HOVERCRAFT!!!

Who invented the hovercraft? What happened to all the hovercraft that used to provide transportation options in the UK? How do they work? We look into all this, plus a classic Jackie Chan action flick.

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Episode Transcript

Speaker 1 (00:04):
Welcome to tech Stuff, a production from iHeartRadio. Hey there,
and welcome to tech Stuff. I'm your host, Jonathan Strickland.
I'm an executive producer with iHeart Podcasts and how the
tech are you? So y'all already know what this episode
is about, because it's right there in the title for

(00:25):
the episode. The title itself is a reference to a
nineteen ninety five Jackie Chan film called Rumble in the Bronx.
So in the climax of that film spoiler alert, there's
a scene in which a hovercraft goes absolutely ape through
the city. It crashes into cars, it absolutely destroys Lamborghini,

(00:48):
and it interrupts a rock band that's playing outside on
the street. And it's at this point in the film
where the drummer of the rock band stops playing mid song,
stands up, points and yells hover aft, which is my
favorite part of the whole movie, even with all the
amazing fight sequences taken into account. And this is the

(01:09):
sort of stuff that inspires tech Stuff episodes, because that's
how my brain works now anyway, Yeah, Jackie Chan films
from the nineties really a source of inspiration. So I
thought it would be fun to do an episode tracing
the history of hovercraft and to talk a little bit
about how they actually work. And I also think this
is the type of topic where you have one concept

(01:30):
in your head when you first hear about it, Like
when you first hear the word hovercraft, you might have
a vision in your head of what that might be,
and then ultimately you could be disappointed when you see
it in the real world. That was my reaction anyway,
because as a kid, when I heard the word hovercraft,
I thought of some sort of semi magical vehicle that

(01:50):
could levitate above the ground, probably something closer to what
drones are, but without the rotors, right, Like there's some
unseen force that makes the thing floatt. So I was
kind of thinking of something similar to like the hover
boards that are featured in the documentary Back to the
Future too, But of course that's not how your typical

(02:12):
hovercraft works. Hovercraft, by the way, are also called air
cushion vehicles, and that air cushion gives a huge indication
of how these things work. And arguably my whole perception
or misperception of hovercraft isn't really fair. I mean, it's
not the hovercraft's fault that I had an overactive imagination

(02:33):
and unrealistic expectations. It is a fascinating invention, and it
traces its history really back to the nineteenth century, when
you had people sort of theorizing about it, but effectively
for talking about making something that actually works. It's more
like the middle of the last century. And I was
born in the last century, and saying that way hurts

(02:56):
a little bit. But the inventor of the hovercraft, the
person that we credit as the inventor, so so I
guess you could say sort of inventor of the hovercraft
was a gentleman by the name of Christopher Sidney Cockrell.
Now I say sort of because, as we will find
out later in this episode, there was another person who
came up with the same concept a decade earlier, but

(03:20):
due to a technicality, this person had no ownership of
this idea. But we'll get back to why that happened.
So Cockrell's parents were both distinguished members of English society.
His mother was Florence Kingsford cockerl. She was known for
her artistic talents in calligraphy, illumination, illustration, and costuming. When

(03:42):
I say illumination, I mean manuscript illumination, think of the
stuff that monks used to do back in the Middle Ages.
So way back in my college days, I focused my
studies in medieval literature and medieval history, and after looking
at Florence's work, I'm really amazed at how her evokes
those ancient texts. Cockrell's father was Sir Sidney Cockrell, who

(04:06):
came from a coal mining family. Like it astonishes me.
He came from a family that worked coal mines, but
he found himself thrust into the social circles of influential
people who were in the artistic and literature worlds in England.
So Old sid served as a personal secretary to British

(04:27):
author and artist William Morris, and Sydney eventually became the
director of the Fitzwilliam Museum in Cambridge, England, where he
had a bit of a reputation for having an incredibly
effective method to convince hoity toity rich people to hand
over some of their filthy lucre to support the museum.

