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Forum: Rotorheads

6th Aug 2006, 22:02

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

HELOFAN, There really is no rule about ratios...

HELOFAN,
There really is no rule about ratios of rpm, but many times the tail rotor tip speed is the same as the main rotor (when a conventional open tail rotor is used), so the ratio of the rpm is...

Forum: Rotorheads

2nd May 2006, 19:31

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

Stan, your basic premise is just a little off -...

Stan, your basic premise is just a little off - remember, it is not the number of blades that determines the total thrust, it is the solidity. All the virtues you list are attainable by controlling...

Forum: Rotorheads

2nd May 2006, 12:03

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

The stored enegry is proportional to the square...

The stored enegry is proportional to the square of the rpm, so a 3% increase in rpm is actually a 6% increase in energy. It is not enormous, but it truly helps in Cat A and H-V engine cuts. For a...

Forum: Rotorheads

1st May 2006, 15:05

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

slowrotor, No not at all, the more the number...

slowrotor,
No not at all, the more the number of blades, the smaller the humps in lift each create, and the higher the frequency the N/rev vibration is. Both factors make the greater number of...

Forum: Rotorheads

1st May 2006, 14:20

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

widgeon, You seem to think that I say 4 blades...

widgeon,
You seem to think that I say 4 blades is "better" than 5 blades, which is not true, at all! The 5 blades are more expensive, but could be a better mix when all design factors are...

Forum: Rotorheads

1st May 2006, 09:33

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

Very true, and also the cost to make 1 blade is...

Very true, and also the cost to make 1 blade is the sum of a fixed cost (inspection, paperwork, tooling, etc) and a variable cost (materials and labor) so that a 5 bladed head with blades must cost...

Forum: Rotorheads

1st May 2006, 02:47

Replies: 320

EC145

Views: 199,035

Posted By NickLappos

Frankly, there is no more lift or thrust in 5 vs...

Frankly, there is no more lift or thrust in 5 vs 4 or 3 blades, as long as the total solidity of the rotor (total blade area divided by the total disk area) is the same. In other words, 4 skinny...

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