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Spitfire 21 possible?


Wingco57
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Hi chaps,

Been thinking about a future pet project of mine, the powerful Spitfire 21. There are no kits other than the Matchbox/Revell 22/24. As the real Spit used bits and pieces from earlier marks, I plan to do this in our scale too. I hope to combine the PCM Spitfire XIV fuselage with the 22/24 wings. Question is, can the wings

Be grafted on the fuselage? Calling Edgar, what tailplane was used?

Any info is very much appreciated.

Cees

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Mk 21 (type 356)[edit]

By early 1942, it was evident that Spitfires powered by the new two-stage supercharged Griffon 61 engine would need a much stronger airframe and wings. The proposed new design was designated the Mk 21. At first the Mk 21 displayed poor flight qualities that damaged the otherwise excellent Spitfire reputation.

The wings were completely redesigned with a new structure and using thicker-gauge light alloy skinning. The new wing was torsionally 47% stiffer, allowing an increased theoretical aileron reversal speed of 825 mph (1,328 km/h). The ailerons were 5% larger, and were no longer of the Frise balanced type, instead being attached by continuous piano-hinges. They were extended by eight inches, meaning that with a straighter trailing edge, the wings were not the same elliptical shape as in previous Spitfires.[42] The Mk 21 armament was standardised as four 20mm Hispano II cannon with 150 rpg and no machine guns.

The Griffon engine drove an 11 ft (3.35 m) diameter five-bladed propeller, some 7 inches (17.8 cm) larger than that fitted to the Mk XIV. To ensure sufficient ground clearance for the new propeller, the undercarriage legs were lengthened by 4.5". The undercarriage legs also had a 7.75 inch (19.7 cm) wider track to help improve ground handling. The designers then devised a system of levers to shorten the undercarriage legs by about eight inches as they retracted, because the longer legs did not have enough space in which to retract. These same levers extended the legs as they came down. The larger diameter four spoke mainwheels were strengthened to cope with the greater weights; post-war these were replaced by wider, reinforced three spoke wheels to allow Spitfires to operate from hard concrete or asphalt runways. When retracted the wheels were now fully enclosed by triangular doors which were hinged to the outer edge of the wheelwells.[42]

In other respects, the first production Mk 21s used the same basic airframe as the Mk XIV. The first true Mk 21 prototype, PP139 first flew in July 1943, with the first production aircraft LA187 flying on 15 March 1944. However the modifications over the Mk XIV made the Mk 21 sensitive to trim changes. LA201's poor flight control qualities, during trials in late 1944 and early 1945, led to a damning report from the Air Fighting Development Unit: "...it must be emphasised that although the Spitfire 21 is not a dangerous aircraft to fly, pilots must be warned...in its present state it is not likely to prove a satisfactory fighter. No further attempts should be made to perpetuate the Spitfire family."[43]

Supermarine were seriously concerned because Castle Bromwich had been converted to produce Mk 21s, and more were coming off the production lines daily. Jeffrey Quill commented that "The AFDU were quite right to criticise the handling of the Mark 21...Where they went terribly wrong was to recommend that all further development of the Spitfire family should cease. They were quite unqualified to make such a judgement and later events would prove them totally wrong."[43]

 
Spi2191a.jpg
 
 
Spitfire F Mk 21 of 91 Squadron.

After intensive test flying the most serious problems were solved by changing the gearing to the trim tabs and other subtle control modifications, such that the Mk 21 was cleared for instrument flying and low level flight during trials in March 1945. An AFDU report on LA215 issued that month noted that the Spitfire 21 was now much easier to fly;

General Handling
The modifications carried out to this aircraft have resulted in an improvement of the general handling characteristics at all heights...
Conclusions
The critical trimming characteristics reported on the production Spitfire 21 have been largely eliminated by the modifications carried out to this aircraft. Its handling qualities have benefitted to a corresponding extent and it is now considered suitable both for instrument flying and low flying. It is considered that the modifications to the Spitfire 21 make it a satisfactory combat aircraft for the average pilot.
[
44
]

Spitfire 21s finally became operational on 91 Squadron in January 1945. 91 Squadron had little opportunity to engage the enemy before the war ended, but scored a rare success on 26 April 1945, when two Spitfire Mk 21s shot up and claimed to have sunk a German midget submarine which they caught on the surface. With the end of the war most orders for the Mk 21 were cancelled and only 120 were completed.[45] In 1946 40 Spitfire 21s were delivered to Shoeburyness; once there their leading edges were removed and destroyed in "lethality" tests. Some aircraft had less than five hours flying time.[46]

Mk 22 (type 356)[edit]

The Mk 22 was identical to the Mk 21 in all respects except for the cut-back rear fuselage, with the tear-drop canopy, and a more powerful 24 volt electrical system in place of the 12 volt system of all earlier Spitfires. Most of the Mk 22s were built with enlarged tail surfaces, similar to those of the Supermarine Spiteful. A total of 287 Mk 22s were built: 260 at Castle Bromwich and 27 by Supermarine at South Marston.[47]

The Mk 22 was used by only one regular RAF unit, 73 Squadron[48] based on Malta. However 12 squadrons of the Royal Auxiliary Air Force used the variant and continued to do so until March 1951. The Mk 22 was also used at Flying refresher schools. In May 1955 the remaining F.22s were declared obsolete for all RAF purposes and many were sold back to Vickers-Armstrongs for refurbishment and were then sold to the Southern Rhodesian, Egyptian and Syrian Air Forces.[48][49]

 

 

 Well, I'm not Edgar, but if the above from Wikipedia is correct, I'd conclude that the Mk.21 used the original horizontal tailplane from the earlier marks with the enlarged mass balances.

