Lancaster has Corsair blades?

Profile picture for user Oxcart

Member for

11 years 10 months

Posts: 2,090

Who knew? (Possibly everyone on this forum except me!)
Original post

Member for

11 years 8 months

Posts: 2,841

No it doesn't - well not exactly! The Hamilton Standard "paddle" blade was manufactured and then cut down to suit the application. The Corsair used blades which were only slightly cut down from the full-size blank, and other types used the same blade which was cut down even more. Off the top of my head; other types which used the same blade, but cut down to their requirements were: C-54/DC-4, Hellcat, B-24, B-17, DC3/C-47 and the Lanc (though these blades were made by de-Havilland under licence from Ham-Stan to the same pattern), along with the York/Lancastrian. You will see much the same blade also on the Halifax (again by de-H) and the Mossie, the only real difference between all those blades being the amount cropped from the full-size blank. It was a straightforward and simple idea that made it easy to match a prop to an engine/airframe type. Anon.
Profile picture for user ZRX61

Member for

14 years 4 months

Posts: 4,789

Off the top of my head; other types which used the same blade, but cut down to their requirements were: C-54/DC-4, Hellcat, B-24, B-17, DC3/C-47 and the Lanc (though these blades were made by de-Havilland under licence from Ham-Stan to the same pattern), along with the York/Lancastrian.
& modified DC3/C47 blades get used on Hurricanes. We shipped a couple of sets to the UK some years ago.
Profile picture for user Beermat

Member for

9 years 11 months

Posts: 3,422

As far as I know de Havilland didn't make any of the 'paddle' type blades, could be wrong though. They DID make the 'needle' Lancaster blades the DP455800, and that was indeed a copy of the Hamilton Standard 6353. This blade goes back further though - when fitted to a bracket-type hub it was the Hamilton 6503, and when made by DH it was the 55200 series that goes as far back as the HP Harrow. The Halifax used de Havilland 451100 and 451700 drawings, suitably cropped of course - and I don't think these had a US equivalent. There is a chap building a Halifax out in Canada right now who would be delighted to find that they did, but there's no sign. When it came to Hercules engines they were designing their own - starting as far back as the Short G-Class. Edit - ZRX61, C-47 blades on Hurricanes - I've seen them, and they look wrong - and I doubt they are particularly efficient either. It's funny how much 'no-one knows, but it fits the socket so it'll do' seems to have happened with props in an otherwise heavily regulated sphere. There was a Spitfire Mk.I flying recently in the UK with a cut down T-28 prop.

Member for

10 years 10 months

Posts: 952

Which is possibly because the warbird community do not need particularly efficient props: it is better to have one that works to a limited flight envelope than a non-flying aeroplane. I can imagine it being more important on a twin with single-engine safety speeds?
Profile picture for user powerandpassion

Member for

7 years 3 months

Posts: 1,196

I can’t think of any part of an an historic aircraft which has more punting and voodoo than blade setups. Only through the historical fortune of US radials and Merlin’s being RH tractor has a pathway to keeping many historics in the air evolved, albeit with ‘suck it and see’ engineering. Of course there are Jablo blades for Rotol hubs, but after the irony and cash spend are accomodated, until somebody forges more Rotol hubs, this pathway is petering out. Truly there is a good future in ‘standard’ E shank HS RH & LH tractor chunky forgings that can be machined to match original specs, both to please aesthetes and achieve original design function. Today CAD programs such as Solidworks can simulate wind tunnel testing and show in pretty colours how good, bad or ugly some selections are, particularly for low speed, low height, low power display at various air densities. Even if you select the optimal blade, a used blade has often been randomly shaped by a tobaccy- chewin shaper with headphones on, so for true entertainment, a 3D scan of actual blades and simulated wind tunnel will show what is truly happening. Probably there are a lot of high power engines making pavlova from air today with inefficient blades, but as long as the thing flies, nobody is wiser. Unless you are going for a speed record, no one is really driven to look for something better and the topic of blade design is obtuse for most. The thing that will change is the lack of parts, a race between Rotol hubs and HS blades with meat on them. Then somebody has to invest in large forgings. I vote Beermat to run this operation!
Profile picture for user powerandpassion

