THE AIRSHIP HOMEBUILDER A Bulletin of Airship Design Volume 1, No. 1
December, 1993
Welcome and thanks for subscribing. We have 40 subscribers. That’s a good start. The reasons I started this bulletin are basically three:
1) After five years of gradually sorting through information and ideas – and spending a lot of time and money in the process – I felt that I should go back and organize my information into a logical process, a sort of manual to clarify my own design process.
2) Others have had to “start from scratch” as I did. The airship journals and “picture books” have little practical information on the design of small airships. Wouldn’t it be great to work together, to help each other get a good start and share information?
3) I’m tired of “experts” insinuating that only they know how. I’m tired of others who know nothing thinking I’m crazy. I’m out to prove them wrong and I hope you’ll join me. Some will say that this is an incorrect motive. Yes, but often it’s the only thing that keeps me going.
An individual can design and build a good and safe airship for a small fraction of the cost of a commercial ‘ship. With a bit of ingenuity you can build a better ship than theirs. By this I mean: more comfortable, more controllable, more efficient, and more practical. We will concentrate on the design of one and two-place helium airships.
We’ll begin with a more detailed discussion of the AIRSHIPS page sent in September, here restated in CAPITAL letters. Some of this will be old and opinionated information to you, but I believe it’s important we start off with a common base of information.
AIRSHIPS
AIRSHIPS ARE AIRCRAFT FOR TRANSPORTING PEOPLE OR GOODS WHICH ARE SUPPORTED IN THE AIR BY A LARGE VOLUME OF LIGHTER-THAN-AIR GAS, NORMALLY HELIUM, CONTAINED IN A STREAMLINED “ENVELOPE” OR HULL.
We will discuss size and shape later as part of the design process. Most small airships will fall into the 50 ft (fat one passenger) to 100 ft (slender two passenger) range. Some will see that I sidestepped airships’ only major use at present – advertising. This is for two reasons:
1) Advertising is a commercial operation normally requiring certificated aircraft and this bulletin is not about commercial aircraft. My goal is to promote experimental category airships testing new features. They should not be expected to operate over populated areas or keep rigid flight schedules, as advertisers would want.
2) I personally am not interested in advertising – I’ve had my fill of “businessmen”. My interest is conservation / tourism / underdeveloped countries. Advertising is a limited market based on novelty and not efficiency or practicality.
For a general description and history of airships I suggest you consult a few different encyclopedias, especially the older ones found in public or university libraries. Few libraries have a good collection of airship books, but if you visit several you are apt to find an interesting variety. Some libraries have collections of old aircraft magazines from the 1920’s and 1930’s, which often have articles on airships. I haven’t had time to go through many but hope to be able to share some such articles of interest in future issues. Sources of information will be in the ACCESS section of future issues.
THIS (the helium) HAS THE SAME PURPOSE AS THE WINGS OF AN AIRPLANE – TO CREATE LIFT – BUT DOES NOT NEED FORWARD SPEED OR POWER TO DO SO. THIS “FREE” LIFT GIVES THE AIRSHIP CHARACTERISTICS DIFFERENT FROM THOSE OF AN AIRPLANE, BOTH ADVANTAGES AND DISADVANTAGES.
Two major characteristics separating airships and airplanes and which affect size and speed limitations especially are: 1) the effect of scale and 2) the sources of drag. As we shall appreciate, the volume and thus total lift of an airship increases as the cube of the dimensions. In airplanes the lift increases with increasing wing area, which goes up as the square of the dimensions. It’s relatively easy to “scale up” or “scale down” (as we will be doing) an airship without greatly affecting operation. As airplanes are scaled up something must be done to increase lift. This means 1) higher speed or 2) high-lift devices; and almost always both. These mean longer runways, higher noise levels, more complex construction, and that crashes are nearly always fatal. This high speed does mean that you get there faster (usually in a shorter time than your boring wait at the airport and sometimes before you luggage!) This is the principal advantages of airplanes. I believe that airplane development has reached a plateau, sandwiched between runway lengths and the speed of sound and limited by the fact that fuel must be burned to create lift. Airships have more room for development.
