Monty,
I
get the impression that you think this is about ‘P-51 envy’ or
something.
For
starters, the P-51 style scoop is part of the original plans. That’s per Burt.
I have seen where many have opted for the NACA style scoop but the more I look
into it the more sense the original plans method makes to
me.
The
sizing-to-hp has already been calculated to the best of my ability using the
available resources. That is a part of the equation that can be applied to any
approach and is an important foundation.
The
biggest issue I have centers around a good diffuser and cooling exhaust
arrangement. To this point, I have heard all sorts of theories and various
‘bar napkin’ graphics but the original P-51 drawings are the only source I
have found for a professionally engineered and proven product. That said, I
feel most comfortable pursuing this approach as a solution for my
project. Because the drawings have been converted to CAD, the calculations can
be performed in a more accurate fashion and the design altered prior to
printing templates. I’ll have more on that later.
The
biggest difference in my approach vs. what others have done in the past is
that I am documenting everything as I go and will make that documentation as
well as the CAD drawings available for others to analyze as a possible
approach.
Another
advantage of reviewing the P-51 drawings is that it has altered my approach to
implementing the design. I anticipate the scoop being composed of three
segment.
A
front section starting just forward of the oil cooler and the portion aft of
that point being divided into a top and bottom section.
By
building it this way, I can rebuild various configurations of the air inlet
and swap them out with very little down time.
One
of the big differences in my project vs. other canard aircraft is the fact
that I have an area behind the rear seat (hell hole) that is available to me.
I can actually tuck part of my radiator into this area and avoid at least some
of the projection of the scoop as it relates to the
profile.
As
is the case with the original P-51 design, the exhaust doors for both the
radiator and the oil cooler are in-flight adjustable.
All
that said, there comes a point where the research stops and production begins.
I would be very surprised if this turns out to be a hit on the first shot, but
it should be very close.
T
Mann
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of MONTY
ROBERTS
Sent: Friday, January 29, 2010 10:18 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Tiff to CAD
Software
Not trying to rain
on your parade, but why do you think that something designed to cool a 1500 hp
WW2 fighter at speeds over 300 mph and then scaled to fit in your
airframe is what you need for your
application?
You should
calculate what your particular situation needs and go from there. The
math is not that hard, in fact I think Ed has a spreadsheet he would probably
be willing to share if you asked nicely. I think he would even run some
numbers for you. If you want to make it look like the P51 installation fine,
but size all the radiators, inlets and exits for your speed, altitude and
power levels. Then draw the P51 like scoop around that and see if it
still fits.
1.) determine how
much HP you plan to make continuously.
2.) figure out how
much heat will be rejected at that HP.
3.) figure out how
fast your airplane will go with that much HP.
4.) size inlet and
exit accordingly.
5.) Check over
range of altitudes repeat step 4 and 5.
6.) look at hot day
takeoff and climb. size max exit opening for that.
7.) compare your
results to the other flying examples closest to your application for a sanity
check
8.) If you are the
outlier you better understand why or start over
I would look very
closely at what Al G has done as well as others successfully flying canard
aircraft with rotaries. They have much more in common with your application
than the P51.