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Oct 29, 2015, 09:08 AM
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Discussion

Best airfoil for flying wing?


Am designing a flying wing similar to the X8 Skywalker and the RV JET with a 2.3m wingspan and 20 degree sweep but was wondering what would be the best airfoil?
Have settled on the MH60.
anyone have anything negative to say about the mh60 tho?
otherwise i was thinking MH45,
Eppler 180/184
Eppler 222/230
How important is reflex in a flying wing as MH60 doesn't seem to have any...
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Oct 29, 2015, 09:47 AM
Ray
I recently used the MH60 on a 62" WS (52" + 10" blunt nose) wing and it flies great. I've used MH60, MH45, and PW51 on similar wings and considering the build tolerances I can't say they're much different.

Ray
Oct 29, 2015, 10:04 AM
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Im being fussy but I'm wanting to do a very technical build.
I chose mh60 over mh45 as this will be a larger fpv wing and i read that "At higher wingloadings (MH45) there is a lack in performance (sinking rate) in comparison to MH60 ."
The FX79, X8 and maybe rvjet all seem to have some noticeable reflex however...
Oct 29, 2015, 10:46 AM
Registered User
Something like the X8 Skywalker is not "very" high aspect ratio.
Unless you're doing something in the very high aspect ratio range, you're not going to see appreciable differences between the choices mentioned (and they're all reasonable choices).
Also, consider the flight duration of a typical "X8 Skywalker"-like airplane. For these relatively tiny duration flights, the difference between the various airfoils mentioned is going to have minimal impact on "efficiency" (battery consumption rate due to drag).
Oct 29, 2015, 12:46 PM
Ft Lauderdale
Number_6's Avatar
Hi,

What material are you using to build your wing?

Oct 29, 2015, 04:02 PM
Chasin' that Neon Rainbow
Grantham Kid's Avatar
I wouldn't copy the X8 too close. It has bad tendencies to flat spin to death.
All flying wings I know have reflex, not just the ones you mention.
Oct 29, 2015, 09:25 PM
Registered User
Reflex is Either intrinsic in the Aerofoil design OR in upturned full span Ailerons.
Won't fly without it
Oct 29, 2015, 10:10 PM
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I've been building carbon fibre hydrofoils, so it will be made from prepreg vacuum bagged carbon fibre.

yes with the regards to reflex was thinking if i had to use reflex i could use a root foil with some reflex then changing to a more symmetrical foil at the tips
Oct 30, 2015, 01:00 AM
Registered User
By the way, for the part of the wing that's inboard of the MAC, you generally don't want reflex - discussed in-depth in various threads on this site, if you're interested why this is so.
Oct 30, 2015, 04:22 AM
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Sorry you are correct, i listed them in the correct order at the start
Nov 02, 2015, 10:23 PM
We don't need no stinkin' tail
RPM314's Avatar
Quote:
Originally Posted by Bare
Reflex is Either intrinsic in the Aerofoil design OR in upturned full span Ailerons.
Won't fly without it
Reflex is one component of pitch stability in tailless aircraft, the other main one being washout for swept wings. You can have a plane that's fully stable with only one or the other, but most use some mix.

Quote:
Originally Posted by nuteman
By the way, for the part of the wing that's inboard of the MAC, you generally don't want reflex - discussed in-depth in various threads on this site, if you're interested why this is so.
If the wing is tapered, the root (inboard) section has the largest influence on the craft's overall pitching moment due to the airfoil. It also influences overall pitching by virtue of all the lift it's creating ahead of the CG.
Increasing reflex in the root area will pitch the plane up due to the higher pitching moment of the airfoil there. It will also try to pitch the plane down because there will be lower lift in the front, HOWEVER that can be remedied by building the root section at a higher AoA than the tip section.
The question of which tendency wins out is tricky. The big factors are sweep and taper; more sweep means that the lifting tendency will be more important, and more taper means that the pitching moment tendency will be more important. You gotta do a LOT of math to figure it out. The SWIFT is an example where changing root reflex has basically no effect on pitch.
Nov 09, 2015, 03:51 PM
Retired CAD guy
birdofplay's Avatar
did you catch my foil data on the "other" thread ?

https://www.rcgroups.com/forums/show...3&postcount=20
Nov 12, 2015, 04:39 PM
Proud to eat Kraut ;-)
Julez's Avatar
I can definitely recommend the PW line of airfoils. I find the MHs a bit outdated, also due to their laminar separation bubble. I also don't like the stall characteristics that much.

If you want to thermal, take the PW106.
For allround flying, the PW75 is good.
For speed, there's the PW51.
Jul 15, 2019, 03:25 PM
Registered User
Hi guys.
I will build small plane, something like skyhunter.
Wingspan will be 40" or 1000mm
Wing area 21.5 dm2
Flying weight will be around 900g-1100g
Motor: propdrive 2830-1200kv
prop: 8x4, 8x5, 8x6 or 9x4, 9x5 i will test it but with 8x4 I have trust around 1200g with 19A
With 9x6 is 1500g with 30A on 4s
I need help with selection which airfoil will be right for me.
My expectation is max speed around 120km/h (70-80mph) maybe more.
So can you recomend me something good?
Thank you
Jul 15, 2019, 06:52 PM
Retired CAD guy
birdofplay's Avatar
Marske P3 reflexed airfoil

Jim Marske was the guy who partnered with Roncz on the Gemini

What I uploaded was proffered by Jim himself.


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