(04:47):
So Christopher Cockrell came from, if not blue blood, at
least light blue blood Lemmelson Mit, which bills itself as
the quote national leader in advancing in vention education in
The quote says that Sidney Cockroll wasn't entirely sold on
the idea of his son going into engineering, but that's

(05:09):
exactly what young Christopher Cockroll wanted to do. And I
find this notion rather like a money python sketch, because
you have a man who comes from a coal mining family.
He's defied the odds, he's become a director of a
prestigious museum, and now he is concerned that his son
wants to be an engineer. In fact, there is a
money python sketch in which you have a family of

(05:32):
It sounds like lower class English folk who are authors,
who are a shame that their son wants to go
into being a coal miner, flipping the old narrative on
its head. So this is reminding me of that fictional sketch,
you know, very silly stuff. But yeah, he didn't want
Christopher to become an engineer. But whether he had reservations

(05:57):
or not, ultimately Sydney agreed to support his son's pursuit
of an education in engineering. In fact, according to the Guardian,
Sydney offered Christopher the princely sum of ten pounds for
every patent his boy would receive. This was back when
old Chris was still a teenager. Sidney would call an
end to that deal later on because it would get

(06:17):
pretty deep, deep, pretty expensive. Christopher attended Petterhouse College at
Cambridge University. In his obituary Cockrell passed away in nineteen
ninety nine, by the way, in his obituary in The Guardian,
Christopher Cockrell was said to have spent much of his
spare time in college quote taking motorcycles to pieces or

(06:39):
racing them end quote, and that this gave him the
experience of practical background in basic mechanics and engineering, which
is kind of cool, like the idea of learning by
doing something you're already interested in. So that was already
neat of course. Christopher by this point, by the time
he was going to university, had already expressed a deep
interest in engineering. Upon graduation, Christopher Cockerrell took a position

(07:04):
with the Radio Research Company. This was in nineteen thirty five,
so still relatively early in the days of radio. I
mean radio had been around for a while, but still
a fairly young science. And he joined the Marconi Wireless
Telegraph Company and worked in an R and D department
that largely focused on radar and he made numerous contributions

(07:26):
to radio and radar technology. Many of those contributions were
put to use by Allied forces during World War Two. Now,
Christopher Cockrell made a career change in nineteen fifty, so
the war hit was over. He continued to work in
radio for a few years, but in nineteen fifty his
father in law had left his wife a big sum

(07:47):
of money, and together Christopher and his wife decided that
they wanted to purchase a boat business in Norfolk, England,
and Cockroll devoted his attention to managing this boat business.
And it was to shift when I was reading up
on his life that this actually gave me a little
bit of whiplash, because here's someone who was instrumental in
advancing technology and radio and radar, and now he's switching

(08:10):
over to manage a boat business. But it was as
a manager of this boat company that led him to
start thinking about a solution to a really tricky problem
and ultimately would lead him to inventing the hovercraft. So
Cockrell got to thinking that there must be a way
for heavy watercraft to travel much faster across bodies of water,

(08:37):
and it would be possible if only you could get
the boat out of the water. If you could remove
it from contact with the water itself, if the craft
could somehow float above the surface of the water, then
that would eliminate all the friction that it otherwise would
encounter as it moves through the water, and it would

(08:58):
be able to move much more quickly than it could otherwise.
But you just had to figure out a way to
minimize or eliminate contact with the water. And if you
could get it to lift up above the surface of
the water entirely, technically you actually would have an aircraft,
not water craft. But that was his starting point. He thought,

(09:20):
how can I create a vessel that would minimize or
eliminate contact with the water so that it can move
much more quickly and efficiently. So Cockrell imagined a craft
with a cushion of air underneath it. That cushion of
air would provide a barrier between the vessel itself and
the water or land underneath. If you could blow out

(09:42):
enough air, it could skim right across the surface, whether
it's water, land, or some mixture like mud or swamp
or whatever, and it could potentially cut travel times significantly,
at least as far as water goes maybe not with land,
because as it turns out, if you're going across solid
land and you've got yourself a road and you have

(10:03):
a wheeled vehicle, you can zip along that pretty darn fast,
and it would probably be difficult and very dangerous to
operate a hovercraft at those speeds, because you've got to remember,
hovercraft typically for propulsion's sake, is using wind power as well. Right,
you've got a fan that points backward and you're blowing
out airs and you know, obviously equal opposite reaction time.