Member for

7 years 3 months

Posts: 1,196

Beermat, dH Australia made paddle blades for Mosquito and many US types. The Corsair and Mosquito blade probably came from the same forging blank. DH Australia also made Fairey Reed metal props and later Hartzell blades until the 60’s. For anybody looking for Fairey Reed drawings for late 30’s Ansons, Gladiators, drawings exist at HARS Archives in NSW. Fairey Reed props are a limited pathway for low to high power fixed pitch LH tractor British radials to stay in the air, but these can, of course, used fixed pitch timber props. The real challenge are the constant speed setups of the 40’s.
Profile picture for user Beermat

Member for

9 years 11 months

Posts: 3,422

P&P, dH Australia - they keep coming up as the link between British dH and the Americans, and I didn't realise they made paddles as well. I'm sure you're right about the Corsair and Mosquito, and of course that design is up there on the list of new forgings that will become useful in the future. Add to that the 6503 (everything from Battle to Lancaster and a fair few US designs too), 6339 (Spitfire), 6127/6128 right- and left-handers for British and US 800-1000hp radials and some LH Hercules blades (5511xx and/or5517xx) and that's the 'product set' right there. The 'as long as it flies' argument is all very well, but efficiency isn't just about performance, it's about fuel economy as well.
Profile picture for user ZRX61

Member for

14 years 4 months

Posts: 4,789

I recall a deal where someone at Dx (Ray or Mark H maybe?) flew something with the prop from something else & didn't like it one bit. Possibly a Buchon prop on a Spit or P51? It was one of those "right, we won't do that again" moments.

Member for

11 years 8 months

Posts: 2,841

I was specifically talking about "paddle" blades, not the pethora of "needle" (both those terms were coined by the prop manufacturers) blades which were in use either/and early on and on smaller aircraft types due to lower power absorbtion requirement. Paddles became better all round, especially for radials where the inner sections of the blades pushed a bit more air through the motor before the speed increased as it got airborne. I really don't think paddles could be easily, or successfully, reprofiled to needles for the Hurricane mentioned. The "meat" of the blade was not in the optimal place so I'm not surprised it looked a little wierd. One might assume, with the Lancaster, that the engine's power must have increased to require the switch from the "needle" to the "paddle" blades, the latter, at least theoretically, requiring or absorbing more power to match. Certainly not - the lanc stayed with the Merlin XX/20-series throughout. What happened was they realised the performance was better at height with the larger blade area, as well as a couple of other factors, so all it needed was some resetting of the blade angles to allow it to operate properly and not, as might be the case, to absorb too much power to the point that the engine would not achieve the requisite RPM at the correct throttle setting. In short; the paddle blade was more efficient and the altitude performance and slower speed cooling of the Lanc improved thereafter. Of course, as is typical with this propeller lark, there comes along the exception(s) that defy the rule(s) so, what happened to the Lincoln? - they put a four-blade unit on with needle blades, so contradicting the theory that they were less efficient than the paddle. They did indeed put nice big paddle blades on the prototype Lincoln but, presumably, the needles worked better. Without research, perhaps the Lincoln was not meant to be a high-level bomber after all? All this lovely theory and testing stuff is now lost to the mists of time, apart from the odd snippet gleaned from some expert or other being quoted in an old publication. Note also that Mosquito went from needle to paddle blade with the same engine. Same as the Lanc, they adjusted stuff and it worked better. Paddles became standard on Mossie as due to later major power increases they had to increase blade area as they couldn't increase the diameter (the blade tips were only 3ins from the fuselage). However, it didn't stop T.III trainers with Merlin 21/22 switching to paddle blades as well. As an Aside; I owned a Mossie paddle blade prop some years ago and I was struck by the thinness and quality of the blades compared (roughly) to the US equivalent size used on C-47/B-24/B-17 etc. Of course the US H-S blades would have been cropped to suit their application, but they were much thicker and heavier. The Mossie (de-H) blade was very much thinner and lighter so I would certainly believe that they were made to that diameter, not cropped from a larger blank. It was certainly a very nicely made blade to which, in my eyes, the US-made blades did not compare favourably at all. I could go on all night but I'd better not. Anon.
Profile picture for user Beermat

