English Presentations  by Hans Walrecht

My presentations contain many pictures and videos. Pictures can tell a story themselves and videos do the same, but better.
In my opinion it is very important to put a subject in a context (why then, why did they do it that way, what was the use of it?).

I like to reach a big audience, so I make use of popular science and show the human side of the story, if possible. Some presentations do have more layers, to satisfy the people who want to know a little more. The same way modern educations works.

I am a retired teacher in primary education and education for children with special needs. For the latter half of my career I was involved in IT -especially the educational part. IT brought me into European projects, in which IT was leading. In a few projects I was the coordinator.
Working in Primary Education leads to many subjects, broadening my interest, as you can see in the subjects below.
Technology and history I always liked most. That is why I’m a volunteer at the Steam Engine Museum in the Dutch town of Medemblik and the Aircraft museum “Aviodrome” in Lelystad.

Moreover I have been writing for papers and magazines the last 50 years. I live in Alkmaar, the Netherlands, just 25 miles North of Amsterdam.


These are the subjects:

01 The Invisible War 10 Aero Engines
02 The development of the jet engine during WW2 11 Moments of the Industrial Revolution
03 Wernher von Braun and the V2 12 ULTRA and Enigma
04 Pictures from Space 13 Red Ball Express
05 Dakota, the Allied Workhorse Target for Tonight (by Theresia Kloosterboer)*
06 The Spitfire 14 Kids presentation "How does it work: The aeroplane"
07 The Great War at the Western Front 15 James Watt and the Steam Engine
08 The 14-18 Air War 16 The Steam Pumping Station of Medemblik
09 The de Havilland DH.98 Mosquito

*) my partner

The Invisible War

(The navigation beams and radar in WW2)


This presentation is about the use of radio and has everything to do with WW2 era bombers and fighters.

I've made two versions:

The first for radio amateurs, in which some subjects are extended, like the British “Chain Home” radar and the “Magnetron”. And there is a link between the Dutch Philips company (via Mullard) with British radar.

The second for a public without knowledge about radio. Unfortunately I can’t tell the story without informing the audience about the relationship between frequency and wavelength. But that's all.

For the two types of public the story is more or less this:

The beams of radio waves that guided the German bombers to British targets, like their Knickebein system, X and Y systems and what the British could do against it.

Further, the British Chain Home radar, the German radar with Freya and Würzburg. The British “Raid on Bruneval”, intended to capture parts of a German Würzburg radar station, is a thrilling story

After the “Blitz” the British start bombarding Germany, with poor results. Most of the bombs missed their target. This should be improved, but how to navigate over a dark hostile territory? The British answers were “Gee”, “Oboe” and the H2S radar, used in bombers and pathfinder aircraft.

This starts the first electronic warfare in history. Every measure evoked a countermeasure.

duration: 1½ hours

The development of the jet

engine during WW2


Speed is paramount for military aircraft. British Royal Air Force pilot Frank Whittle knew that at an early age and patented his design for a jet engine in 1930. After much obstruction he could start his first jet engine in 1937. Support of the British authorities was poor until Rolls Royce stepped in. After all Frank was “just an RAF captain” and no professor…

Almost for nothing ($ 800,000.-- ), the knowlegde of Frank Whittle came into the hands of the Americans. Just to say “Thanks” to them, for all the war materiel “lent” to Britain by the Lend Lease Act.
General Electric, Pratt & Whitney and Westinghouse were eager to use all the information.
All efforts soon led to the British Gloster “Meteor” and the American Lockheed “Shooting Star”.

Nazi Germany was a little late with the Heinkel jet engine, but was the “first” with a jet flight in August 1939. Several German engine builders designed and built jet engines during the war,  but the quality was very poor compared to the British engines.

Many pictures and historical film fragments, including Frank Whittle playing himself in a documentary about the “Wonder Engine”.

duration: 1¼ hours

The V-2


The presentation starts with a brief history of the rocket, German “Rocket-fever” (as a result of the Versailles Treaty in 1919), the development of Wernher von Braun’s "A" series by the German Army and the testing of the A4. And more important: how does this thing work?

