A 12-gun fighter with 2 RR Kestrel engines for the RAF?

[don4331]

Trying to fit over 4000lbs of power plant weight into an 8300lb tare weight airplane (with Peregrines and DH variable pitch propellers) is the trick.

You seem to be implying that the Peregrines/DH Variable pitch propeller were no where close to 2,000lbs each

Morgan and Shacklady have the breakdown for the "power plant" in the Spitfire prototype as 2,000lbs with 1,225lb for bare Merlin F - close enough to the 1,230 lbs for Merlin II, RRHT cutaways, that I have been using.
The equivalent numbers for a Peregrine are 1,140lb for bare engine, and just over 1,800lbs for entire power plant. But Whirlwind doesn't use wooden propeller. The DH variable pitch propeller adds about 140lbs making the Whirlwind power plant about 1,940lbs each or about 3,880lbs for the pair.

But in my design. I want variable pitch propellers on the Merlins, so would be looking at adding about 200lbs to the Spitfire power plant weight. So, 2,200lbs total or about 260lbs/side more for the now 8,850lb empty fighter. And we know exactly how a Whirlwind flies with a 250lb bomb on each wind from increased takeoff run to stall speed (both u/c & flaps up and down) to landing speed. And that is close enough to the delta to Merlins for girl I go with. The only thing we don't know is how it functions at higher speed at altitude.

For the Kestrel Whirlwind with 12 gun nose
The 12 gun nose is about 100lbs lighter with 350rpg (which is why the mock up had 500rpg; note: Wiki is wrong for HS.404, 60 round drum weighs 22lbs empty/54lbs loaded. I'll fix it at some point referencing the US TM9-27)
The Kestrel XVIs are 140lbs lighter, the power plant with wooden propeller would be slightly over 500lbs lighter than historic each.

So, as our Kestrel Whirlwind is a 7,000lb empty airplane, changing from Fowler to split flaps will allow take off and landing distances in same general range as historic plane (Fowler flaps being 20% better than split per Theory of wing sections)*

Supermarine was truly fortunate to have the plane that RJ Mitchell designed and Joe Smith developed. But unfortunately, much of the team that was put together for the Spitfire dispersed after his death. Had he lived, I suspect he would have designed successor (like Sydney Camm followed up the Hurricane with Typhoon/Tornado, Tempest, Fury, etc) and Spitfire would only be a small pre/early war footnote.

For Westland, Petter still lives. And he can follow up a successful Kestrel XVI Whirlwind, with a slightly portly Peregrine Whirlwind (think Bf.109F to Me.109K) then design the follow on Merlin power heavy twin (with 25% more wing area and 4 - 20mm/3 - 0.303") using reputation gained from the initial successful plane.

*Yes, you can further improve Fowler flaps but making them multi element, and adding leading edge slat and get some truly impressive CL's but we are building a fighter in mid-30s here.

 

[Shortround6]

Morgan and Shacklady have the breakdown for the "power plant" in the Spitfire prototype as 2,000lbs with 1,225lb for bare Merlin F - close enough to the 1,230 lbs for Merlin II, RRHT cutaways, that I have been using.
The equivalent numbers for a Peregrine are 1,140lb for bare engine, and just over 1,800lbs for entire power plant. But Whirlwind doesn't use wooden propeller. The DH variable pitch propeller adds about 140lbs making the Whirlwind power plant about 1,940lbs each or about 3,880lbs for the pair.

Alfred Price has the power plant as 2035lb with the wooden airscrew.
35lbs is no big deal but some of the weights can wind up in different categories.

Like on the Spitfire prototype the 86lbs of engine cowling and 58lbs of engine mounting are over in structure weight with the wings, fuselage and landing gear, etc.

Under powerplant are listed as;
The "cooling fluid" is listed as 142lbs while the radiator is listed as 98lbs and the cooling system is 56lbs.
Petrol tanks are listed as 57lbs and oil tanks are 47lbs.

There is a bit of room for shifting things back and forth, but, you are not going to cool an 1030hp engine (let alone anything bigger) with the radiators and coolant capacity of a 885hp engine. You can fit a better radiator design, those 3 round radiators are not very space efficient but you are going to need more cooling tubes and more liquid. Likewise you are going to need bigger oil coolers.
Long flat fuel tanks (wing tanks) are heavier than short fat tanks (fuselage tanks) and especially so when you fit self sealing or protection.
The Whirlwind carried 67 Imp gallons per engine.

This is a lot of the "stuff" that is ignored when we discuss engine swaps in these "what if" pages.

Another thing that is glossed over is what "field performance" was expected.
The Whirlwind was officially disliked because of it's high take-off and landing speed, although it would up flying out of fields during the war that the prewar critics said were too short. I don't know if the extend the fields any or if they cut down trees or building to make extra space.
The Whirlwind was initially allowed to used 4lbs of higher pressure in the tires (and possibly create ruts in grass fields) more than any other aircraft of any type was allowed to use at the time (1939?).
When bullets started flying a lot of these restrictions went away but saying you can stuff a pair of Merlins into an airframe the size of the Whirlwind takes a lot of wishful thinking.

One reason the Hurricane and Spitfire were as adaptable as they were was that they had been built a bit oversize to get around these "field performance" requirements.
The large wings meant low landing speeds and take off speeds with crappy propellers left room for improvement with large increases in weight.

If the aircraft designers of 1936-39 had been told they could use tires that used 15-20% higher air pressure and could use 20-30% (or longer) runways or other changes in infrastructure a lot of planes might have wound up looking a lot different.

 

[stona]

My point is that the Whirlwind was an excellent airframe. When it turned out that the Peregrine engine would not be developed, and that the Merlins did not fit, the aircraft was declared obsolete. By late 1942, a twin-Kestrel powered fighter has more frontal area and less power than a Spitfire_IX. Which do we go with?

That is not at all what led to the demise of the Whirlwind.

When the first production Peregrine was delivered in February 1940 the decision had already been made to cease production after 290 units. To all intents, the Whirlwind was doomed from that point on, and was limited to a production run of just 114 aircraft.

As Robert Bowater wrote in '263 and 137 Squadrons: The Whirlwind Years'.

'Had the aircraft been ordered off the drawing board, delivered on time, and had the engine not been cancelled, the RAF would have had several squadrons of Whirlwinds during the Battle of Britain...'

But none of that happened, so it didn't.

 

[Spindash64]

Yeah, I admit to having a fondness for the Whirlwind and thinking it's a bit underappreciated among the 15 people who DO know about it, but they made the right call axing it: the Peregrine was a dead end, and even if it could be upgraded to Merlins, that would be two engines to build one plane, at a time that they needed every plane in the air they could get, and with the Merlin supply being a major limiting factor. And by the time this was a lesser concern, the upgraded Spitfires had already proven themselves better choices as interceptors with more far development room, and both the Beaufighter and the eventual Mosquito were far more versatile twin engine aircraft with equal or superior firepower

It was the same issue as the He-100, minus the "sneeze on it and everything starts leaking" problem: there was simply no room to add improvements, and this was a major problem in WWII, when technologies were developing at a breakneck pace and making engine variants (ie, Merlin III vs Merlin XX) obselete in a year at best, not to mention the many changes to armament, payload, and avionics