When an airship is flying in level flight all its drag is form drag, sometimes (in airplanes) called “parasite” drag. The power needed to overcome this drag increases nearly as the cube of the speed. (the drag in pounds increases as the square of the speed but since this force is exerted over an increased distance:
Drag in pounds ~ Velocity x Velocity (~ will mean is proportional to)
D ~ V2
Power in horsepower ~ Velocity x Velocity x Velocity
HP ~ V3 (HP ~ force x distance)
Thus at low speed airships have little drag and are very fuel efficient. Also this drag increases only as the square of the dimensions because it is due mostly to surface area. Since lift (volume) increases as the cube of the dimensions, an airship twice as long will have four times the drag but eight times the lift. It is thus twice as efficient in terms of fuel consumed to move the same load. This fact has led to many proposed schemes to build very large airships for cargo or luxury passenger transport, none of which have been carried out so far. If fact if some of the time and money wasted on such schemes had been used to build and fly small airships we could believe that such projects could work. It has been a failure of people, not airships.
I remember reading that Goodyear kept a design team of some twenty engineers working on airship proposals after the Navy ended their airship operations. It is unfathomable to me how such a group could exist for twenty-five years and not even build one airship! What an unfulfilling life. If those guys had any initiative and ability they would have at least gotten together and built one on weekends! (PS: I believe Goodyear company policy forbid them – it would look bad if it crashed or something) When they finally did build one blimp (the GZ-22) it’s
just another boring blimp – to me anyway.
Besides the parasite drag of the fuselage and its accessories airplanes have what is called “induced drag”. This is induced or caused by the creation of lift over the wing surfaces and varies not with speed but with lift created and airfoil efficiency. (Airships have such an “induced drag” when flying at an angle of attack such as when heavier or lighter than the surrounding air – this is normally kept to a few percent of their gross lift.)
Since airplanes must always create lift by forward motion to fly they always have a certain drag to be overcome (and can not stop). Above about 100 mph airplanes are more efficient. Below this speed airships can compete. Remember though that fuel is only one consideration of the operating cost. An expensive airship must fly faster to pay for itself on any commercial route, at the cost of extra fuel – an expensive airship loses one of the principal advantages of airships. Airships are much more fuel efficient and potentially much safer than helicopters. Once airship prices are lowered they will often compete with helicopters. Our subject though is design, not commercialization.
Another area of distinction is flight characteristics. Airplanes have little lag in control response: you push a rudder pedal; it turns. Let’s compare a hypothetical eight-seat airplane cruising at 200 mph (293.3 feet per second – 1 mph = 1.467 fps) to a 200 foot eight-seat airship cruising at 40 mph (58.67 fps). If the airplane is 40 feet long it takes 0.136 second for air to pass over the length of the airplane, as compared to 3.4 seconds for the airship – 25 times as long. Let’s now land our airship at 13 1/3 mph – near minimum controllable airspeed. It now
takes ten seconds for air to pass over the length of the airship. Okay, you actuate the rudder control. That force, greatly reduced because of the low airspeed, must now yaw (turn right/left) a 12,000-pound airship. Theoretically the force on the tail/rudder is proportional to the square of the airspeed and thus only 1/9 of what it
could be at 40 mph. In the typical airship the concentration of car/passengers/motors/fuel near the center does make it easier to change direction. Once the ship’s attitude is altered an altered airflow starts flowing over
the ship. Perhaps five or six seconds later is has built up enough pressure differential to push the ship in the direction desired. Of course by then 1) the wind may have changed and made your control input inadequate or even unnecessary, 2) you’d better be reversing or adjusting your control inputs, or 3) you may have already hit something. If fact if you’re near the ground and want to go up you must force the tail down to alter the airflow to go up. This down force on the tail is seen as extra weight and the entire airship will descend until the new airflow can overcome the down force on the tail. See Airship Aerodynamics pages 46-49, attached.
All these add up to: AIRSHIP CONTROL AT LOW SPEED IS INADEQUATE AND UNPREDICTABLE. THIS AND THE ASSOCIATED GROUND HANDLING PROBLEMS ARE THE MAJORS FACTOR LIMITING THEPRACTICAL USE OF AIRSHIPS. In my opinion IT IS RIDICULOUS THAT A VEHICLE WHOSE PRINCIPAL ADVANTAGE IS THAT IT FLOATS IN AIR HAS NO CONTROL WHEN IT DOES SO. That’s like making a boat that sinks whenever you stop! That would require a docking crew too!
