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Member postings for Colin Leighfield

Here is a list of all the postings Colin Leighfield has made in our forums. Click on a thread name to jump to the thread.

Thread: Colinís Spanish Fury
17/09/2019 23:41:52

After the various events of the last few weeks, not to add my son’s wedding on Friday, I have managed to get sufficiently up to date to start working on the Fury again. I have spent this evening cutting and fitting the fibre-glass aileron hinges. One or two problems to overcome but should be ok. I hope to make further progress tomorrow.

Thread: Thinking aloud about Spits...
15/09/2019 21:47:30

You could be right Erfolg!

15/09/2019 17:36:21

The reason for the intake on the P51 being outside the boundary layer was because it was found that early problems with buffeting etc. were resolved by moving the ventral intake outside of It, very noticeable on the P51D. It was the solution to the problem. It would probably have been the answer to the similar difficulties with the Hawker Tornado prototype, but Hawker solved it, also for the Typhoon, by moving the radiator etc under the nose, where the problem doesn’t arise behind the propeller. Almost certainly Kurt Tank had identified the issue as well.

15/09/2019 08:19:22

PatMc makes an interesting point. When Supermarine produced the type 371 Spiteful using an aerodynamic design developed by the National Physical Laboratory, the assumption was that the theoretical lower drag of the “laminar flow” wing section would enable it to be slightly thicker and also that wash-out wouldn’t be necessary in the interests of minimising drag by every means. When they flew the protype Spiteful NN660, which was actually a Spitfire XIV with the new wing, it was about 30 mph faster than the Spitfire in level flight with good high speed handling and roll rate, but at landing speeds demonstrated wing dropping and aileron snatching. Sadly NN660 was destroyed in a few weeks killing Frank Furlong, initially thought to have been caused by this tendency in a tight turn although later believed to be due to aileron binding through the rod controlled system. (The Spitfire wing used cables). The full prototype NN664 and the “production” planes used for testing from RB515 onwards were developed to resolve this problem and one of the changes was to reduce the sharpness of the wing section leading edge. However in so doing the level speed advantage was reduced to about 20 mph.

When the Seafang variant of the Spiteful was being evaluated by the Navy, one of the reasons for rejection was that in return for this comparatively small difference of about 4.5%, the landing speed was 30 mph faster. Consequently they chose the Seafire 47 instead and when the Sea Fury was sorted out, that became the main fleet fighter. The handling problems must have been reasonably resolved because otherwise the Attacker (originally Jet Spiteful) with the 371 wing would never have got into service, although that took so many years it was past its sell-by date by then. As mentioned in an earlier thread, Jeffrey Quill told Joe Smith that the Attacker would have been a “b****y sight better aeroplane with a Spitfire wing”. He was no doubt right and also it could have been in service much earlier.

All of this begs the question, why then was the Spiteful/Seafang faster than the equivalent Spitfire in level flight when it was proven to actually have a lower limiting Mach number of around 0.82, similar to the P51? Almost certainly the answer lies in the much lower drag of the cooling system, which was extensively tested with the wing in the NPL high speed wind tunnel. In other words, the same reason why the P51 was about 30 mph faster than the equivalent Spitfire in level flight, nothing to do with its “laminar flow” wing which was later found not to achieve laminar flow, but because of the low drag of the cooling system.

Another interesting event was the idea to improve the laminar flow characteristics of the Spitfire wing by raising the leading edge profile, this thickening the leading edge and moving the point of maximum thickness further back. Such a wing was built and tested and would have been used in a version called the Spitfire 23. However it was found in testing to make no worthwhile difference to performance and introduced some handling problems, so it was dropped and they focused on the 371 wing instead.

As Leccyflyer says, the thread is all about “thinking aloud about Spits”, So I hope this is of some interest in that vein.

Edited By Colin Leighfield on 15/09/2019 08:35:13

Edited By Colin Leighfield on 15/09/2019 08:35:39

Edited By Colin Leighfield on 15/09/2019 08:37:25

Edited By Colin Leighfield on 15/09/2019 08:38:48

14/09/2019 22:34:46

Well, the Mk1a doesn’t really look any different from a MkII or even a MkVa. It doesn’t really matter though does it? It would be a sad old world if we all saw things the same way.

14/09/2019 22:02:59

To say that any version of the Spitfire isn’t really a Spitfire is a bit odd, everyone of them was a Spitfire and the strain ran right through every version from first to last with absolute continuity. To me it is the most aesthetically attractive aeroplane ever built, built in so many different and progressively improved versions yet still thought of as “the Spitfire”! The photo is of the Seafire FR47, truly the last Spitfire and it looks absolutely stunning. All versions from start to finish have this rare quality that is so often captured in photographs.

