PDA

View Full Version : Question about COG



bustitup
03-31-2009, 11:58 PM
Ok so I'm working on the mm..placing the motor, batteries, rx, servo, esc, rx battery and I have it sitting in front of me on a table with the nose pointed away from me sitting squarely on the table...so I start to slide the boat back towards me and I start to take measurements underneath the boat from the end of the table to the outside of the transom...I got the boat hanging off the table at 10" and it just starts to slightly teeter totter........is this basically what you want for a mm?...wouldn't this be about 35% ..is this "teetering " what you want or should I slide some weight forward to stop it

hope I explained this properly so you understand

crrcboatz
04-01-2009, 12:19 AM
I do it a little differently. I use a broom stick. Mount the hardware, place the other items where you plan to use them. Put the broom stick under the boat and move it under the boat from midway back toward the transom until it balances.
Now with an electric boat it would seem that one's ability to move the batteries forward or toward the transom provides leeway to make the cg flexible.
I would not do this until I had the hardware mounted though.

Curt

bustitup
04-01-2009, 12:25 AM
good info....yours seems like a two man operation.....


so it seems the goal is getting the boat to balance at a point that is 1/3 of the lenght of the boat?


I do it a little differently. I use a broom stick. Mount the hardware, place the other items where you plan to use them. Put the broom stick under the boat and move it under the boat from midway back toward the transom until it balances.
Now with an electric boat it would seem that one's ability to move the batteries forward or toward the transom provides leeway to make the cg flexible.
I would not do this until I had the hardware mounted though.

Curt

crrcboatz
04-01-2009, 12:38 AM
Well, again to me it would depend on the individual boat. I am of the opinion that each hull has its own cg. In gas and nitro they do. The beauty of the electrics is the ability to move the batteries, at least in most cases to achieve this.
I bet if you check, your individual hull has an optimum cg. I'd post up on that to get some other owners opinions. Better to do that than just make all your boats 33%!!

Curt

Fluid
04-01-2009, 08:31 PM
My MM runs best with the CG at 9". Different props and speeds can change this, but between 9" and 9.7" should get you where you need to be.


'