Marine Drive unit

 - selecting ​the right size of brass tube.

Your project may need a small length of small diameter brass tube, and it may need some filing. How do you hold it while you work on it? Select the largest drill bit that will fit in the tube. You can hold the drill bit in your hand with thumb and forefinger holding the tube in place while you work on it.

One of the tricky, early tasks in building a model of a twin-screw vessel is fitting the propeller shafts and tubes. Whether you are building a kit or from scratch, it’s equally tricky because you have to locate and make two holes in a surface which is probably sloping in two directions. The holes need to be in precise locations, and of a precise shape. They’re not even circular, but are oval. To make it even more complicated, often your only reference points (the ends of the propeller shafts) are located in mid-air somewhere, and you cannot see from one to the other in a straight line.

 - holding small lengths of brass tube.

Quick tip

         A marine drive unit consisting of prop tube, prop shaft, propeller and motor mounting is available from at least 2 suppliers in the UK, Model Dockyard and J. Perkins.  This item takes away the hassle of trying to  correctly align the motor with the prop shaft. It is supplied with a plastic propeller threaded 4mm,  so a suitable brass prop could be substituted. The current price is around £12.50 (approx $21).
   

Installing twin propeller shaft tubes.

Quick tip

Building tips - Hardware

If you've fiddled around with a ruler trying to find the right diameter of tube that you need in your bits box, there is a quicker way. Find a drill bit 1/32" smaller and use that as a gauge. Any piece of tube that fits snuggly over the drill is the right size.

Unfortunately it doesn't work with styrene tube.