Yo!! Trainfan..
Got a question for you on props.I have a two SS props - same pitch, same diameter. One is a four
blade and one is a three blade. Same manufacturer. The four blade has a cup or more of a twist in the blades than the
three blade. Is there a reason for that? |
Short
Jun 15
|
| following well considered thoughts to the readers of rec.boats: |
Gene
Jun 15
|
| following well considered thoughts to the readers of rec.boats: Oh.... cooool..... check your mail.....
|
Gene
Jun 15
|
| Very cool. Just ordered one. Let's just keep this to ourselves shall we? Don't want the riff raff to join in on the fun. |
Short
Jun 15
|
| There is a purpose and reason for everything, grasshopper. |
HK
Jun 15
|
| It is part of the design to reach the intended pitch. If you look at both props, you should be able to see that the 3 blade
probably has a greater rake angle where the blades meet the root or hub,
and the trailing edge is noticeably cupped. This design is to reduce
ventilation or blowout at higher trim angles or jack plate settings, and
as a bow lift enhancement at speed. The 4 blade is cupped along the rake to enhance the bow-lifting feature
desired from that design. The 4 blade may have a slightly thinner blade
cross-section too, for a given application. Each blade is only loaded
w/ 75% of the power compared to a 3 blade situation. Rob |
trainfan1
Jun 15
|
| Interesting. I need to learn a lot more about this. Thanks. |
Short
Jun 15
|
| Cupping is a way of increasing the effective pitch. If you have
enough torque to spin them, the cupped props should give you a bit
more speed at the same RPM. |
Wayne.B
Jun 15
|
