June 9, 1944, Bassinborne Air Base, Cambridge, England. At 7:22 in the morning, the First Sergeant Edward Kowalski, 31 years old and construction carpenter civil before the war, is stopped in front of a Boeing B17 g flying Fortress [music] that will never fly again. The B17 g, number 43 38,274, returned from a bombing mission over France 3 days ago.
An anti-aircraft gun German 88 muo hit the fuselage rear. You are abasing hit the rear fuselage. The projectile did not detonate, but opened a 1.4m diameter hole in the side port side. Just behind the turret waist. The pilot managed to land the plane, but now the B17 is doomed. [music] According to Force regulations Army Air Force, structural damage of that magnitude requires replacement complete fuselage section.
That means dismantling the plane, sending the parts to a repair depot specialized in England or the United States United States and wait 81 weeks for complete reconstruction. The eighth air force does not have 8 12 weeks, He has a war to win. Kowalski walks around the B17 damaged. Touch the edge of the hole. The aluminum is torn, not cut cleanly.
There is 40 cm of structure exposed internal. Stringers, reinforcements, wiring, hydraulic lines. Kowalski He is not an aeronautical engineer. Never He worked on airplanes before joining the Air Force. He built houses in Chicago, wooden structures, beams, columns, reinforcements. And while you look at the B17 damaged, Kowalski sees something that engineers do not see.
See a house with a hole in the wall. At 9:14, Kowalski walks to the office Lieutenant Colonel Harold Fisher. Official engineering maintenance of mood first bombing group. [music] Sir, I have a proposal regarding the B17 damaged. Fiser is reviewing reports of damage. [music] It has 23 B17 in land awaiting repair. 23 aircraft that they should be bombing Germany, but they are in hangars useless.
What kind of proposal? Sergeant? I can repair B17, number 43 38,278,274 in 5 days. [music] Fiser raises his head view of his papers. Kowalski, that plane has a hole in it. 1.4 m in the fuselage. Requires replacement complete section. It is not a 5 days repair, [music] sir. No I’m going to replace the section, I’m going to patch it.
Aluminum patches do not They work on damage of that magnitude. Ya we try. The vibrations Structural break the welds in less than 10 hours of flight. I’m not going to use aluminum, sir. I’m going to use wood. The silence in the office is absolute. Fiser looks at Kowalski as if he had just propose repairing B17 with cardboard. Wood.
Do you want to repair a bomber aluminum with wood? Yes sir. English oak 2.5 cm laminated thickness in three layers with resorcin adhesive. Reinforced with stainless steel bolts every 15 cm. Sealed with rubber compound synthetic. Fiser leans back in his chair. Kalski, Are you aware that a B17 flies to 370 km H at 7.6 6 m altitude, where the temperature is -40ºC.
And you want to put wood in the fuselage? Yes sir. The wood will shrink with cold. It will crack. The patch will come off in mid-flight. [music] The plane will depressurize. The crew will die. The wood of oak laminated in three layers with Resorcin adhesive does not crack -40 gr.
Sir, we use it in construction of bridges in Minnesota, where the temperature reaches -35º regularly and the B17 fuselage is not pressurized, [music] so depressurization no He is a factorist. Fiser looks at Kowalski for a full 10 seconds. Where do you plan to get English oak from structural quality in the middle of a war? Of the trees felled by German bombings, sir, there is a oak forest 3 km from the base that was hit by Quinto bombs last week.
The fallen trees are between 80 and 120 years. Exceptional quality wood. Yes you want to know how wood from trees bombed saved bombers from aluminum, please press that button I like [music]. Helps us share more forgotten stories like this. and Subscribe if you haven’t already. Fisher does not approve the method immediately.
Instead, he calls a meeting with three Boeing aeronautical engineers, two maintenance officers of the 8th air force and a structural engineer of the Royal Air Force. The meeting lasts 2 hours. Kowalski explains his method in detail. Engineers ask questions, many questions. [music] How do you calculate the structural load? No I calculate it, sir. I match it.
The aluminum of the fuselage has tensile strength of 310 mcales and thickness of 1.6 mm. laminated oak It has a tensile strength of 110 Mapasalts, [music] so I use 25mm thickness for compensate. Three layers of 8.3. 3mm each. How do you handle the thermal expansion difference betweenaluminum and wood? I leave a space of 3 mm between the wooden patch and the fuselage aluminum.
