AX-O's Fastback RV-4

[AX-O]

The air molecules and I can

[Bob Kuykendall]

Originally Posted by AX-O

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.

[Stewie]

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

[smokyray]

Originally Posted by Stewie

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

www.iamanet.org

[Stewie]

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.

[AX-O]

Thanks for the info all. Will make some changes and repost.

[AX-O]

Pics of new fairing mold below. I reduced the forward, top and bottom radius.

[learningtofly]

Would you happen to have the coordinates for your new f-407?

[AX-O]

Some more work on the intersection fairings. A few steps closer to the finish product. I am very happy with the fit.

[AX-O]

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.