I had my first need for a blow-off tube this week. It was exciting. I was a bit surprised though, considering it was from a fairly small beer, OG of 1.039. I pitched a rehydrated pack of us-05 and 24 hours later the krausen was up to the airlock. I put the blow-off tube on and the krausen was to the jar of water in another hour. Does us-05 typically cause such big krausen? The beer was Biermuncher's Cream of Three Crops, by the way.