If you are considering buying a new cruising yacht (or one that’s new to you), you’ll likely soon be comparing two or more candidates of the same or similar “size” (LOA) by their published performance and range figures.
Well, I’m not going to try to talk you out of doing that — for as Poseidon well knows, a lot of yachting people, including pros like naval architects and captains, not to mention brokers and other salespeople, use published performance figures as a basis for such comparisons.
However, what I am going to tell you is that comparisons based on published figures can be wildly inaccurate — not because the builders or designers of the yachts in question intentionally fudge the published figures but because the test conditions under which those numbers are compiled vary wildly from one instance to another, without any established or commonly accepted standards or procedures.
I’m not talking here about the built-in physical differences between yachts — characteristics like different beams (resistance), different displacements (weight), and different above-water cross-sections (wind resistance) — but about what is usually not stated in published performance numbers, namely, wind and sea conditions at testing, loading, how speed and range were actually measured or calculated, and more, much more.
Consider, for example, the statement that often appears with published speed, draft, displacement, and related numbers, namely, that they are based on “half load” condition.
Half-load or half-baked?
Half-load is generally taken to mean half of total fuel, freshwater, grey and black water, and stores. And the rationale for using “half-load” condition is that the yacht will “perform” at a somewhat lower level with a full load and at a somewhat higher level as the load level diminishes toward and close to zero, with the “average” being at half-load condition. Fair enough.
Well… maybe not. The hiccup is that, even if used accurately, “half load” can mean different things in different contexts.
These days with either integral or closely shaped tanks, many cruising yachts are fitted with significantly more fuel capacity than a decade or two ago. Much of the time, this added fuel capacity is intended only for the occasional trans-ocean crossing and is not used on a regular basis. Why carry the weight of, say, 2,000 gallons fuel around all the time when most of the time you won’t use more than 500 gallons before visiting a fuel dock? As a result, a significant percentage of total fuel capacity in a yacht such as this should, I think, be considered reserve capacity for the very occasional long-distance passage.
Keeping the playing field level…
After all, is it accurate (or “fair”) then to compare the performance of a yacht at “half-load” with 2,000 gallons total fuel capacity to one of approximately the same dimensions, etc., but only 1,000 gallons total fuel capacity — as the weight difference between two such yachts at “half load” under these circumstances could be more than 7,000 lbs?
I’d say no. Which is why I personally recommend sea trialing yachts with oversized tankage (capacity significantly larger than the norm) at “one-third load”. As that provides, I submit, a much more accurate comparison to yachts with normal tankage.
However, that’s not all of it, just a single example. Here’s another. If you’re comparing published performance numbers as a way of filtering your search for a new (or used) yacht, and you want to avoid making the wrong decision, you have to drill down to see not only what engines with what HP ratings are being used in the yacht(s) in question but also what reduction gears and what size and type(s) of propellers are involved. And if the builder(s) can provide you with fuel burn numbers at various loads and engine rpm, so much the better since that can give you some idea of how much HP the engine(s) are actually developing… as opposed to what they’re rated at max output against a standard (theoretical) propeller load curve.
Ask the tougher questions...
There are a number of reasons that published figures sometimes distort the picture of how a given yacht can be expected to perform — not the least of which is that often the preliminary projections developed at concept development and early marketing stages too often persist in print without correction as the yacht’s design and engineering get completed and the yacht gets built.
Keep in mind that the initial performance projections (using the term “performance” in its very broadest sense) are generally as good as it gets. And just as no yacht ever grows lighter than its initial weight studies indicated, no yacht ever comes to need less power or be faster than the designer first said, no hoped, she would.
Consequently, it is well worth the effort to ask some of the tough questions of the builders and their salespeople, when you’re seeking to narrow your field of initial prospects. Then follow up with a sea trial to confirm the representations… before you put pen to paper on the final sales agreement. If you’re working with the right people, they will be happy to accommodate your diligence. — Phil Friedman