Member for

9 years 11 months

Posts: 3,422

There aren't many places where I find people who know their stuff talk at length about propeller blades. Please go on, Mike! Just to add that the broader 'paddle' was initially an American solution not just for power absorbtion (most of the power was transmitted around the 0.7r station, which was always kept broad, not the tip) but as a way of delaying the onset of Mach drag. This kicks in according to thickness-to-chord ratio, not just thickness. Hamilton Standard, as noted, were incapable of making blades any thinner, so instead they made them broader to decrease thickness-to-chord around the tips and make them more efficient at high Mach. This is why they proved better at high altitude on the Mosquito - the speed of sound gets lower the higher you go, and relative Machs are of course higher for any given rpm/forward speed. De Havilland made their blades thinner - starting with their deliberate thinning of the HS 6339 from 9% to 7.6% t/c at 0.7r for the Spitfire's 55409 (they didn't do the same with the Whirlwind 54409 blade, with disastrous results). I have heard it from several sources that the thinner DH versions of blades were preferred by pilots. The broader DH Mosquito blades were from smaller blanks. They were 4551212, cut down 6 inches per blade from 13ft, while the US blades were complete paddles, cut down from 15ft, and fat. I don't know about DH-made complete paddles, did you get a drawing number for the Mossie blade you had? Maybe it was an 'Aussie Mossie' blade?
Profile picture for user powerandpassion

Member for

7 years 3 months

Posts: 1,196

Oh this is getting controversial! Now you’re saying the Trump Mosquito paddle blade has eaten more hamburgers than the British Mosquito paddle blade ! I need definite proof before I hand good beer money over on this. As a separate issue, my understanding of paddle blades relates to my experiences with ice cream tubs. So the fatter scoop digs out more ice cream than the thinner scoop. Now change ice cream for air and the fatter blade is chippy-chopping more air than the thinner blade, at same RPM. I would want to do this if the air is thinner, way up. So I associate paddle blades with the race to go to 40,000 feet, stay above the flak and lessen the chance of interception. Then I have to rise in England and land in Russia, so I lean out my engine, balance power and RPM to ice cream scoop as much thin, icy fraulein deutcher air as possible for the minimum fuel spend. So that’s why I have paddle blades. After the war I want to send my DC4 as far as possible for minimum fuel spend so I stick with the paddle blade formula. Toothpicks fade from memory. Toothpicks were really about getting Spitfires and Hurricanes up as fast as possible in 1940, which is all Britain cared about then. Then I’m told I’m joining 618 Sq to Highball Japanese cruisers at sea level, where I want to transmit as much power as possible into thick air, so I change my Mosquito setup from three paddles to four toothpicks, back to trying to push as much air past me as possible. Now my big ice cream scoop, so good for pulling big scoops of watery ice cream might not be that good for pulling big scoops of chunky, solid ice cream. I might find weird torque affects when I push the throttle to the gate, chasing the devilish Luftwaffe. I really need a chopstick and to put the tub up to my mouth and flick little bits of delightful dairy goodness, or thick air, into my gob as fast as possible. In fact four chopsticks, Bruce Lee style, would be better than one. I am sort of exploring Force = Mass x Acceleratation, where air density influences Mass, RPM deals with Accelaration, where I am stuck with an engine, or Force, in both cases of 1,000 HP. Really I am trying to keep my RPM in a fixed range, so the Conrad’s don’t pop out, so I invent a constant speed airscrew which makes a blade fatter or thinner within limits. So flip-flopping between scoop and chopstick. Now later in the piece I am using 130 octane and getting 2,000 HP, so I am finding that I can actually push more mass, so I can use my big ice cream scoop paddle blade on a ground attack aircraft, where fuel burn is a non issue, because I am landing at an airfield only 10 miles behind the front. I hope this has lifted the scientific tenor of discussion and I apologise to any vegans for not using vegetable based analogies. I guess blade design comes from marine work and if you look at devilish torpedo blade setups and understand that speed through fluid with a short, brutal ‘fuel’ burn was the aim you start to see ice cream moving, or at least I do. Really the whole theory is there in the varying blade configuration in a jet engine, which was originally designed by Frank Whittle to make butter.
Profile picture for user powerandpassion

Member for

7 years 3 months

Posts: 1,196

dH also made blades out of magnesium, so the lighter blade might be that. Now I am not sure that Uncle Sam HS made magnesium blades, and generally if an aluminium formula worked and you had Alcoa, why change? Britishers finally made local magnesium from seawater and dolomite in 1939 and aluminium cost shipping and lives to U boats, and aluminium was needed for Spitfires, so magnesium blades were very attractive in 1941. Of course the big design issue is centrifugal force, as I learnt when over speeding an industrial fan, destroying it, so lower mass magnesium, for the same mechanical strength, could allow you to design a different shape, certainly less meat in the shank, a double benefit. I think fat shanks are about material strength and managing centrifugal and torque reactions. We don’t know about magnesium blades because it was probably just a British thing, it wasn’t needed after the war and whatever remained fizzed into powder.
Profile picture for user powerandpassion

