I have totally stock Naca on Cozy. Just added the vortex generators as
John describes (I think it's 40 deg included angle).

I found air flowed in wrong direction often upon takeoff. It would both
take time and playing around with aircraft attitude to get it to flow in
correct direction. There after, it did ok. Adding erics vg's increased
total pressure differential and totally eliminated that initial flow
problem. In hind sight, this makes sense. The cozy has long flat bottom.
NACA at rear of craft. Thick boundary layer at that location. So the vg's
break thru the boundary layer allowing the NACA to do it's thing. I
measure air pressure differential with PC and atmospheric sensors. Log
info every few moments.

I have huge safety margin with my cooling. Lucked out and learned from
others. Didn't allow myself to make any design assumptions.


-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html



On Fri, 10 Mar 2006 14:50:55 -0500 john slade <sladerj@bellsouth.net>
writes:
 

This would be Eric Westland. He did some oil trail tests and ended up
with much improved cooling using vortex generators 1" * 4" vortex
generators at 45 degrees to the airstream ahead of the NACA (or whatever
you want to call the plans Cozy scoop). The results are up on a web site
somewhere.

Based on his results I installed the same generators from day one. I
have no measurements with them not in place.
John Slade




aheaJames wrote:

   

I read an article (don't remember where) about a fellow who placed      

two
   

vortex generator tabs just in front of the NACA ducts.  This      

improved
   

efficiency quite a lot.  He had to experiment a while to get it      

right;
   

but, liked the results.  I think it was on a Velocity or Cozy.

This makes perfect sense.  As I remember when I read the initial      

NACA
   

report.  The paper indicated that the duct was efficient for      

large
   

volume flows which created little back pressure.
Thus, my analysis of the operation is that the  efficiency of the      

duct
   

depends on a bit of local turbulence at the duct to break the      

local
   

boundary layer.   A high flow rate, as the original paper      

indicated
   

and/or required, would do that.  Also a set of vortex generators      

in
   

front of the duct would also do the same.

Second point:  I believe that a reversed direction NACA scoop      

would
   

make an excellent low drag exit port for the cooling air stream.        Such a scoop design would tend to form a small low- drag partial
vacuum at that point, allowing the exit scoop to literally help      

suck
   

the air out.  This would improve cooling efficiency I.E. NACA in,      

and
   

ACAN out.
I hold several patents, but I am not going to pursue this idea on      

that
   

basis.  I think it has a good possibility of being a very      

efficient
   

low drag cooling system.
     
If anyone tries it, please let us know your findings.

Best Regards;

James Freeman



David Staten wrote:

     

I skimmed it.. Chris and I are actually considering armpit scoops        

for
   

cooling, but we still have this nagging urge to minimize        

deviations
   

from plans. I will go back and do more than just skim..

All I saw was NACA's, Cooling and immediately thought of PL..

Dave

Bulent Aliev wrote:

       

You are right Bill. David did not read the whole article. Or he          didn't want to hear it? :)
Buly



On Mar 9, 2006, at 8:58 PM, Bill Dube wrote:

         

I read that article as well. I had the same skepticism about            

the    

NACA intake for cooling. My understanding is that with an NACA            inlet, you don't get the ram pressure you need to force air
through  a high fin-count radiator. Am I wrong about this?

Bill Dube'

David Staten wrote:

           

At the risk of invoking PL's name, anyone else read this              

months    

Sport Aviation mag from EAA, and notice an article on cooling
that  seems to indicate that NACA's are acceptable and              

adequate
   

for  aircraft cooling needs? I have no idea regarding the              

authors    

credentials, and I no longer monitor PL's "newsletter".. I was              curious more than anything else... Pauls reaction, others reactions, etc.

Translation.. yes.. I'm stirring the pot/Trolling... I figure              

if    

we are using NACA's on the Velocity, that makes us somewhat of              

a    

NACA supporter..

Dave

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-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html

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