Airships, Blimps, anyone...anyone

dingpud

Have any of the members out there done anything with airships or blimps? I am getting kind of interested in them and was planning on doing a DIY blimp or airship and wanted to know if anyone else has tinkered around with anything.

There are some small scale kits out there...
http://diydrones.com/profiles/blog/s...ogPost%3A44817
which are cool, but I'm looking for something that could maybe work outdoors and be a little more "rough and tough".

The mylar style balloons just don't seem like they could withstand...anything...

Weatherballoons are neat, but they only go one direction...well, two directions technically. Here's a really neat project a group did...
http://www.natrium42.com/halo/flight2/

So if anyone out there knows of blimp or airship manufacturers (other than ILC Dover and TCOM) let me know. Or if you've had success making your own airbags or envelopes, let me know.

Thanks

KalamMekhar

Beyond the hot air balloon type of home craft, I haven't ran across anything in my design books that helps with air ships. I will look around some more and see if I can find some stuff on DIY airships.

dingpud

Anything that you've got on airships....construction, projects, theory, etc. It's all good stuff to me...

Lancelot59

Looks like we have a common interest! I've been looking at trying to build one myself. From what I've researched so far the envelope is the trickiest part in a DIY situation. I had an idea for a rather cheap but what should be effective solution. Stuff a bag full of mylar balloons. The bag would just be a cover, and you just need to evenly pack all the balloons into the envelope.

The great thing is that you have a bunch of isolated cells, so even if some get punctured you don't lose all your lift.

I took a quick look around YouTube and found this: http://www.youtube.com/user/minizepp

These guys seem pretty good: http://www.minizepp.com/

dingpud

Yeah, I've thought about the isolated cells as well. Just think that an exoskeleton would then be required to keep it's shape. I've been doing some heat sealing of some mylar material to see how well it holds the helium...didn't realize how much money He was...

thanks for the link.

Lancelot59

How well has the mylar held up?

dingpud

As long as you get the stuff that you can actually heat seal...it seems to work well. Holds He decent...super fragile though. I am curious what the "big boys" are using in theirs. I am sure it's some sort of combination engineered material which us DIYers can't get a hold of cheap...

Lancelot59

Possibly, or it could be something much simpler. Perhaps there is some compound available that we could just coat some fabric in to create a gas tight cell. According to HowStuffWorks.com most full sized envelopes are made from "a durable, airtight, lightweight fabric (polyester composites) that is much like the fabric of a space suit." There has to be a cheaper way of getting it to work though.

mugaliens

The Hindenburg's gas bags were made of "goldbeater's skin," which is layered between gold before it was beaten into leaf as this as one micrometer.

Very expensive!

Aluminized mylar (boPET film) is cheaper, stronger, and more effective.

Lancelot59

Yeah, I don't have the money to get that much gold. However mylar should be fairly cheap. The only problem I see is trying to seal the seams. But if we can find a solution to that, this should become fairly simple. A flat sheet of material could be cut into whatever shapes we need.

mugaliens

Actually, BoPET is so smooth that it will adhere strongly to itself if it weren't not treated to prevent this. For improved vapor barrier perfomance, it's aluminize and a layer of polyethylene is added, which improves its ability to be sealed as well as its puncture resistance.

I don't think sealability will be an issue. The question is, when you start using large, house-sized helium-filled bags, how does one anchor them in a way which contains them while evenly distributing the forces? BoPET's tensil strength is seriously strong (something like 4 GPa), but you don't want to make it thick enough to carry the lifting stresses itself. Just thick enough to maintain containment of the helium. I'm thinking balloon-shaped nets with an interlocking hexagonal weave made of kevlar, but that might be overkill. Nylon would be heavier, bit I think it would work just fine. Cheaper, too, and nylon also has excellent abrasion resistance.

Of course silk might work, but there are serious cost issues with using silk.

Lancelot59

The strength of that adhesion might not hold the gas in once you get higher up and the gas starts to expand. It would have to be sealed with something. The mythbusters used tape to decent effect when they made the balloon out of lead foil. Some higher quality stuff should do the job well.

Balloon shaped nets seems like a good idea, if the material really lacks that tensile strength. You might even be able to get away using cables. The way I best imagine this working is having two rings on the top and bottom that the ends of the cables attach to, and then just have some thin wire wrap around each of the cables in several places along the height of the cell to keep the cables aligned.

mugaliens

The mylar bags would never be pressurized, but would simply be designed to expand. Besides, we're not talking 35,000 ft operations, here, as the carriage wouldn't be pressurized, so only about 20% volume differential between sea level and max operating altitude.

Self-sealed without the additives. Heat-sealed during the epitaxial alignment. One of about a thousand adhesives on the book, half of which would do admirably?

It's not an issue.

With all due respect to their experience, it's a TV show.

Lancelot59

Makes sense. I wouldn't wanna take this higher one or two thousand feet.

My knowledge of BoPET is pretty limited, so I'll defer to your assessment. I'll do a little more research.

I mentioned it because it's a solution that worked fairly well.

mugaliens

Ok. I'll run with it - Although gold is 70% more dense than lead, it's both far more maleable, and vapor deposition products do not corrode (oxidize). It might very well be a better solution than aluminized mylar, provided it provided better overal characteristics.

We might find beryllium to be the optimum choice, but since we know the characteristics of them all, let's specify the design requirements, first, then select for the best, perahps most effective life-cycle cost combination of materials within those design specs.

Lancelot59

Just to clarify, I was talking about the tape as the solution, and not the lead foil.

Given the scale we're working with, tall cylindrical cells don't have the volume we need. It depends on how the cells are going to be laid out. I'm thinking a cylinder laid out along the longitudinal axis. Big radius, and short. It would make the most effective use of the space available inside the ship. Each cell fits in between two frames, and should follow the curve of the skin fairly well.

I wonder if there's a specific shape that could be used on the actual dirigible that would offer more stability. A sideways oval I guess? Might as well start simple with a circular frame.

mugaliens

Here's a picture of one of the Hindenburg's gas cells, along with some other pics of its interior construction.

The gas cells cannot be full sized at sea level due to expansion at altitude. You can see this in the picture and accompanying text in the link.

As for shape, a hocky puck turned on edge might be appropriate, although the lower portion would be somewhat flattened to allow for expansion. Line 'em up along their mutual axis and you whind up with the aerodynamically streamlined form of a dirigible.

Alternatively, instead of a single hocky puck per cell, you can use two balloon-shaped nets containing a mylar bag. :)

Another advantage of mylar is the fact that it can be made both electrically conductive by means of the aluminized coating, while electrically grounded by the same means. Static can be reduced by means of this and other coatings, though I'm unsure of the static effects of enclosing mylar bags in nylon or kevlar mesh nets.