Tires for your scale crew boat. Electical supply store is the answer. I have scratch built two models of the Swift Ship 120ft boats. For my tires down each side I used 1inch gromets, they look scale and are a lot cheaper than those little rubber tires from the hobby houses. I mounted them the same way that we mounted the real thing on the boats. I have one that is a twin screw and one that is a triple screw. You said you are going to use Dumas 12volt motors, that I tried and could not get a good scale speed out of them. I now use Graupner 700bb`s. I use 2 jell cells, 12v 7.5AH. That combo does a real good job. Hope this note is some help to you. Lloyd

PS Hope to get my fleet (7 boats) on the water with our friend Tim if it ever quits raining up here.