I fill it with synthetic rubber compound absorbs differential expansion and aerodynamics, a patch of wood will create turbulence. I sand the wood until that the surface is smooth within [music] tolerance of 0.5 5mm Then I cover it with doped linen fabric with cellulose nitrate, the same as old wooden airplanes. Finally I paint [music] with the same paint of the fuselage.
Boeing engineer Richard Patterson, takes notes throughout the presentation. Finally speak sir Kowalski. Your method is Mr. Kowalski. Non-conventional. violates principles basics of aeronautical engineering modern. Metal airplanes are not They repair with wood, I understand, sir, But Patterson continues, his calculations They are mathematically sound and Boeing experimented with construction metal-wood hybrid in the 1930s.
It worked. We do not adopt it for reasons of mass production, not for reasons techniques. Patterson looks at Fisher. If he Sergeant Kowalski is willing to bet your reputation on this, i I would recommend a controlled trial. Repair a B17, test it on the ground, then Try it in flight without combat load. If you survive 10 hours of flight without structural failures, then consider broader implementation.
Fiser, nods. Kowalski, you have authorization to proceed, but if that patch fails and kills a crew, You will face court martial. Understood? Do you understand, sir? June 10, 1944. Kowalski and four carpenters from his team walk towards the forest Oaks, damaged by bombs. Fifth one. They find 11 fallen oak trees.
The trees are between 90 and 130 years old. [music] The wood is dense, without knots, perfect. Using hand saws and axes, cut 2.5 m long planks length and 30 cm wide. They transport the wood to the base in a truck requisitioned During the next two days, Kowalski and his team process the wood. They cut it into 8.
3 mm sheets thick using a band saw industrial. They sand each sheet until smooth surface. They verify that there are no cracks or defects. June 13 they begin the repair of number B17 43 38,200 78,274. First they clean the damaged area remove torn aluminum. They expose the internal structure. [music] four vertical spars, six reinforcements horizontal.
[music] Then they make the patch, three layers of laminated oak with resorcin adhesive between each layer. The adhesive requires 24 hours for complete cure under pressure 8 kg per cm². kowalski usa woodworking clamps and weights lead to apply uniform pressure during curing. It is technology Xeno century carpentry applied to 20th century aviation.
On the 14th June, the laminated patch is cured. Kowalski adjusts it to the hole in the fuselage. The patch is 10 cm larger that hole in all directions to allow overlapping with aluminum intact. Kowalski drills 64 holes through the wooden patch and the fuselage aluminum. Each hole is spaced exactly 15 cm from the next.
Insert bolts 6mm diameter stainless steel with Lock washers on both sides. Tighten each bolt to exact torque 12 Nm using a torque wrench. No more, not less. Too much torque would crack the wood. [music] Little torque would allow movement. Then seal the perimeter of the patch with synthetic rubber compound. The compound fills the 3 mm space between wood and aluminum and creates a barrier airtight.
Finally, cover the patch with three layers of linen fabric doped with cellulose nitrate. Each layer requires 6 hours of drying. When the fabric is dry, sand it until completely smooth surface and paint with standard olive gray paint air force. Total time of repair. 4 days 16 hours. On June 15 at 10 hours hours. The B17 number 43 38,278,274 is taxied onto the track for testing in land.
Boeing engineers have installed voltage sensors in 12 points around the patch to measure structural stress. [music] Engine number three starts, then four, then two, then one. The four engines right array, [music] 1820, cyclon 1.2 horsepower each one roar at maximum power. The B17 vibrates, the fuselage flexes. Voltage sensors record data.
After 30 minutes at maximum power, engineers review the readings. The wooden patch experiences tension structural of 84 map scales. The surrounding aluminum experiences 89 scalemaps. Difference 5 megapascals. Inside the margin of tolerance, Patterson, the Boeing engineer, walks towards Kowalski.
The [music] patch is inside of specifications. I authorize flight testing without cargo combat. June 16, 1944. At 8:14 B17 number 43 38,278,274 takes off with test crewmission. 4 hour flight at altitudes variable up to 7.6 m without load bombs. No combat. The test pilot It’s Captain David Morrison, 29 years old, 48 combat missions.
Veteran with 340 hours in B17. [music] Morrison takes the plane to 3m, then A5, then A7.6. At each altitude perform maneuvers, turns, ascents, descents, changes of speed. The patch does not fail, it does not cracks, does not come off. At 12:6, Morrison lands. Your report [music] It is brief and direct. The plane flies normally.