(10:24):
That means you're moving forward as a result with a
proportional force, but that doesn't mean that you can easily
do things like stop, and that turning is more of
a gradual process as well. So moving at high speeds
across land where you could occasionally encounter obstacles probably not

(10:45):
the best idea. But anyway, in Cockrell's spare time, he
started to tinker to see if this idea he had
could be made practical. He wondered, first is it plausible
and then is it practical? So early on, as a
store where he goes, he used some tubes from an
old vacuum cleaner as well as the vacuum cleaner's motor,

(11:05):
and he used a pair of empty cans. The types
of cans, it depends on which version you read. Like
some say it was a couple of coffee cans. One
was slightly smaller than the other. One was like, no,
it's a coffee can, and then a cat food can.
Some call them tin cans, some call them aluminum cans.
I think what's important to know is he used a
pair of cans. One was larger than the other one.

(11:26):
He put the smaller one inside the larger one. He
blew air so that it would go underneath the smaller one,
which was turned face down I imagine, like open side down,
and the air would create an air cushion, and the
smaller one would end up hovering inside the larger one

(11:47):
and just kind of bang around a little bit. So
he saw that this was possible. It could create lyft,
and that lift could be enough to counteract the weight
of the vessel, in this case the little small can.
So his concept had validity, and Cockrell got to work
building on a prototype, an actual sort of small hovercraft

(12:08):
that would be more substantial than just a pair of
aluminum cans and some tubes. And it took him a
while to build it, but by nineteen fifty five he
had a working prototype, and he then had to decide
what was he going to do with it. And he
could have tried to create like a private business based
off this, but the story goes that instead he thought,

(12:30):
I'll show local officials, I'll see if I can get
some investment in this and turn it into something viable.
In that way, I'm not just sinking money into something
that may never pan out. So he arranges a demonstration
for his hovercraft prototype with some local officials, and the
story goes that the local officials were astonished and more

(12:52):
than a little frightened as Cockrell's prototype skimmed around inside
an office that he had brought it into this office
of the the local officials. He had fired up the
engine that would drive the fan. So you got to remember,
this is an internal combustion engine. It is burning fuel
and letting out fumes, and it's very loud, and it's

(13:12):
turning this fan, and the fan is making this hovercraft
skim above the surface of the ground. And then there's
not really a way of steering the hovercraft at this point.
It's just showing a proof of concept. It's kind of
bumping around like a bumper car all over the office.
People are jumping up on chairs and desks and trying
to get out of the way. And meanwhile, like I said,
it's noisy and it's smelly. It made a real impression

(13:36):
and it makes me think of that scene in Rumble
in the Bronx where there's just a hovercraft gone wild.
So the officials weren't quite ready to devote funding to
Cockrell's invention at this point. There was this general perception
in the nineteen fifties that England was not really that
interested in investing in innovation. There was this perception that

(13:57):
England was kind of backward at this point. They were
focused more on things like, well, we're doing it this
way because that's how we've always done it. Whether that
was an accurate representation of what was going on in England,
I can't say, but that was the perception. So consequently,
the nation was starting to feel like it was falling
behind some of the rest of the world. More than that,

(14:20):
the officials who saw this demonstration decided, rather than fund
Cockrell's idea, they would put it on a so called
secret list, which effectively meant they were classifying his invention.
They were putting it under classified information, and Cockrell would
be legally prohibited from talking about it or finding some

(14:42):
other means to fund his work that that would be
against the law. Maybe he could find a way to
fund it if he could somehow convince people to give
him money without actually talking about the invention itself. But
really it just meant that the officials were really hamstringing him.
Now we're going to take a quick break, and when
we come back, we'll talk about what happened next and

(15:03):
how Cockroll was able to get some progress despite this
initial setback. But first let's take a break to hear
from our sponsors. Okay, we're back. So before the break,
I talked about how Cockrell does this demonstration. Officials are

(15:27):
taken aback and they decide to classify Cockroll's invention, which
effectively makes it impossible for him to do any real
work on it. This is despite the fact that Cockrell
had demonstrated to them that his hovercraft could potentially solve
a lot of problems like not only could it glide
over water, it could go over land, it could go

(15:50):
over lots of icky stuff that other vehicles actually have
a lot of trouble with so marshes and muddy sections
and stuff. You know, if you had a boat, you
wouldn't be able to go through these because there's not
enough water to keep the boat floating right. The boat
would just get beached or mired. Same with vehicles that
are on treads or wheels, they would eventually get stuck

(16:14):
in really nasty muddy situations. But the hovercraft would float
above all this. It could get you through to places
that other vehicles couldn't unless you were using something like
say a helicopter or an airplane. So Cockrel was really
making a case for how this could be a really
useful vehicle for all sorts of different applications, and none

