Page 1 of 2 1 2 LastLast
Results 1 to 15 of 21

3 Blade vs 4 Blade props

Other Mechanical Systems Tech. Discuss 3 Blade vs 4 Blade props in the Technical forums; Can anyone tell me the advantages / disadvantages of each. Seems to me the more blades the more air it ...

  1. #1
    Senior Member Thorlifter's Avatar
    Join Date
    Jun 2004
    Location
    Dallas, Tx
    Posts
    7,282
    Country
    United States
    Post Thanks / Like

    3 Blade vs 4 Blade props

    Can anyone tell me the advantages / disadvantages of each. Seems to me the more blades the more air it would grab.


  2. #2
    Senior Member comiso90's Avatar
    Join Date
    Dec 2006
    Location
    FL
    Posts
    3,672
    Country
    United States
    Post Thanks / Like
    Good question....

    I imagine the more blades, the more complicated the feathering mechinism would have to be.

  3. #3
    IP/Mech THE GREAT GAZOO FLYBOYJ's Avatar
    Join Date
    Apr 2005
    Location
    Colorado, USA
    Posts
    21,594
    Country
    United States
    Post Thanks / Like
    The number of propeller blades are determined by engine HP, Blade length and engine RPM. based on this engineers determine how to get the most "bite" from the engine and propeller combination. There was an aircraft flown with a one blade propeller said to be the most efficent.

  4. #4
    Senior Member comiso90's Avatar
    Join Date
    Dec 2006
    Location
    FL
    Posts
    3,672
    Country
    United States
    Post Thanks / Like
    Antonov An-70

    ...
    Attached Thumbnails Attached Thumbnails 3 Blade vs 4 Blade props-prop.jpg  

  5. #5
    Senior Member
    Join Date
    Jan 2007
    Location
    Vantaa, Finland
    Posts
    302
    Country
    Finland
    Post Thanks / Like
    Last edited by Cyrano; 07-21-2011 at 12:19 AM.

  6. #6
    IP/Mech THE GREAT GAZOO FLYBOYJ's Avatar
    Join Date
    Apr 2005
    Location
    Colorado, USA
    Posts
    21,594
    Country
    United States
    Post Thanks / Like
    Quote Originally Posted by Cyrano View Post
    Wouldn't it be unbalanced?
    No, it was offset with a counterweight.

  7. #7
    Senior Member Thorlifter's Avatar
    Join Date
    Jun 2004
    Location
    Dallas, Tx
    Posts
    7,282
    Country
    United States
    Post Thanks / Like
    Quote Originally Posted by FLYBOYJ View Post
    The number of propeller blades are determined by engine HP, Blade length and engine RPM. based on this engineers determine how to get the most "bite" from the engine and propeller combination. There was an aircraft flown with a one blade propeller said to be the most efficent.
    That makes sense. But how do you explain, for instance, the Corsair. They had 3 blades and 4 blades, but it was the same engine, give or take 100 hp.

  8. #8
    Siggy Master Wurger's Avatar
    Join Date
    Jun 2005
    Location
    Poland
    Posts
    33,746
    Country
    Poland
    Post Thanks / Like
    FlyboyJ is right.Look at early WW2 fighters ( Spitfire,Bf-109,).At first, they were equipped with two-blade propellers, but when their engines became more and more powerful they had to be fitted with 3 or 4 blade props ( Spitfire Mk.XIV and later with 5-blade prop even,Griffon engine had really a big power) to make the props working effectively.It seems that the German engineers chose a different way to solve the problem.Fw 190s,Bf 109s and other later a/cs were equipped with props that had very wide blades.As far as F4U Corsair is concerned.The plane had so powerful engine that if its prop would have to work correctly the blades had to be very long.As a result the Vought firm made the fighter using the "W" shape of the wings ( in front view) to equip the plane with the engine and prop.It seems that the 4-blade prop worked much more effectively with the powerful engine.
    Last edited by Wurger; 05-27-2007 at 02:12 PM.




  9. #9
    IP/Mech THE GREAT GAZOO FLYBOYJ's Avatar
    Join Date
    Apr 2005
    Location
    Colorado, USA
    Posts
    21,594
    Country
    United States
    Post Thanks / Like
    Quote Originally Posted by Thorlifter View Post
    That makes sense. But how do you explain, for instance, the Corsair. They had 3 blades and 4 blades, but it was the same engine, give or take 100 hp.
    In actuality when the Corsair went from a 3 blade to a 4 blade prop, the engine did change (different dash number) as well as altitudes the later models were operated at. I think this was at the thinking of the engineers who made these changes.

    Check this out...

    A Single-Bladed Prop? What the h....?

