Curiosity got the best of me on this one. I had to see if it really worked. I ordered 180 bucks worth of dimple tape and put it on this afternoon. To give some idea of a comparison, before I installed the tape I flew the plane at WOT at 3000' . The engine reached 2730 RPM and the indicated airspeed was 130 mph. I have a fixed pitch Sensenich, 180hp and did not use the neg. flap cruise position. Flaps set at zero. After installation on the wings only I repeated the same flight. WOT at 3000' the engine reached 2770 RPM and the indicated airspeed was 138 mph. A gain of 40 RPM and 8 mph airspeed.
My goal was to decrease drag enough to reduce sink rate and allow a lower touchdown speed without maintaining power through the flare. Maule pilots will relate to this as well as owners of any aircraft using a high lift wing that is accompanied by high drag. I will experiment more with the landings this week when another set of eyes can watch the airspeed at touchdown.

Hey dirtstrip,

Just wondering if you did anymore testing? Where did you apply the tape?
Got any pictures?

Chris

I'd also like to know where on the airplane you want to put this tape. I've heard of it being used on propeller blades, I've personally used it on the underside of laminar airfoil wings, and I've heard of using it to control boundary layer airflow around "diverging" surfaces. I'd be curious to know how and where the stuff is used on a back country airplane.

Maybe on the struts and gear?

Hey thanks for the heads up, I did not say in my post where I put the dimple tape. I spoke with the designer and he said the most effective use is along a line wing tip to wing tip over the deepest part of the wing chord. It would work similar to VG's by affecting the boundary layer but would do so with less drag as it does not stick up in the airflow. That is where I placed mine and since the chord of my wing is maintained over the cabin area I put it there too. Other proven locations are on the prop and struts. He said the prop location would not interfere with the leading edge tape that I have in place as it would also be along the thickest part of the prop. He claims a noise reduction of 30-50% by reducing the amount of air that breaks loose behind the passing blade causing the "pop" sound. This supposedly increases prop efficiency of about 5%. On the struts it should also be placed along the line over the deepest chord of the strut. In the case of a symetrical strut where both upper and lower halves are like shaped then both upper and lower get the tape. It is most effective in the area hit by the prop blast since the airspeeds and corresponding drag there are much higher. We did not talk about the landing gear but he did mention it has been used on the fuselage and rear control surfaces. In general he seemed to point out placement at the thickest part of the wing, strut, and prop. Slimmer props benefit less. Maybe that translates to the flatter your rear control surfaces the less benefit.
I apologize for not having more results to share. I noticed it was time to do the annual condition inspection and I also have some changes in mind while I do it. Things are apart now, and last night we got frost which will speed up the coming harvest. My hope for the dimple tape is to reduce enough drag to cause a reduction in sink rate as airspeed decays during flare with low or no power at landing. This should reduce the touchdown speed in an engine out landing.

Sounds intriguing.

Love to see some pictures of the set up when you get the chance. Who invented it buy the way?

This will answer your questions. Its been around for longer than people believed it could work. I think interest in VG's and their being approved by the FAA has brought dimpletape new attention. It was also one of the featured products at Oshkosh this year and that's how I learned about it. I don't know within what limits it can be used on a certified aircraft, mine is experimental. The inventor, Anthony Occhipinti lives in Louisianna and is about 83 now. He told me the Tailwind he built and originally installed the first dimple tape on suffered complete submersion from hurricane Katrina. He is restoring it yet. Mhttp://www.dimpletape.com/

http://www.dimpletape.com/ Things don't always work like they're supposed to. Check the date on the article from Sport Aviation, 1998.

Definately keep us posted! If it help at all, I'll try it on my Sportsman. I'd love to come up with a way to arrest the sink rate on landing.

So, I can go wash my 172, leave a strip of dirt along the top of the wing where it's hardest to reach, then actually tell people that it's for performance reasons!