(16:37):
of that seemed to really matter to these officials. However,
he did receive a patent for his invention in nineteen
fifty six because he had filed for this patent before
the officials had put the hovercraft on the secret list,
so ironically, his invention was already public because patents are public, right,
that's one of the elements of patents. When you file

(16:59):
for a patent, your description of your invention is made public,
but in return, you receive government protection for your idea,
at least for a certain amount of time. So this
is why we call him the inventor of the hovercraft,
because Cockrell actually secured patents relating to his invention, although
as I mentioned earlier in this episode, and we'll get

(17:21):
back to it, there was someone else who had built
something similar a decade before Cockroll did. In nineteen fifty eight,
the UK government declassified his work and this gave Cockroll
the chance to actually pursue funding. The UK's National Research
and Development Agency or NRDA, was really impressed with his

(17:42):
invention and they commissioned a company called Saunder's Row to
build a test hovercraft based on Cockrell's design. So Sunder's
Row was already an established business. It specialized in building boats,
and they produced a vehicle that was called the SR
in one. SR standing for Saunder's Row, and it was
really only big enough to hold its own crew. It

(18:05):
wasn't designed for passengers. But here's the thing. It did work,
and on July twenty fifth, nineteen fifty nine, Saunder's Road
demonstrated its capabilities by having the SR in one cross
the English Channel. The hovercraft left Dover in England and
landed in Calais in France. Ou La Lain. Cockrell himself

(18:26):
was aboard of the hovercraft for this demonstration. According to
The Guardian, he served as ballast very dignified. This demonstration
convinced UK authorities to invest more heavily into the hovercraft technology,
and the NRDA created a company called Hovercraft Development Limited
with the purpose of creating hovercraft for commercial purposes such

(18:48):
as ferrying cargo and passengers across various rivers and channels
like the English Channel. The organization oversaw the work of
five different companies that were all dedicated to this purpose,
so there was five different boating companies that all began
building hovercraft vehicles. Christopher Cockrell landed a gig as the

(19:08):
director for Hovercraft Development Limited, and he was also the
technical advisor to the company and he stayed on in
that capacity until nineteen sixty six. Also in recognition of
his contributions, he would ultimately receive a knighthood in nineteen
sixty nine, just like his dear old dad. So you
had Sir Sidney and now you had Sir Christopher. The
first of the passenger hovercraft was the Vickers VA three,

(19:32):
which was an experimental vehicle it wasn't meant to be
built for full commercial use. It was more like, again
a proof of concept. It launched in nineteen sixty two.
British United Airways ran the service because again hovercraft were
thought of as an aircraft not a boat, right, because
these fans would end up creating this air cushion that

(19:54):
made the vehicle hover, sometimes several feet above the surface
that it traveled across. So as such it was more
of an aircraft than a watercraft. So the initial route
passed over an estuary between Liverpool and North Wales. The
hovercraft would hold up to twenty four passengers per trip,

(20:15):
and it was intended to take twelve trips per day.
And like I said, this was kind of an experiment.
It was a pilot program. And originally the concept was
that it would go for fifty nine days and then
they would evaluate does this make sense, like can we
turn this into a reasonable and viable transportation option. But

(20:36):
while it was meant to go for fifty nine days,
it only made it to thirty six. The reason for
that was not entirely the fault of the actual vehicle,
although there were some engine problems that turned out to
be a bit of an issue, and in fact that
would become a thing for a lot of hovercraft. It's
not that the design was bad, it's that sometimes the

(20:58):
equipment that was being used wasn't the most reliable. The
other issue was that there was a lot of bad
weather during that stretch. Now I think that you should
just anticipate that, because as far as I'm concerned, bad
weather is kind of a constitutional requirement in the UK,
at least every time I've been there. So anyway, because
of this combination of issues, the experiment was cut short.

