RAF after BoB: mid-term strategy, tactics technology?

[wuzak]

It's just not right.....

A drawing from a guy named Mossie

Supermarine Spitfire and Seafire

It doesn't seem as if the Hercules was considered for any single engine fighter. Having said that, someone will prove me wrong.

Also, when was teh Hercules available in quantity? The Beaufighter II was built because of the possible shortage of Hercules.

 

[Shortround6]

So a quick-and-dirty conversion of the standard Hercules power-egg installation to fit the Spitfire firewall, with some tin stuck on behind to make it look nice, would be a pretty good start.

Although the dry weight of a Hercules is about 500 lb greater than a single-stage Merlin (or about 300 lb more than a two-stage), once the weight of the cooling system is also considered, there really can't be much in it weight-wise. And the Hercules is of course shorter than a Merlin, so installed on the same firewall in a Spitfire V would give pretty much the same balance.

The cooling system of a two stage Merlin was several hundred pounds heavier than a single stage Merlin. The radiators and intercooler were behind the CG so taking them out and adding weight ot he nose does get a bit tricky, (more ballast in the tail?), they had to add ballast just to fit the variable pitch/constant speed props.

And I really want to a see a Spitfire fitted with a Hercules with that honking big airscoop right in front of the canopy

 

[tomo pauk]

The war time Merlins dictated a single airscoop under engine, yet there was a fair number of Merlinized A/C with 'bifurcated' intakes. Should work for Hercules, too. Or, locate the scoop at 10 or 2 o'clock, rather than at 12 o'clock position.

...
It doesn't seem as if the Hercules was considered for any single engine fighter. Having said that, someone will prove me wrong.

Bristol was proposing the Type 153; a bit about it: link.

Also, when was teh Hercules available in quantity? The Beaufighter II was built because of the possible shortage of Hercules.

Both 4-engines Halifax and Stirling were to be powered by Hercules engines, so I guess that a single engined fighter might get some of the Hercules without those bombers taking much of a hit.


A less controversial topic - water injection for the Merlin. Per Morgan Shacklady: the Merlin II Special was tested with water injection, during 1938 (!). Combined with 110 oct fuel, boost achieved was +18.5 psi, 1450 HP power. With special fuel (noted as 'SR24'), it was +25 psi, 2150 HP. Engine life was cut back severely on there powers.
The water injection could be an useful addition for the Merlin 45, we could probably go to +18 psi there, without much damage to the engine? The inter-cooling effect would mean that also altitude capabilities are improved over the usual Merlin 45.

 

[Shortround6]

Hercules carb intake was pretty high up, almost level with exhaust ports.
Spitfire didn't have the best forward and down vision as it was. The radial is not going to help and sticking big air intakes anywhere in the 3 to 9 o'clock positions makes it even worse.
The straighter and least amount of turns in the inlet duct is going to give the best ram effect. On the twins it did one 90 degree bend. Go much below the 1 to 11 o'clock positions and you are dealing with multiple bends, 3 or 4.

 

[nuuumannn]

The Tornado's installation in 1940 was different to the Tempest's in 1944.

I'm well aware of that and if you re-read my post, it says, "but Hawker were working on that installation on the Tornado in 1940", meaning a Centaurus installation. The point I'm trying to make is that Hawker had been pondering it for some time and that I'd like to see confirmation that the BMW 801 installation in the Fw 190 had an impact on the Tempest and Fury, if it exists. I'm sure it would be interesting reading.

Yep, SR, the downdraught carb is going to be the thing, unless clever cowling is thought up where the intake is in the top lip of the cowl, like the cowl on the Zero.

Not sure what a Hercules Spit is going to do apart from ruin the aerodynamics. Why not go for a Griffon engined Spitfire that early in the piece? Fairey approached Rolls-Royce in 1938 and RR used the old 'R' derived Griffon - in its first incarnation bench tested in 1933 - and one was running a year later. By late 1939, Rolls had advised Supermarine of the potential of the Griffon, but in mid November Supermarine advised RR that it wanted to concentrate on the Spit III and the Merlin XX, but three weeks later changed its mind and began examining a Griffon engined Spitfire. Hows about anticipating this and approaching RR sooner with the Griffon idea?

 

[wuzak]

I'm well aware of that and if you re-read my post, it says, "but Hawker were working on that installation on the Tornado in 1940", meaning a Centaurus installation. The point I'm trying to make is that Hawker had been pondering it for some time and that I'd like to see confirmation that the BMW 801 installation in the Fw 190 had an impact on the Tempest and Fury, if it exists. I'm sure it would be interesting data.

I didn't say that the Tempest's installation was inspired by or copied from the Fw 190.

What I said was that the Tornado's installation, nor any other British radial installation, was as advanced at the time (~1940-1942).

