airfoils for an old flyingwing

[Mucksmear]

Planning for my next build - Grahm Jones' 1972 Soar Jet (https://outerzone.co.uk/plan_details.asp?ID=9235)
I'll be making some aesthetic adjustments to the top of the fuselage for reasons of personal taste.
Here's the specs:
Span: 72"
Airfoil: unknown symetrical
Root: 19.75"
Tip 6.5"
LE sweep: 28.8 deg
Twist: none
Elevons are a little less than 1/2 span and 1/4 chord at the wingtips.
Elevons are set with about 11 degrees up or 3/8" at the TE.

Question for you aero-gurus: IF one of you were building this, would you bother to change up the airfoils to something "better"? On a "vintage" sport design like this, would there even be any noticeable improvements from using reflexed airfoils given the old-school construction (built up balsa D-box wing with capstrips)?

 

[Red]

I would for sure update the airfoil, if for nothing else to get rid of the trim drag associated with all of the up elevon required in the original section. Something like an MH60 (might be too thick) at the root transitioning to an MH62 at the tip would be great. If you don't want to go through the hassle of transitioning the airfoils, just use the 62 all the way and add 1 degree of washout. PW51 would also be a good choice. It will be a sweetheart. Cool looking plane!

Please post build pics.

MH 60 10.08% (mh60-il)

Details of airfoil (aerofoil)(mh60-il) MH 60 10.08% Martin Hepperle MH 60 for flying wings

airfoiltools.com

MH 62 9.3% (mh62-il)

Details of airfoil (aerofoil)(mh62-il) MH 62 9.3% Martin Hepperle MH 62 for flying wings

airfoiltools.com

PW51 (pw51-pw)

Details of airfoil (aerofoil)(pw51-pw) PW51 Peter Wick. Airfoil for plank model gliders

airfoiltools.com

Red

 

[Wayne]

Totally agree with Red! Update the airfoil!

Looks like a neat project.

There are a range of airfoils that could be used. It is basically a chevron flying wing with a fuselage.

 

[Mucksmear]

Thanks for the input guys!

The most that I’ve played with flyingwing twist angles with anything beyond just guessing, is to compare root and tip profiles at an a given Re number and then measure the angular diff between the stall AoA based on the graphs generated by AirfoilTools… so that the wing tip stalls at the same time or later than the wing root.

I have not been able to wrap my brain around the issues of pitching moments.

I’ll check out your suggested airfoils

 

[Wayne]

Better hurry up so you can bring this one to Sunset.

 

[Mucksmear]

Edit - I posted the wrong combo of foils, ok fixed now:

Ok I just spent some time playing with the suggested airfoils plus a few others in the family on AirfoilTools, so as a followup, what do you guys think of the following?

Just guessing a typical airspeed of about 33 mph +/- gives the following Re for the root and tip chords:
Root Re: 530,020
Tip Re: 174,210

MH44 is not excessively thick at a root chord of 19.75" (from a purely aesthetic/practical standpoint)
MH62 at the tip

Is building in 1.5 deg soley to prevent tipstall the right thinking here?
Im assuming a linear transition from root to tip airfoil

Also, any thoughts on the original design's outboard elevons, vs outboard ailerons and inboard elevator? Sparating the controls could allow me to play with flaps by countering pitch changes with the ailerons.

 

[iti20090]

Regrets the belated reply. If you would like to stay with a symmetrical section, friend Russ Conradt built us eyeball knockoffs of the 1985 Pharaoh delta from cores computer cut by Dave Schaller, using the SD8020 thinned to 8%. All three of the Pharaoh's fly magic, including in the mildest of conditions.

Flying 20% mean average chord CG, the aerie barely needs 1mm reflex in light conditions (zero in blow) and is obviously equally happy inverted.
Swept wing may a bit of challenge though.

Cheers
Dave