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Jul 15, 2019, 11:12 PM
Ft Lauderdale
Number_6's Avatar
Quote:
Originally Posted by macvidler
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...
Hi,
I had two bad experiences with long wing span, aft swept,
flying wings (83").
Issue was spars... could not build in enough strength to avoid
eventual flutter.

Once it flutters, might as well toss it in the garbage can.
Anyway, I use 12%-14% thick airfoils now if going over 60" WS.

MH60 is thicker of the two you mention.

The 20 degree sweep will act as some reflex.
Last edited by Number_6; Jul 15, 2019 at 11:31 PM.
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Jul 15, 2019, 11:19 PM
Ft Lauderdale
Number_6's Avatar
Quote:
Originally Posted by Groot
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
Hi,
Looking at pic....seems to be a Telemaster, flat bottom,
high lift airfoil. A ClarkY would be good also. Assuming
you are building with a separate elevator.
The old Telemaster plane wing was mounted at 4.5 degree
positive on main wing, 2 degree positive on elevator...just as an idea

If you are not using elevator (see Drak), the Marske P3 airfoil
would be better with its built in reflex... we are looking at a plank
shaped wing.

Edit....if you are looking for a fast airfoil, light plane, no heavy
lifting, I have used MH18b recently with good results. See pic.
Last edited by Number_6; Jul 15, 2019 at 11:44 PM.
Jul 16, 2019, 01:34 PM
Registered User
Thank you guys for respond.
I read something about airfoils and I found MH43 or maybe better for me MH42. It is used for F5D (elektric pylon racers) They have really similar properties like my build.
What do you think about these airfoils?
Jul 16, 2019, 10:36 PM
Registered User
Quote:
Originally Posted by Groot
Thank you guys for respond.
I read something about airfoils and I found MH43 or maybe better for me MH42. It is used for F5D (elektric pylon racers) They have really similar properties like my build.
What do you think about these airfoils?
A lot depends on your level of experience as a builder and pilot.
Can you give us your experience?
Also, for the scale and specs you mentioned, there is going to be very little practical difference between the airfoils mentioned - they're all reasonable.
At 80 mph speed, your primary build challenge for the wing is going to be strength.
But, based on the specs you gave for motor/ prop, I sincerely doubt you'll reach anywhere near that speed in level flight...
Jul 17, 2019, 01:07 AM
Registered User
So, i fly around 15 year's, last 5 year's FPV, so this project is for FPV. I like P51D so I have some models of it.
What I exactly need is airfoils which is maybe wind resistant, low drag, (better for speed) and lock in, stable and too good agile. So for these reasons I choose these airfoils.
But I never ever before make my own wing with specs. Just flat bottom wings but not fly great.
About my motor/prop setup. These is what I have at home, so I use it. Maybe I will be not so quick on air, but nevermind.
I just calculate what I can try and what I can reach with this setup. If I will build stable little bit agile plane with good flying characteristic's I will be happy. I love building my own
Last edited by Groot; Jul 17, 2019 at 01:15 AM.
Jul 17, 2019, 01:35 AM
Registered User
Quote:
Originally Posted by Groot
So, i fly around 15 year's, last 5 year's FPV, so this project is for FPV. I like P51D so I have some models of it.
What I exactly need is airfoils which is maybe wind resistant, low drag, (better for speed) and lock in, stable and too good agile.
OK, that gives us a much better idea of how to recommend.
At this scale, a desire for low wing drag is most affected by thickness-to-chord ratio (t/c) and aspect ratio (AR) - much more so than the particular style of airfoil (MH series, PW series, etc). So I would go with a an airfoil that has t/c of no more than 10% (even better would be 8%) and an aspect ratio of at least 9 (if you don't know what I mean by aspect ratio then look it up - it has a huge effect on drag).
Having said all that, know that hot-wire cutting your own airfoil takes practice. Even after getting good at it, you're unlikely to very closely match the airfoil you intended - but again, the t/c and AR are really the driving factors for drag.
Also, your pod/fuselage will have a significant effect on drag. If it is not streamlined, drag goes way up. Any other chunky protrusions on the airplane will also make drag go way up (clunky landing gear hanging out in the slipstream is a good example).
Jul 17, 2019, 02:11 AM
Registered User
Great, thank you.
Fuselage I have ready to go and it is big for more place for gear and for big batt .
But I made it with drag in mind. I have no landing gear.
About numbers which you write, sems like MH42 I think:
https://www.mh-aerotools.de/airfoils/mh42koo.htm
But I will look at PW series.
Thank you guys for you time


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