Quantcast

Flying wing as cheap and simple option for basic fun flying.

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
Hi FOLKS

Here is the analysis of that wing I posted with a 300KG load at various speeds and AOA.

With a 13 foot wingspan its not to bad, but obviously there is no extra drag or loss of lift from attaching an engine, undercarriage and person etc etc.

But it will give you some idea .as to what sizing may work.....

Cheers
Kevin
 

Attachments

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,019
Location
North Carolina
Hi FOLKS

Here is the analysis of that wing I posted with a 300KG load at various speeds and AOA.

With a 13 foot wingspan its not to bad, but obviously there is no extra drag or loss of lift from attaching an engine, undercarriage and person etc etc.

But it will give you some idea .as to what sizing may work.....

Cheers
Kevin
You might want to calculate the induced drag before getting too excited.
 

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
You might want to calculate the induced drag before getting too excited.
AGREED but thats another step along with the more significant CDA, and other factors, thats for the thrust to overcome....unless you want a glider.

The basic sizing starts with just the basic calculations to see what ballpark one is in size wise.....

How are those PXR airfoils coming along?
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,019
Location
North Carolina
Induced and parasitic drag both need taking into account for basic sizing. Make an estimate for each. If it looks ok, go deeper. Neither is hard to ballpark.
 

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
Induced and parasitic drag both need taking into account for basic sizing. Make an estimate for each. If it looks ok, go deeper. Neither is hard to ballpark.
Theres no point in doing them though if the Wing area and Airfoil cannot deliver the lift to match the weight at the RN you want with the air density and temp you input.

So I did those first, its an easier relationship for others to see making the differences.

The CDA(Parasitic) and Induced drags are added no matter what the configuration is and their variations are not likely to manifestly affect the sizing choices for aircraft in this class, they being neither gliders or highly efficient craft at high speed...the airfoil choice is more important.

The cross section of the fuselage, engine, pilot and undercarriage also make a far bigger difference.

As yet they dont appear to have been finalised!

I was merely adding a planform similar to the ones Cluttonfred posted, which I had provided a similar analysis for comparison between his SQUARE 144 and 112 SQ FT Planforms...
 

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
Please find attached the only data I could find on a PXE airfoil, extracted from this site, tested to the same inputs as the others.

Whilst it is not a flying wing airfoil, to much negative CM, it also has a narrow drag bucket and a lowish LD.

As well as less lift than the M6 or Horten, although it does have a benign stall.

Is there a Flying Wing airfoil in that range that we can perhaps compare?
 

Attachments

Urquiola

Well-Known Member
Joined
Aug 23, 2013
Messages
98
Location
Madrid, Spain
As discussed, probably no cheaper design could be found than $100 Glider by Werner Lutz Giessen Germany -Mechanix Illustrated Dec 1951 .jpgthe Flying Wing Glider by Werner Lutz in image. I failed in having more data about inventor, as to have plans. Any help? Blessings +
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,019
Location
North Carolina
Please find attached the only data I could find on a PXE airfoil, extracted from this site, tested to the same inputs as the others.

Whilst it is not a flying wing airfoil, to much negative CM, it also has a narrow drag bucket and a lowish LD.

As well as less lift than the M6 or Horten, although it does have a benign stall.

Is there a Flying Wing airfoil in that range that we can perhaps compare?
PXE airfoils are churned out by a spreadsheet I made. Currently using the 4 digit thickness distribution and 6 digit camber lines. I combine several camber lines to alter Cm and stall. I add camber lines to thickness riblett style. I haven't got around to trying the proper NACA way yet.

Heres one aimed for Cl=0.5, Cm=0.03 using a=0 and a=1 camber lines. Haven't tried it in XFLR5... Change .txt to .dat and hopefully your analysis program will eat it up.
 

Attachments

cluttonfred

Well-Known Member
HBA Supporter
Joined
Feb 13, 2010
Messages
7,559
Location
World traveler
More details and images including a 3-view here: J2mcL Planeurs - Fiche planeur n°

It’s not obvious from the pics below but this was an open cockpit design with the pilot’s head above the wing.

As discussed, probably no cheaper design could be found than View attachment 99868the Flying Wing Glider by Werner Lutz in image. I failed in having more data about inventor, as to have plans. Any help? Blessings +
 

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand

Attachments

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
PXE airfoils are churned out by a spreadsheet I made. Currently using the 4 digit thickness distribution and 6 digit camber lines. I combine several camber lines to alter Cm and stall. I add camber lines to thickness riblett style. I haven't got around to trying the proper NACA way yet.

