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Tracy,
this was one of my hang-ups with PL.
I recommended to look at the drag reduction a
Mustang II builder and Dave Anders with his RV-4 achieved, by using correct
inlet/outlet size and using exhaust augmentation to further reduce
drag.
His comment was: Aircooled engine - less back
pressure....
I argued: Don't believe it - at the end of the day
we all have "air-cooled" engines, even rejecting about the same amount of waste
heat, just a matter of transmission to the air.
Whatever works for the Lycosaurus guys works for us
too, just have to implement it according to our engines.
Cory Bird's "Symmetry" is also a piece of
cooling-art to look at!!
Thomas Jakits
----- Original Message -----
Sent: Saturday, March 11, 2006 10:14
AM
Subject: [FlyRotary] Re: NACA's, Cooling
and Sport Aviation Mag..
Just a comment on one often repeated point: "There is less pressure
differential [on an aircooled engine] than with a radiator". This
factor is a major one in the decisions/arguments made regarding cooling
of aircraft engines.
The problem is that I have seen absolutely no empirical evidence to
support it and some which refutes it. For example, some Lycoming
powered RV flyers locate a backup airspeed indicator pickup inside the
cooling plenum over the cooling fins. They report that it reads within a
few MPH of the primary ASI fed from the pitot tube. This indicates that
almost full dynamic pressure is being recovered from the airstream and that
pressure differential is at least as much as seen on radiator
installations.
Bottom line is that reduced backpressure is NOT one of the advantages of
an aircooled engine. At least that is the working premise I go on when
making cooling decisions on my airplane. If I'm wrong, I'd like to
know. Anyone have data supporting/refuting this?
Tracy
----- Original Message -----
Sent: Friday, March 10, 2006 1:25
AM
Subject: [FlyRotary] Re: NACA's,
Cooling and Sport Aviation Mag..
Group,
The problem with submerged inlets, and Buly is correct to mention that
means flush with the surface, is that they do not handle back pressure well.
Ed A posted the original NACA data and their conclusion was that submerged
inlets don't work well with RADIATORS. The comments PL has been making are
only to re-publish the data. If you do a smoke tunnel test on submerged
inlets you will find that once enough pressure is built up they will "flip"
and hardly take in any air at all. The actual NACA ducts also have the
carefully designed lips, or rounded edges to train the boundry layer into
the inlet. The full profile defined by the NACA is rarely used. Most of the
inlets we see are some attempt at looking like a NACA inlet, without the
trouble of actually BEING a NACA inlet. We used to call this "eyeball
engineering." Aircooled engines do work better with NACA inlets as there is
less pressure differential than with a radiator. This doesn't mean they will
never work, just that the NACA didn't recomend their use with a
radiator/heat exchanger.
Bill Jepson
In a message dated 3/9/2006 8:24:30 PM Pacific Standard Time,
atlasyts@bellsouth.net writes:
John, would you stop calling it a NACA scoop. Remove the big
raised
lip and make it flat. Than come and report to us. Your
inlet is half
submerged and half raised scoop. NACA is a flush
with the surface
SUBMERGED inlet.
Buly
On Mar 9,
2006, at 10:44 PM, John Slade wrote:
> Dave,
> My only
cooling intake is the plans Cozy IV NACA.
> Cooling has never been a
problem.
> Regards,
> John
>
> David Staten
wrote:
>> At the risk of invoking PL's name, anyone else read
this months
>> Sport Aviation mag from EAA, and notice an
article on cooling that
>> seems to indicate that NACA's
are acceptable and adequate for
>> aircraft cooling needs?
I have no idea regarding the authors
>> credentials, and I
no longer monitor PL's "newsletter".. I was
>> curious
more than anything else... Pauls reaction, others
>>
reactions, etc.
>>
>> Translation.. yes.. I'm stirring
the pot/Trolling... I figure if
>> we are using NACA's on
the Velocity, that makes us somewhat of a
>> NACA
supporter..
>>
>> Dave
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