Airship’s Fighter 3rd test flight

Our Silence Twister is put through its paces by test pilot Jim Guldi in our longest flight to date, about 1.2 hours. The GoPro was mounted aside the headrest in this 2.5 minute summary of the launch and flight. He does a high-speed low pass at the end.

USS Long Island -Theory and Design Part Four

So now Long Island is structurally ready for the screen: 944 feet long, 160 feet in diameter, four engine cars, strong fins, double-deck control car. Now we have to enter completely new territory, remembering the USS Akron and Macon design only had a airplane facility added, after the major design was mature. The resulting heavy, complex truss necessary to spread the loads across the main rings forming Bay VII added no real strength to the airship’s overall structure.

In this case there was no extensive German experience to use as a reference. VADM C. E. Rosendahl recalled the side keel design and the after-the-fact hangar bay, writing, “Having two side corridors did add structural strength, and provided housing for the engines and quarters for the crew. However, they resulted in certain operational disadvantages, and the conventional Zeppelin centerline corridor along the bottom represents a far better solution… For one thing, it was unnecessary and costly to provide, in the airship, an inside hangar capable of housing all five of the ship’s planes. Much simpler facilities would suffice… Such innovations in our 1927 design were daring, in a way, and understandably motivated. But having tried them, we should not repeat them.”

Indeed, a ship designed from the outset as a flying carrier would surely use its heaviest, strongest structural member to handle its toughest loads. Dr. R.K. Smith wrote, “The ZRCV’s nine bombers were stowed in tandem beneath the hull, each plane had its own trapeze; all could be launched within a few seconds. This stowage arrangement dictated a strong keel in the airship, and thus a return to “conventional” airship construction…” This makes perfect sense.

In fact, research for a wartime article in POP MECH magazine adapted one of the Goodyear-Zeppelin designs for the airship-unfriendly vertical frame of the front cover. Herein we see six of the LZ-130 style power cars. We have some sort of  a two-place airplane dropping off, which one could take as a shrunken version of the SNJ (Army T-6) trainer.

Check the size of the pilots in the magazine cover illustration vs. the crew aboard the USS Wolverine next to the SNJ, whose wingspan was forty-two feet (!) The artist sought to make it fit.

There are two major problems with this vision:

First, there is no evidence the Navy considered a purpose-built two seat “miniature” hook-on design. The drawings inside the magazine leaned more toward a full size airplane, arguably a BT-13 or SNJ. As we shall see, packing these completely inside a keel just won’t work, even in a much larger airship.

Why? Remember the square-cube law. Nearly doubling the Akron-Macon 6.5 Mft3 to Long Island’s 12 Mft3 increases the diameter only about 27 feet. That does not translate into a huge area increase in the keel quadrant—perhaps 13 feet on a side.

Additionally, as the second point, the Macon “post-mortem” report argued against housing full sized (particularly larger radial engine, two-seat) airplanes inside the hull, for good reason. The F9C-2, N2Y-1 and slightly trimmed Waco were employed because they were available, and just happened to fit through the USS Akron’s door. Once inside, space was so tight even these small airplanes had to be canted, then eased into the corners. Akron never got to use the aft positions owing to a girder conflict, fixed for Macon then under construction. A completely different arrangement is called for.


We’ve done a lot of study on the hook-on airplanes and see a more logical evolutionary development. In the timeline that had not seen the three major accidents that hobbled airship technology, we think Rowan Partridge’s vision of the airship and her bombers being protected by small, highly maneuverable fighter planes is quite logical—and makes great action visuals for the movie as well.


This dual-plane vision was somewhat predicted by Goodyear-Zeppelin, with the ZRCV-like design above, drafted but not publicly detailed during WWII. This 10 Mft3, 16-bay concept, originally designed to tolerate helium, suggests the airship’s largest diameter sections could carry small fighter aircraft along with the bombers. The extra two million cubic feet in our Long Island will seek more of the same; we see the airship carrying nine SBD-Z1s, and eight fighters.

Beginning with Long Island’s bay depth, and moving to the largest-diameter four center bays, we can design a set of flip-up doors that adjust the existent intermediate frame spacing. (Plan shown) Once the trapeze is accommodated, doors large enough to clear the fighter’s tail will suit the SBD fuselage as well.

Then the center four need only two smaller flip-up doors to clear the fighter’s wing tips, allowing it to be brought completely inside. (Above, plan) This drawing shows the outer beams only. In the next drawing, adding the four keels and outlining some of their fuel tanks partially obscures the fighter in this view, looking down through the gas cell. Hooked on, the fighter is raised to a point just above the curved monorail track, and the dolly moved to pin the prop guard just forward of the hook.

