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Originally Posted by Crumpp
Good summary, Sternjager II and all.
In general, yes but as long as the designer pays attention to the installation of an aircooled motor, the Cd0 is not necessarily higher. Look at the Zeke, Corsair, F6F Hellcat, or Focke Wulf series. All have average to below average Cd0 for the period. In fact very few inline installations approached the Cd0 of the Zeke.
Consequently there are inline installations that have much higher drag than radials.
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yeah, but in the end of the day you need a higher number of HP to compensate for the drag, and even if you implement ram fans like on the FW190, you still need air to go through the cyl heads and out from the sides in a very turbulent fashion. No matter how "polished" your radial design is, it's still a radial
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Only when comparing dry weights. Add in the radiators and coolant and their is little to choose in terms of weight.
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I suppose it depends on the specific plane really. A Thunderbolt would have a chunky turbo supercharger installed in the fuselage and oil coolers in the engine cowl, that adds a lot of weight as well. Let's not forget that the Merlin has a higher power to weight ratio other than a lighter dry weight.
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In terms of TBO, liquid cooling wins out. Temperatures are much more stable across the engine in comparison to air cooled engines. Air cooled cylinders can vary over 100 degrees in normal operation just from fuel metering alone.
http://www.liquidcooledairpower.com/lc-longertbo.shtml
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mmmmh, again, it
really depends on engines. It's not a good idea to run a Merlin, even with transport heads, beyond 600 hours, while a well maintained radial has more than double that TBO. In fact, apart for certain non certified ones, I can't think of any radial with a TBO below 500 hours, while there are many many many inlines that are below that (the DB family being the extreme example).
Temperature is not the only factor, and whilst a coolant system failure can be catastrophic, a radial can survive prohibitive temperatures, thermal shock and component failure, and
still do its job.