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Old Jun 24, 2014, 03:56 PM
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Why is the blimp forum totally dead?

It seems like discussions on this board have nearly completely stopped in the last year or so. Has the high price of helium just driven people away from making blimps?
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Old Jun 25, 2014, 12:07 AM
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Was the price of helium ever a factor?

That's kind of like asking if the high price of feed is the reason nobody is posting about pet elephants anymore.

I'd be posting more about micro blimps, but life has thrown me a curve lately and it's been near impossible to complete any construction. My Helium costs are barely more than coffee money so I can only assume that there's a barrier to entry preventing others from doing the same.
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Old Jun 25, 2014, 01:30 AM
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Well, I know one guy who used to post here who stopped flying blimps due to the increasing cost of helium so I figured maybe it has become a problem. Cost is ALWAYS a factor unless you happen to be so rich that you don't have to worry about money, which is not most people. If you are flying micro blimps then you are not going to notice, but if you have to put 200cf or more in to your blimp then you'd have to be drinking some pretty expensive coffee to exceed that.
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Old Jun 25, 2014, 10:03 AM
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I agree, for larger blimps the primary cost would be helium. But the way I see it, you've only got two options. Fly indoors or fly outdoors.

If you're flying outdoors then the size and power envelope of your blimp has to be of elephant proportions. You can't just throw a blimp in the trunk and head out for a day of flying. This will limit participation to a handful of people who can either afford it, or commercial ventures. I don't think commercial ventures have much reason to post here.

Anybody can afford to build and fly indoor blimps, but you need a facility to fly in and there are no off the shelf products to get you going. For less than $50 you can be up and flying a micro quadcopter in the comfort of your living room. But an indoor blimp would barely manage bumping from wall to wall, if you could buy one, which you can't. I organize indoor flying in my parts. So I know it's a limited audience to begin with, and none of the regulars could be bothered to fiddle with building blimps. Very few people have access to a large indoor venue outside of some kind of organization.

I've occasionally seen commercial micro blimps along the 'Good Year' style that look really interesting. But they've always been out of production or impossible to get locally. I wouldn't have started building my own (initially) if there were easier ways to get started.

If a manufacturer were to come out with a line of RTF indoor blimps that actually did something, instead of an anemic air swimmer, I think there would at least be some resurgence of interest.

I see very little scratch building in most of the other forums (like say boating). The bulk of posting is manufactured products, with modifications and a little scratch building thrown in the side. So without manufactured blimp products to fuel new and existing 'blimpers', there's not much left to discuss (I fear).
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Old Jun 25, 2014, 12:25 PM
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I wonder if there were a website that offered how-to manuals for scratch building blimps, along with selling a few types of hard-to-get films that are required if this would help give blimping more popularity. I would invest in such a venture if I thought the market was big enough to keep from losing money on it. I'm going to have to buy the films anyway for another project I'm working on, so if I just made a machine for spooling them off onto smaller rolls for resale and have my wife run that operation it could be done. The two films I'd sell would be 2 mil white polyurethane and silver LumLife (aluminized PET with 4 times the helium retention of aluminized nylon).
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Old Jun 25, 2014, 02:13 PM
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I don't know how much of a market there is. If you build a plane a little to heavy you can usually put a bigger motor on it and still get it in the air or at least put it on the shelf where it will still look impressive. Build a blimp too heavy and it's nothing more than recycling. That will turn off most people.

I think there would be a market for pre-assembled envelopes in various sizes. Not the two side flat 'balloon' type whoopi cushions, but real multi-gored envelopes. They could be done in different profiles, like say a Hindenberg or sport model, instead of the same old 'blimp'. I think ready made guaranteed envelopes would really kick start the hobby. Inexpensive reversible micro sized ESCs are also hard to come by, yet not difficult to design and manufacture in small batches. With pre-made envelopes and available ESCs, 90% of hard work is done and just about anyone can mix and match building materials, motors and batteries to pull together the last 10%.

I really enjoy building envelopes, but my current hot glue technique is only temporary at best (hot glue always looses grip over time). I'm starting to tire of re-building, especially when I get a good flying blimp. It's frustrating knowing that my next best blimp is going to be wasted Helium after a handful of flights. Maybe I needed to learn that to appreciate a commercially made envelope. I'm ready to pay a reasonable fee for an assembled envelope that I can trust to last a while or at least the materials to create my own design.

