Yeah, I work in R&D, I know about ‘thinking outside the box’ it’s what managers say when a ridiculous idea won’t be let go when it has been shown to be bad, commonly known as ‘ugly baby syndrome’.
Obviously Boeing has found something and the math works making the shape possible.
"Thinking outside the box" is what I hear when a stupid idea needs to be delivered against an absurd schedule at no cost. It seems Fred and I worked in similar companies.
Kevlar does a pretty good job at stopping bullets at a pretty light weight. Before that it was steel plates (The Good, The Bad and The Ugly).
Kevlar works because the structure and concept is fundamentally different. A solid piece of Kevlar would not stop bullets. But kevlar uses many layers with other materials in between and this layering concept is much more effective than the concept of using a strong solid material.
Okay so it’s impossible to know but you would think Boeing would be able to do the FEA work to figure it out. Computers aren’t getting slower and you can iterate faster and faster.
Anyone who claims that FEA can solve all problems obviously does not understand this technology. FEA is extremely complex and can evaluate the design which goes in, but not create designs. In it is highly dependent on the skill of the modeller and the assumptions which go in. I have seen many FEA simulations which are beautifully looking pictures full of nonsense. For a good example of how FEA can proof nonsense, look for the academic paper on MH370 and the theory why no wreckage could be found. FEA showed that under the right angle the plane could dive into the ocean at high speed and the wing would shear up but fuselage stay intact and dive like a submarine and end up resting as 1 piece at the bottom of the sea.
It’s not an impossible problem and even at a 50% weight penalty Per M a Carbon 7W tube shouldn’t be any heavier than an 6W Aluminum tube which destroys the weight argument at lest in competition to an A322. Even if it’s a little more it appears the fuselage is only about 5% of the MTOW (at least on the A320). I would guess the percentage falls on a longer range airplane as they are bigger winged/heavier engines/more fuel.
I have seen a presentation by Hexcel at an aerospace conference that carbon has 3 problems for smaller planes:
1) The benefit is non-linear: as it scales up, it becomes more efficient. For a wide body, the weight benefits are significant but for a small aircraft less so. It also depends on the complexity of the structure, so wings are easier to justify than for simple structures.
2) Related to that, it takes longer to manufacture but that also depends on structure complexity. For a fuselage, they estimated maximum build rate for a full carbon narrow body fuselage is around 20 to 25 per month.
3) Cost, cost cost. Carbon costs about 10x Al per kg. You don't get even close to 10x weight saving.
And why does everyone talk about Carbon: this is old stuff. The real advances right now are 3D printing of metal parts. It is starting with brackets. Small savings per part, but with the number in an aircraft it adds up. Examples are injectors in the new GE9X and Airbus using brackets. This works because the part can be designed without the limitation of traditional machining manufacturing limitations.
I read already for more than 5 years that NMA is the new magic solution which is going to crush all competition. But Boeing still does not launch because they can't make the business case. And that is because this business is mature, highly advanced and highly competitive. There are no simple solutions. Look at Embrear with the E2. The "no brainer" solution of adding GTF is not selling. I even has magic new carbon wing. Still not selling. CSeries. Fantastic design but R&D killed the company and Airbus is investing a fortune to bring production cost down by at least 25% to make it sellable.
This business is very difficult and there are no easy solutions.
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