Comment by jillesvangurp | Hacker News Reader

Comment by jillesvangurp | Hacker News Reader

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Cross Laminated Timber (CLT), which I assume this is closely related to, is being used in construction more often now. It's much lighter and stronger than steel, easier to work with, holds up well in a fire because it doesn't go soft and loses structural integrity like steel does. And while wood of course can be burned, the char layer that forms on the outside protects the inside so it actually has some safety properties that buy people time when there is a fire. Also, wood is an excellent insulator.

Laminated timber is also very construction-friendly. It can be worked with simple tools, and CNC machines allow for prefab components to be shipped to the site and assembled quickly with minimal fuss.

There are some plans for high rise construction with this material. E.g. there is a plan for a skyscraper in Tokyo (350 meters, 70 floors).

The adhesives used in laminated timber aren’t perfect. They’re very durable, which is great for structural integrity. But it also means the material breaks down more slowly in a landfill (if you decide not to recycle the material for some reason). However, newer adhesives used for this these days are less toxic and not that harmful in a landfill. And importantly, most of the material is actually just wood, not glue.

(I know nothing about this)

Is it possible to make smaller scale CLT, with thinner boards or something, and build like cars or airplanes out of it?

Early cars and planes were made out of wood. So, I see no reason why not. The mosquitto which was one of the most successful planes in WW II was made out of plywood, which you could think of as an early form of CLT.

A lot of modern cars are made with a lot of composite materials that probably have better properties. But I imagine CLT could work well for things that are currently made out of steel or aluminium on such cars. I'm not sure if there's a big advantage to doing that in terms of strength, weight, or durability though. Aluminium might be lighter. And composite materials provide better strength and weight.

CLT is in no way similar to the product InventWood is working on, besides that it uses the same base material, and I guess requiring some pressing. You can think of CLT as being like plywood, but for beams instead of for sheets.

That said, CLT has 2 major advantages over regular wood:

1. It is more dimensionally stable, it expands/contracts less and in a more uniform way.

2. It is cheaper at larger dimensions. I.e. 0.5m x 0.5m x 20m wooden beams would take decades to grow and even then not realiably, but you can just manufacture CLT beams with those dimensions easily out of <10yr old trees.

Those two advantages are not limiting factors for the construction of cars or airplanes, so CLT is not super relevant to them.

Dimensional stability isn't irrelevant to planes. Thermal cycling is inevitable when going from the ground to cruising altitude and back.

Certainly would be better to laminate IF you're using wood. But it's still got a long road ahead.

Aluminum still has a higher strength/weight ratio which is everything in aero. Also, I'm not finding any information on cyclic strain behavior. Dimensional stability is only part of that.

Edit: There could be room for this in experimental aircraft. Once we tease out all the failure modes and properly characterize cyclic behaviorof course.

RIGA chair factory tour >> https://youtu.be/IndP2IKXTP0

Make CLT from thin enough boards and you got plywood

Aircraft grade plywood is still a thing. Often used for model aircraft, but you can make small planes from it.

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