Adding wash-out makes no difference whatsoever to the wing area or lifting capability. If a designer chooses an angle of incidence of 1.25 degrees it makes no difference if he does it with a wing having no wash-out and constant incidence from root to tip, or with a root incidence of +2 degrees and tip of -0.5. The average is still 1.25 degrees. The lifting ability will be identical. In theory it can increase drag slightly, but in practice the progressive wash-out from root to tip will have some co-incidence with the natural span-wise air flow that occurs across a wing and help to control it, with a corresponding effect on the drag-inducing tip vortex. There is no question at all that the Spitfire wing was proven to have remarkably low drag at high speed and a limiting Mach no. beyond that recorded for any piston engined aeroplane. The combination of shape, thin wing section and wash-out was better in this respect than any of the later “laminar-flow” wings that followed and were supposed to be superior.

Compared with the 109 and later 190, the Spitfire with 240 square feet of wing area against these both with only about 70% of that area achieved similar level speeds with less horse power. The 109E had 100 more hp than the Spitfire 1, the 190A had 200 more hp than the Spitfire IX. That is a very good measure of superior aerodynamics. To combine this with benign low speed handling and no tip-stall was remarkable, the flaps and undercarriage down stalling speed of some versions was only 58 mph. Additionally the high speed stall in a tight turn was at much higher speeds, a recent article in Aeroplane describes that in a sustained high speed turn the 109 would eventually flick out into the opposite direction while the Spitfire sustained the rate of turn without difficulty. Where the 109 and 190 had the advantage was more rapid initial acceleration in a dive because of their heavier wing loading, although if sustained for long enough the Spitfire would eventually wear down that advantage.

It wasn’t perfect by any means and fortunes varied as its opponents were also improved, but it was capable of continuous improvement beyond probably any other fighter ever built. We shouldn’t forget that from 1941 it was intended to be replaced by Hawker Typhoons and Tornados and Supermarine were expected then to build Beaufighters. A good job for us that when Hawker failed to come up with the goods that we had the Spitfire and it was so capable, otherwise we would have been in very serious trouble. 78e2031b-b5e9-4434-9ffe-b66d219d7f0c.jpeg

12/09/2019 23:23:33

There is a lot of mythology about the colour of K5054. We know exactly what colour it was originally. In his book “R.J. Mitchell - Schooldays to Spitfire” his son Gordon describes it. In fact he still possessed the aluminium ash-tray sprayed in the original Cerulean Blue colour that had been given to his father. After the original tests the plane was taken back into the workshops, the undercarriage leg fairings fitted and it was painted. There were issues with the quality of the filler and suitability of the paint, so that there were problems with cracking and flaking early on. As a result the airframe was stripped and re-painted within a few weeks of the first flight. The light grey paint that I understand was used then has been assumed by some to be the original colour, but it wasn’t. Later on the plane was re-painted again in standard RAF camouflage and late photos show that. The “planked” wing structure remained throughout its life until the sad accident that killed White, the pilot. A major part of the production engineering lead by Joe Smith to get the Spitfire into production included re-engineering the wing structure to increase stiffness, because originally it lacked torsional rigidity and aileron reversal occurred at too low an air speed. That is why the “planked” effect is only visible on K5054. 

Edited By Colin Leighfield on 12/09/2019 23:27:14

12/09/2019 20:49:21

image.jpegimg_2094.jpgI designed a 1/7 scale version of the prototype K5054 many years ago, I don’t know if I’ll ever finish it. The colour should be cerulean blue, slightly lighter than this. Later on the prototype was re-painted in a light grey after problems with cracking of the original colour.

The wing section is scale, NACA2200 series and the wash-out also scale at 2.5 degrees. Had the Dynam Spitfire IX forDynam Spitfire after re-paint. a while and that was a pussy-cat. The current Durafly Spitfire 24 is also a very good flyer and doesn’t tip stall. My Black Horse 72” Piper Cub would drop a wing though if I slowed it down too much!

Thread: Hobby King Piper L4 Grasshopper 1.4 metre, plug and fly.
11/09/2019 12:35:47

Thanks JD 8 and Chris. Good thinking, there’s nothing artificial about this weathering!

10/09/2019 21:44:01

An hour or so’s work and it’s ready to fly again. Connected a battery and everything worked, so seven weeks out in a bean field have done no serious damage except to the paint. Repairs were to re-attach an aileron and detached wing strut, fix the undercarriage with epoxy and bullet tape, which will look ok under a coat of matt olive green paint.

So my reliable flyer is back, I will keep it closer in from now on, particularly against a dark sky. 2d68dcec-bcea-4d6d-925a-af0d3fc442f3.jpeg

Thread: Hangar 9 Ultra Stik 10cc
09/09/2019 22:44:15

Mine is actually an Ultra STICK. I got confused and spelled it as STIK when I opened the thread and don’t know how to correct it! Either way, they all seem to work well enough!

09/09/2019 21:29:19

Edited By Colin Leighfield on 09/09/2019 21:34:54

09/09/2019 21:25:55

I think the opinions on the diaphragm being dried out might be correct. The new plug arrived from Morris Mini Motors so I fitted it but I don”t think there’s wrong with the old one. I spent a lot of time spinning it with the starter, squirting fuel into the intake and also opened both high and low needles by a turn. Eventually I got it going and worked the needles back to factory settings. There’s a learning curve here for me. Hopefully video will show on the next posting!