Heres one aimed for Cl=0.5, Cm=0.03 using a=0 and a=1 camber lines. Haven't tried it in XFLR5... Change .txt to .dat and hopefully your analysis program will eat it up.
Thanks for that Pictsidhe

Please find attached the analysis of the PXE500 against some of the previous others.

That has the CM in the right place and the benign stall but drag is still high and LD low. Maybe because of the 17%?

I have also added a Riblett REFLEX mod 15% I did after reading his book some time ago, it gets very good CM but overall performance is only fair.

In this Reynolds range it seems to be that 12-13% is optimum to get the maximum area under the Cl and LD curves.

THE ISSUE IS ALWAYS THAT AS ONE GETS DOWN TOWARDS ZERO CM THE LIFT REDUCES..........

Nature already knows this because I have a laser scanned wing profile of an Eagle whilst its soaring, which when analyzed is very illuminating!

Perhaps for another day....

Cheers
Kevin
 

Attachments

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
918
Location
Evans Head Australia
The 2D airfoil data is all very interesting and very applicable for ARs > 3 but for very low ARs (1.2-1.3) the planform is a greater predictor of low speed lift and stability. For very low AR the airfoil should be chosen for low drag, low speed lift is provided by the vortex generated over the upper surface at high alpha by the planform shape.
 

cluttonfred

Well-Known Member
HBA Supporter
Joined
Feb 13, 2010
Messages
7,559
Location
World traveler
rotax618, do you have any specific examples of something like high lift and low drag airfoils at AR of 4 and 2 so we could see the differences in practice?
 

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
Hi Matthew

There is no specific airfoil.....as such

The SPEED and REYNOLDS NUMBER define what any given airfoil can do.

I posted that spreadsheet that shows how the CHORD and SPEED generate the RN required to test at.

So for a plank it is easy you just choose the LOW SPEED(STALL) and HIGH SPEED(VNE) as well as your CHORD, that then gives you two RN numbers.

That is the RANGE you would test across.

Its a bit more complicated if you have tapered wings, where the ROOT CHORD may be TWICE the TIP CHORD!

You then have to assign weightings that, favour/or not, the chord based on AREA, as obviously the longer CHORD section provided the greater % of total lift.

So optimizing for 52 MPH with your approx 7 Foot CHORD we have done all those tests at an RN of 3,363,000.

You can change the CHORD AND SPEED in the GREEN cells in the spreadsheet and it will give you the RN number. The AR ratio only has an efficiency bearing later and it is a small component at these low AR's proposed.

Here it is again:

Cheers
Kevin
 

Attachments

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
The 2D airfoil data is all very interesting and very applicable for ARs > 3 but for very low ARs (1.2-1.3) the planform is a greater predictor of low speed lift and stability. For very low AR the airfoil should be chosen for low drag, low speed lift is provided by the vortex generated over the upper surface at high alpha by the planform shape.
You will see that those GOOD airfoils of the bunch have LOW drag.......at those large Chords...for the low and high speeds.....

Is anyone actually planning a low speed extensively swept back planform in this class of usage?

How much Vortex lift do you anticipate you would get.....and how would you calculate it!
 

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
You will see that those GOOD airfoils of the bunch have LOW drag.......at those large Chords...for the low and high speeds.....

Is anyone actually planning a low speed extensively swept back planform in this class of usage?

How much Vortex lift do you anticipate you would get.....and how would you calculate it!
Heres the DM1 in action, it doesnt look great at low speed to me....with only tip vortices even at a high AOA...


They later put sharp edges on to get a proper vortice going across the wing but who is going to do that in practice..


Heres the nose PIC and relevant studies: One of which L6K20 is to large for this board(PIC)
DM1 OTHER STUDY.png

SAH-Lippish_DM-1 NOSE.jpg:DM1 DIMENSIONS 1.pngDM1 DIMENSIONS 2.png
 

Attachments

WINGITIS

Well-Known Member
Joined
Jun 24, 2020
Messages
300
Location
Wellington, New Zealand
Heres the DM1 in action, it doesnt look great at low speed to me....with only tip vortices even at a high AOA...


They later put sharp edges on to get a proper vortice going across the wing but who is going to do that in practice..


Heres the nose PIC and relevant studies: One of which L6K20 is to large for this board(PIC)
View attachment 99887

View attachment 99883:View attachment 99884View attachment 99885
A normal NACA 0015 has good CM(POSITIVE) but a lower lift and more drag than the best of the others......as well a sonly low to fair LD, at the speed/chord we are testing.

Not sure about the 0015-64 they mention, I cannot find it co-ordinates.
 
Top