Dimple Tape

Is your friend Bill Rewey by any chance? He has an article on this in the latest Brodhead Pietenpol Association newsletter.   I had never heard of this stuff and now see two references in a day.   Bill's had it on his Pietenpol prop for 10 years and claims a static RPM increase of 75, and 10% increase in fuel burn.  He has just installed it on a Zenith CH801 prop and reckons he's seeing 5% improvement.

He also references an article in EAA Sport Aviation from January 1998 - linked here:

http://www.oshkosh365.org/saarchive/eaa_articles/1998_01_11.pdf

I think this is written by the guy that sells the tape, but it does look like an interesting product.  In addition to aerodynamic and speed improvements the article claims a 50% reduction in propeller noise. 

I'm tempted... anyone else have experience with this?

Dimple tape pops up in conversation every now and then, but there really isn't any absolute scientific evidence that it does in fact do anything.  Sorta like drooped wing tips!  (The only thing we know for certain that drooped wing tips do is cut down the visibility on a high wing airplane or reduce the wing tip ground clearance on a low wing!)  The fact that, after all this time we still don't see dimple tape showing up on large numbers of aircraft, and don't see it offered by ANY of the major propeller manufacturers tells me that it's mostly hype.

Now Marvel Mystery Oil is a whole different issue.....

Cheers!

Joe

Hey Paul,

Just confirming Adam's comments.  In fact, Bill has sent us a note that we'll be running in the Members' Forum section of August Sport Aviation discussing his successes with dimple tape. You can learn more at www.DimpleTape.com

I've had several members over the years talk about improvements using dimple tape.  

Good luck with your investigation.

Mary Jones

Mary, maybe you could invite members to come on here and discuss their Dimple Tape experiences.   We will have invited the great mass of EAA  members to join the community by the time their August edition reaches people.

On a related issue I have developed a theory that my Cessna 180 is uncommonly quick (this is true) because it has hail damage on the upper surface of the wing - thus dimpling it. 

I just read in Popular Science magazine about a vinyl graphics company that's started doing full-body dimple tape for cars:

http://gizmodo.com/5133921/fastskinz-car-wraps-confuse-passing-golfers-as-they-save-you-gas

(Note to Adam: no, that's not my car. Signed, Postman Pat.)

a product that will undoubtedly be hawked by Billy Mays in the near future.  

This is the magazine that also promised me I'd be flying to work in a jetpack by now...

Sorry, Billy Mays died The last week of June, 2009.

I bet if Vince the Sham Wow guy hawked it, it would show up at Walmart checkouts everywhere over night.

Dear Paul, several years ago i experimented the Dimple Tape on my propeller fitted on a KR 2.

Propeller was a 52x 48 Ed Sterba designed for a VW conversion 1835 cc -70 HP.

I was wery satisfied of the experiment:an increase of 50/100 RPM at the same power, and a little bit of speed, about 10 mph.

Plus a little reduction of noise.

Now i have upgrade my engine to 2180 cc and a little more HP, requiring a different propeller that i'm building: i will addedd again the Dimple Tape.

On Sport Aviation of August i have hear that will be an article about the Tape.

Best regards

Franco Bucci

 I can personally vouch for Marvel Mystery Oil.  I used some last night to pop up some popcorn, and it was delicious. 

Look at a golf ball.  I do know that the performance of the ball is strongly influenced by the dimples on the surface of the ball.  Can't remember more than that.  Maybe someone else has more info, as there has been a lot of analysis published on the golf balls.

Mike

On golf ball dimples:

http://wings.avkids.com/Book/Sports/instructor/golf-01.html

Several years ago I met the guy who invented the dimple tape at Lakefront Airport in New Orleans (NEW) and we had quite a conversation.  He showed me models of propellers on scales and ran them up with and without the dimple tape.  The results looked impressive.  Since I am (was) an avid cross country racer, I thought it would be worth a try on my 64 Comanche 400.  I can't remember his name but it was something like Ochipinnili???  Anyway, he directed where and how to install the dimple tape on the prop and on the wings.  I spent the whole weekend testing this dimple tape for him; from morning to night, trying to find the "sweet" spot for best performance.  Here are the results:  When I installed the tape on my constant speed Hartzell in the location suggested, my climb rate went from 1800 fpm to 500 fpm!  Yes, it just about stalled the prop.  I moved the tape back a few times on the blade and foward a few times on the blade and the results were the same.  With the tape removed, I got my 1800 fpm climb back.  Maybe it works better on a fixed pitch prop.  I had better luck on the wings.  With the dimple tape installed at the suggested spot my stall speed went from 68-72 mph to 62 mph.  I did not gain any top speed at low altitudes or higher altitudes (15K and above).  I again moved the tape forward several times and back several times on the wing in an attempt to find the "sweet" spot but the first suggested location was the best.  For my application, if it didn't increase my top speed any, I didn't want it on the airplane.  I can say that it did greatly help low speed handling, especially in the landing configuration.  I was disappointed in the prop results but I do have a constant speed prop and I have heard that a fixed prop realizes some improvement.

Charlie

Sounds like a good project for EAA or CAFE.   There are several articles and sites discussing dimple tape and the "Turbolator"  tape that gliders have tried.   It is curious that nothing definitive has been done.  I'd like to know if I can get free mph,  stall speed, mpg.

I can't even spell enigener but from what I have read, dimple tape and vortex generators do the same thing, They increase the turbulent boundary layer which can fill in areas of a less than ideal airfoil. G.A. AIRFOILS ,Harry Riblett. In his book he shows the benefit - need of VGs on less than ideal airfoils and how to improve airfoils. Assuming you can change your airfoil.

The golf ball is less then an ideal airfoil and needs the dimples. A well designed airfoil for a specific purpose should not need them.

Any disturbance to the boundary layer increases drag, but if this disturbance is approximately 20% or greater from the leading edge the amount of drag is significantly reduced. THEORY OF WING SECTIONS, Abbott and Doenhoff.

Maybe if your wing - prop airfoil is somewhere between a golf ball and a well designed section they should be an advantage.

As for wing tips, drooped or upright they should not be needed if the wing platform was well design for a specific purpose. I got this from a seminar by "Raymer" at Oshkosh this year. He also has a book on design.

So if you had a good airfoil for the purpose no "improvements" should be needed. Not much help huh.

As for Marvel Mystery Oil on the farm we found trans fluid did about the same thing.