

at 2000RPM, (prop curve) fuel consumption is 145l x2= 290l This is very close to what we actually observe !!!

so adding 75Kw (100Hp) we would need 2100RPM for same speed
at 2100RPM, fuel consumption is 165l x 2 = 330l

290l to 330l = 14% more fuel
alle very aproximate !
but gives a good indication of what we would acheeve, I think.
and I'm still considering..

Those numbers don't stack up though Bart. Adding 100hp isn't adding 14% power, unless at 2000rpm your engines develop 714hp together, ie 357hp each, which is clearly not true. If adding 100hp isn't adding 14% power, it cant be adding 14% to fuel burn

The real numbers should be that your engines are developing say 900hp each at 2000rpm (prop curve), so adding 100hp of drag is an extra 5% in power and 5% in fuel burn per mile

 

[BartW]

Those numbers don't stack up though Bart. Adding 100hp isn't adding 14% power, unless at 2000rpm your engines develop 714hp together, ie 357hp each, which is clearly not true. If adding 100hp isn't adding 14% power, it cant be adding 14% to fuel burn

The real numbers should be that your engines are developing say 900hp each at 2000rpm (prop curve), so adding 100hp of drag is an extra 5% in power and 5% in fuel burn per mile

you're Always so correct J
I don't have software on this laptop to copy the MAN power curves in this post,
but here are the correct figures;
power curves scale is not accurate, so all very approximate,
max for these engines is 2300RPM, 809Kw (1100HP),215l/hr/engine

at 2000RPM(20,5kn) one engine produces 575KW (772HP), and fuel cons 145l/hr or 290l/h/2engines
so adding 100Hp (74.5Kw) for the stabs, is 50HP / 37Kw PER ENGINE (there was my mistake)
fuel cons at 612Kw (822HP) /approx 2030RPM is approx. 155l/h/engine or 310l/h/2engines

going from 290l/h to 310l/h is 6,9%, (very approximate scale!!!)
and equally, going from 772HP to 822HP is 6.5%

even more tempted to go for stabilizers now,
what it is their approximate position on the hull length ?
I guess this depends a lot on the hull type/shape, and position of COG ?

 

[jfm]

going from 290l/h to 310l/h is 6,9%, (very approximate scale!!!)
and equally, going from 772HP to 822HP is 6.5%

That's good maths! The 100hp is approximate of course

what it is their approximate position on the hull length ?
I guess this depends a lot on the hull type/shape, and position of COG ?

Picture below. They should not be too far forward else they can lift the bow when going fast. Princess had this problem big time in the p72. It's also good to have easy access. In both my and MYAG's boat they are under the floor in the master cabin/bathroom area.

 

[MapisM]

A couple of thoughts, if you're really considering to retrofit stabs:

1) Judging by your external pics, I would guess that BA e/r is rather extended towards the forward section of the boat.
This means that you might have a choice of fitting them either in the e/r or in the center cabin.
If given such choice, I'd go for the first, particularly if you're thinking to fit zero speed stabs.
No matter how well they're insulated, if located in the cabin you will always hear them a bit if and when used while anchored at night.
That aside, it's also easier not to have to run the hydraulic hoses through the e/r bulkhead.
But bear in mind that on top of the higher cost, also the installation of zero speed stabs is more complicated, because you need a second hydraulic pump, driven either by a genset PTO or by an electric motor.
Which arguably is good also for redundancy, but does take some space, hoses, etc.

2) if you could find a location with enough space around the fin actuators to enclose them in small, dedicated watertight compartments, that would be a big plus imho, particularly on planing boats.
In fact, the risk of water ingress after hitting flotsam (or grounding) obviously increases with speed.

 

[BartW]

A couple of thoughts, if you're really considering to retrofit stabs:

1) Judging by your external pics, I would guess that BA e/r is rather extended towards the forward section of the boat.
This means that you might have a choice of fitting them either in the e/r or in the center cabin.
If given such choice, I'd go for the first, particularly if you're thinking to fit zero speed stabs.
No matter how well they're insulated, if located in the cabin you will always hear them a bit if and when used while anchored at night.
That aside, it's also easier not to have to run the hydraulic hoses through the e/r bulkhead.
But bear in mind that on top of the higher cost, also the installation of zero speed stabs is more complicated, because you need a second hydraulic pump, driven either by a genset PTO or by an electric motor.
Which arguably is good also for redundancy, but does take some space, hoses, etc.

2) if you could find a location with enough space around the fin actuators to enclose them in small, dedicated watertight compartments, that would be a big plus imho, particularly on planing boats.
In fact, the risk of water ingress after hitting flotsam (or grounding) obviously increases with speed.

thats the kind of details I would like to discuss in detail, before doing this retrofit, But don't worry, for sure not this year, if ever.
This year many mods are in progress, even the hi lo platform, (very very sory MapisM) I'm waiting for the quotation. But don't worry no underwaterlights for me (yet)
Business was good last year, and promising good for this year, so....

But answering your thoughts,
I'm aware of the impact of the work, and difficulty's we could encounter,
a challenge ?

with reference to their position on Match, 0.5m...1m behind the center of the waterline,
this is exactly in my main cabin bathroom (SB) and dressing room (P).
Going more backwards, there is 0.5m...1m (?) fuel tanks,
and then in the machine room, there is very little space between engines and fresh water tanks (on the side walls), so I think bathroom/dressingroom would be the best position.

agree about watertight compartment, but lets first check if there is enough space available in the bathroom/dressingroom under the floor.
will make a few pictures today.
Would be good/helpfull to have a indication of what space is needed for the actuators, width, hight...

 

[BartW]

The 100hp is approximate of course

of course.


I'm sure you will sugest Sleipner to be the best stabs available , and I'm convinced that they have learned a lot and made subsequent progress from their cooperation with you ! (or even from this forum, re Ellesar)
But I think it does not harm to asc a alternative proposition / quotation.
Coincidently I discovered that the Naiad european office is in Maastricht, that's 5miles from my home.
Would be interesting to asc them their USP's ?

 

[BartW]

they have a small problem here in Rome,
the first snow sinds 25 years
they have no instant organisation for cleaning the snow from the roads,
snow chains for wheels are sold out everywhere,
traffic is completely stucked in and around Rome
stay on the boat is the best I can do

 

[BartW]

Room for the stab actuators ?

This is in the dressing room, (port side)
Here is space, but the acces gate is rather small (40 x 40cm)

Further backwords is a bulkhead,

It is possible to make a acces hatch in the dressingroom floor behind that bulkhead


On SB
The same (more backwards) spot in the bathroom is here,
very small acces gate, unless we remove the toilet, bidet and teac floor

When using the more foreward position in the bathroom, we have to make a hatch in the nice old teac floor here:

This last position is the same like on Match, relative compared on hull length
(all very aproximate in this stage)