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Yacht constructionTechnology: deep or flat keel?

Fridtjof Gunkel

 · 25.04.2011

Yacht construction: Technology: deep or flat keel?Photo: YACHT/H.-G. Kiesel
Swivelling keelboat: good performance and flexible
On most ships, customers have the choice between different draughts. What is the best compromise? A designer does the maths

There are keels for maximum performance, swivelling keels for maximum flexibility, sporty deep keels, simple flat keels and chine keels. Ranking them according to performance is not difficult at first glance. But what can a deep keel really do and isn't the shallowest model enough for a pure cruising yacht? What do the different draughts mean not only for performance, but also for stability, overall weight and centre of gravity? Yacht designer Marc-Oliver von Ahlen has analysed an example boat with different configurations and the same stability characteristics and delivers some astonishing results. The short version: the performance keel brings speed advantages of up to one knot - but the differences are close to zero when the boat is under centre of gravity.

In addition: Sailing professional Tim Kröger explains the advantages of a telescopic keel, which enables variable draught without sacrificing interior space, and shows how it can be replaced relatively easily with a fixed keel.

Find out more in the latest YACHT, issue 10 (first day of sale on 27 April)

Fridtjof Gunkel

Fridtjof Gunkel

Deputy Chief Editor YACHT

Fridtjof Gunkel was born on Helgoland in 1962; he started his sailing career there in the Opti and quickly switched to keelboats. North Sea Week, Cowes Week and Kiel Week were early stops, followed by many years in the Admiral's Cup scene on the cuppers “Container” and “Rubin” World Championships and international regattas in the Starboat, with the mini-maxi “SiSiSi” and various tonner yachts as well as participation in the Whitbread Round the World Race were further formative stations, flanked by extensive cruising trips. Fridtjof Gunkel joined YACHT back in 1985 as part of a traineeship, where he later became Head of the Test & Technology department and then Deputy Editor-in-Chief around 25 years ago. He is also responsible for the regatta and sports section. Fridtjof Gunkel privately sails a performance/cruiser moored on the Baltic coast, his favorite areas are the eastern Swedish archipelago and Brittany.

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