what is the function of the keel stringer?

[mada]

On the older (70's) 20 cc boats, what is the function of the keel stringer (the laminated piece that runs the length of the boat. It's the only active core stringer on the boat and is totally rotten in most of the hulls of this vintage.

A few experienced boat builders have told me that the keel stringer core does not really lend much at all structurally, it's the glass doing all the work.

This is 2x4 with a rounded top that runs the length of the center of the boat.

If the 4 main inactive (hollow) stringers are in good condition, is a wet core in the keel stringer a problem?

Any feedback and knowledge would be great.