(21:22):
The VA three would retire as a passenger vehicle, but
the British government would continue to use the VA three
vessel to conduct some other kinds of tests, including a
very extreme one. Namely, the test they wanted to really
check out was could a hovercraft pass safely over a
zone in the sea that happened to be occupied by

(21:45):
marine mines? Right? Like? These are those mines you see?
You know, typically I almost only see them in things
like cartoons, where it's the giant globe with lots of
little pressure sensors on it that are connected by chains
and anchor to the seafloor. And the ideas that a
boat which will pierce the surface of the water. If

(22:07):
it were to make contact with these would cause it
to explode. Well, the thought was, well, hovercraft, they don't
pierce the surface of the water, they hover above it.
So is it possible that a hovercraft could safely glide
over an area that is filled with marine mines and
not trip them? And they tested it and the VA

(22:28):
three done blowed up real good, which answered that question
rather definitively. Passenger hovercraft would tackle the English Channels starting
in nineteen sixty six, with one of the most famous
being a class of hovercraft called the SRN four. Again
back to the Saunders Row and this was also known

(22:49):
as the mount Batten class of hovercraft, and the very
first one that made the trip across the English Channel
was called Princess Margaret. This was in nineteen sixty eight.
These vessels could make the trip between England and France
in about half an hour. Typically we're talking like Dover
to Calais, but sometimes a different port in France. But

(23:09):
the interesting thing is if you contrast this with the
traditional ferries that were making this trip between England and France,
that journey would typically take an hour and a half.
So three times as long. So the fairies had some advantages, right,
You could build a ferry large enough to carry much
more cargo and many more passengers than your typical hovercraft could.

(23:33):
You know, hovercraft was usually carrying around two dozen people,
maybe a little bit more, and maybe like as many
as twenty cars initially. With these larger hovercraft and fairies
could carry much more than that. However, hovercraft could make
three trips in the same amount of time that the
ferry took to do one, so there was a way

(23:53):
of you know, kind of figuring that out and balancing
it between the two. For a while, hovercraft would factor
into Britain's transportation infrastructure. In fact, some would call hovercraft
a quintessentially British form of transportation because there were lots
of places around Britain where you could grab a hovercraft
to go from one port city to another, whether it

(24:16):
was to cross a river or an estuary or a
channel or whatever it might be. But as I mentioned earlier,
there's some slight dispute as to whether we should even
call Cockrell the father of hovercraft in the first place,
and that maybe thinking of hovercraft as a really British
type of technology is misleading because, as it turns out,

(24:38):
a Yank came up with a very similar methodology a
decade earlier. And again, the actual theory for hovercraft predated
both of these guys by decades, like almost a century,
so let's keep that in mind. But the Yank was
a guy named Charles Joseph Fletcher who was born in

(24:58):
nineteen twenty two in New jer the United States. So
Cockrell was born in nineteen ten. Fletcher was born in
nineteen twenty two, so he's twelve years younger than Cockrell.
During World War Two he served as an officer in
the US Navy, and while doing so, sometime around that
same time period. The details, to me are are a

(25:18):
little bit hazy because a lot of the sources just
don't have things like specific dates, But sometime around then,
he sketched out a design for a vessel that would
use a cushion of air to glide. You know, you
could almost say hover above the surface below, whether that
was land or sea, which sounds pretty familiar right now.

(25:39):
He called his invention a glide mobile, so he had
hovercraft and glidemobiles. So the story goes that Fletcher actually
built a prototype of his design and tested it in
New Jersey and showed it off to the Navy, and
the War Department said, say that can be useful and
then swooped in to take charge. So the War Department

(26:01):
classified the project, similar to what happened to Cockrell when
he showed it off to those local officials over in
the UK. By making it a classified project, it prevented
Fletcher from being able to seek a patent for it.
He did not file a patent before showing it off,
so the Glidemobile didn't really go much further as a result,
because it just became the property of the War Department,

(26:22):
and the War Department apparently didn't do very much with it. However,
eventually some British companies were making a patent claim against
the glidemobile design. This is after World War Two, it's
in the nineteen fifties, and the hovercraft companies are saying, hey,
you are infringing upon a patented technology. And then Fletcher
was able to defend the position of the glidemobile by

(26:45):
pointing out that no his designs predated Cockrell's patent and
that it served as sort of prior art and meant
that they weren't infringing upon a patent because they were
building upon a design that actually pre dated the patent.
Presumably Fletcher was able to prove this concept predated Cockrell's

(27:05):
patent and he was able to move forward. I don't
know for sure, because again the details are pretty scarce.
But anyway, you didn't see hovercraft become a favored form
of transportation here in the United States, whereas again in
the UK, particularly in like the sixties and seventies, it
really was like it became a kind of common form

(27:28):
of transportation for folks who were trying to get across
bodies of water quickly. Now, even though they were really
famous in those days, there's only one commercial hovercraft service
that is still in business today in the world, and
it happens to be in the UK. It's a route
that goes between the city of Ride, which is on

