Exoskeleton wing design - how carbon fiber makes it possible

[@DarkAeroInc]

Learn how to design and build your own high-quality composite parts and structures! Sign up for the Aerospace Composites Course here: darkaero.com/courses/aerospace-composites Online version available here: darkaero.podia.com/aerospace-composites

[@thegoldenatlas753]

Im curious will yall have a jet engine variant in the future like Sonex has done?

[@ashsmitty2244]

We must be getting close to take off.

[@californiadreamin8423]

Very impressive lecture. When you performed the load testing of the complete wing, even though the wing withstood the load, how do you know if internal damage has occurred ? Do you have inspection hatches/ holes to enable say fibre optic visual inspection, or are there other NDT testing methods available….strain gauges, ultrasound etc… Inevitably the wing will experience stress/strain reversal which in an Al structure will lead to fatigue, do these composite structures delaminate ? How do you plan to verify the structural integrity while in service ?

[@andrewashmore8000]

Brilliant thanks for offering this to the Web. Class.

[@TheClearsky88]

I really like your project and your videos. As a mechanical engineer myself I like your factual, no marketing bullshit approach to your videos and also to your product itself. A breath of fresh air in the "sell pie in the sky" startup world.

[@homomorphic]

Haha, yeah, no battery electric powertrain. I guess the long range requirement killed that in the first 5 seconds of analysis.

[@deldridg]

I would agree. Engineer here too.

[@glennlane6599]

I mean this as a huge compliment. In your next life you would make a fantastic Mechanical Engineering Professor. You have the rare ability to explain complex concepts in an easy to understand presentation. Thank you.

[@cptairwolf]

The methodology you guys practice in researching, building and testing parts is really impressive.

[@causewaykayak]

Yes, this team is a breath of fresh air. Let's hope they do well after all their effort.

[@timgarrett203]

Extremely good and concise presentation of the right way to do wing design! Can’t wait to see her fly!

[@xpeterson]

I was always curious about the solid foam core vs hollow composite wings. Cool to see you guys came up with your own unique solution

[@matthayward7889]

I can’t stop looking at that beautiful carbon fibre 😍 fascinating discussion about why you’ve made the choices you have, and how it benefits the design.

[@Mariano.Bernacki]

I really, really, really like that you guys are product-focused and engineering-centric. That takes care of marketing by itself, as opposed to others "sell impossible performance first, figure out how to make it close-ish enough that you are not sued later" like the Raptor fiasco.

[@andrewashmore8000]

Its very inspiring stuff.

[@daszieher]

I started watching these, because I just love fast and efficient aircraft. However, these videos provide such an in-depth insight into composite manufacturing that my engineering interest now benefits more from it than my passion for flight 😄

[@bwalker4194]

Excellent content and presentation, guys! You all have great skill at not only highly technical processes but also the ability to convey it down to our level without coming across as condescending or droll. Congrats! keep them coming!

[@woutermissiaen4745]

Nice video! I'm curious to see how the fueltank works with so many compartments.

[@Zav]

I think it's essentially gravity drain through interconnected compartments and a large reservoir between the wings to collect before sending to the engine fuel lines.

[@ashsmitty2244]

They act as natural baffles.

[@divyajnana]

I'm with you, would like to see the fuel tank design, seems like you would need a lot more sealant, which would mean more weight.

[@ashsmitty2244]

@@divyajnana More sealant for what?

[@ashsmitty2244]

@@divyajnana Watch their videos from beginning to end and you will then know what you didn’t before. 😉

[@onethousandtwonortheast8848]

I always look forward to your new releases. These videos are great for educating and building confidence in your design. I’ve always wondered however why are you teaching building classes to people who are not necessarily interested in building your aircraft?

[@Jack-ne8vm]

Diversified income, fresh ideas brought up by students, future employees...

[@Michallote]

This channel is a Gem for the engineering community, it doesn't has to be applied on building specifically their aircraft in order to be useful for us. Knowledge is always useful

[@michaelspunich7273]

For the same reason you and I watch their videos

[@SKYHILLMIKE]

Wow, so well explained, detailed and concise. Love the idea that you don’t need mould so you can change the design quick and easily.

