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        Question Nexstar - new prop changes character

#1 los36 Dec 05, 2012 10:52 PM

Nexstar - new prop changes character
 
My first couple of landings with my Nexstar were a little rough. No damage other than the tips of the stock prop were chipped. I decided to switch from the stock 11x5 to a Master Airscrew wooden 10x8.
Success! Another bouncy landing, yet no propeller damage. The surprise was the way the plane flew. With the stock 11x5, I couldn't fly with the throttle set at more than 50% without the plane shooting for the stars. Today, without any trim or other settings changes to the plane, I flew with the shorter, higher pitched propeller. The plane seemed to fly faster and flatter. It would climb at settings over 75% but not nearly as drastically. The plane seemed better at converting thrust into speed when throttle was applied as opposed to shooting upward. Much more fun!
So, the question part of my post is this: any ideas how a different prop could make this kind of a difference?
Second, if you own a Nexstar, I recommend experimenting with different propellers.
Today was my second session with the plane and I got a solid hour+ in the air. It was dead calm all over town. Of course, where I fly there was a 5mph perpendicular cross wind. Six landings and I can say I was pretty proud of the last three! Thanks, RealFlight!

-Carlos

PS: yes, the airfoils and speed brakes are still in place.

#2 Thermalin Dec 05, 2012 11:12 PM

May be overloading the motor...generally from 11x5 you would go to 10x6...one in increase or decreas in diameter... with one decrease or increase in pitch. Drop diam... increase pitch... increase diam.. decrease pitch. WIth the much greater pitch.... the motor may be lagging a bit on throttle up working harder to get the prop up to speed.

And yes.. one must try different propellers for different performance levels. Hot summer air is much less dense than cold winter air and a prop change is generally required to account for that.

#3 jetmech05 Dec 06, 2012 11:08 AM

Its common for an airplane to climb with throttle on......how did you set your trims? I have always been taught to set trim at around half throttle as this is where you fly....add power climb decrease power descent slightly....

#4 kimchiyuk Dec 06, 2012 04:07 PM

Plus you said the airfoils and speed brakes are still on. These are there to increase lift. That is one reason the plane "shoots for the stars" at full throttle. It's a trainer plane and is meant to be flown at half throttle. I understand you changed the prop due to damage, but before you go playing around with props to get more performance; you should remove the airfoils and speedbrakes. This alone will make a night and day difference. Also, if you fit a prop for performance with them on, you will be playing with props again when you do decide to remove them.

#5 los36 Dec 06, 2012 04:17 PM

Correct, I didn't change it looking for performance. I also realize that the Nexstar isn't designed to fly fast. I stand by my observation that the plane's tendency to climb as the throttle setting increases over 50% is noticeably reduced using the new prop ... and it seems faster.
I posted hoping to understand why. I googled it and found that a general rule is that shorter+more pitch = faster, with less climbing power. Longer+lower pitch = slower, more climbing power.
Moral of the story: google before posting.

#6 kimchiyuk Dec 06, 2012 05:02 PM

Simply put...every plane you ever own you will need to play around with the props. A small change can make a huge difference. Even props of the same size, but different material can give completely different performance. That's the nice thing about 10 to 12 inch props...they are cheap...so for $10 or $15 you can have a whole bag full of props to try.


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