The next-to-smallest bays in the extreme forward and aft will not be tall enough to accommodate the fighters. By enlarging the door structure slightly in these two bays, one SBD could be brought higher into the ship to allow access to the underside—to re-arm, or re-attach wheels and hook for runway landing or flattop liaison.

With the keels well into the main ring area, the most tapered-shallow airplane bays fore and aft will only allow the entry of the SBD fuselage up to its horizontal stabilizers. We think this the best bay for the winched accessories: the pilot retrieval basket, and the spy car. Of course either being deployed would call for that bay’s airplane to be launched.  That SBD could be “parked” on the fin’s perch or the car’s perch while the basket or bridle was being used.

A fully loaded midship bay looking down through the gas cell all but obscures the SBD hanging outside (above plan), but shows the fighter planes canted to easily fit outboard. The SBD hook and propguard is not intended to ever reach the monorail in those four center bays, and there is no monorail in the extreme forward and aft bays.  During transits the SBD’s hook release handle would certainly be secured with a pit pin to prevent inadvertent release during egress.

Looking from forward (plan view) the fighters would actually be canted for storage with respect to the keel, only facing forward as seen here when the SBD was gone and they were positioning for launch or after recovery. The trapeze would be winched into position to prevent a conflict with the fighter’s wingtips.

(Below plan) As seen from the side view, a centermost bay is recovering an SBD while the fighter is about to be dollied into stowage position. Outboard keel and ballast bags not shown for clarity.

A detail insert shows the fighter plane handling dolly (above). Each of the duly equipped four bays’ twin dollies are slightly bent to ease travel along the curved I-beam. A bearing plate allows rotation to allow the wings’ tips to clear the stowed SBD canopy.  Just as on the Akron/Macon, the fighter plane’s weight was transferred to the assembly by bringing it up the trapeze to near full height, then pushing the dolly and its bearing-mounted dual dangling arms along the curved I-beam to straddle the aft prop guard mounting. Reaching down from the platform above, a crewman would insert a fat load pin through one arm, through the airplanes’ hook mount structure just forward of the hook, and then finally through the other dangling arm. The load pin would be secured with a spring clevis.  Then the cockpit hook release would be tripped to allow the airplane to fall onto the load pin. With hook wide open, the trapeze would be winched up out of the way, and the little fighter dollied outboard for storage. Once outboard, aft and canted clear, the trapeze would be winched into position for the next evolution.


The ZRCV could have been built even as late as 1942, and certainly would have if FADM King had been able to push it through. Not suffering from the manpower shortage on the US coasts and shipyards, ZRCVs could have been assembly-line produced for deployment with the fleets on both coasts. Captains Barkely and Buckley told us in their book so long ago: since the Germans had been making a new Zeppelin every six weeks back in World War One, our Liberty-ship-every-three-days capability could easily have supplied a fleet of hydrogen-borne ZRCVs to hasten the end of the maritime war.


Our flying carrier USS Long Island is ready for the screen.  All the years of toil and treasure – not to mention the lives of so many people – need not be relegated to the dustbin of history. Let’s allow our audience the chance to see what might have been!

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USS Long Island—Theory and Design Part Three

LOOSE BRIDGEWORK

The altitude pilot’s position in a rigid airship is greatly under-appreciated. When referred to simply as the “elevator man,” we miss the fact that only the most experienced hands who had developed a sort of sixth sense for attitude drift could hope to preempt pitch changes with orchestrated elevator tweaking. In any design, the altitude pilot’s outboard facing position is not negotiable, be it the Brits’ right hand drive (above) or the standard Zep port side.

Left- or right-hand drive elevator, helm perfectly center or off-center, bridge design was fairly consistent from R.100 (upper photo) to LZ-130 (lower photo).

Akron/Macon three-compartment bridge/car (diagram) retained the earlier Zeppelin port side altitude pilot wheel and centerline rudder wheel. Its aft center compartment was also a throughway from the folding accommodation ladder to a fixed ladder leading up to main ring 35, which gave access to the outboard companionways, centerline passageway and officers’ cabins forward. (Nothing in the literature suggests the space labeled “photo lab” aft of the radio room was ever finished as such.) The bridge/car was made more comfortable by engine manifold-heated ducted air.


We see nothing wrong with the Akron/Macon bridge design. One could easily add later 1930s enhancements, such as the lifesaving radio altimeter to supplement the annoying whistle of the sonic altimeter. They were already installing other advanced electronics in 1934, such as the radio direction finder.