This control/landing/load exchange problem is THE factor that would bring down any scheme of airship transport. Would YOU buy a car with no clutch or brakes that needed to be push started and caught to stop it? True, the machine is simpler without them, but at the expense of a complex ground support system, usually 2 to 3 people for each person in the air. Airships as now built are expensive impractical toys – not a viable means of transport or even sport vehicle. Only their novelty has kept them alive.
Now I know that some of you would tell me that the largest Navy ships, the 2W and 3W, used “mechanical mules” mounted with constant-tension winches for handling and they greatly reduced ground crew. Well the “big boys” today using the 200 foot Goodyear and Airship Industries ships spend at least a half million dollars per year per ship on just the ground crew necessary to handle the ropes. (In case you haven’t heard these ships lease for $250,000-300,000 per month – a high dollar business.) If the “mules” work that great, why don’t they use them? At the LTA Technical Workshop in Weeksville, NC, June ’92 we saw the Sentinel 1000 and its “mules”. They were left parked in the hangar while the ship has manhandled! There was to be another ship there but it had hit a mast truck and deflated!
Unless you have lots of self-sacrificing friends, employees, or servants, you need a “standard” airship about as much as you need an elephant. Incidentally, flying an airship has been compared to herding an elephant – I happen to really like elephants but I don’t have one. I have none of the first above and wouldn’t even consider building an airship unless I thought I had the control problem down to a manageable size. My purpose is not to advertise my control systems; in fact I plan to tell you little about my own airship design. That might limit your creativity and give away mine.
Incidentally, don’t expect to find any interest from the industry in anyimprovements you may envision. If you were spending a million dollars a year to remove blemishes from apples and someone claimed to have a solution to the problem, you would at least investigate his ideas, though they may or may not work. Don’t expect such logic and open-mindedness from airship people. In five years of promoting improved airships I have received only one letter in response – from the now-defunct Advanced Non-Rigid (ANR) group.
Back to our comparison. An advantage of airships is a smooth ride. This makes it easier on passengers and structures. It has been said that the highest “g” force felt on an airship in flight is probably near 1/2 g. This is in agreement with the attached computer projection, courtesy of Mr. Newton. On page 13 the diamond and cross lines show this 1/2 g. Page 14 shows control time history (control response). This is for an airship traveling at 50 knots, but I’m not sure what size ship. We see about a two second lag before any response, with full
response taking about six seconds. As page 15 shows, a pilot control input, in this case pulling out of a dive, will seldom create a force of 1/4 g. The highest loads an airship will normally withstand are in fact landing loads. Bad landings, that is.
I have a airplane pilot friend who whenever the wind is gusty at all will say, “I bet you wouldn’t want to fly your airship today.” Of course I would. I’m no math whiz but let’s do a bit of analysis of why airplanes can have such a rough ride at times, and leave them at least confused instead of contemptful. Let’s imagine our 200 foot airship and our 40 foot airplane hit an imaginary gust of 35 feet per second, as per the attached page 15 of FAA Airship Design Criteria – our page 16. Assuming our maximum g force of 1/2 g, it apparently takes about 8 seconds for
the airship to be accelerated to near the speed of the gust, as we see again by the diamond and cross lines of page 13. Here the “g” forces build up smoothly for about 4 seconds, then decrease smoothly for about 4 seconds – a fairly smooth “bump”.
