Spitfire IX Project

[Westozy]

Hi Darryl, if you buy copper tube in a coil, it is already annealed (softened), and can easily be bent by hand!

Your sim looks fantastic, it has been a pleasure to make parts for it!

Cheers, Gwyn

[Tony Hill]

Thanks Kermit..I'll try that trick where the bends are too tight or close together to use the bending tool.

Gwyn, cheers mate..The coils are what I bought. Nice stuff.she will be a little longer to be flyable now as I can't get time on the tools to do the big assembly that is left..the monitor tray. The neighbours don't seem to like me running the saws and drills at 23:30!!

It will be late June now before I can do that...NOT happy. I have managed to get the slide pots installed for the Mixture and Prop Pitch....you did me the great favour (or Supermarine did with their design??) of making the throw on those levers pretty much exactly the length of the slide pots!

So all that remains now is for Leo Bodnars card to arrive, the wiring to be completed and the monitor tray and she will be "basically" flyable. The detailing will probably go on for years

[Tony Hill]

The Seat upholstered and the head pad done. He did a great job on both...the seat pad is a "private purchase" item, longer in the back than standard issue (as I am getting too old for hard seats fro 3-4 hours at a time.

[Westozy]

Gwyn, cheers mate..The coils are what I bought. Nice stuff.she will be a little longer to be flyable now as I can't get time on the tools to do the big assembly that is left..the monitor tray. The neighbours don't seem to like me running the saws and drills at 23:30!! (

Saws and drills, I've heard of those hehe... Started your valve thingy, it will be ready for your visit!

Cheers, Gwyn

[Tony Hill]

Saws and drills, I've heard of those hehe... Started your valve thingy, it will be ready for your visit!

Cheers, Gwyn

Great news....I will phone you shortly with another little job to fit in between all things 777.


Darryl

[Tony Hill]

Just ordered from Sefton Clothing Co:

Late pattern Type C Helmet
Type E* Oxygen mask

All fully wired and spliced to a NATO plug, for which I can plug a converter straight into the computer!

I also have a line on an early type Landin Lamp lowering unit.


Not much else done as work is too flat out ATM

[graemesmith]

The position behind the stick and well forward makes it quite hard to see and the parallax error is huge so navigation on the compass alone must have been a nightmare.

Actually no. The reason is that it is an Admiralty Pattern Small Boat Compass of the "grid" type - designed for this situation. If you look at your original with the moving card the procedure would run:

- Release the lock on the top rotating ring and dial on the course you want to fly. Lock the ring.
- Fly round the sky till the card floating in the bowl lines up with the two parallel "lubber" lines on the rotating top ring. This is actually easy to judge from just about any angle as the eye/brain is very good at judging when two sets of lines are parallel. Even when viewed from difficult angles. There is no reason to read the numbers. You just need to fly keeping the sets of lines parallel.
- Then dial the course on the gyro compass on the blind flying panel and uncage the gyro. Fly on Gyro which is in the important 6 instruments.
- Every 10-15 mins check the gyro against the magnetic compass (because the gyro tends to precess).

In practice you hardly ever use the compass except for quick checks.

Those P8 compasses were VERY popular in the UK on small yachts till the late 1970's. With no GPS, Loran or Decca on small yachts we used to navigate for real - just like Spitfire pilots did. With a small yacht heaving around like an airplane - you needed a simple system to stay on course. Keeping the lines parallel after dialing on the course was the way to do it. And of course we were always told we were using "Spitfire" compasses. Though in reality Spitfires were using boat compasses.....

[Tony Hill]

Actually no. The reason is that it is an Admiralty Pattern Small Boat Compass of the "grid" type - designed for this situation. If you look at your original with the moving card the procedure would run:

This is actually easy to judge from just about any angle as the eye/brain is very good at judging when two sets of lines are parallel. Even when viewed from difficult angles. There is no reason to read the numbers. You just need to fly keeping the sets of lines parallel.

- Every 10-15 mins check the gyro against the magnetic compass (because the gyro tends to precess).

In practice you hardly ever use the compass except for quick checks.

Keeping the lines parallel after dialing on the course was the way to do it. And of course we were
always told we were using "Spitfire" compasses. Though in reality Spitfires were using boat compasses
.....

Thanks Graeme, we will agree to differ I fear. (but I welcome friendly discussion any time).

I've used the P8 (or P11 which is idetical in all important respects) in Tigermoths and it is a good
compass..but there it is in clear view over the top of the stick, not hidden half behind a spade grip. A
position which also introduces a curve and another straight line (column spade and straight edge) into
the field of view. It is not a particularly stable compass and in any sort of weather does not settle at all
well, which makes keeping an exact course difficult. As I said, I would have nightmares if navigating
just by it alone.

A DG is also only as good as the accuracy of it's setting against the compass...and the numbers must
be read for that. A preflight check I have read for the Spitfire is "allign DG to runway heading" rather than
Compass. The constant weaving on taxi (voluntary AND involuntary due to the fully castoring tail wheel)
is unsettling to a modern Whisky Compass, let alone that bowl of oil!

You must also remember that in a small yacht you are making what, 5-6 Knots? That gives you a fair
few oportunities per hour to average out the movement, take landmark sightings, chart readings
triagulations etc. In the Tiger' that is 60mph (50odd knots) In a Spitfire cruising at 250mph you have
barely 1/40th of those oportunities. And that is assuming that you can see the ground through the
cloud in sufficient detail to make an assessment (usually done in a Spitfire by rolling 90 degrees
to look straight down, a game not conducive to settling the compass).
At 25,000 a Spitfire's wing covers the whole of south east England (Johnnie Johnson, if memory serves)

A noted Spitfire Recce pilot (whose name escapes me for the moment but whom I could chase up
easily enough) said that it was barely possible to fly within 5 degrees of planned course . 5 deg being
considerable error over, say, 350 odd miles.

The distinct lack of anchorage or sheltered cove in which to take a break and consider the next course
is merely an unpleasant bonus, as is the certain knowledge that what goes up must come down!

cheers


Darryl

[graemesmith]

friendly discussion

Same back!

A noted Spitfire Recce pilot ....... said that it was barely possible to fly within 5 degrees of planned course . 5 deg being
considerable error over, say, 350 odd miles.

You are lucky if a small yacht can achieve +/- 10 degrees

The distinct lack of anchorage or sheltered cove in which to take a break and consider the next course

What anchorage? You have to find it first!! Fog=cloud or fog, Tide=Winds aloft, Sea State=Turbulence, Anchorage to consider next course=handy airstrips dotted all over the clouds to let you take a break!

Couple it to the fact that a yacht engine would often hit resonance with the P8 card which would proceed to circle the bowl at often impressive speeds.

Let alone that bowl of oil!

There's your problem! Every P8 I ever came across was filled with alcohol. Mix the oil and alcohol and it turns milky white. No wonder you can't see it!!

Alcohol made them lively to respond but slow to settle.

[Tony Hill]

Alcohol made them lively to respond but slow to settle.

Has much the same effect on me!