Through the 2012 maps, Spanker was part of Pitch Pole, which was very close to a full loop running from halfway up the mountain to the top of the lift and then halfway back down. To avoid confusion, Spanker is now the name of the section on the right (north) side that most riders do in the up direction. It was built by bikers to reach the top of the chairlift. It is both aerobically and technically challenging with rocks, roots and some steep but short pitches.
It begins a bit less than halfway up the hill where Keelhaul turns across the mountain. The location can be easy to lose your bearings on, as several old trails still exist. Most rides of Spanker involve coming up via Jibe and Keelhaul, so if you simply keep switchbacking up the mountain, you'll eventually move from Keehaul to Spanker. If you see the sign indicating the bottom of Dreadnought, you'll know you are now on the Spanker trail.
This is part of the "Race Course" climb, which starts with the first half of Jibe, continues on most of Keelhaul, and finishes with Spanker in its entirety.