 

 

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Thanks Erik,

That helps, now I wonder if the wings from one kit fits the fuselage of the other. The LHS didn't have neither

Of them unfortunately, but planning these projects is always fun ( although there are too many to choose from)

Cees

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The super-critical report on the 21, February 1st 1944, was followed, 10th March, by a second, which passed the aircraft for service use. The balancing action of the rudder tab was eliminated, the gearing in the elevator trim was reduced, and a metal elevator (note this, you modellers) with rounded-off horns was fitted. Metal-covered elevators were able to be fitted by units from October 1945. 

Apart from that, the back end was standard XIV (unless you want to do a contra-prop 21, which is a different matter entirely.)

If you start off with the PCM XIV, you start with a double advantage; as well as the ready-made fuselage, you have a pair of "proper" XIV radiators (those of the Matchbox kit are a scale 6"(ish) short), BUT this is where the fun now begins (been there, done that, but got it wrong.)

Somehow, I think that Matchbox got Spitfire 22/24 drawings mixed up with those of a Seafire 47, or went to Blackpool to measure a derelict 47 sitting there. Either way, though the wings are usable, the 22/24's root fairings are badly wrong, being a scale 4"-6" (can't remember exactly) too wide at the wing trailing edges. This, when you fit the wing up to the fuselage, gives you a passable fit back as far as the mainspar, but an increasing, triangular gap between wing and root, the further back you get. 

I made the mistake of grafting the 22/24's roots onto the Hasegawa fuselage (all we had back then,) when I should have extended the wings' upper surfaces inwards with a triangular piece of plastic.

If Matchbox did use a 47, the too-short radiators are explained by the 47's wider flaps, which didn't drop as far as Spitfire flaps, but still needed truncated radiators, and the too-wide wingroot fairings appear to have been necessary on the Seafires 46 & 47, to spread the angles of the RATO rockets, so that the efflux missed the wider tailplane. 

Sorry, I seem to have gone on a bit.

Edgar

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Hi Mike,

Thanks for the link, had not seen that one, so using the PCM fuselage is possible. Although the one in the

Link used the Mk IX, but I am a lazy modeller.

Cees

Cees,

  You miss read the article. The link I provided is my build. Here's what I used  PCM Mk IXC fuselage, cockpit and tailplanes with Revell Mk22/24 wings and landing gear and RB Mk14 Griffon nose, prop, intake, and vertical stabilizer and rudder. 

    Mike Horina

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Hi Mike,

 

Good to see you here. That's a great buid. How did you tackle the fit between the PXM fuselage and the ancient Matchbox (Revell) wings?

You had a more difficult job because the XIV wasn't available. Any in progress pic perhaps you can post?

Cheers

Cees

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Hi Mike,

 

Good to see you here. That's a great buid. How did you tackle the fit between the PXM fuselage and the ancient Matchbox (Revell) wings?

You had a more difficult job because the XIV wasn't available. Any in progress pic perhaps you can post?

Cheers

Cees

Hi Cees,

  Thanks for the welcome. Sorry I'm not a camera person, in fact the photos I posted were taken at a club meeting to be put on the club's site from a club contest. As to the mating of the wing to the fuselage I used white Milliput (spelling) because its so easy to even out with water before it cures fully. By the way I think PCM did a nice job on the Griffon bulges. Any thoughts on those? Vacform or cast to use on a Hase MkV to get to a MkXII?

    Mike Horina

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Mike,

I agree about the PCM bulges being very well rendered. I have the Iconicair nose cowl set to replace the Matchbox

Misshapen nose, but probably won't need it. if I can get a XIV that is.

Doesn't grey matter figures make a conversion set for a Mk XII, a real looker. Then again I like all Giffon Spits.

Cees

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  • 3 weeks later...
  • 1 month later...
  • 1 month later...

Calling Mike Horina,

Could you describe how you managed to marry the Matchbox/Revell wings to the PCM fuselage?

There is little area to give strenght and there is a large gap between the wings and fillets.

Cees

Cees,

  Sorry it took this long to get back. Not magic just some plastic pieces ,super glue and Milliput. One side at a time. If I remember correctly one side is worse than the other. Work slow and allow things to dry and cure otherwise you stress and develop cracks. When /if cracks develop I used more Milliput to fill and correct. I know not much help you just have to go slow.

    Mike Horina

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