Sprung panels for a rigid hull without high-pressure membranes

Hello All

I mentioned the use of sprung panels in tents and that I thought this might allow for an envelope where tension - and therefor rigidity and resistance to aerodynamic loads - could come from this method rather then relying on gas pressure.

The panels work by having a rim made of a plastic loop in compression - which then tries to spring back and keeps the panel in tension.

Here is a little tent that works this way:

Here is what it looks like when folded up - useful

Here is a close-up of the edge - showing the compressed rim that keeps the panel in tension

This is just an idea you understand - but assume you used something similar to the tent but with six sides instead of four - that would make a nose-cone with basically triangular panels - then the next section of the hull can have four-sided panels - however long we want, but with the narrow end the same length as the ends of the nose-cone panels and joined to them and the wider end somewhat longer so as to make the hull grow wider - and so on.

Do I make myself clear?

Maybe I'll make a model to show you what I mean..but does this explain the idea?

Neil

OK I made a model - just by way of explanation:

See here:

Obviously this is just a quick bodge-up to show the idea.

Neil

Would your idea be like this? Or would it be done with many different panels? This is the method that is used by the hot airship Alberto. I think hoops make more sense than straight ribs, and I think that is what you are advocating.

Yes, as you say.

Hoop-sprung panels was what I had in mind - if you look at my little model (link above) then each flat panel - which is just paper in my model - could be a sprung panel.  I knocked up a standard zepp. shaped floater, because I had some dimensions worked out already, but it is adaptable to other shapes, such as more wing-like aerodynamic-lifters.

The Alberto is what I referred to as 'umbrella' construction if I understand it correctly - it has two limitations for me;

1) It only works for a bulbous shape like this - if you tried to make it more 'cigar-shaped' the middle would be floppy, since it is the curvature of the ribs that creates tension.  If we want something capable of navigation in a reasonably wide window of conditions, the shape needs to be more streamlined.

2) If a rib breaks you have a problem - you lose shape and structural integrity and you have a potential spear near the gas-bags. So don't hit anything.  This inability to take a knock has caused a lot of trouble historically - as everyone here knows, I imagine. 

I would hope a sprung-panel ship would bounce better - even if you got a few broken panels from whacking a tree or the ground the neighbouring panels would take the load so the ship bends without breaking.  If you break a panel, it should be easily fixed.  I don't see why we couldn't zip them together to make the hull.  Of course, that assumes we use internal balloons to hold the gas.

This second point - the need to absorb punishment without failing - is something that my years of hang-gliding have left me pretty convinced about.  I have seen people die when their equipment fails.  I am old enough to have flown Bog-Rogs (bog-standard-Rogallos).  I was young and stupid - you would not get me up under one of those things now.  The air is not a forgiving environment, as we all need to remember.......

Years of ground-handling hang-gliders makes me think that a blimp that cannot stand being smacked into the ground hard and often is not something I want to be relying on.  A hang-glider is a hard beast to control on the ground in any sort of breeze and these blimps have much bigger surface areas.  They will get thumped about during ground-handling.

Anything that relies on strong but rigid frames causes me a problem in this regard.  The parts of hang-gliders that caused trouble were the aluminium spars, rather than the dacron wings.  Have a hard landing and you have to check the spars for dinks VERY carefully.  Dinks can cause buckling failures.  I have a friend who had his leading edge break 1/3 of the way out along the wing due to this.  He came down like a sycamore leaf - but faster.  Very fortunately he fell through the roof of a barn - which slowed him down a bit.  He only broke a few bones.

Neil

 I started out on  Rog  wings too.  Yep , we were nuts.   Todays birds  are Cadillacs  in compare. PG or PPG flying  has the  edge for  not worrying if you  bent something on a hard landing, Set up is for sure  quicker ,  but flying slower an  Thats really fun too.  
  Yes  , basically  joined together auto sunshades .  Would you use the tent size panels  or   would the panels be larger?  What  would be your material  to use  for the tension frame on  larger panels?

I didnt want to start another thread for the same purpose.  So  here is my idea to  "rigidize" a hot air balloon without adding too much weight:

What about attaching  "encirculating"  inflated air tubes  out of light rubber around the envelope?

