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.