The airship (in equilibrium flight) was not dependent on an angle of attack to the relative wind for lift. (Relative wind is the airflow direction actually affecting the aircraft, not the direction of flight.) But the airplane is, very much so. An airplane’s lift varies with the wing’s angle of attack to the relative wind. Foregoing accuracy, let’s say that our 200 mph airplane has a minimum airspeed of 1/3 it’s cruise speed – that is 66 1/3 mph. Below that speed the wing will stall – lose lift because the airflow can no longer follow the steep angle of attack of the wing. let’s say the wing needs an angle of attack of 15º to get a coefficient of lift of 1.5 for this minimum speed. Lift on an airfoil increases as the square of the airspeed, for the same angle of attack. So to fly level at 200 mph the airplane has to change the angle of attack to get a coefficient of lift of 1/9 the 1.5 necessary to fly at 66 1/3 mph. For most wing shapes with camber (more curve on the top than the bottom) the then necessary lift coefficient of 0.166 (1.5/9) is achieved at about 0º angle of attack. Now if a gust comes along and momentarily changes this angle of attack, it also changes the lift on the wing. In fact if a strong enough gust to change the angle of attack back to 15º hit, it would create a force 9 times that necessary to lift the airplane – the airplane would feel a 8 g bump! (and likely destruction, depending on its design criteria!). The effect is similar for a downward gust but with negative g’s. A lateral (side) gust would affect the airplane much as it would an airship. We will consider gusts on airship tails later.
Not all airplanes are designed to stand 5.4 g’s-very few for 9 g’s. We see that airplanes can have a much rougher ride in gusty air and thus must be built stronger. Airships can, and indeed must, be built light and strong to have any useful lift and not compromise safety. Both are potentially deadly. Airships are not toys.
While the most dangerous situation in an airplane is loss of control or structural failure, airships are pretty safe as long as you have a fail-safe connection between the passengers and the lifting gas and can control its volume
and pressure, by means of a good envelope or gas bags and good valves.
Of course airships have many similarities to airplanes. I think of them, especially the semi rigids, as an airplane with a bag instead of a wing. For the homebuilder the most important similarity is materials. You can build the majority of an airship from readily available good quality materials from companies supplying the homebuilt airplane market. One well known is :
Aircraft Spruce and Specialty Company
Box 424
Fullerton, CA 92632 USA
Catalog is $5 ($15 overseas airmail)
I suggest you send for their catalog. Prices are usually the best, service is good, and the catalog itself is an education in aircraft construction materials. We will often refer to it later. Other sources will be in the ACCESS section.
EXCEPT FOR SOME IMPROVEMENTS IN MATERIALS, NO SIGNIFICANT ADVANCES HAVE BEEN MADE IN AIRSHIPS SINCE THE 1930’s AND A GREAT POTENTIAL FOR DESIGN IMPROVEMENTS AND NEW USES
EXISTS.
All this talk about “state-of-the-art” is just talk. They are state of the 1930’s art. Despite all the talk about space age materials, their main characteristic is higher prices and there have been little if any improvements in useful lift, reduced drag, etc. A modern polyester envelope will last longer than cotton, but that’s been around for decades really. To me the most impressive thing about the Sentinel 1000, touted as “The World’s Most Advanced Technology Airship” on the cover of a recent Airship journal and by most “experts”, is that the ribs of the tail
fins don’t even line up with airflow! Pre-WWII! Most would be impressed by the laminated, heat sealed envelope by TCOM (of aerostat fame and sharing the same hangar at Weeksville) but those of us who drive Volkswagens (a 1979 Rabbit Diesel with 213,000 miles) have made up our minds not to be impressed by Rolls Royces, meaning that such fabric is out of my, and probably your, price range. And did you hear that they even considered an iron nose weight to balance the overweight tails?
I don’t have the exact areas on the Sentinel 1000 tails, but according to a chart in Pressure Airships p. 83 they should be very near 2000 ft2 total. The same book on page 86 states: “The weights have been kept down to a maximum of .5 lb. per sq. ft.” Another source (1934) gives 0.6 lbs, including rigging. Assuming the “space age” materials and “leap in technology” should give any necessary increases in safety factors, the tails are around 66 to 100% overweight. According to John Craig of Westinghouse the Sentinel 1000 tail unit weighs 2136.8 pounds.
To me the necessary significant advances in airships are 1) more practicality and 2) lower cost. “Modern” airships have neither. Just as not one person (to my knowledge) from the companies building or operating these airships
has subscribed to this bulletin, we can expect no such advances from such ignorant people. I don’t mean stupid. Ignore-ant means purposely not considering what is visible or available. I would certainly subscribe to their bulletins! I hereby salute Tracy Barnes of Blimpworks (Rt 2 Box 86, Statesville, NC 28677) as the only airship builder I know to subscribe. He has built and offers for sale some interesting little airships.
