Mid-air occurred at uncontrolled airport with the S-2B executing right traffic, as published, and the C-172 executing a long final or an arcing left turn to final. Both aircraft were attempting to land on runway 17R. Accident occurred during late afternoon and there was considerable sun glare. The S-2B came out of the sun and collided with the right side of the C-172 empennage, causing the tail to sever. At the time, C-172 was wings level in a slight descent, S-2B was in a right bank, slight nose high attitude, descending. C-172 crashed in an open field and S-2B regained control and landed without further damage. Witnesses stated that C-172 did not take evasive action and pilots in S-2B stated that they did not see the C-172 until after the collision. Airport manager did not recall hearing either aircraft transmit on UNICOM. Sun glare would have made acquisition of S-2B difficult for C-172 pilot and restricted visibility out of S-2B affected visual acquisition of C-172 by its pilots.