Most complicated CARBON FIBER part in the DarkAero 1!
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- Опубліковано 8 жов 2021
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We just finished building a carbon fiber part called the trunnion frame. This structural component transfers loads from the landing gear into the rest of the airframe. It was made on a male mold using a manufacturing process called infusion. The mold for this part was a bit different than our standard molds. Normally we CNC cut a mold pattern from tooling board and then use the mold pattern to create a final mold. The trunnion frame mold was instead directly CNC cut from an assembly of MDF stock.
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I've moved on from my dream of building and flying one of these beautiful creations, mainly on account of very low SAF (spousal approval factor) and the differing ideologies between my better half and myself. As a minimalist, I love this. It's fast, efficient, likely small and light enough that liability-only insurance won't break the bank. It's the kinda plane that makes you think about where you want to go, and not about how much getting there is gonna cost. I wish you all the best and hope to see some of these flying into Oshkosh in future years as I sit there pondering my life choices.
I really appreciate the time and effort you're putting into making these videos, especially when you're already putting so much into the project itself. It has been fascinating to watch.
Thank you following along! The videos are fun for us since they allow for a bit more freedom and expression compared to the more strict engineering and manufacturing tasks.
I assume it gives them some "free" marketing, while in turn giving us free knowledge. Win-win.
@@DarkAeroInc what is the size of the sleeve carbon fiber for the prop spinner?
Where do you buy it from?
I do almost this exact same process for my 4meter F5/3J sailplane wing molds. Super in expensive way to get a decent mold for ~50 or less pulls.
I vacuum bag the layers of MDF to a huge granite surface plate to keep everything flat and have no voids in the laminations.
Also - always do my finish pass with a 2 flute Harvey ball end mill
Excellent work and great project!!!
What I wouldn't give for a large calibrated granite slab.... I did notice that (it appears as if) they didn't use anything to thicken the epoxy when they glued up the MDF. That might have helped but I think the mold looked pretty darn good less some small voids. I think that if they took the time to Gelcoat and polish that mold they would get > 200 pulls from it and much better cosmetic finish. The little bit of carbon stuff I do is structural for sailboats, so cosmetics is never a factor, we always paint everything anyway.
I built a series of fairly large MDF molds for the manufacture of product I was involved in. The parts were made from vacuum formed HIPS (high impact polystyrene), so the molds saw more abuse in the form of thermal cycles and "clamping" from contraction during cooling. I was able to get 1200 cycles from the MDF by combining the use of clear maple or aluminum in high stress areas and performing periodic maintenance. They performed way beyond our expectations.
That mold is beautiful... I couldn't stop thinking I would love to have a topo rendering of my ranch made like that!
Dark Aero posted! I imagine there is a bit of anxiety when you have that much time and materials into a part. Thanks for your excellent efforts!
This part wasn’t too bad but we definitely have had some high stakes parts. The lower wing skin is one in particular that we always want to get right on the first try. It’s nearly 24 feet long so it would be a lot of expensive material to throw away if the infusion didn’t go right. Thank you for watching!
Great job! Thanks for telling us how many hours it took @4:12. Sometimes we watch a 10-minute UA-cam video and forget that a part like that can take days or weeks to create - and that's not even the final production mold. Keep up the great work!
Awesome! I just love to see the making of molds, molding and then release! 😀 You guys rock! 🤙🏻
I was wondering how epoxy was going to be applied when I saw the vacuum bag fitted.
Infusion worked brilliantly - what a great labour saving technique.
And so much cleaner and qualitative.
Infusion is a great process! Really clean and controlled once you get it dialed in.
They do make 'weatherproof' MDF. When it first came out, I grabbed a sample block and left it in a water bucket for a week. Expanded less than a 1/16th" (about 1 mm) and wasn't compromised structurally at all.