[@aaronkaufmann2242]

On the manufacturing topic, could you give us some insight into how the hollow grid is bonded to the skin? Specifically how you can count on that in a tank application.. Love these videos, incredible content. Great job guys!!!

[@JasonKuehn]

Agreed, love the innovative ideas and think this is brilliant for things like control surfaces. But have to admit I am skeptical of that being used as a tank. There is a whole lot of bond area there and if any bit of it fails it will both leak and be inaccessible for repair.

[@NeilStainton]

Kudos. You guys are so professional and so generous with your time in sharing your knowledge and vision. If I was 40 years younger I would beg to work with you.

[@simonbaxter8001]

Fantastic video! Being a traditional aluminium construction kinda guy, this was extremely educational. Looking forward to the next one already.

[@earlgreystoke3324]

Excellent damage tolerant design. Multiple load paths reduce the risk of single point failure. You explain complex engineering principles in a direct, easy to understand manner.

[@doncarlson8391]

Your comment about testing vs simulation is so very true and ultimately important. Simulation is only as good as the data that's entered and all too often what's thought to be complete has omissions. Empirical data from testing will fill in the simulation gaps and keep you and your passengers safe. Thanks for the video and explanation.

[@WPGinfo]

Great content, well structured and presented! Excellent!

[@DarkAeroInc]

“well structured”…I see what you did there ;)

[@javiartbarreda3851]

Looking forward for the test flight!

[@parrotraiser6541]

It's always nice to see machines being built as embedded thought, taking maximum advantage of the properties of the materials. Relates to "Zen and the Art of Motorcycle Maintenance.

[@Datamining101]

This is interesting. Love to know more about the testing and simulation, in particular higher energy dynamics, heating, impact, electricity, etc.

[@Mrsournotes]

Big Burt Rutan fan here. This generation it’s Dark Aero. Nicely done fellas.👍🏽👍🏽

[@deldridg]

Great to be able to come along on your journey. Thank you for the big effort you are putting in to share your story and educate us along the way. Very exciting project! Cheers from Sydney - Dave

[@plmarshall30]

I would love to know if you guys have been surprised by anything you've learned yet while building this very coot plane? Is there anything that you just didn't even think about or is the building and design process calculated to the last detail and you haven't been surprised by anything? Keep up the cool videos, I get excited when I see a new one.

[@DarkAeroInc]

Hi Paul! Thanks for checking out our videos and thanks for the great question. Yes, lots of surprising challenges popped up along the way. A big one was canopy manufacturing, which turned out to be much more involved than expected. We spent too much time on that before we ultimately outsourced the process. We might try to bring it back in-house at some point. Making large honeycomb sandwich panels to meet our own standards turned out to be hard as well. We figured out how to do it at a small scale pretty quickly, but scaling it up was difficult.

[@edog7059]

Designing and building a plane is pretty cool but the materials and structure knowledge your team has developed is even more impressive. Honestly, with your skills, you could probably be designing and building about anything!

[@KiimiKooooo]

Just amazing, thank you so much! I don't recall ever been that captivated for something that technical before

[@JH-tc3yu]

You guys are absolutely killing it

[@roweboatracing2606]

Phenomenal video! I wish I had seen this one year ago before I designed the airfoils structure on our FSAE car. Going to pass this video on to my classmates.

[@nitin8595]

Awesome follow up to the last video on wing design. Loved learning about the thought process behind Hollow Grid, in depth. Great stuff!

[@troygiampietro9570]

Awesome video, great explanation. How are you bonding the ribs/shear webs back to the skin with the distributed spar?

[@Grarder]

This was incredibly well explained and you're a very good speaker! I'd heard of the DarkAero but wasn't really following it, I watched this out of pure engineering curiosity. Definitely interested in hearing more.

[@davidstrong7854]

not sure why Im watching this , but you sure make it interesting to see all you put into it. can't wait to see the final product.

[@vmpgsc]

Great content, love your clean whiteboard sketches.

[@francisunderwood9998]

Love you guys. Because of you I can understand how to make a good design as a erospace engineer student

[@SteelDogFab]

Fascinating. Love your guys work

[@mcanderson0]

your presentation is getting better! Much more prone to keep watching; doesnt feel too slow as some have felt

[@felixcat9318]

Outstanding presentation and narration, clear, concise explanations of technical, engineering and fabrication matters. Subscribed.

