New Wheel Fairings

[Bob Axsom]

The wing tips I made this year improved the performance of my RV-6A in a couple of ways - speed increased 3 kts at 6,000 ft density altitude and it is rock solid in flight. The first was expected but the second was a surprise. When I came back from the EAA Chapter 732 meeting Sunday I greased it on and made the first taxiway turnoff - no float, balloon or bouncing around in light chop. Every time I go out in the garage I look at the molds and have a lot of satisfaction. Now the cross country air race season is over and I look ahead to next year wondering what I can do to gain a little more speed without putting out a lot of money.

The thing that I think has potential and will give me a lot of satisfaction is making new wheel fairings. These will be intended for racing. I'm not buying the fat bulbous shape as unquestionably the very best that can be done. I think they should have a round ended leading edge that does not change there effect on drag with changes in AOA or yaw. They have to be large enought to enclose the brakes and tires except for the bottom inch of the tires with an inch of internal clearance at the tightest fit points. There should be a concave surface of uniform depression on all sides on all sides after the wheels extending to a blended return to the slipstream at the trailing edge. Finally, there should be a rubber seal between the fairings and the tires.

Even if the effort is a failure I will end up with some fine looking molds that I can mount for display like the tip molds.

OK critics, hit me with your wisdom.

Bob Axsom

[hevansrv7a]

Bob, I admire your work. I have only this to contribute and it's not really mine and you probably already know it, but here goes.

The SJ wheel fairings on the mains are the minimum width, much narrower than Van's. Sam acheives this by making the outboard side attach with an AN4 bolt directly to the axle nut and just covering the brakes on the inboard side. This leads to having the tire offset within the housing, closer on the outboard side. His fairings are also, I think, a little longer than Van's. I have no test data on them but Sam claims they contribute a few knots over the stock version to which he attaches the name of a popular country/western singer famous for her looks as well as her singing.

I think if one were to custom-make an axle nut another inch could be slimmed off.

The mounting of the fairing to the leg is different. It's an elegant one-piece affair on the inboard side. Sam or I could supply more about that.

Have you settled on having an open area behind the wheel rather than a bulkhead? That's really important information if you have found that it works. Sam James recommended a close fitting bicycle fender style which he said was used a lot in racing. I have no stake in this one, just an intense interest.

Thanks again.