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  #1  
Old 11-02-2011, 08:17 PM
KiloWhiskey1's Avatar
KiloWhiskey1 KiloWhiskey1 is offline
 
Join Date: Mar 2006
Location: Kennesaw, GA
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Default Static port - pain in the rear!

I have an RV-7 and I am having issues with my airspeed indicating about 5-10knots high. I just had an IFR certification done and the pitot and static system checked out fine. I have heard that some static ports can cause a low pressure area around the port that causes inaccurate readings.

This picture is of my static ports with a half washer glued just in front of the port hole. I had heard that this would disrupt the air and allow for a more accurate reading. I flew it and did not see a difference.

Please let me know what ports are working well for you.

If someone is using the same ports that I have, did you mount them differently?

Any other advice would be much appreciated.

[IMG][/IMG]
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  #2  
Old 11-02-2011, 08:23 PM
leaker311 leaker311 is offline
 
Join Date: Aug 2009
Location: texas
Posts: 68
Default Van knows what he is doing

Standard Super duper Van's Static system aka prosealed pop rivet.
Dynon D180, smackdaddy on speed.

I have noticed with Van's (barring one maybe two exceptions) fancier is not always better, just more expensive
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  #3  
Old 11-02-2011, 08:30 PM
aerhed aerhed is offline
 
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Default

Usually placing a dam/riser in front of the port will lower the pressure across the port (think flute). This RAISES indicated speed. If you are indicating high you already have low static or bad gaging.
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  #4  
Old 11-02-2011, 08:44 PM
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Ironflight Ironflight is offline
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Default

Do a search for "Static" Keith - you'll find lots of experiences and things folks have tried - some work, some don't.

It seems to be a common misconception among many folks that the pitot/static test can ensure a goo static source - it doesn't! What it DOES do is tell you that your static system doesn't leak - because the accuracy of the ports are dependent on the aerodynamics of the airframe at speed, the only way to test that is in the air. It can take hundreds of hours for a manufacturer to find a good location and configuration for static ports - that's why I just stick with Van's solution - saves me a lot of Avgas!

Paul
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  #5  
Old 11-02-2011, 08:46 PM
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Location: Bennington, Vermont USA
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Default Leaks?

Are you absolutely sure that you don't have any pitot static system leaks?

I use the basic pop rivet static ports and corrected initial airspeed errors by fixing leaking pipe fittings.

Jim Sharkey
RV-6
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  #6  
Old 11-02-2011, 08:46 PM
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Sparky Sparky is offline
 
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Location: Perham, MN
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Normally, the best static port is a very small hole in the skin on both sides (to equalize differences in pressure due to side slips) of the aircraft in an area of the fuselage where there is very little normal disruption of airflow. From past posts on VAF it appears that the use of the Van's specified pop rivet in the specified fuselage position(s) works as advertised and even a slight deviation may cause problems. It appears from your picture that you have installed static port(s) that cause severe disruption of airflow past the static port(s). The main problem appears to be the protrusion of the ports from the fuselage skin. I think they were intended to be installed inside the fuselage skin.
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  #7  
Old 11-02-2011, 09:10 PM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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Default

Quote:
Originally Posted by leaker311 View Post
Standard Super duper Van's Static system aka prosealed pop rivet.
Dynon D180, smackdaddy on speed.

I have noticed with Van's (barring one maybe two exceptions) fancier is not always better, just more expensive
I agree, after a number of test with different size "dam" and other shapes, I found the size and shape of a pop rivet head gave me the best result. I less concern about IAS then altitude, specially for IFR so I believe I have mine that the altitude shows very close and IAS has narrowed to about 1-2 knots accuracy.
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  #8  
Old 11-02-2011, 09:15 PM
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Larco Larco is offline
 
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Maybe only a pain because maybe the plans were not followed? This is not really directed towards you but a message to builders not yet to that point of building. It seems like most everyone that doesn't use the standard static ports from Vans has a problem. Location and SHAPE are important. After market ports seem to cause about a 10 MPH error. Larry
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  #9  
Old 11-02-2011, 10:16 PM
petersb petersb is offline
 
Join Date: Mar 2008
Location: Toronto
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I drilled a small hole down the centre of a #8 stainless machine screw, same as that used to screw the floor down on the RV7. Then grind the head flat on your scotch bright wheel until the head is about the thickness of a rivet head. You can now use a nut to hold the #8 screw firmly into the fuselage, the thread diameter is perfect size for a quarter inch plastic tube. Works perfectly

peter
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  #10  
Old 11-02-2011, 10:21 PM
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KiloWhiskey1 KiloWhiskey1 is offline
 
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Default Thanks

Thanks for all the replies. I went back via the search engine and found some additional info and I have some good ideas to try from there as well. I tried the pop-rivets from Vans first and switched to the ones pictured in my original post after leaks became an issue. I chose these because of their outside mounting configuration. They are similar to many certified ports found on Cessnas and Beachcrafts. Ultimately they didn't work well either.

Cleveland Tools has inside mounted ports for $24/pr that look like they would fit the holes that will be left by the current ports. Does anyone have the Cleveland ports installed in their RV-7. If so, how and where did you install them? Are they working well?

Thanks.

Keith
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