Airship builder in Bristol, Tennessee

Discussion in 'New Member Introductions' started by MikeK, Mar 29, 2019.

  1. Apr 9, 2019 #81

    lr27

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    I should think most of the airship will experience lower than ambient pressure when underway. Only a small area at the nose would need stiffening. Of course I could be totally wrong. And maybe if the airship got a bit sideways there would be higher than ambient pressure in other areas.
     
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  2. Apr 9, 2019 #82

    Riggerrob

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    Structurally, it is simpler to over-pressurize the hull. As long as skin is always in tension, it will hold its shape. Internal pressure must exceed outside atmospheric pressure.
    In comparison, battens are heavy and easy to break.
    PVC has a poor strength that weight ratio.’If you are going to install battens, use carbon fibre tubes.
     
  3. Apr 9, 2019 #83

    Dana

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    Easy enough to calculate the dynamic pressure due to airspeed, the internal pressure has to be more than that or it needs to be stiffened.
     
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  4. Apr 10, 2019 #84

    MikeK

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    I think those were called 'cloud-hoppers'. Cheap and simple way to get aloft, certainly to get a good view. At the current cost of gas, a recovery system would be nice. Bag it up, take it home to fly another day.
     
  5. Apr 10, 2019 #85

    MikeK

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    Not that I expect my ship to go fast enough to over-pressure the nose, I still plan to make that section out of slightly thicker plastic, since it is the most likely panel to suffer collision. Vacuum-forming is a simple process, I made nose and tail sections for my model.
     

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  6. Apr 10, 2019 #86

    BBerson

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    I watched a guy at Oshkosh fill about 50 weather balloons with helium and fly off.
    Seems a good way to go. A shooter would only hit a few balloons.
    I would use Mylar instead of rubber, to hold the helium longer. A light fabric bag could cover the balloons.
     
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  7. Apr 11, 2019 #87

    MikeK

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    I've seen too many videos of balloons hitting power lines, with deadly results. Any flying contraption has to have a way to avoid power lines. With mine, as a last resort, I can use the 'chein-de-mer' ( sailing device, like an underwater kite) as an emergency anchor. It's hook-shaped, should dig in quick or snag whatever is available.
    If I was anywhere close to power lines, I could also drop all ballast for an emergency escape. Once past the lines, then it's a challenge to control the ship without having to waste gas.
     
  8. Apr 11, 2019 #88

    Jerry Lytle

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    I may have missed it, but I do not see a calculation for the cubic feet of helium needed to accomplish your objective. Do you have a design weight, including payload and ballast?
     
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  9. Apr 11, 2019 #89

    BBerson

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    I don't advocate no engine or no maneuverability. Actually the opposite. A modern airship should almost certainly include nearly the same maneuverability as an evtol by using powered directional lift. The point about 50 weather balloons (or 500) is the safety in numbers.
    A cluster tied together is a structure also.
     
  10. Apr 11, 2019 #90

    MikeK

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    I hope to lift one person and enough ballast, probably about 50 lbs, to fly one day. Each day any lost gas is replaced, and ballast re-filled. Water makes sense there. I used to have the specs, but have misplaced my notes from the 'Small Blimp Forum'. That was a great forum, good conversations there. When I get closer to actual construction, I'll search for some specs from other ships. That will give me a diameter for the first section.
    My plan is to make a center section, without motor or such, fill it with large mylar balloons and see what it lifts. The center section will be the most efficient. less waste of space. From that test I'll know if the project is feasible, hopefully. Not too much cash invested, and I think I can do the construction myself, no extra help first off.
    Like others have mentioned, a central tube will add weight, but I think I will save weight by having the tube hold the motor, stiffen the ship, and help hold the weight of the cabin. Like Lindbergh's Spirit of St. Louis, I won't have front windows, will have to navigate looking out side windows. Eliminating a conventional cabin saves more weight. Later models can be more user-friendly, but this is a test model.
     
  11. Apr 11, 2019 #91

    MikeK

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    Cost is very important in my project. The heavier envelope, due to the thickness of the plastic, and a motor, controls, even the simplest pilot accommodations, all add up to making the ship larger than a cloud hopper. I'm trying to make this an economy version, if that's possible, while stressing on safety.
     
