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  #251  
Old 07-18-2013, 08:13 PM
AX-O's Avatar
AX-O AX-O is offline
 
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The air molecules and I can
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RV-4 fastback thread and Pics
Instagram @ LetMeFlyIt
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The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of Van's Aircraft.
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  #252  
Old 07-18-2013, 08:55 PM
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Bob Kuykendall Bob Kuykendall is offline
 
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Location: Vallecito, CA
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Quote:
Originally Posted by AX-O View Post
The air molecules and I can
"The air has fingers, not eyes."

You might be surprised how asymetrical some aircraft actually are when you look closely. I've measured Nationals-winning sailplanes with templates that show that the right and left wings look like their airfoils came from two completely different gliders. Yet they go like stink and fly straight as arrows.

Thanks, Bob K.
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  #253  
Old 07-19-2013, 08:26 AM
Stewie Stewie is offline
 
Join Date: Nov 2008
Location: Santa Paula CA
Posts: 185
Default Flow viz

Axel-

Good timing on this subject. I am finishing up my Phase I and just put my pants and gear fairings on a couple days ago. Per the manual, I aligned the fairings by string method, no weight on gear. Nevertheless, during flight I was definitely getting some roll/yaw forces (although this could have been due also to pant misalignment).

I waited to do the top/bottom intersection fairings, since I figured doing so would preclude me from adjusting the gear fairings based on flight tests. I'm glad I did so. After the first flight with fairings, I decided to do a flow viz experiment. I smeared engine oil along the leading edge of both fairings, then doped it with talcum powder, and went out and flew at cruise speed for an hour. When I returned, I had a very nice visual flow pattern that showed both fairings to be misaligned. Adjusted the fairings (TLAR method), redid the flow viz, and now the flow is straight and roll/yaw forces much reduced (there's not much I can do about wheel pant alignment at this point). I'm hoping the addition of the intersection fairings doesn't mess things back up again!

I'll post pics and a more detailed explanation on a dedicated thread in a couple of weeks when I have a bit more time. In any event, you may want to consider waiting to do the intersection fairings until once you've had a chance to fly the plane.

Eric
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  #254  
Old 07-19-2013, 08:41 AM
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smokyray smokyray is offline
 
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Location: TX32
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Default Ah, the details...

Quote:
Originally Posted by Stewie View Post
Axel-

Good timing on this subject. I am finishing up my Phase I and just put my pants and gear fairings on a couple days ago. Per the manual, I aligned the fairings by string method, no weight on gear. Nevertheless, during flight I was definitely getting some roll/yaw forces (although this could have been due also to pant misalignment).

I waited to do the top/bottom intersection fairings, since I figured doing so would preclude me from adjusting the gear fairings based on flight tests. I'm glad I did so. After the first flight with fairings, I decided to do a flow viz experiment. I smeared engine oil along the leading edge of both fairings, then doped it with talcum powder, and went out and flew at cruise speed for an hour. When I returned, I had a very nice visual flow pattern that showed both fairings to be misaligned. Adjusted the fairings (TLAR method), redid the flow viz, and now the flow is straight and roll/yaw forces much reduced (there's not much I can do about wheel pant alignment at this point). I'm hoping the addition of the intersection fairings doesn't mess things back up again!

I'll post pics and a more detailed explanation on a dedicated thread in a couple of weeks when I have a bit more time. In any event, you may want to consider waiting to do the intersection fairings until once you've had a chance to fly the plane.

Eric
Excellent subject. I will add however that over time less importance will be spent toward alignment and appearance and more on how to keep them attached and in one piece.

I found in 2000 flying hours on my RV4 and HR2 "life stresses" on them challenged structural integrity (especially on rough turf or gravel) or just the landing gear movement itself. My point? Leave some wiggle room around the base of the fairing (where the leg fairing attaches) and put some MhWh tape around them where movement occurs. Use large area washers on all holes and thread lock as the screws loosen easily. Put Silicon film on the back side of the fairing where it chafes any painted surface.

Even with all of the above they take a beating. Be ready with HySol...

V/R
Smokey

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  #255  
Old 07-19-2013, 11:53 AM
Stewie Stewie is offline
 
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Location: Santa Paula CA
Posts: 185
Default Great idea!

Great idea Smokey! I'm about to make my intersection fairings, I like the idea of laying up over a relief and leaving a bit of wiggle room, then using tape to fill the gap/seal the gap.
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  #256  
Old 07-19-2013, 12:41 PM
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Thanks for the info all. Will make some changes and repost.
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RV-4 fastback thread and Pics
Instagram @ LetMeFlyIt
VAF 2022 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of Van's Aircraft.

Last edited by AX-O : 07-24-2013 at 01:20 PM.
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  #257  
Old 07-19-2013, 03:00 PM
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AX-O AX-O is offline
 
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Pics of new fairing mold below. I reduced the forward, top and bottom radius.





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Axel
RV-4 fastback thread and Pics
Instagram @ LetMeFlyIt
VAF 2022 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of Van's Aircraft.

Last edited by AX-O : 07-24-2013 at 01:21 PM. Reason: Added links
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  #258  
Old 08-01-2013, 06:23 PM
learningtofly learningtofly is offline
 
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Location: kuttawa, ky
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Default Bulkhead

Would you happen to have the coordinates for your new f-407?
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  #259  
Old 08-10-2013, 02:43 PM
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Some more work on the intersection fairings. A few steps closer to the finish product. I am very happy with the fit.



















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Axel
RV-4 fastback thread and Pics
Instagram @ LetMeFlyIt
VAF 2022 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of Van's Aircraft.
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  #260  
Old 08-10-2013, 02:56 PM
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AX-O AX-O is offline
 
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I took the airplane out early this morning because I wanted to see how it looked. I only used one AN-3 bolt on the top of the rudder. That is why the seam looks a little weird. I think she is starting to look nice. Hope I can have her in a hangar in a couple of months.











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Axel
RV-4 fastback thread and Pics
Instagram @ LetMeFlyIt
VAF 2022 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of Van's Aircraft.
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