Improvements I would like to see and believe are possible include:
1) no ground crew
2) quieter accommodations
3) faster control response
4) controls that don’t wear you out but keep some feel
5) autopilot
6) less aerodynamic drag
7) less dependence on envelope pressure
8) unattended mooring
9) eliminate “kiting”
10) control at zero airspeed and reverse
11) greater safety against rip-out
12) lower helium loss and contamination
13) better maintenance access (fins, valves)
14) control of “superheat”
15) higher % of useful lift
16) etc.
Once practical and cost effective airships are built, new uses will be possible and practical. Until then the only use found that can afford $10,000 per day is advertising, and that’s a limited market.
HISTORICALLY AIRSHIPS HAVE BEEN DIVIDED INTO THREE BASIC AND SOMETIMES OVERLAPPING CATEGORIES: NONRIGID, SEMIRIGID, AND RIGID. NONRIGIDS ARE DEPENDENT ON THE AIR PRESSURE IN INTERNAL AIR BAGS CALLED “BALLONETS” (pronounced bal-o-NAY) WHICH KEEP THE MAIN VOLUME OF HELIUM UNDER SUFFICIENT PRESSURE TO MAINTAIN THE AIRSHIP’S SHAPE. THERE IS NO INTERNAL STRUCTURE, THOUGH SUSPENSION CABLES ARE OFTEN USED TO SUPPORT THE WEIGHT OF THE CAR FROM THE TOP OF THE ENVELOPE AS WELL AS THE BOTTOM. MOTORS ARE ATTACHED TO THE PASSENGER CAR, AND TAIL FINS FOR STABILITY AND CONTROL ARE TIED TO THE REAR OF THE ENVELOPE. NOSE RIBS OR “BATTENS” HELP MAINTAIN THE NOSE SHAPE AND ALLOW CONNECTION TO A MOORING MAST TO ANCHOR THE AIRSHIP AFTER LANDING. NEARLY ALL RECENT AIRSHIPS HAVE BEEN NONRIGIDS. THIS DOES NOT MEAN THAT THEY ARE INHERENTLY BETTER.
Don Woodward of AEROSTATION reminds me that not all nonrigids use ballonets. He mentions that “The British “Nulli Segundus” (190?) had its envelope made of several layers of goldbeater’s skin, which was elastic enough for whatever heights it could reach. More important, and more interesting, were several small single-seaters built by Zodiac” with “pleats on the sides, laced with bungee cord, which permitted the volume to expand as the craft ascended, and recompressed the gas as it came down . . . Fatigue of the bungee cords required quite a lot of maintenance.”
Very interesting. Goldbeater’s skin is a thin membrane created – not by man of course – to protect the bloodstream of cattle from any escapes of methane gas from their methane-digester stomach. Thousands were necessary to line the gasbags of most rigid airships. The U.S. built Akron and Macon used instead a “gelatinized latex” rubber. Despite all the talk about modern materials, remember that hundreds of successful airships used natural rubber to make them gas tight. Don’t overlook it. In fact I have about 100 rubber (Hevea brasilensis) trees on my farm in Costa Rica, which are not being tapped and should provide near 1000 lbs of rubber per year.
Goldbeater’s skin is as gas-tight as the best available materials today and it stretches too! Tracy Barnes (Blimpworks) has built airships of a thick (very tough) urethane film that stretches, too, with no ballonets. For all practical purposes some allowance must be made for helium expansion and contraction, with any
type of construction. We will get into pressure, shape distortion and materials later.
Notice the bungee cord system used on the Oehmichen Motor-balloon – see page 40. This was how the Piasecki “Helistat” should have been instead of the fiasco it was. It succeeded in using a free hangar, free envelope, free helicopters, and used aluminum irrigation tubing to create a 34 million dollar accident waiting to
happen – the worst rip-off in LTA history. Am I correct?
