SOF Cassis to Rome delivery trip

[BartW]

I'm just back home from this challenging trip,
Tuesday morning arrived in Cassis SOF, Alfonso (my assistant shipper) came from Napoli by train.
Weather prediction was OK only for Tuesday and Wednesday, so we decided to leave immediately after the checkup of the boat.
At 10am we left Casssis, towards San remo,(120Nm) and got there in time (at 16h) for refueling.
Wednesday morning at 5am, Alf and myself headed in to the dark straight towards Elba.
Have a look at this wind chart, and you get an idea of what weather we had all day:

Sunrise around 7h30 am was wonderful, including spotted some dolphins
Will add some pics later when I have more time

Re Route
We came along Island Giorgona (far on P side), Island Capria, Cap Corse, (far on SB side), Elba, GIGLIO, Toscane Ercole, to our destination Rome Fiumicino, to a yard 1mile up the river Tiber.

Re Costa Concordia
The VHF announced that it wasn’t allowed to approach the disaster area, lots of patrol and police boats around, so we headed strait to our destination, passed Giglio at approx 5nm. I took some pics from the dreadful cruise ship, but better pics are around on the net, and in news papers.

Re. Trip data, (San Remo - Fiumicino)
We cruised 11h20min at a distance of 236 Nm
average speed 20,9 Kn
first 8 hours GPS speed 20…21 kn
last 3hours GPS speed 21+ kn (less weight)
Fuel consumption 3500l/236Nm so 14,8l/Nm

Re engine RPM,
assisted with a professional skipper during the trip, I had a lot of time to do some investigation and tests. We cruised permanently at 2000RPM
Regularly measured with a small lazer RPM meter.
I was pleased that I could teach the “audible engine synchronization” trick to Alfonso, as learned from MapisM one here.
I can assure you that my engines have been running all day perfectly synchronized. Yes now I’m obsessed with that.

Re. Trim flaps, I’m aware of the fysics that applying more flaps could not increase efficiency,
but ones again we were confirmed that putting flaps down about 2° increases speed (0.3…0.7 kn) at same RPM.
I think that the reason for this can be that the trimflaps in their ‘in’ position are slightly ‘up’,
Bringing them down a bit, puts them in line with the boat hull and could probably increase hull length and lift, at the right place , right behind the props, just a gues ?

Re works in Rome,
Thursday, Friday and Saturday we met all kind of workers that are going to do some modifs on Blue Angel.
Their Boss (Mr Z) is the godfather of Canados boat building (and some others yards aswell) he’s no less then 77y old. He’s a good friend of Alfonso’s father, etc….
He introduced me to all the workers (some very old !) and some others still running some private business.
Despite the big crisis is Italy, aspecially in boat building business, I have the feeling that I’m going to save the Italian economy by far
More about the works in the rebuild thread later.

 

[MapisM]

Glad to hear that all went well, B.
And also that my ear-based sync system works nicely...!
It seems that you had some quite decent weather overall: when I did it in the other direction a couple of weeks ago, aside from the fact that we weren't in a 20kt boat, we definitely couldn't have kept such speed anyhow.

I'm not so surprised to hear that the trim tabs can improve the boat efficiency, if by "lowering" them you actually mean setting them level with the hull.
If the indicators are reliable enough (and that's a big IF, because the only dependable indicators I've ever seen are the mechanical ones, which are usually fitted on speedboats), I would definitely mark the position where they are level with the hull. In fact, the only situation when it makes sense to raise them higher than that is when reversing while mooring, leaving them fully raised when the boat is at rest.

Re. fuel burn, the 300 l/hr or so is consistent with the speed and the boat size/weight.
But didn't you mention in the past some figures which were a bit better than that? Mind, I might well be mistaken.

Last but not least, I'm amazed by the f/b pic at night.
If you helmed from upstair during the whole trip, rest assured that you don't need to worry about the water temperature for June dives!
Apropos, I've seen your email and will ring G. tomorrow. The guy knows his stuff, but he's not so keen on PCs and emails...

All the best for your works in Rome!

 

[grumpy_o_g]

Totally irrelevant but during World War II it was standard practice to de-synchronise the engines on multi-engine bombers as the crossed the coast. It mean that the observers couldn't tell how many aircraft there were or get the bearing or speed so easily - the Royal Observer Corp in particular relied heavily on hearing to identify aircraft and some were incredibly accurate.

 

[rafiki_]

Nice update Bart. I hope the mods go well, and look fwd to the commentary.