 That should  be a start. It might not be rigid enough though... hmmm. But if we could pump lots of air inot these airtubes it would pretty rigid!.   and I am not talking about car tires here either:D!

Right ,  The  real hot air airships  use part of the prop wash  to inflate  and keep pressurized  the tail  fins .  Maybe something  similar to  that ?  
 If there was  a way  to  deflate them quickly  to  get the  envelope  down   so  it  wont become a sail .  It  would be  good. Maybe  pockets  swen into  the envelope  to install and  capture  them in?
 Once heated    it  would  offer   just  a little insulating  factor . 
 

One wants  the envelope inflating to be easier and  therefore it must be more rigid.  Sprung panels or what they are called plus  air tubes  are a start. any more ideas?

That is a good point. Air tubes could keep the airship from becoming a sail when deflating. So there is a possible solution for IM's deflation problem. 

Depends on  shape ,  Some  could  use  sprung  frame members  along  with  pneumatic tubes  and  sprung panels .  Frame members like  pop up  tents   use  bent  rods in tension to hold  shape. Nav is  experimenting  with  Sprung  frames .   

~~Cue the guy with the sprung frame~~~
   Oh hello. I just made one today.

It's a 15-foot long, 25% scale airframe made from bendy 3/4" pvc pipe and I coverd it with 3 mil PE film. I blew it with a fan and immediately discovered the nose spar bends downward with the smallest air pressure. I'll have to watch that when I make the fiberglass spars and might have to add a structural stiffener to the spar.

  
So far, this technique seems very lightweight and doable on a larger scale without much complication beyond that of fabrication of the fiberglass tubes.

The pvc pipe was only about $3 per 10-foot length is why I chose to go ahead with it even though it can barely support its own weight when held horizontally by one end. And it went together in an hour.

{{{ Sprung panels or what they are called plus  air tubes  are a start. any more ideas?}}

   Helium tubes. Nice and fat so they lift their own weight at least. Put an inner tube belt inside at the waist of the hot air ballon and turn it into a fat saucer shape.

   In fact, to imagine even further, why not make a b ig fat helium toroidal soft doughnut and cover that with a saucer-shaped hot air shroud and use the heat to expand the helium to where it firmly stretches the shroud.?

   When the heat is off, the helium may shrink to less than equality and we become HTA and land heavy with no ground crew.

   Plus, the saucer shape has lift when making forward speed so when we slow down and turn off the heat, we go down extra heavy but we still have aerodynamic form and can glide in for a landing.

   Call it a hybrid hybrid? It offers two ways for variable buoyancy. And what is VB? Right. The holy grail of airshipping.

Say Yup to UP!

P.s. on the topic of variable lift, Alan Handley emailed to say he is making progress with his big concept demonstrator. So, even though he doesn't update his website to the minute,   http://varialift.com/   , he is still in the game. His compressors and tanks are working and he is starting on his lift bags and there's not a lot to make after that. I think he's shooting for about 250 kilos of lift and the same amount of down weight.?  Don't quote me.

Something  on  the order of  a inflatable  tent.

couldnt you just get tyhe manufacturers of that tent to make you a buble they almost have the perfrect shape inventing man.

You know, amemoi, that's not a bad idea at all. A couple of those tents, with the tubes filled with helium, and the interior filled with large party balloons and weather balloons, you just might get some good lift!
  The openings could be combined to enclose the cabin/motor/tailfin assembly. All the really tough envelope and structure work is already done!
Deflated, the two tents would probably be manageable. I think two to get enough volume for lift.

my thoghts exactly

have you guys seen this one?

it is an interesting concept. im not sure how much weight it can stand though.

any ideas?

That's a really nice looking ship, I wonder how much they have invested in it. I looks really durable, should bounce off any obstacle, maybe just scratch the envelope, which should be patchable if the design is right.
It reminds me of a similar ship that has large inflated longitudinals and rings. The skin on such ships could be just zipped on and off for easy replacement.

i was thinking something like that, with the tubes containing hydrogen, then covered with a light weight net and containing the bladder balloons also with hydrogen, would be very cheap and easy. in theory even the net would be redundent if the bladders were made too large to slip out the holes.

any ideas on this?