Originally Posted by RV10inOz
Its interesting stuff drag, because you can't see or measure it, well not easily in flight apart from speed.
I have a stubby Transponder, 2 x VHFs, GPS, Stormscope (huge) and the VOR/ILS rabbit ears in the tail. They will be all huge drag items for sure.
Spinner drag is an interesting one, and a very good point. I might have a look at that a bit closer and investigate sealing it.
We noticed about 4 knots in removing the tie down rings alone.
There are a few things that we did different very early in the build trying to get the most speed possible in a practical manner. I was not out to make an all out race plane but something that I can use and service in a practical manner.
The cooling system was modified using a plenum with fiberglass transitions molded to capture all of the air and force it into the plenum without leaking into the lower cowl.
Under the engine we tried to provide a transition to smooth the airflow flowing out the exit side of the cowl. (not shown in the pics. all of the gaps were sealed with RTV)
This along with a modification to the lower cowl to slightly increase the outlet area provides enough cooling to keep the engine cool without using the factory "louvers" under the cowl. I think they are draggy but the effects are unknown to me.
We closed all of the ends on the control surfaces.
Closed the hinge gaps like this
Also we sealed every hole that we could find in the wing root area. control rods, spar web gap etc. This is to keep air from in-filtering from the tail and exiting the low pressure area in the wing root and door area..
The wheel fairings are extra tight around the tires.
I only have 1 comm antenna on the belly and 1 transponder blade. the rest of the antennas are internal.
I ordered new ECI cyl's that were flow matched. worth it? i dont know..
The area that Pierre talked about on the spinner is cut very close to the blades.
The spinner is very close to the cowl (really its to close but its not rubbing so i left it like it worked out).
It is not really 1 thing that makes airplanes go faster. It is a lot of small things that finally add up.
Also note that I accept a slightly higher CHT that some do. My limit is 400 F in cruise so I MIGHT be accepting accelerated engine wear due to heat???? In my case I accept the risk--not for everyone.