Would you say that having ray hannah own MH434 has its increased its value rather than joe bloggs?

I don’t know who joe bloggs is. Is he a warbird owner … 😮 … ? No matter what, I don’t think any Spitfire or warbird in general has depreciated since civilians started flying them. The problem is deciding which cost is an operating cost and which cost should be regarded as an addition to the investment.

Christer

Yes, I`ll stick to aircraft engines I think!
I don`t think it would worry Peter Svensson, he is usually up for most things. Do you know him?

Pete

That’s a common swedish name and I know a few of them. Probably not the one you refer to, though.

Christer

galdri,

Next, again using the Spit as a measurement, all the way up to the end of the production, elevators and rudders were fabric covered. The Spit, and certainly the early ones were very marginally stable (some might say very unstable) in the longitudinal (how do you spell that) axis due to aft center of gravity. A number of Mk.V broke up in midair. The fix was to add bobweights in the contol run to fool the control forces felt by the pilot, and assist in bringing the problem under control. It worked a treat! No more inflight brake ups. So the reason an aircraft like the Spit has fabric covered elevator and rudder is due to weight saving measures at the tail, to have the center of gravity as far forward as possible. To fit metal surfaces with (possible) mass ballance would have made the instability even worse! I´m open to suggestions

It has been years since I read “Spitfire – The History” and other books on the subject. I remember reading about the bob-weights in the context of the trainer. The second seat moved the CG backwards and the aircraft had a tendency to “tighten” the turns. It became so light in pitch that the pilot(s) pulled more than intended. To counter act this tendency, an adjustable bob-weight was fitted to the control stick in the aft cockpit. It was attached forward of the hinge point. The result was that when G-load builds up, the bob-weight is also affected by the G-load and counter acts the “tightening” by pulling on the stick forwards. As you point out, it also “adds” to the control feel of the pilot(s).

Christer

For the engine itself, disregarding propeller efficiency and tip speed, piston speed is what limits RPM. The higher the piston speed the higher the G-loads on the crankshaft and bearings. Light weight design and limited stroke are requirements for high rpm. I don’t remember exactly but in an F1 engine, piston speed is 22-23 m/s.

For a Merlin, that piston speed and ~152 mm stroke (6.0″) result in ~4400 RPM.
For a Griffon, that piston speed and ~168 mm stroke (6.6″) result in ~4000 RPM.

Merlins, Griffons and “light weight” are never mentioned in the same sentence and I doubt those theoretical RPMs are achievable.

Christer

Smith,
in a discussion, there’s always a proportion of speculation. If there wasn’t, it wouldn’t be a discussion but a presentation of indisputable facts. How boring would that be?

When we create our posts, we have a “quote button”. Maybe we should have a “speculate button” … :p … ?

Christer

… should we make a WWII fighter design “mistakes” thread (Germany vs Britain)?

Oh no, please don’t … 😮 … it would only be a display of our own ignorance. One example is the mentioned “Miss Shillings orifice” which wasn’t the best the brits could do. The injection carburettor (injecting the fuel into the eye of the supercharger) was in some respects more efficient than the german direct injection since it provided charge cooling. I think all two-stage engines and the late-war single-stage engines were equipped with these injection carburettors.

I will stop now because I feel that I have displayed enough of my ignorance!

Christer

cotteswold,

By the way, that is ‘my’ Christer??

Are there more than one … 😮 … ? Well, I can’t tell since I don’t know who you are!

Christer