If I'm not mistaken Pyro, you were doing stuff with a large computerized cutting table (and possibly seam sealers). How cool would it be to draw up a blimp profile online, specify the dimensions, then have a program section it out, calculate the weight of the material, the number and weight of the seams, and volume of Helium and lift? Then order the envelope, cut and sealed to specification? Man, I could stop wasting time (and Helium) wondering if there will be enough lift for the weight, and 'know' the design will support what I have in mind. Even if the envelopes only needed seam trimming (or pre-cut only needing seam sealing). I can't tell you how much I dread cutting out gore after gore to the same exact pattern. From there it just a matter of providing a few proven designs to hobbyists looking for a quick entry. I wonder if the final price would be even close to my budget

Shoot me a pm about your film selections. I'd like to know more.
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Old Jun 25, 2014, 03:09 PM
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I do have the CNC machine working for both cutting and heat sealing seams now. The only time consuming process is taping the film down to the table, as the vacuum table was not adequate for pulling the film nice and tight. I'm trying to develop flying saucers with it currently, but multi-gore blimp envelopes would be possible too. I'll have to develop a process for that to see how much manual labor can be reduced in making one. The foil type material is the easier one to work with, as you don't have to worry about it sticking to the heat sealer. The PU requires a barrier when sealing, which adds more work and materials to the process. The whole step of creating templates and using them as cutting guides is eliminated though, which also makes scaling to any arbitrary size a non-issue.

The 2mil PU film from API would not be suitable for micro blimps, it is just too heavy. The LumLife is very light weight just like the aluminized nylon though, so it would work great for small indoor blimps. The smallest minimum order I could find for aluminized film is 1000 lbs, and the cheaper suppliers from China require a ton or more. So it really requires a big chunk of money up front to even get the stuff. The PU is not so bad, API will sell you just a single roll if you want. The foil just has superior helium retention and weight over PU, not to mention being easier to seal.
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Old Jun 25, 2014, 11:31 PM
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Hmmm.... I never thought about how to pull the film tight. That's always a chore. I cut my gores eight at a time, folded in half so they're symmetrical, so it's a single cut through 16 layers. I guess that explains why I have to press so hard But ya, each layer, each fold needs to be stretched flat and taped. I guess that problem doesn't go away with foil on the roll. That would be a show stopper for volume production if you can 't work out a method.

Man, a 1000 lbs is a life time supply many times over for the entire (hobbyist) blimp building population of the world. There's no way you can make your money back on that. LumLife has been on the market for over 5 years now. There should be other sources available. LumLife MK61 looks like it's used in the food industry for foil wrapped food. Maybe it's just a matter of finding the current buyers of LumLife and contacting them until one is found that is prepared to off sale roll ends. Some kind of cottage industry food packaging?

My most recent blimp is a modification of it's predecessor. I simply cut the blimp pattern in half at the mid point where the profile curve is flat, then insert a cylindrical tube between the nose and tail cones. This easily doubles the capacity with very little extra work and materials. The mid-body extension completely changes the shape of blimp of course. It wouldn't be hard to come up with a half dozen preset variations of nose and tail profiles with calculated material and final volumes. Then the blimp designer could pick and choose from these, add in a variable length mid body cylinder (or not) to achieve the final design shape and the whole thing could be calculated to any size and patterned without resorting to complex math and CAD drawings. There might quite a bit of manual work involved cutting, and seaming, but it might not be 'too' much manual work for the price.
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Old Jun 26, 2014, 12:00 AM
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I tried getting a rep to send me a sample of LumLife last year, which he said he would do but never did. I get that a lot. It's like these guys aren't interested unless they know you are going to buy tons of the stuff. API is the only company I've dealt with that says they will send a sample and then actually does. I'm going to try to get the LumLife sample again though. All I want to do is verify the helium retention compared with aluminized nylon, since it costs twice as much.

For a CNC machine that is doing all the work sealing and cutting work, having to manually splice in a cylindrical center piece would actually be harder, since the machine can't do that. My cutter can apply up to 100 psi against the table though, so cutting through multiple sheets at one time should not be a problem.

I've watched videos of commercial CNC machines cutting films and it looks like they have to tape it down too. Vacuum tables tend to create wrinkles, and then you have the little holes that will interfere with cutting and sealing.
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Old Jun 26, 2014, 12:23 AM
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Well, for what it's worth I just requested information on product samples from Toray Plastics on their website. Not that I'm expecting anything useful in a response, but you don't know if you don't try. It's odd that almost all the google hits on LumLife focus on the 2008 product announcement, but virtually nothing in the way of more recent links or distributor sources.

I'd like to see your table in action. Every time I start cutting gores I envision computer controlled dual roller cutters pressed against a roller foil feed much like a compact drafting pen plotter printer (the kind that hangs a big sheet of paper over a roller as it draws). If the foil roll came on rolls in small widths (like say 10" or so) it could just feed through the cutter and the gores would be sliced out like banana skins while the cutting rollers just zigzag in and out (or maybe dozens of cutting wheels cutting multiple gores out of a wide roll). It shouldn't be hard to keep tension on the roll source and a pickup roll for the scrap to keep things feeding through the cutter smoothly. Of course, I'm still thinking in terms of 'only' cutting. A machine that could seal and cut a seam in one step would be infinitely more useful, but maybe not applicable to a continuous feed cutter.