For an airship designed from the outset as a flying carrier, as suggested by C.P. Burgess, a “pri-fly” for airplane control would be a necessary design element, in a second deck below.  Macon officers had tried to expand the position of senior aviator to also direct the airplanes. Such a billet would  certainly been on the duty roster of the ZRCV.

This greatly enhanced job/post of “Air Boss” would work hand in glove with the bridge, just as on today’s flattops. That station, for which we can borrow the modern term “pri-fly,” would need a commanding view of the keel to direct airplane launch and recovery. Effectively, he would serve as local Air Traffic Control.

Meanwhile, the Akron/Macon accommodation ladder never seemed quite long enough; our Long Island will have a reinforced double extension accommodation ladder. Like the ZRS ships, ladders will lead straight up to the hull through the pri-fly and bridge. A slightly retractable wheel, replacing the bumper bag  and similar to the LZ-129/130, would allow the Americans the luxury of more easily controlled wheel landings, which the Germans came to appreciate – then unfortunately set aside by request in May 1937.

This lower deck also would be the logical if somewhat exposed position for the radio room, since much of the ship’s communication would be with her airplanes. The ship’s radioman and/or navigation position would evolve to include scout airplane report coordinator, in a compartment with plotting board – in other words, a Combat Information Center, more advanced than the evolving ZRS-5’s.


MOTOR-VATION

Few engines were ever designed specifically for airships. Long before LTA had to make do with adapted airplane engines, the maritime industry supplied much of the motivation.

The mighty 12-cylinder Mybach VL-2 (photo, awaiting installation in Akron) powered LZ-126 and LZ-127 as well. Its 550 horsepower was too little for the LZ-129 and would have been too weak for the 10 Mft3 ZRCV, let alone the 12 Mft3 Long Island. In spite of the lure of America making a flying weight diesel engine ala ‘129-130, it is most likely any ZRCV design would have used the same gasoline as its airplanes, avoiding the complexity of a dual fuel system.

More likely, American industry, building ever larger and more powerful radial engines for new all-metal high-performance airplanes, would have gotten the contract. Macon’s replacement engine from Packard, on the test stand when Macon was lost, might have powered six engine cars for a ZRCV or could have be put in tandem for the Long Island cars.


Of greater importance to the movie is what the engine/drivetrain would have looked like: internal ala ZRS-4 &-5, or external car/pod mounting.
R.101’s power cars (photo above) contained both a Canadian railroad diesel engine and its gasoline starting motor.

Akron/Macon’s keel-integrated engine rooms (photo, on a combined structure/drivetrain stand) are not very visually appealing. Then there is the vexing question of “vectored thrust.”


VECTORED THRUST—IN 1906

“Vectored thrust” is an arrangement to swivel the prop to push the airship in a particular direction. We are not sure it was a new idea when seen on the Melvin Vanniman airship America in 1910. The British R.9 was so equipped (photo).

Even the Germans had even tried swiveling props, briefly on LZ-127 (LZ-Archiv photo) but rejected the idea. Remembering the Mybach VL-2 had dual cams, so as to be reversible, the ability to push or pull the ship in any direction was a capability not lightly discarded. (Pity the Italians, without revering engines or gearboxes, had to stop engines and send a crew out on the stanchions to change props!)

Yet Rosendahl lamented, “That German airship men did not like the AKRON-MACON design is not exactly a secret…These two airships were equipped with swiveling propellers in order to provide vertical thrust up or down; however, the modest advantages derived therefrom were not worth the cost and complication. The location, in line, of the four propellers on each side, proved inefficient and a source of serious vibration.” The Macon “post-mortem” recommends deleting the complex geartrains in all but perhaps the foremost engines.

WATERWEIGHT

Also of importance for art direction is the question of the water recovery equipment’s appearance. One can barely see the water-weight recovery system on Hindenburg—a thin line amidships at the equator. It was a rain gutter that collected runoff when the ship was run into the clouds to make up some burned off fuel weight.

The weighty complexity of condenser stacks and associated plumbing (early Akron, photo) would have been the first tonnage deleted in a conversion back to hydrogen; indeed, #3 and #4 were removed from Macon to save weight in 1934.

Nonetheless, the American ability to recovery water from exhaust was so desirable the Germans might eventually have added H2 to their diesel fuel to recover lost fuel weight even before LZ-130. Remembering the Lakehurst innovators had developed and fitted the Mk4 condensers to Akron by ‘33, designers were advancing toward solving the problems of soot buildup, improving the weight ratio and the efficiency.