[@DarkAeroInc]

Thank you for checking out the video! We appreciate the kind words too. :)

[@benjaminschaefer6757]

Brilliant work and excellent video.

[@terrancestodolka4829]

Wow, Carbon Composite magic... Nice to see you in the future of aircraft being done this way.

[@sardcanada2640]

Very intelligent engineering related to manufacturing simplicity. That was your biggest achievement. Smooth and deliberate presentation of information. I love the hollow grid design, it is more organic and this should be the direction taken psychologically with all engineering and architectural thought processes. Well done gentleman, I will take your course as it sounds like great FUN ! And it may give me new insight to precast, aerated concrete panels inlaid with an organic matrix. Thankyou.

[@janbergendahl]

You guys are amazing! Cant wait to see this fly.. 🙂

[@stanislav770]

Apprendre comment construire son propre avion est bien . Compliments pour le cours très instructif

[@theonlyari]

I really appreciate your hand drawn stuff.

[@SuperYellowsubmarin]

That was a treat. Lately, I too am using carbon fiber (foam cored) sandich panels, CNC cut to manufacture the internal structure of an aircraft. I second that the benefits of that approach being no-tool, large stock, easy design change, are extremely undervalued.

[@LoanwordEggcorn]

Thanks for a very clear explanation. You're an excellent teacher. Definitely want to hear how you're building this. Subscribed.

[@jlunde35]

Love this content. Thank you. I heard about galvanic corrosion problems joining carbon fiber to metal. So many issues. Great job.

[@johnelliott4521]

Great approach to strength weight ratio

[@royvreeland1609]

Absolutely love watching your new videos. Can’t wait to see this thing fly. 🎉❤😊

[@AJ-zj4ml]

Absolutely excellent video. Your methods and design techniques are very impressive.

[@telakos]

Great explanation, I undestood most of it and I'm not an engineer.

[@Humble_Electronic_Musician]

Chances are low that i will build my own airplane (except a small one out of paper) , but i really enjoy your vids. Very informative and a joy to watch. Well done!

[@thebogy]

I love the videos. Would love to get some updates on testing. Like what's the progress, is there rough timeline for first flight, etc.

[@nwbackcountry5327]

I need one. Can't wait to place an order.

[@dittilio]

Damn your white board drawing/writing skills are good. Aesthetics for days.

[@michaelguy7168]

Great information, really enjoy the technical side of design.

[@asteriskman]

Never before appreciated the nuance of an I-beam the way you describe.

[@brighambaker3381]

Fantastic video! Thank you for sharing!

[@Pawe-mx9wc]

Wow this is very interesting, thank you for your educational videos.

[@strugglingengineer1465]

You finally answered my question with this video.

[@air-headedaviator1805]

This is really sick stuff, innovative, different. Interesting thing I noted about y’alls hollow core concept is that something similar is has been used in some 3D printing RC airplane designs too, going as far as to place stingers at angles to the width span of the wings. Its all fascinating

[@EllipsisAircraft]

A similar design is used in fighter jet wings also. One that comes to mind, is the F-104. Where compressed bleed air from the engine was sent outboard through the wing, and emerged from ports precisely located to blow air over the flaps when deployed. "Blown flaps" as they were called, reduced approach speeds significantly as long as the engine was kept spooled up and compressing plenty of bleed air. Losing the engine in this configuration, when landing, was unrecoverable. Such were the 1950s.

[@jbrownson]

Loving these videos, thanks for digging into the engineering

[@martinperry1843]

I like the term "structural divergence", reminds me of SpaceX's term "rapid unscheduled disassembly".

[@FlyingInEurope]

Lovely explanation!

[@compspace]

Can’t wait for the manufacturering video, great video 👍

[@EngineerK]

Thoughts about the very linear stress strain curve of carbon fibre? I am a structural engineer - in seismic engineering we use the non linear section of the stress strain curve (from yield to ultimate) to dissipate seismic energy (hysteresis - ie with steel ultimate strain is ~2.5x yield). This allows us to design for lower seismic force level and we intentionally let the building go non linear to dissipate energy - with the primary intent to prevent collapse (and the building is also not likely useable after a design seismic event). In the high performance sailing world, I think this has been one of the fundamental issues with CF. They are hitting yield loads followed quicly by structural failure because of the lack of a yield plateau (there is no ductilty). Do not know how the aeronautical codes are written but IMO, use of carbon fibre probably needs higher factor of safety in comparison to say aluminum. With CF you basically cannot afford to go past yield...

