Hi Jay,
It depends on the risk of going broke that you want and heavily on the exact standard deviation. Say your standard deviation is 24 bb in 1 hr, that would be 12 times your hourly rate, and say you want a 1% risk of ruin. Then you would need a bankroll of -[ 24^2/(2*2) ]*ln(.01) = 663 big bets. The actual bankroll formulas are in this thread:
bankroll formulas
-Bruce