Really really cheap lift bags

[[The only  way I see it happening  is to make  a LOT  quickly  and get it in the envelope  with a  store bought  cylinder  or 3  at  2500 PSI  of  ether  H  or HE  to get the envelope to  correct pressure . I have not  seen  a quick  or cheep way to do this  at home ,]]

  We don't have good permeability figures for the various thicknesses of PE film or for the perhaps better PU film. One thing we know is that permeability is simply  inversly proportional to thickness. That means that we may have to go to 6 mil, or more?, thickness to preserve H2 longer.

   I personally am designing a multi lift bag ship of 25 bags with 20 pounds lift each for 500 pounds total lift. The bags will be inflated one at a time and stored til flight time. They'll have leashes on them so they can be taken for walks to the storage place and then walked to the envelope and inserted in the right place one at a time. this seems more manageable than inflating the whole ship at once.

   [[  Knowing  this  ratio 24 / 7   is  the only safe  way  to manage and fly with H2  safely . ]] 

   Not really.  It doesn't hurt but it's not necessary.  It takes 25% air inside the lift bag to produce a flammable mixture. That means the bag must lose 1/4 of its lift before it'll burn. That is EZ to measure; just pull down on the bag with a fish scale which can measure that much. 25% lift loss means the airship will have lost its rated liftability weeks ago! And it's not gonna change that much in one week or even a month.

Here's a site on making H2 chemically, extremely simple methods

http://www.tutorvista.com/content/chemistry/chemistry-i/hydrogen/hydrogen-preparation.php

I agree with the cold air inflation and foil lamination of the interior of the envelope. This is easy and cheap to do and will greatly reduce permeation. 

Easy?   You will want to be inside the envelope while under pressure, means having a really good and reusable air lock hatch system.   You will need about 30 cans of 3M90 or better contact spray glue, which says on the can use in the open or with plenty of ventilation and avoid sparks as it is very flammable.    You may need oxygen to breath.   You may need to spray the aluminum outside the ship and then bring it in with wax paper rolled in between it like a capacitor.   The whole ship will have to roll over on it's back so you can press this onto the ground, I mean floor, it will have to be done indoors.   The spray must be applied to both surfaces, plastic and aluminum and let dry for a few minutes to stick well.   There is what in a roll of aluminum, about 45 feet on a large roll of about 1 foot wide.  You will need about 35 to 40 rolls, only about 100 dollars.   3M 90 will cover about 70 sq ft or so and it costs about $15 dollars per can, you will need 30 cans of spray.   That's about  $550 dollars so far.   There are less expensive quality spray glues that could bring your cost down to about 250 to 300 dollars.    You will need a very good, flat floor, like an outdoor basketball court or a tennis court.
    For the money and the trouble and fire risk, I would rather go with a six to nine mil heavy plastic and know it will be durable.   Can someone weigh a square foot of aluminum for me?

BALLOON SEALER  is called Hi-Float

http://www.balloonhq.com/faq/deco260.html

This site describes the use of commercial brand "Ultra Hi-Float" which is a spray sealer for latex party balloons to make them hold helium longer.

    It's flexible so it'd work for PE loose envelopes. they say it 25X's the balloon life so it might be 25X'ing the impermeability.! Even though it's advertising puffery, we cannot ignore that.

May be too expensive to use on big man-lifters but the principal of spraying something on the envelope to seal micro-pores in PE is something to remember.

http://www.hi-float.com/pintinstructions.wmv

Easy?   You will want to be inside the envelope while under pressure, means having a really good and reusable air lock hatch system.   You will need about 30 cans of 3M90 or better contact spray glue, which says on the can use in the open or with plenty of ventilation and avoid sparks as it is very flammable.    You may need oxygen to breath.   You may need to spray the aluminum outside the ship and then bring it in with wax paper rolled in between it like a capacitor.   The whole ship will have to roll over on it's back so you can press this onto the ground, I mean floor, it will have to be done indoors.   The spray must be applied to both surfaces, plastic and aluminum and let dry for a few minutes to stick well.   There is what in a roll of aluminum, about 45 feet on a large roll of about 1 foot wide.  You will need about 35 to 40 rolls, only about 100 dollars.   3M 90 will cover about 70 sq ft or so and it costs about $15 dollars per can, you will need 30 cans of spray.   That's about  $550 dollars so far.   There are less expensive quality spray glues that could bring your cost down to about 250 to 300 dollars.    You will need a very good, flat floor, like an outdoor basketball court or a tennis court.
    For the money and the trouble and fire risk, I would rather go with a six to nine mil heavy plastic and know it will be durable.   Can someone weigh a square foot of aluminum for me?

