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On Heather's Workbench - Strike Hard, Strike Sure: RAF Bomber Command 1940


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Hi Heather

 

I've just have a catch-up that's covered the last few weeks. And a while back there was some puzzling over the ventral turrets of the early planes. Serendipitously (maybe!), I found an animation by a YouTuber today on the Short Stirling FN25 ventral turret - so,  just in case it's new to you:

https://www.youtube.com/watch?v=RUBqaqqvk2o

 

Enjoying your thread! Thanks for the fun.

 

Matt

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13 minutes ago, MattJ said:

I found an animation by a YouTuber today on the Short Stirling FN25 ventral turret


Coo! That’s a find! Thank you. It probably asks more questions than it answers, but its better than anything else I’ve turned up so far.

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Hey Heather, you may already have come across it, but there's a website call World War Photos. In amongst a ton of other stuff are several, very good pages of photographs of the Stirling. Many at the factory, loads of excellent interior shots etc. If I remember correctly, there are a couple of the ventral turret.

Hope it helps.

Regards

Pete

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Gunk arrived, so time for a little experiment.

 

Airfix Stirling

 

The ready-mixed epoxy resin is thick, and I’m not sure I can drop it into the window apertures without it forming a meniscus. I may need to make a test mule for experimentation.

 

Under the UV, the stuff sets rock solid in about 10 minutes. 

 

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As reported in the previous post, I had a little experimenting session with the UV epoxy resin. I’m not naming brands, since it’s a generic starter pack of stuff designed for crafters and jewellery makers. It came with a large pot of resin, a USB-powered LED UV lamp gizmo, and some silicone rubber tools. The resin cures under the UV somewhere between 10 and 30 minutes, depending on the thickness I suppose.
 

My first effort was to stick some 3M Magic Tape across the window apertures on the outside of the fuselage. I rubbed the tape down to try and avoid the resin seeping under it. With the fuselage flipped over, I dropped in some the resin, hoping to get a thin film in the aperture. While the resin cured hard and clear, the result had a thicker edge round the frame, giving the classic "bottle bottom" appearance. I was able to carefully push the resin out of the frames and tidied up for a second attempt.

 

Attempt number two followed the same basic procedure as before, but this time I filled the aperture completely. This was more successful, but I managed to trap a couple of air bubbles in the resin. It also didn’t remain crystal clear. Once the tape was removed, the outer surface, affected by the tape adhesive probably, was ever so slightly frosted. It was also slightly tacky, which meant I probably hadn’t let it cure long enough. Impatience is one of my many personal failings. The resin kit suggests IPA can be used to wipe away sticky residue, but all that did was cloud the surface more.

 

I went to bed, happy with tests, and scheming improved methods. 
 

Airfix Stirling

 

One notion was that perhaps I should continue to pour the resin to the full depth of each aperture, worked carefully to avoid bubbles, but put the tape backing on the inside of the fuselage. Pouring for outside should result in the more or less shiny surface I want, and what happens inside isn’t important. This is what I am trying as I type. A slightly longer curing session is also being tried, which will hopefully cope with the deeper pour.

 

More later.

 

I have also scanned the fuselage sides to give me a template for the aperture sizes. I’ll draw up and cut masks later on.

 

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Oh…

 

Airfix Stirling

 

…bother! Bloomin' bubbles.

 

The stickiness is caused by the tape adhesive, I discover. Right, ping these out and try again, this time hopefully getting rid of bubbles.

 

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Heather have you tried pricking the air bubbles with a pin? 

To get a smooth surface try trapping a sheet of shiny celluloid at the window surface.

UV resin will polish to a flat surface if you have to try for a 'mechanical shine' that way.

 

But on the whole, wow already.

 

Looking fabuloso.

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4 minutes ago, perdu said:

Heather have you tried pricking the air bubbles with a pin? 


I have, Bill. It works sometimes, depending on how deep the bubble is in the layer, or I end up just chasing the perisher around to no avail! I’ve found it best to carefully work the resin with one of the rubber tools to try and prevent bubbles from the outset. Not always successful, but I’ve got loads of resin to play with. I also try to let the stuff self-level to give a smooth finish, though I am going to try to sand and polish as well.

 

It’s slow progress, mainly down the tiny UV lamp meaning I can’t expose a whole side at once. The resin will cure in daylight, but it takes a lot longer. Still, I’m encouraged by what I’ve achieved so far. 

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20 minutes ago, woody37 said:

Sorry I'm late to the party Heather ,but loving what you're doing to this old Stirling. Great idea with that epoxy stuff

 

9 minutes ago, Brandy said:

I'd say that last shot looks like a success, and a lovely shine on it too!

 

Cheers chaps!

 

I've just finished both halves of the fuselage. One side is now sanded and polished, and I'm about to do the other.

