I'm in the process of repairing a 40' spruce box beam mast that had some rot at the masthead. I've carved out the bad wood, and I've got to replace about the top 12 inches.

My question is, how do I cut the mast and the replacement wood so that I've got nice matching surfaces for the scarf? I've seen a description online somewhere, but unfortunately it wasn't very clear.

I'd appreciate any advice.

- John