(27:48):
the Isle of Wight, and south Sea in Portsmouth. So
you might wonder what the heck happened? Why did this
form of transportation, which was fairly enthusiastically embraced in the sixties,
why did it peter out by the time you get

(28:08):
to modern day, to the point where now there's only
one commercial route still in business. Well, I'll tell you,
but before I do, we're gonna take another quick break
to thank our sponsors. Before the break, I mentioned that,

(28:34):
you know, for a while, hovercraft were enjoying a moment
in the spotlight, but then a few decades later they
have all but disappeared, at least as far as commercial
travel goes. I don't want to say that there are
no hovercraft anymore. There certainly are, and in fact, there
are a lot of hovercraft that are meant for very
specific purposes. It's just you don't see them as cargo

(28:56):
and passenger travel solutions these days, not that much anyway.
And there are a few reasons for this. And it
is kind of crazy because even if you go back
to like the nineteen seventies, there's a James Bond movie
in which there's a big hovercraft sequence. And again there's
the bit in the ninety five movie Rumble in the
Bronx where there's a big hovercraft sequence. But there are

(29:16):
reasons why it's no longer a reliable and widespread travel solution.
One is that hovercraft, especially older hovercraft, are really really noisy.
I mean they make a huge amount of noise. They
use these massive engines to turn the fans. The mount

(29:40):
Batten class that I mentioned earlier used these enormous turbo
gas engines that were made by Rolls Royce, and these
engines make a whole lot of noise. They also generate
a lot of exhaust, but they're very, very loud. The
fans also generate a good deal of noise as well.
So if you were a company and you're proposing building

(30:03):
out a hovercraft to run a route between two particular cities,
chances are you're going to have residents of those cities say,
come on, we don't want that. We do not want
to have this kind of noise pollution in our communities.
Most folks aren't keen to have their days punctuated with
extremely loud traffic from all sorts of places. And as

(30:27):
someone who lives right across from a freight train line,
I can understand this is not thrilling to hear that
freight train go by. So that made expansion a little tricky, right.
It's a lot of not in my backyardism, but understandable
because that noise pollution is serious stuff. But another issue
is that while hovercraft can have a big advantage in

(30:47):
that you don't have to use a peer or anything
like that. Like, you don't need a peer or a
dock in order to secure the craft. You can just
drive the hovercraft from the water up to the land
as long as the land is relatively clear. You still
need a space where the hovercraft can go, right, you

(31:07):
can't just plow through like woods or whatever. You can't
go wreaking havoc through a marina. You need to have
a dedicated space where the hovercraft can beach itself, like
can go up onto the land and then descend so
that people can get off the vehicle. So you do

(31:28):
need to have some physical space available for the hovercraft,
and not every place had that as an option. Then
there's the issue of maintenance and repair. Hovercraft need these
really big engines to work. Like if you're looking in
the grand scheme of things the fans used in hovercraft,
they don't need to generate the same amount of lift

(31:48):
that a helicopter would, right, they don't have to work
as hard as the rotors of a helicopter, but they
still have to work. And these really really big hovercraft,
while they can be very efficient, still need a great
deal of power in order to generate that lift. So
you need these really large engines. If those engines are

(32:09):
in disrepair, then you're not going to go anywhere. And
as I've already said, like some of the engines that
were used in hovercraft, especially in the early days, weren't
terribly reliable, and that meant that hovercraft could be down
just as frequently as they could be in operation, and
this gets expensive to do maintenance and repair all the time.
There's also the matter of fuel. Those engines require a

(32:30):
lot of fuel in order to operate, and fuel is expensive.
And remember, in the nineteen seventies, the world went through
an oil crisis and fuel prices skyrocketed in the nineteen seventies.
This was due to a political crisis in the Middle
East that spawned from some military conflicts in the Middle East.

