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Fly-n-hi

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Posts posted by Fly-n-hi

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted · Edited by Fly-n-hi

    One last thing Fly-in-hi, the next time you go for an FAA check ride, just remember that FAA inspector could be me.

    Would you care to give me your name and credentials so I can pass this on to my local FSDO? I'm sure that when I notify them that an "FAA inspector" is threatening me over an internet squabble they will want to know who you are. I could be wrong but I'll bet if I press it something will be done about it. I'm sure the ARC mods wouldn't have a problem giving up your info to the Feds.

    I can assure you, sir, if I decide to take this to the FAA you will never ride in my jumpseat and I will never take any checkrides from you.

    Don't ever threaten me again.

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted · Edited by Fly-n-hi

    I see CRM and conflict resolution are high on your skills too.

    This is what is known as a desperate attempt to get the last word in.

    "How can you tell a pilot has joined the discussion? Don't worry, he'll tell you."

    Like this guy for example:

    ...Try Aerospace Engineer, PP,SEL, MEL...

    The floor is yours. I'm done here.

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted

    I'll listen. I'd like to know which conditions, and why. And I was an aircraft mech. There is still a lot to know and this is something I'm not really knowledgeable in.

    Heck, I can tell you why it happens, at least on the planes I fly, but I'm sure some desk jockey will make a technical or semantic issue out of it.

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted

    Shame that one internet ludmouth internet blowhard can emotionally punch you so hard that you just quit.

    Come on buddy cool off, no insult was meant, just offering a different point of view.

    Usually the guys who dissect and reply to forum posts quote by quote tend to be "emotionally punched" people. Is your's an example of the need to be right or just to save face?

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted

    Let's clear a few up and throw in some controversy.

    More accurately ROLL in the counter clockwise direction. An offset fin can do nothing to stop this.

    100% right on that one.

    If you think about this one for a moment you will realize that this is one that has been taught incorrectly for many years. If you believe in gyroscopic precession then the thrust from the P factor will be realized by the propeller at the 6 O'clock position causing the nose to pitch up. However, the additional THRUST caused by the localized increased airspeed on the right side of the fuselage will cause a yaw to the left because of its reaction on the right face of the vertical fin.

    And the oldest aviation myth. Did you know there is no mention of spiraling slipstream in aviation literature prior to the publishing of "Stick and Rudder"? And since that time almost every aviation textbook quotes Herr Langewiesch's empirical explanation without question. Yet not a SINGLE aviation engineering textbook will provide you with the series of computations to determine how much fin offset is needed for a given horsepower and propeller combination. And if spiraling slipstream were true the aircraft would have an ENORMUS ROLL to the RIGHT due to the same spiraling slipstream that supposedly only causes a yaw to the left. That's because we never bother to look at the effect the spiral would have on the wings and horizontal stabilizers.

    Sorry you hit a raw nerve with me. I've been looking for one paper one textbook to prove spiraling slipstream is real and QUANTIFIED. It's NOT.

    But everyone believes it because it's a story that has been told for so long it must be true.

    Great explanation by the way, just needs some more thought.

    Gee, thanks for the backhanded compliment. I'll bet you're the guy at work everybody hates to talk to.

    If you want to have a friendly debate about whether or not spiraling slipstream is quantifiable or not that's fine. I'm open to discussion and if I'm wrong, heck, I'll admit it. But your tone is very unprofessional.

    I Googled "spiraling slipstream" to get more info on it. The funny thing was that the first link on the list was to a forum in which one guy was arguing against the entire forum. Guess who that one guy was? Yeah...You. Below that link I found links to Brown University and NASA with articles saying that it does exist. I'm pretty sure those guys are smarter than you. Would you like me to post them for you?

    Also, I am fortunate to have been raised in an aviation family being a third generation pilot myself. I have had the privilege of being taught by men who flew during WWII and men who flew commercially with 25,000+ hours of time. They say spiraling slipstream is real. So who should I listen to? Those professional aviators or some loudmouth on the net? Couple that with my 10,000 hrs, including a Gold Seal CFI, and I'd say that the last person qualified to lecture me is some internet blowhard. But I guess every forum has one. Well, apparently there's 2 forums that have one.

    Sorry, you just hit a raw nerve with me. But you clearly wanted an argument so you got it.

    And yes, I know that torque results in "roll." Thanks for making that pedantic correction. Geesh, that's the last time I try to be helpful.

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted

    Now, that is interesting, thank you for explaining Fly-n-hi. I loosely understood the concepts, but your explanation has greatly aided my understanding. That's what I love about this hobby, there is always something new to learn. :)/>

    Anytime!

    I'm actually a CFI and I enjoy teaching this kind of stuff, although I haven't instructed in a while. :(

    Is vertical fin offset or asymmetrical airfoil shape

    in Props

    Posted

    I'm sure there are alot of people reading this right now scratching their heads saying "huh?" I can explain if you're interested.

    Let's assume we have a plane with a propeller that rotates clockwise from the pilots perspective. There are forces that are constantly making the plane want to roll/yaw to the left. These forces are torque, gyroscopic precession, p-factor and spiraling slipstream.

    1. Torque: The torque force is the easiest to understand. As the propeller spins clockwise the plane wants to spin counter clockwise.

    2. Gyroscopic Precession: The propeller basically acts like a large gyroscope in front of the plane. When a force is applied to a gyroscope the resultant motion occurs 90 degrees in the direction of rotation. For example, imagine sitting behind a steering wheel. Assume that steering wheel is spinning clockwise. If you were to push on that wheel at the 12 o'clock position the 3 o'clock position would actually move forward. Google gyroscopic precession for a better explanation.

    Now imagine that steering wheel is the propeller. As you lift the tail (pushing at the 12 o'clock) the plane wants to yaw to the left (motion at the 3 o'clock). On a plane like a tail dragger this is most prominent when lifting the tail off the ground on take-off.

    3. P-factor: Take a tail dragger again. As it rolls down the runway at full power while still on the tail wheel the prop isn't producing even thrust. The blade that is descending is producing more thrust that the blade that is ascending. This makes the plane yaw to the left. The only time the propeller is producing even thrust is when the aircraft is straight and level.

    4. Spiraling slipstream: As the propeller produces thrust the wind tends to spiral aft around the fuselage. This spiraling airflow will push on the left side of the vertical stabilizer and causing the plane to yaw to the left.

    Now, some of the builders decided to attach the vertical stab with a slight left angle to aid in offsetting these forces. Some builders built the vertical stab (which is an airfoil) so that the left side produced more lift...sort of like a wing sticking out of the tail. Other builders put trim tabs on the rudder. And some builders decided that they'd just let the pilots deal with it using their own input on the rudder. But no matter what all the pilots would have to use the rudder to control the roll/yaw.

    How's that?

    1/48th P-51B

    in The Display Case

    Posted

    Thanks Netz for the nice words. I sprayed the props with three coats of future before decalling, so I was shocked when they silvered.

    Nice work!

    I didn't read the whole thing so if this was already suggested I'm sorry but did you use Micro Set? Brushing this on to the area where the decal is to be applied helps eliminate silvering.

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