Wednesday, 18 April 2012

What The Boat Brochures Tell You


In thinking about the ideal second-hand cheap boat, it helps if you can get your hands on the brochure which would have been published when the boat was in production.

The photography will be superb. Sunshine, a sparkling sea and a cabin table with flowers and even a bowl of fruit on it. The brochure puts on rose tinted spectacles for you but if you know how to read between the lines and you have a calculator handy, you can discover a whole lot more. Here’s how to take off those rose tinted specs and gain a more realistic view of the type of boat which takes your fancy.

Bear in mind though, that the types of old boats likely to come within the 'Simple Sailing Low Cost Cruising' price range are probably from the pre-metric age,  ‘old numbers’ feet and inches for lengths,  pounds, and ounces for weight.

Beyond the pictures there is information about the overall length of the craft (LOA) and her waterline length (LWL), as well as the Weight of the Boat (Displacement) the Beam and the Ballast.

For sailing boats the square root of the LWL [in feet] multiplied by 1.25, will give you her optimum speed. 

Ballast divided by Displacement [in lbs] will give you a figure expressed as a percentage. The higher the number, the more stable or ‘stiff’ the boat will be. Some traditional heavy cruising boats will carry over 50% of their weight in ballast. More modern craft tend to be lighter and rely on a broad beam for their length to keep them upright. A comparison between boats in terms of Displacement/Ballast Ratios and Length/Beam ratios can tell you a great deal about what the designer intended.

For planing boats, you can also work out the speed a boat needs to achieve before she rises over her bow wave and begins to fly. The calculation is that planing begins when the speed divided by the square root of the LWL is equal to 2. A 36 foot LWL boat therefore would need to achieve twelve knots before she could begin to plane – 12 (speed) / 6 (square root of 36) = 2.



Armed with a good book on boat design, you can find out a great deal about a boat simply by doing a few sums. 

It's also helps to take a careful second look at the photos and imagine what life aboard would be like in a bouncing seaway with all the family aboard. Still interested? Then she’s worth putting on the list of serious possibilities.





Seaward