Racing with Voodoo

This season, I’m racing with Voodoo. What? Oh. No. Sorry. Not the famous Reno Racing plane by the same name. I’m talking about a speed modification that uses some aerodynamic Voodoo to improve Tess’s performance in our never-ending quest to crack the mac barrier in an Ercoupe. Or at least just go fast enough to securely maintain our title of the World’s Fastest Ercoupe, and to keep those pesky Cesena 150s and 152s behind our twin tails in the SARL races.

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So this might be our sketchiest speed mod yet, but here’s the tale: One of the bad things about having your plane in the shop is that you spend too much time sitting at home thinking about airplanes, instead of being out at the airport having fun with them. And thinking about airplanes at home often entails surfing through various online catalogs of airplane stuff, and discovering things that you were perfectly happy not owning when you didn’t know they existed, but now can’t live without.

This is why I now have Wig-Wag lights on Tess. But they’re not the only thing we added while waiting for our nose strut to be rebuilt, and then waiting for UPS to locate said strut after they lost it.

I also added Voodoo Propeller Tape to Tessie’s prop. Well, that’s what I call it, anyway. It’s officially called a Propeller Vortelator. It’s a distant cousin of the aerodynamically unlikely vortex generator, which is a small plastic or metal fin which, when glued to your wing along with a bunch of other little fins, does amazing things. Things like lower your stall speed, improve controllability, reduce your takeoff run, and more. How on earth do they do that?

Well, that’s what I was told, anyway. Apparently, the little fins create mini vortexes of air that delay flow separation in the boundary layer, and…

Yeah, like I said, magic.

So when I read about something similar for propellers, it didn’t strike me as impossible. Hey, if a bunch of fins on a wing can work magic on the airflow and improve performance, why wouldn’t something similar work on the prop? A prop is just a perpendicular spinning wing, after all. The advertising copy for the Vortelator—which is made by Aircraft Development, the same folks that make the Slick Air coating that we use to reduce airframe drag—say that, “Vortelators will cause the boundary layer to stay attached to the propeller surface for a greater distance, and to keep the boundary layer thinner. The net result of these two actions is that it reduces both the profile drag and skin friction drag components of the parasite drag.” Going on, they said that the Vortelators are placed on the most inefficient high drag areas of the prop, making it more efficient across its span. As I didn’t understand what they were saying, that didn’t impress me much.

But they also said it would improve my speed by 2 to 4 mph. ThatI understood.

I placed an order.

Now, I knew the Vortelator was some sort of tape, but I couldn’t tell much about its form factor from the pictures at Aircraft Spruce’s website. I think I pictured a row of mini vortex generators, or a quasi-washboard ribbon. I’m sure you can picture my disappointment when my box of Voodoo Propeller Tape arrived, and I discovered that it was nothing more than a piece of flat, thin, clear self-sticky plastic tape—cut in a zig-zag pattern.

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Seriously? I was about to send it back in disgust, but decided to do some more research first. The first thing I found was that I couldn’t find anyone who had actually used it. Rather, all I could find were people who hadn’t used it, but nevertheless felt justified in trashing the mere idea. They’re probably the same people who poo-pooed vortex generators when they were first introduced, then later quietly installed them on their planes.

Next, I discovered something called turbulator tape, which is a big deal with the sailplane crowd. Apparently, most current production sailplanes use it to improve aerodynamics, and many older ones are retrofitted. Guess what? Yeah. It’s nothing more than a piece of flat, thin, clear self-sticky plastic tape—cut in a zig-zag pattern.

Hmmm… Those sailplane folks sure know their aerodynamics, even if they don’t have propellers.

But there’s more: The RC model crowd rave about zig-zag tape. Granted, their planes don’t have pilots in them, but they are honestly and truly miniature aircraft. And zig-zag tape is even used in archery to improve airflow of the tail “feathers” of modern carbon fiber arrows for increased accuracy. Who knew?

And although Voodoo Propeller Tape sure looks disappointing to the naked eye, in all things aerodynamic, small changes can net big results. So maybe some thin zig-zag sailplane/model plane/archery tape near the hub of Tess’s prop might make that ol’ piece of aluminum work better.

What the heck, it didn’t cost that much, it’s already paid for, it’s STC’d for my prop (which only means the government thinks that the product is safe, not that it actually works), and my wrench turners don’t want much to install it. And who knows? Maybe it will make Tess shoot through the air like an arrow. Rather than sending it back, I had my team put it on the prop.

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So this season, we’re racing with Voodoo.

 

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