[@Johnny-Too-Bad]

excellent info and you manage to fit it all on one whiteboard!

[@OliverFlying]

Awesome video once again guys !! Thank you 🙏

[@kirill3754]

Based on my knowledge and hands on experience, the honeycomb core will be saturated with fuel after a while. Primarily due to cyclic ambient pressure change (with altitude). It is impossible to make them perfectly sealed, fuel will go through tiny gaps and stay there. It will add extra dead weight, better to use monolitic webs in the fuel tanks.

[@foesfly3047]

I wondered the same thing.

[@DarkAeroInc]

Hi Kirill! You have highlighted a valid concern! It is definitely possible to create honeycomb sandwich panels that are sealed against liquid/gas leaks. Sealed cells are often the default result for certain panel manufacturing methods, and this can be a problem in certain applications, which is partly why vented honeycombs exist. This is something we were concerned about when we were developing our sandwich panels, and resistance to fuel ingress was a criteria we tested and achieved.

[@kirill3754]

@@DarkAeroInc Great! I wounder if you tested under cycling ambient pressure or just soaking in fuel?

[@daverobinsonTnT]

Love the progress you guys have made over the years I’ve been following your project. Great stuff 👏 Just a couple of questions :- (i) - Have you evaluated fuel flow, migration and fuel bubble criteria for your ‘wet wing’ design ? (ii) - Do you anticipate having to be able to inspect the internal spaces within the wing periodically and if so, does the ‘hollow grid’ construction make provisioning easier or more difficult ? Looking forward to seeing you progress to a successful first flight and beyond 👍 Cheers, dave

[@scott_aero3915]

Another great video!

[@gerrycooper56]

Are there any other commercial or military aircraft that use a hollow grid?

[@michaelstadnikfilm]

Thanks for sharing your work, it's really interesting!

[@jphillips5576]

Another amazing and informative video! 👏👏

[@michaelklepacz]

I love this channel. You’re a bunch of nerds!! Thank you.

[@DarkAeroInc]

🤓 Happy to hear you are enjoying our channel!

[@johnfitzpatrick2469]

G,day Riley, River and Keagan from Sydney Australia. I was wondering how you design structures (aerospace). I knew the components; ribs, spars, struts etc. I now have a idea of testing to resist G force loading. So... one could purchase plans with specified materials or "build and carry out testing to "with a coupon calculations measurement system recognised by the FAA" On the other hand; completely experimental categories. Then there's materials; * Wood, fabric, aluminium, composite material such as fibreglass, carbon fibre in moulds etc. "Speed, just a matter of money, how fast do you want to go?" That was was a great lecture sir, you got my brain to spark on two cylinders. 🍏🇭🇲

[@noonehere1793]

Excellent presentation !

[@MrAerocomposites]

At 6:38 you show the Hollow Grid wing. It is beautiful. I had read some years ago that the primary wing spar structure should be in the traditional location. Having primary load carrying structure closer to the trailing edge of the wing could cause wing structure issues in flight and lead to possible wing failure. Can you comment on that? Thank you.

[@tnk.2033]

Keep doing more educational videos ⚡🙏🏻

[@SoloRenegade]

so, you used a type of Wing Box instead of a traditional wing spar. the construction method is brilliant though, as you say makes design changes much easier.

[@PeakTorque]

Great video, and you are selfless in what you share. Another reason we should be moving away from ribs and spars, is that they are an outdated function. They were needed to take mechanical loads when we had cloth wing skins! Now we have wing skins with serious stiffness/weight properties, we really don't need them so much! Yes theres shear to deal with and face collapse, but i love your design. Be really interested to know how you connect the cell spars to the upper wing skin when you close the structure, how do you know the glue is touching? :) Cheers from UK

[@rschaffer8]

Excellent presentation.

[@lattermd1457]

Fun topic. Would also love to see how the fatigue load test is designed and conducted. - formal aeronautical engineer.

