Spitfire Mk.14/18 rudders

[John Aero]

There is some confusion with the rudders fitted to the Mk.14 and 18 Spitfires. I find that the Morgan/Shacklady "bible" is often less than helpful and sometimes irritating. As Edgar mentioned in a previous post (on contra props) the 14/18 fin/rudders areas are given as the same. This is not so and this "red herring"is the cause of some confusion. The 14 fin went through a considerable change in area and the only real reference given in the"bible" is a sketch showing an interim straight leading edge modification and it omits to mention that the height at the rudder post was increased by almost 3". The standard rudder post height of all the earlier Spits was 58".

The extra 2.75" fin height increase was achieved by fitting a "block false tip". The Mk.18 had a broader chord rudder and a deeper horn balance. This rudder was also fitted to other Mk.14 based airframes,( by the simple expedient of "removing the block") such as FR14e, 19, and the Mk.21 when fitted with a contra prop.

This illustration I have cobbled up might help. It is the tail of an FR.14e and I have superimposed the outlines of the Mk.14 and Mk.18 rudders on to it, the white area is the "block" . The blue outline is the 14 and the red 18.

The join line (lower edge of the block) seldom shows up on photos and is often shown as a panel line in drawings but too low down, a mistake repeated on my own Mk.21 conversion as this was made originally to the Cook drawings.

John

[AnonymousAA72]

There is some confusion with the rudders fitted to the Mk.14 and 18 Spitfires. I find that the Morgan/Shacklady "bible" is often less than helpful and sometimes irritating. As Edgar mentioned in a previous post (on contra props) the 14/18 fin/rudders areas are given as the same. This is not so and this "red herring"is the cause of some confusion. The 14 fin went through a considerable change in area and the only real reference given in the"bible" is a sketch showing an interim straight leading edge modification and it omits to mention that the height at the rudder post was increased by almost 3". The standard rudder post height of all the earlier Spits was 58".

The extra 2.75" fin height increase was achieved by fitting a "block false tip". The Mk.18 had a broader chord rudder and a deeper horn balance. This rudder was also fitted to other Mk.14 based airframes,( by the simple expedient of "removing the block") such as FR14e, 19, and the Mk.21 when fitted with a contra prop.

This illustration I have cobbled up might help. It is the tail of an FR.14e and I have superimposed the outlines of the Mk.14 and Mk.18 rudders on to it, the white area is the "block" . The blue outline is the 14 and the red 18.

The join line (lower edge of the block) seldom shows up on photos and is often shown as a panel line in drawings but too low down, a mistake repeated on my own Mk.21 conversion as this was made originally to the Cook drawings.

John

Thanks John, It all makes perfect sense now - though I don't think I'll be changing my Mk21 again!!!!!

[John Aero]

Hi Bill

No need to change anything except the one little panel line for a 14.19,21 (to be 100%). It's the shape of the 18 and FR14e rudders which is always drawn wrong. Tommy Atkins (Metal kits) did explain to me once (he flew 21's with No 1 Sqn), why the contras were fitted with the larger rudder . Apparently propeller gyroscopic force is eliminated but torque is not and on take-off at low air speeds a dropped wing is recovered with the rudder, as coarse use of the aileron to lift the wing introduces induced drag compounding the problem.

Here is my old 21 from 1 Sqn days I fitted the four slot wheels as the BB flight stole the 3 slots for their 19's. Please note that the 14 rudder tip in my original sketch is slightly too high. Arthur Bentley and I are close but not totally in agreement over some shape aspects of the 14/18 rudder differences but the drawings I have of Arthurs are preliminaries.

John

Edited July 2, 2007 by John Aero

[Edgar]

I haven't, yet, been able to get to this one, at the RAF Museum, so, until I see the drawings, discussion is a bit superfluous. However, the broad-chord rudder was introduced, as mod 1672, from 15-10-46, 16 months after the first XVIII flew, so Morgan/Shacklady's book might yet be correct, for the first off the line.