-inventive47

  This is   a matter of   using  a   big  enough  fan   and keeping  the   "hatch" partly open  to  keep  a  fresh  air  exchange happening .  And  also  a matter of   degree  As to  how  fast  you  wanted  to  work it . Doing  a  strip  at  a time   and  letting  the  spray  fumes   go  away  then  do  another .  Something like  that . And  a  organic  vapor   respirator   might be  a good  thing  too.  Pre  tacking  the foil  is a  good idea .    I  have  found  18 inch  wide  and 1000 ft rolls  for  45  bucks . 
 There could be   some  water based   adhesives  that  work   too .  One that  might be  good is  called  Stewart systems  .
    Anyway  this  is not  going  to be  a  fast process ,  nor  should it be . I think  you  will want to be  very  exact .  So  given  that    its  doable  and  could be  safe  enough  even using  spray on  stuff .  Just take your  time .  
    Here is  a  situation  that happened  to me   I  worked on  Corp jets   turning   green  aircraft into corp  flag ships.   We  were  applying  lead vinyl  to  the  inside  skin  with  what  smelled like  plastic model glue . 
 Gallon Buckets of  this stuff ,  open  ,  with 5 paint   brushes  going to  town  .  I  breached my  mask   just  to  see how bad it  was , and OMG!   If  anyone  had  so much  a  farted in there,   we would have blown up!  
 I  got out  quick  and got  the Super out ,  And   Oh  yes   we  slowed  down   ...a whole lot , One  frame  section  at a time ,  and get out  !  So   yeah   if  your  doing  this with   sprays ,  remember,   There is no  rush . Play it  safe  and smart .
 See  the  Myth  buster  Episode  lead balloon .  I posted  the vid   somewhere on here .     

  I don't see trying to deal with aluminum foil, it is so fragile. The party balloon plastic is layered with aluminum with minimum holes, and is easy to weld, maybe glue. I'm sure it only takes a layer one molecule thick to hold gas. If we can get the mylar pre-welded as wide as our boat wrap, construction would be super simple. Just allow a little extra mylar on the inside so it doesn't get stressed as the ship inflates, and there you go. Clamp it all with the poly fastener and start filling.
  For a ship like Nav's it will be a fun video showing him shoving cells into his ship while it is jacked up in a field somewhere. Sorta like herding cats, I'm sure!  Good times, good times.
  I'm looking into having the cells permanently installed, with little fill tubes to them. This allows me to monitor each cell, and add or vent gas as necessary.

I'm  sure  the  party  balloon  film  will  stretch out  to  about  the  same  as  the Boat wrap will . This  will make  "pre lamination " easy  .    Its more  expensive  than foil  thats  for sure .  Hope  some  day  soon  we can  see a side by side  comparison .  

Well foil won't stretch. The boat wrap will. You will have to have a little extra foil material to keep it from being stressed.

Exactly  right  Dude. ,  thats  why  you  would have  to  cold air inflate to a " inflated and ready to fly  " condition  to  apply  the foil inside .  The  envelope plastic is  going to  stretch out in all directions the foil  can compensate  for .  It  will have to be  applied   when  the envelope is  fully expanded  with  normal air.   

edit see underline

Exactly  right  Dude. ,  thats  why  you  would have  to  cold air inflate to a " inflated and ready to fly  " condition  to  apply  the foil inside .  The  envelope plastic is  going to  stretch out in all directions the foil  CANT  compensate  for .  It  will have to be  applied   when  the envelope is  fully expanded  with  normal air.   

That'd be good

____________

business opportunity
Locksmiths

Hey truongvuhung9, welcome to the forum.

Hi, jamesg, thanks for the reply, maybe I expressed myself badly, but what I meant, with the comma, is that the metric system, the comma comes after point from left to right and the imperial system, the comma comes before the point. I once ordered a British company that built for me a little envelope of an RC blimp with 52,22 meters cubic by a British company and they sent a message back, asking if it was fifty two thousand and twenty two cubic meters. So I posted this as a warning to all of the forum, because we MEMBERS around the world, speaking multiple languages ​​and using two measurement systems. Forgive me for my errors of translation into English, to communicate I'm using Google Translate, imagine if the errors are the measurements of the prototype of the blimp?

I built two Blimps RC flying saucer-shaped with a diameter of 6 meters and 30 cubic feet of gas, both are designed to be used with four types of gas, helium gas, ammonia gas, methane gas and hydrogen gas. the gas that I use most is the helium gas, other gases will be used to support performance testing of static lift, so I got the idea of ​​using a long tube of metallized plastic film with low permeability to helium gas (those used in party balloons) that will pipe 1.16 meters in diameter and 33 feet long and weighing only 2, 5 kg. (wrapped in a spiral inside the blimp) Obviously this has increased the area alongside the escape of helium gas, but when the helium gas escape from the tube it will have to go through the external envelope, that is, I have double barrier to hold the more expensive helium gas, so I can remove the tube filled with gas through a port of the steerable under the Blimp, without losing a cubic centimeter of helium gas and put in place another tube of hydrogen gas, for example. The larger the diameter of the tube, the smaller the area of leakage of helium gas and also have shorter length of the tube. So if you look, you'll see that enhances the loss of gas and has an excellent value, cost / benefit. Please give your opinions.See photos of my BLIMP. 

Thanks, Guibs.

