mberme

Hello
I would like to construct a F7U to scale 1/7 th.
Wings span 70 inches and chord 18 inches. 850 sq. in.
To equip it with two EDF 90.(MW 44)
The Eppler E334 is a good choice?
To use Slats, it is necessary?

Thanks
Manuel

pimmnz

The thing is a delta, any noncambered foil will do, slats not necessary. A cambered foil (like the Eppler) will have to great a C.P movement and need too much elevon offset, just added drag you don't need.
Evan.

Ed_Moorman

My Feedback: (1)

The F7U Cutlass is more of a swept wing, tailless design. For a powered model, I would use one of Bill Evans' airfoils that he used for many of his Simitar designs. It is a reflex airfoil and flies extremely well for powered flying wings. The airfoil is called the Evans Simitar Airfoil 40 or ESA40. You can find the data in several places.

mberme

Hello Edd
The Bill Evans ESA40 is airfoil for flying wings "Planks"
I look for a Airfoil for a Tailless Swept wing.
I have found the airfoil S5010, it might serve?

Thanks
Manuel

Flypaper 2

Just looked at some photos of a real Cutlass I got from Bob Banka a long time ago. Looks like a conventional , thin, semi symetrical wing.

BMatthews

For a project like this I'd probably go with a scale thickness symetrical airfoil.

Then I would do the MAC (mean aerodynamic chord) calculations and plan on putting the CG at the 20 to 22% location of the MAC. There's online sites that let you input the wing dimensions and they calculate the MAC for you. There are links in [link=http://www.rcuniverse.com/forum/m_2867994/tm.htm]THIS THREAD[/link]

Now you will want to figure out how much washout twist to put in the tips to balance this CG location. There is a very nice calculator that runs in Excel at this site.... http://www.b2streamlines.com/Panknin.html . If you don't have access to Microsoft Excel then you can download Open Office from www.openoffice.org and install the package and the Panknin twist spreadsheet calculator will run on that. Note that for a symetrical airfoil the Pitch moment coefficient is always 0. This calculator will tell you how much twist to build in for your 20% MAC CG location. You may have to sort of make it run backwards by altering the wing twist a number of times until the CG comes out to be at the proper location but it is easy to do.

In the end the elevons may require some fine tuning but this should get you into the ballpark.

Good luck.

mberme

Thank you very much.
With these tools I can obtain good results.

Regards
Manuel