 

I'm a bit lazy because I don't go for the highly polished look on most transparencies. I reason that the glazing material was Perspex, and tended to yellow and fog with age and the elements. I do want the Stirling windows to as clear as possible, within limits, as the aircraft I'm modelling wouldn't be more than a couple of months old. Mind you, there's nothing to see inside the fuselage, so a crystal clear window isn't a lot of use!

 

Now I've got the stuff, I shall be looking to see what other models it could be used on. Immediate thoughts are the De Havilland Albatross and Flamingo waiting their turn on the bench. I will find a test mule so I can experiment with pouring the resin in thinner layers to see if it improves the overall appearance.

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I know you are experimenting with the windows -- you might try this to get smooth on both sides. Cut a piece of tape slightly larger than the hole of the window and place it sticky-to-sticky on another larger piece of tape. Then when you stick the larger tape inside the fuselage it will be the non-adhesive side that meets the resin. If there is a tiny amount of seepage it won't matter as much as it will be inside the fuselage. But it should allow for a smooth surface on both sides of the window.

 

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I’ve been ploughing into the Stirling build, throwing the odd titbit of prototype information out here and there. It’s time, perhaps, for another lengthy post looking at the aircraft’s design and early development in a bit more detail.

 

As already noted, the Stirling was born of the Air Ministry’s specification B.12/36. This specification was circulated in July 1936, inviting tenders from the main British aircraft and engine manufacturers. The specification didn’t stipulate any particular engine, but did lay down a limitation on the wing span, and to the size of the bombs the type would be expected to carry.

 

The myth has always been the 100ft wing span limitation was to accommodate the new type in standard RAF hangars. The standard hangar of the time was larger than that, and the specification actually expected routine maintenance to be done in the open. It should be noted the reason for the wing span limitation was more down to the Air Ministry wanting to limit the overall size of the aircraft. Worries were voiced that a very large aircraft simply wouldn’t be able to operate safely from typical bomber airfields, which were pretty much universally grass fields at the time. For really heavy loads, it was expected the new aircraft should be capable of being launched by catapult, chiefly because engines at the time were not expected to provide sufficient power for a normal takeoff at the full load capacity. It was also expected that the new aircraft should be easily broken down into manageable pieces that could be transported by road to maintenance centres. The centre fuselage, for instance, was not to exceed 35ft long, 9ft 6in high and 8ft wide. These sorts of restrictions meant the designers had to be a bit creative about where the bomb load was to be carried.

 

The Air Staff had discussed the types of bombs the new design was to carry. No bomb heavier than the 500lb general purpose was expected to be deployed in any future conflict, and such things as 4000lb, 8000lb and 12000lb bombs were beyond comprehension at the time. The designs submitted to B.12/36, therefore, were to carry a large load of 250lb and 500lb general purpose bombs, only just coming into service in 1936. A 2000lb bomb was also being introduced, but it was considered this weapon wouldn’t be used against land targets, designed as it was for use against heavily-armoured capital ships. The B.12/36 specification omitted the requirement for the new bomber to carry torpedoes. This oversight, perhaps intentional since the parallel P.13/36 specification did include torpedoes, would lead to limitations in the Stirling’s operational usefulness.

 

Tenders for designs to B.12/36 were submitted by Bristol, de Havilland, Vickers-Armstrong, Armstrong Whitworth, Vickers Supermarine and Short Brothers. Only the last two were given orders, and work began on detail design and prototypes. I’m not going to get into detail about the Supermarine Type 317 and 318, having mentioned them in a previous post. Suffice to say the two prototypes were under construction at the outbreak of war in 1939. Supermarine, however, was a small company, and found themselves virtually swamped with orders for their small fighter and the Walrus amphibian. The bomber prototypes were worked on in a piecemeal fashion at the company’s Woolston, Hampshire, factory, until late September 1940 when a Luftwaffe raid destroyed the aircraft and most of the drawings associated with them. The Air Ministry cancelled the order in November.

 

Meanwhile, in Rochester, Kent, Short’s design team headed by Claude Lipscomb and Arthur Gouge had been working on what was to become the S.29 Stirling. The first proposal had a wing design based on the Sunderland, with a span of 112ft and large Gouge flaps. Wikipedia explains:

 

Quote

The Gouge flap, invented by Arthur Gouge of Short Brothers in 1936, allowed the pilot to increase both the wing area and the chord of an aircraft's wing, thereby reducing the stalling speed at a given weight. This provided the benefit of a shorter takeoff distance for a given load, a shorter distance to achieve a given height and a lower takeoff speed. This type of flap, in spite of its use on successful aircraft such as the Short Sunderland and the Short Stirling, was limited to use on aircraft produced by Short Brothers.