  12. Apr 11, 2019 #92

    Aesquire

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    A central tube structure is not optimum. A keel structure underneath would be supported from above, all tension members, or in simple terms, ropes, membranes, the plastic sheeting you favor, all pulling up. This puts engines where you can reach them from the ground without deflating or disassembly.

    Further advantage of a bottom structure is short landing gear, your heaviest parts will not collapse the envelope, in the event of pressure loss, and in flight stability is natural and easy.

    See the Norge for an example, you don't need a full length keel to take advantage of the distribution of lift and stiffening effect. Lower pressure difference for the same strength.

    https://en.m.wikipedia.org/wiki/Semi-rigid_airship

    It's all about minimum weight and maximum volume.

    I can see a 40 foot keel, that foods in half, with bolt on trailer wheels for transport. The envelope can fold into/on the keel. A triangular truss could be covered in part with transparent Mylar. Reasonably inexpensive paramotors ( say, 2 ) can be mounted to the keel with nothing more than aluminum tubes to each side, rotating for vectored thrust.

    https://www.space.com/16623-first-powered-airship.html

    If you modernize Giffard's steam powered version by compressing the design vertically, lighter & more efficient engines, etc. You see the lineage to the Norge. Fasten your seat where center of gravity needs dictate, and leave yourself in open air, and visibility will be great! I'm not sure you want to go as retro as climbing back & forth on the keel for pitch control.

    And the Home Despot version could just use a ladder for the keel.
     
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  13. Apr 11, 2019 #93

    MikeK

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    I'm hoping to keep weight down to the absolute minimum, with only one motor, a very spartan cabin, and yes, it would be interesting to see if shifting my weight within the little cabin area centered in the ship could actually affect trim.
    I plan to mount the motor on a section of center tube with flanges, like pipe. The rest of the center tube will have flanges at each section, to be the hub of the whole lashing system, much like a bicycle wheel. Easy enough to dismount the motor, but I don't expect any problems from something as simple as a ducted fan with and electric motor. The motor will be right there in the cabin, everything at the ships center of gravity. Outside motors can get snagged on trees and such.
    I'm also hoping that the flanges at each section will provide mounting points for simple skids on the bottom, something that will not snag on trees.
    With a central cabin, water landings are possible. I like having the option of landing on water rather than it being a problem. I can land, lower the 'chein-de-mer' as an anchor and charge my battery or wait for the weather to change.
     
    Last edited: Apr 11, 2019
  14. Apr 11, 2019 #94

    Riggerrob

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    ..............
    Like others have mentioned, a central tube will add weight, but I think I will save weight by having the tube hold the motor, stiffen the ship, and help hold the weight of the cabin. Like Lindbergh's Spirit of St. Louis, I won't have front windows, will have to navigate looking out side windows. Eliminating a conventional cabin saves more weight. Later models can be more user-friendly, but this is a test model.[/QUOTE]
    .......................................................

    Enclosing the cockpit inside the hull will certainly reduce drag. Side windows are still a good idea.
    To simplify construction, build the cockpit inside the Norge-style triangular keel.
    You probably only need a keel 2/3 the total length of your semi-rigid airship. The keel needs to support the cockpit, engines, landing gear and tail fins.

    Can you picture a keel - with a hinge halfway between the cockpit and tail? To stow Orr the night, you suck out gases with a pump. Do you store gases in high-pressure cylinders?
    Tail feathers pivot to lay on top of the cockpit and the deflated airship slides into a (enclosed) trailer barely 1/4 the total length of airship.

    You might not even need any rigid structure forward of the cockpit. Cockpit gondola depth is often determaimed by the length of landing gear legs.

    The next question is whether to install an optical or electronic periscope to see forwards?
    NASA experimented with under-nose periscopes as part of the American SST program .... back during the early 1990s.
    Simple pivots could also allow you look downwards or aft with the periscope.
    Electronic periscopes add dozens of different angles .... limited only by your imagination ..... and the number of GoPro cameras you bolt to the nose, tail, fins, engine nacelles, etc.
     