The logical solution is found by looking to the last rigid airship, LZ-130. Of his many wonders, many of which we may never appreciate, most easily notable are his engine cars (photo montage). The first and only “tractor” configuration for a Zeppelin, the barrel/pod-like power cars conceal several advanced engineering developments. Initially equipped with the same double connector and the stacked two-blade props, the marvel-in-disguise cars show cooling radiators forward. However, these are more complex than meets the eye, for they contain oil cooling and exhaust condensers as well. Also, the water recovery system was wholly enclosed in the cars. A shaft-driven turbofan  helped rush that airflow out with such thrust it was said the drag penalty was wholly paid back (!)

Though arguably never developed without the LZ-129 fire, since the necessity to limit static discharge and also recover water might not have evolved, we think it an acceptable stretch of the truth that such technology was created anyway. Of course his syn-diesel had to have hydrogen added to make water recovery possible, but perhaps gasoline versions would be selected by the US had the Packards made for Macon not evolved into larger engines. Zeppelin engineman Eugen Bentele told the producer the German engineers never really solved the soot problem, but by the time of the Long Island, and her gasoline engines, perhaps a less strenuous method of cleaning out the carbon would have been developed.

Later flights featured single-hub, laminated three-blade props that improved efficiency (photo). These raised the bar for future rigids.

In Part 4 we will see a magazine cover that suggests such cars would be part of the ZRCV, so these power cars on our movie airship are not much of a stretch. Either way, one has to acknowledge it’s a lot more visually interesting for enginemen to loop an arm around the station and egress the engine cars via the ladder!

So we have the most important design details of our USS Long Island ready for the screen: 944 feet long, 160 feet in diameter, four engine cars, strong fins, double-deck control car.

However, that was only the foundation. USS Long Island, of course, is a flying aircraft carrier, and we shall make her so, in Part 4.

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The USS Long Island—Theory and Design Part Two

EVEN DOZEN OR SWEET SIXTEEN?

Though seemingly outwardly similar, LZ-129/130 and ZRCV had more bays & gas cells than the slightly smaller ZRS-4 and –5. In any rigid, a smaller number of larger cells offered greater lift, via less structure and cell weights. A larger number of smaller cells made for a stronger if possibly heavier structure, and greater survivability in case of battle damage or stuck-valve type cell casualty.

We will opt for a larger number of cells with the knowledge the 1937 designers could thereby make much stronger cell bays via tighter intermediate frame spacing. Therefore Long Island will return to 16 cells in an equal number of bays, numbered from aft to forward.

SPINELESS OR BONE-IN

Some sort of backbone has been featured in a good many airships which, from the turn of the century, have sought to smear the pinpoint loads like petroleum fuel tanks, aviators and engines across the feeble gas bag(s). A notable exception was R.101 herself, which had no keel at all in the conventional sense. (Refer to the previous post, some fuel tanks located in the rings themselves.)

Photo: R.36’s keel demos its hospitality to weight-extremes of gasoline cans and ballast bags alike.  A ZR-1 crewman would have felt somewhat at home in this similar arrangement.

ZR-3’s heavy centerline keel (photo) helped carry an airplane trapeze later in her life. The next Zep,  LZ-127, did not have so many heavy gasoline tanks testing his keel strength. The “weightless” gaseous fuel was carried in fabric cells below the hydrogen cells. The heavy gasoline carried aboard was used as trim.

LZ-129’s giant diesel tanks (photo) hung from his heavy keel. This strong keel bent, but did not break, during his fatal fall.

The Arnstein Goodyear-Zeppelin design won the US Navy approval in part because of its three-keel design. The triangle of reinforcement they offered eventually lead to the incorporation of not just fuel, oil and ballast loads on the two lower keels, but the airship’s propulsion plants as well, while offering crew access to a large cross-section of the interior.

While the ZRS 4/5 upper keel carried no concentrated loads, its walkway provided access to the airship’s topside, the logical mounting of gas valves used for maneuvering and to prevent overpressure during extremely rapid altitude changes. Thus Akron and Macon had direct valve access without any complex tower or center walkway arrangement. The two forwardmost valves were athwartships, off the centerline keel, but were still reachable via their main ring (photo).

This useful upper keel appears to have been retained on ZRCV.

The centerline walkway created by the LZ-129’s spoke-like rings’ construction (photo) permitted access to gas vent towers, but not all valves could be easily reached by the crew.

On the first return trip from Brazil, a valve stuck open and vented tens of thousands of cubic feet of hydrogen. The riggers could only watch as the cell went limp right up to the level of the stuck valve. Mixed in outside air, it dissolved, disbursed and, when it found enough oxygen in the static-rich atmosphere at that altitude, doubtless burned with great ferocity. No one noticed, since the heat generated was headed upwards, and most of the energy would have been absorbed in the air’s water vapor.