 

[Deleted User YDKXO]

Well done, Bart. Looks like you had a nice trip but 0.3nmpg fuel consumption! Ouch! Did you not think about doing the trip at d speed? We have had this discussion before but whatever the physics say, on some boats, putting the trim tabs down a little or even a lot does add speed and hence, efficiency. Certainly my last 3 boats have all gone faster over most of the rpm range with tabs lowered to some degree but its a case of experimenting with each particular boat to find out what effect they have, rather than generalising

 

[BartW]

Re. fuel burn, the 300 l/hr or so is consistent with the speed and the boat size/weight.
But didn't you mention in the past some figures which were a bit better than that?

<= 15l/nm has alway's been my recorded fuel burn, but that didn't match with the figures from another famous forum boat, similar size, but less weight, but with stabilizers.

About weight, my quoted 70T has been questioned and this could be correct, because I can nowhere get any proove of her actual weight, except in the origenal papers (20yo) the weight is 64.5T.
I guess it is more now, but probably less then 70T.
We will try to find out during the next liftout.

I would be really interested to know what the influence on fuel burn make stabilizers on a planing boat. I think it is a lot,
I am considering the stupid idea of retrofitting stabilizers to BA, yes I know I am mad, but I am very much interested in the technical side of such a project..

I'm amazed by the f/b pic at night.
If you helmed from upstair during the whole trip, rest assured that you don't need to worry about the water temperature for June dives!
Apropos, I've seen your email and will ring G. tomorrow. The guy knows his stuff, but he's not so keen on PCs and emails...

first 2 hours, we were on the FB, for better vieuw in the dark
next 1 hour during sunrise, for the beautifull vieuw,
from then we were inside

yes pls can you help me with my communication with G, much apreciated, many thanks !

 

[BartW]

Did you not think about doing the trip at d speed?

yes we did, but both of us wanted to stay for the night and have a good sleep in San Remo, as we had very little sleep the night before.
Then we wanted to be as far as possible wednesday evening, as weather prediction for thursday was bad.
And finally with such a good sea state, this was a ones in a live time opportunity for a 12hrs cruise at planing speed, which I enjoyed every minute of it, and thats what it's all about !

 

[jfm]

<= 15l/nm has alway's been my recorded fuel burn, but that didn't match with the figures from another famous forum boat, similar size, but less weight, but with stabilizers.

About weight, my quoted 70T has been questioned and this could be correct, because I can nowhere get any proove of her actual weight, except in the origenal papers (20yo) the weight is 64.5T.
I guess it is more now, but probably less then 70T.
We will try to find out during the next liftout.

I would be really interested to know what the influence on fuel burn make stabilizers on a planing boat. I think it is a lot,
I am considering the stupid idea of retrofitting stabilizers to BA, yes I know I am mad, but I am very much interested in the technical side of such a project..

Bart my fuel burn at 20-21kts is 16.5l/nm with the boat light, say 57 tonnes, and 18l/nm with the boat at 61tonnes

I'm giving figures from a fuel computer that knows the boat's GPS speed and fuel burn from the engine ECUs; you are being pretty approximate on your fuel burn and your 3500litres is maybe a round number, slightly? That said, 15l/nm seems just about rational (and very good!) in view of the C70's quite flat hull at the stern

Sleipner estimate that the stabs are 100hp of drag at 20kts. At 20kts my engines read 65% loaded and that's roughly 2000hp out of 3144hp max, so the stabs are 5% drag say. Hence my 16.5 and 18 l/nm would be say 15.6 and 17 without stabs

I would say 5% is a fair price to pay for the huge benefit of stabs, so fitting some on BA would be a great idea imho

 

[MapisM]

At 20kts my engines read 65% loaded and that's roughly 2000hp out of 3144hp max

Are you sure that's the correct way to read the load numbers, J?
I would have thought that 65 is the % of load vs. the max output corresponding to the specific RPM the engine is spinning, rather than the max rated power.
That said, I suppose that for 32 liters engines the power curve is rather flat, so maybe that doesn't make a lot of difference...?

 

[MapisM]

And finally with such a good sea state, this was a ones in a live time opportunity for a 12hrs cruise at planing speed, which I enjoyed every minute of it, and thats what it's all about !

Well, I still don't see the point in reducing the pleasure time...
...even more so when you think that you could make it at 4,6 l/nm, as we recently did in a similar size/weight boat!

 

[BartW]

Sleipner estimate that the stabs are 100hp of drag at 20kts.

I'm intrigued by the fact there is a water flow from the middle towards the side of the hull,
and
at further distance from the hull, the water flow must be in line with the course of the boat.
This must create a very complex and strong force on the stabilizers,
Why don't they leave a gap between the hull and the fins ?
(maybe not the right place here to discuss the details on stabilizers)

I would say 5% is a fair price to pay for the huge benefit of stabs, so fitting some on BA would be a great idea imho

thats on a new boat J, but on Blue Angel the project would cost more towards 50% of her buying price

 

[BartW]

Well, I still don't see the point in reducing the pleasure time...

you've beat me on that

 

[jfm]

Are you sure that's the correct way to read the load numbers, J?
I would have thought that 65 is the % of load vs. the max output corresponding to the specific RPM the engine is spinning, rather than the max rated power.
That said, I suppose that for 32 liters engines the power curve is rather flat, so maybe that doesn't make a lot of difference...?

