Archive
- February 2022
- September 2021
- July 2021
- June 2021
- January 2021
- December 2020
- November 2020
- October 2020
- September 2020
- August 2020
- July 2020
- June 2020
- May 2020
- April 2020
- March 2020
- February 2020
- January 2020
- December 2019
- November 2019
- October 2019
- September 2019
- August 2019
- July 2019
- June 2019
- May 2019
- April 2019
- March 2019
- December 2018
- November 2018
- October 2018
- September 2018
- August 2018
- June 2018
- May 2018
- April 2018
- March 2018
- January 2018
- December 2017
- November 2017
- October 2017
- September 2017
- August 2017
- July 2017
- June 2017
- May 2017
- April 2017
- March 2017
- February 2017
- January 2017
- December 2016
- November 2016
- October 2016
- September 2016
- August 2016
- July 2016
- June 2016
- May 2016
- April 2016
- March 2016
- February 2016
- January 2016
- December 2015
- November 2015
- October 2015
- September 2015
- June 2015
- April 2015
- December 2014
- October 2014
- August 2014
- May 2014
- February 2014
- December 2013
- November 2013
- June 2013
- February 2013
- January 2013
- December 2012
- August 2012
- July 2012
- June 2012
- May 2012
- April 2012
- March 2012
- January 2012
- May 2011
Comparison of modern keel types for sailing yachts
Have you ever reflected over the different types of bulbs chosen for yacht keels? Today there is no general agreement on which bulb type is preferred for different types of yachts and very little scientific investigation has been done in this area. SSPA and Chalmers have carried out a study, where the hydrodynamic performance of different types of bulb keels were systematically evaluated. A paper is published in the International Journal of Small Craft Technology (IJSCT), a RINA Publication.
Have you ever visited a boat show or a boat yard at winter and reflected over the different types of bulbs chosen for the yacht keels. There is no general agreement today on which bulb type is preferred for different types of yachts and very little scientific investigation has been carried out for bulb keels for production yachts. Most of the scientific investigations for keels that has been carried out has been related to racing yachts such as America’s Cup and Volvo Ocean Race. In order to shed some light on the subject, Chalmers University of Technology and SSPA carried out a study, where the hydrodynamic performance of different types of bulb keels were systematically evaluated.
Four different keels were evaluated (3 bulb keels and one standard fin keel as reference) in a wind tunnel and further studied in a velocity prediction program (VPP). Two different scenarios were investigated in the VPP; new design and keel retrofitting. The selection of the shape and weight of the bulb for a sailing yacht keel should be carried out at an early phase of the design of the yacht. This is so, since the righting moment from the keel will influence the choice of rig and sails. In case the yacht already is built/designed and the keel is retrofitted, the sail and rig is already set and thereby the whole yacht is not as optimised as if it was designed from the beginning.
The results shows that the differences between the bulb keels are small, but the keel with a bulb integrated with the fin is slightly slower than the keels with more distinct bulbs, in either L- or T-configuration. These are very close in retrofit, but the T-configuration has a slight advantage in the new design scenario.
About the paper
The paper; “Comparison of Modern Keel Types for Sailing Yachts”, published in RINA, Vol 159, Part B2, International Journal of Small Craft Technology, Jul-Dec 2017. Co-authored by Kasper Ljungqvist, and Christian Finnsgård, SSPA. Michael Orych, FLOWTECH International and Lars Larsson, Chalmers University of Technology. The paper and the detailed results are available at www.rina.org.uk/IJSCT
Illustrations
Four different keels was evaluated. Three bulb keels and one standard fin keel as reference. Illustration: SSPA
The paper; “Comparison of Modern Keel Types for Sailing Yachts” was published in RINA, Vol 159, Part B2, International Journal of Small Craft Technology.
SSPA ramps up yacht testing
Lately, SSPA has tested models for a number of major yacht projects. Yacht testing requires attention to details not only in terms of the methods and model accuracy, but also, and possibly most importantly, in terms of how to handle the demands and criteria set by the client.
Sailing, aerodynamics in waves
Prediction and analysis of added hydrodynamic resistance in waves is an established research topic, with several accepted methods, but the study of sail aerodynamics in waves is an open research area. SSPA and Chalmers are cooperating in the Sports & Technology initiative, with several research projects in sailing. The leading journal Ocean Engineering has recently published a paper titled “CFD prediction of steady and unsteady upwind sail aerodynamics”.