Subs Model A2 in High Currents (> 2.5 knots)

Sontek 500 kHz ADP mounted in Subs

Sontek Tow Test Results

Equipment:

SUB, Model A2

Sontek ADP

Sontek Battery Pack

Custom attitude and compass package (BIO) with direct readout and data logger.

Tow Tank trials were undertaken in November 1999, using a Model A2 SUB, with Sontek ADP and external battery pack mounted. G. Fowler, P. Eng., of Bedford Institute of Oceanography on our behalf, conducted trials at a Canadian Government tow tank in Ontario, Canada. Instrumentation was assembled and installed by J. Hamilton, Physical Scientist at BIO, who supervised trials. Hamilton also plotted the data presented herein.

The purpose was to test three-axis stability at various current speeds. Previous trials had indicated that with the standard battery case suspended horizontally below the SUB, the pitch angle exceeded ADP manufacturer’s design criteria at moderate speeds. A high performance tail had been designed for these trials, which was expected to improve pitch self-correction.

Trials were undertaken with a battery pack slung horizontally below the SUB. The tow tank carriage did multiple runs of increasing speeds, commencing at .25 m/s, followed by .5m/s, 1.0 m/s and with the final run at 2 m/s (4 knots).

Pitch remained stable at all speeds, not exceeding 8⁰ at any speed.

Roll remained stable and minimal over the full range.

Heading misalignment had corrected below .25 m/s.

Data was plotted for each speed. Plots are attached.

Conclusion:

In this configuration, a Sontek ADP mounted in a SUB is a stable package, with all results well within manufacturers specifications and user requirements for applications with current speeds of not more than 4 knots. Data trends might indicate that higher speeds could be accommodated. The high performance tail is required to compensate for increased drag of the external battery pack and the large lobes of the 500 kHz instrument. This tail configuration must be the standard on all Sontek units.

Data Plots – Sontek ADP Tow Tank Trials

Note 1: Plus pitch is nose down.