Selection of a keel design is also dependent on how much non-gas space is expected to be habitable within the hull.  In this faint original print, the Akron / Macon Bay VII airplane truss appears to be quite intrusive.

How much room can be efficiently chiseled out of the gas cell space? The passenger sections of the R.100 and R.101 (below) were arguably not quite as gas-capacity-efficient as the LZ-129 and –130.

 

 

 

 

 

 

 

With the ZR mission emphasis switching from scout to attack, it becomes obvious an airplane with the wing area capable of supporting two-man, three-gun crew and a 1,000 lb. bomb simply would not be practical to stow inside an airship. At the same time, the only practical way of also carrying small fighter planes would be to stow them inside. A compromise between multi-story luxury compartments and more functional keels would have been reached.

Therefore, we settle on one 4-truss centerline keel, and one “conventional” V-shaped upper keel for our USS Long Island design. Our wide, quad-reinforced lower keels will carry the heavy and dynamic loads of fuel tanks, ballast bags, and transitory airplanes. The upper keel will allow access to gas valves,  as well as topside navigation & defensive stations.

CHASING TAIL

Rosendahl continued, “…German airship men did not like the AKRON-MACON design … they did not like the idea of the considerable unsupported length of upper fin forward of its attachment at Frame 17-1/2, a frame they considered weak anyhow.” Author Thom Hook followed Rosendahl’s unpublished lead in suggesting Akron was lost for the same reason—tail structural failure and resulting gas cell loss—as Macon.

In disagreement, Jeffery Cook’s intense study of airship empennage set the LTA world abuzz, writing:
“It has been a widely held belief that Goodyear-Zeppelin’s failure to include one or more cruciforms to support the fins was a fundamental flaw in the ZRS-4/5 design… The Germans had used cruciforms in all of their ships since 1915, without any fin failures, and they (along with many other LTA experts and enthusiasts over the subsequent half century) believed that the American ships’ deep frames were not strong enough to take the place of the cruciforms. The Zeppelin Company also pointed to the fact that Goodyear had assumed the same loads for all three upper fins. In their years of operating experience, the Zeppelin Company had learned that the upper fin of an airship should be designed for higher loads than the other fins… The fact that no such allowance had been made in the ZRS-4/5 fins, and the Macon girder failures in April 1934, led the Germans to feel that the American ships’ fins and aft hull structure were under-designed for the loads imposed on them… Both of these arguments are unsupportable… Arnstein was intimately familiar with German practice, for he had helped to establish that practice; had he felt it necessary to use cruciforms or increase the strength of the upper fin, he would have done so at the outset.”


Meanwhile, belief that stability could be enhanced by increasing the fin area from the German originals was not followed with R.101 (photo). Critics charge R.101’s fins and control surfaces were undersized, but at least structural strength seemed adequate.

Arnstein’s winning proposal for BuAer Design #60 (photo) featured large fins which, in deepening for Design Change #2, lost their root main-ring support.

LZ-127 (Roy Gibbens photo) shows the most successful fin design, if by 1935 disfigured with the symbol of the national socialist party paying the operating bills.


As Jeff Cook’s study revealed, Akron/Macon’s production tails were designed with incorrect pressure distribution data which directly caused the horizontal fin failure in flight over Texas and the Macon’s loss from upper fin failure. C.P. Burgess’ 1938 ZRCV design showed both this real world education, and studies completed after Akron’s loss. Our movie effort is also blessed to have Jeff Cook on the design team.

Jeffrey Cook’s USS Long Island fin structure concept (above) reflects studies that designers would have possessed even if Macon had not been lost in 1935. Unlike the ZRS-4 & -5 fins that were basically enlargements of the LZ-126 fins, this design has its structure in the right place to handle flight loads. Of course, like the rest of the structure, it would also benefit from the stronger 24S aluminum and improved spot-welded construction techniques.


Back up at the bow end, the LI structure design would have no need to deviate from the accepted practice of supporting the three-winch mooring system and internationally-accepted “plumb bob” sized to fit all the world’s mooring cups. The diagram shows this design in relation to one of the standard “Empire of the Air” mooring towers.

Of course a regular bow boarding door connecting to the keel walkway is a must—perhaps not as finely finished out as the R-100 seen here (photo).

Likewise, a forward lookout platform would be fitted above the winch room, though on our warship it would be equally useful for shooting at attacking enemy planes via a machine gun mount, as it would the stars with a sextant (as on R-100 in the photo).