I did not detect vibrations unusual. I did not experience any problems control. The patch works. The engineers inspect the patch after the flight. Zero [music] cracks, zero detachments, zero deformation. Patterson writes his report that night. The conclusion is unequivocal. The method laminated wood repair Designed by First Sergeant Edward Kowalski is structurally sound, operationally safe, operationally safe and can be implemented as a temporary solution for B17 with fuselage damage that Otherwise they would require replacement complete section. On June 18, the
Lieutenant Colonel Fiser authorizes complete implementation of the method. Kowalski is ordered to train all carpenters and technicians structures of the first, group of bombing. During the next two weeks, Kowalski teaches his method to 47 technicians. 11 additional B17s repaired using wooden patches.
The 11 planes They return to combat. Missions fly about Germany. They face fire anti-aircraft. They withstand temperatures of -40º at 7.6 m. The patches do not fail. Write oak in the comments if this is story is surprising you. July 1944. The news of the Kowalski method extends to other bombing groups the eighth air force.
The commanders group in Turley, Buddington, Molesworth and Grafton Underwood request Let Kowalski coach his teams. The command of the 8th air force takes a decision. Convert method Kowalski in doctrine. Standard field repair for B17 with damage larger fuselage. Kowalski spends July and August 1944 traveling between 14 air bases in England.
He teaches his method to 340 technicians structures and carpenters. The method is standardizes. Each base receives a kit of wood repair including resorcinol adhesive 40 kg, bolts stainless steel, two units: synthetic rubber compound 20 [music] L, linen fabric 200 m², flax nitrate 200 m², cellulose 15 L, tools specialized carpentry and each base identifies local sources of oak, forest is damaged by bombing, abandoned farms, buildings destroyed.
War wood becomes salvation for war bombers. Between June and September 19440 B17 are repaired with wooden patches [music] using Kowalski’s method, 340 aircraft that would otherwise have Been grounded for 81 weeks. waiting for repair in warehouses specialized. Those 340 B17s flew 8.74 combat missions over Germany during that period.
They dropped 14.2 tons of bombs. 34 They were shot down by enemy fire, but none zero failed because problems with wood patches. Aeronautical engineers eventually they carried out studies details of the method. They discovered something fascinating. wooden patches Kowalski laminate were not only good enough.
In some aspects were superior to aluminum. [music] Wood absorbs vibrations better than metal. The patches of wood reduced structural fatigue in the surrounding aluminum in approximately 12. The wood-headed B17s had fewer fatigue cracks than B17 without damage. Additionally, wood is easier to repair in the field than aluminum.
Weld aluminum requires equipment specialized, stable electricity and technical highly trained. [music] Laminar wood requires saws, adhesive and clamps, technology that any carpenter can use. After the war, Boeing incorporated some lessons from Kowalski’s method in his field repair manuals. The section on temporary repairs with non-standard materials includes procedures for wood patches in emergency situations.
edward Kowalski was promoted to non-commissioned officer teacher in September 1944. He received the soldier’s medal in October. The summons said, exceptional technical innovation that returned critical aircraft to operations combat and contributed significantly to the war effort ally. After the war, Kowalski returned to Chicago, opened a business construction, built houses, buildings commercial and three wooden bridges laminated.
Never worked in aviation again, but every time I saw a plane in the sky was smiling. He died in 1989 at 76 years old. His obituary in the Chicago Tribune mentioned his service in the SecondWorld War. Didn’t mention the 340 B17 which he saved with oak wood. Today [music] Kowalski’s method is no longer necessary. Modern airplanes use composite materials, alloys advanced and repair techniques sophisticated.
Nobody repairs fighter planes with wood. But in 1944, when the eighth air force needed bombers in the air and had no time For formal repairs, a Chicago carpenter looked at a damaged B17 and saw a house with a hole in the wall and applied the simplest solution, put a plank over the hole. [music] Sometimes the most difficult solutions elegant do not come from laboratories high technology, [music] come from carpenters who understand structures, they come from people who see problems complex and sees simple solutions. The
war is not won only by pilots and bombers, carpenters win that turn fallen trees into airplanes flying What do you think of this story extraordinary? Did you know how wood oak saved aluminum bombers in full war? Leave us your comment and subscribe to our channel. Every week we bring verified stories and fascinating that changed the course of the history.
Activate the bell so you don’t get lost no episode.
