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Comment by Patrick Hoyt on August 26, 2021 at 9:46am

I built a fiberglass fairing in that area that yielded good performance results (about 6mph).

In my case, I have a radiator hanging between the main gear, a header tank behind the radiator (beneath the fuselage), and fuel pumps/lines/wiring behind that (all external to the fuselage).

I made a wood form to get the shape, and did a wet layup over that (as I recall, I used a fineness ratio of 4:1 just to keep it simple). It's ugly if you crawl under the fuselage and look closely, but it's efficient (did some tuft testing). Also built an access panel and a cooling duct into it (and installed a temperature sensor back there to keep tabs on fuel temperature).

Also did some minor cleanup of minor protrusions in the aft bottom area (ELT bolts sticking into the air, etc). I suspect that drag reduction on the underside of the airframe is often overlooked.

Pictures here: http://www.zenith.aero/photo/albums/fuel-system-v2-0

and here: http://www.zenith.aero/photo/albums/n63pz-v2-0

- Pat