I am amazed how much motivation you guys have I have been following you for over a year and see you guys love what you do and you certainly do not do it for the money. As an experimental aircraft builder thank you for taking the time to share the brothers talents with us. I can’t wait for the next video even if I takes you 2 to 3 weeks to actually make a real progress on your built.
Frank, we appreciate the kind words and for following along! It means a lot to receive these types of comments! Hopefully we can get the next video out soon!
So amazing to watch guys! Gonna be one sweet airplane!
All right guys, I gotta tell ya, with each new video, I say dang that is a great video. How are they going to top that one. But never fear, the next one is as interesting and entertaining or more than the previous one. Really appreciate you sharing your journey with us!!!
Such a cool build excited to see it fly and curious how it performs as well!! Keep it up
These videos are gonna be hella cool in 10 years when y’all are a huge successful company with multiple models looking back
Can you guys please do a video on project management and how you stay organized in the development of dark aero?
As well as a video on the detailed design process of the aircraft
Enjoy the updates. It's always a treat when I see a new video is out.
I like videos like this because they kind of demystify CFRP. It's surprisingly simple.
Kristoffer, that's correct! It all comes down to documentation, understanding your variables, and following a process. Thanks for watching!
Very impressive part. Thanks for showing the entire process and sharing your results and Congrats on a successful pull the first try...that is a good feeling indeed!
Thanks for watching and for the kind words! :)
Amazing work in as usual, cant wait to own one of these one day
Hi, very impressed with your work, I can’t keep from wondering however how your business model works. You have been building for a couple of years now with three brothers, you probably have families to support, while burning through heaps of cash for materials, tools and bought-in parts. How many aircraft are you looking to produce per year to break even?
That was one nice looking part... Keep up the great work guys 👍🧡
Hitting it with a ring at 4:14 made my heart stop for a while :) I stopped wearing any jewelry when I was working with composites
Vadim, thanks for watching! Keegan just got married in September so he's still getting use to the ring! :)
@@DarkAeroInc Should tell him to leave it at home, the shop is no place for jewelry!
Also I wonder if you guys have/will do a video on how you used structures analysis to come up with a layup schedule for your parts
This is a pretty involved topic but we’ve been thinking through how to boil it down into a shorter overview for a video. It’s a topic that comes up a lot so it would be a good discussion!
Trunnion Frame Landing Gear Mount... I love the geometry that's being worked out for real-world application design for takeoff and landing configuration, then clean transition of mains landing gear retracting into the fuselage... Stellar sophisticated key part integrated into DarkAero's 1 airframe... I appreciate the time spent to deal with complicated load factors to a geometric formed part that weighs about four pounds.. Very nice packaging guys! I love spending time with your channel!
Thanks Will!
Amazing watching you guys work. So impressed. I’m finishing up a velocity xl rg and can appreciate all the time and steps you are taking to build this plane. Awesome, just awesome!
Hi Michael! Velocity makes a great kit! It definitely is hard to communicate fully the effort involved in building an airplane so we appreciate your appreciation. ;)
I went there about a month or 2 ago and did the tour with my dad for his birthday! I probably saw your plane! they make a great product and something I aspire to build with my pops one day.
Fabulous work as usual
That is really impressive piece of engineering right here) Nicely done!
Hey Riley, just trying to wrap my head around the structural integrity of that part since its supports the main landing gear. Its pretty thin and not real ridged in nature. I don't see or understand the whole engineering frame work around that area and the gear. You really want that area to be the 'beefiest' part of the landing gear system, especially for the mains. As you said, on this type of retractable gear, it's usually found under the wings.
Keep up the good work and I cant' wait to see the finished product. You guys rock!
Hey David! There are a few more parts that will be bonded to the trunnion frame to create the full main gear support structure. The complete structure functions like a box beam connecting the two gear struts and it is bonded to several other bulkheads in the fuselage. The part we showed in the video is just part of the upper flange in that beam. The bottom of the beam is formed by the lower fuselage skin. More will be shown on this in future videos so my apologies if the brief explanation in this video caused any confusion. Thank you for continuing to follow the project!
