Geodesic Airframes
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As Mike has noted, a compound curve is quite strong. The geodesic is an amalgam of strong linear shapes, the triangle being the most elegant. There are two considerations in three dimensions, compression and tension. A cylinder (fuselage) has terrible compressive strength, marginally better tension. The strongest three dimensional fuselage (section) would be the triangle, basically three trusses fastened on edges. This shape would be strong in bearing, tension, and in torsion (twisting). To gain volume (but lose strength) the "Tube" is born.
The modern aircraft is robust, and impossibly weak, depending on the stresses, and weight.
I am no engineer, so you know, my background has been in design and fabrication. I still am unsure what you want to accomplish with Fullerine dogma v/v a/c. ??
The modern aircraft is robust, and impossibly weak, depending on the stresses, and weight.
I am no engineer, so you know, my background has been in design and fabrication. I still am unsure what you want to accomplish with Fullerine dogma v/v a/c. ??
Joined: Jan 2006
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From: Dorking
BearF.
Understand what you're saying,but I'm having difficulty with this 2d/3d thing.
As I see it, the least number of finite elements needed to construct a 3d shape would be 6 - in the form of a 'triangular' pyramid.
From there, an Infinite number of elements can describe anything. So put enough 2d shapes together and you get a bumpy 3d. The more you add the smoother the surface.
The thing I'm stuck on is where you say that a tube is better in tension than compression. Hilberts' Regression suggests otherwise, or have I got that wrong?
Understand what you're saying,but I'm having difficulty with this 2d/3d thing.
As I see it, the least number of finite elements needed to construct a 3d shape would be 6 - in the form of a 'triangular' pyramid.
From there, an Infinite number of elements can describe anything. So put enough 2d shapes together and you get a bumpy 3d. The more you add the smoother the surface.
The thing I'm stuck on is where you say that a tube is better in tension than compression. Hilberts' Regression suggests otherwise, or have I got that wrong?
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boguing
bear with me, I am utilizing the "tube" as a fuselage, eg. frames, stringers, skin.
Suspended in space from either end, my visual and intuitive opinion is that it will resist "rupture" (separation) underneath, and foster "crumpling" (accordion), above. This of course requires 'loading', (eg 1G), so I haven't a clue as to the contribution of the existing stress.
Seen as: Tension, resistance to rupture, and Compression, resistance to wrinkling.
bear with me, I am utilizing the "tube" as a fuselage, eg. frames, stringers, skin.
Suspended in space from either end, my visual and intuitive opinion is that it will resist "rupture" (separation) underneath, and foster "crumpling" (accordion), above. This of course requires 'loading', (eg 1G), so I haven't a clue as to the contribution of the existing stress.
Seen as: Tension, resistance to rupture, and Compression, resistance to wrinkling.
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From: Dorking
I'm with you on the tube thing completely.
So, taking two tubes, one plain vanilla ring frames and longitudinal stringers, the other Geode(s/t)ic and both hung vertically from an end, you seem to imply that the geo structure will (under identical Gravitational constants) undergo less stress than the former. When Hilbert is applied to the resultant strain, I think that the strains would be equal. Or am I missing something? As usual...
So, taking two tubes, one plain vanilla ring frames and longitudinal stringers, the other Geode(s/t)ic and both hung vertically from an end, you seem to imply that the geo structure will (under identical Gravitational constants) undergo less stress than the former. When Hilbert is applied to the resultant strain, I think that the strains would be equal. Or am I missing something? As usual...
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I think it is I who am missing something. Given equal weight, and suspended vertically from an end, the strain is equal. An engineer (amicus?) would have to input here, for stress is only a factor insofar as it is spread, yes? If I had a choice of material but was limited in mass, and was free to design the tube, I would select a composite, for intrinsic in the shape is the inclusion of geo- stringer, skin- etc. Incorporating the frame with the consolidating skin gives strength and weight saving. Strength (Stress) is always best when distributed, rather than focal??
edit. Did you see that I proposed suspending the "tube" from "both" ends, to simulate dynamic load?
And, if not for drag, perhaps a helix !!
edit. Did you see that I proposed suspending the "tube" from "both" ends, to simulate dynamic load?
And, if not for drag, perhaps a helix !!
Last edited by bearfoil; 20th March 2011 at 01:08.
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From: Cardiff UK
It is interesting that the the original definition of "geodesic" is related to "geodesy" which is concerned with methods of defining the shape and size of the earth. In fact "geodesic" is a part of a great circle, therefore a great circle route could also be descibed as a geodesic route.
As I understand it the first geodesic structure was a planetarium for the Carl Zeiss co designed by Wather Bauersfeld just after the end of the first world war.
Geodesic structures are used by architects and structural engineers to enclose any curved space. An example would be the geodesic sphere that forms Spaceship Earth at Walt Disney world.
As mentioned earlier an American engineer called Buckminster Fuller designed many geodesic domes after the end of the second world war and was awarded the US patent for geodesic structures.
Bearfoil as an Architect I find your definition of Architecture interesting.
As I understand it the first geodesic structure was a planetarium for the Carl Zeiss co designed by Wather Bauersfeld just after the end of the first world war.
Geodesic structures are used by architects and structural engineers to enclose any curved space. An example would be the geodesic sphere that forms Spaceship Earth at Walt Disney world.
As mentioned earlier an American engineer called Buckminster Fuller designed many geodesic domes after the end of the second world war and was awarded the US patent for geodesic structures.
Bearfoil as an Architect I find your definition of Architecture interesting.
Joined: Jan 2006
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From: Dorking
BF.
Sorry not to get back to you sooner. I'm having a bit of trouble trying to keep up with the thrust of your posts. At first you said that Geodes/tics were very similar to more modern CFRP, which, in laymans' terms is close enough. You then thought that I might be falling for 'Fullerine Dogma'.
Where was dogma in Fuller? Of course a composite allows far more elegant solutions than geodetics ever can. But, how can (and more's the pity) a football get made out of 2d fabrics without linking planar surfaces in clever ways.
Just need to clear my mind a bit before launching in to the Maths.
ps. What kind of things do you design? I'm currently busy in automotive dynamics, but have had fun with boats and 'planes too. Did a few houses too!
Sorry not to get back to you sooner. I'm having a bit of trouble trying to keep up with the thrust of your posts. At first you said that Geodes/tics were very similar to more modern CFRP, which, in laymans' terms is close enough. You then thought that I might be falling for 'Fullerine Dogma'.
Where was dogma in Fuller? Of course a composite allows far more elegant solutions than geodetics ever can. But, how can (and more's the pity) a football get made out of 2d fabrics without linking planar surfaces in clever ways.
Just need to clear my mind a bit before launching in to the Maths.
ps. What kind of things do you design? I'm currently busy in automotive dynamics, but have had fun with boats and 'planes too. Did a few houses too!