 

In operation, the flaps would slide out and backwards, extending the chord, rather than dropping into the airflow. According to Short’s calcuations, the design would have an excellent high altitude performance, and would have been able to operate from existing airfields without assisted takeoff systems. The Air Ministry send Short back to the drawing board, stipulating the 100ft wing span of the original specification. The revised design had a wing span of 99ft, with increased flaps to 48 per cent of chord to help maintain takeoff performance. Two prototypes were ordered to the revised design.

 

To test the characteristics of what was to be Short’s largest land plane for a good while, as well as its first with retractable undercarriage, it was decided to build a half-scale wooden flying version. Assigned S.31 in the drawing office, the miniature Stirling had room for a test pilot and observer. Its wings were based on the Short Scion Senior, a four-engined civilian monoplane, and it was powered by four Pobjoy Niagara radial engines. Opening bomb doors and retractable undercarriage was fitted so their effects on the flying behaviour of the the full-sized aircraft could be observed. The S.31 took the air for the first time from Rochester on 19 September 1938, with the company’s chief test pilot, John Lankester Parker, at the controls. The small plane was eventually flown to the A&AEE at Martlesham Heath for handling trials and some wind tunnel testing for alternative defensive systems. Recommendations came back that the Stirling’s wing incidence should be increased to 6.5 degrees to keep the aircraft’s takeoff and landing distances within certain limits. With tooling for the full-sized aircraft already under way, such a change would mean a major redesign and delays to the delivery of the aircraft. It was decided to increase the length of the main undercarriage legs, and this modification was made to the S.31 for testing. Various other modifications were made, which replicated various the changes on the Stirling. The S.31 continued to be flown, logging 110 flights before it was written off in a takeoff accident in February 1944.

 

The first prototype Stirling had its maiden flight from the Rochester site, with Lankester Parker at the controls, on 14 May 1939. The big plane handled well, but a brake seized on the port main wheel on landing. The aircraft slewed and the undercarriage collapsed. The first prototype had to be written off, and the undercarriage had to be redesigned to make it stronger. The second prototype didn’t fly until December 1939. L7605 was eventually flown to the A&AEE at Boscombe Down in April 1940 for testing and acceptance trials.

 

The RAF’s Scheme L expansion plan called for 3,500 heavy bombers to be delivered by April 1942, around 1,500 of which were to be the new Stirling. Such numbers meant Short began building aircraft at the Short & Harland factory in Belfast, plus Austin Motors at Longbridge providing a third production line, as well as various subcontracted firms for smaller components. A new shadow factory near Swindon was also brought on stream. The first production Stirling from Rochester flew in May 1940, but Belfast’s first aircraft flight wasn’t until October. On 9th August 1940, Short’s Rochester factory was attacked by the Luftwaffe, destroying six newly-completed aircraft, and another six destroyed by an attack on the Belfast factory a week later. Deliveries were also slowed as priority was given from May 1940 to other aircraft already in production. A total of 15 Stirlings had been delivered by the end of 1940.

 

When I get time, the next historical post will describe the Stirling in more detail, and briefly cover how it was developed during the war.

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The Air Ministry's restriction to 100ft came from trials of prototype bomber/transports in the early '30s.  There were means of getting aircraft into hangers through doors smaller than their wingspan, but these were clumsy and slow.  One thing often mentioned is that the B-17 had a 100 ft wingspan, though with a smaller payload.  In plan view the wings of the two types are remarkably similar.   Bomber Command's hangar doors were 126ft wide, though overseas 100 ft was the norm.

 

It has been suggested that the problems arose from Shorts not being the Air Ministry's ideal choice of a manufacturer, because of its lack of experience with military requirements.  It is true that the three British companies normally linked to large military aircraft (Vickers, Handley Page and Avro) were fully committed to other types.  So Shorts and Supermarine were chosen - it was entirely understandable (then) that the Spitfire was not expected to place as much pressure on the company.  The Supermarine design is very interesting in comparison - initially a much smaller wing (it grew in development), a thinner fuselage and innovative bomb storage.  It does show what has been suggested: Shorts didn't realise that requirements were there to be argued about rather than followed slavishly, providing a good case could be made.

 

The comment about the 2000lb bomb I think understates the importance of this, especially in the disproportionate length of the Stirling,  Dropping the requirement to 6 rather than 7 such bombs would have meant a shorter aircraft with a steeper ground angle (than the original design) maybe giving an acceptable compromise on take-off run and thus avoiding that G.awful undercarriage.  This would have helped the aircraft's key problem of excess weight - on the other hand, of course, it would have meant a larger fin and tailplane which would have brought some of that weight back.  

 

It is interesting that the Gouge flap didn't increase the camber - perhaps switching to Fowler flaps which increase chord and camber would have been a better approach?

