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Old 07-23-2023, 07:44 PM
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Tyler Durden Tyler Durden is offline
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De Havilland Comet 1: Beginning my first ever design!

After having built probably thirty or so models over the last several decades including tanks, ships, and of course aircraft, I have decided to put my abilities to use and start designing models of my own.

I have always loved the de Havilland Comet since I first read about it as a boy. In my opinion it is probably the most beautiful jet airliner ever built with the exception of the Concorde. With the engines recessed into the wing roots, sleek flush riveted panels, streamlined nose design and high speed with elegance to match it was truly revolutionary and set the standard for what was to follow. And in forging a new path it also suffered tragedy in that the design was simply too advanced for the knowledge of the day. Several Comets were destroyed in catastrophic explosive decompression incidents due to metal fatigue caused by pressurization and depressurization cycles over normal operation. The recovery of the pieces of the aircraft from the bottom of the Mediterranean and subsequent accident investigation was also groundbreaking and set the standard for all subsequent aircraft accident investigations. Suffice it to say, if it hadn't been for the Comet being first into service, the Boeing 707 would not have been the blockbuster success that it was, gaining from the painful lessons of the Comet, applying them, and avoiding the same fate.

The Comet I have chosen to model is a Comet 1, and will wear the livery of B.O.A.C. G-ALYP, which was the first Comet to fly paying passengers and was later the first to be lost to explosive decompression with the loss of all on board. I will be designing it in 1:33 scale with a complete interior, detailed cockpit and landing gear, separate control surfaces with options for control surfaces as configured for takeoff, landing, and high speed flight, and aluminum foil clad skin courtesy of the excellent tutorial by forum member Gil.

Since I have no experience designing models but experience with Fusion 360 the model will first be designed in that space which will be used for making the internal frames, but eventually I will export it in a form suitable for rendering and unfolding in Blender or some similar program.

So far I have the fuselage worked out with the location of all the frames. Luckily there is a huge amount of material available on the Comet and plenty of very detailed measurements, and I have a set of the maintenance manuals for the Mk 1 version along with the manual for the Ghost engine.
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De Havilland Comet 1: Beginning my first ever design!-screenshot-2023-07-23-185655-1-edit.jpg   De Havilland Comet 1: Beginning my first ever design!-screenshot-2023-07-23-185813-1-edit.jpg   De Havilland Comet 1: Beginning my first ever design!-screenshot-2023-07-23-191423-1-edit.jpg  
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Old 07-23-2023, 10:51 PM
RyanShort1 RyanShort1 is offline
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Originally Posted by Tyler Durden View Post
Suffice it to say, if it hadn't been for the Comet being first into service, the Boeing 707 would not have been the blockbuster success that it was, gaining from the painful lessons of the Comet, applying them, and avoiding the same fate.
I mean, we can give some credit to the Boeing guys. It's not like they weren't innovating as well.
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Old 07-24-2023, 03:39 AM
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The Comet was innovative but it was essentially a 1950s philosophy aircraft. It was built on the assumption that flying would remain a luxury experience for low passenger numbers, whereas the 707 was designed to push more seats for a higher volume economy. This made it more of a commercial risk, but one which ultimately paid off. The 707 could do almost double what the Comet could in seats, range and engine power.



A common myth is that the fatigue cracks were caused by it having rectangular windows. In fact the windows were rounded at the corners and they were not the cause of the catastrophic fatigue, rather it was an ADF aerial cutout on the roof. Needless to say, the disaster was a consequence of the rush to be first and the politics of the British aero industry at the time, which led to the use of underpowered engines and thus the dangerous weight cutting scheme. This is also why most Comets were largely unpainted.
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Old 07-24-2023, 08:51 AM
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wow cant wait to see more of this a great aircraft and at 1/33 scale as well
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Old 07-24-2023, 09:22 AM
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Quote:
Originally Posted by Siwi View Post
A common myth is that the fatigue cracks were caused by it having rectangular windows. In fact the windows were rounded at the corners and they were not the cause of the catastrophic fatigue, rather it was an ADF aerial cutout on the roof. Needless to say, the disaster was a consequence of the rush to be first and the politics of the British aero industry at the time, which led to the use of underpowered engines and thus the dangerous weight cutting scheme. This is also why most Comets were largely unpainted.
Finally someone gets it right!

There were other contemporary pressurized aircraft that used square windows (they weren't actually square since they had rounded corners)and the misconception probably came about due to that aerial cutout which was identified as an aerial window in the investigation reports and from there likely entered common perception as a failure of the windows due to them being square. Later Comet versions switched to round windows and thus the perception was born that this had been the cause of the accident when in fact it was a measure to speed up production as round windows were easier to install.

The prototype and the fuselage sections used in testing and pressurization tests used a kind of glue to bond the aluminum as this was able to replace rivets in many areas, and was stronger than riveting. Later, the production article used glue but also reverted to rivets likely due to speed of production, but the rivet holes were punched which introduced stress points and microcracking, as opposed to drilling which didn't have the same issues but was more labor intensive.

You're right about the engines as well; the Comet had been designed with large enough engine fairings and engine bay that it could accommodate the Avon axial flow jet engine in development by Rolls Royce, while the Ghost radial flow turbine was only meant as an interim measure. Upgraded Ghost engines were used on the 1A version of the Comet while the Avon was finally ready and available with the Comet 4 which had a substantially lengthened fuselage and much higher passenger capacity as well as much longer range. It was never a huge success as by the time it entered into service there was little advantage to purchasing them over Boeing products which as another forum member pointed out were able to carry far more passenger volume and were produced in far greater numbers as well as being more economical to operate. Still, the Comet is by far the more elegant aircraft and was aimed at a clientele for which luxury and speed were more important than cheap tickets.
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Old 07-24-2023, 01:23 PM
Siwi Siwi is online now
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I will admit to having watched Mentour Pilot's recent-ish video on the Comet - have a hazy memory of a BBC documentary from about 2000 which did little to dispell the 'window' misconception. Another interesting point of note is how many UK-published books from the last quarter of the 20th century tend to brush off the crashes as an unfortunate side note then overstate the technical and historical importance of this aircraft beyond simply being the first jet airliner. It's almost like some kind of denial complex as the British aviation industry was at that time imploding and being absorbed into a multinational European company.
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Old 07-24-2023, 05:48 PM
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love the comet!!
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Old 07-25-2023, 01:38 AM
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Butelczynski Butelczynski is offline
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That's excent news. I was expecting Aaron Murphy to design one since he loves such subjects but I welcome yours. Canada had a number of early Comets.

Canadian Warplanes 6: Jets, de Havilland DH.106 Comet
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Old 07-25-2023, 07:02 AM
Petestein Petestein is offline
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I flew the Comet IV when it was used by the Latin American "AREA" airline. Extremely smooth and reliable aircraft, Looking forward to a highly detailed Comet card model.
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Old 07-25-2023, 08:13 AM
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Tyler Durden Tyler Durden is offline
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Quote:
Originally Posted by Butelczynski View Post
That's excent news. I was expecting Aaron Murphy to design one since he loves such subjects but I welcome yours. Canada had a number of early Comets.

Canadian Warplanes 6: Jets, de Havilland DH.106 Comet
I checked out that site. Lots of good images I had not come across before in any of my reference material!
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