Began to work the rear spars. Studied the plans and had to do some searching in my storage areas to find all the parts called out in the plans. Began by edge fiinshing the W-707 E and F doubler plates for both spars. Moved on to edge finishing the W-707A-R rear spar channel for the right wing. Filed burrs and edge finished with a scotch brite wheel in a 90 degree pneumatic grinder.