[@nickolayjelev6077]

Nice one guys, what you have achieved so far is brilliant! Keep it up! Quick question: How do you ensure that any ethanol content in the fuel does not attack the sandwich pannel epoxy exposed to fuel in the fuel tank?

[@rcnfo1197]

Thanks for a great overview of your design. How does an all composite structure handle a lightning strike without shattering?

[@jeremyjabaay]

Another good one! Whens the homebuilt engineering class start?

[@gpaull2]

Aircraft have advanced all the way back to fabric again 😎👍

[@kieranshanley7365]

Really awesome explanation of your design approach. One word of caution- by optimising for stiffness and rigidity you may pickup the unintended side effect of uncomfortable ride in turbulence. Pilot friend of mine complains how stiff the carbon fibre spar in his aircraft is and how he gets thrown around in turbulence.

[@CraigVanSickleAK]

Great video guys, keep up the good work.

[@bradley3549]

"Structural Divergence" is suddenly my favorite way of saying the wings broke off.

[@DarkAeroInc]

Add to that “thermal excursion” as a way to say the airplane started on fire.

[@wadesaxton6079]

That’s how Lear jet did their wing in the 60’s. They used that on all models but the 40 &70 series. Rather than a main spar and an aft spar, they went with 8 “spars” and the entire wing is one fuel tank.

[@cougarlove8542]

I am most interested in actual takeoff and landing distance. Looking at the competition VL3, Blackwing they have very short takeoff and landing distance over a 50' obstacle. I need that for sure.

[@rnordquest]

Those planes accomplished that with quite low wing loading. DA has much higher loading and should have a better ride in turbulence.

[@rasgizatulllin1705]

Thank you for your detailed explanation! I have one question: how does your wing structure accomodates torsion? I mean, classical wingbox (the front spar, the rear spar, the skin between) is used for torsion stiffness also. Is the same approach in your structure (the front and the rear spars are stronger than other)?

[@paulslevinsky580]

Love your work. I would think you have a significant gain in torsional stiffness with your hollow mold wing construction because of the multiple closed box sections it creates. I'd be nervous about using any kind of honeycomb core material in a wet wing. A small crack or pinhole will result in tankering unusable fuel.

[@roberttrussell1010]

I really enjoy the videos of your progress. I do understand your reason for your design; however, do you guys think that you might design a slightly slower plane with a lower stall speed in the future? I think it would be awesome if you could use the same format with interchangeable wings to keep your cost down. Just a thought. I'm a new pilot and have no business in a plane with thin wings and a high stall speed. I'm sure a lot of new pilots would agree (or at least should agree) you could hit both sides of the sales. just a thought. I can't wait to see the final product. Good Luck!!

[@generico896]

@DarkAeroInc Genuine question: Wouldn't it be better to distribute the spars keeping equal celular volume instead of equal distance in between spars? On your approach, it seems like the denser and stiffer part of the wing is towards the trailing edge. Was it deliberate?

[@danielvidakovich]

How challenging was it to calculate the stresses on the Hollow Grid design using either manual or computed aided methods?

[@EllipsisAircraft]

Almost certainly easier, assuming You obtain the velocity/pressure distribution over the airfoil at several important angles of attack. It is simpler to integrate loads to multiple shear webs, and wing skin cells, than over an entire wing, flowing to a single spar which is constrained in placement due to thickness, and location of the Aerodynamic center.

[@DanFrederiksen]

You have very satisfying engineering and manufacture discipline. Where you might have opportunities is in simplicity. Have you considered a completely hollow closed shell wing? I believe Elixir does this. Because carbon fiber is stiff, it might hold its shape well enough with little weight penalty if any. And the shear forces transferred diagonally on the shell. And such a design avoids any bonding that could reasonably crack. Any presumably lends itself to fast and reliable manufacture. Cost effective. Similar might be possible for the fuselage although you use a somewhat boxy cross section. but let's say you could do the fuselage as a one piece shell or only one bulkhead for a penalty of only 2kg, it might well be very worth it.

[@Q_Channel1]

I'm curious how you are bonding to the wing skins -- are you using a jig to secure the shear webs for bonding? How are you guaranteeing the quality of the bond fillets between webs and upper and lower skins?