Great video guys, nice to see part construction from start to finish!
Thank you! We enjoy sharing the process!
Thanks for another fantastic video, terrific editing to show a long process quickly. How do you guys all manage to get along so well without fighting? 😊 Is there a "Dark Aero- the DARK moments behind the scenes" video coming out ?
Glad you enjoy the videos! Oh boy, DarkAero DARK moments would be an interesting behind the scenes video! 😬😂 It helps that there are three of us since the third man can break the tie when there is a disagreement between the other two.
Excellent build! I would be ogling the weight and balance scales once you all have the landing gear in place with the wing attached to the fuselage. Hopefully, your upcoming video might hint on this. Hopefully, after successful launch you all remain in the R&D of aircraft, so awesome to see the amount of heart you all are putting into this aircraft.
You are doing great. Your videos always bring very important tips and concepts for everyone to learn. Excellent !!!
Great video. I have made molds out of MDF and have found that soaking the surface with polyurethane after the roughing cut and before the finish cut helps make a stronger mold.
There is a product sold as "carving foam" that is generally used for this purpose. Sold by sign suppliers. MDF is a tough sell. Why mdf is cheap if also will let a vacuum flow through it. You have sealed it but it can still see pinholes in production.
The material you are describing sounds similar to what we normally use to make patterns for our production molds. We were hoping we trash talked MDF enough that people would try to avoid it! 😂
@@DarkAeroInc I would seal the back and sides of the mdf while you have a chance. Spray varnish is generally good enough.
Awesome video! And awesome project! Great job
Nice work. Thanks for letting us look over your shoulder as you work.
Have you considered using compressed air to aid unmoulding? I've used it with fiberglass, to good effect. A disc of aluminum foil bridges the opening while infusing the part to avoid surface printing.
I love this channel. I love the project. I love the enthusiasm. I love the intelligent approach. I love aviation.
Thank you for following along! It means a lot to us!
a good way to make a quick part with a nice surface and zero mould prep/release is to bag a layer of vacuum bag down over the mould, lay up over that then bag as per usual. saves a ton of time for a one off.
Just a thing I will add about mdf molds. Lots of guys I'm the rc space do this and they get it a few thousandths above the final part then coat the whole part in resin then carefully use a heat gun th soak into the mdf. Then rerun the whole part to final thickness. The resin should have soaked into the mold and you can then run the program and be cutting through an fairly durable resin and mdf mix. Hope that makes sense!
That would work as well! There are a lot of options when making quick prototype molds like these. 🤙🏼
Being an A&P IA I really do not have all that much experience with carbon fiber however, I have worked around it before with others aircraft. I really appreciate that younger generation is picking up the mantle and experimenting like you three brothers are doing. I'm at KRFD not too far from you so thank you and I really cannot wait to see your plane fly if it isn't already.
Have you dealt with the E1000?
yes, looks great
Have you considered doing a pass with negative axial stock to leave, doing your coat of epoxy (or two) then a finish pass with 0 stock to leave? You might be able to go straight to mold release and pull your part and avoid sanding time. More machine time, but less you time. :). Great work regardless!
We have experimented with something like that using low density tooling board, but not with MDF. In the end, sanding is still required to remove scallops generated by the cutting tool. Agreed that it's typically better to try to offload effort to the machine! 😁
Great job guys!
had an idea for parts like that with large flat areas, you could create a wave type pattern to strengthen the flat areas. thinking about curved surface being stronger than a flat one. if you could have a small scale pattern that is always curving could add a lot of stiffness if needed. basically like a truss made of a continuous curving surface. like a triangulated pattern of peaks and valleys curving into each other.
One way to save time and effort is instead of finishing the tool with epoxy and mold release is to vacuum bag the tool and do your layup over the bag. Did this many times and was able to go from a finished (machining) tool to a curing layup in less than a day.
