flyrotary@lancaironline.net Mailing List Archive

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Indeed there is more than one way. However, without the inlet moved out of the boundary layer, this NACA study would indicate that you may need internal guide vans to overcome the detrimental effect of ingesting the boundary layer.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930093223_1993093223.pdf

----- Original Message -----

From: Mike Wills

To: Rotary motors in aircraft

Sent: Friday, February 29, 2008 10:34 PM

Subject: [FlyRotary] Re: New (old) guy on list

Just a comment on the boundary layer splitter. Take a look at Strega and Voodoo, two of the fastest 51s around and you'll see there is no boundary layer splitter. Obviously more than one way to skin a cat.

I looked at all sorts of ways to locate coolers anyplace other than the cowl because of the (mostly anecdotal or theoretical) evidence on the web. But for me it was a non-starter. No way to run coolant lines or add coolers without structural mods to the RV and I wasnt willing to go that far. Also, I'd actually like to taxi without having to shut down to let the engine cool. :-)

I compromised by mounting coolers below the engine and eliminating the stock RV cowl. I doubt it'll be any less draggy than a good RV cheek cowl but it will stand out in a crowd.

Mike

----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

Sent: Friday, February 29, 2008 12:16 PM

Subject: [FlyRotary] Re: New (old) guy on list

Greg, there has been a lot of debate among heat exchange professionals about whether the P-51 cooling system resulted in any net thrust( Meredith effect ). There are numerous web sites you can read about the debate if interested.

http://yarchive.net/mil/laminar_flow.html

http://yarchive.net/mil/p51.html

It appears to me that what can be said about the P-51 cooling system is that at high airspeeds and high power settings it was very effective and provided a good (minimum) drag factor. However, be aware that on the ground it was less effective and care had to be paid to coolant temps when taxing in warm weather.

However, the P-51 style design requires some very specific attention to certain factors (even the North American P-51 engineers didn't get it right the first time {:>)). Two of the highest factors on the priority list is to:

1. Make certain your cooling inlet is outside the fuselage boundary layer - note that the mouth of the P-51 intake appears 3-4" away from the fuselage. If you do not stand-off the opening then you may need to put guide vanes between inlet and core. I am sending a NACA report direct to your e mails as it is too large for a Rotary Posting. I would think it easier to stand it off - if you have that option.

2. Make certain you have minimum flow separation near the entrance. Easy to say, harder to implement. Drop me a line off the list and I will give you my viewpoint of what it takes.

Some interesting viewpoints here on cooling in general

http://groups.google.com/group/rec.aviation.homebuilt/browse_thread/thread/aa11e7e47621e34b/eac8082eecac905b%23eac8082eecac905b

Another source that appears to have good information

http://glasairproject.com/AirSig/CoolingSystems/cooling2/CoolingSystems2.htm

Ed

----- Original Message -----

From: Greg Ward

To: Rotary motors in aircraft

Sent: Friday, February 29, 2008 11:50 AM

Subject: [FlyRotary] Re: New (old) guy on list

I would also be really interested in seeing some others cooling solutions. I was told that 40% of the Lancair's drag is in the cooling drag, and I am contemplating a belly scoop A la' P-51, and have created controversy about how much that configuration will add to the drag factor. In other words, I might get great cooling at a slower speed? Supposedly the P-51 configuration creates enough thrust to overcome around 90% of the drag created, but I would like to confirm that before I go through the process of designing and building the damn thing.......(:-) Call me lazy...

Greg Ward

20B Lancair in Progress

----- Original Message -----

From: Mike Wills

To: Rotary motors in aircraft

Sent: Friday, February 29, 2008 7:26 AM

Subject: [FlyRotary] Re: New (old) guy on list

Well, it's not as beautiful as it once was. Had to add some ugly bumps for exhaust clearance. Finally threw in the towel on a clean oil cooler install and added a second scoop and stock RX7 cooler below the rad inlet.

Can I attach pictures here?

At the moment it appears during full power ground runs that I have excess cooling capacity, both oil and water. Never been over 180 on either. Which brings me to thinking (again) about oil/water heat exchangers. Has anyone successfully implemented one? If so what are you using? I may eventually be able to get rid of that second scoop.

Mike

----- Original Message -----

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Thursday, February 28, 2008 8:57 PM

Subject: [FlyRotary] Re: New (old) guy on list

I was on this list years ago when it first started up. Job change and other issues slowed progress on my project and I unsubscribed.

Hey, Mike's Back :-)

Good to hear from you again. Can't wait until all the new folks see that beautiful cowl :-)

Cheers,

Rusty