I would assume that foil party balloons are fed through a machine as top and bottom rolls of foil that are then stamped and cut in one step by large dies.
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Old Jun 26, 2014, 12:45 PM
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I'm sure the party balloons are made as you suspect, I doubt any hands have to even touch the foil during the process. My saucers use similar two-piece construction and if I ever go into production with them I would make a similar dedicated fixture for stamping them out. They are not entirely the same though so I wouldn't be able to crank them out at the speed of a simple foil balloon. It's a three step process currently, where an operator has to get involved between the steps.

With the CNC method, the seams are sealed before they are cut, otherwise you lose the tension in the film. I think typically with the hand made method you cut them first and then seal them using an iron, so you have to work from trimmed edges with a lot of effort put into keeping the edges from curling up after being cut. I've done that in the past and yes it is a huge hassle. A CNC seam sealer can roll a seam anywhere on the sheet of film and repeat the exact same pattern in the exact same spot with identical pressure and feed rate over and over, so you can keep adding gores in a stack and folding them like a book as you go. A dual head would not be of much use since you are only sealing one side at a time, with only the final gore getting seams on both sides. The cutter only has to trace the gore pattern one time, assuming it can slice through the entire stack on one side, so not much time would be save with a dual cutting head there either. A dual head just wouldn't be worth all the extra cost and special programming for using it. I've seen them used in the garment industry though, and they do cut the production time in half when cutting out symmetrical patterns to be sewn together later.
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Old Jun 27, 2014, 10:11 AM
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Here's the CNC machine making a seam on some aluminized nylon:

CNC: Sealing Aluminized Nylon (0 min 59 sec)


Note that the sealer lifts of the table and does a 360 when necessary to keep the power cord from getting wrapped around the post. When the seam is done, the rotary cutter tool you see will then be used to cut out the finished product.
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Old Jun 27, 2014, 03:29 PM
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That's really cool. The roller seams to drag on the foil as it goes. I wonder if a stepper motor driving the wheel would keep the tension neutral?

I see the problems with keeping the foil flat and smooth. I don't know how you could attempt multiple gores folded (let alone automate it). The heat seal is only one side of the foil correct? If the foil was folded into multiple layers, how many layers do you think the heat would penetrate to create a reliable seam?
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Old Jun 28, 2014, 12:19 AM
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I don't know if it's really dragging or if it is just pushing a wrinkle in the foil and the wrinkle grows in size as it gets pushed ahead until the wheel finally rolls over it after it can't go any further. I think if the film were secured along it's entire edge this wouldn't happen.

The original heat sealer wheel had a knurl in it that I assume was to help keep it rolling. The problem with that is it left tiny holes in the seams that leaked like a sieve, so I took off the knurl using a lathe to get rid of that problem. I've never seen wheel actually stick and stop rolling, so I don't think it's a problem anyway.

I'm working on a holding fixture made from aluminum screen porch frames which have the groove along the edge where the film can be pushed into the groove and held in place by a strip of grooved rubber tubing. This way the entire edge is secured and no tape is involved so setup is faster. I might be able to put one of these hold-down bars on each end, then wedge a weighted stretcher bar with a rubber bottom surface between them on the other two edges and not have to tuck the sides into a groove.

I've seen the sealer go through four sheets of film, but the seam on the bottom is not as strong as the one on the top. I would only be sealing one seam at a time for blimp envelopes, they would just be piling on top of each other during the process, then only the cutting stage would go through all of them at once. If the cutter can't get through all at once it's not hard to just run the program again for multiple passes, sine it will trace the exact same spot each time.
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Old Jul 03, 2014, 02:34 PM
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You know, I've been racking my brains for a way to create a 'folding' table (as in folding foil, not a foldable table) that would allow you to just feed a roll of foil, then let the seam/cutting tool do it's thing. But I just can't picture it, which leaves too much manual setup and preparation.

I'm about to start messing around with irons and heat sealing (scrap commercial foil balloon). Instead of the usual seam (flat/fold/butt?) I'm going to try using a ribbon strip, to make a flat seam. Lay down the ribbon (melt side up), then butt match each gore (melt side down) over the ribbon and seal. It occurs to me that this technique might lend itself to some sort of roller feed which would cut two gores and run them through a set of sealing rollers with the ribbon joiner. I don't know if it can be fully automated either, but the final seams would be flat and very secure.
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