Discussion in 'Technical Discussion' started by HTMO9, Apr 17, 2015.
The other issue is how often can you really run 40 knots or faster in a 60-80' yacht.
It looks like Arneson, ZF (SeaRex / MiniRex) and MTU maritune are dominating the market. The rest is either out of market or just working on very low scale in third world countries for the small fishing industry.
Btw. rcrapps, Fabio Buzzi is now La Marca Marine, spezializing in racing events and its hardware and Trimax belongs to ZF Italy (see above).
Not very much choice, if one wants to go for a long living and reliable surface drive propulsion. From the numbers out in the seven seas, Arneson seems to be the leader in that field.
To bad, that Seafury and LevDrive stuff looked quite promissing. And for something bigger and fast its only multiple Arneson AD16 or KAMEWA anyway.
How easy was life in the earlier days. Men went to sea with sails and for speed, they raced their horses. Nowadays, the young generation wants to break the sound barrier with boats (which makes a lot of fun too, as I rember personally but only with a Jet ).
I take my Pershing 80 up to Phuket quite regularly from Singapore for the season. It's a little over 600 nm there. The Pershing is quite happy to sit at over 90% engine load all the way ... at 47-48 knots.
I cover the distance in 15 hours of running time.
Takes forever to wipe the grin off my face though ...
This must be a floating fuel tank more than a yacht..?
Pershing boats are for sure the best boats (besides Riva) within the Ferretti Group. And this as far as quality and performance are concerned. But I do question your performance data a little bit.
We had demo rides on the Pershing 82, 92 and 108. But we never saw that performance on the two smaller ones. The tripple engine 108 is different. But this monster is beyond any reason anyhow.
Also the 80 is an older model, it is very similar to the 82. It has the same total amount of fuel of 5950 Liters and the 2 x MTU 16V 2000 M93.
At your powersetting of over 90 % (which is above MCP), your figures would mean a fuel flow of app. 198 Liter per hour, per engine. No way. 350 to 380 Liter per hour, per engine would be the realistic figure. If your MTU 16V 2000 M93s would have this fuel flow in this power range, the MTU company would buy the engines back for analysis .
By looking at the official performance charts of the Pershing 82, the vessel is capable of app. 43 to 44 Kts at half load and WOT, at MCP a little above 40 Kts and at cruise power setting, which is far lower than 90 %, app. 37 Kts. And the range to dry at this cruise powersetting is app. 330 NM (334 Liter per hour and engine) depending on load. At full fuel and water, you would have problems, even reaching this figures.
So, if you are covering the little over 600 NM in 15 hours (which is an average speed of app. 40 Kts), you own the greatest performing Pershing 80 in the world but you would need some "inflight refueling" for your trip and you are operating your engines outside their spec.
But I do agree on your statement about: It takes forever to wipe the grin off your face. It was the same with my son and me. And it took some time for my wife and my daughter in law to stop their knees shaking .
Just my 2 (Euro) cents
To cover 600NM in 15 Hrs is an average from cast off to tie up of 40kts. It is quite possible for the OP to have refuelled along this journey as long as it was done very quickly and if he was really able to cruise at just under 50kts.
That is what I called "inflight refuelling". Refuelling 5500 liter or more on a normal yacht type filling station in the Med, takes nearly if not more than an hour (it is not a F1 pit stop ) from entering until leaving the harbour. Leaves him optimisticly counted with an average speed of 43 NM / hour. If his boat is capable of keeping this pace for 2 x 7 hours continously (which I doubt, both for range and speed), it would still make him operating his leasure type light duty rated engines outside their spec.
My Citation is capable of carrying 7 passengers and two pilots plus baggage. It runs at 420 Kts True Airspeed or 0.72 Mach, has a range of more than 1.600 NM and can climb up to 45.000 ft. And it uses runways as short as 3000 ft for T/O and landing. But definately not all at the same time and load.
Note, he didn't say he covered it in 15 hours of elapsed time, but 15 hours of running time. So, assuming he fuels along the way, averages 40 knots, and fuels about midway, then it could be possible. Perhaps he even fuels twice along the way.
I do show slightly faster numbers on the 82 with 46.5 knots at 2400 rpm, 42.8 at 2250 and 34.5 at 2000. However, at any of those speeds the best 90% range I show is 275 nm. The 80 and 82 basically have the same engines and fuel capacity from what I could tell.
So two fuel stops and 40 knots average for 15 hours then works. 47-48 knots at cruise though would be some unique boat.
If its that what he said, I give him the credit .
