How can I find the accel. of gravity with 2 pipes being swung?

[Capt. Sullivan]

I am given 2 pipes and string. Tied to each end is a pipe and in the center is a third pipe used to hold on to. I must swing the first pipe at 30 cm away and measure the velocity needed to keep it from sliding. Given the ratios between masses of pipes and the velocities, how can I graph and deduce the accel. of gravity?