Mod 1674, the larger rudder horn, designed, originally, for the contra-prop 21 & 22, wasn't proposed until 14-8-46.

The split rudder trimmer, which was mod 1659, was designed for the contra-prop 21, too, and wasn't proposed until 10-7-45.

I have a contact, in the library, at the Museum, who will cross-reference drawing numbers to mods, then I can go to check them. Vickers's system refers the drawings to the mods, but not the other way round, so I have to allow her several days to make the connection(s.) Last time, I found out some details of the Sutton, "Q" and "Z" harnesses, and some of the seat alterations (but there are more,)and my next visit might sort out the IX cowling "hump," since I've found a mod, which specifically mentions changing the shape.

I'm trying to make one trip, each month, mainly so that I don't wear out my welcome(!!!)

Edgar

Edited July 2, 2007 by Edgar

[John Aero]

I haven't, yet, been able to get to this one, at the RAF Museum, so, until I see the drawings, discussion is a bit superfluous. However, the broad-chord rudder was introduced, as mod 1672, from 15-10-46, 16 months after the first XVIII flew, so Morgan/Shacklady's book might yet be correct, for the first off the line.

Mod 1674, the larger rudder horn, designed, originally, for the contra-prop 21 & 22, wasn't proposed until 14-8-46.

The split rudder trimmer, which was mod 1659, was designed for the contra-prop 21, too, and wasn't proposed until 10-7-45.

I have a contact, in the library, at the Museum, who will cross-reference drawing numbers to mods, then I can go to check them. Vickers system refers the drawings to the mods, but not the other way round, so I have to allow her several days to make the connection(s.) Last time, I found out some details of the Sutton, "Q" and "Z" harnesses, and some of the seat alterations (but there are more,)and my next visit might sort out the IX cowling "hump," since I've found a mod, which specifically mentions changing the shape.

I'm trying to make one trip, each month, mainly so that I don't wear out my welcome(!!!)

Edgar

Hi Edgar

Interesting as always but was mod 1672 introduced as a mod specific to the 21 (contra) in which the mod "used" the (possibly) exsisting 18 rudder, or was this an introduction of the broad chord,big horn rudder to the Spit in general?. I'd suspect the former, remember all 14 airframes would have the "false" extension to the fin tip from build.

Regards

John

[Edgar]

No, mod 1672 was, specifically, for the 14 & 18 (it's written, that way, in the book, without Roman numerals.) The 21 doesn't get a mention, at all.

1659 was for the 21, only, and 1674 was for the 21 & 22.

Further on, in 1947, mod 1702 introduced "Fit anti balance split tab and larger horn to rudder" This was for the 22, with the "Larger empennage" (mod 1613)

It looks, from that, as though even the 22's rudder changed, during its life.

Like I said, I really need to see the drawings.

Edgar

[John Aero]

Edgar

It would appear from these discussions that the "big rudder" originated with the fitting of the contra prop to the Mk.21 (and not with the 18), and there is a photo of LA219 dated September 1945 fitted with this wide chord rudder. It's becoming obvious to me that with the larger chord requirement for the contra prop a/c came the need for a larger (both weight and aerodynamically) counter balance horn and this was easily acheived by reducing the fin height back to the original rudder post height.

Over

John

[Edgar]

I have a suspicion that this will only be (sort-of) resolved, by measuring the rudder-post, on 1 Squadron's 21 (access denied, for me, in the present climate, I presume.) I've spoken to Peter Cooke, who, years ago, clambered all over XIVs, XVIIIs, and XIXs, at Blackbushe, and he doesn't remember any additions to the fin-tops, but he's going to loan me all of his slides (two boxes of them,) so that I can check for myself. These airframes had all been returned to this country (from India, he thinks,) so should have been untouched.

Judging from the dates, I think that the first idea was, simply, the split rudder trimmer, for the contra-prop 21, leaving the original "narrow" rudder; it's mod 1659, and was proposed in July, 1945.