Edited By Colin Leighfield on 09/09/2019 21:27:53

Thread: Thinking aloud about Spits...
07/09/2019 21:53:10

All Spitfires from the prototype to the Mk24 had 2.5 degrees of washout from root to top, with positive incidence of +2 degrees at the root and negative -0.5 at the tip. They didn’t tip stall. Generally poor handling models of Spitfires are lacking in wash out and also may have non-scale wing section. The full-size was one of the best handling of all WW2 fighters and considered to be easy to fly. The Hurricane had a sharper stall and would drop a wing when it happened.

07/09/2019 17:46:44

The full size Spitfire in some versions with flaps and wheels down had a stalling speed as low as 58 mph.

Thread: Hobby King Piper L4 Grasshopper 1.4 metre, plug and fly.
06/09/2019 19:02:38

Hi again Alun. I’m pleased that your Navy Cub version has worked out ok, hard to believe that mine is already three years old and having just survived seven weeks in a field it might last for a bit longer yet!

My wife can’t tell one plane from another either, but sadly she can count!

I’ve had a look at stuff on the forum about low voltage LiPos and sadly it looks as if I have to dispose of it. If anyone has another (safe) answer, please let me know!

06/09/2019 15:49:53

089df049-eae9-46ef-aed8-6c01596d7511.jpeg4cfea13f-090f-4e08-8496-a17f07801401.jpeg7aaa7143-3ea3-46d2-942d-6ef1c1c0ce56.jpegIsn’t it odd that I’ve only just noticed Alun’s post dated 23/09/2018! If you are still looking Alun I apologise for appearing ignorant in not having answered your question, which I will try to do shortly.

The reason that I looked again was because of a recent event with this plane! It has been exactly what I hoped it would be, even though I often go far too long between opportunities to fly, I could always depend on this one and the odd hard landing from lack of practice caused minor issues quickly rectified. Although it can be flown in a perfectly scale-like fashion, with 4S it is massively over-powered and flies more like a WW2 warbird!

On 21 July I took it to Fradley Scale Day, not as a competitor (!) but just to fly in between the real pilots. On one flight I took it on a wide circuit at about 50 ft and became disorientated against a dark sky. Looking for a gentle right hand turn to bring it into line with the runway I became convinced that the rather small and black silhouette was turning left. Classic error, I gave it some more right and it went into a spiral dive. I did the usual and thought “radio problem”! It came down in the farmer’s field some distance away, in a crop of some kind of beans varying in height between 4 and 6 ft. I spent some time in the field and found the nature of the crop, plus some kind of “bindweed” growing between made it extremely hard to walk through and even harder to see anything. Eventually I called it a day.

I had the incident on video from my Tomtom Bandit and when I get home I had a look. There my mistake was obvious, the spiral dive was to the right, the plane was turning the right way and my further right aileron caused the crash. Personal incompetence, not a “brown-out”!

I came back the following day and spent a long time searching without any luck. A few days later one e09f10b8-169e-4f29-9d02-b9a6a47fac8a.jpegof my club-mates searched for it with his professional standard camera quad and no luck. I gave up and wrote it off, thinking that when the farmer harvested the crop the plane would be wrecked. Yesterday a post came through on the club FB page to say it had turned up! The farmer had cleared the crop and there was the plane parked in the middle of the field! I can only imagine that he had seen it and deliberately avoided crushing it, many thanks to him.

The photos show the easily repairable damage, although it is going to need painting! The LiPo is a problem because when connected to the charger I just get “low-voltage”, so I need to work that out. It is undamaged though and shows no sign of swelling. I bought the Hangar 9 Ultra Stick to replace this (I told my wife) and now I am getting some funny looks.

Thread: Hangar 9 Ultra Stik 10cc
05/09/2019 13:59:30

Doug and Moss, thank you both. The tacho suggestion is interesting, sounds like there is some experience of this happening? I will include that as I work through the options.

I don’t have a manual switch in the ignition circuit on the plane, I am using one of the auxiliary channels through a toggle switch on the tx and that all appears to be doing what it should. I am working today and won’t get time to have another look until tomorrow. It did occur to me though to see what happens if I connect the ignition directly, to confirm or eliminate where the problem might lie. Incidentally, the RCGF technical literature says that the carburetter is a Walbro, I need to look at it more closely.

04/09/2019 21:49:41

Thank Rich and John. Will do!

04/09/2019 20:30:49

Thanks cymaz and Bruce. Priming by hand I could see fuel pulsing in the line, so it looks as if there is some draw. I will try injecting some fuel into the intake and see if anything kicks off, I would have done that already but being a rear induction motor it’s a bit awkward.

Possible diaphragm issues noted, it is a brand new motor and I haven’t touched anything out of the box, but as so often happens it has been lying around for a year or so before I have tried to use it so there could be an issue there. Hopefully I won’t need a Walbro conversion but you never know.

Same old story isn’t it though, you take on something quick and simple for some extra flying and it turns into a major diversion you can do without!

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