Looking for range under power

Discussion in 'Motorsailers' started by Andrei Taranu, Dec 1, 2020.

  1. Andrei Taranu
    Joined: Dec 2020
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    Location: Bucharest, Romania

    Andrei Taranu Junior Member

    Again, Mr Efficiency, TANSL, I don't require anything, I'm not looking to get a boat but I do want to know what the standard is for blue water sailing on yachts of this size. You're saying there's no average? No minimum required range below which the boat would not be desirable? I get it that if you put a bigger tank it would go further, really I do. What I'm asking is what is reasonable? What is expected? For blue water sailing, recreationally, the way most yachts are used.
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    With my best intention of "helping" I have to repeat (I hope you understand me this time) that, in my opinion, that figure you are looking for, that "average" value, that "normal" value, does not exist. What for one may be "reasonable", for another is not enough or is too great. Complicated, right?. I don't know if this helps you but I assure you that this is my intention.
  3. Andrei Taranu
    Joined: Dec 2020
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    Location: Bucharest, Romania

    Andrei Taranu Junior Member

    I'm fairly convinced that the range these yachts have been provisioned for from the factory accounts for the needs of the sailors/owners, and I'm also sure there aren't big variations on that to the point that they can't be expressed with a ballpark estimate. No worries tho. I'll find out.
    Last edited: Dec 2, 2020
  4. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Why all the drama? A quick look on the interwebs is all that's needed. Most sailing yachts in your lenght bracket are optimised for a cruise speed of +-10kn, with engines between 2-500hp, depending on actual displacement. Usual theoretical range given by fuel tankage is ~1000-2000nm, depending on the initial owners preferences.
    Now the reality check, most of this boats are not expedition boats, and are not intended to cross oceans in "cruise mode". They are cruised in specific areas, namely the Med, Caribbean, USA, long distance motoring is not a priority. When they cross oceans it's in "delivery mode", without guests. Why is that important? Because the biggest draw on the fuel tanks are the hotel loads. Even in delivery mode one generator is running at least half the time (sailing them manually is almost impossible), when you have a full complement of guests on board you have one generator on full time, and the second on demand (meaning it runs only half the time). Range under power is seldom used, this boats are normally motorsailed for speed and angle, and they go only a few days between ports and refueling.

    Example: Yacht FRIDAY STAR VENDREDI 13, CMN Yachts) https://www.charterworld.com/index.html?sub=yacht-charter&charter=friday-star--vendredi-3042 This is a very good sailor, originally designed as a racing yacht. It carries 3300l of diesel but in addition to the 300hp main engine it also has two 30kW generators. One generator running at rated capacity uses ~10l/h. I would expect typical use with crew only to be 50-100l/day, with full hotel loads 2-300l/day.
    You can browse the site above to look at other boats, not all are described as complete as this one, but you will get the ideea.

    There are of course exceptions, boats designed specifically for long range expeditions in remote areas, or for racing, and those can have significantly different statistics, but most superyachts fall in the above use pattern.
    bajansailor likes this.

  5. skaraborgcraft
    Joined: Dec 2020
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    Location: sweden

    skaraborgcraft Junior Member

    A very basic ball park figure is to assume 20hp will consume 1 gallon of diesel. So if you know the engine power and the tank size, you can work out how long the fuel will last. How far it will go will depend on its length and tank size. Maybe a safe guide to say the hull can reach "hull speed" at around 75% of power. Ball park figures. There is no "average" when it comes to boats, but fuel consumption per hour/power is a known quantity across the board, at least good enough to make calculations.
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