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

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#### rotax618

##### Well-Known Member
Naturally the ability to control the thrust/drag couple is the distance the pitch control surfaces are from the aerodynamic centre. If you are talking about a medium aspect ratio plank, the application of throttle coulud cause a catastrophic stall if you were near the ground - its not a good design feature - stability in planks requires that the thrustline ahd drag as as coincident as they can be.
your idea would be acceptable fo very low aspect ratio planforms.

#### WINGITIS

##### Well-Known Member
Naturally the ability to control the thrust/drag couple is the distance the pitch control surfaces are from the aerodynamic centre. If you are talking about a medium aspect ratio plank, the application of throttle coulud cause a catastrophic stall if you were near the ground - its not a good design feature - stability in planks requires that the thrustline ahd drag as as coincident as they can be.
your idea would be acceptable fo very low aspect ratio planforms.
I agree it would be better with a low AR planform....IE not a Glider type.

But that still can be a plank!?

Is there an AR limit where a plank is not a plank?

In the earlier post I mentioned the use of a swept plank as well......

The wing on the D8 kit would have to be converted, as I mentioned, to something that was appropriate...

You will notice on their BASIC plane kit, not the D8, it had Ailerons set back on the simple wing which would help with the leverage issue.

In the NACA report that references the Fauvel AV-2 it states that the rear of the center airfoil is used to trim for thrust and it also implies that the motor pod may be able to have its angle adjusted.

If we have a French reader on here we may get more information from the PDF I put up that has his calculation results/graphs.

#### cluttonfred

##### Well-Known Member
HBA Supporter
I am happy to help but it's a pretty long article, somewhat technical and old-fashioned. Exactly what did you want me to translate?

If we have a French reader on here we may get more information from the PDF I put up that has his calculation results/graphs.

#### rotax618

##### Well-Known Member
The idea is possible provided that proper consideration is given to the thrust/drag couple, Gyro designers recognised this problem long ago, unfortunately too late for some lost pilots.
probably the best fuselage to copy for a high wing plank would be the HM14, it is super simple and the engine can be raised oe lowered to align with the drag vector.

#### WINGITIS

##### Well-Known Member
I am happy to help but it's a pretty long article, somewhat technical and old-fashioned. Exactly what did you want me to translate?
Many thanks Cluttonfred

From the bottom of the 1st page beginning at "Pour un allogement" to the bottom of the second page if possible.

That appears to be where the interesting stuff is...

Especially all the wording that is on those graphs on page two, he is referencing longitudinal balance or stability I would guess....

Cheers
Kevin

#### WINGITIS

##### Well-Known Member
The idea is possible provided that proper consideration is given to the thrust/drag couple, Gyro designers recognised this problem long ago, unfortunately too late for some lost pilots.
probably the best fuselage to copy for a high wing plank would be the HM14, it is super simple and the engine can be raised oe lowered to align with the drag vector.View attachment 101909View attachment 101910
I do like the adjustable engine height and longitudinal position of the mounting on that fuselage...

But it would probably be a lot easier to just work with the "dream classic braced" at $4000 USD and remove the elevator and rear horizontal stabiliser....modifying the wing to a better airfoil with some Sweep-back and keeping those Ailerons as Elevons... Then effectively your only modifying a few things and can build it easily, quickly and cheaply... The D8 would only need to be done if one wanted something that looked a lot better and made a bit of a statement. I dont think Polini power can really cause to many upsets as it has trouble motivating the MW9 Plank to reasonable performance, its not like a 100HP engine.... And even the Polini may be to expensive for some... #### Attachments • 39.2 KB Views: 15 • 37.5 KB Views: 19 • 37.9 KB Views: 19 #### WINGITIS ##### Well-Known Member Another variation tried before: #### Sockmonkey ##### Well-Known Member This is a closer approximation of what we want I think. You might want tip rudders, or it could be made Horten style so you don't need them. The big thing is that with nothing behind or below you but the seat, it's going to feel like flying naked. Plus it's easy to get into. #### erkki67 ##### Well-Known Member I still would prefer the Plank of Mike as a tractor. #### rotax618 ##### Well-Known Member I built an HM14, It was a long time ago but it only took 3 or 4 sheets of 1/8” ply and a few pine sticks for longerons, it certainly didn’t cost$4000. The bare fuse only took a week to build. I used spring steel legs for the UC but the original had wheel barrow wheels on a pipe axle tied to the lower longeron with bungees for suspension.
It is worth reading Le Sport de L’Air, it contains complete plans instructions and materials to build an HM14, the book is freely available on the net.

