Spitfire AB910

Nothing unusual about swapping the 3 & 4 blade props around. The first time I got involved was when the gear was selected up on a BBMF Hurricane at Northolt, my first day with BBMF! Shortage of 3 blade type meant fitting a 4 blade.
Usually the basic blade angle is adjusted as often the reduction gear ratio is different and this would affect the reference/static rpm.
Some propeller manuals also give the required basic blade angle change required when the propeller is cropped or different diameter prop fitted.

The Merlins are easily swapped between the Hurricanes and the Lancaster at least, likely P7350 and AB910 as well.

A 20 Series Merlin physically will not fit a Spitfire Mk I/II/V engine mount. The two speed supercharger wheel case for the 20 Series makes the back end too long.

The Hurricane Mk V of 1943 also had a four-bladed prop. Essentially a Mk IV with a Merlin 32, only two were built.

Has MK732 been ‘recreated’ since then from what was left or just the data plate?;)

I think there was substantially more than a data plate to kick-start MK732… 😉

The four blade propeller was fitted to AB910 on or before July 1951 together with a PR XI windscreen. All for civil air racing reasons.

Mark

I think the 4 bladed prop becam a permanent fitting on AB910 when it was rebuilt/repaired after a Harvard collided with it after landing at an airshow at Bex, Switzerland in about 1978. In Michael J.F. Bowyer’s book he says ‘much of a Mk IX, MK732 was absorbed by AB910’ and a Merlin 32 from a Balliol. Hope ARCO can give her back a 3 blader but as always if the budget and the hours for the rebuild project can allow it. Has MK732 been ‘recreated’ since then from what was left or just the data plate?;)

The Merlins are easily swapped between the Hurricanes and the Lancaster at least, likely P7350 and AB910 as well.

No. of props is optimised based on several factors. Sure you need hp to drive it and there is an optimal tip speed….then you have the issue of blades chopping thru the previous blades flow…..same is true for helios……you could write books about it….some have!!!

However, the more propeller blades you have the more drag you are creating. Therefor the more blades you have the larger and more powerful engine you would have. Eg. Spitfire Mk.I’s had two and three blade propellers while the XIX has five.

If I understand it correctly the early spits and hurricanes around ’38ish changed the two blades to three. Hamilton Standard?
But the the biggest improvement was the higher octane petrol from the US had?

I read recently that when the engine was changed decades ago and a hybrid one fitted the prop was nearly out of hours and that three blade ones were very difficult to obtain so a four blade prop was fitted.Dont count on her reappearing with a three blade unit as the flight only has one and that is on P7350.

Ummm, I’m not so sure about that.

As I recall, after 70-odd Mk.I Spitfires, the new 3-blade, two-pitch DH prop was fitted, which gave an increase in performance with no actual increase in engine power. The Mk.II introduced a more powerful engine later on.

I always thought the extra propeller blades were added to absorb the power of the engines.

However, the more propeller blades you have the more drag you are creating. Therefor the more blades you have the larger and more powerful engine you would have. Eg. Spitfire Mk.I’s had two and three blade propellers while the XIX has five.

Sorry another dumb question:rolleyes:

A four bladed prop will have a larger surface area than a three, given the lower power of a V than say an IX how does a four blade affect the performance of a V?

Told you a dumb question:D

Without the books in front of me, I think the four-blade prop added a few MPH onto the top speed of the wartime Mk.V. Supermarine modified a standard VB with a four-blade prop (among other things) sometime in 1943, and the various mods added a good few knots.

I’m sure someone far better qualified to comment will come along, but as I understand it all the BBMF Merlins are of the same type. Retro Track & Air and BBMF have devised a “BBMF standard” Merlin, allowing interchangeability of engines between types (Spit, Hurri) and also the fitting of different props. This is just my ‘third party’ understanding as I’ve heard it, I could be well off the mark.

On the subject of Hurris with four blade props, IIRC G-ORGI flew with a four blader for a time. Apparently a four-blader isn’t a happy match on a Hurri as the prop helix is different, which affects the stability.

Original airworthy de Havilland 5/20 prop hub assemblies are as rare as rocking horse poop and very, very expensive to build new. Rotol 3 blader hubs aren’t a whole lot more common.

Pretty much a case of make do and mind the budget.

Would it have anything to do with the series of engine fitted or has the horsepower got nothing to do with it?

If you think 4 blader Spits are odd, I can remember visiting the BBMF in the 80s and LF363 was sporting a four bladed prop. She did not have it on for long. I had not noticed when I was sat in her cockpit, until DP came and asked me if I had noticed anything odd.

Sorry another dumb question:rolleyes:

A four bladed prop will have a larger surface area than a three, given the lower power of a V than say an IX how does a four blade affect the performance of a V?

Told you a dumb question:D

Probably more to do with what’s available when needed.

Is it because there are more four blades available than three?

AR213 certainly did up until her rebuild a few years ago.

P7350 has done on several occasions.

Spitfire VB EP120 had a four-blader for initial test flights, I think, back in 1995.