Friends..modeleers..Colleagues..i am posting this simple idea, because , i am getting lots of requests to make a prop shaft and its outer tube in a simple way..answering to all personally is not possible with my slower connection..so here is the simplest idea, is tested for years, and works well, to years, and you need not any high rated stuffs to make this..same idea can be utilized in to any ctaft , any size, and any type..including a boat using an IC engine, as i post it later..
most of us, (modellers), the considered head ache is, to make a prop shaft and its outer tube..some try at lathe with expensive stain less steel, with bearings, and water seals..but will be expensive, and the power of the motor will be consumed a lots as the motor become liable to pull the grabing force of the water seals..and some of us try with solid copper or brass tube, in full length, and struggles to get a smooth free movement all the while..
when we makes a boat or ship model, we have two options..is, one, is the fixation of the propeller, in a straight angle, as we found in Puffer Coasters, and some other, is only for a real scale look..and years of my research and study taught me that it is not nessesary to fix the prop in a straight line, and works well..but yes a very steep angle is not feasible..so, as an alternate, as easy one, we can choose a slightly angled prop shaft for our use..and it works well..
after completion of the hull, place it in water..and mark the water level with a marker pen..take the hull out..and dry it..the marked line is only a basic reference, and not a final line..so, we can consider this line as a basic water level line, and easily can fix the drive shaft assy, just over the water line..so, can avoid any water leaks inside..cool and simple..