After loosing the battle for Stalingrad the Germans choose a “wonder weapon”, their Last Straw… The A4 becomes the missile V-2. Testing takes place at Peenemünde in Germany. The British, suddenly aware of the existence of this weapon, bomb the place in August 1943. Production had just started. The Nazis move to the underground factory near Nordhausen. Prisoners of the hard labor camp “Dora” (a satellite camp of Buchenwald) work until their death in the very unhealthy galleries of “Mittelwerk”.

How did the Germans launch their weapons? The Hague and surroundings have the honour of becoming “Cape Canaveral behind the dunes”. Over a thousand V-2’s were launched from there, even right from the middle of the town. What damage did the V-2 do? How many lives were lost?

The end of the V-2 terror leads to the beginning of the Space Adventure, which ultimately leads to the “first step” of Neil Armstrong. Different rockets, same Germans...

Wernher von Braun plays a significant role in this story. His dream was about travelling to other worlds, like the Moon and planets.  His dream ended in building a weapon of mass destruction. But he gets a second chance and two decades after WW2 his rockets put people in space and eventually on the Moon. The dream has come true.

This presentation contains beautiful material which shows the preparation and launch of the V-2.

There are three flavours: strong, medium and light. Please contact me about this.

duration: 1½ hours for the "light" version

Pictures from space


Images from high above the Earth and in the vicinity of the Moon and planets have always sparked our imagination. Astronauts and unmanned spacecraft showed us intriguing worlds. Other than beautiful, these pictures are also useful. We can check the health of our crops on Earth and forecast the weather much better.`

This is not a show with the most beautiful pictures ever made, but the images illustrate the way they are made.

In the 60’s telescopes were not as good as today. The blurry pictures made us curious about what was really there. Very soon in the Space Adventure spacecraft made the first pictures of the Moon, Mars and the other near planets. But… taking a picture of Mars at a distance of 200 million kilometers, how do we get that on Earth?

The presentation shows us how those pictures were made and we’re going back in time to see how scientists got the best results with 1960’s technology.

I start with the old chemical photography, like the astronauts used in their capsules, although these cameras were heavily modified.

Then the vidicon television recording tube, used as a photographic camera. The first weather satellite “Tiros” had one, but “Voyager” used this way of taking pictures too. The vidicon was succeeded by the CCD chip.

Scanning is a widely used way of shooting pictures, used by Landsat, Meteosat and even the Viking Mars Landers.

The Russian Luna 3, that took the first picture of the far side of the moon in 1959, used a combination of photography and an on board “fax”. So did the Lunar Orbiters, in 1966 -67. LOR’s pictures produced a high definition photographic atlas of the Moon.

duration: 1¼ hours


Dakota, the allied workhorse


A presentation about and "around" the Dakota.

What can we expect in this presentation?
Well, how a dubious accident with an American Fokker airplane with wooden wings leads to “the plane that changed the world”. TWA, owner of the Fokker, asked the aircraft builders for an all metal plane and Donald Douglas took the bait. Douglas built a demonstration airplane, the DC-1, that was tested in a very modern way. The production version DC-2 soon followed. The need for a “sleeper plane” prompted the factory to build the bigger DC-3.

The DC-3 steps into the military world and a new word arises: AIRLIFT. The plane becomes the C-47, Dakota (named so by the British), C-53 Skytrooper, etc.

The Dakotas were used for delivering paratroopers, dropping supplies, airlift operations and flying from Lisbon to Londen with escaped pilots. The Dakota could also “snatch” stranded gliders off the ground. The Dakotas could land anywhere with their rugged landing gear. Sometimes they were 100% overloaded, but did what they had to do.

After the war Dakotas took part in the Berlin Air Bridge, Korea and even in the Vietnam War, as a flying gunship. About 200 are still in flying condition.
And then the anecdotes, like the DC 2,5 and the whistling C-47.

duration: 1½ hours


The Spitfire


The development of the British WW2 fighter, the Vickers Supermarine "Spitfire", according to specification F7/30 of the Air Ministry.