Now we have the hull structure design. We follow the recommendations of the Macon “post-mortem report”

and here she is: Length, 944 feet; maximum diameter 160 feet. 16 bays housing 16 gas cells totaling 12 Mft3. Our USS Long Island could have been constructed in the Goodyear-Zeppelin airdock, even if the major assemblies had to be built by the Naval Aircraft Factory and trucked over to Akron, ZR-1 style. While it would not fit in the Lakehurst hangar owing to length, the rarely used roadside doors could have been removed and the hangar extended.

Admittedly it would not have fit in Scott Field or Sunnyvale Hangar #1 owing to height, so, as the novel suggests, a second hangar would have to have been built at Sunnyvale, perhaps in the current footprint of the WWII era timber hangars 2 & 3.


Command bridge, crew facilities, airplane handling and other parts of the design will be laid out in follow-on posts.


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The USS Long Island—Theory and Design, Part One

Unlike a different outcome to the Battles of Thermopylae, or Hastings, or Gettysburg, a dreamer dabbling with rigid airship history has a shorter working time period, and limited technological options. Narrowing our focus from the generally possible to the more likely scenario is much more complicated. Some have already speculated what might have happened if Captain Pruss had simply refused the American’s request for a “high” landing: LZ-129 could have made an ordinary on-the-wheel touchdown on May 6, 1937. A world in which Hindenburg’s return with 70 passengers on May 9th in time for King Edward’s coronation, accompanied by the routine launch of Graf Zeppelin on his scheduled May 11th South American run, has long generated speculative debate. Remember that, even after the fire, the Germans had started on LZ-131, whose extra bay would have given that airship a volume about 9 Mft3.

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As we have seen on the ZRCV page, logical arguments for much larger airships had been made by men in the know. VADM (then CDR) Rosendahl and even CAPT Buckley (then a young midshipman, later co-author of the 1943 privately published book at left) had flown aboard LZ-129. However these discussions came years after the harsh economic times of 1939. In the real world, where the US Government had been unable to spend itself out of a depressed economy, it was a sure sign of the Administration’s contempt for Goodyear-Zeppelin when the bill HR 3519 of 1939 authorizing construction of a 300-ton Naval Airship never got off Capital Hill for a most certain Presidential veto. (Specifically, ZRCV would have been about 300 tons, vs. LZ-129’s about 242 tons.)

SIZE MATTERS

For the more airship-friendly “ZRS” universe, Burgess’ ZRCV is clearly too small a step. Author Rowan Partridge envisioned Long Island as 12 Mft3 , and we’ll show why we think this about right.

Ismal mastAs we have speculated on the Empire of the Air page, Scott and R.101’s delayed departure would have been pivotal in completion of the “Empire of the Air.” Direct flights to Canada, one-stop trips to India and few-stop trips to Auckland, Sydney or Singapore would in turn have created competition pressure for the German passenger service.

Later, with the German assembly shed extended and their LZ-131 “Super Zeppelin” under construction, 9 Mft3 was the new target. The Americans, at first hobbled by the BofM fraud cutting H2 flight funding, would have continued to believe their own propaganda, and stood behind the eight-ball of helium’s fixed, lesser lift for the dollar. As we see on the ZRS-4 Evolves page, the Americans had been forced to enlarge, to avoid performance embarrassment.  With R.101’s announced capacity of 5 Mft3 the Americans had revised to 6, then 6.5 Mft3, for the Akron/Macon design to keep pace. The Americans would have certainly repeated the airship enlargement process to stay “competitive” in performance.

These figures agree with a British study offering an explanation of their refusing the offer of American helium. P. L. Teed’s paper showed that, to perform like a 9 Mft3 hydrogen rigid, a helium ship would have to be 12 Mft3. Thus we arrive at the first parameter of our hypothetical American rigid airship within the given time/technology limitations – precisely at Rowan Partridge’s envisioned, twelve million cubic feet. That’s a good deal smaller than the Buckley/Barkley vision of 1943, but correctly beefing up the ZRCV reflective of the helium penalty in relation to the LZ-131.

The especially good news is, given the circa 50% increase in payload by conversion back to hydrogen from any design originally enlarged to be competitive with helium, Partridge’s Long Island would be comfortable with full fuel load and aircraft complement even in the vast reaches of the trackless South Pacific that had swallowed so many airplanes (Amelia Earhart being just one) in the past.

In the film production we will stick with Rowan’s overall vision for the basic size and overall design. We will pay special attention to the previous state of the art. We will take direction from those men who flew rigids, and had their own ideas as to the design details of the next generation.