PS: I still do not know which of converting the thickness of thesheet of transparent plastic that Boldt was referring to in his post Re: Off the Shelf Item List by Boldt, 20 April 2011 08:42 PM where he mentions that the clear plastic sheet with: Plastic sheeting (6 MIL) I DO NOT KNOW THAT MEASURE THICKNESS OF PLASTIC SHEETS. The measurement of thickness of plastic film that is used in the metric (microns) or (microns). Please help me find one in the  store that sells only 3kgplastic film metallized  MYLAR or NYLON metalized (BOPA).

However both have to be heat-sealable. with 10 - 12-15 or 17microns thick and with at least 2 meters wide with low gas permeability (according to the specifications of a Chilean company that produces and sells this material in large quantities to the USA, however the material Chilean company that produces, is not heat-sealable, the USA buys this material makes the dubbing and transforms the  TERMO-sealable material with low permeability to gases, with less than 5 cc / m 2 / day (with a gas leak of 5 cubic centimeters per square meter per day)

I need to find the site (SOURCE company) in the , which makes the lamination of this material (the material transforms into heat-sealable) and sells to companies that are metalized balloons for children's parties. I tried to buy this stuff in companies that manufacture metallic party balloons to fill with helium, but I did not get success. Please help me find the address (site) of a SOURCECOMPANY, where I can buy this material 3KG thermo-sealable.

How did this post jump over to this thread?

Anyway.

1 MIL (.001" or one thousandth of an inch) = 25.4 microns.

So, 6 mil = 152.4 (or ","  ;)  ) microns,  or about a tenth of a millimeter thick (0,1524mm).

Do a google search for "mil to micron conversion" and it will even do the calculations for you.

I have no suggestions on who to contact for a source of the heat sealable metalized mylar but give google more of a work out by searching for "plastic film" and it will produce a long list of companies that provide various film products.

All I have been  able to  find on a "retail '  sales of  balloon foil  is  from Felix Press at  balloon kits.com 
 Anything else  seems to be   geared toward industry  sales of  hundereds of thousands of feet,  and dollars .8( 

Given that one would only be in the air in their ship a small fraction of the time, say 2 percent of the time, the other 98 percent of the time in storing it in a hangar, so this is when 98 percent of helium loss would happen, or hydrogen.   A large thick plastic barrier has been suggested to help retart the diffusion of gas, but it needs to be tight and wrap around as much of the ship as possible.
.
.   Another way to retard helium loss is with water.  Yet if you spray water on your ship it will bead up and run off.   RainX makes a substance called FogX which causes water to build up on a surface with an even film and not bead up.   Given the time and effort a person could coat his ship with this stuff, wet it down, throw a plastic cover over, perhaps sucking some of the excess air out with a shop vac and leave it for a week, then take it out, let it dry for a few minutes in the sun and it's ready to go again.

<<< the other 98 percent of the time in storing it in a hangar, so this is when 98 percent of helium loss would happen, or hydrogen.>>>

   During storage and during off-periods, the airhips lift bags should probably be emptied into big "nurses" for less permeation-loss of H2.  These nurses are thick plastic and have much less permeation than the thin and necessarily lightweight ~5 mil  flight bags of the ultralight airship.  [permeation is mainly a function of bag thickness/weight, among other things of course]
   the good news is that hydrolyzed H2 is a quantum factor cheaper than helium.  My BOTE calc is that a home hyrolyzer might generate the required 250 cubic meters of H2 for  $400 of electricity.  And it would take 3 months to generate the entire quantity. This 250 c m would be contained in 20 different lift bags rather than filling the entire volume of the airship envelope in just two or three compartments like a blimpo would do. The object is easily handling and cycling  of the H2 volume. That requires a type of "cluster balloon" dirigible.

    Now, by the time the last bag is filled, it will be time to think about replaceing the first bag due to its permeability letting enough oxygen inside to bring the H2 concentration down to near-flammable limits.  That's good and that's ok!  it simply means that every ten days or so , you'd replace the oldest $40 bag of homemade H2  with a fresh bag! That's cheeeep operation costs for an airship when compared to buying rare and non-renewable helium on a regular basis!
  the "old" H2 could be cleaned up and re-used if the required machinery proves cheeply available ... or the H2 could simply be released to atmosphere. it's only a $40 bag of renewable gas.

This concept may not work with Nav's unit, but may work with mine: The outer shell is pressurized with 'old' H2 to increase rigidity. This pressure bears on the inner cells, and maybe reduces loss of 'new' H2. The 'old' H2 leaks out and is replaced by the next 'old' bag in line. 'New' H2 is constantly being created by solar panels and an on-board Hydrogen generator. Once an 'old' H2 bag is totally empty, it gets refilled with 'new' H2.
Presumably the 'old' H2 is carried away and doesn't get into mischief.

Yes, i can see where old H2 surrounding new H2 cells would reduce loss of new H2.
    ...but isn't old H2 partly oxygenated?  that's a lil scary, even if it takes 25% O to become flammable.