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  #1  
Old 01-08-2010, 05:20 AM
tinman tinman is offline
 
Join Date: Aug 2005
Posts: 496
Default Conducted My Speed Run Yesterday

I have been waiting for a cold day with calm air so that I could make my full-throttle 8,000' speed run.

I took her up to 8k (Which didn't take very long... ) and steered 120, then 240, then 360 and recorded the max speed on each heading once everything had time to stabilize. Aircraft weight was 1685 with fuel and crew.

The three-run gps average was 180 kts.

I am running a Mattituck 0-360 with 8.5/1 jugs and a Sensenich 72 FM 86" prop.

I ran out of prop on each heading and had to back off of the power a bit, so I could probably go a bit faster with a repitch. Vans recommends an 85" pitch for this plane, but I thought that the 86" would be better for my needs. I am pleased with these results and feel that I have a satisfactory combination of climb and cruise performance.
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  #2  
Old 01-08-2010, 05:41 AM
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pierre smith pierre smith is offline
 
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Location: Louisville, Ga
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Default Not too slouchy, Don...

....and meeting Van's numbers. What would the prop turn if you hadn't backed off?

Congratulations,
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  #3  
Old 01-08-2010, 08:03 AM
tinman tinman is offline
 
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Default

Pierre,
I must admit that I am a coward and didn't push it...once I saw it hit 2740 and still climbing, I backed off. I usually putz along at 120 kts, so it was interesting to see how stiff she got with the additional kts...
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  #4  
Old 01-08-2010, 08:19 AM
Mike Macon Mike Macon is offline
 
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Location: Sisters, OR
Posts: 169
Default Static

What are you turning static?
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  #5  
Old 01-08-2010, 08:28 AM
tinman tinman is offline
 
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Default

21 to 22 static
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  #6  
Old 01-08-2010, 10:02 AM
David-aviator David-aviator is offline
 
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Location: Chesterfield, Missouri
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Default

Quote:
Originally Posted by tinman View Post
21 to 22 static
That's about right. I turn up 2160 static with the Catto and it will top out around 2750 at 8000' but you're speed is a better. The max I've seen is 175 KTAS. The 7A probably has more frontal area.
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  #7  
Old 01-08-2010, 10:07 AM
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hevansrv7a hevansrv7a is offline
 
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Location: Detroit, MI
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Default ditto

Quote:
Originally Posted by David-aviator View Post
That's about right. I turn up 2160 static with the Catto and it will top out around 2750 at 8000' but you're speed is a better. The max I've seen is 175 KTAS. The 7A probably has more frontal area.
Same static, top speed at altitude, NTPS measurement method, same prop-maker, 2650 rpm. I agree about the 8/8A frontal area. I'm told the wing is the same.
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  #8  
Old 01-08-2010, 11:27 AM
Bob Axsom Bob Axsom is offline
 
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Posts: 5,685
Default The average is always the worst case low estimate

If you still have your speeds on each leg, plug them into the NTPS spread provided through links here by Kevin Horton and John Huft. To use this properly you have to have the GPS ground tracks and GPS ground speed as the inputs. This eliminates the effect of wind mathematically and will give you the true airspeed. It will be as high or higher than your average speed calculation.

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  #9  
Old 01-08-2010, 02:43 PM
tinman tinman is offline
 
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Default

Thanks for the tip, Bob. I ran my numbers and gained 2 kts. This is the easiest speed mod that I have ever heard of!
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  #10  
Old 01-08-2010, 04:55 PM
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Exclamation pick it up a bit.......

i did a flat out run a SnF race a few years ago. my race guy said i could go to 2,900 rpms safely. the engine can handle it but the prop tips would go super sonic after that. at sea level i turned 208 mph at 2850 rpms WOT. my 0-360 85' sesi works great on my 6a. good luck.
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