School Me On Air Density and Density Altitude

[reality]

Man 10% humidity..  - Around here [great lakes] the BEST you could hope for is 30 to 50%


And does 50% humidity mean the air going in is 50% water?

[Steve Wood]

26% and partly cloudy here at the moment.  On a hot day, it goes on down.

[Scoobum]

34 percent at 6pm when I got there and went up to 54 percent at 9pm when I left.

[good2win22]

Man 10% humidity..  - Around here [great lakes] the BEST you could hope for is 30 to 50%


And does 50% humidity mean the air going in is 50% water?

No.  50% humidity is relative to the air temperature and the air pressure. So at any given temperature and pressure the air can only hold so much water vapor. 70 F temps at 29.92 will hold x amount of water vapor. 70 F temps at 30.02 will hold less x amount of water vapor. 70 F temp at 29.82 will hold significantly more x amount of water vapor.


Know this, if humidity is 100%, you will either have fog or its raining. I like to watch the dew point spread to see if visibility will be an issue on night flights.

[Steve Wood]

pretty soon we will be into dew point and what it has to do with tornado prediction

[Scoobum]

Maybe you guys could explain the thunderstorms we've had damn near daily this year.

[reality]

 This subject begs answers to a number of questions.


In terms of aerodynamics how much hp [time, speed] is lost in a TR 
running 11.0 between 0% and 100% humidity?


In terms of molecules of air in say 1 rpm how many are lost 0% to 100% humidity?


What is the difference between 100% humidity and being at the bottom of a lake?


Answers not burning a hole in my brain or anything I just find it interesting.

[nocooler]

http://www.dragtimes.com/da-density-altitude-calculator.php

There is a "correction" calculator for density altitude. You can play with the humidity, barometric pressure, temp, and elevation - check it out. With the custom d/a you could then put that with what ever et range you want to test.

Is it 100% accurate? Probably not - but it gives you an idea.
 

[good2win22]

This subject begs answers to a number of questions.


In terms of aerodynamics how much hp [time, speed] is lost in a TR 
running 11.0 between 0% and 100% humidity?


In terms of molecules of air in say 1 rpm how many are lost 0% to 100% humidity?


What is the difference between 100% humidity and being at the bottom of a lake?


Answers not burning a hole in my brain or anything I just find it interesting.

I like the way your mind works. Thinking outside the box.


As I kid, I received a book titled, Tell me why.  Had an assload of useful information in it. Like why is the sky blue and why does the ocean have salt water. Still have the book and still refer to it. First printed in 1964

[Scoobum]

This subject begs answers to a number of questions.


In terms of aerodynamics how much hp [time, speed] is lost in a TR 
running 11.0 between 0% and 100% humidity?


In terms of molecules of air in say 1 rpm how many are lost 0% to 100% humidity?


What is the difference between 100% humidity and being at the bottom of a lake?


Answers not burning a hole in my brain or anything I just find it interesting.

Ron...this doesn't answer your question. Here's some data. 2 weeks ago the temp and humidity were pretty damn close to this past Friday. 2 weeks ago the 02's were 760 at the traps. Friday nite, seeing the temp and humidity were the same as 2 weeks ago I added 5 percent high gear fuel to cover my ass...so I thot. The air was far 'cleaner' than what I thot given the temp/humidity I had...and the 02's came in at 737 when the knock gauge went off and I lifted. I've based my tuning on temp/humidity. I have a lot to learn about tuning in regards to DA, AD and grains of water.

[good2win22]

Reading a performance chart in the Bell manual.  Says engine performance can decrease by 3-4% from 20-80% humidity.  Have a separate performance chart for high humidity.