Airfoil for Lippisch DFS-40/Delta V - RC Groups
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Aug 04, 2017, 03:57 AM
Registered User
Discussion

Airfoil for Lippisch DFS-40/Delta V


Hello.

I'm at the very first stage of a new "winter-projec": a medium/big scale Lippisch DFS 40 (aka Delta V) RC model.

Unfortunately I have found very little info on the web and for what I know the real airplane do not exist anymore.

First of all I'm asking help for the airfoil selection.

On this RCG thread:

https://www.rcgroups.com/forums/show...0#post30817942

.......I read that the airfoil used on the small model is the Sipkill.

Now looking at this drawing I hope that some of you can help me to identify the airfoil used on the Delta V:
Name: lippisch_dfs_40_delta_v_polar_curve.gif
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Size: 68.6 KB
Description:

Thank-You!

ettore
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Aug 04, 2017, 09:45 AM
internet gadfly
nmasters's Avatar
It looks similar to the NACA 32015.
Aug 08, 2017, 02:37 AM
Registered User
Thank-you.

Unfortunately on this website:

http://airfoiltools.com/search/index

………. I can't find the NACA 32015.

Do you mean 23015 ?

ettore
Aug 08, 2017, 10:18 AM
Herk
HerkS's Avatar
Hi Ettore - I think Norm did mix up the first two numbers, but considering that, the 20315 does look very close to the one you posted.
Aug 08, 2017, 10:30 AM
Herk
HerkS's Avatar
I do have data for the NACA 32012 which I modified to the 15% thickness.

I have attached an image of its shape and list of data points. Good luck with your project - please continue your thread here as you build and fly it.
My best wishes Herk Stokely
Aug 08, 2017, 11:08 AM
less is more
Knoll53's Avatar
I am not sure what flight qualities you are aiming for Ettore, but my Plank 368 uses a similar NACA airfoil. The thread has flight videos of this big plank in slope lift..............which makes any glider look good. Well almost any glider.

It is a draggy airfoil but from my experience, it has no bad habits.


Kent
Aug 08, 2017, 11:15 AM
internet gadfly
nmasters's Avatar
Sorry. Yes I wasn't paying attention and let my fingers wander, 23015 is correct. You might also look at the Go-765. Lippisch used that one on the Me-163. If you don't find the Göttingen 765 on airfoiltools you can copy the coordinates from this page. There is a spreadsheet at the bottom of this page that uses a formula that was used in Germany at that time to generate reflexed airfoils.

--------.~.
--------/V\
------//----\\
-----/(------)\
----(^^)---(^^)--Norm
Aug 08, 2017, 11:29 AM
less is more
Knoll53's Avatar
Holy Moly ! Look at the reflex on that thing. That's what you call dedication to the cause.
Aug 08, 2017, 12:04 PM
internet gadfly
nmasters's Avatar
Quote:
Originally Posted by Knoll53
Holy Moly ! Look at the reflex on that thing. That's what you call dedication to the cause.
Yeah and it has lower CLmax than a similar thickness NACA 5 digit section but also lower drag so a better L/D and section power factor. Softer stall too.
Aug 08, 2017, 01:36 PM
Registered User
Thank-You Friends!

The airfoil used on the DFS-40 is very similar (maybe the same??) to the Me-163 Komet's airfoil.

For my DFS-40 model I'm thinking about a "scale-speed"…….slow and easy….I hope.

I'm still evaluating the model's dimensions and something like 2 meters or more could be right.

The wing's area is huge so no problem for the wing load factor.

The three big problems are:
- retracts
- canopy
- motor cooling

Maybe the DFS-40 static kit could be useful to reproduce the landing gear retract system:
DFS 40 (4 min 28 sec)


But before spend many hours on the "final" model I think that a smaller RC glider without retracts and canopy could be great for some flight tests and for the C.O.G. location.

Thanks again.

ettore
Aug 09, 2017, 12:10 AM
B for Bruce
BMatthews's Avatar
Looking at that small sketch on the Cd graph about all that one could possibly surmise is that it likely has some reflex to the airfoil. It's there for illustrative purposes of some parameters or spoiler movement or something from looking at the lines to the wing section. I doubt that it's a proper shape. But if you want to pull more than this from it I'd say it has more in common with the 5 digit NACA series than it does with that airfoil from the Komet.
Aug 28, 2017, 05:07 AM
Registered User
Hello!
I have I very basic question and I'm sure that this is the right place to ask

After some research I have the confirmation that the airfoil (Gottingen 765) used on the DFS-40 is the same used on the DFS 194: the prototype version of the Me-163A Komet.

So for my small DFS-40 test model I will use the Gottingen 765 airfoil.

I suppose that the airfoil will change going from the root rib to the external tip rib.

So for the tip rib (of course with the proper negative wing twist) I can use a symmetrical airfoil.

The software used for the wings will take care of the proper ribs modifications along the wing length.

Your suggestions will be very appreciated, thank-you!

ettore


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