 

[nuuumannn]

What I said was that the Tornado's installation, nor any other British radial installation, was as advanced at the time (~1940-1942).

I'll give you that. The Bristol installations stuck with the exhaust collector ring for too long; it added weight and drag. I'll also agree with your comment about the Herc powered Spitfire; "it just isn't right!"

 

[wuzak]

I'll give you that. The Bristol installations stuck with the exhaust collector ring for too long; it added weight and drag. I'll also agree with your comment about the Herc powered Spitfire; "it just isn't right!"

I also don't think a Hercules powered Spitfire would be any great shakes either.

Also, by 1940 Supermarines were working on the Griffon Spitfire. A Hercules version would distract from that work, as well as the 2 stage Merlin versions.

 

[nuuumannn]

by 1940 Supermarines were working on the Griffon Spitfire. A Hercules version would distract from that work, as well as the 2 stage Merlin versions.

That's right. Read my post above about that. Perhaps in this what if scenario, Supermarine instead of Fairey could go to RR regarding a new engine and kick start the Griffon?

 

[wuzak]

That's right. Read my post above about that. Perhaps in this what if scenario, Supermarine instead of Fairey could go to RR regarding a new engine and kick start the Griffon?

Not sure that Fairey had anything to do with getting the Griffon started.

The question was asked, not long after the Griffon was started, if it could be fitted to the Spitfire. This was before the war.

Fairey was asked to help with or develop the Seafire, also before the war, but they wanted to do their own thing.

 

[tomo pauk]

I also don't think a Hercules powered Spitfire would be any great shakes either.

In case the Hercules Spitfire can climb with Fw-190 and Bf-109F-4/G-2 (and Zero?), it is offering something valuable. At under 7000 lbs loaded (2x 20mm, 4x .303s)and 150 HP extra with Hercules VI, it would be in advantage vs. the 8300+ lbs heavy Fw-190A-1 (2x MG FF, 4 LMGs).

Also, by 1940 Supermarines were working on the Griffon Spitfire. A Hercules version would distract from that work, as well as the 2 stage Merlin versions.

Unlike the Griffon, the Hercules is in production - once testing is done, there are engines around to install them. Vickers can allocate their engineers and technicians to bulk up the Supermarine's design staff. Plus, the Supermarine cancelled out the work on their heavy bomber once the prototype is destroyed during bombing - meaning there is more design staff to work on the Spit, that has the major aerodynamics structural long solved. The 2-engined heavy fighter is also cancelled.
Trial installation tests can be done during the Autumn and Winter, and small scale production to be undertaken from summer of 1941. Large scale production from Winter of 1941/42.
Hawker was working on 3 different-enough engines for their Typhoon/Tornado in about the same time.

 

[wuzak]

In case the Hercules Spitfire can climb with Fw-190 and Bf-109F-4/G-2 (and Zero?), it is offering something valuable. At under 7000 lbs loaded (2x 20mm, 4x .303s)and 150 HP extra with Hercules VI, it would be in advantage vs. the 8300+ lbs heavy Fw-190A-1 (2x MG FF, 4 LMGs).

Maybe. I'm not convinced.

Unlike the Griffon, the Hercules is in production - once testing is done, there are engines around to install them. Vickers can allocate their engineers and technicians to bulk up the Supermarine's design staff. Plus, the Supermarine cancelled out the work on their heavy bomber once the prototype is destroyed during bombing - meaning there is more design staff to work on the Spit, that has the major aerodynamics structural long solved. The 2-engined heavy fighter is also cancelled.

Supermarines stopped working on the 324/327 in 1938, having never received an order to proceed. So that wasn't an issue.

It is telling that the Air Ministry chose the "interim" Mk V over the more advanced Mk III. The Mk III was refined aerodynamically and would have (probably) been a match for the Fw 190A and Bf 109F.

A Hercules version, like the Griffon version, would have required significant strengthening of the fuselage. That adds weight. As does the need, identified earlier, to install counterweights in the tail to correct the CoG.

Hawker was working on 3 different-enough engines for their Typhoon/Tornado in about the same time.

The Centaurus was somewhat closer in size (frontal area) to the Vulture and Sabre than the Hercules was to the Merlin.

 

[Shortround6]

This seems like another one of those ideas/projects that requires working on a version of plane that will NOT be very good in service for 1 to 2 years so you can be ready with a tooled up production line when the version of the engine you really want to use shows up.
It also requires a fair amount of jiggery-pokery to get it to work.

AS for availability of Hercules engines, details seem to be a bit sketchy but it took until Dec of 1941 to get the first 200 Short Stirlings.
The first Wellington Prototype with Hercules engines flew May 19th 1939 but the first production version didn't fly until the Jan of 1941 with the Hercules XI engine.

Photo of Halifax engine installation

Photo of the Zero

http://www.enginehistory.org/G&jJBrossett/RAFCosford/Nakajima Sakae 21 display.JPG

can't get it to transfer over.

