So following Shadow-Greg's PW R-2000 suggestion, and Shadow-Jeff's encouragement, I have cobbled together some Hawk 87A-R2000 sketches and calculations.
(See linked sketch for reference: https://www.flickr.c...posted-public/ )
Engine dry weight comparison:
Allison V-1710-81, 1,352-lb
Packard V-1650, 1,640-lb
PW R-2800, 2,340-lb
PW R-2000, 1,585-lb
So dry weight of R-2000 is about 55-lb lighter than the Packard-Merlin, and about 230-lb heavier than the Allison.
In the attached sketch, I have used the DHC-4 Caribou engine cowl, but turned upside down, with the air inlet on the chin side. This keeps the pilot eye-line clear over the top of the cowl.... and I quite like the looks of the chin-mounted intake scoop. I have moved the R-2000 closer to the firewall than the R-2800 location, but left some extra room to accommodate a - possibly - larger supercharger. This results in the approximate engine CG at 4-ft 9.2-in forward of the assumed 40% chord Centre of Lift. Remember that the assumed CG for both the Allison and Packard-Merlin was at 5-ft forward of 40% chord; compared with the R-2800 CG at 5-ft 8-in forward of 40% chord.
This roughly equates to the R-2000 being able to be used on the P-40M airframe with very little ballast weight near the tail.
I have very little detail as to what the cooling air requirements were for the Caribou, so have kept the engine nacelle as-is for now. The red-lines are my interpretation of streamline possibilities from nacelle back to fuselage aft of the firewall. Thrust line of the R-2000 (as drawn) is about 6.5-in below that of the V-1710, but about the same higher than assumed for the R-2800. We know the Hawk 75 had been tested with 4-bladed props, so that was a possible get-out-of-jail-card for ground clearance issues.
R-2000 prototyped circa 1940. Development of R-2000 was delayed as R-2800 seemed more useful and thus higher priority. I guess, had there been a real requirement, R-2000 could have been developed faster at a shadow factory with minimal delay to the R-2800.
So what do you think of the Hawk 87A-R2000?
....more fun later:
I found some cool drawings of the Hawk 81A-P&W Sp on the internet.
(Ref: http://www.wunderwaf.../52/Draw/18.jpg )
Taking the drawing on the front cover of the Pratt & Whitney R-2000-24 Maintenance Manual, I have approximated the scale based on the R-2000 diameter of 1.247m.
Cobbled together comparison sketch is also in the flikr-page linked above. It's the Hawk 81A-R2000_a2 sketch with plan and elevation.
The R-2000 seems to fit vertically into the allocated space for the R-1830, though internally, some modification to the air intake ducting may be required. Engine thrust line seems to be maintained as per the R-1830 without problem.
In the plan view, I don't have an equivalent plan sketch of the R-2000, so I have taken the engine diameter from the side-elevation and replicated it in the vertical view. It seems to fit - just - into the relative location, though it's a tight fit on the drawing. If the scaling of the various components is correct, then the sides of the Hawk 81A-PW-Sp may need widening or perhaps local cylinder "bumps" as per the Macchi C.200.
Still, seems a reasonable fit of engine into airframe. Probably stay with the Hawk 81 unlengthened fuselage (as seen here) for a more balanced look.
Edited by bearoutwest, 11 February 2018 - 07:50 AM.