Go to a paint store and buy a couple of the 1-gallon paint strainer bags. They also sell 5-gallon bags for larger applications. Next time your bag rips, place the oak in one of these paint strainer bags. This way, you won't have as big a mess in the bottom of the fermentor bucket. Sometimes the loose oak can get stuck in your siphon and stop it up.
I usually add a bunch of marbles in with the oak to weight down the bag, as the bag of oak will tend to float during the first few days of fermentation. However, if you don't weight it down, in a few days the bag typically will sink to the bottom of in the fermenting wine.