The performance and fame of the Spitfire in the Battle of Britain and the decisive role of the Hawker Hurricane in this battle

The reliable Rolls Royce Merlin engine, the World's most built aero engine of which the development kept up pace with the demands of Supermarine. The Merlin is very well known. Say: "Spitfire" and many people say: "Merlin!" and of course the other way around.

Some marks of the Spitfire are highlighted, because they are an important milestone in the history of the fighter. And of course the weaponry is not forgotten, just as the production of the complex Spitfire.

How good was the Spitfire compared to German contemporaries and in what roles was the Spitfire employed?

Restauration projects of the Spitfire -or how are they kept aloft?

duration: 1 hour


The Great War at the Western Front

...based on 8 places along the front



A war is terrible and fascinating at the same time. This surely applies to the Great War. It starts in the 19th century style, but becomes the first modern, total and technological warfare in history. There still are many traces to find of this war.

The Netherlands escaped the war by pretending being neutral, but we knew there was a war going on, because of blockades, shortages, stray bombs, thousands of mines washed ashore and a great loss of fishing boats and freighters.
A million Belgian refugees in the Netherlands made it very clear that something nasty was going on in the south. At the borders you could hear the guns pounding and see the "Electric Fence" built by the Germans to keep the Belgians in.

As a matter of fact the Great War is part 2 of a trilogy:

  • The French-German war 

  • The Great War

  • The Second World War

The presentation starts with the circumstances and events that led to this war. The life of the soldier is central: The Tommy (GB), Das Frontschwein (D) Le Poilu (F) en The Yank (USA).

The presentation brings us along the front on the basis of 8 visits, from West-Flanders to the Vosges. Every spot is a "Then and Now" story and also a hook for several subjects, like trenches, life at the front, poison gas, the development of the first tanks, trench-art, transportation, the air war, mining, the dug-outs, equipment, start of plastic surgery and treating shell shock.
It provides a kaleidoscopic view on the Great War.

So, there is something to learn from this presentation for everybody.

duration: 2 hours


The 14-18 Air War


This is a small part of the "Great War" but enlarged to a presentation in full.

The airplane matured during the Great War. The role of reconnaissance was very clear from the start. The Germans won the battle for Tannenberg because of their recce planes. Automatically the fighter developed as an answer to the hostile reconnaissance aircraft. Dropping bombs, first by hand and later from specially built bombers became a terror weapon against cities and so against civilians. Germany's first bombers were the airships, to intimidate the British. But halfway the war they found a way of shooting down the dreadful zeppelins. Real bombers soon followed and some were giants for their time and long after. 

The aircraft industry started in small workshops, but was soon booming, in giant factories.

We take a good look at the development of airplanes, the training of the pilots, their work and the stories of chivalry. 

The presentation ends with the precursor of the Royal Dutch Airforce. We started with just one hired plane in 1913. Acquiring warplanes was not that difficult. They just came out of the sky by engine trouble of fuel starvation: French and British planes in the South West and German planes in the East.

The audience will be surprised by all the developments achieved during the Great War and think: "What? Already in 14-18?"

duration: 1½ hours


The De Havilland DH.98 Mosquito



  Geoffrey De Havilland makes three important decisions concerning the new DH.98 “Mosquito” bomber:

1 The plane is unarmed and therefore very fast

2 It has a crew of only two

3 It is made entirely of wood

De Havilland chooses wood because of its great experience with this material and moreover it makes little use of scarce metals. Furniture makers, coach builders and piano builders could be employed. In this role those factories and workers could take part in the war effort.

The Mosquito is the first real “multirole combat aircraft” and was used as reconnaissance plane, bomber, fighter-bomber, night fighter, pathfinder and the fright of the German U boats.

Originally De Havilland had only a bomber in mind, fast but unarmed. All the gun turrets on the big bombers make such a plane very heavy. By omitting the gun turrets you can save a lot of weight and morerover, turrets cause drag and this reduces the speed. The Mosquito did not have turrets and by doing so it could  take a comparatively rather heavy bomb load, at great speed.

