Single-Track Hydrofoil

This website provides background information on our award-winning article :

G. P. van Marrewijk, J. K. Schonebaum, A. L. Schwab. 2018, March. “An Experimentally Validated Dynamical Model of a Single-Track Hydrofoil Boat”. Naval Engineers Journal, Vol. 130-1, American Society of Naval Engineers.

With this paper we won the Mandles Prize for Hydrofoil Excellence 2017, which has been granted by the International Hydrofoil Society. It has been published in the March 2018 edition of the Naval Engineers Journal of the American Society of Naval Engineers.

TU Delft Solar Boat 2014 was the first single-track hydrofoil boat on solar power.

Single-track hydrofoil boats are boats where the two inverted T-shape wings are placed on the centre line of the hull, see photo above. Back in 2013, the TU Delft Solar Boat Team designed the first solar-powered single-track hydrofoil boat in the world. The team goal was to win the DONG Energy Solar Challenge 2014 (now Solar Sport One). We were both members of the team back then. A documentary on the Solar Boat Team 2013/2014 and its boat can be found here (in Dutch).

The use of two vertical struts with hydrofoils ensures that the boat has a low drag, so that the solar power could be used efficiently. By using the front strut as a rudder, the dynamics of the boat can be compared to those of a bicycle: by steering into the direction of the rolling motion, the boat can fly upright.

The yaw, roll and sideslip motions of the flying boat depend on the steering input of the ‘pilot’. Unfortunately, no mathematical model was available to predict these motions. Instead, engineering parameters of the Solar Boat 2014 were based on other single-track hydrofoil boats, such as the Yamaha OU32 and this human powered hydrofoil. The boat was able to sail and make turns with this principle, but we had the feeling that improvements in the dynamic behaviour were possible.

In 2015, our successors in the TU Delft Solar Boat Team desired to use the single-track hydrofoil concept again. This time, as members of the technical advisory committee, we modelled the dynamic behaviour of the boat to find the optimum strut length, flight height and distance between the two hydrofoils. This model was based on conventional aircraft flight dynamics.

Application of the model resulted in a single-track hydrofoil boat design with shorter struts and a larger distance between the two hydrofoils. The performance of this Solar Boat 2016 was beyond expectations, as can be seen in the action video below.

However, the dynamical model that was used to predict the boat dynamics had not yet been validated, thus making its application to new boats risky. With enthusiastic support from Dr. Ir. Arend Schwab, we set out to experimentally validate the dynamical model. For this, motion sensor data from the TU Delft Solar Boat 2016 was compared to the mathematically predicted motions under a given sinusoidal steer input. We found that our mathematical model very accurately predicts the dynamic behaviour of the single-track hydrofoil boat at typical steering frequencies of 1 Hz and below. See the following figure.

Modeled dynamics and measured dynamics in response to a given steer input for five periods at 0.47 Hz. Continuous lines indicate model response, while dash-dot lines indicate the real measured response of the boat during testing. It can be seen that the model output is nearly identical to the measured output in both phase and amplitude. Velocity was 7.9 m/s and measured flight height ca. 0.15 m. Download the pdf version of this figure.

 

The validated model can be used in computer simulators for pilot training and boat design. The video below shows a first implementation of the model by the TU Delft Solar Boat Team.

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