Yacht Testing

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Background

From its inception in 1967 the Wolfson Unit has used the towing tank and wind tunnel facilities at the University of Southampton and Southampton Solent University to make model testing available to the designers of small ships and yachts. As their experience and reputation grew, particularly through the testing of 12 metres, AC class yachts for the America's Cup, the tank testing has expanded to use larger models in a variety of larger tanks around the world.

Since 1983 the Wolfson Unit has provided model testing and analysis services for a number of America’s Cup syndicates including Team New Zealand winners of the America’s Cup in 1995 and 2000. For the 2007, cup, the Wolfson Unit was contracted to provide testing services to Emirates Team New Zealand, Luna Rossa Challenge, Areva Challenge and UIT Germany, as well as providing test equipment used for testing Team Shosholoza and Victory Challenge.

The increasing competition in the Volvo Round the World Race, the Open 60 class used in the Vendee Globe race and classes such as the TP52 has seen a rise in research and development budgets of competitors.

For the 2005 Volvo race, when the Volvo 70 class was first created the Unit had a hand both in the development of the class rules and also tank testing the Volvo 70 yachts entered. For this race we also saw a large increase in wind tunnel testing of sails and rigs. Not only is the wind tunnel valuable in designing sails and rigs but it was also found to be important for crew training as it is easy to see the effect of sail trim on the performance.

Extensive tank testing projects for AC and Volvo yacht development have been carried out at both small (1:9 - 1:7) and large (1:3 - 1:4) scale. Small models have proved to be a valid and cost effective method of evaluating design concepts prior to refinement at the larger scale. For projects with only a modest research budget, the lower model costs and quicker testing of smaller models offer an affordable way of providing useful design data. Involvement in these test programmes for racing yachts has led to significant improvements in test techniques and data acquisition systems, coupled to refinements in data analysis and scaling, with results now being incorporated into an in-house performance prediction program. Experience gained during testing of racing yachts is also applied to the testing of cruising yachts and sail training vessels.

Good design decisions rely on well-executed experiments and correct interpretation of test data in relation to full size performance. To help ensure this, Wolfson Unit personnel involved with yacht testing have studied the yacht design process and carry out all phases of the test programme from preparation of models, running tests, analysis of results and performance prediction, to writing the report. Their experience of sailing and experimentation is applied to all stages of the programme. Models can be modified quickly and re-tested, if new ideas develop or unusual results occur.

The towing tank and wind tunnel are only two of the many research facilities available to the designer. By working through the Wolfson Unit, he has access to the wide range of academic staff within the University specialising in such disciplines as computational fluid dynamics, aerodynamics, electronics, materials and structures.

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Sailing Yacht Model Tests

The following experimental techniques may be employed as part of the design process.

Towing Tank tests using small scale models, up to 2.5m long:
using the Southampton Solent University tank, which is 60m long x 3.7m wide x 1.8m deep and is equipped with Wolfson Unit designed dynamometer to measure resistance, sideforce, roll and yaw moments.

Towing Tank tests with large scale models, up to 6m long:
using larger facilities, such as the Haslar No.2 tank at Gosport, which is 258m long x 12.2m wide x 5.5m deep, again using a Wolfson Unit designed towing system and dynamometer.

Wind Tunnel tests on hulls and keels:
using the University of Southampton No.l Wind Tunnel with a working section 3.5m wide x 2.6m high x 9.1m long.

Wind Tunnel tests on masts and sails: using the University of Southampton No.2 Wind Tunnel, low speed section, which is 4.8m wide x 3.2m high x 3.0m long.

For further information see our test facilites page.

Full Scale Trials.

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Application of Results

Racing Yachts

Many of the techniques devised for ACC and Round the World Race yachts may be used to good effect on smaller racing yachts, even though budget constraints may dictate the use of small scale models. Definition of the performance trade offs available and rapid assessment of alternative design concepts can be carried out using towing tank and wind tunnel test results combined in a VPP to define the performance of different designs.

Definition of the performance trade offs available and rapid assessment of alternative design concepts can be carried out using towing tank and wind tunnel test results combined in a VPP to define the performance of different designs.

Typical studies include:

Sail Training Vessels

These vessels now have to be designed to meet the specific requirements of operating organisations and regulatory authorities, which make stability aspects important. The Unit has recently undertaken a number of studies for the UK Department of Transport, including wind tunnel investigations of heeling force and the effect of gusts, which have been incorporated into their sail training vessel stability regulations. Against this background, the necessary calculations for a new or modified design can be performed and the results assessed.

Towing tank tests can be used to provide data for:

Wind tunnel tests can be used to:

Large Cruising Yachts

This type of yacht often has to be designed to achieve good sailing performance with restricted draught. Some of the work described for sail training vessels is relevant but in addition the following can be applicable:

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Experimental Equipment

In most of the facilities used, the experimental data are gathered using Wolfson Unit purpose built dynamometers, whose signal conditioning equipment is linked to a PC based data acquisition system. Routine data analysis and results presentation can be accomplished during the tests.

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Software

For the analysis of sailing yacht performance, the Wolfson Unit and Yacht Research International Inc. have developed their own Velocity Prediction Program. VPP for Windows is a program for use by yacht designers and naval architects who need to perform sailing yacht performance prediction calculations as part of their design and evaluation process. It is offered with LPP, a windows based lines processing program. The Wolfson Unit also has its own programs for sale or available as a bureau service.

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