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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
>>>>>
>>>>> -- >>>>> Homepage: http://www.flyrotary.com/
>>>>> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
>>>>>
>>>>
>>>> -- >>>> Homepage: http://www.flyrotary.com/
>>>> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
>>>
>>>
>>>
>>>
>>>
>>> -- >>> Homepage: http://www.flyrotary.com/
>>> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
>>>
>>
>>
>> -- >> Homepage: http://www.flyrotary.com/
>> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
>>
>> .
>>
>
>
> -- > Homepage: http://www.flyrotary.com/
> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
>
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
-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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