Ok gang, I an working on new project I am building an Acadamey submarine and it come with a speed 280, I am going to upgrade the speed 280 to a Graupner 6v speed 280 race or even my astro 10. I am familiar with air props and their pitch etc.. but lost with boats. Ok back to the point, the model is about 12 inches long and 1.5 wide. I am going direct drive with a lipo battery at 11.1 volts or less. What prop would give me a nice mix of speed and a nice mix of run time. Lets say the battery is 600 mah to start off with. Any help is welcome. Thank you all for your help.

Jason

I'll move this down to the Sub forum, they should be able to help you out.

Several of us have converted the Type 9. We just used the stock motor and prop. Switching to a better motor sure wouldn't hurt. For the battery we ended up using a NiMH 9volt. With the stock prop/motor it will give about 15 minutes of run time. It fits easy into any of the compartments and under load gives out about 7 volts. Just be sure your ESC is rated for it. The rubber tubing that comes with the sub can't handle the higher power. Even if it is CA'ed it will only last for several runs before it comes off and your sub is adrift. I used a coupler from Hobby Lobby (not the chain store- http://www.hobby-lobby.com/ujoint.htm ). Part #GR355 is a 2mm to 3mm drive shaft. The motor and prop shaft are 2mm so you have two choices. Order 2 and use the ends to make a 2mm to 2mm or order 1 and some 3mm O.D. tubing. You can use the tubing to make a bushing to reduce the hole in the 3mm end of the coupler. Just be sure to cut a hole for the set screw to grab the shaft. Then you can use the left over tubing to make a prop shaft stuffing tube to help hold the shaft. I didn't like the idea of the shaft just running in the plastic bulkhead. Then use the rubber seal and cap that came with the kit to seal the prop shaft. Next use RTV silicone to "Glue" the motor compartment to the upper hull. Run a thin bead, install housing, let set for 24 hours, and then using a new sharp blade trim the excess off. It makes a watertight seal and if you ever need to get back into the compartment just run a blade around the silicone and pull apart. If you have any questions just ask and good luck!