 

Basically the Stirling was basically a poor design which left the design team "firefighting" a series of problems.  At the core was poor management by Shorts, which was considered so bad that the company had to be nationalised in the middle of the war.

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Interesting historical info on the plane. I picked up the book We flew by Moonlight by Ralph Campbell at a model show on the weekend. He flew Stirlings later in the war when they were being moved out of Bomber Command roles. They had a secondhand kit at the show but I've got myself on a short BCATP leash. Looking forward to watching your build as I read the book.

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What I’d really like to be doing is fiddling about with the Stirling.

 

Distractions


What I’ve actually been doing (aside from a very delayed To Do List from August 2022) is dealing with this lot. Sixteen brass PE coaches, Great Eastern Railway, 1/76th scale, a commission build I have regretted taking on from the start! 
 

Distractions

 

Happily, I’ve just finished fitting all the wire handrails and door tee-handles to the bodies. After a bit of solder tidying, these will all get a session in my ultrasonic bath to get rid of crud and flux residues, and to encourage anything not soldered properly to come adrift.

 

The next big job will be working out how to fit the bodies to their underframes. The things I do for money!

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If I had my life again, I would build O gauge stock based around Hastings where I live, 1900-1910. I could run LBSC, SER and SECR and the odd Chatham. Pretty, and much better than 1/76!

 

Back to reality. It takes me an age to finish a single Airfix kit OOB.

I cannot even comprehend the task that pile of brass sitting on your desk signifies. (15!!? 🫣)

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1 hour ago, Heather Kay said:

What I’d really like to be doing is fiddling about with the Stirling.

 

Distractions


What I’ve actually been doing (aside from a very delayed To Do List from August 2022) is dealing with this lot. Sixteen brass PE coaches, Great Eastern Railway, 1/76th scale, a commission build I have regretted taking on from the start! 
 

Distractions

 

Happily, I’ve just finished fitting all the wire handrails and door tee-handles to the bodies. After a bit of solder tidying, these will all get a session in my ultrasonic bath to get rid of crud and flux residues, and to encourage anything not soldered properly to come adrift.

 

The next big job will be working out how to fit the bodies to their underframes. The things I do for money!

A glutton for punishment aren't you? 

Sure you will beat these into submission in due course, likewise the Stirling. 

Kevin 

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2 hours ago, Samuraiwarrior said:

Sure you will beat these into submission in due course


Oh, they’re getting there. I’ve now got to a stage where I have bodies and underframes ready to be mated, bogies built but needing detailing, and internals and roofs to be sorted out. If I put my heart into it I would have them more or less ready for paint in a couple of months. Life, however, seems to have other plans, so it may well be a bit longer.

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With the Ireland v England test match at Lord's burbling away in the background (what? Ireland take a lead in the second innings on day three? :blink: How? What?) I had a pleasant day fiddling about with a Stirling.

 

Airfix Stirling

 

The early version I want didn’t have the twin pitot tubes under the nose, so the slot needed filling. Likewise, the chosen version also didn’t have the towel rail aerial under the rear fuselage. To plug the slots I added some strip across the inside, then stuck strip in. This has since been trimmed back and both plugs will get a smear of filler once the fuselage is joined together.

 

Airfix Stirling

 

While in plugging mode I filled the mid-upper hole with scrap material. It’s more or less at the right height to match the fuselage now, but will be filled and finished once the fuselage is joined together.

 

Airfix Stirling

 

While most of the kit hadn’t suffered from warping during its long sojourn in the box, I had noticed the forward part of the port fuselage half had a twist. Some careful testing followed, with the bomb bay and flight deck dry-fitted to see if the twist could be persuaded to go away. It could, but it’ll need some serious clamps and possible reinforcing with epoxy resin.

 

Airfix Stirling

 

Dry-fitting has revealed the fuselage needs quite a bit of help to align. There’s a distinct lack of pegs and holes along the top edge. In the fashion of short-run and vac-form kits, I’ve added some scrap strip to help with alignment. Getting the bomb bay floor deck in place needed clamps.

 

Airfix Stirling

 

the cockpit rear bulkhead also showed some mild twisting. With only guide strips on the fuselage, I added some styrene blocks to hold the bottom in place on the floor while another clamp held things as the cement set. My aim has been to get the basic flight deck together to then assess what detailing I can do.

 

Airfix Stirling

 

There is nothing for the bomb aimer's position. I don’t need to worry about the wireless op's area as it behind the bulkhead. The instrument panel and flight deck floor, plus the pilots' seats all need detailing, as does the navigator's station. That said, for 1966, it wasn’t all that bad.

 

Next, then, I shall spend hours poring over photos and drawings for the flight deck to see what goes where. I really don’t think the fuselage will be buttoned up this weekend.

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