REFLECTOR: Performance

[Rene Dugas]

Brian, I did oil studies to show air disturbance from IO-540 down exhaust exiting about three inches.  The air disturbance for each side was about 14 inches in diameter. I've never gotten around to building tear drop fairing but I'm certain they would help.  Exit out the back would be even better or through the prop like my outboard motor.  I know I got carried away.☺

Sent from Rene's iPad. A pleasure.  Go Apple.


On May 9, 2013, at 11:23 AM, Brian Michalk <michalk at awpi.com> wrote:

> I still don't understand the drag mechanism for normal angle of exhaust being a drag.
> Does anyone know where I can find NACA or other research on this?
> 
> On 5/9/2013 11:07 AM, Richard J. Gentil wrote:
>> Geoff,
>> 
>> If you make the exhaust change I would be very interested in your results since mine currently exit straight down.
>> 
>> Richard
>> 
>> Sent from my iPhone 5
>> 
>> On May 8, 2013, at 10:59 PM, Geoff Gerhardt <geoff.gerhardt at gmail.com> wrote:
>> 
>>> Scott,
>>> 
>>> Thanks - that was the insight I was looking for and what I suspected.  I would actually prefer to have the normal, shorter wing - I'd love the 15kts in speed and would gladly live with a little higher stall speed.
>>> 
>>> Now, given that, I wonder if there's anything I could do that could improve my performance.  The two things that I'm considering are changing my exhaust config from exiting straight down to exiting inside the cowling at the prop.  I've heard some folks state they have seen significant improvements with that mod.  The other was an intake ram scoop - would that give me more MAP at altitude and a little more power?
>>> 
>>> Thanks for all the performance comments/comparisons...keep them coming.
>>> 
>>> Geoff
>>> 
>>> On Wed, May 8, 2013 at 8:31 PM, Scott Baker <scottb33333 at gmail.com> wrote:
>>>> I notice that several responders are giving numbers for a Velocity Standard RG, while Geoff's aircraft is a Velocity 173 (aka LW 'Long Wing').
>>>> Velocity Standard models, with their smaller wings and reduced drag, are faster than their 173 brethren ... by 15 knots on average (with comparable engines and propellers).
>>>> The factory V173FG trainer is hard pressed to see 145KTAS in cruise.  I think the RG version cruises between 155-160KTAS (about 15knots faster than the fixed gear model).
>>>> These numbers are pretty close to what Geoff is reporting for his aircraft.
>>>> Scott B.
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On 5/8/2013 10:38 AM, Geoff Gerhardt wrote:
>>>>> Folks,
>>>>> 
>>>>> I'm getting pretty consistent performance out of my 173RG over the last 8-9 months since                           initial flight testing.  My question to you guys is, are the performance numbers I'm seeing typical, or should I be seeing better performance?  Normally, on a cross country, I'll fly b/w ~8-12,000', ~60deg LOP which typically has me going 150kias at 8-8.5gph.  Full power, 160kias is about my max speed.  
>>>>> 
>>>>> I have a fixed-pitch Catto prop (66x74, design target 200mph @ 2800RPM).  When I'm doing 160kts, my prop is spinning at ~2800RPM.  That tells me that I have the power to spin the prop, but may have air frame drag that's keeping me from seeing the 200mph predicted by Catto at 2800RPM.
>>>>> 
>>>>> I have a standard 200hp, Lyc IO-360, Lightspeed EI on one side, Mag on the other.  Timing as per spec for both EI and Mag.  About 90hrs on the engine (rebuilt).  Compression/oil consumption is normal.  Very stable performance from the engine.
>>>>> 
>>>>> My plane is fully finished and pretty tight.  Main/nose gear doors are not hanging out and are reasonably well tucked in when the gear is raised.  Main wing angles of incidence are spot on, no rudder trimming was necessary to center the ball - she flies nice and straight.
>>>>> 
>>>>> The factory predicts I should be able to cruise at 175kias - that's just not possible with my current setup.  Can others with Std Velocities relate the performance you are seeing?  Is this as good as it gets, or does anyone have suggestions for things to check to see if I can eek out a bit more speed?
>>>>> 
>>>>> Thanks.
>>>>> 
>>>>> Geoff
>>>>> 
>>>>> 
>>>>> 
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