Ok, will post more on the effects as I go. If I get an increase in rpm over my baseline test again I will have to repitch the prop, but that would mean I am further reducing drag. Struts next and then the prop.
Good point about the dirt, kevbert, even though you meant as a joke, I wonder what will happen if the dimples are not kept clean? I will find that out too being down on the farm as I am but they do look easier to clean than VG's.

On gliders, zig-zag tape is usually applied at the point that laminar flow starts to seperate. The zig-zag tape serves the same purpose as dimple tape, in that it energizes the boundry layer and helps keep it attached. If the flow seperates, it forms a drag bubble - - something to be avoided if possible.

One way to determine proper placement is by applying used motor oil ahead of where flow seperation is suspected. This can be on the top or bottom of the wing, elevator, on the rudder etc. After a test flight, the oil will have flowed back and pretty much stopped at the seperation point.

Tape is sometimes applied just ahead of control surfaces to make them more effective and to prevent stalling etc.

On my Schleicher ASH26E, they actually use very small NACA vents to pressurize the flaps and ailerons. Then there are hundreds of little SS lined blow holes that keep the flow attached with even less drag than the tape would cause.

bumper

Back to the dimple tape. I was thinking that it might help on an old strait tail 182. For tht matter do you think that an inverted dimple would do the same thing.

Probably could not get a 337 for either. Maybe I will just park the plane in a thunder storm and wait for the hale.

Tim

The reversed dimple tape might do the same thing but by putting the bumps upward could also increase drag. I would be interested in seeing your results if you can find a way to test it. As far as my own experience I have not applied anymore dimple tape to my Tundra since applying it to the wings. I am still assessing what I have accomplished with the wing treatment also I have limited time now to do more than focus on my fall harvest. I did get to take a nephew and his two pheasant hunting companions for a ride last weekend following a rain that shut down the harvest. I have this to report from that flight:
The Tundra has an minus 8 degree flaps position. It is for the purpose of tipping the flaps upward of neutral of the trailing edge of the wing position. You may be familiar with this in the Maule. In the negative flaps position it destroys some of the lift of the wing and reduces some of the drag. When I use this setting in the Tundra I always feel the nose drop a little and I pick up anywhere from 8-10mph and retrim. Well I had yet to try this flap setting with the dimple tape in place until this past flight. In cruise with the dimple tape and flaps zero I had gained a solid 8 mph over zero flaps and no dimple tape. ( I reported this on my earlier post.) When I set the flaps to the negative position to my surprise the -8 degree flaps setting did not produce an appreciable gain in speed. What gives? I think the dimple tape provides a nearly equal reduction in drag with flaps at zero as does the negative flaps setting without the dimple tape.
This says to me that the dimple tape is efficient in reducing drag. I have not made enough landings to say that I have reduced the sink rate over what it was but if I have reduced drag on the wing without affecting stall speed then I think that is what it has done. Does someone have another take on this?

I'd be a little worried that it's reducing lift along w/ your reduced drag. Have your stall speeds been affected? Below is a post I copied and pasted from Oshkosh 365 that I read last night.

By Charles Horton
"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"

Ochippini is the name. Thanks for posting your results. My purpose was to get reduction of drag on the wing in order to reduce sink rate and thereby lower touch down speed without addition of power, or at least with less power. If dimple tape were to work on a fixed pitch prop, it might well improve prop efficiency but its use on the prop would have no effect on the power off characteristic of the wing at flare or it's touchdown speed. That is why I have focused on it's use for the wing. The other position I will go for is the two struts on each side. Occhipini did say that his experience with dimple tape on the prop showed improvement on thicker chord props such as his own wooden one but had less effect on thin aluminum ones.
I have a question for anyone with VG's on a Maule. Do the VG's still let the reflexed flaps increase speed at cruise or does their use result in reduction of enough wing drag that there is little to be gained with the negative flap setting?

Anthony C. Occhipinti