Starmax's gorgeous P-51D is a pretty slow as shipped. The plane gets a significant speed boost from a 5-cell upgrade alone, but the 4S-advertised motor sometimes balks on static runs to include takeoff. In the air it seems to run fine and the big 4-blade sounds great. But is it fast enough to evoke thoughts of a V12 Merlin? Maybe not.
At Z8RC, we don't cope well with sluggish warbirds, especially P-51Ds. Call it a mental disorder. It actually hurts to watch a vicious warbird airframe quietly paddling along like a broken wild animal that has lost its will to fight.
Starmax's nicely scale P-51D airframe screams for more speed. It would one cruel act of torture to force the big Mustang to play nice, like some 1980's Chrysler K-car pretending that what people really crave is slow motion efficiency and resource squandering sensibility. As if watering down products to a state of uselessness magically makes them more desirable. It all makes me want to puke.
In an attempt to give the Mustang a proper personality, I learned a two things. First, it's pretty hard to make a 63" chunk of foam hurdle through space. Second, it's pretty hard to make a 63" chunk of foam hurdle through space. Enter the well built Rimfire .60, 50-55-650 Kv electric motor. It shares guts with the lower kV Rimfire .80 50-55-500 Kv . The Kv gearing could be addressed alternatively with prop pitch, so the two are close cousins. Aside from being a milled metal monster, the Rimfire motor is surprisingly efficient, not like the failed Power 46 experiment which guzzled electrons to little effect.
I think the .60 upgrade was a success. This flight used a 14x8 Master Airscrew K-series prop and is running on 6S:
The Rimfire .60 was easy to install. After unscrewing and removing the stock motor and mount, I sandwiched a standard 1" diameter PVC pipe coupler (50 cents) behind the Rimfire's beefy X mount bracket and the firewall. Then I drove four long deck screws through the holes in the X bracket, past the PVC spacer and into the firewall, secured with a dab of Gorilla Glue on the point of each screw. Done.