It's magic
Here is an old VAF link:
http://www.vansairforce.com/community/showthread.php?t=11437 I am 100% skeptical but than no one I know of has really tested it carefully on a RV.
You did not leave a link but assume you are talking about "PROPELLER VORTELATOR KIT". It's been around awhile. I never tried it but their
(LINK) says, two to four mph increase in speed or increase in RPM 20 to 50 for your Homebuilt! Sounds good (too good?). For $24 give it a try. The vortex in theory cause better attached flow or delays onset of turbulent flow, like a VG on a wing. They come into play at higher angles of attack. The only way you will find out is try it. I'm impressed they have a "certified" version. That tells me the FAA signed it off as not affecting the planes function. It doesn't mean it works or not, just that it does no harm. Their STC (
LINK)
Of course VG's for the wing work. On a RV wing they are a Plus & Minus, tend to lower stall a few MPH but take about the same top speed off, that you gained at the bottom. It's the no free lunch rule. I suspect the VG on a prop have Pros & Cons? From the pics they only show it on the first few inches or the prop near the hub. Not sure how much it will do.
Also not sure how long it will last. In the rain the tape will no doubt be chewed off in no time. I'm betting the Con is measuring 2 mph and the tape does not last long. You get three feet. You probably could transfer it to other tape and cut out some more or get the zig zag tape sail plane guys use (about $1.5 /ft). It might be good on the gear legs as well? If (that is an if) it works on a Cessna strut application, than why not.
This is not new, Boeing worked with the "Americas Cup" boat team to develop rib-lets, tape with groves to reduce hull drag in the water. This was in the mid late 80's. The Vortelator kit came out in early 2004 by "Aircraft Development" of Troy Mo. I looked for their web site. All I found was an email:
[email protected]
The tape has to be perfectly placed. If its too far into or past turbulent flow it will do nothing, it's too shallow. Why on the leading edge of the prop? Don't know. I say we need to get yards of the stuff and experiment but not at $8 a foot. Sail plane guys use the stuff. You can buy some zig zag tape here:
http://www.wingsandwheels.com/page29.htm
Here's another link of interest.
http://www.standardcirrus.org/Turbulators.html
Bottom line, you can't violate the laws of physics and the law of "If its too good to be true....." The Reno racers do some kind of sanding cross hatching on the surface of their props to improve performance. There are things to do, free thing. One freebie is make sure your prop is super clean (no bugs) waxed and smooth, especially the leading edge. Nicks and gouges are bad aerodynamically on the leading edge or any surface. When I say smooth I mean mirror, except for the "cross hatch" sanding some do for racing. I can't advise you on cross hatch sanding, but I am not going to sand on my $5000 prop, even for racing. May be someone else can give details on race prop of a metal prop.