The two things I most dislike about nonrigids are:
1) Component location. Those noisy, heavy, and dangerous motors are always fastened to the car. Lacking any framework that’s about the only place you can stick them with little danger of them flopping around and destroying the envelope. If they or the props can be vectored (tilted) they can be useful there to
help in vertical control, but because of the gyroscopic forces involved that can be a slow process. I believe it takes 9 seconds on the Skyships and took 90 seconds on the Akron/Macon. That’s not nearly fast enough to get out of an emergency situation. Don’t overestimate vectored thrust. Many do. BUT, on small ships vectoring would be quicker with smaller props. Add this to quicker control response (roughly twice as fast as the “big Boys”) and vectoring is potentially much more useful in small ships, but should be approached carefully. Two bladed propellers (normal for small engines) have a terrible vibration when you tilt their axis of rotation. Three or more do not but still have a sizable but even resistance to vectoring. This is hard on crankshafts and could be catastrophic if you break a shaft in flight. Steve Garner of Memphis Airships built a small ship with two 9 HP
Rotax engines on a rotatable shaft and said it vectored fast. He also said that they had problems with both crankshafts!
Well, back to nonrigids. With central motors they’re of little use in pitch (nose up/nose down) or yaw (turning) control. All that weight of car, motor(s), fuel, landing gear, and passengers concentrated near the center means that what is left (envelope and tails) is pretty lightweight and easily thrown around by gusts. You have an unstable airship, the envelope trying to go every which way and the car trying to stay in one place. Among my meager credentials as an airship designer, I have flown in one airship, an ABC Lightship in Kissimmee, FL. This is usually THE place to get a ride. Kissimmee is SE of Disney World and usually has a Lightship and a Sea World ship. Half hour rides (1991) were $75 and $85 respectively. The Lightship phone number was (407) 841-UPUP = (407) 841- 8787. I have no great desire to fly in other ships, especially not at that price. I had the controls for about 20 minutes. The wind was gusty and the ship pitched and yawed what seemed to be 30º in any direction. It was all over the sky and yes was much like herding an elephant. The sensation is very much like the suspended cable cars or “aerial tramways” at amusement parks or to mountaintops, enjoyable with nice views but unstable and noisy.
2) That darned pressure. You have to constantly baby a nonrigid. Pressure is usually supplied by the prop blast in flight and electric or gas-powered fans on the ground. It is watched constantly, which may not be so bad if you
already have a 20-man crew, but for me would be impossible. You obviously won’t fall from the sky without it (unless its loss is due to a helium leak) but you do lose control because the control cables go slack, etc, and the bag would need a thorough inspection afterward. If you don’t fly everyday and don’t have a 20 member “circus” it can be a very negative aspect. I want an airship that I can leave unattended at the mast or in the hangar for days at a time and that is “friendly” to improved control systems and passenger comfort. To tell me that I had to build a nonrigid (as some have tried) would be to tie my hands. While some of you have already seen it, I am appropriately including a copy of my paper “A New Look at Semi-Rigid Airship Construction”.
SEMIRIGID AIRSHIPS UTILIZE A BOTTOM FRAMEWORK TO STRENGTHEN THE ENVELOPE AND DISTRIBUTE LOADS BUT STILL RELY ON A SLIGHT PRESSURE TO MAINTAIN SHAPE. THE FRAMEWORK ALLOWS MORE FREEDOM AS TO LOCATION OF COMPONENTS AND DESIGN INNOVATIONS.
RIGID AIRSHIPS USE A RIGID FRAMEWORK NORMALLY COVERED WITH A FABRIC SEPARATE FROM THE INTERNAL GAS BAGS AND DO NOT RELY ON PRESSURE TO MAINTAIN SHAPE.
AGAIN, VARIATIONS ARE POSSIBLE.
We will of course analyze the “rigidity” factors later. To those who say you can’t “reinvent” the airship, look at the “New Technology” Zeppelin (see following page). They have adopted a unique construction system and control
improvements (I do not say solutions!). That’s the kind of open-mindedness we need to promote. I don’t mean that you have to build this or that kind of airship. Those with an open mind will consider any airship design that works. The Italian semirigid “Omnia Dir” of 1931 was the only airship to achieve successful control by air jets. Most assume you can’t build a small rigid airship, but such a one-seat ship was built and flown in Utah years ago. Keep an open mind.
The airplane homebuilders are the leaders in innovative, fun and, yes, high performance and economical (= practical) airplanes. Airship homebuilders, admittedly an almost non-existent group, can do the same! In fact because the “experts” have chosen to ignore us we have the unique opportunity to design and build airships that might put theirs to shame. Of course they’ll still try to ignore us.