Probably due to the loss of directional control, on the cut-down fuselages of the XIV & XVIII, the large chord rudder was introduced in October 1946; that's mod 1672.

Maybe, due to the trim-tab not doing enough, someone proposed that the larger rudder, with a larger horn, (due to the blanking effect of the high-backed fuselage, I suppose) should be tried.

What we have to remember is that "proposed" doesn't equal "introduced," and it can be difficult to work out when certain actions occurred.

There's an awful lot of "suppose," "guess," and "maybe," in that lot, and, without looking at the drawings, I'm stymied; if they don't include measurements...........! I'll get a request off, to my "Girl in the Library," and see what she can come up with.

Edgar

Edited July 2, 2007 by Edgar

[John Aero]

I have a suspicion that this will only be (sort-of) resolved, by measuring the rudder-post, on 1 Squadron's 21 (access denied, for me, in the present climate, I presume.) I've spoken to Peter Cooke, who, years ago, clambered all over XIVs, XVIIIs, and XIXs, at Blackbushe, and he doesn't remember any additions to the fin-tops, but he's going to loan me all of his slides (two boxes of them,) so that I can check for myself. These airframes had all been returned to this country (from India, he thinks,) so should have been untouched.

Judging from the dates, I think that the first idea was, simply, the split rudder trimmer, for the contra-prop 21, leaving the original "narrow" rudder; it's mod 1659, and was proposed in July, 1945.

Probably due to the loss of directional control, on the cut-down fuselages of the XIV & XVIII, the large chord rudder was introduced in October 1946; that's mod 1672.

Maybe, due to the trim-tab not doing enough, someone proposed that the larger rudder, with a larger horn, (due to the blanking effect of the high-backed fuselage, I suppose) should be tried.

What we have to remember is that "proposed" doesn't equal "introduced," and it can be difficult to work out when certain actions occurred.

There's an awful lot of "suppose," "guess," and "maybe," in that lot, and, without looking at the drawings, I'm stymied; if they don't include measurements...........! I'll get a request off, to my "Girl in the Library," and see what she can come up with.

Edgar

Edgar

Whilst I accept that 1946 was probably the introduction date for the "big" rudder I still maintain that it was possible to retrofit it because the fins of Mk."14" type fuselages had been built up in the first place. The fin tip of the "normal 14" has a chord of 14.25" and the fin tip of the Mk.14e (big rudder) at Manchester which I measured is 16.25" chord. If one takes the line that the fin heights are the same on 14s and 18s then the fin leading edge of the 18 has been extended giving a much broader fin,which I feel is clearly not the case.

Cheers

John

[Edgar]

I suspect we're, apparently, arguing, when we both, actually, agree, on the main item; there was, definitely, at some stage, a deeper horn. Photographs, of Mk.21 LA215 (The Spitfire Story, page 469,) with, and without, contra-props, show a marked difference in the distance from the top of the fin, down to the top of the fin flash.

The irony is that Nexus never printed Peter Cooke's drawing of the starboard side of a XIX, only a truncated version of the port side. I have a copy of his 1/24th drawing, of the fuselage, and he has drawn a panel line, a short distance down from the top of the fin. Measuring it, to the base of the rudder post, and multiplying by 24, the distance comes out to 58", which is pretty close to the 59", which I measured on the Duxford 18. The panel line scales out to about 2.5" below the "normal" fin-top.

So far, though, I haven't found any photos, which, clearly, show that line; even photos, of natural metal XIVs, in Aircam no.8, don't appear to show it. Peter will be bringing his photos to our next club night, and I have to get to the drawings!

Edgar

Edited July 4, 2007 by Edgar

[John Aero]

I suspect we're, apparently, arguing, when we both, actually, agree, on the main item; there was, definitely, at some stage, a deeper horn. Photographs, of Mk.21 LA215 (The Spitfire Story, page 469,) with, and without, contra-props, show a marked difference in the distance from the top of the fin, down to the top of the fin flash.