Wrinkles in the bag?
Have you considered tooling paste as a mould finish? Or high density EPS mould core + Tooling paste finish?
Construct mould > Rough CNC pass (+- 1/8 inch below surface) > put on paste > fine CNC pass.
A step slightly above a pure MDF mould, still economical, but you get a fully homogeneous mould surface instead of the MDF quirks.
Always interesting...great video!
Good job fellas! Keep it up!
Wow! I've been looking for information on this exact process.
I wonder how it would work, to CNC the MDF slightly undersize,0.05" or so, then lay up several layers of fiberglass and micro, followed by a finish machining to final dimensions. It would potentially improve the molds dimensional stability, and could allow it be used to make additional parts. Say, for limited production runs of 3-30 items.
Really nice work 👍 !!
Thank you and thanks for watching!
You may have addressed this in another episode, if so, my apologies for missing it. Will the DarkAero have a ballistic parachute system, or at minimum, a design allowing this system to be an option or added later without major modifications? Thank you! You guys are awesome! I thoroughly enjoy your channel!
Great question, BRS is vey importan feature nowadays, no matter how the old timers hate it.
perfect I can't wait for the project to be ready
First of all thanks for the video! It show‘s that we‘re pretty much dealing with the same issues!
We‘re in the process of developping a UAV in full composite and starting the first prototype tools/parts. First molds were made out of MDF but it‘s pretty much the worst „wood“ Material you can find! But how ever these test molds were not that bad for our first parts.
Now my questions is (as we didn‘t make it the exact same way), how do you mill the MDF in terms of finish dimensions and what is the layer of Epoxy you apply?
Thanks in advance guys and thanks for sharing all your experience!
Extremely exciting stuff !
Tip for you guys. Throw a Household Heater Blanket over your curing parts. Also use a blast of Compressed air to release the part from the mold.
Man, your work is amazing, feels like an art.
The plane is going to be sexy, can't wait for the maiden flight! I'll keep my fingers crossed!
Greetings from Germany
Thank you! We are excited for first flight as well! ✈️
@@DarkAeroInc do you have any estimates as to when it will be? I was hoping for some time in the first half of the next year?
Mannnn!!!!! I love the info you guys share and the technology you are using to bring your dreams to reality..... Hopefully I will be in a place to be one of the first in line to buy one. #ENJOYYOURJOURNEY
There are already a couple of hundred of us that have placed deposits!
I was just saying to the Mrs that the Dark Aero team hasn’t posted in a while.
And today I wake up and BAM!
Happy days.
In future, could you design a mold with vacuum hold down, tram in the mold on the cnc and then run a path to cut the part precisely?
Why don't you use extruded polystyrene glued with epoxy, it's much lighter and easier to process, but can be a little bit messy with residuals from routing
Hey Konstantin, thanks for watching and for the question. We have machined a few simple "molds" using extruded polystyrene. A good example is when we completed the wing load testing. We machined out several sections to match the profile of the wing to act as a flat surface to stack weights onto. It works decent for larger shapes not requiring high degrees of detail or dimensional accuracy. Several challenges with it include accurate work holding, keeping it from tearing across glued sections, and holding detailed features for defining things like the edge of the part.
Damn, you make it look so easy, congrats.
Thanks Ash!
Well done!
That’s a really nice part - and a great demonstration of the process!
One really important note - you bagged over the MDF block and down to your table. It is really hard to get a good air-tight surface on MDF so bagging onto the mold rarely works well. Just something somebody doing this would need to know but that might not be obvious if you aren’t looking.
And I love those long skinny demolding wedges - perfect for carbon! Did you make or are they a product?
That’s a good point and it’s something we failed to mention in the video. For all the MDF molds we’ve made, we either vacuum bag to a metal backing plate or we completely vacuum bag around the mold since it is difficult to seal directly to the MDF. The wedges are just door framing shims. They are some sort of composite plastic and are nice and soft so they don’t scratch the part or the mold.