For the same investment the Mosquito could drop 4.5 times the bomb load of a Lancaster. In the cost of human lives the two crew Mosquito did also better than the big bombers with their crew varying from 7 - 10…

The “Wooden Folly” became “The Wooden Wonder”, of which ultimately 7600 were built. There are many video fragments to be enjoyed.

duration: 1¼ hours


Aero Engines


For technical chaps…

It’s about How Things Work. I do advise to choose the Piston Engines or the Jet. Not both in the same presentation. If the presentation takes place in an aviation museum or a museum in possession of aero engines, we can do a guided tour.

1 Piston Aero engines

  •         principle of the fourstroke engine

  •         the radial engine

  •         the in-line engine, like that of Wright and the Rolls Royce Merlin

  •         the rotation engine

  •         the sleeve valve engine like the Bristol Hercules

  •         the H-engine, like the Napier Sabre

  •         which was the most powerful?

2 Jet Engines

  •        the need for a stronger engine than the piston engine

  •        the history of the gas turbine

  •        the principle of the centrifugal jet engine

  •        the principle of the axial jet engine

  •        turbofans

  •        turboprops

Both subjects take ¾ hours each


Moments of the Industrial Revolution

The end of the 18th century was an era of great revolutions in North America and France. The British Revolution was quite different; their social revolution took place by the industrialisation of the country from the 1760’s onward.

The presentation starts with the British Industrial Revolution and some examples in the USA. All other Industrial Revolutions that followed sooner or later were more or less copies of the British situation.

Situations, developments and inventions led to the industrialisation of Great Britain:

1. the natural resources like coal, iron, copper, tin and chalk. 

2. the waterpower of rivers. 

Problems with ground water led to the invention of the first working steam engine by Thomas Newcomen. James Watt improved this engine and developed it into a rotational engine. This ultimately led to an unruly expansion of the industry.
Adam Smith thought about the division of labour, which made work done by unskilled workers possible -at a higher production rate. The interchangeability of parts made assembly of products a piece of cake.
Little training was necessary to make a fine product -together.

In 1760 many people worked at home; in 1820 many worked in factories. What happened?

We follow the developments in the 18th and 19th century and after that the situation in the Netherlands, which deviated strongly from the industrialisation in other countries.

The consequences of the industrialisation are of course not forgotten; the dark side like the living conditions, long working hours, exploitation  and diseases.

I have also version that is tailored to a female public.

duration: 1 hour 


ULTRA and Enigma



ULTRA is the code name of the total British efforts in decrypting the German ciphers of WW2. The Germans waged a very mobile war, so the messages had to be send by radio and this could be received by anyone.

The Germans never knew that the British and later the Americans could read nearly all traffic between commands and armies, squadrons and ships.

This was such an important and decisive source of information, that “Most Secret” was not enough. It became “ULTRA secret”, hence the name ULTRA. Because of safety reasons the source of information was always concealed.

The decrypting took place in the huts near Bletchley Park and the villa’s dispersed over the premises. At the peak nearly 10,000 people were employed in decrypting and processing the coded messages. Spread over Great Britain and non occupied Europe, 8,000 people of the “Y service” (wireless service) listened to the German coded messages. These were precisely written down and sent to Bletchley Park.

The code machine “Enigma” is well known, and in the twenties of the 19th century everybody could buy one. But during the war it became more complicated. The British, however, could keep on with decrypting messages, also helped by errors made by the German operators.

For the top secret German messages the complex “Geheimschreiber” was used. To decrypt those messages the British build the first computer, Colossus.

The presentation contains an historical summary of different methods of coding, shows how Enigma was used by the soldiers at the front (with help of the beautiful simulator of Dirk Rijmenants), how the messages were received, how to crack the code of the day and what happened with the information.

After the war general Eisenhower said: "Ultra has been decisive to Allied victory".

duration: 1½ hours


Red Ball Express

The Red Ball express is a tiny but important part of the logistic efforts just after the D-Day landings in 1944.

The story begins in Great Britain, that nearly sinks under the weight of soldiers, equipment, tanks, moveable harbours, PLUTO fuel lines and  an immense stockpile.

Just after D-Day the materials pile up on the beaches of Normandy. The Command expected a slow progress in taking down the German armies. However, from July onwards the fronts are moving very fast, so fast that problems arise for fuel and ammunition. The regular logistics are not able to cope and the Red Ball Express is established. 6,000 lorries drive day and night on specially allocated roads to bring the stuff at the front, a dangerous job.