FINENESS COUNTS

The fineness ratio – defined as the relationship of length to diameter – delivered reproducible drag values in rigid airships. Therefore it is possible to predict performance of anything from the football-shaped ZMC-2 (above left) to the torpedo-like stretched L-59 (LZ-104) “Africa ship” (above right). It comes as no surprise that all three of the last rigid airship designs—Akron/Macon, LZ-129/130, and ZRCV—were all within a tenth of a point of each other. We think it logical to split the difference, resulting in Long Island’s fineness ratio: six.

Blessed with the assistance of Mr. Norman Mayer, who had relieved C. P. Burgess at BuAer, the next step was easy. Plugging in the fineness ratio of 6 and the desired volume of 12 Mft3, the formula that Mr. Mayer created (for his AIAA paper and presentation at Bedford, England) yields our airship’s precise dimensions: Length, 944 feet; maximum diameter 160 feet.

From this point forward there are many options, each with their own followers and champions, and no preset formulas to plug in. Dr. Richard K. Smith in his The Airships AKRON and MACON: Flying Aircraft Carriers of the U.S. Navy discussed these options: “The British… in their R100 found their answer… using Barnes Wallis’ novel geodetic structure… and by using deep rings in their R-101. The Germans found their answer by using a supplementary axial keel… the Hindenburg and the Graf Zeppelin II, which ran through their hull’s centerline, of itself a radical departure from the so-called “conventional” Zeppelin… [USN BuAer’s] C.P. Burgess believed that an appreciable increase in performance could be realized through a radical break with the past, by discarding the archaic redundancies of the classic Zeppelin structure for the simplicity of Ralph Upson’s stressed-skin Metalclad design… [thus, with the tri-keel ZRS design of Karl Arnstein] …there were four different answers found to the same problem, and it is doubtful if the alternatives were exhausted.”

In this photo,  Arnstein looks over a special heavy-duty girder section with then-inspector LT “Tex” Settle, right. This larger, heavier type was seen in the hangar bay and other selected ZRS-4 & 5 assemblies.

Indeed, with airplane structures turning to metal, leaving only control surfaces fabric-covered, regardless of girder design, acres of nitrate-doped cloth would still be the weak point. R.101 design engineer V. C. Richmond said “… the fabric work of the rigid airship (i.e. the gas bags and the outer cover) represents the least satisfactory part…” Therefore, the wild card in any construction speculation is the stressed skin or “metalclad” airship which promised lessened manufacturing cost, and flame-safe operation with hydrogen. In the novel, Partridge speculates a balance was struck with the ship’s covering called “metalfoil.” For screenplay purposes, we will speculate the Germans figured out how to add bronze to the covering mix for conductivity, fireproofing and longevity, a few years before they actually did so. Perhaps during the 36-37 overhaul, or even earlier, but once done others had easily followed suit. Therefore, we will be forced to turn our backs on Ralph Upson and what C.P. Burgess called “the ultimate airship” – at least until (perhaps) the sequel.

THINK OUTSIDE THE BOX

Rosendahl wrote, “That German airship men did not like the AKRONMACON design is not exactly a secret, for privately and diplomatically they let us know it. Their main objection centered about our built-up form of main frame, and our use therein of square or ‘box’ girders rather than the previously accepted triangular girder.”

Before R-101 and Akron-Macon, girder design had changed little since before Zeppelin (Schwarz girder, left, 1898). Even pieces of the ZR-1 Shenandoah show a similar basic structural girder design. For the ZRS-4&5, Arnstein’s patented lightening holes were stamped into a sheet whose edges were formed to join with others like it. These were riveted together to form a box beams on bench jigs (photo).

These beams were used extensively in the structure of ZRS-4 & 5, including forming them into the arch-like constructions that formed rings.

By the later 1930s Arnstein had abandoned his complex box girder  in favor of what looks more like “previously accepted triangular girder” in Rosendahl’s Rigid History motion picture clip. The test section found in the Airdock supports this notion. Using ALCOA 24S the new girders could have been spot welded, easing the more complex jig-dependent process of drilling and riveting. Given that our basic building girder will be more “triangular,” without actually being able to employ the simple but strong tubular structures in use today, we can move on to the form used to employ the girders to make a structure.

ONE RING TO RULE THEM ALL

R.101 featured built-up rings whose continuous triangle was more injury-resistant and perhaps less wire-tensioned than earlier methods of building circular flyweight structures.  R.101’s rings (photo) supported the heavy pinpoint loads of diesel fuel tanks. There were no intermediate rings like those in the ZRS-4 & 5. In fact, it has been suggested the R.101 had no actual keel in the “conventional” sense. The R.101’s rings did not enclose the same triangular area as Akron/Macon’s  ladder-equipped main rings, but did allow some access impractical with conventional Zep design.

