Tank Testing (Take 1)

Its taken weeks of standing out in the freezing garage superglueing our fingers to thin plywood strips. We've gone through several trees and an entire beach worth of sand paper, but the model is finally ready.

Today we took it down to the towing tank at Southampton Solent University. Their tank is 60 meters long and allowed us to test (at an equivelent speed of 17 knots).

The model is fixed to a carriage that sits on rails via a post. The carriage can then be sent down the tank at precise speeds and the resistance of the model can be measured.



The model is sent down at a series of speeds, correcting the trim each run and then a resistance curve can be produced which will give the naked hull resistance of the boat at any speed. We can use this to estimate the amount of power required to reach certain speeds.

We ran tests in the sprint and endurance conditions and the data should prove invaluable to help us design the new boat.

Model Building Tarka I

We have been set the challenge of redesigning the hull for Team Tarka. The rules of the competition mean that the hull must be optimised to fit somewhere between being really efficient at low speeds (for the endurance event) and being really efficient at high speeds (sprint event). These two cases require a hullform with completely different features.

Before we start designing the new boat, we need to get a better idea of the performance of last years boat. We want to get some accurate data from some towing tank tests.

To do this, first we need to build a completely accurate scale model of last years hull.

We started by getting some frames (bulkheads) laser cut from 4mm thick marine grade plywood. These form the basis of the model and ensure that the shape of the hull is accurate.

The next challenge was to glue even thinner plywood (1.8mm) to the frames to form the hull of the boat. This took a suprising amount of time! Once the strips were glued on, they were faired - so much sanding...

The finished hull was then ready for a thin layer of GRP and painting - more sanding!

The boat then went on a major weight loss regime, losing most of the longitudinal (fore-aft) structure and all the bulkheads were cut down.