Parasitic drag question

On Fri, 12 Mar 2004 08:41:08 +1000, "Derek Anderson"
wrote:

We are currently test flying an all fiber-glass experimental plane in an
unpainted state and wondered if any of you have done the same and
experienced as much as a 10% increase in air speed and improved climb rate
after painting your planes.
I know most of you are happy to wait until your pride and joy is painted but
we opted to test fly in the raw. The manufacturer who has a similar plane is
achieving around 10 knots better speed for the same revolutions, at 4,600
rpm on a Subaru conversion with a 2:1 reduction he gets 100 knots and we are
only just getting 90. The only difference in configuration is the addition
of front wheel fairing and three leg fairings plus nice shiny paint. Our
climb rate is also very low compared to predictions. It will be several
months before it is painted and back in the air so am asking the group.
Replies appreciated. Derek.

Several people have given you good replies Derek. Here's my input.

Do your airplane and the manufacturers airplane weigh the same? Is
your instrument panel loaded with goodies that add weight?

Does your engine make exactly as much power as his does? Are you both
using exactly the same prop? Does the prop have adjustable pitch? If
so, is it exactly the same as where the manufacturer has set it?

Not having fairings on the gear legs or wheels will, as others have
mentioned, make a substantial difference in cruising speed, but not so
much with climb. Weight , engine output and prop make the difference
there.

Did you build the engine yourself, or is it a firewall forward kind of
powerplant? If you built it yourself, did you do all the
modifications the manufacturer has done?

No two homebuilt airplanes are ever exactly the same.

Corky Scott