  15. Apr 11, 2019 #95

    ScaleBirdsScott

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    There's a small part of me that secretly hopes someone could build a small WWI era Zeppelin replica to bring to one of those dawn patrol meetups. I'll be the guy in the dorsal machinegun nest.

    Seriously though, the best way to monetize and fund such a venture as building an airship and hoping for publicity is to invest in and get good at YouTube vlogging and livestreaming. I don't think the FAA can really be too upset if you make money from ad revenue from videos filmed with your experimental: otherwise a lot of people are in trouble.

    Plus to be honest, the live event type attraction of "yet another crazy guy and his homebuilt [thing] tour" drawing crowds has a very 70's-90's era vibe to it. The idea of car lot stunts and events gathering more than a microsecond's glance seems like fairytales out of my childhood and no more.

    But the weekly wild adventures of a funny guy who has amusing and sometimes insightful commentary about his trials and tribulations of trying to fly across the country at the whims of the weather and his stomach, strapped into a home-made balloon with the liability to crash or deflate or run into these menacing high-tension wires.... has AdSense revenue written all over it.

    And then there's Patreon...
     
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  16. Apr 12, 2019 #96

    MikeK

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    Excellent post, Scott. Long ago I started a book about my adventures in an airship. Perhaps I should pick it up and see just how much I could write. I know nothing about getting published, though.
    Your ideas of blogging and livestreaming are great. The right person in the pilot's seat is the thing. I love to talk and make jokes, but gabbing is a real talent, and not everybody is good at it.
    Keep in touch, your ideas are welcomed.
     
  17. Apr 12, 2019 #97

    MikeK

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    .......................................................

    Enclosing the cockpit inside the hull will certainly reduce drag. Side windows are still a good idea.
    To simplify construction, build the cockpit inside the Norge-style triangular keel.
    You probably only need a keel 2/3 the total length of your semi-rigid airship. The keel needs to support the cockpit, engines, landing gear and tail fins.

    Can you picture a keel - with a hinge halfway between the cockpit and tail? To stow Orr the night, you suck out gases with a pump. Do you store gases in high-pressure cylinders?
    Tail feathers pivot to lay on top of the cockpit and the deflated airship slides into a (enclosed) trailer barely 1/4 the total length of airship.

    You might not even need any rigid structure forward of the cockpit. Cockpit gondola depth is often determaimed by the length of landing gear legs.

    The next question is whether to install an optical or electronic periscope to see forwards?
    NASA experimented with under-nose periscopes as part of the American SST program .... back during the early 1990s.
    Simple pivots could also allow you look downwards or aft with the periscope.
    Electronic periscopes add dozens of different angles .... limited only by your imagination ..... and the number of GoPro cameras you bolt to the nose, tail, fins, engine nacelles, etc.[/QUOTE]
    Thanks, Riggerrob, for the input. This first ship is a workbench, a prototype to test and prove the theory of a plastic airship.
    Modern rear-view equipment in cars is remarkable, I think it would be fine for my ship.
    I'm not worried about deflating or folding the ship. I'll have to find a safe place to park it each night.
    Once the project is self-sustaining a second ship of better design can be built. Hangar-friendly and probably faster, the new one may find a market. It all may just be a dream, but it's a fun one.
     
  18. Apr 15, 2019 at 12:00 AM #98

    Tiger Tim

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    I’m honestly shocked nobody has done a replica WWI observation balloon to take to those.
     
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  19. Apr 15, 2019 at 11:23 PM #99

    Bill-Higdon

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    How about a PKZ-2? http://aviastar.org/helicopters_eng/petroczy.php https://en.wikipedia.org/wiki/Petróczy-Kármán-Žurovec https://forum.axishistory.com/viewtopic.php?t=11351
     
  20. Apr 16, 2019 at 4:39 PM #100

    vhhjr

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    Small is a relative term. Since the lift is a cubic function if you made a 100 ft long version the max gross weight would be about 1/500 of the orginal's 242 tons. That's about 1000 lbs for everything. Throw in a pilot and passenger and some fuel and you're down to less than 600 lbs for structure and propulsion. Then you have to find a rather large building to keep it in and deep pockets to afford the helium, which slowly leaks out of most balloonette materials.

    It would be very special to have your own Zeppelin to cruise around in.

    Vince Homer
     

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