One of the fun things about the iconic nature of the Porsche 917 is that it must be one of the most documented race cars in history. "Stuff" keeps popping up. Apparently nobody threw anything away. Or maybe by the time they thought to pitch some files the car was already legendary and they thought again. Thus the blind alleys and "...meh's..." of 917 development have been preserved. They illustrate the fact that all race cars are constantly being developed. ("No battle plan survives first contact with the enemy.") With most race cars, by the time secret tweaks that didn't work out might become public, nobody cares anyway. The 917 is immune to that indifference.
The story of the Horsman (Wyer) K-tail for the 917 is fairly well-known because it transformed the 917 from a car with diabolical handling into an instant winner. The story of Ferdinand Piech's development of the LH tail (and indeed, the entire car's shape) over three years are less well-known but available to 917 geeks. So are accounts of "The Pink Pig," commissioned by Piech from S.E.R.A. Finally, we know about the Wyer center wing[let] tail, which provided slightly more downforce with an acceptable drag penalty, and Porsche's 1971 fin tail, which provided slightly less drag, with acceptably lower downforce. (Bonus trivia points for geeks who know about Wyer's "one race only" full-width spoiler tail used at Spa-Francorchamps in 1970.)
And now, the news (at least to me): Here are three Wyer body configurations got up for testing in the M.I.R.A. wind tunnel, presumably in 1970, probably by John Horsman. Evidently none of them measured up to the drag/downforce ratio of the center wing tail. So they were not used, or passed along to Porsche.
|Here the center "rear visibility slot" is filled in. The rear edge is similar to the "one race only" full-width spoiler used|
at Spa-Francorchamps in 1970 except that it lacks the slight spoiler upsweep.