Crewe Model Show 27th Feb 2011

[dr_gn]

Here are some pics of models that caught my eye (for various reasons) taken at my first visit to a model show. I enjoyed it, and felt very much at home mingling with the 'distinctive' smelling, Star Wars t-shirt wearing nerds. Can't wait for Cosford!

[perdu]

great idea posting these doc

A few somewhat familiar subjects too



cheers

[Eric Mc]

Very nice.

I particularly like the FAA displays - pre and post war.

[drivin_me_nuts]

Hi Eric, lovely photos - what is the twin prop 10th picture down?

[Shar2]

drivin_me_nuts said:

Hi Eric, lovely photos - what is the twin prop 10th picture down?

Supermarine Seafire FR-47 with the next contra-prop being a Westland Wyvern.

Edited by Shar2 on Thursday 3rd March 10:41

[Eric Mc]

I think it's a tad "over dirtied". Is it the Airfix 1/48 model?

[perdu]

I am of a similar mind too Eric

I hate these machines looking as if there were no ground crew looking after them

I cannot remember seeing any Fleet Air Arm machines that dirty, "pusser's pride" would have made sure of that

But they are still very nicely made

[dr_gn]

I thought exactly the same: The Seafire is way overdone on the weathering, particularly the cannon smoke stains. Easily done though. Shame really.

[drivin_me_nuts]

Shar2 said:

Supermarine Seafire FR-47 with the next contra-prop being a Westland Wyvern.

Edited by Shar2 on Thursday 3rd March 10:41

Thanks Eric. Out of curiosity what was the benefit of having a contraprop? From my (very limited knowledge of fluid dynamics from a long time ago) wouldn't the inner prop have been running through dirty air and as such not that effective?

[perdu]

Driving_me _nuts amongst other aerodynamic doodahs contrarotating props on the Spitfire airframe helped stop the wild torque steer effect of the huge engine power acting on the aircraft at take off

Not much fun having a tailwheel aircraft that wants to fling itself off the edge of the deck on a tiny wartime carrier on full take-off power

ISTR that the dirty air question does have some effect but far less disadvantageously than losing it over the side




edit 'cos I was too stupid to see who I was chatting with

Edited by perdu on Thursday 3rd March 17:27

[Eric Mc]

As Perdu says, the swing of the 2,000 hp Griffon made these late mark Spitfires/Seafires a real handfull - especially on take off. The RAF settled for the standrd 5 blade prop but the Navy went for a contra-prop to try and alleviate the swing which was a real problem on smalll Royal Navy carriers.

Contra props were also used on the Wyvern and Gannet for the same reason.

[drivin_me_nuts]

Thanks chaps for your replies. I've never seen these planes before and engines dominate the whole frame. It must have been some experience flying the,.

[Eric Mc]

All these last generation piston fighters were real handfulls - mainly because of the huge amount of torque generated. As well as the Spitfire/Seafire family, the Sea Fury, Bearcat and Lavochkin La-9 all had to be handled carefully.

Jets arrived at just the right time.

[drivin_me_nuts]

... so is it fair to say that a prop driven plane would have a natural tendancy to prefer to turn one way more than the other? How would the designers have compensated for this natural tendancy in their design... I guess what i'm asking in very basic terms is which part of the plane prevents/reduces this torque twisting effect?

[Shar2]

The contraprop on the Seafire 47's not only negated swing, but allowed the use of shorter blades, which in the case of tail draggers reduced the prospect of tip strike when taking off and landing.

With the large amounts of torque on the later piston fighters that Eric mentioned I would imagine you'd need quite a large rudder/fin or rudder authority to counter it. IIRC Spitfires needed a good bootful of rudder to keep them straight on take-off. Don't konw which went which way, but I believe the Merlin prop rotated in one direction whilst the Griffon prop rotated in the opposite direction.

[Eric Mc]

Yes, the Griffon and Merlin rotated in opposite directions - which meant that pilots transitioning from earlier versions of teh Spitfire needed to be very careful.

Most WW2 era piston fighters had a degree of offset built into the fin to try and compemnsate for this torque.

[dr_gn]

It's not just torque that's the issue, it's the gyroscopic effect of a huge prop tending to yaw the aircraft when the tail lifts on take off.

The torque effect was used to good effect in aircraft like the Sopwith Camel, which made rolls in one direction much faster than in the other.

[Eric Mc]

The Camel suffered from really odd gyroscopic effects. If you pulled the stick back, the plane darted off to the left or right (I can't remember which). It was extremely counter intuitive and caught loads of pilots out.

[drivin_me_nuts]

.. so on larger multi engined planes were these effects less pronounced? Would it be fair to say the mass of something like a fully ladended bomber would have negated the twisting effects of these very large engines?

[Shar2]

drivin_me_nuts said:

.. so on larger multi engined planes were these effects less pronounced? Would it be fair to say the mass of something like a fully ladended bomber would have negated the twisting effects of these very large engines?

I'd imagine size of the aircraft was a factor on reducing torque and gyroscopic effects. Some twin engined aircraft had handed engines/props to stop the effect.