Wortmann Airfoils

[Mike Switzer]

Does anyone know of a book or technical paper that discusses the various Wortmann airfoils & their intended uses? I have found a couple sources for some of the coordinates but I have been unable to find any source that discusses the intended use of the various profiles. (I know a lot of his work was intended for low Re uses in sailplanes)

Most of the common airfoil design books were published before he did his work.

[Thomas Stute]

Franz Xaver Wortmann was professor at the Technical University of Stuttgart, Germany. I know that his airfoils are summarized in the "Stuttgarter Profilkatalog". For years I'm trying to get hold of one but up to now I didn't succeed. A few of his profiles are discussed in the book of Fred Thomas "Sailplane Design" which should also be available in the US. I have a copy at home. If you don't get hold of this very intersting design book I will be happy to provide you with some information of the Wortmann airfoil published in this book. Just drop me an email.

[tonycondon]

i don't know much about them except that they were good performers but also very susceptible to contamination. rain or bugs on the leading edge would have a significant impact on glide performance.

[Mike Switzer]

My sister is going to try to get a copy of "Stuttgarter Profilkatalog" thru the university interlibrary loan system, there are 25 libraries that have it.

I will have to brush up on my German, which I never was very good at. :)

Spruce has Thomas's Sailplane Design book for a way better price than anyone else.

My sister's search also turned up a Wortmann document discussing keeping insect contamination off wings using elastic surfaces - not real practical but I downloaded it from NASA.

well I was going to attach it but the "manage attachments" window isn't working properly

[Thomas Stute]

Mike, if you need some help with the translation german to English just drop me a note. I will be happy to help you.

[Mike Switzer]

Attached is the document about insect contamination

[Thomas Stute]

It is correct that all of the glider laminar airfoils are more or less susceptible for insect and/or rain contamination. I recall a gliding contest I participated in in the mid 1980s. The weather was quite poor for crosscountry flying but we'd got a task for the day (150 km triangle) and so we went. We got more overcast and the thermals got weaker and weaker. I spotted some gliders circling under the remains of a cumulus cloud and I hurried to join them with my LS-3a for probably the last thermals of the day. There was a Standard Cirrus, a LS-1f, a wooden Ka6Cr, a Bergfalke and me with the LS3a circling in the dying updraft. We all managed to keep our altitude but we were not gaining anymore. Now it was clear we wouldn't make it back home to finish the task (nobody did that day). And suddenly it started to rain, not heavily but enough to spoil our wings. And you could easily see the effects: First the Standard Cirrus dropped out and made an off-field landing, next was the LS1-f. I played around with the flaps to get some more lift but finally I had to land as well. Our comrades in the wooden planes with no laminar airfoil still remained aloft for some time but due to the dying thermals joined us on our landing field. This episode made the effect of rain on a laminar wing very clear.

[Mike Switzer]

One of his most popular airfoils is FX 63-137 which is used on all the Diamonds (including the HK 36 motorglider). I don't recall hearing anything about Diamonds having a problem with wing contamination.

[Thomas Stute]

We shouldn'd overestimate the "problem" with wing contamination. What really happens when the airfoil has collected insects or rain dropplets is that you do not benefit anymore from low drag due to the laminar flow since the airflow has changed to turbulent. This is meaningful for competition soaring and when looking for extreme performance wrt range or top speed. You will not simply fall out of the sky. And there were some measures we took trying to avoid contamination: washing, waxing and polishing the leading edge. This reduced the drag penalty and boosted our moral.
Having flown many different types with Wortmann airfoils I'm very fond of them. Most planes with Wortmann have very nice handling characteristics, especially in the high alpha region. for my own design I would be considering a Wortmann airfoil.

[Mike Switzer]

Well, phooey!! The only known copy of "Stuttgarter Profilkatalog" in a US university library has just been reported missing. I guess the others are all overseas.