<... What is roster tail drag...>
Visualize the rooster tail behind a speed boat.  Anything (exhaust, cooling air, etc.) exiting the airplane normal to air flow direction acts like [fairly flexible] rubber hose sticking out the side.  Vari-EZs trying to simplify their exhaust systems simply ran a short header pipe straight to the cowl.  Cost them >5 kts.  Shirl Dickey's V-8 E-Rzcer had exhaust stubs straight out the cowl.  He had vibration from hell for two years.  He tried balancing EVERYTHING, from the engine output flange to the prop; drive shaft, PSRU, etc.  Nothing worked.  He then installed 4 into 1 headers going out at a shallow angle and it all went away.  The exhaust pulses were traveling 4 or 5 feet and hitting the prop with enough force to make it vibrate.  Folks have reported speed increase just from seriously lowering the angle that air exits the cowl.

Effect to be bigger than it seems ... not obvious, but easy to fix ... Jim S.

Marko Bewersdorff wrote:

 What is roster tail drag? how and where does it get created? Is there anything about that written up on the net?I'd like to know since I'm in the process of figuring out where to put my radiators in the Long EZ.ThanksMarko