This is from the C&N webpage: ANNE O Specifications length 113.85' [34.7m] beam 23.79' [7.25m] draft 6.4' [1.95m] construction Fiberglass builder Hatteras year 1994 engines 3 x DETROIT 1,450 HP speed 16 Knts accommodation: cabins 4 guests 8 crew 5 legal flag Cayman Island previously LADY FLORENCE Anne O has been very well maintained and updated by her full time crew and owner. Recent paint, new teak decks, new tender and O.B., upgraded electronics and entertainment systems are just a few of the special features of this boat. Main engines have been rebuilt and most systems upgraded when needed. New Fly Bridge hardtop and enclosure make this area one of the best on the boat to enjoy cruising.
Thanks. Do you happen to know the story behind why it has three engines? I assume it can be run on just one to save fuel, correct? Was that the think on having three? How crowded is the engine room space?
You won't get any sort of startling performance on just one and may have overheating problems. 3 x 1450 as against 2 x 1450 is a 1/3 more power On a small boat like that with 3 of those I would say very crowded.
"You won't get any sort of startling performance on just one and may have overheating problems." Wasn't thinking you would see "any sort of startling performance" on one engine. Overheating? Perhaps. But I would think if you weren't pushing it it wouldn't be a problem. Or at least one you could perhaps over come with larger heat exchangers. It shouldn't take a lot of HP to get it and keep it moving at low speeds in decent weather. "3 x 1450 as against 2 x 1450 is a 1/3 more power" Clearly. But with more drag and weight. Still wondering if it was done so they could run on one and get lots of range at low speed.
Hi, I will try and explain what I mean't about overheating. The size of the coolers have nothing to do with it. With a multi engine application running on one it is easy to overload that remaining engine. You would have to play abut with various throttle settings to get to somewhere that the engine is comfortable running alone. I went around the world on a 55m motor yacht, during construction I had electric oil pumps fitted to the gearboxes to enable extended periods of trailing a shaft. We were running A Rated, 3512 CAT Engines, normal cruising speed was around 1400 RPM. On one we could go along at 9kts at 900 RPM without getting high Exhaust Temps until we encountered any sort of head sea then 2 were needed or we would be down to aroiund 6/7 kts.
Yes, I understand you on making sure the gearboxes of the non-running engine are kept cool. But you could lock the shafts down no? And it's always been my understanding that shafts spinning in water creat more drag than a locked down shaft does. But I did forget about exhaust temps. But we seem to agree that by finding the right RPM and in the right conditions you could run on one engine. Correct?
I think K1W1 is referring to the remaining running engine. It can get overloaded pretty easily. So yes, you can always theoretically run on less engines than the boat is designed for, but it may be at a near crawl/idle speed.
Yes, I understand that. My comment about locking down the shafts was in refference to this: "I went around the world on a 55m motor yacht, during construction I had electric oil pumps fitted to the gearboxes to enable extended periods of trailing a shaft." I take the above to mean the electric oil pumps were added to cool the gear boxes of any non-running engine/s. But I'm sure he'll be along soon to clarify.
Hi, Here is your answer. We used to let the non running engine side freewheel the shaft, this causes a lot less drag than locking one. When one is locked you will find that you need to carry a lot more helm to maintain a straight course than just dragging it. The electric pump was set up to provide an oil flow to the clutches for some cooling and lubrication. I used to start the non running engine everyday at noon as I was doing the Engine Room checks and Log and let it idle for about 10 mins. It was the running engine I was saying you should be careful not to overload.
"We used to let the non running engine side freewheel the shaft, this causes a lot less drag than locking one." Interesting. So I take I'm wrong in thinking a spinning shaft creates more drag through the water than a locked down one does?
Well you learn something new everyday. And in looking around the web I found this: http://cr4.globalspec.com/thread/15712/Calculating-propeller-drag "I decided to consult with a colleague who is a naval architect and who has done tow tank testing plus he did a tour of duty in a hydraulics test lab building scale models of major civil structures like dams, river diversions, etc. Water flow and resistance was key. His answer was disappointing. The measured drag of fixed and free wheeling propellers will be greater or lesser as compared to the opposite, depending on hull shape, strut configurations prop design and position of prop relative to hull. In other words everybody is right, depending on what their personal experience was. Therefore you cannot predict or calculate what the drag is going to be with any certainty. Only emperical data from a tow tank will tell accurately." Makes for interesting reading. At least for me.
Hi, A hull shape or strut configuration that makes dragging a 4 or 5 blade wheel locked in place less of a load than free wheeling one would also make the drive efficiency less purely by the fact that it must mask a good percentage of the propeller when it is being driven by the engine. Props work the best in a straight angle of attack to the water, most conventionally driven yachts are somewhat of a compromise as this isn't a realistic possibility. The underwater gear should be set-up so as to provide the least amount of masking/interference to good clean water flow to the blades as possible. As Lars says above however none of what I have written about trailing and so on except for overloading the running engine applies if you have CPP's and can feather the blades- this is the best one of the lot when trailing a shaft.
OK, lets say I wanted to run the afore mentioned boat on only the middle engine. Where would I start and what should I do to see if it's feasible. And besides the oil pumps to cool the gear boxes, what other modifications would be in order. I have some ideas. But any and all help would be welcome.
With some gear boxes like a lot of the ZF's they have a shaft mounted oil pump that lubricates the gear boxes if the engine is not running. I don't know how good this is in the longterm. I would highly recommend running a lot less propellor pitch on the center engine so you're not running too high of an engine load. But chances are, you wouldn't have good steerage and also the boat would be a nightmare in any kind of sea. It would be easier to run the 2 outside engines (which at displacement speed wouldn't burn much fuel anyways) and not run the center engine. The boat sounds awefully slow for it's size and HP when compared to a Broward or Burger with twin engines.
