Re: Prop Question for Keith Willshaw???

On Apr 19, 9:34 am, "Keith Willshaw" <keithnos...@xxxxxxxxxxx> wrote:
"Rob Arndt" <teuton...@xxxxxxx> wrote in message

news:b02e6a85-a80b-4c4c-b8ed-fcb1c900d8d8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

In the other prop thread you said that "more power, more blades" and
used the Spitfire as an example going from 2-5 blades during its
longevity.

OK.

But what do you have to say for the Me Bf 109 that shared that same
longevity and only went fron 2-3 blades up from 635 hp (V-1) to 2,000
hp (EP for the K-4)???

The detailed propellor design changed considerably.
Early versions used a simple fixed pitch prop, the Emil
had a variable pitch prop and the Me-109G had a more
advanced smaller diameter prop



There is also the DB- Spitfire- a captured Mk.V that was fitted with a
DB-605 of superior hp. No change in 3-prop except the Germans swapped
the British one out for a German one...

Which means a BIG change as the British propellor would be a
Rotol constant speed unit

Please explain how "more power, more blades" doesn't work with these
examples.

German propellor design  in many ways lagged behind allied
practise. They were still using manually selected variable pitch
designs long after the western allies adopted automatic constant
speed units

Were the German VS props superior as well ;)

Considerably inferior in fact.

Keith

First off, I should have said VDM props and by the end of the war that
company was exploring a supersonic prop (do not know if they
prototyped one)- so VDM cannot be said to be inferior- AFAIK, no
Allied supersonic type was being investigated.. Consider also the
early contest of prop development in WW2 by the Germans:

In some respects, Germany had led the way in propeller design by
introducing wide, broad chord blade propellers. If one looks at the
narrow chord blades of the Luftwaffe’s Bf 109E fighter and compares
these to the later Bf 109G, it is readily apparent that the latter’s
propeller blades have widened considerable. The earlier VDM, variable
pitch propeller worked reasonably well at converting the Daimler-Benz
601 engine’s power into thrust. However, as the weight and drag of
subsequent models increased, so did the horsepower requirements. With
the increased power came the need to utilize that power in a more
efficient manner. Thus, German engineers looked to the propeller
design as the solution to getting the power to the road, to use the
common metaphor. Ultimately, these engineers decided to remain with
three blades, rather than four (or more) as incorporated by British
and American designers. It must be assumed that the efficiency of
their design did not require more than three blades. Perhaps the
penultimate example of the German three-blade design resides in those
used on late war fighters such as the Fw 190D and the Ta 152. Indeed,
the chord to span ratio of these propellers is dramatic in comparison
to the “toothpick” blades used on virtually every fighter in the
American inventory through 1942. Another noteworthy observation of the
German designs shows us that the propeller blades were not “clipped”,
or squared off. The blades have a semi-elliptical trailing edge that
tapers to a tight radius at the tip.

I would say that the German VDM props worked well enough for the
German fighters that there was no real need for any 4-5 blade
modifications with the increasing hp. The 4-blade prop Fw-190C
Kangaruh seems to prove that. It had inferior hp to the Fw Ta 152
which used a 3-blade and attained 472 mph.

I believe that the Allies believed their designs were better, but in
actual combat with German 3-blade prop a/c the victory went to the
Allies with numerical superiority. The top kills went to the Luftwaffe
Experten, hopelessly outnumbered and in bulked-up Me Bf 109s that were
nowhere as graceful and forgiving as the Mustangs and Spitfires.

Rob
.

Relevant Pages

  • Re: Prop Question for Keith Willshaw???
    ... early contest of prop development in WW2 by the Germans: ... propeller blades have widened considerable. ... pitch propeller worked reasonably well at converting the Daimler-Benz ... German engineers looked to the propeller ...
    (rec.aviation.military)
  • Re: Prop Question for Keith Willshaw???
    ... early contest of prop development in WW2 by the Germans: ... propeller blades have widened considerable. ... pitch propeller worked reasonably well at converting the Daimler-Benz ... German engineers looked to the propeller ...
    (rec.aviation.military)
  • Re: Prop Question for Keith Willshaw???
    ... used the Spitfire as an example going from 2-5 blades during its ... Early versions used a simple fixed pitch prop, ... Germany had led the way in propeller design by ... German engineers looked to the propeller ...
    (rec.aviation.military)
  • Re: Number of blades on a propeller
    ... I know that having more blades ... A propeller is basically a set of wings, ... These cause losses. ... At low speeds, it really doesn't matter whether the solidity comes ...
    (rec.aviation.military)
  • Re: Number of blades on a propeller
    ... I know that having more blades ... > A propeller is basically a set of wings, ... > At low speeds, it really doesn't matter whether the solidity comes ... 190D-9 they had a water cooled Jumo 213 engine, ...
    (rec.aviation.military)
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