@@DarkAeroInc also mdf isnt air tight at all, especially at this scale. So one spot where you cant through the epoxy and you need to have the vacuum pump running through the night
Great videos guys. I enjoy watching you sharing the details of the manufacturing process. I have a couple of questions one from structural integrity of such a complex part and manufacturing as well. How do you guys validate the structural integrity of the part making sure it will withstand the flight/ landing loads. The bend radiuses specially at the corners where 3 planes converge look some how sharp. I always was told that for aerospace composite structures, we have to use gentle radiuses at corners, to relax stresses and avoid delamination. Also how do you ensure the angular deviation is respected at the corners and bend radiuses, so the mechanical properties of the layup remain hopefully as per analysis.
Do you have any videos discussing the hardpoints and mounting solutions from the bulkhead to the engine frame?
Very good work for mdf ! What kind of releas agent you use after epoxy ?
Hi could you please brief on analysis of carbon fiber parts you make.
Software and process
Looking good boys
Excellent job.
Thanks Ervin!
you guys are doing some great stuff, is there any way to support what you’re doing
Hey Jack, thanks for following the project! Just watching and following along is cool by us, but you are welcome to support us further by becoming a channel member here: ua-cam.com/users/darkaeroincjoin, otherwise we have some great DarkAero clothing options available here as well: darkaero.myshopify.com/
I appreciate all the hard work you put into these fun videos. I am working on composites with a formula student team in the US and I work a lot with wet and prepreg layups but I learned a lot about vartm from you guys. I was wondering if you placed the breather underneath the flow mesh? I thought we did not have to use breather since the mesh itself makes the way for vacuum. Also, what is the X shaped material you use on top of the mesh that you connect it to the infusion line ?
I’d really like to see a lot less paint on the final airplane. I don’t know how the CF reacts to the UV but I’d like to see the carbon and maybe a small red and white pin stripe design.
Use your router to cut up your MDF sheets into the sizes needed. Straight and square pieces will assemble better and eliminate most of the voids in your mold blank. The time invested up front saves a bunch at the end and produces a better result. I know it's a test part & mold. I still think its a worth it.
I can really reccomend pore sealer for mdf, its kinda similar to epoxy in the way you apply it (with a brush) but its dry in like 15min. After that hit it with a rough scotchpad and theres no need to sand it, youll need a fraction of the time.
Ofc finish wont be as polished as the final part should look like, but doesnt really matter for a prototype, does it?
I keep getting this type of finish as well. Im going to try to sand my mold down with 2000 grit sand paper and polish it better. Do you think this will get me a more glossy finish? Is it worth it or should I just apply a coat of resin/clear coat after to accomplish the glossy wet look?
Have you considered the change in CG when the gear is lowered/raised?
Yes. There is a CG shift when the gear is raised and lowered. This is accounted for in the CG limits so it doesn’t get too tail heavy when the gear are retracted.
Very nice work! I have a love-hate relationship with MDF for mould making.. when applying epoxy for the first time, the fibers of the wood stand up and need to be sanded, most times i have to apply a 2nd coat then. For improved surface finish, you could have easily applied another spray layer of epoxy to get quite a perfect finish. Anyway, nice work! One thing i noticed though: on 5:25 on the right corner there seems to be two larger gaps in the mould.. no fear of the resin sticking in there?
Thank you! Our relationship with MDF is exclusively hate-hate. 😂 Agreed that further iterations of epoxy coating and sanding can be utilized to improve the mold surface finish. You might be seeing gaps that were filled with epoxy but they still look open since the epoxy shows up darker than the surrounding material.
According to the engine manual max in flight OAT is 90F. That eliminates a lot of low level flights in the summer down south. Don't think you'll escape up north either. Min OAT is -15F. This is easily reached when climbing above the clouds on a cold day. What's the plan?