The irony is that Nexus never printed Peter Cooke's drawing of the starboard side of a XIX, only a truncated version of the port side. I have a copy of his 1/24th drawing, of the fuselage, and he has drawn a panel line, a short distance down from the top of the fin. Measuring it, to the base of the rudder post, and multiplying by 24, the distance comes out to 58", which is pretty close to the 59", which I measured on the Duxford 18. The panel line scales out to about 2.5" below the "normal" fin-top.

So far, though, I haven't found any photos, which, clearly, show that line; even photos, of natural metal XIVs, in Aircam no.8, don't appear to show it. Peter will be bringing his photos to our next club night, and I have to get to the drawings!

Edgar

Edgar

No arguement just logical investigation into a simple solution. )

Look very closely at the top pic of LA215 and just above the stencilling-there is the join line which by the way was normally flush filled, but on LA255 it had become loose which is why I noticed it. and memory tells me it was made from wood.

If you have a pic of the 14 that went to Canada for cold weather trials in it's later natural metal racing guise it can be seen also.

Cheers

John

[Edgar]

Sorry, John, I missed out a couple of words, in my answer. I should have said apparently "to others." I somehow doubt that we're going to fall out over a panel line (unless it's pre-shaded, of course.)

As well as the modifications, I might have to look at the original drawings, at least for the "normal" F.XIV, FR.XIV, and XVIII, perhaps even the XIX. I've just passed on a list of 11 mods, and I'm loath to load any more onto the girl, at least until I know how many drawings this little lot will add up to. I have included the 1659, 1672, and 1674 mods, so they might help.

Pssst! Anybody want to know about crowbars? headrests?

Edgar

[Dave Fleming]

Mentioned on the other thread, but I noticed it again recently that in 1947, 17 Squadrons mk 14s (i.e. original high backed aircraft - e.g. RN185) in BCAFO in Japan were fitted with the enlarged mk 18 style rudder, whilst 11 Squadrons FR14s (low backed - e.g. NH844) were fitted with the earlier F14 style. There are pics at Miho which show all 17 Squadrons aircraft with the original rudder in Spitfire At War 3, and another in the Lucas 'RAF Fighters Overseas' book that shows all the squadrons aircraft with the later style!!*

'RN' serialed aircraft operating in the SEAC zone in 1945/6 had the F14 style as well - both high backed (RN193) and low-backed (RN218). I've not yet found photos of an aircraft carrying both styles of rudder, but i'm sure they do! This does make you wonder about the wording of any retrofit notice!!

Certainly. the F18 style doesn't seem to start appearing on FR14s until into late 1947/1948 (The two FR14es supplied to 602 Squadron had it)

There is a photo in SaW3 showing mk 18s under assembly which is dated as late 1945.

Thanks for the drawing John, the part I always found hard to envisage was how much to add to the rear of an F14 rudder to make the later one!!

* The later style also appears to have been fitted to both high and low backed mk 14s supplied to Belgium

Edited July 4, 2007 by Dave Fleming

[John Aero]

Mentioned on the other thread, but I noticed it again recently that in 1947, 17 Squadrons mk 14s (i.e. original high backed aircraft - e.g. RN185) in BCAFO in Japan were fitted with the enlarged mk 18 style rudder, whilst 11 Squadrons FR14s (low backed - e.g. NH844) were fitted with the earlier F14 style. There are pics at Miho which show all 17 Squadrons aircraft with the original rudder in Spitfire At War 3, and another in the Lucas 'RAF Fighters Overseas' book that shows all the squadrons aircraft with the later style!!*

'RN' serialed aircraft operating in the SEAC zone in 1945/6 had the F14 style as well - both high backed (RN193) and low-backed (RN218). I've not yet found photos of an aircraft carrying both styles of rudder, but i'm sure they do! This does make you wonder about the wording of any retrofit notice!!

