A real Tail Fin

[Mun Moo]

I would really like a real Tail Fin in (basic) Aviation, that is, a triangular part with zero wing surface.  Basic Tail Fins are actually designed as Canards or Wings because they have a lift surface.  If you put a basic Tail Fin on your craft you'll notice the Aerodynamic Overlay Lift go left (at least it did on mine) when the part is perfectly aligned and balanced.  I just want something with zero lift surface so it doesn't screw up my aerodynamics, even if I have to attach an Elevon to it as a rudder.

[Gargamel]

AFAIk, when the basic fin is pointed vertical, it adds no lift to the plane.   Post up some screen shots so we can see what you mean. 

But what you are asking for is a part that does not interact with the environment around it, aside from attachment points.  

Or you could use structural panels, I believe there are triangular ones in the DLC. 

[Guest]

8 hours ago, Mun Moo said:

 If you put a basic Tail Fin on your craft you'll notice the Aerodynamic Overlay Lift go left (at least it did on mine) when the part is perfectly aligned and balanced. 

It shouldn't do that. Pictures?

(Building rudders and tailplanes out of wing segments and elevons is standard procedure though.)

[Dark Lion]

8 hours ago, Mun Moo said:

a real Tail Fin in (basic) Aviation, that is, a triangular part with zero wing surface

This is not a true statement, as history has proven in life, and in KSP simulations. I'm already doubting this is any fault of the game's.

 

8 hours ago, Mun Moo said:

I just want something with zero lift surface so it doesn't screw up my aerodynamics, even if I have to attach an Elevon to it as a rudder.

This doesn't make sense either, because the moment you roll a craft enough to make your rudder any kind of perpendicular to the force of gravity... it generates lift! Stunt planes count on it in knife-flight maneuvers...

 

8 hours ago, Mun Moo said:

If you put a basic Tail Fin on your craft you'll notice the Aerodynamic Overlay Lift go left (at least it did on mine) when the part is perfectly aligned and balanced

This is really best tested on a craft using no other wing parts besides that in question. I've done so and in quite a few different placement ranges. No result so far displaces CoL without using Mk2 parts which have been placed with subtle roll orientation. I can imagine how one might overlook that until you compare CoM + CoL.

I highly recommend setting up shop on Imgur for easy screenshot uploads here on the forums. In order to best learn the err of our ways, we can't be blind to the mistakes we make/made/are making. Don't give up!

[Temeter]

If it goes left, then it's maybe not perfectly vertical?

KSP sometimes had a bug where even slightly diagonal lifting surfaces would be calculated as massive sources of lift the editor.

[Val]

In stock Aerodynamics, all wing surfaces in KSP are completely symmetrical. It doesn't matter which side is up or down.

• They only create lift when they have Angle of Attack.

So if your craft shows the Tail Fin as producing lift to one side, that means the fin is not moving 100% in the direction that the fin is pointing.

A likely cause could be that the landing gear is buckling slightly either from load or because the parts the landing gears are attached to are flexing.

Edited March 22, 2018 by Val
Small clarification and grammar

[Jognt]

Uhm.. if tail fins didn't have any lift/interaction with air then there would be absolutely no point in using them on real and KSP planes.

[DerekL1963]

9 hours ago, Jognt said:

Uhm.. if tail fins didn't have any lift/interaction with air then there would be absolutely no point in using them on real and KSP planes.

Um.. no.  It's quite possible to have zero lift and zero angle of attack and still interact with the air and still be useful - on real planes and in KSP.

[Capt. Hunt]

22 minutes ago, DerekL1963 said:

Um.. no.  It's quite possible to have zero lift and zero angle of attack and still interact with the air and still be useful - on real planes and in KSP.

then it would be useless as a tail fin.  Part of the reason that stabilizers work is that air still flows over them like a wing.  if it didn't, the surface would just create drag.

