REFLECTOR: Performance

Fri May 10 10:47:54 CDT 2013

I would say we need someone (Geoff, Geoff) who only changes the exhaust and nothing else, runs a test and reports back to the Reflector with the findings

Richard 

Sent from my iPhone 5

On May 10, 2013, at 11:38 AM, Kevin Baker <flykb at verizon.net> wrote:

> I would agree.
> This is the type of info I've read about as well on the cozy /long forums with similar results 
> 
> Thanks
> Kevin Baker
> 
> .
> 
> On May 10, 2013, at 10:12 AM, David Rene Dugas <renedugas at gmail.com> wrote:
> 
>> David,
>> I would suggest that #2 is significant because the large plume of hot exhaust is forcing a dramatic change in direction on a large shout of air traveling at 200 mph. This would act like a speed break.   The energy to move this air would be parasitic drag and would be substantial.   I realize there is no mechanical connection but there is a gaseous connection the same as one has with the earth when in flight so very real. I'm not an engineer so I do not has the formulas to calculate it but my 2 cents worth is that that plume and pipes are a big source of drag. Just my maniacal machinations. 😳
>> 
>> Rene' Dugas
>> Sent from an Apple. 
>> 
>> On May 10, 2013, at 8:06 AM, "David Ullman" <ullman at robustdecisions.com> wrote:
>> 
>>> IF I added up all the speed increases I could get from the topics discussed
>>> here, my plane would be supersonic.  
>>> 
>>> I too would like to see proof that rear facing exhaust helps.  I have now
>>> heard four theories: 1) the exhaust gas acts like a jet, 2) the
>>> perpendicular flow adds drag, 3) The exhaust disturbs the boundary layer on
>>> the cowl, 4) the exhaust gas disturbs the flow seen by the prop.  
>>> 
>>> The first one I calculated, and the thrust due to increased velocity of the
>>> exhaust gas is minimal.  For #2, the plum has no way to transfer its drag
>>> back to the plane.  Picture the plume as a cylinder projecting into the
>>> airstream.  It is not connected to the plane in any way to slow it down, so
>>> #2 is out.  The boundary layer at the back of the plane is already well
>>> chewed, so #3 is not much of a possibility.  I hadn't thought of disturbing
>>> the prop flow before.  The wings are already doing a good job of this, could
>>> the exhaust add to this disturbance in a significant manner?   I can see
>>> where moving the exhaust to the hub area (or outside the prop radius) may
>>> have an effect, the first three are just noise.  
>>> 
>>> David Ullman
>>> N444DX
>>> President EAA 292
>>> 541-760-2338
>>> david at davidullman.com
>>> 
>>> 
>>> -----Original Message-----
>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>>> Behalf Of reflector-request at tvbf.org
>>> Sent: Thursday, May 09, 2013 7:47 PM
>>> To: reflector at tvbf.org
>>> Subject: Reflector Digest, Vol 98, Issue 27
>>> 
>>> Send Reflector mailing list submissions to
>>>  refle
> 
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