(32:54):
So this was not a natural oil crisis, it was
a man made one. But it's still meant that fuel
prices around the world, especially in the UK and the
United States and in Japan, went crazy high, and so
operating a transportation system that was fuel hungry was kind

(33:15):
of a losing proposition as far as money goes. So
eventually it just got to a point where the return
on investment wasn't really that good. It became too expensive
to operate a hovercraft service. Most hovercraft are fairly modest
in size. They might carry a couple of dozen passengers
at a time, maybe a few cars. The Mount Batten

(33:35):
class was different by the time we get to its
later refittings because of the Saunders Row would end up
upgrading this class of hovercraft over and over again. By
the end of it, they could carry more than four
hundred passengers and around sixty cars at a time, which

(33:56):
is pretty impressive, but I imagined that the profit margins were
still fairly thin when you look at how expensive it
was to keep the vehicles in operation versus how much
you can make in ticket sales to customers. Because eventually
you're going to get to a point where a customer
is going to say, I'm not willing to spend that
much money just to save an hour's worth of time

(34:17):
while I'm crossing the English Channel, for example, Like I'll
spend less money and it'll take me an hour and
a half to get there, rather than spend five times
as much in order to get there in half an hour.
So it just meant that there really became fewer and
fewer financial reasons to keep a hovercraft operation going. So
by the year two thousand, most hovercraft services commercial ones

(34:41):
had shut down, and as I said, the only one
that remains now goes between the Isle of Wight and Portsmouth.
Occasionally you will see hovercraft of various sizes doing other
types of jobs. There are some military hovercraft, there are
some other ones that are used for you know, recreation purposes,
but when it comes to commercial transportation, it's really mostly

(35:04):
a thing of the past. Now that we've covered the
history of the craft, let's talk about what's actually making
them hover because it's just a tiny bit more complicated
than fan points down and air pushes hovercraft up, but
only a tiny bit more complicated than that. Ultimately, that
is what is making the hovercraft work. So you could

(35:25):
just walk away with fan points down. It pushes air down,
hovercraft goes up because equal and opposite reaction and whatnot.
So the original hovercraft design used two layers of a
shell or hull. Think of it like a channel, like
it was a channel through which air could flow, and

(35:47):
the underneath the hovercraft is a hollow section that would
be called a plenum. In fact, the original version of
a hovercraft that little ten can version. You could think
of that as a plenum based hovercraft, where you're just
pumping air through the plenum. That's enough to generate lift,
but only generates a little left. You aren't able to
get very much height using that. So this other version,

(36:13):
the one that Cockroll had designed, used this channel of
air that would direct air to flow down along the
periphery of the hovercraft's bottom, So you have a vertically
oriented fan it's blowing air downward. That air flows through
this channel, which then is directed toward the outer section

(36:35):
of the hovercraft. It creates a ring of air. That
air is effectively flowing inward toward the inside of the hovercraft,
that plenum, that hollows section underneath the hovercraft, and that
ring of air also serves as a kind of curtain
or barrier, so it's not allowing air to escape out

(36:56):
the sides of the hovercraft, or at least not a
lot there escaping out the sides of the hovercraft. And
this creates the lift. It allows the hovercraft to levitate up,
not levitate, but to hover up, and you can get
a hover of around several inches up to a couple
of feet, but you couldn't get much higher than that. However,

(37:16):
later on, engineers developed a flexible skirt for hovercraft. So
imagine that you have this flexible material, typically made out
of rubber, that goes around the periphery of the hovercraft.
So it's got a little skirt that goes all the
way around. When you're directing air downward, perhaps in the

(37:38):
same style as you were before, which was actually called
a peripheral jet approach, maybe you're using a combination of
the skirt and a peripheral jet. Then it keeps the
air in more effectively than just the peripheral jet by itself.
The rubber contains the air there. It creates this air cushion,

(37:59):
and theft actually get much more height this way. You
can get maybe up to like six or seven feet
of height using this. So the skirt makes it look
like the hovercraft is still keeping contact with the ground,
but the actual bottom of the hovercraft itself is several
feet above that, and this is how hovercraft typically work.

(38:21):
A secondary fan is usually used to provide propulsion. I
mentioned this earlier. You got a fan that points like
backward from the hovercraft, and when you turn that on,
it's shooting air. Out the back, and then you get
the equal but opposite reaction. The hovercraft will move forward.
You usually have a rudder or some other method to

(38:41):
redirect that fan so that you can make turns. Those
turns can be pretty gradual, and you still have momentum.
You know, you have the loft conservation of motion. You're
still moving. So that's why it's difficult to pilot these things.
It's challenging. You can't just slam on brakes with a hovercraftft.
You can stop the fan and you will come to

(39:03):
a stop gradually, but you can't just slam the brakes,
so tight turns and sharp stops are not really possible,
which is why hovercraft are typically a little easier to
operate on the water than they are on the land.
If you come up to an obstacle on land, you
might be bumping into something. One thing that Cockrell figured
out was that, perhaps counterintuitively, the larger the hovercraft was,

(39:27):
or more precisely, the larger the area of the air
cushion or cushions that provide the lift, the more efficient
the hovercraft became. Here's how he put it in his patent,
and it does get technical. So here we go quote.
In such vehicles, the lift or load carrying capacity is
proportional to the plan area of the gas cushion or cushions.