Great Craftmanship,,lot of work making that Part ,,,,Remember Aviation Rules: keep it Simple
Good work guys 👍👍
very cool! quick question: why not going back to cnc after epoxy coating? i know the finish is not a problem in this part, but would it be possible to laminate some epoxy for sealing and then go back to cnc to finish the epoxy?
Yes so to cut the trims and such? That's be a great idea, save the customer from breathing carbon.
Excellent video. How do you compensate for thermal expansions? Do you change your mold geometry according to the thermal expansions expected?
Super interesting as always. We work in similar worlds and I've used this type of mould many times. Even used it with low temp prepreg. You could also check out Valchromat. It's a nice version of MDF, might be better than the MFD you have?
Can you kindly tell me what you are sealing and releasing with? Do you think it is better than using Teflon coated fabric? Cut at 45 degrees it would cover most of that mould.
Hey guys, try bondo thinned with polyester resin (syrup consistency) instead of epoxy. Also, look into Ren Shape and K36 primer.
Do you post cure your parts? Great vids and plane !!
Thumb up on the presentation. Noticed that no tooling gel coat is used on the mold. Is the mold be as good as with with tooling gel coat? May be the tooling gel give better finish?
Exciting 😮
Flying by this coming Air Venture perhaps ?????
Hopefully sooner than that so we can get it tested enough to fly it into the show! 😁
Hi, cool video with many tech infos as always. I was wondering why you did not plan lightening holes instead of lets say normal holes? From static points of view lightening holes more state of the art. But I guess you know that and wanted to keep the mould simple. Nice work anyway.
nice. very impressive.
Is there any particular reason you didn't epoxy coat the MDF before running your finish pass? Seems like that would give a more accurate mold. I have been using a similar process for hydrofoils.
Very cool.
Did you publish the layup schedule and fiber orientation?
We have kept the layup schedules proprietary.
Good work for low budget
There are moisture resistant grades of MDF which may help..
Just in case this is not on your radar; there is a MDF product out there with solid colour through out and moisture resistant. You don't need the solid color bit - but it is a much higher quality product. Naturally very few folks stock it (it can be special ordered). I learned about it from two youtube channels: Peter Millard in the UK and Hooked on Wood in the Neatherlands.
Did I mention it was not cheap? :^) But in this case I think you get what you pay for. There are several brands out there to choose from.
Ronald, thank you for checking out the video! Thank you for mentioning this, but we had come across moisture resistant MDF several months back - very interesting stuff! However, given its more of a special order product and higher priced, we would likely just opt for tooling board at that point. One of the goals of this part was to keep things moving without any downtime waiting for materials.
I haven't done it myself; but I've heard of people having good results soaking epoxy into mdf molds before doing a final shallow finishing cut. As opposed to putting it on after you've finished machining. Have you guys experimented with that?
Kohen, thank you for watching and for the question! There are a lot different approaches you can take to mold making especially when it comes to going the experimental route with MDF. :) We did consider the approach you're suggesting, but we didn't see that as having a significant advantage as you would still need to sand it after machining to remove tooling marks. Another concern we had with that approach is that if we weren't consistent with how we applied the epoxy, it could soak unevenly, potentially exposing the raw MDF after the finishing pass. However, this could be something we experiment with for a future part!
@@DarkAeroInc Ah yeah fair enough. Yeah I had heard it can give you a better finish but as I said never tried it. I think they used a heat gun to warm the mdf and the epoxy as they go to get it to penetrate further. But it's one of those techniques that might not be worth the extra fidling once all is said and done. Thanks for sharing your work with us good luck with the project!
You guys have got to be close to getting this thing tested and in the air after this part....
Correct! Getting closer now. This component was one of the more trickier ones standing in our way.
Congratulation DarkAero Team! I would like make you a question, what kind of material (brown color )is do you useing to cover de mold? Thank you. Saludos desde Paraná - Argentina
Too smooth the part out better for a more finished look why did you not use bondi to finish your mold surface. ?