"In dubio pro reo" and I claim the language barrier for me.
OB, the numbers are a bit high but close enough, depending which chart you took. At the typical ISA + 20 or 25 in the area from Singapure to Phuket, even more optimistic. But his used boat is most likely much better tuned and cared for than those bloody brand new, overloaded with options, demo models, we drove.
Btw., my 911 Turbo S makes over 200 mph topspeed, goes from Hamburg to Munich (app. 600 Miles) in 3 hours (unrefuelled of course) has a milage of nearly 50 mpg and a set of tires (especially the rear once) last for almost 100.000 miles. And while doing all this, its below 55 db(a) in the car and I listen to the B&O stereo sytem and enjoy classical music. And only a little bit of warm, clean air is leaving the exhausts. May be ?
But if somebody is interested, I can provide the real numbers .
naah ... just very thirsty ...
a couple of points mate ...
- i opted for the upgraded engines running 2,500 hp each
- while technically a 6,000 L fuel tank, the last 700 L is vapourware ... just doesn't exist
- she was clocked by Pershing reps after delivery at 51.2 knots in local waters here in Singapore
- at a high speed cruise of 47-48 knots, the fuel consumption is a little over 970 L per hour (total)
- the singapore-phuket-singapore run has been done on multiple occasions with the Pershing dealer and other avid boaters on board
- on a separate Pershing 80 thread here on YF, I posted a pic of the speed - 45 knots if I recall correctly
hope this clarifies it ...
you are absolutely correct ... running time, not elapsed time.
and three fuel stops along the way
congratulation on your well tuned version of the Pershing 80 then. None of the boats we saw, was capable of 50 Kts+.
How many hours do you have accumulated on the engines up to now? Do you have a special maintenance schedule due to this high usage?
thanks mate ...
if i'm not mistaken, should be north of 350 hours ...
and nothing out of the ordinary by way of maintenance ....
but i DO keep her bottom clean ... squeaky clean ...
Maybe that one needs to be returned to Porsche to find out why its fuel burn is nearly 1/2 the published numbers.
From a Top Gear Review:
Porsche is extremely keen to highlight the eco credentials of the new Turbo S, pointing to economy of 29mpg and CO2 emissions of 227g/km. These are, indeed, impressive figures for a 553bhp supercar, but the anti-petrolists, we suspect, will find plenty else about the Turbo S to rail against. Like its 198mph top speed.
Then my daughter in law was lucky, my son did not have the demo ride on your boat. With the performance of your boat, he would have bought most likely a Pershing. The main reason, he went for the quad IPS, was the fact, that the ladies (his wife and his mother) were scared by the demo ride.
After buying the much lower performing IPS boat (35 Kts WOT, bearely 30 Kts at MCP) he was talking about buying an additional gas turbine powered very fast boat like "Miss Geico".
Only the immediate offer of an pending divorse by his wife, prevented him going that road .
The same subject came up with son Nr.2. But the combined effort of all female members of the family and my humble person are trying to divert him to something more reasonable.
As you could see, I was joking about the performance data of the 911 T.
We have a running gag in Germany saying: "There no field with more lies and exaggerations than man with their cars". Top speed, acceleration time, fuel consumption and how long the tires last.
Actually, the 911 Turbo S with its 560 (german) HP and its 7 speed PDK automatic gear and the sport chrono option, can be driven with an minimum fuel consumption of about 11 liters per 100 km in real live but then, any diesel taxi driver will overtake you. Actually, I normally see 20 to 26 Liter per 100 km. With its loughable 67 liter tank, you are looking for a pump station every 250 km. And going really fast on the Autobahn, every 120 to 150 km. Turbo charged petrol horses get really thursty, when challenged.
And the tires, especially the rear once, last a maximum of 15.000 km and if my sons borrow that car (which they do quite often), may be half of it. But if concerned about those figures, one should not buy a Porsche.
Even driving a sportscar, does not mean, the car should not be reliable and long lasting. Thats the reason, I would never buy a Lamborghini or a Ferrari. My wifes 4 cylinder 912, 90 HP from 1969, bought second hand in 1973, is still in the family and going strong with its first engine.
I will give it one more try, just for the peace of mind in my family .
Taking a given boat like the Pershing 92, equipped with two MTU engines 2600 HP each, Arneson type surface drives and a fully laden weight of 80 tonnes. The performance on paper is around 41 Kts top speed, max. cruise 38 Kts and a cruising range with 9000 Liters of fuel of about 385 NM.