Yep, you're right. I was being approximate. TBH I do not know what the load% actually means. It could mean the current fuel mass flow rate as % of max flow rate, and therefore approximate the power %, but I don't know how the number is computed. Latestarter might know the algorithms inside the ECU...

 

[jfm]

I'm intrigued by the fact there is a water flow from the middle towards the side of the hull,
and
at further distance from the hull, the water flow must be in line with the course of the boat.
This must create a very complex and strong force on the stabilizers,
Why don't they leave a gap between the hull and the fins ?
(maybe not the right place here to discuss the details on stabilizers)

Yes let's not do a big thread drift but in quick reply:

1. A gap would increase vortex losses and also bending force on the shaft/bearings
2. FWIW, and it's a slightly different posit from the one you were making, the new sleipner software which I am having installed in a few weeks varies the stabs centre position according to boat speed (after you do a "learning" routine on sea trial, so the computer memorises a graph). This is inspired by Ellesar's post on another thread, amybe it was my Sq78 in build thread, (I'll write a reply to Ellesar's post sometime) which Sleipner read on this forum. This is an industry first and will help reduce fuel burn (though, as i say, it doesn't address the "twisting" effect that you refer to )

on Blue Angel the project would cost more towards 50% of her buying price

Yup. My 5% was fuel burn %, nothing to do with capital cost €€€

 

[MapisM]

Latestarter might know the algorithms inside the ECU...

Yep, maybe he can enlighten us, if he sees this thread.
Otoh, I always assumed that since typically a properly propped boat achieves 100% load at the max rpm (hence using, by definition, the max output the engine is rated for), the load throughout the whole rpm range should be a good enough measure of the power actually "used" by the boat (calculating the % vs. the max output at any given rpm).
And since I was curious about my own previous assumption on the curves of your engines, I googled for them, and found them here.
Amazingly, the rated max power of 1550bhp (=1572mhp) is available through a very wide rpm range, from 1800 all the way to 2300 rpm.
I did expect a flattish curve, but I wouldn't have thought THAT flat.
So, assuming that at 20kts you're spinning 1800rpm or more, probably your previous calculation was reasonably accurate, after all.
Btw, I fully agree that a 5% additional fuel burn is a reasonable price to pay, considering the quantum leap in comfort.
Also because surely the power absorption would be much lower at D speed, probably to the point of being almost negligible.

 

[jfm]

Thanks for that info MapisM. Yup, that is one helluva flat curve! Of course as you say the actual power developed curve is different, and is in fact represented by the lower dashed line, which is modelled for a D boat. 1800rpm is about 50% of max rated power

And yes i agree with you that the 5%, which is acceptable, is a P speed figure. It becomes much lower at D speed - more like 1% I would expect, which is completely negligible

 

[Deleted User YDKXO]

Thanks for that info MapisM. Yup, that is one helluva flat curve! Of course as you say the actual power developed curve is different, and is in fact represented by the lower dashed line, which is modelled for a D boat. 1800rpm is about 50% of max rated power

Yes you're right, the prop demand curve is modelled on a d hull on Cat power curves. You could model the actual prop demand curve for your boat, if you're feeling particularly anal, by working back from the actual fuel consumption figures. When I had my last boat, I was initially puzzled by the fact that my actual fuel consumption figures were higher than the prop demand consumption figures given in the Cat data. It took me several months to read the small print! But at least Cat gives you a prop demand curve. Many engine manufacturers don't

 

[BartW]

some more pics as promised,

Leaving Les Porcerolles behind us (red dot bay)

Leaving cap de Bregancon behind us (gold dot bay)

Cruising at 21kn along the cote d"azur

A Famous monastry

Monaco

sunrise

Island Capria

Elba

Giglio

Toscane

Guided up the River Tiber by a pilot boat (obligatory for +50Ton boats)

Down the Tiber river from BA in the yard

Up the river towards Rome

And a typical local dish prepared by Alfonso

 

[MapisM]

Island Capria

LOL, that's Capraia, surely? When I read Capria, the other island in front of Naples popped to my mind...
Very nice sea conditions for a winter cruise, I can see why you preferred to go fast while you could.
Oh, and the "seppioline" look great, I can almost smell them from the pic... Yum!

 

[Erik C]

Sad picture to see the Costa ship lying there like that. Nice trip though!