(39:49):
The energy required to contain the cushion or cushions is
proportional to the peripheral dimension of the cushion or cushions. Thus,
for an increase in size of a vehicle, the lift
increases proportionally to the area of the cushion or cushions,
whilst the energy requirements increase linearly with the periphery of

(40:11):
the cushion or cushions. So, in other words, the larger
the hovercraft is, or the larger the surface area of
the air cushion is, the easier it is to achieve
greater lift with only a smaller increase in actual power.
So you're getting greater returns for just a smaller investment
in power, and thus it's more efficient to build larger

(40:34):
hovercraft than it is to build smaller hovercraft. I guess
you could still just say that pointing a fan downward
provides the lift needed to hover the vehicle, and you
could just leave it at that, but you do need
some other design elements to make the vehicle stable and useful,
Like I said, hovercraft are still a thing, They're just

(40:54):
not typically used for commercial transportation. They are not commonplace,
but similar technologlogies related to hovercraft have found their way
into designs since then. You might know that the original
concept for the hyperloop train system included a train running
through a tube where you had pumped out most of
the air, and the train would hover above the floor

(41:17):
of that tube through the use of air ball bearings.
So Elon Musk described it as sort of like an
air hockey table, only facing downward instead of facing upward.
That's not that different from a hovercraft, or a glidemobile,
or an air cushioned vehicle, however you want to call it.
The methodology described in the hyperloop concept is a bit
different from what you'd see in a hovercraft, but the

(41:39):
gist is similar. As it would turn out, the various
companies that sprung up in the wake of Musk's proposal would,
by turns, choose a different approach. Some went with magnetic levitation,
some would dispense with the idea of suspending the train
above the track entirely and thus embrace a more traditional
train design. But initially the hyperloop was meant to have

(42:01):
an air cushion under it. Of course, you could argue
that these days the hyperloop concept has been all but
abandoned because several of the companies that pursued the goal
of making it a reality have since gone out of business.
You can, of course, build your own hovercraft. There are
websites describing how to make a sample hovercraft using like

(42:21):
a balloon and an old CD or a DVD. I
would suggest use one you don't plan on ever playing again.
Maybe maybe a kid rock album would be suitable. There
are also kits to build an actual hovercraft. You know,
you can kind of build a sort of personal pan
pizza sized vehicle. I've seen diy hovercraft on YouTube of

(42:44):
varying degrees of safety and reliability, and there are lots
of ones for things like radio controlled hovercraft. Right. There
are a lot of toy versions of hovercraft that work
on the same principle, but they're obviously at a much
smaller scale, and that way you can learn how challenging
it is to direct a vehicle that works on momentum
and has a lack of breaks. It can really be

(43:06):
easy to get moving in a particular direction and a
real challenge to you know, stop doing that. But that's
our look at hovercraft, a technology that I think is
pretty interesting, pretty cool. I have never written on one.
I've never been on a hovercraft. I kind of wish
that I had had that experience. Maybe one day I'll
make a trip out to the Isle of Wight simply

(43:27):
so that I could say I wrote on a hovercraft,
which means that I'll be walking around Isle of Wight
and probably lamenting how many places have closed down. I've
watched some videos recently of that area of Isle of
Wight and it was looking a little grim, although I
should say that was also in the off season, so
maybe that's it, you know, Maybe it's just that, Oh,

(43:50):
these are things that are usually working in the more
popular seasons. It's just in the off season they shut
down because there's no sense in running it. Then maybe
that's the case, I hope. So, but that is our
look at hovercraft. I hope you enjoyed this episode. You
learned a bit about Sir Christopher Cockrell and his mission
to create a new form of transportation and to get

(44:13):
past that irritating problem of friction that voting stuff encounters.
Although Cockroll encountered more than a little friction just you know,
in the political side, as opposed to as opposed to
physical friction that you would encounter in the water. I
hope you are all well. Thank you so much for listening,

(44:36):
and I will talk to you again really soon. Tech
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