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A sailor like me wants a yacht for fast voyages. I use the computer in my research for the optimum design. Only the computer can give me a fast ranking of different variants. With the right search strategy the computer can also cover parameter ranges that might otherwise be overlooked by the designer.

A numerical method that is successfully applied in yacht design are the genetic algorithms. The computer is used to improve a design in an evolutionary process through many generations. I presented first results of this method at the Second High Performance Yacht Design Conference 2006 in Auckland. The figure of merit was the VMG and the constraint were the costs of the yacht. The validity of the optimum depends heavily on the accuracy of the predicted speed potential of the yacht. The speed must be calculated from the geometries of hull and sails. The resistance of the hull could be predicted at that time only on the basis of the regression factors, which were developed at the TU Delft. All influences on driving- and resistance-forces are still not known though. Of great help were the towing tank test data of a Dehler 33. They were thankfully supplied by the SVA Potsdam. The status of this work as of 2012 is described here.

In the years to follow, a lot of new tank test data became available. Since the beginning of 2013 all individual test results from the towing tank at the TU Delft are available on their website. This is a new invaluable knowledge base. Based on this experimental data and an additional boundary-layer calculation, I developed a new correlation for the residual resistance. A prerequisite for this task is explained here, the theoretical background and the results of the regression analysis can be found in this report. The database was increased by adding the towing tank results for the Delft-372 model. UliTank is a computer program that incorporates all the newest findings. In 2015 the Sailing Yacht Research Foundation published on their website towing tank results that were conducted in 2003. I used these results to increase the database of the regression analysis for the new version UliTank_3.3.This new version computes the resistance with appendages in the heeled attitude and with leeway. UliTank_3.3 can be downloaded  here.

The next step was a more accurate modeling of the sail forces. For this purpose I have developed the program UliSail. It is here available. A combination of UliTank and UliSail enabled the development of a velocity prediction program (VPP). The big difference to conventional VPPs is the numerical modeling. You can download it here.

One of the tasks in optimization is the creation of a lines plan for the hull, based on the optimization parameters. The program UliLines was written for this purpose and can be downloaded at UliLines.

In April 2011 the Yacht Research Unit Kiel allowed me to use their circulating water channel for the determination of the different resistance parts of hull and appendages. Unfortunately it turned out, that a CWC cannot compete with a traditional towing tank, the accuracy and repeatability of the results is not sufficient (report in German).Falltest

To define the constraints for the optimization it became necessary, to estimate the weight of the yacht for a given design. The structural weight can be calculated from the scantling rules of the classification society, but there was a gap if it comes to the design load for the keel-hull junction. To get reliable data for this design task, I conducted drop tests with a model-yacht in the summer of 2009. The results were published in the RINA transactions 2011 and are available as pdf-file. These results show, that for yachts with a low ballast ratio conventional scantlings might result in a structural design that is too week.

E-mails will reach me at "ulrich[a]remmlinger.com"
last update of website: June 2024
Preparation of drop tests at lake constance

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