George,

The Thorpe 18 used side exits, and it cooled quite well. Several aircra= ft=20 have used this system with success. The merge area is fairly high pressure=20 though and you create some drag. Not the end of the world or anything but=20 significant. The finning of most radiators causes plenty of turbulence. The=20 ideal ducting has just enough pressure drop across the radiator to ensure go= od=20 mass flow. The heated air should help to accelerate the flow to "buy back" s= ome=20 of the cooling drag. It was said the last P-51 ducting actually added thrust= ,=20 but the info I've read from North American said that zero was the best you c= ould=20 hope for. Still if you think about it a net zero or very small cooling drag=20= to=20 cool 1200 HP is a pretty big achievement in itself! This was a plane=20 designed for water cooling from the outset and the results speak for themsel= ves.=20 Getting back to the chin scoop George, the location does provide high pressu= re=20 but at the penalty of MUCH higher drag. The prototype P-40 had an under-fuse= lage=20 radiator. Not the same as the 51 but still much better than the gapping mout= h=20 that was forced upon them by the AAC! In the info I read the production plan= e=20 was 10 knots slower! Several of the German designs used the shark mouth chin= =20 inlet and they were the slowest. (Stuka anyone?) Later wing mounted radiator= s=20 like the 109 were much better. The Spitfire used an almost identical radiato= r=20 location. If the RV's didn't have the tanks there an in wing system would be= a=20 good option too. FWIW

Bill Jepson

In a message dated 11/8/2007 1:56:41 PM Pacific Standard Time,=20 lendich@optusnet.com.au writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

Ed and Bill,

I was just thinking about the vertical si= de rads=20 ducted to the outside. I have seen this work very well in smaller pla= nes=20 with smaller engines, but am unsure how that might translate to larger=20 installations. I think they work so well because being so close to the air= =20 stream being on the side walls of the cowl, that the slip stream actually=20 creates a suction, or low pressure area (over the airfoil shaped outlet bu= mp),=20 which enhances the flow through the rads. This could be somethin= g=20 lacking in some installations.

I did ask PL some time ago if the chin sc= oop was=20 in a high pressure area, which I think it is, which might make it less=20 effective compared to side outlets.

That's not discounting Ed's c= omments=20 on inlet pressure, but it may enhance pressure drop across the core, if we= can=20 target low pressure areas for exits.

George (down under)