Basic Design Theory and Aerodynamics behind Flying Wings and Tailless Aircraft (Part 1)

This is a (regretfully short-handed) summary of my notes for one of my recent home projects in which I challenged myself to design, build, test, and fly a flying wing from scratch. The basic design theory in this video covers surface-level stability (excluding stability derivatives), airfoil design, tailless aircraft performance characteristics, and aircraft config/design methods to generate static stability (q, R, L) in the absence of fins or tails. In a future video, I'll dive into the stability derivates and which are significant or not significant for tailless aircraft, as well as vertical fin design theory, it's role in stability, and the effects of hedral and gull on the aerodynamic performance of tailless aircraft.

There may be small bits of information or nomenclature usages in this video that are incorrect or used improperly - if you catch any, please comment and let me know so I can learn from this. The whole reason I pursued this design and test challenge was to learn anyways!

*The green text at 10 47 should say NACA0010, NOT MH61*

0:00 Intro
1:29 Tailless Aircraft Overview
4:38 Aerodynamic Introductory Topics
5:24 Longitudinal Stability Calculus Fundamentals
9:48 Overcoming instability in a wing
11:44 Downsides of Reflex
12:17 Effects of Twist
15:30 Lift Distributions
17:53 Proverse Yaw
19:05 Taper Ratio

My twist spreadsheet:

Some sources:

[BenjaminWagner-yp]

Excellent video GabeFPV. You pretty much covered the key points of 2 years worth of aerospace coursework in just the right amount of detail while stringing together a great narrative. Good slides too. I feel like I could go back and pass my intro to aerospace final with flying colors😂. (A long time ago for me)

[brucematthews]

Very well explained. Good level of detail without burying us in math. I'm looking forward to the next part.

[Tensho_C]

finally an in-depth video on unconventional wing designs. been looking for one since the nasa prandtl project came to my attention

[zipped]

Current Aerospace Engineering student here (undergrad), and I loved this video!

[paragjiwtani]

The amount of knowledge crammed into 23 minutes is insane! Can't wait for the next part.

[antrygrevok]

Incredible amount of help you've given us, in this..

Couple of gifts for you, ( hopefully ),
from an autistic who's spent a few years thinking on aircraft-design,
& tried working through Raymer's university-textbook
( until the damn carelessness in his work stopped me:
sometimes his explanations aren't clear,
& his books all seem to need much more rigorous copy-editing!!
*don't* allow mistakes into textbooks, eh? )

1. Please, *PLEASE* try Julia with Pluto, instead of spreadsheets:

You can make your work be compounding-capability in ways that spreadsheets sabotage..

( I intend that all my aircraft-design stuff
be able to generate variant-aircraft through calculating everything,
just with some parameter-changes,
& Julia+Pluto's core to that.
Spreadsheets constrain one's work much more,
the Julia/Pluto combination is much more parametric/dimensional/live )

2. given that there is a portion of any real ( full-sized ) aircraft which is likely *usually* turbulent-boundary-layer,
consider doing the golf-ball dimples thing,
to that portion of the surface,
to energize the boundary-layer a bit

( there are 2 competetion-level golf-balls, apparently, & they've got different dimples-patterns:
1 is all the same, the other has some-larger/some-smaller.

I *think* the dimples need to be proportioned to either the Re or to the dimension of the object,
but don't know which, yet,
or if both make-difference.. )

3. Please consider doing experiments re aircraft icing,
with a boat hull coating called Silic One, which is a silicone-silane anti-fouling..

If it makes it impossible for ice to accumulate onto a surface,
it may be a significant safety-investment for some aircraft..

( I suspect that the blown-wing with aluminum in it, in the ATR-72 might have been part of the problem:
blown surfaces tend to be colder,

& having a prop blowing an aluminum-wing, or partially-alu-skinned-wing,
seems to me like an icing-suicide-machine..

I don't know how long it'll take for the accident-investigators to report,
so may have to wait a few years to know if this insight is right )

4. I don't understand why flying-wing tankers aren't the normal
( just a random opinion of mine, for the last few years ).

You can refuel more aircraft behind the thing, through more spanwise drogues,
AND you waste less fuel staying in the air, while doing the work?

Seems win-win, to me..

5. Please consider trying fractions, instead of percentages, in your work:
Nature seems to work more that way.

( e.g. natural ocean waves, that aren't, through shelving seafloor, becoming breakers,
have a 1/7 ratio of height to length )

You said the optimal change from lift to negative-lift is around 70%,
I suspect that it's either 2/3,
or it's in a range ( due to specific-configuration ) between 2/3 .. 3/4.

Once I realized that for sailboat & aircraft design
( both are related, & the lessons learned in each often do improve one's competence in the other,
please consider "Principles of Yacht Design" to be the basic-text for it,
& the North Sails textbook to be the pinnacle of sail-design books ),
the fractions-orientation simplifies/clarifies much..