[qzgy]

1 hour ago, Capt. Hunt said:

then it would be useless as a tail fin.  Part of the reason that stabilizers work is that air still flows over them like a wing.  if it didn't, the surface would just create drag.

So you're saying having a tail fin that auto corrects the aircraft to point in the right direction, making 0 angle of attack and lift most of the time, is not useful?

[Capt. Hunt]

no, I'm saying that it does that by acting like a wing.  No airfoil is truly liftless, the empennage just generates an amount of lift that is negligible compared to that of the wings.

Saying you want a tail fin to work without the aerodynamic effects is like saying you want to make a cake but don't want it baked.

Edited March 26, 2018 by Capt. Hunt

[DerekL1963]

7 hours ago, Capt. Hunt said:

Saying you want a tail fin to work without the aerodynamic effects is like saying you want to make a cake but don't want it baked.

Nobody is asking for a tail fin to work with no aerodynamics.  What we're doing is trying to explain to you that there are more to aerodynamic effects than just lift.

[pandaman]

A perfectly vertical tailfin will generate 'lift', but just in the horizontal axis.  When not flying straight forwards it generates a bit more 'lift' on one side than the other, turning the aircraft slightly, that is how it is able to do its job.

[Capt. Hunt]

3 hours ago, pandaman said:

A perfectly vertical tailfin will generate 'lift', but just in the horizontal axis.  When not flying straight forwards it generates a bit more 'lift' on one side than the other, turning the aircraft slightly, that is how it is able to do its job.

Exactly, that's what I was trying to explain.  Stabilizers work by using lift to right the aircraft if it is not flying level.

[KerrMü]

A good part of the lift produced by a wing in rl is because of the curvature of the wing profile. -> lower pressure above the wing than under the wing. On quite a few rl aicraft designs the stabilizers at the back are "lift neutral" in level flight. For a simple example: The first balsa wood model glider I built as a kid had no stabilizer wing pofile at all. It was just a straight surface. 

In KSP it works a little bit different. Every part that has a lifting property designed into it (for example all wings) change the Center of Lift indicator in the editor. You can work around that with changing the angle of attack of the wing a little in most cases though. 

I would agree, that the ability to change the lift property of a wing on a plane design slightly (not drag aso. just lift) could be useful. But I doubt it will happen so late in the development of the game.

(I´m sorry, this is a complicated subject, and I´m not a native english speaker.) ¯\_(ツ)_/¯

[Kerbart]

I think we’re arguing over definitions. Lift being the force perpendicular to the chord of an airfoil, vs being in the opposite direction of the gravity vector, for instance. And a couple of others.

Don’t sort them out though; it would reduce the entertainment factor of this thread.

[Mun Moo]

Hello.
I seem to be unable to copy/paste PNGs or GIFs.  Copy/paste and drag/drop won't work.  Both Chrome and Edge have the same problem.
Anyways, it's pretty easy to see what I'm talking about: just take a cockpit, mk1 fuel tank, and Wheesley engine and put a Basic Flight Tail Fin on the fuel tank.  Turn on Aerodynamics.  If you align the tail fin exactly with the Aerodynamics circle it will show rightwards "lift".  If you align it so that it doesn't generate sideways lift the tail fin looks skewed left (the aerodynamics bubble touches the right side of the tail at the top and touches the left side of the tail at the bottom.  The offset appears to be very small, say 1-2 degrees.

 

[Snark]

42 minutes ago, Mun Moo said:

I seem to be unable to copy/paste PNGs or GIFs.  Copy/paste and drag/drop won't work.

Correct, because that's not how the forum works.  It won't let you paste any content directly here.  You get a screenshot into your post by linking to it, not pasting it.  Here's what you do:

1. Upload your image to some third-party image sharing site, such as imgur.com.
2. Once it's uploaded there, right-click on the image on its web page and choose "Copy Image Location"
3. Paste that URL into your forum post here.
4. Presto, it gets automagically converted into an in-line image.