PRESENT AIRSHIPS HAVE NEGLIGIBLE CONTROL AT LANDING AND TAKEOFF (ZERO AIRSPEED) AND MUST THEN BE HANDLED BY NUMEROUS MEN USING ROPES ATTACHED TO THE ‘SHIP – USUALLY 2 TO 3 GROUND CREW PER USEFUL PASSENGER. MOST OF THE NEAR 20 AIRSHIPS NOW FLYING HAVE VERY HIGH PURCHASE AND OPERATING COSTS. A GREAT POTENTIAL EXISTS TO LOWER AIRSHIP COSTS AND INCREASE THEIR VERSATILITY. THESE TWO FACTORS WILL BE EMPHASIZED IN THE AIRSHIP HOMEBUILDER.
The Goodyear size ships (based on the Navy “L” ships of the early 1930’s) use about 23 as a total crew, including I believe about 16 to man the handling lines and car rails. It’s safe to say that they spend at least 1½ million dollars per year per ship due to inadequate control and mooring systems. They are said to cost near 5 million dollars; 1½ million for the smaller 5-seat Lightships. No wonder there aren’t many airships. When one of these big ships hits something on the ground or has to intentionally rip-out due to very bad weather on the ground they often need a new envelope. We read that this costs 1 million dollars. Okay, that leaves 4 million dollars for 1) a cabin with twin engines, one landing wheel and fuel tanks 2) some large airfoils – the tail fins 3) a few hundred feet of cables, etc. 4) a giant umbrella – the nose battens. These components are comparable in material
cost and construction complexity to a twin-engine airplane of the same passenger capacity, which costs 1/10 as much. The airship is a rip-off.
I expect material costs of my own ship to be about $25 per pound empty weight. That is using aircraft quality components (not always necessary) and includes some high-dollar items such as instruments and carbon fiber. That means about $20,000 for my 800 pound two place ship, not counting tools, experiments, shop expenses, etc. – the part that doesn’t fly. I could buy a Cameron DG-14 one-place ship for I believe $240,000 or a Thunder and Colt GA- 42 two-place for about $500,000. What a deal, huh? And these are mediocre, impractical airships. My personal opinion, of course.
Let’s just say that the big ships cost $50 per pound and weight 8000 pounds empty. That’s $400,000 in materials. Are they worth over 10 times the material cost? I estimate 4 hours per pound of weight construction time for my
first ship. Mine will not be a very simple ship and will perhaps have more innovations than all the ships since the Hindenburg combined. Maybe it will really take 6 hours per pound? The Akron/Macon and Hindenburg/G.Z.II took about 6 hours per pound, as do the most complex homebuilt airplanes. If the 8000 pound ships being considered also took about 6 hours per pound to build then 8000 lbs x 6 hrs/lb = 48,000 hours. At $20 per hour let’s say $1 million. Subtracting the $400,000 materials and $1,000,000 labor from the $5 million price gives
$3,600,000 for the part that doesn’t fly. It would seem that either they don’t know how to build airships, they don’t know how to run a business, or somebody has a Swiss bank account.
Yes, a great potential exists to lower airship costs and increase their versatility. I cannot claim to be the best equipped or qualified person to write this bulletin of airship design. But I feel someone should do it and some fresh ideas are definitely needed. To build an airship is no small undertaking. Not that it’s impossible to build your own aircraft – this is shown by the literally thousands of homebuilt airplanes of similar complexity. The pity is that it has been so difficult to work out the design, financing and construction of such an unusual aircraft as the airship that most have settled with building something that they know will work, though not that great, as evidenced by the nonrigids now flying. My hope is to give you enough information that you will not have to worry so much about the basics and can focus also on improvements.
I was hoping to start the design process with envelope shape considerations in this issue, but due to time and space limitations and the fact that I’m waiting on some material I’ve ordered we’ll start next issue (March). As this “goes to press” – the local newspaper’s copy machine – I notice in the newest “Aerostation” magazine that Memphis Airships is filing for bankruptcy. I will have info on Aerostation and other magazines and organizations in the next issue.
Until next issue, best wishes;
Jesse Blenn