Has any of our esteemed forum members any idea, how a boat like this would perform with the same engines but with conventional shaft, prop and rudder or KAMEWA type waterjets. No fixed numbers, just estimates about their performance level, behaviour and handling. Both for the low and high speed regime.
We had our matrix with pros and cons for different propulsion systems and trains evaluated by some specialists and asked for some more advice on which system to go with.
The fixed surface drives like SeaFury and LeviDrives are only theoretically available and do not exist in this size at the moment. With Levi Drives not anymore, with SeaFury, they never did. They would have to be developed from scratch and the boat would have to be specially designed for them. They require a specific hull (different for both of them) with specific V, deadrise and spray rails. Because of their close proximity to the transom, the stern has to be designed in an specific angle and the raw water inlets or any other intakes or outlets and spray rails have to be at a minimum distance from the the surface wheels. Then the Surface wheels have to be specially designed for those drives and the boat. All of that stuff above for this one off has to be CE certified individually and than the complete new boat certified in total .
Far to much hassle, far to expensive and it takes far to much time and to much personal involvement during the build. End of story for the fixed surface drives.
Second, Arneson / SeaRex surface drives or Waterjets (KAMEWA or Hamilton HM Series). New thing learned, you cannot take a hull designed for WJ and just bold some SD on it or vice versa. Both systems ask for a specific hull design.
Besides the well discussed problems and negatives with surface drives, all vectored thrust steered and trimmed surface drive systems have an similar issue with the limited lifetime and wear and tare of the universal joint or double cardan joint. This higly flexible joint plays most part of a thrust bearing in the drive train, especially in the bigger, high power versions.
Compared to WJ, surface drives deliver higher top speed, faster acceleration and better fuel ecconomy at high speed. With additional retractable bow and stern thrusters, docking and med mooring would be far easier and acceptable. But in the low speed regime up to nearly 20 Kts more or less useless.
WJ have to be specially designed (mainly nozzle and pump wheel) for a specific optimum speed. Below that speed, they are lousy in performance and very ineffective, above that speed very fuel consuming, compared to the performance given. But they are quieter and easier to handle (steering, maneuvering). But as with SD, high maintenance and care. On SD, some maintenance could be done in the water, i.e a wheel change or similar. Whereas on WJ, everything more difficult than cleaning (diver), the boat has to go out of the water.
Having ruled out a fully custom boat (remember, we are looking for an officially 24 meter long boat, which means something in the region from 80 to 94 ft LOA) for the above reasons, we were looking at basically two different production boats, because they are by far the best in its class and type of propulsion.
1. The Pershing 92. Also with 92 ft LOA it is officially under 24 meters long (RINA calls it homologation length, the commercial world London Load Line Length). 2 x MTU 16V2000 M96L, 2600 HP each via 2 speed transmission onto SeaRex drives with computer controlled and assisted steering and trim. Combined with interceptors and Seakeeper Gyro, a great performing (41 Kts top speed, cruise 37) boat. Great Italian design, if you like that.
2. The Mangusta 94. Twin KAMEWA with the same MTU engines. Performance one step lower, top speed aroung 38 Kts, cruise above 30 Kts. Similar but less radical design, just a matter of personal taste. The boat is havier than a Pershing and has a higher fuel consumption. Quality almost as good as Pershing but both on a high level for Italian boat building.
Due to performance, any other boat with shaft, prop and rudder like a Horizon E-84 or a SanLorenzo 82 were ruled out. Production boats with variable pitch props in this size do not exist.
But with accepting a slightly lower top speed but gaining great overall handling and maneuverability, we are back to Volvo Penta IPS propulsion. Having this system already in the family, nobody would have to be convinced about the system itself, just a matter of accepting the slightly lower top speed.
Here we are actually down to only two contenders.
A Wim van der Valk 25 meter Flybridge with quad IPS 900 or tripple IPS 1200. A semi custom design made out of Alloy and with great quality but average performance. The hull rides pretty wet and top speed is limited but other than that a great semi custom boat.
The second IPS contender would be the Delta Powerboat, Delta 80, tripple IPS 1200 and by far the lightest of all above mentioned boats, due to its fully carbon vacuum-infused building process. Top performance, great design and as it looks from distance, it rides remarkable smooth and dry. High end as far as quality, design and final price is concerned but calculating its overcomplete standard spec, still reasonable.
As my humble person is only the advisor in this process, I have to wait and see, what the final decision may be. My personal vote has obviously been taken .
Just my 2 (Euro) cents
Just curious. Riva fell out of consideration over performance or appearance?