  10. #10
    Senior Member comiso90's Avatar
    Join Date
    Dec 2006
    Location
    FL
    Posts
    3,672
    Country
    United States
    Post Thanks / Like
    Wurger...

    You have the best "sig pic". did u make it yourself?

  11. #11
    Siggy Master Wurger's Avatar
    Join Date
    Jun 2005
    Location
    Poland
    Posts
    33,746
    Country
    Poland
    Post Thanks / Like
    Yes I did using some components for the collage.
    Last edited by Wurger; 05-24-2007 at 12:26 PM.




  12. #12
    Senior Member
    Join Date
    Nov 2004
    Posts
    273
    Country
    United Kingdom
    Post Thanks / Like
    Quote Originally Posted by Wurger View Post
    FlyboyJ is right.Look at early WW2 fighters ( Spitfire,Bf-109,).At first, they were equipped with one blade propellers.
    I think you meant to type two-blade: AFAIK only model aircraft have been made with one-blade props. You can balance the weight of a one-blade prop with a counterweight, but you can't balance the thrust - and the forces generated by a powerful engine would probably destroy the propeller shaft.

    For any engine of a given power, there were a number of options facing designers. The more blades you had, the more thrust you could obtain within a given propeller diameter, but the closer the blades were together the less efficient they were, as each blade disturbed the air for the following one. Another variable was the chord of the blades - how wide they were. As with aircraft wings, a long, narrow shape is the most efficient in terms of the maximum thrust for the minimum drag, but a large propeller diameter causes practical problems, not just with undercarriage height but with propeller tip speed approaching the speed of sound, when performance falls off badly.

    Designers of the early WW2 fighters like the Spitfire and the Bf 109 had the problem of coping with engine power which increased steadily through the war, so the props had to be upgraded to cope with the power. There was only a very limited opportunity to increase the prop diameter because of undercarriage length, so they had the choice of adding more blades (the Spit went from 2 to 3, then 4, then 5, then 6 in a contraprop) or making the blades wider (the Germans generally chose this). Why the Germans didn't add more blades has been the subject of much debate, but one of the reasons was probably their reliance on synchronised guns: the more blades you have, the more precise the timing of gun firing has to be to ensure that the projectiles pass between the blades.
    Tony Williams: Military gun and ammunition website

  13. #13
    Senior Member davparlr's Avatar
    Join Date
    Mar 2006
    Location
    Southern California
    Posts
    2,780
    Country
    United States
    Post Thanks / Like
    Quote Originally Posted by Tony Williams View Post
    I think you meant to type two-blade: AFAIK only model aircraft have been made with one-blade props. You can balance the weight of a one-blade prop with a counterweight, but you can't balance the thrust - and the forces generated by a powerful engine would probably destroy the propeller shaft.

    For any engine of a given power, there were a number of options facing designers. The more blades you had, the more thrust you could obtain within a given propeller diameter, but the closer the blades were together the less efficient they were, as each blade disturbed the air for the following one. Another variable was the chord of the blades - how wide they were. As with aircraft wings, a long, narrow shape is the most efficient in terms of the maximum thrust for the minimum drag, but a large propeller diameter causes practical problems, not just with undercarriage height but with propeller tip speed approaching the speed of sound, when performance falls off badly.

    Designers of the early WW2 fighters like the Spitfire and the Bf 109 had the problem of coping with engine power which increased steadily through the war, so the props had to be upgraded to cope with the power. There was only a very limited opportunity to increase the prop diameter because of undercarriage length, so they had the choice of adding more blades (the Spit went from 2 to 3, then 4, then 5, then 6 in a contraprop) or making the blades wider (the Germans generally chose this). Why the Germans didn't add more blades has been the subject of much debate, but one of the reasons was probably their reliance on synchronised guns: the more blades you have, the more precise the timing of gun firing has to be to ensure that the projectiles pass between the blades.
    Good entry. Clear and concise.

  14. #14
    Senior Member renrich's Avatar
    Join Date
    Jan 2007
    Location
    Montrose, Colorado
    Posts
    4,542
    Country
    United States
    Post Thanks / Like
    The F4U1 could turn up only about 2000 HP and had 3 blade prop. The F4U4( the first Corsair with a 4 blade prop) could develop more than 2400 HP. Thus the 4 blader. My brother has a Saratoga 10 or 20 years old. Recently had a complete overhaul and went from a 2 blade to 3 blade prop. Says it climbs a little better but probably no faster but seems a little smoother.

  15. #15
    Siggy Master Wurger's Avatar
    Join Date
    Jun 2005
    Location
    Poland
    Posts
    33,746
    Country
    Poland
    Post Thanks / Like
    Quote Originally Posted by Tony Williams View Post
    I think you meant to type two-blade
    Certainly, yes.Some troubles with the translation into English.




Page 1 of 2 1 2 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198