Hard to say, Ernest. So many other factors come to play such as size, thickness, fin density of the radiator.  However, I do recall that when Tracy Crook reported on the pressure differential across his GM cores it was on the order of 5" - 5 1/2"  of water.  I think the figure of 1" during climbout may not be good news - but again as you point out this is on a surface and not in a duct.

Ed A

----- Original Message ----- From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, August 02, 2005 5:36 PM
Subject: [FlyRotary] Pressure differential

Another Delta builder has done some testing and come back to me with some hard data for the pressure differential between the wheel wells and the wing's trailing edge.  A mamometer with a line terminated in both places gave:
- 1/16" differential during taxi
- 1.25" takeoff/touchdown
- 1" during climb out (100 mph IAS)
- 2.25" with the gear down
- 2" during base and final

I sure someone has, but I don't remember anyone quoting the pressure differential across their radiators.  Do these numbers look workable?  The airplane doesn't have a scoop dropping down as tested, and the front edge of the wheel well is squared off.  I would expect these modifications to significantly increase the numbers, but if this is sufficient neither one may be necessary.

These numbers are not from a duct with air passing through it, but just points on the solid surface of the aircraft.  Will that make a huge difference?

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