Hey again Fred!
I keep reading that cooling drag can be as much as 35% of the entire
drag of the aircraft.
That could be a big factor on Alex's plane as the hot air coming off the rad
is exiting in a very
clean area - the sides of the cowling. This supposedly is the most
efficient exit location, especially
if the exhaust air is accelerated back to the freestream velocity with a
converging duct right
before it exits. This way minimal drag is created by the cooling system.
I have a diverging bell shaped inlet duct about 15" long that slows and
pressurizes the incoming air before the rad and also a converging duct after
the rad to accelerate the hot air back to free stream
velocity. Unfortunately, this duct exits underneath right in front of the
monowheel in a very
dirty area and probably is not helping. I may try to redesign my exit duct
to go out the sides
of the cowling, or possibly duct the exit air underneath and on past the
monowheel before it
exits.
Glenn
>From: "Fred Fillinger" <n3eu@comcast.net>
>Reply-To: europa-list@matronics.com
>To: <europa-list@matronics.com>
>Subject: Re: Europa-List: Jabiru as alterantive
>Date: Thu, 11 Aug 2005 16:33:22 -0400
>
>
> >
> > Hey Fred!
> > Yeah, seems high to me as well, but I'm getting an
>honest 172-175 mph
> > GPS at 7500 ft with my 125 hp rated EA81
>
>That's more reasonable within the math at that altitude,
>Glenn. Dr. Sighard Hoerner is again motionless in his
>grave! ;-)
>
> > and I do not have the slick underbody fairings
> > as on Alex's plane. When your'e trying to go fast,
> > the aero mods can help more than more hp. Like
> > this guy who went 214 mph on 65 hp!
> >
> > http://www.ar-5.com/sportav93.html
> > The Arnold AR-5
>
>A number of aerodynamic mods individually may have to add
>up, before meaningful things start to happen. The main
>thing Arnold arguably did was achieve laminar flow back to a
>phenomenal 70% of chord, and claims to have proven so by the
>usual methods. Hoerner, in the days before fiberglass, said
>55% was pretty good construction methods. Also mimimal
>cooling drag. He also had a really small prop with a really
>big bite in pitch -- not a very practical airplane, but some
>say a Cessna 150 ain't either!
>
>Reg,
>Fred F.
>
>
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