Member for

7 years 3 months

Posts: 1,196

When I destroyed the industrial fan, I went into the library to hide, to eventually find an engineers handbook from 1890, which dealt with HP restrictions on steam engines, caused by cast iron flywheels shattering from centrifugal forces rather than the intrinsic capacities of steam engines. It was only after better metallurgy created stronger flywheels, able to resist centrifugal shattering, that more powerful steam engines could be developed. I think a 50 year old blade designer in 1941 would have learnt his craft on marine engines and marine propellers, so a lot of the basic stuff is there 130 years ago. Of course you can learn a little bit from reading and then you can learn a lot from making a mistake, which is a tough but good school.
Profile picture for user ZRX61

Member for

14 years 4 months

Posts: 4,789

Of course you can learn a little bit from reading and then you can learn a lot from making a mistake, which is a tough but good school.
It's much better to learn from the mistakes of others, cheaper too & sometimes rather entertaining. ;)

Member for

10 years 10 months

Posts: 952

Rotol initially made magnesium blades, and one squadron of Spitfires was equipped with these in Spring 1940 - there's a photo of one down in the sands of Dunkirk. However they were abandoned - I hadn't realised that DH made some later in the war.

Member for

11 years 8 months

Posts: 2,841

Yes, I was going to say that Rotol had made some mag-alloy blades - but they were fitted to the Whitley. The Rotol hubs were designed such that various materials could be used for the blades with a suitable adaptor. One thing that seems to have emerged from our conversations, above, is that Mossie blades were from a shorter blank which, in itself, would lead to a thinner blade section. Think of it this way; as a tapered form which, the closer you cut it down to its base, the thicker it becomes i.e., more dumpy. The H-S method of starting with a longer blank would result in this happening, though it has to be said that, although the resulting section would be thicker, it probably didn't make much difference to the efficiency of the prop. At least not enough to justify another method, and much easier under the pressures of war time production. I was not aware that H-S or de-H had made production blades from different materials, though I can see that it would have been very easy to do so given the simple and universal way they were retained in the hub/barrel. Aluminium and copper were relatively plentiful in the US during WW2 so there would be no real need to investigate other materials, perhaps only to prove the case that they could be utilised. Just to round off, I enjoy the colourful descriptions of P&P's text and enjoyed this one: "creating a pressure differential through the relative speeds of ice cream over the surfaces of your spoon". That's a cracker! Are you a teacher, by any chance? Finally, thanks to Beermat for his facts and figures. They certainly helped to broaden the discussion. Anon. EDIT: I've quoted from Beermat's post but P&P is the instigator of the interesting and hilarious but practical ice cream scoop analogy.
Profile picture for user powerandpassion

Member for

7 years 3 months

Posts: 1,196

Ahh, that’s Beermat with the good quote! I think in any difficult topic you need an Idiot and an Expert on the panel. Beermat is the expert. In the face of the wall of competence from the expert, most folks are cowed into silence. So the role of the Idiot is to get the Expert to roll their eyeballs and explain things s l o w l y using ice cream as an example...it’s amazing the illumination that can come out of basic principles. The Idiot, too idiotic to be cowed by the expert can also say dumb things like ‘ is that an iceberg ahead?’ which once every 28 times saves the ship, the other 27 times being saved by the Expert. Really what we are getting here on the fascinating topic of props is a barstool conversation, and I’m learning a lot and lovin it. Now does travelling through rain increase or decrease the speed of an aircraft, or does increased reaction of blades against raindrops balance increased resistance of fuselage to raindrops?
Profile picture for user Beermat

Member for

9 years 11 months

Posts: 3,422

Not at all, Ed. It was the experts who said it was unsinkable - or were they the idiots?

Member for

10 years 10 months

Posts: 952

I suspect it was the company PR that said it was unsinkable - no real expert ever said anything without qualifying it. Which may not have mentioned icebergs...
Profile picture for user Beermat

Member for

9 years 11 months

Posts: 3,422

Icebergs and Ice cream.. the world of propellers is a weird and wonderful place.So here's the thing - the reason it all seems so mysterious and full of witchery and riddles is because there has never been a 'Big Book of Propellers' With Ed's gift for imagery and my nerdism I think we could put together something to fill the gap. You can get mathematical treatises and manufacturing company histories, but nothing to put things into focus for normal humans. Anyone know any publishers? Actually being serious here. Ed, you up for it?