The hull I am using for the POCV is based on the Cygnus Marine DS25
Fishing Boat. It is made by a company called Models By Design
, they specialise in G.R.P. model boats. The hull costs a little over £20, perfect for low budgets.
To begin with the basic components going into the hull are the Motor, Kort Nozzle, Propshaft, Propeller, and servo. The DS25 is not designed to run a Kort nozzle
, but as this system works well at low RPM and high torque, I decided to trial the Kort system with a view to using it in our larger vessels.
The first step is to find the centre line of the hull. To do this is I simply held a ruler against one side of the keel and carefully drew a line along the underside of the model. Repeating this on the opposite edge put two lines on the underside. Next it was just a case of measuring the distance between the two lines and marking up the centre.
To locate holes for the Kort nozzle I had to approximate where the nozzle would be best situated, I did this by viewing the hull side on and taking measurements to get the correct distances.
Inside the hull is a wooden support. This support forms the upper brace for the Kort nozzle, and provides the lower brace for the rudder servo. The support is held in with epoxy resin.
Once the Kort was fitted I used a similar method to locate a hole for the propshaft. The hole for the propshaft was slightly elongated to allow for minor adjustment in height. As long as the elongation was in the vertical plane there should be no deviation off centre in the horizontal. Before finally cementing the propshaft with epoxy take note to align the propshaft with enough room to give the propeller clearance inside the Kort nozzle, even when the nozzle is being steered.
I found that by following the mantra of measure three times, cut once, I reached an accuracy of about 0.5 of a mm when positioning the propeller.