Like when I realized that the NASA recommendation for quiet operation,
to keep prop-tip-speed down to 0.6 Mach was *actually*:
the upper-surface of the prop has airflow around 4/3 of the prop-blade-speed,
& 4/3 * 0.6 == 0.8,
so you're getting close to transonic, then..

THEN it made much more sense, see?

( having a number where it's actually the interaction of 2 distinct fractions,
if you know the basis-fractions, then it can make much more intution-sense,
and THAT is one's designing-instinct: one's intuition.

Get it right, consistently! : )

Or, another e.g.:
make a yacht-rudder a symmetrical NACA foil of 1/8, aka 12.5% chord/thickness..
but if you want a low-drag foil? go to 1/12.

Why is so-simple a thing important?

The difference between a displacement-mode monohull
& a faster-than-displacement-mode trimaran
means that the optimal rudder-thickness may be thinner, for the trimaran,
right?

This hands me the exact range to try: 1/8 .. 1/12.

I already KNOW the right-answer's within that range! ( :

---

Please identify for us the textbooks you recommend,
for us to learn these things *properly*.

I'm already presuming that Doug McLean's Aerodynamics
( arguing from the actual physics, or something like that )
is the proper aerodynamics book to rely on

& that Snorri Gudmundsson's General Aviation book is the book to replace Daniel Raymer's one..

( please correct me if I'm wrong )

but that still leaves massive gaps in one's learning, doesn't it?

Please identify the dimensions-of-knowledge,

& the specific self-learning textbooks you recommend in each,

not as a reply to me,
but rather as the text-underneath your videos,
so that everyone readily sees that!

Also, please make a playlist for these videos,
so it *as a set* can be shared..

Subscribed, upvoted,
& I wish I had the mental-firepower to work directly with this, as you do,
& I wish I could hire you, to help me make my imaginings actualize..
( multiple kinds of aircraft,
arrays-of-each in different scales/sizes,
bushplanes being 1 of those kinds )

Perhaps karma will change,
perhaps not: either way, learning results, right?

Either way,

Salut, Namaste, Kaizen, & Gratitude for your helping us!

_ /\ _

[hu]

Hey Gabe, this was absolutely EXCELLENT! I’ve been watching a lot of flying wing videos of late due to a pending interest in trying out a related blended wing body design, and yours is absolutely the best! (At least for us engineers ;-). I very much look forward to seeing part 2 on stability, as this very much is “the rest of the story”. Thanks so much!

[mtsAlencc]

Very happy I came across this video. Thanks for all the clear explanations.

[mykolakhrystenko]

Thank You for your effort putting all this information in the video! Waiting for the next part!

[veloxsouth]

Excellent video and explanations. I'm looking forward to more on stability.

[soupypunk-pkys]

I’m an undergrad mech student that will minor in aero. I’m doing some research on how to start applying math and physics to real-world projects. Thanks for this video :)

[jayfeaver]

Nice effort on the video! You did a great job of summarizing and presenting. I really hope you keep going and look forward to watching the next ones. 😊

[AerialWaviator]

Fantastic video. Interested seeing more of your design process as you worked through creating and building a flying wing. This looking to be the start of a nice mini-series on aerodynamics and design.

[CarlosChavez-gsld]

Well done, good pace, not for newbies.

[AstroCharlie]

This is an awesome video!
I love the engineering level deep dive on flying wing theory!

[captarmour]

Love this video! Flying wings and close coupled canards get me really excited. When I started playing around with making flying wing foam gliders to test airfoils I found that when I would hand toss a symmetrical tailless wing she would climb hard at high speed and then as she slowed down she would lower her nose and find her trimmed speed. Then I would reshape the LE to give some positive camber and with the same force throw(launch) she would tuck hard until I retrimmed her by moving the cg way back. she would fly almost level at high speed but as she slowed she would gradually nose up into a stall. I got the longest glide with a symmetrical LE and just enough positive TE camber so that she would barely climb with a high speed toss and maintain almost level flight while decelerating before lowering her nose at slow speeds. I think what I'm seeing is the wing wants to follow the camber. I came across a "self incidence wing" which if I remember correctly had only about 1% camber which maintains a somewhat constant AoA over a range of speeds. I think it was a 1410 airfoil.

[TheQuantumFreak]

Excellent work man, took notes on this one.

[nuttyDesignAndFab]

big brain stuff! understood maybe 1/2 of what you said. looking forward to pt 2 :D

[BoonOhm]

Very good video. I need more content like this!!!

[johntenhave]

Great Video with excellent graphic illustrations. I learnt a lot from your excellent presentation. It will take a couple of viewings to understand it all but that is a good thing and refreshingly different from the once over lightly skims that so often come our way. keep up thee good work! Further explanation of how aerodynamic twist works would be very helpful.