 | Propeller Design| Aviation Discuss Propeller Design in the World War II - Aviation forums; First off, great forum people. Now the question. I have always wondered as the war progressed why american planes went ... |
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07-19-2006, 08:25 PM
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#1 | | Junior Member
Join Date: Jul 2006
Posts: 4
Country:  | Propeller Design
First off, great forum people. Now the question. I have always wondered as the war progressed why american planes went to a broad four blade design of prop while the RAF seemed to favor a slender five blade design and the germans kept a large three blade paddle type. What were the reasons or benefits of each.
Thanx! | 
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07-19-2006, 09:10 PM
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#2 | | IP/Mech THE GREAT GAZOO
Join Date: Apr 2005 Location: Colorado, USA
Posts: 12,675
Country:  | It was all a matter of the methodology used by the engineers for squeezing the maximum amount of power from the engine while achieving maximum efficiency.
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07-20-2006, 04:31 AM
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#3 | | Senior Member
Join Date: Mar 2005
Posts: 240
| It depends how fast you want your prop to spin. More blades are more efficient for a faster-spinning prop. | 
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07-20-2006, 05:25 AM
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#4 | | Der Crewchief
Join Date: Nov 2004 Location: Ansbach, Germany
Posts: 28,863
Country:  | I think it also had to do with the design of the aircraft and how to get the most from that aircraft. Some Luftwaffe aircraft had 4 blades instead of 3. Some British had 3 blades instead of 4. Some US aircraft had 3 instead of 4.
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07-20-2006, 05:44 AM
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#5 | | Senior Member
Join Date: Jan 2005 Location: Saffron Walden/Sheffield
Posts: 3,001
Country:  | I always thought that the general rule was the more hp the engine gives the more propeller blades it had
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07-20-2006, 05:56 AM
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#6 | | Der Crewchief
Join Date: Nov 2004 Location: Ansbach, Germany
Posts: 28,863
Country: | I dont think so. Look at the Ta-152. It had well over 2000hp and only had 3 blades. Look at the Bf-109K and so forth.
__________________ US Army Blackhawk Crewchief 2000-2006 Classic ww2aircraft.net quotes: fly boy said: "isn't that the first jet bomber? becasue i have flown one in a flight sim before and i know how it handles" "wait what ok who made the b-2 crash come on people that messed up its a b-2" "ah yes the mistel those things are so annoying is games and in real life" | |
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07-20-2006, 09:43 AM
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#7 | | Senior Member
Join Date: Feb 2006 Location: City of the Angels California
Posts: 810
| It even got as banal as the height of the landing gear struts positioning the nose above the runway for tail draggers at least. A shorter height gear kept the nose lower but limited the diameter of the blade arc. It is much easier to steer and see on the ground and easier to take off if the nose isn't pointed heavenward at a steep angle. So 4 blades of less over all diameter gave as much or more power than a large diameter 3 blade. A fighter had to still have clearance when you brought the tail up on takeoff when the fuselage was level.
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07-20-2006, 11:22 AM
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#8 | | Senior Member
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Country: | right, gotcha
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07-20-2006, 12:01 PM
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#9 | | Senior Member
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Posts: 681
| The P-47 was the first fighter to feature telescoping landing gear struts to give the gear more length when extended for this very reason. | |
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07-20-2006, 01:20 PM
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#10 | | Senior Member
Join Date: Mar 2005
Posts: 240
| Quote: |
Originally Posted by mosquitoman I always thought that the general rule was the more hp the engine gives the more propeller blades it had | As I said before;
"It depends how fast you want your prop to spin. More blades are more efficient for a faster-spinning prop."
Which is why more modern wind turbines (well depending on where) have one propellor and a counterweight. | |
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07-20-2006, 08:05 PM
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#11 | | Junior Member
Join Date: Jul 2006
Posts: 4
Country: | Thank you gentlemen for your thoughts. I agree that height is an issue I beleve that is why the Vought F4U had a cranked wing. RPM's and horsepower may figure but as stated most late models had big HP numbers, although I'm not sure about RPM's. Maybe the materials used had an affect, (were German props made out of wood?). Tip speeds need to remain sub-sonic too. Anyway thanks again for answering this trivial question.
Oh, the best fighter of WW2?- F6F Hellcat! | |
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07-20-2006, 08:06 PM
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#12 | | Junior Member
Join Date: Jul 2006
Posts: 4
Country: | Propeller Design
Thank you gentlemen for your thoughts. I agree that height is an issue I beleve that is why the Vought F4U had a cranked wing. RPM's and horsepower may figure but as stated most late models had big HP numbers, although I'm not sure about RPM's. Maybe the materials used had an affect, (were German props made out of wood?). Tip speeds need to remain sub-sonic too. Anyway thanks again for answering this trivial question.
Oh, the best fighter of WW2?- F6F Hellcat! | |
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