Sailplane tape on DA40

Chris B · Post by **Chris B** » Wed Mar 12, 2014 1:18 am

Per Antoine's suggestion, here are a some pics of my DA40 with sailplane tape on a variety of seams. Installing all of this was about a 15 minute exercise. I suspect that the performance impact is de minimis, but at least this makes it easier to clean bugs from the gaps!

I also added a short section of tape on the leading edge of the OEM wing walk. Replacing the wing walk is such a PITA that I am hoping to stave-off delamination...

In a previous thread on the DA20 forum BrianB suggested Cumulus Soaring as a good source for sailplane "Bowlus" tape. Check here: http://www.cumulus-soaring.com/bowlus.htm

Chris

smoss · Post by **smoss** » Wed Mar 12, 2014 2:34 am

That tape looks like it would be a great alternative to the grey wing root molding that covers the gap where the wings hook on. The Diamond wing root seal is not only a royal pain to get on/in, but it degrades quickly over time and get little micro-cracks all over it. What do you think?

Paul · Post by **Paul** » Wed Mar 12, 2014 3:04 am

OK so I did this a few years ago. I did not tape anything near a control surface. If it made a difference, I'm not sure I could tell although it made me feel like I was faster. Then one day in cruise flight I stuck my hand out the side window in cruise (note: this will hurt as your hand will get knocked backward into the rear part of the window if you are not prepared). This had no impact on cruise speed and I figured if sticking my hand out into the slipstream didn't make a difference, speed tape probably didn't either. I had a little yellow staining from the tape when it came off that took some work to get rid of. I would say though my tape job wasn't nearly as good as the one in the pictures.

Chris B · Post by **Chris B** » Wed Mar 12, 2014 3:18 am

smoss wrote:That tape looks like it would be a great alternative to the grey wing root molding that covers the gap where the wings hook on. The Diamond wing root seal is not only a royal pain to get on/in, but it degrades quickly over time and get little micro-cracks all over it. What do you think?

Charles posted on this twice last year. One post had a happy outcome, but an earlier post did not. Perhaps he can add some real-world experience to this thread?

The sailplane tape is so easy to apply that I will probably try this first when my gray seals fall apart. In the meantime I am thinking about applying the 2" tape over the top of the seals, but would first prefer to get more first-hand experience with tape removal after long exposure to the elements.

Chris

Antoine · Post by **Antoine** » Wed Mar 12, 2014 5:47 pm

Chris thank you very much.

I think Paul's note deserves some debate and here is my 0.018 CHF - check out conversion rate.

I believe that one major cause of drag on the DA40 is interference drag:
A seemingly minor source of drag causes severely turbulent airflow that affects another surface downstream that is much bigger an was happily enjoying laminar flow. As Chris pointed out, the NLG is definitely such a case.

Now if you stick your hand out the window (ouch!) and nothing major happens, then my guess is that there is such a strongly energized airflow around the canopy that it re-attaches after this disruption.
I flew once in a very wet stratus cloud. We could see beautiful aerodynamic streamlines painted by water flowing on the canopy. The airflow looked perfect there.

This said, I am surprised you did not notice any difference. When flying in really smooth air, the smallest change in anything causes airspeed to vary, to the point that I pull my feet back and almost stop breathing when looking for a nice round number.

Back to Chris' pictures: I was also disappointed after tackling my landing light cover. It looked really ugly to start with. I spent lots of effort to make it look even uglier but at least fit properly. It got custom spacers to make it flush with the wing and a seal all around,
Even took out some of the screws, but nothing measurable happened.

I will tape the vertical stab fairing next flight and see what happens.

Lance Murray · Post by **Lance Murray** » Fri Mar 14, 2014 5:59 am

The Tape job looks great. I plan to do the same. It may or may not be faster but it looks cleaner and helps seal a potential moisture entry point.

I am also very curious about the use of turbulator tape on sailplanes and how we could benefit with it's use on a Diamond. I think it is about helping with glide performance at slower speeds at the expense of increased drag at higher speeds. Everything helps. Here is a source of the tape: http://www.wingsandwheels.com/page28.htm

Lance Murray · Post by **Lance Murray** » Fri Mar 14, 2014 6:51 am

Here is another thing I am curious about. Vortex Generators. http://www.microaero.com/pages/k_diamond.html,

http://www.avweb.com/news/reviews/18256 ... directed=1

carym · Post by **carym** » Fri Mar 14, 2014 1:00 pm

Lance,
I have no experience flying the same plane with and without vortex generators. However, when I purchased my C310B I had the shop put on the vortex generators. The pilot who flew the plane out from Hayward, CA to my home in Minneapolis, MN said that the vortex generators made slow speed flying, i.e. landing, much more gentle in that plane. I wanted them put on because it lowered the Vmc and this was my first twin so I wanted the extra safety margin. Since I experienced 4 engine outs in that plane (3 of them while in the air), and never had any real problem handling those engine outs, it is possible (?likely) that having the vortex generators actually did make the plane safer to fly.

smoss · Post by **smoss** » Thu Mar 20, 2014 11:21 pm

Chris, what size tape is that you used in the pics? Also, is that the Bowlus brand, or something else?

Chris B · Post by **Chris B** » Thu Mar 20, 2014 11:56 pm

smoss wrote:Chris, what size tape is that you used in the pics? Also, is that the Bowlus brand, or something else?

Hi Steve -

I used the 1" for everything, except 2" for the vents.

Yes, I used the Bowlus brand, although primarily because of the prior recommendation. Presumably there are differences between brands (adhesive, UV resistance, stability...), but I really have no comparison with any other sailplane tape. But that site seems credible & they like it - and probably have tried other brands...

Chris