It is not question of unbolting the Merlin and it's radiators and bolting on a Hercules "power egg" and bashing some sheet metal to fill the gaps. The Hercules has a higher carburetor than the Sakae and some other radial engines. It often used a remote drive to the accessories. Good for servicing the accessorizes, not so good for a short engine installation. The exhaust system is going to offer a lot less exhaust thrust than the Merlin. The cowl is not exactly low drag.
Everything can be 'fixed' with enough time and effort but the longer it takes the less need for it.
The Early Hercules doesn't offer anything the Melrin doesn't at the time and even a Hercules VI giving 1545hp at 15,500ft (Lumsden) is fighting higher weight and much higher drag than the Merlin.

 

[Aozora]

It's just not right.....

A drawing from a guy named Mossie

Supermarine Spitfire and Seafire

So, Mr Blackadder - aka Mossie - you decided that a Spitfire powered by a Hercules would be an interesting idea?

Errr...errr...yup!

And having thought up this idea, you proceeded to photoshop it, and put it out on the net - for EVERBODY to see!?

Errrr...weeell...yup!

I put it to you, Mr Blackadder, you have just admitted responsibility for what is, in fact, AN ABOMINATION OF BEELZEBUB!!!

Not sure that Fairey had anything to do with getting the Griffon started.

The question was asked, not long after the Griffon was started, if it could be fitted to the Spitfire. This was before the war.

Fairey was asked to help with or develop the Seafire, also before the war, but they wanted to do their own thing.

The Griffon was designed in response to RN requirements. According to Morgan and Shacklady, Supermarine issued a specification (No. 466) for a Griffon powered Spitfire on 4 December 1939, and subsequently issued a revised specification No. 468, on 27 Feb 1940:

Flight articles from 1944 and '45

View attachment Rolls-Royce Griffon II VI.pdf
View attachment Spitfire XII 1944.pdf
View attachment Rolls-Royce Griffon 65 1945.pdf

 

[wuzak]

Let's look at the prop diameters again.

Mk V and Mk IX had prop diameter of 10'9".

Mk XII and MK XIV had a prop diameter of 10'5". The difference to the Merlin types is due to the lower thrust line.

The Hercules is ~10" taller than the Griffon. So we can expect a reduction of thrust centreline of ~5". That would mean a prop of ~9'7". That is a reduction of area of 21% over the V/IX and 15% over the XII/XIV.

The shorter engine may give some extra clearance, so if we assume a diameter of 10' that is still a loss of 13% and 8% respectively.

As regards to adding blades, the XIV got 5 blades in 1943. A 5 blade prop didn't exist in 1941 - it would have to be built.

Also, due to the smaller diameter the XIV spun its prop faster. The Hercules VI would need new reduction gearing to do that.

Also, ~1/5-1/4 of the prop will be blocked by the engine behind. The frontal area of the Bristol being roughly twice that of the Griffon.

 

[nuuumannn]

Not sure that Fairey had anything to do with getting the Griffon started.

I think I should have written FAA rather than Fairey, but Fairey did have something to do with kickstarting the Griffon. The Navy approached RR regarding a more powerful 'Merlin Type' engine, as stated in the text above in Morgan and Shacklady's book provided by Aozora, and subsequently released N.8/39 and N.9/39. To the former spec, Fairey offered the Griffon as a powerplant option (one of four engine types it specified) and it was selected for N.8/39. The spec was was re-written as N.5/40 and the Fairey design was selected for production off the drawing board, which became the Firefly I (first flying 22 December 1941) and indeed, the Firefly introduced the Griffon into service.

 

[tomo pauk]

By the end of 1940, there was plenty of orders from the American manufacturers. What orders should be kept, what ones altered, what can we be without?
Merlin (even the single stage) Mustang is a given

 

[gjs238]

And putting aside national pride, which British designs would be better shelved and foreign designs utilized?

 

[gjs238]

Order P-38 Lightnings (Model 322B) with counter-rotating engines and turbochargers.

 

[Shortround6]

P-38s with turbos won't show up in useful numbers until Nov/Dec of 1941 at which point the US grab the majority of the ones on order (this sort of happened historically, many of the P-38s originally ordered by the British weren't actually canceled, the orders were taken over by the US and the planes completed as several different models. However the British orders allowed Lockheed to hire workers, order machinery, material and parts. Like landing gear, Brakes, instruments, etc.).

BTW, By July of 1941, the RAF recognized that there probably would be a need for high altitude capabilities, and the original contract was amended to provide for the delivery of 143 Lightning Is with the originally-specified V-1710-15 un-turbosupercharged engines, with the remaining 524 aircraft to be delivered as Lightning IIs. First Lighting I does arrive in England until March of 1942.