ZRS-4 & 5 used a similar, but heavier continuous pyramid-like ring design, which in the case of battle damage, was supposed to retain its circular shape. These eliminated the finely tensioned bicycle-like spoke-like wiring used to support the Zeppelin ring shape, let alone the complex and cell-complicating axial cable or corridor. Their interior ladders offered previously unknown access to the ship’s interior and its fittings.

As seen in the assembly films, the more fragile intermediate rings were attached to the mains for hoisting during assembly  in Goodyear-Zeppelin’s Airdock. Carefully spread out for more box beam girders to be added as longerons,  each bay took shape. (The ZRS–4 & -5’s ALCOA 17S structure was said to contain 6.5 million bucked rivets. )

For our USS Long Island, we will retain this built-up main ring  as a compromise between the R.101/ZRS4/5 and the later ZRCV more conventional ring design. We will reduce its height slightly to decrease the overall wasted non-gas space.

With ZRS-4, bay VII had been the first to be completed,  and was the first to be tested by installation of a gas cell and inflated with helium. In both ZRS ships, bulkhead wiring prevented a full cell from surging into an adjacent deflated-cell bay. These were fastened to the main rings with “resiliency devices” (marked with an “R” in the photo) which worked somewhat like automobile shock absorbers, and managed the tension of surging cells. The combination was designed to prevent adjacent cells from squeezing into nearby bays whose cells were deflated.  Various photos show cells purposely overpressurized to test the construction and design, thus resembling a sort of quilted blanket.

Our typical Long Island bay will be generally similar, likely with one smaller intermediate ring spacing owing to our larger number of bays and cells. There will be retaining bulkhead wiring to prevent surging.

It should be noted that, once designed and built, only to find performance expectations not met in the real world, it’s rather difficult to change airship capacity by enlarging the diameter. Therefore it was not uncommon to cut a rigid in two, so an extra cell could be inserted for more lift. (C P Hall has pointed out R-101’s extension spoiled her perfect aerodynamic symmetry and that structural section did not fare as well in her final impact. Yet, our movie will  have yet another bay added to our “R.101D”.)


So far, then, we have resolved to use ZRCV-like channel girder material in the construction of ZRS-4 &-5 like “main rings.” This offers compromises the designers of 1937-1938 would have considered the best choices, for crew access, least wasted non-gas enclosed area and damage resistance. For the movie, our USS Long Island set can use less complex tubular material to simulate spot-welded girder sections. A set including some lower-third main ring sections above will have to be built to support hangar bay and habitable sections where actors will perform their scenes. Intermediate rings would not normally be seen, obscured by fabric walls or simulated gas cells, which will easily be incorporated into the set.

Now we need only decide how all the rings will be joined together to form the framework, which will be addressed in the next post.

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On location with a TV crew at Pompano

One thing we’re planning for the site is a video compilation of Hollywood’s attempts at entertainment featuring LTA content. (Someday.)

A more ambitious project would be an examination of commercial television’s LTA related efforts, seemingly easy since most center around some way of blowing up the Hindenburg.  Until such time as we can whip that up, here is a 5 minute video by the producer taped during a documentary crew’s visit to Goodyear’s airship base at Pompano, Florida.

Last Navy Airship

The last airship purpose – designed for and delivered to the US Navy last century was the ZPG-3W, a 1.5 million cubic foot radar-picket ship.

The producer had visited the remains of the only remaining example of that model – in fact, the entire “Nan” series – at her resting place, D-M AFB’s “The Boneyard,” near the Pima Air Museum.

The NAA also scheduled a -3W car tour for a member’s reunion, and several men who flew on ZPG-3Ws (including BuNo -243)  visited their old aircraft.  The color photo shows Ross Wood, a ZPG-3W pilot and past NAA President. He is pointing out the name of Robert Keiser, the last skipper of Combat Air Crew  #102 to have is name stenciled on -243’s car forward. The B & W photo is of Bob Keiser himself using the retractable boarding ladder to ascend into the 3W’s forward section, back in the day.

The producer has prepared a 6-min. video tour of this, the largest blimp ever made.  You’ll also see Bob and his family aboard in the second deck mess, as we pop back and forth to her active duty days.  (Watch for that boarding ladder lying in the car’s interior today.)  Bob passed away in 2017. Unless steps are taken to stabilize its remains, this last Navy airship will eventually cease to exist.

you can read a ZPG-3W pilot’s memoir in:  The Airship Experience

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