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Comment by ricardobeat | Hacker News Reader

This is quite scary for a non-engineer. You're telling me that this little supersonic plane has the whole wing structure held together by a handful of 4mm thick metal struts, manually glued to the wing surface, with wire pulleys running on the inside :O

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Building a plane in my garage. You'd be surprised how minimal yet how strong a lot of these structures are. The vast majority of the material I use is thinner than a credit card.

I want to hear more about building a plane in one's garage. Are you using a kit? How hard is it? Cost? How will you transport it to an airport once it's finished?

It sounds like it would be a great project.

Thanks.

Kit: Yes, in my case it's an RV-8 by https://www.vansaircraft.com/ they're probably the biggest name in town by volume and they make mid-cost kits. There are some more and less expensive options however.

Hard: I took a class from a licensed A&P mechanic and while not mandatory, gave me a pretty good idea of what I'd be up against. It is extremely challenging even with a kit however. Lots of learning, lots of redoing stuff because of mistakes, many many hours.

Cost: whatever you want it to be really. You can do safe builds probably from around 40-50k for something like a Sonex or Kitfox to several hundred thousand for a Velocity twin or even something turbine powered.

Transport: most people build in their garage and leave the wings off then stick it in a trailer or U-Haul to complete final assembly at a hangar. It's mostly a non-issue.

Kits have become progressively simpler to build. The example like the RV below would conservatively take over 1500 hours. A newer Vans RV-12, much less. A Rans S-21, possibly 600 hours. Looking at their wing build:

https://www.youtube.com/watch?v=iPJgm7qP3FY

dramatically simpler than an RV-8. My -8A flying cost was about $75K a decade ago, it would probably take at least $90K today. An S-21 would probably be more.

Some kits come with a folding wing option, so they can be trailered.

The primary decider in the difficulty/time factor is community and your Technical Counseler [1] (usually a multi-kit builder and FAA approved). If you’re able to build near a very active community (Livermore has a lot of RVs), these people will show up at your house/hangar and get/keep you going. Amazing people who can teach you a lot.

1. https://www.eaa.org/eaa/aircraft-building/volunteer-assistan...

Glue is sort of the wrong word. When you hear glue you maybe imagine the general purpose glue that you can buy, like Elmers glue or Super Glue. This is a chemical adhesive designed specifically for the surfaces that it's holding together (i.e., they will use a different glue for composite-to-metal bonds than metal-to-metal, etc.) and it's very strong.

Many things you wouldn't expect are glued together. Many weld and rivet connections on cars have been replaced with glue in the last few years.

And these bonds can be stronger than the base materials, so that it’s actually least likely to break where you glued it.

Cue the obligatory "Then why don't they build the entire plane out of that glue?"

Various reasons. Chemical bond glues are only strong if there’s something for them to bond to; it’s expensive glue; it’d be much harder to make the entire plane out of that stuff, especially given the desired tolerances; sometimes it has other problems that make it unsuitable, e.g. how it reacts to environmental conditions it’s exposed to; it’d look and sound silly…

I mean, they kind of do. That's what carbon composite is, in a way: thin strands of carbon held together in a mass of resin (glue).

Traditionally in aircraft design, you can't rely on adhesives for primary structural integrity. It's mainly because it's hard to ensure you glued right, it's hard to inspect.

Also we don't like it too much because it's harder to repair.

Adhesives are used, but normally for secondary structure, or as reinforcement to fasteners. So for example you'd ensure that a failure of the adhesive wouldn't lead to catastrophic failure, but it may lead to early cracks that would be detected in regular maintenance.

In the case of Boom they seem to rely more on adhesives than the traditional airframe methods. At the same time they are making a one-off demonstrator here, so they can afford to choose methods that need particular care and inspection, even if it would be unrealistic to expect that level of quality on a real production line.

Yes, glued. Although "structural adhesive" is the preferred term. Race cars and carbon fiber supercars are built this way too, there is decades of experience in this kind of manufacturing for high stress environments.

you should see how most of the internet is glued together :)

//causes obscure network latency issue, fix this later

Last commit, 7 years 6 months ago

Airplanes are very strong, but very delicate. Really amazing works of engineering.

Have you seen that F15 perform a carrier landing with one wing mostly blown off?

https://youtu.be/M359poNjvVA

Carrier?

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