+1 (for what that's worth...)

IIRC, Tracy has mentioned several times that he doesn't worry too much about ground cooling, for the reasons Lynn just mentioned. 'If it cools on the ground, it'll be draggy in the air.'

Anyone calculated how much the radiated heat from the engine block affects radiator efficiency, when the face of the rad can 'see' the block?

Charlie

On 12/28/2017 8:07 PM, Subscriber Lehanover@aol.com wrote:

Are these cooling tests being done at speed, say 60 to 70 MPH? Or, stationary?  It only needs to cool long enough to get to the runway. Put some tufts on wires right behind the prop and long enough to get into the ducting. I bet almost nothing flows into the ducting. Mount a pancake fan behind the radiator to cool on the ground. Some of the spiral flow from the prop will defeat the straight sides of the ducting. Ram air at flying speed is completely different. Most added temperature shows up in the oil with high power settings. The racer cooling at low speed is just not adequate. But once you hit the first straight and go over 100 MPH

(top speed 146) the cooling is great. Make one change at a time. Make it a big change. Record the instruments on video. Just like running the dyno. Run a bit rich on the ground. Say 1600 degrees or less EGT. This will help a bit.

Lynn E. Hanover

 

In a message dated 12/28/2017 7:55:29 P.M. Eastern Standard Time, flyrotary@lancaironline.net writes:

Steve

I suspect it’s #2. Steve B’s email has a wealth of information and points to airflow. To prove it layup a quick but reasonable shaped duct and test it with the cowl off. I would start with a 28 sq or large inlet. 30% of the core face would be a good place to start testing.

I’ve only seen Tracy takeoff in the RV8 once. But he was not using anywhere near full throttle. He did a lot of work on the inlets but I’m not sure he can use all 300HP in the summer. 

Bobby



Sent from my iPad

> On Dec 28, 2017, at 5:13 PM, Stephen Izett stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:
>
> Hi Guys
>
> Thanks for the replies
>
> Our water inlet is small (Standard Glasair) - modelled of Tracy’s RV8 20b
> I understood he had a round right cheek inlet of 5.25” giving him 22 in^2 to his water rad for 300hp in Florida temps.
> For the two rotor -> 2/3rd of 22 is <15. We have >16 for <200hp
>
> My concern is the delta T’s.
> Yesterday at 1800rpm I was seeing 12F across oil and 6F across the water. Previously I’d seen this as high as 18F and 9F not sure why so low yesterday.
> What do others see on the ground at idle?
> Does anyone have good pressure data on the ground. Idle and power settings?
>
> Are these low due to:
> 1. Water flow due to cooling system design or air trapped.
> 2. Air flow due to small inlet, compounded by a prop that doesn’t have much blade near the spinner.
>
> I’ll look at some further baffling of the Rad to exit but cant see this helping at idle air speeds unless I duct the exit low pressure direct to the back of the core.
>
> I’ll send further photos
> Thanks
> Steve
>
> Steve<3.JPG>
> <Cowl exit.jpg>

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