Certainly. the F18 style doesn't seem to start appearing on FR14s until into late 1947/1948 (The two FR14es supplied to 602 Squadron had it)

There is a photo in SaW3 showing mk 18s under assembly which is dated as late 1945.

Thanks for the drawing John, the part I always found hard to envisage was how much to add to the rear of an F14 rudder to make the later one!!

* The later style also appears to have been fitted to both high and low backed mk 14s supplied to Belgium

Thanks for the feedback Dave and Edgar. The panel line (really Join line) I refer to, was, as I pointed out previously usually filled and painted over, so it's invisible on most 14 variant pics but I am finding more and more where it can be diserned.

The normal rudder post (fin) height for the early Merlin Spits is 58" (ish) and so I suggest the rudder post height for a 14 has to be nearer 61" as the extension fin tip is about 2.75" deep. The chord for a "big rudder" on the lower edge of the trim tab is 33.2".

Cheers

John

[Edgar]

That matches (well, nearly enough) my measurements of the rebuilt 18, at Duxford. The rudder post is 59", the chord, at its widest point, is 33.5", and the horn, to the apex of the rudder, is 12.5" deep. This gives a total height, for the rudder, of 71.5" At the top of the rudder post, the horn, to the l/e of the rudder is 16" long, and the chord, of the rudder, from that point, is 18".

Edgar

[John Aero]

That matches (well, nearly enough) my measurements of the rebuilt 18, at Duxford. The rudder post is 59", the chord, at its widest point, is 33.5", and the horn, to the apex of the rudder, is 12.5" deep. This gives a total height, for the rudder, of 71.5" At the top of the rudder post, the horn, to the l/e of the rudder is 16" long, and the chord, of the rudder, from that point, is 18".

Edgar

We're getting there, so it won't be Crowbars at dawn.

Cheers

John

[Hurrinut]

Never mind all this about Spitfires John.

Wheres my 1/48 Rapide?

:whistling:

[Edgar]

We're getting there, so it won't be Crowbars at dawn.

Cheers

John

Dawn? What's that? (I'm retired, dontcha know?)

Just had a message, from the RAF Museum; the search is on, so we'll see, soon (I hope!)

Edgar

Edited July 5, 2007 by Edgar

[thx6667]

Always a pleasure just to sit back and watch some first rate research being done.

[AnonymousAA72]

Always a pleasure just to sit back and watch some first rate research being done.

Yep!!!

[Jon Kunac-Tabinor]

Just a note to say, thankyou for this info. Just what I needed!!

Jonners

[Miggers]

Thanks indeed gents.

I'm planning an FR.XVIII from a collection of 1/72nd scale bits(prolly based on an Airfix XIX)and I had a suspicion

about the rudder chords.

Mark

[wellsprop]

Ah blast it!

Finding this out means i now know that the az xiv's i made have the wrong rudder! Too little difference in 72 scale so I think I'm going ot have to let that one pass...

Ben.

[Edgar]

Thanks to Kew's filing system, I now think that I've found out what all this was about.

A Mk.IX, AB505, was fitted with a trial set of contraprops, and it was found that there was difficulty taxying, so a new, bigger, rudder had to be fitted.

It now looks as though the 2" blocks were initially fitted to the XIV, in anticipation of the arrival of contraprops, which would need a different rudder, but the blocks were deleted (by a modification,) when the idea of a contra-prop XIV was dropped, then resurrected with the planned arrival of the contra-prop 21.

Edgar

Edited April 8, 2013 by Edgar

[Spitfires Forever]

To put this discussion into a practical application towards a modeling dilemma which I have, would anyone know about the Airwaves Mk XVIII rudder in 1/48 and whether it would work on the Academy FR XIVe? I have the DACO retrofit resin kits, but those rudders may not be quite big enough for the FR version, but quite suitable for the Mk XIVc. Any thoughts before I commence surgery?

Cheers

P.S. I figure of I go through all the effort to build the kit Airfix will announce the release of their Mk XIV for next fall.