This is a story of soldiers who drive the ever longer routes, after a few hours of training, with hardly time to rest well. Lack of sleep was the greatest enemy.

This is also the story of the GMC trucks, the Autocars, the Diamond T M20’s and other cars. And of black soldiers...

duration: ¾ hours


Target for Tonight



This presentation will suit a wide audience and is not technical.

During WW2 thousands of bombers passed the Dutch airspace on their way to targets in Germany, and back. One of the crew members was the bomb aimer.

The experiences of a now 98 years old British Royal Air Force veteran are the foundation of this presentation. He completed 22 missions, dropped food over the occupied Netherlands and made repatriation flights. The legendary British Lancaster bomber played a leading role in his story.

The presentation is about the work and the danger on board, the impact on the young crew members, the airplane and its bomb load and situations that really took place during and around the missions.

The presentation is easy to follow, even for those without prior knowledge about this subject.

(On request)

duration: 1½ hours and a break halfway


Kids presentation How does it work: the Aeroplane


A short presentation in which we learn about the first flights, air resistance, streamline, how a wing works (at two levels), the propeller, the propulsion, stearing, “light and strong”, the jet (at two levels) and brakes.

It’s intended for kids of 10-12 years of age, approximately.

At the end we fold a paper airplane and make it steerable.

duration: approx. ¾ hours


James Watt and the 
Steam Engine
James Watt 

This presentation was made in 2019, because then it was 250 years ago that Watt had patented his improved steam engine (1769) and 200 years since he passed away.

Watt improved the first capable (atmospheric) steam engine, made by Thomas Newcomen in 1712. He added a condenser and went even further. This 1769 engine was more economic. Fifteen years later Watt made a giant leap by making his steam engine double acting.
This is the engine that changed the world, because it provided a rotational motion, usable for the industry. Now the Industrial Revolution really took off.

We follow James Watt in his early days, his acquaintance with the Newcomen engine and his financial problems while building a better steam engine. Meeting Matthew Boulton was very important for him. This forward-thinking manufacturer, with his Soho Manufactory (then the biggest factory in the world) made it possible to live of building steam engines. Soho was the first mass production factory ever.

The framework of the story is the “Enlightenment” of the 18th century, a movement in which people did not take things for granted. No, they did experiments, did tests, observed. 
In 18th century Britain knowledge was spread by apprentices, scientific societies, like the Lunar Society and thousands of Coffee Houses in the country. You were more or less obliged to share knowledge. Hence the first (French) encyclopedia.
James Watt, Matthew Boulton, Erasmus Darwin, Josiah Wedgwood and many other members of the Lunar Society sometimes are called “Fathers of the Industrial Revolution”, or: "The friends who made the Future" (Jenny Uglow). 
Watt called the time in which he lived: “We are living in an age of miracles”.

duration: 1¼ hours


The Steam Engine Pumping Station of Medemblik


De Vier Noorder Koggen is a polder in the North West of the Netherlands. As you probably will know, our country lies for the greater part below sea level. It was not always like this. In fact we created our own problem for a part because of draining the bog, which caused the soil to go down. Other reasons are the rising of the sea level and the subsiding of the surface over ages. But in fact we are living in a bathtub.

The presentation shows the history of the land, from the most recent ice age into the Middle Ages and how we mastered the seawater by building dikes en using windmills. But windmills need wind and can only pump when the tide is not too high. In other words: the mills could not always do their job. That is the reason for building the auxiliary steam pumping station in 1869. After many alterations the new part of the pumping station was built. It opened in 1907 and replaced the last remaining windmills in the neighbourhood of the pumping station

You also learn about the use of steam engines, a producer gas steam motor and the return to steam again in 1924.

It provides insight in our struggle against the rain and seawater and this example stands for many other pumping stations.

Since 1985 the Pumping Station accommodates the National Steam Engine Museum. The building is an (industrial) monument and in possession of the District Water Control Board "Hoogheemraadschap Hollands Noorderkwartier".

duration: 1 hour




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