Why did the founding fathers choose a government based off of a confederation?

The American colonists had just fought a war with England to escape the tyranny of a strong central government.  When discussion took place in the Continental Congress for the shape of a new United States, there was very little support for a federal system.  Delegates wanted to be very cautious about establishing a system that would strip the states of their autonomies.  They felt that a system could be created where power was concentrated in the states, but held together by a confederation.  A confederation is similar to an alliance or a league.  The members are bound by the alliance but do not necessarily have to answer to one another.  The states, at this time, had all drafted a constitution of their own at the behest of the Continental Congress.  There was some variation between the different state constitutions.  Each colony had a unique history and culture and there was not necessarily a sense of national unity yet.  For these reasons, a confederate system was chosen instead of a federal one.