George,

The Thorpe 18 used side exits, and it cooled quite well. Several aircraft have used this system with success. The merge area is fairly high pressure though and you create some drag. Not the end of the world or anything but significant. The finning of most radiators causes plenty of turbulence. The ideal ducting has just enough pressure drop across the radiator to ensure good mass flow. The heated air should help to accelerate the flow to "buy back" some of the cooling drag. It was said the last P-51 ducting actually added thrust, but the info I've read from North American said that zero was the best you could hope for. Still if you think about it a net zero or very small cooling drag to cool 1200 HP is a pretty big achievement in itself! This was a plane designed for water cooling from the outset and the results speak for themselves. Getting back to the chin scoop George, the location does provide high pressure but at the penalty of MUCH higher drag. The prototype P-40 had an under-fuselage radiator. Not the same as the 51 but still much better than the gapping mouth that was forced upon them by the AAC! In the info I read the production plane was 10 knots slower! Several of the German designs used the shark mouth chin inlet and they were the slowest. (Stuka anyone?) Later wing mounted radiators like the 109 were much better. The Spitfire used an almost identical radiator location. If the RV's didn't have the tanks there an in wing system would be a good option too. FWIW

Bill Jepson

 

In a message dated 11/8/2007 1:56:41 PM Pacific Standard Time, lendich@optusnet.com.au writes: