I think a learned something today:

Tried to rip a piece of green pine that was cut from near the center of the
trunk...part sap wood, part heart wood. About 1/5 of the way thru the
piece, the kerf closed up so tightly it bound on the splitter and I couldn't
move the board either fore or aft. I finally drove a narrow wedge into the
kerf to free it up.

Perhaps foolishly, I decided to try to rip it all the way thru. About 80
percent of the way, the forces on the sap wood caused it to split from the
remainder of the board with a loud crack. When I picked up the sap wood,
there was a bow in it that deviated about 1-1/2 inches from straight. BTW,
the heart wood stayed relatively straight.

Lesson duly noted...I shoulda scrapped the piece and not tried to finish the
cut. I'm sure glad that sucker didn't kick back on me.