#### erkki67

##### Well-Known Member
I built an HM14, It was a long time ago but it only took 3 or 4 sheets of 1/8” ply and a few pine sticks for longerons, it certainly didn’t cost \$4000. The bare fuse only took a week to build. I used spring steel legs for the UC but the original had wheel barrow wheels on a pipe axle tied to the lower longeron with bungees for suspension.
It is worth reading Le Sport de L’Air, it contains complete plans instructions and materials to build an HM14, the book is freely available on the net.
Yes build the flea but only the 1936 version, DO NOT ATTEMPT TO BUILD THE INITIAL 1934 VERSION!!!

#### Mike W

##### Well-Known Member
Some nice pics of my plank.

#### cluttonfred

##### Well-Known Member
HBA Supporter
Great shots, Mike. Is that you in the cockpit?

#### Jsample40

##### Member
As the former pilot/ builder of multiple pusher powered Mitchell Flying wings, I believe the basic B-10 wing to be state of the art, even today. Don Mitchell, member of the original flying wing design/ build team... developed the original B-10 wing as a hang glider. In the 1980's several of us "Wing Nuts" further evolved the basic wing into aluminum "trike" shaped wheeled variations with pusher prop engine configurations. I started with 12.5 hp McCoullach go cart engines; Honda Odessy engines; 17 hp Zenoah snow mobile engines; and finally, the 25 hp twin cylinder horizontally opposed KFM 107 engines. Fiberglass pods streamlined the pilot area, landing gear, and propulsion systems to further perfect the combination. That was the most pleasureable, joy filled flying of my life time. I have never seen a more predictable flying wing with better performance characteristics in the 40 years since. The NACA 230-15 wing cannot be beat in my humble but experienced opinion. The B-10 design and drawings are likely still available today. Hats off to this 85 year old "test pilot".
Jay Sample (80 years young)

BJC

#### rotax618

##### Well-Known Member
I am not advocating anyone build a Flea, I was pretty disappointed with mine, I was advocating using an HM14 type fuselage for a high wing plank type flying wing. It would be the simplest arrangement to have an adjustable thrust line.
The only problem I can see is ingress and egress from the cabin below a wide chord plank wing.

#### Norman

##### Well-Known Member
HBA Supporter
Is there an AR limit where a plank is not a plank?
Why should there be? As I see it a plank is simply a tailless airplane that controls pitch by adjusting the airfoil pitching moment. A long chord allows you to do that with less elevator deflection so low AR is actualy an advantage in that one aspect. A long root chord also allows you to get more of the non lift producing stuff out of the wind which would seem to be a plus for reducing parasite drag but the induced drag of the short span pretty well negates that.

In the earlier post I mentioned the use of a swept plank as well......
Sweep is great but if your tips stick out of a rectangle defined by the root chord and span you realy shouldn't call it a plank see attachment.

The wing on the D8 kit would have to be converted, as I mentioned, to something that was appropriate...
Yeah it'd have to be converted. That thick high camber airfoil would be a lousy choice for a flying wing. You CAN get a positive pitching moment by reflexing trailing edge control surfaces but that dumps a lot of lift and creates a lot of drag (L/D goes down the toilet) so basically the only part of the kit wing that's usable is the spar.

#### Norman

##### Well-Known Member
HBA Supporter
Referring to the title of this list, That was the goal of the original BKB AKA the Kasper wing.
Lippisch built some fairly simple 'wings similar to the BKB in the '20s. The Storch V flew on 8 Hp but needed a bungee assist for takeoff.

#### pictsidhe

##### Well-Known Member
That's the closest thing i could think of, don't know if it's of any help.
View attachment 101889
That could be really interesting. I've watched a Fauvel doing aerobatics. A sawn off Pitts could be spectactular.