Stealth Pilot wrote in
:

On Sat, 12 Jul 2008 18:25:42 +0000 (UTC), Bertie the Bunyip
wrote:


I got 5 extra knots in cruise for nothing when I cleaned up the
prop and got the shape right the first time. the damaged leading
edge paint just drops me back to the original slower cruise.

Stealth Pilot

Five knots is a huge gain. I remember reading some years ago of a
homebuilt getting a new paint job, and the color change on the
wings
led to a paint 'bump' or seam near the leading edge which so
altered
the airflow the airplane could not fly (probably changed the
stagnation line).

Sounds like a myth to me. How thick is a paint line?

Still, that big a change in cruise speed seems
remarkable.

I'd say unlikely.

Not in an airplane like the Tailwind. A small change in somethign like
a
Cherokee might not get you much, though a series of changes will get
you
quite a lot evn in one of those, but something that acts more of a
whole
like a talwind or a Midget mustang can be hugely affected by one
single
ingredient being out.


Bertie

on an allied note there was a cherokee that had been flown up in the
North of Australia all it's life. every year to protect the aircraft
the owner had hand painted it. the paint eventually looked so crappy
that when it was sold the new owner immediately put it into the paint
shop.

the painters were intrigued by the thickness of the paint. on careful
examination made easier because each year it was painted a new colour
the painters discovered that it had 26 distinct layers of paint.
needless to say the professional paint job removed all of this re
alodined the skin and applied the thin paint coats.

the new owner reported that after repainting it felt like the aircraft
had an extra 50 horsepower.

paint matters.

On a prop, definitely. I'm sure the thing was getting a substantial
boost in HP if the revs were down static!

Bertie