The cover of the Climbers Guide to Smith Rock shows the famous Chain Reaction climb. But it also shows Smith Rock in the background, and a clear view of Sky Chimney. The photo of Asterisk pass on the main Smith Rock page also clearly shows the formations mentioned in this route description.
Follow the crowd of climbers down the big trail to the river. Cross the bridge, and continue following the crowds along the wide path beside the river. Walk past Morning Glory Wall, The Dihedrals, and Christian Brothers climbing areas, losing the crowds in the process. Head up toward Asterisk pass. Directly to the left of Asterisk pass is the Smith Rock group. The noticable arete on the right skyline is Sky Ridge. The wall that forms the left side of Sky Ridge ends in a wide open book with another wall. In this open book, at mid height, is a noticeably large hole. The book opens up into a wide shallow gully at the summit. You have found Sky Chimney. The base of the climb is a vaguely heart shaped rock with 3 chimneys on it's right side. Use climbers paths to get to this formation from the Christian Brothers/Asterisk Pass area.
Many thanks to rpc for his detailed update of the route, and the great photos.
Pitch 1: Choose the biggest of the 3 chimney's, and grovel up, using stemming techniques and a few tighter chimney moves. The pitch ends on top of the heart shaped rock, on a big sandy ledge, with room for a dozen souls. This has been retrobolted, so what used to be iffy protection is now safer. There is also a 5.7/8 bolted variation that climbs straight up the face. 5.6
Pitch 2: On the right hand side of the ledge is a great hand crack. Follow this crack, keeping right when it splits. The next belay is inside the hole, which isn't as cozy as it looks from the ground. Natural anchor consisting of mid-size cams in a rather hollow sounding flake. 5.7
Pitch 3: Swing out left of the hole, and follow wider cracks up. There is a crunchy lieback/overhang section about 10-15 feet higher which may be the technical, but surely is the pyschological crux for the rock flexes noticeably. The flake on the left is not to be trusted. Move through this section quickly and smoothly. Lieback and wiggle for another 30 feet, then follow more blocky rock and cracks to the left hand side of the gully. A single bolt keeps the rope from dragging through all the dirt and loose rock in this large gully. Walk the ledge 20 feet and move up the 4th class squeeze chimney. Belay immediately above. Hint: don't try to shout anything down to your belayer after leading this pitch. He\She is in the belay hole, and is totally deaf to you.5.7
4th class junk leads to the summit.
Descent, easy paths down the opposite side lead down. Skip the first gully, it doesn't reach the valley floor. Keep left, and do not descend until you can see the entire route down. Head left and walk around the Smith Rock group along the river, or head right and up over asterisk pass.
Cams cams cams. The funky cracks of Smith love cams, and hate passive pro. A few medium and large stoppers are useful for anchors. This route needs hand to fist size cams. Bring doubles of 1.5 to 3 inch size cams, triple if possible. Some slings for rope drag, but not many, the route is pretty much straight up.