Strut speed fairings.

[Av8r3400]

Just to set the record straight, the strut in my previous post is not mine. It is a photo of a Kitfox SLSA parked in their booth at Airventure.

Below is a top and bottom view of my struts.

This is from the top:
Mangy Strut.jpg


This is from below. (Please ignore the mud...)
Mangy Strut 2.jpg


I filled in the trailing edge gap again with a fitted piece of wood, hysol'ed into place then covered the whole thing with fabric. I went with the fabric because I have never had any luck getting paint to stick to plastic like this. So now they are fabric covered and match the rest of the plane.

[SkySteve]

(Please ignore the mud...)

AV8r3400,
No, we will not ignore the mud. Mud is definitely a badge of accomplishment!! Mud on, dude.

[jabkwab]

Today I made a test flight with my new strut fairings fashioned from insulation foam and Oratex (the rc plane stuff). Picking up about 9 miles of cruise, impressive!

One thing i noticed is the orientation of the fairings. I made them so that they can rotate, the theory being that they will align in the most aerodynamic way possible during flight.
What surprised me is how far down they seem to go during flight!



On the ground the fairings align perfectly with the small connecting tubes between the struts.

Would this make my Kitfox weird? Or is this the way everybody is aligning their fairings, just nobody told me


Greetings from the Low Countries, Jan

[kitfox2009]

Try doing the jury and elevator struts as well. Probably gain some more.
I think that's why the Vixens fly faster.
Have fun
Don

[jiott]

That's really interesting! I wonder if the rest of us who have our fairings in a fixed position could gain some more speed by angling them down. From the photo it looks so extreme, I wouldn't have believed it. Does both sides of the airplane do the same? Wonder if it is a spiraling propwash effect?

[av8rps]

I'd be careful about having the wing struts move too easily, as like any flying surface that is not dampened some way or other could allow flutter.

I have my horiz stab struts faired and I one day switched them out with a standard (un faired - just round tube) set of struts to learn streamlined horizontal struts give me 2 to 3 mph. Next mission is to fair out my jury struts. I have some faired from a Speedster, but I think they are not wide enough in chord, so I'll probably make up my own fairings on those. I'm guessing those will be another couple mph.

It all adds up!

[SkySteve]

Does anyone have an idea what size the fairings should be and what material they should/could be made of for jury and stabilizer struts?

[av8rps]

General rule is the chord of the fairing should be aporoximately 4.25 times the thickness of the tube you want streamlined.

While Kitfoxes plastic snap on wing struts are a bit heavier than I'd like, they are sized just a bit over 4 inches (as I recall) and the struts on the 4-1200 are 1 inch in diameter, so they are about perfect. I believe thats why you see 9 to 12 mph cruise speed increases on average when they are used.

Unfortunately most readily available (and expensive) streamlined 4130 tubing has much too narrow of a chord to be truly effective, so for jury and tail struts I would just make my own. I believe my tail struts are about 1.75 inches in chord. They were some leftover material my Rans buddy had, so I just used that.

[Floog]

Just curious. Has anyone done a retractable gear conversion on a KF? It would be nice to get those 29" wheels in the wells after I streamline my jury struts

[HighWing]

I did fairings on the Jury Struts and the Elevator Struts. The ratio I used was 1:3.5 which is very close to the ratio on the extruded lift strut fairings. I prepared an album series of pictures with the technique I followed. As a side note, during the Lancair build there was talk of the drag created when a right angle is produced by large surfaces. Specifically the horizontal wing butting against the vertical fuselage. On high performance airplanes, these are always faired. I would suspect that the junction between the doors and lower wing surface on our design is extremely draggy. Fix that, and I suspect performance would improve about as much as adding the lift strut fairings. To see the way I did my strut fairings, go to my Albums "Techniques Page" http://www.teamkitfox.com/Forums/album.php?albumid=474