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Author Topic: thrust/speed  (Read 909 times)

ntg06

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thrust/speed
« on: September 14, 2009, 11:52:32 AM »

I have just completed my first boat build (or rather restoration from old racing hull). It is a simple setup, single 550 motor (running off 12V), and my intent is to learn with this boat before moving on or up-grading.
The boat is about 30" x 8", and with battery pack weighs just over 4Kg (roughly 2Kg hull and electronics, 2Kg 7AH battery). I have tried 2 and 3 blade props on the boat, in a tank, and measured the "pull" with a spring balance. The 2 blade measures just under 3Kg, and the 3 blade just over 3Kg. Unfortunately I have not been able to actually run this on the lake yet.

I have a few questions:

1. For a speedboat of this weight, what sort of thrust should I aim for (is 3Kg too little)? It doesn't need to do 50mph+ at this stage, but I would like reasonable performance.

2. Is there a rule of thumb to roughly equate the weight/thrust to speed?

3. I have also been looking at brushless motors, but there are so many, it is difficult to work out which one to go for. I would like to stick with the 12V setup for now (get batts for free!), but increase performance. Can someone point me in the direction of a suitable brushless replacement? I know I will have to replace the ESC as well, so don't want to break the bank!

Thanks in advance for the help.


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