Hi All,

I am trying to make 4 airfoil shapes, to represent the 4 panels in a taped wing. I have recieved some information via email from someone who knows more than I do on this subject, but i am a little confused????

Airfoils are based on the Symetrical NACA 0012 airfoil, with the following changes:

Airfoil 1: Top 5%, Bottom 8% (inverted)
Airfoil 2: Standard NACA 0012
Airfoil 3: Top 6%, Bottom 5%
Airfoil 4: Top 6%, Bottom 2%

Airfoil 1 is the root
Airfoil 2 is the end of the first panel / start of the second panel
Airfoil 3 is the end of the second panel / start of the third panel
Airfoil 4 is the wing top airfoil

I would use Airfoil 1 at +3 degrees incidence, and Airfoil 4 at -3 degrees incidence - and airfoil 2 and 3 somewhere in between (depending on where they end up along the span).

Can anyone help me with instructions on how to make these using profili?

Also - I understand that the NACA 0012 means that the airfoil is 0% Camber at 0% of the chord, and is 12% of the chord thick at the widest part. How would I name the airfoils above?

Airfoil 1 - 13% - NACA ??13
Airfoil 3 - 11% - NACA ??11
Airfoil 4 - 8% - NACA ??08

Thanks - sorry if these are stupid questions, I am VERY new to this!!!!

tasesq:

Questions are never stupid.

You could start reading this, learning and trying to figure it out:

http://en.wikipedia.org/wiki/NACA_airfoil

Different % up and down means the airfoils at the points 1, 3 and 4 of the wing have some camber (non-symetrical).

Just calculate the camber for those and ask Profili plotting them for you. [sm=spinnyeyes.gif]

Regards!

You could plot each of your desired thicknesses in Profili, copy the results to a paint program, then combine the upper and lower profiles as needed...
For the first, plot an NACA 0005 and an NACA 0008.
Use the upper curve for the 0005 and the lower curve from the 0008 to get your desired shape.
And so forth.
Or, take the coordinates of each upper surface and lower surface and combine those into a new airfoil for Profili to plot for you.

Fantastic!!!

That is exactly what i was after.

Cheers - Merry Christmas.

Hi,

I have been thinking about it:

The instructions i recieved were:
"Airfoil 1 (wing root): top 5%, bottom 8%, thus giving 13% of thickness. Many real planes have such an inverted airfoil which I often used without problems"

If I were to take a NACA 0005, this would be 5% of the chord thick at the maximum thickness; Since it is symmetrical, taking the top coords would leave me with 2.5% thickness.

Similarly, if i took a NACA 0008, and took the bottom profile, I would have something that is 4% thickness.

Additing these two coords sets together would give me 6.5% thickness and not the 13% thickness?

Am I on the wrong track here?

Thanks!

You'd need to work with profiles twice as thick... a 10% for where you want the 5%, 16% for the 8%, etc.
I was wondering about the utility of such thin airfoils.
And use only the symmetrical series.
The semi-symmetrical 4-digits arch the camber line above the chord line, so a split along the chord line would give a totally different shape than using the symmetrical series.

Hi Everyone,

Merry Christmas - Thank you all for your help!

I just figured I can do a mix of two airfoils in profili; the professional version of Profili allows for a mix of two airfoils, with a bias on the upper and lower surfaces.

All i need to do (i will purchase profili first of course!) is, say for the 5% top, 8% bottom airfoil, mix a NACA 0010 and NACA 0016, and bias the top 100% to the NACA 0010, and bias the bottom 100% to NACA 0016! This results in half of the NACA 0010 (i.e 5% thick) and half the NACA 0016 (i.e 8% think) resulting in a 13% thick inverted airfoil!

Thanks for everyone's help with this one!

The only full-scales I'm aware of that have inverted profiles at the wing root are the L-1011 and DC-10.
The wings on these have a much larger operating range than a model, and have to be optimized accordingly.
I doubt at model Reynolds numbers such a complex wing would be any better than a more conventional distribution of airfoils.
L-1011 Wing Root...

Hi,

Yeah - it is really more so I can get a scale look to the model. The inverted root airfoil will have +3 incidence. I got these figures from http://rauch-airliner.com/Introduction.htm - his beautiful aircraft would have similar weights to my planned one, and similar airfoils etc.

Thanks for all yuor advice so far - I am like a sponge - if you can offer any other ideas i'll happily take them on board!

FYI - the model would hopefully have an all fibreglass fuse (from a mold) and a foam wing, balsa sheeted and glassed. The tricky bit will be to balance all the operating equipment that needs to be in the wing (gear, flap actuators x 3, and slat actuators) against the airfoil thickness! I am hoping to figure it out in Sketch-up in proper scale to try and get it all figured out!

Thanks!

There are other full-scales having inverted profiles. See wing root of this DC-8.

There are many commercial jet aircraft with these strange shaped wingroots, but the reasons for the shapes has more to do with wing/body blending and actual airflow patterns around these areas of the airframe. The shapes are optimised for minimum drag at cruise speeds and attitudes, with sufficient depth for the spars and fuel tanks. Unfortunately, using them in model situations will not result in similar results, models simply do not fly fast enough or have enough volume for these shapes to work. Although you may not like it, for maximum efficiency you will have to stick with typical model sections.
Evan WB #12.

Hi,

Thanks - these airfoils came reccommended from a model maker who specialises in airliner type models (A380, DC10 etc).

I thought that these reccommendations were reasonable, as his models would fly at similar speeds to the Global?

As you check the the site of rauch-airliner.com you could also see those profiles on model airplanes. The front view of the DC-8 model clearly shows the inverted profile at the wing root. It looks very scale-like and I don't think that the flight characteristics are so bad. Maybe fuel burn is a little bit higher as with a profile optimized for a model airplane...?