Torsion Box Info

[mezmo]

Just came across these and thought they might be helpful:

RE: Torsion Boxes
http://www.core77.com/blog/furniture_de ... _26334.asp
http://www.finewoodworking.com/woodwork ... table.aspx

[GPW]

Nice table !!! Especially if you plan on dancing on top ... Foam core would do basically the same thing as the egg crate ...

[Mary C]

Sometimes my thinking goes bananas, wonder if: You made one with two inch foam inside in sorta close 5x5 or 4x4 and made the top with foam covered in canvas and probably make a bottom too covered in canvas and painted, wonder how that would work for a platform for building a light weight TD, make the box and strap to frame............ just thinking .......I told y'all thinking gets me into trouble. Now I wonder if making a boat hull like that would work? Oh just think of the possibilities..........I'm in trouble............just thinking Now I know another reason for my being crazy enough to build with foam. I may be old and I just believe not all new stuff is bad... There I go again I believe I could increase the floatation by building a modified hull with the idea.............if it works for a wing in some curved aspect .............I can see I am in trouble............ I know everyone thinks I am crazy...I just see things differently!!!

Mary C.

[Epbowen]

Boat hull....isn't that what those unsinkable boats are? Boston whaler....

[angib]

It's a fair rule of thumb that any time anyone mentions 'torsion box construction', what follows is at best ill-informed and at worst complete rubbish. Those articles seem to be in the ill-informed category so I guess that's better than average!

Better tables could be made with much less work by running the internal stiffeners in the short direction only (which is what airplane wings do). But that would be good structural design and that's not required if you mention the magic words 'torsion box'.

Personally, I find saying 'abracadabra' generates all the magic I need, and I do sell a lot of snake oil.........

[Epbowen]

Seams to me planes have ribs that run along the chord too. ( been along time since I played with aeronautics so forgive me if my nomenclature is off)

[VijayGupta]

From what I remember of Ian Kirby's articles (+25 years ago) on torsion boxes the strength derives from two things:
- Shear strength of glue bond of the the skin against the grid
- Beam strength proportional to the cube of the beam height (doubling the beam height -> eight times the strength/stiffness)

Marc's method seems a little off the ordinary. Kirby suggested just stapling the joints on the grid. Once assembled, the grid items are not going anywhere. I'd also think that running the continuous beams the long direction would be stronger than running them the short direction.