How can I help with aerobatics on my fighter?

[SlabGizor117]

I saw a gif on the reddit one time of someone who did a backflip taking off.  It was probably reaction wheels, but I wanted to try it with my own fighter.  I have the CoL really well balanced, but the thrust vectoring can't overpower the wings enough to do a flip.  It either noses straight up and stalls, or goes backwards and cancels it's speed, again stalling the craft.  I should add, though, with the CoL that it is still a good bit behind the CoM, but it's right up against the CoM on empty tanks.  So, should I do some fuel line trickery to help the CoM moving back as the fuel goes down?  Or is there something else I could do?  Another thought I had was that there was just a lot of drag because it had big wings, so it was stifling my momentum when I would nose up.  What do you think?

EDIT: I was thinking of the wrong craft, the CoL is right behind the CoM.  So what else could I do to make the thrust vectoring more effective?

Edited January 29, 2016 by SlabGizor117

[Snark]

Suggest posting a screenshot-- it's much easier for folks to give concrete what's-wrong-with-this-craft suggestions if they can see it.

[pincushionman]

Truly aerobatic craft have the neutral center of lift (or whatever it actually is in real life) as far forward as you can get it without losing control (some planes like the F-16 are actually longitudinally unstable for this exact purpose). Ideally, use a single fuel tank centered as close to the center of mass as you can get it so it won't vary through the flight, and nail that CoL marker right on top of it, too. Then give yourself loads of pitch authority.

But Snark is right - a picture is worth a thousand words.

[WhiteKnuckle]

If you're stalling when you pull up then I'd start by adding moar thrust! But seriously, at low airspeeds control surfaces just wont have the authority to pull you around, so you ether need to go faster before you pull up, or have a better TWR so you don't loose as much speed in the climb. A thrust vectoring engine has the added benefit of giving you another method of control, but placement matters, if the engine(s) are close to the CoM their vectoring wont have as much effect as it would if they were all the way at the back of the plane.

Or you can just cheat...

(does a backflip on takeoff)

[SlabGizor117]

Ok, didn't think that would affect much since I had described everything I thought relevant, but I'll do that when I'm done with school today.. If I can remember
 

[WhiteKnuckle]

2 minutes ago, SlabGizor117 said:

Ok, didn't think that would affect much since I had described everything I thought relevant, but I'll do that when I'm done with school today.. If I can remember
 

All you told us was that the CoL is behind the CoM and that it has "big wings".

We don't know what type of engines you're using or where you've placed them, what your pitch control surfaces look like and where you've placed them, how big your wings are and how you've placed them... ect.

A pic really will help.

Edit: another thing we need to know, are you using FAR?

Edited January 29, 2016 by WhiteKnuckle

[SlabGizor117]

No.  I'll work on pics now.

EDIT: Here's the album.

http://imgur.com/a/UZWgm

Whaddaya think of the design, by the way? I'm proud of it.

Edited January 30, 2016 by SlabGizor117

[Rocket In My Pocket]

1 hour ago, SlabGizor117 said:

No.  I'll work on pics now.

The .craft file would be even better!

[SlabGizor117]

Yeah, it would, but I have no dropbox or mediafire account, and my parents are kinda strict about me making email accounts, I already get KSP forum spam because I accidentally subscribed to the BDArmory thread.  Like, 20 emails a day... How do I unsubscribe?? XD

I added pics in the last post though.

Edited January 30, 2016 by SlabGizor117

[Rocket In My Pocket]

13 hours ago, SlabGizor117 said:

Yeah, it would, but I have no dropbox or mediafire account, and my parents are kinda strict about me making email accounts, I already get KSP forum spam because I accidentally subscribed to the BDArmory thread.  Like, 20 emails a day... How do I unsubscribe?? XD

I added pics in the last post though.

Pretty good looking bird! 

As far as the question at hand, I'd wager it's just too darn heavy. Any plane I've ever built that was capable of really high G stunts like loops and backflips off the runway was always small, light, with lots of power. As far as the air intake issue it's really hard to say without flying it and watching the numbers, but it could very well be part of your problem.

The wings are also in the shoulder/high position which is good for stability (and also carrying missiles which is why I assume you've used them), but low wings tend to give better performance. Some Wikipedia stuff about wings in spoiler. 

Spoiler

Wing position[edit]

Besides the general variations in wing configuration such a tail position and use of bracing, the main distinction between types of monoplane is how high up the wings are mounted in relation to the fuselage.

Low wing[edit]

 

Low wing on a Curtiss P-40

A low wing is one which is close to the bottom of the fuselage.

Placing the wing low down frees up the central fuselage from the wing spar carry-through structure and also allows good visibility upwards. By reducing pendulum stability it makes the aircraft more manoeuvrable. It also allows a lighter structure because the fuselage sides carry no additional loads and the main undercarriage legs can be made shorter. It is common on jet airliners.^{[citation needed]}

One problem with the low wing position is that on landing the ground effect is especially strong, giving the plane a tendency to float a long way before it can touch down.^[2][3]

Mid wing[edit]

 

Mid wing on a de Havilland VampireT11.

A mid wing is mounted mid-way up the fuselage. It is aerodynamically the cleanest and most balanced, but the carry-through spar structure can reduce the useful fuselage volume near its centre of gravity, where space is often in most demand. It is common on high-performance types such as sailplanes.^{[citation needed]}

Shoulder wing[edit]

 

Shoulder wing on an ARV Super2.

A shoulder wing is mounted between the midpoint and the top of the fuselage. It is sometimes classed as a type of high wing.^{[citation needed]}

Placing the wing above the midpoint increases the useful volume beneath and also allows good visibility downwards. It provides pendulum stability by placing the centre of gravity below the centre of pressure. It also gives increased ground clearance for the propellers of multi-engined aircraft, for underwing stores and for ground handling. Many light transport aircraft have shoulder or high wings.^{[citation needed]}

High wing[edit]

 

High wing on a de Havilland Canada Dash 8.

A high wing has its upper surface close to or above the top of the fuselage. It has all the advantages and disadvantages of the shoulder wing, and even more so.^{[citation needed]}

On light aircraft the wing is sometimes located on top of the pilot's cabin.^{[citation needed]}

Parasol wing[edit]

 

Parasol wing on a Pietenpol Air Camper.

A parasol wing is a high wing which forms a separate structure above the fuselage and is not directly attached to it, with structural support being provided by either several cabane struts or a single wider pylon.^[4] Additional bracing has to be provided by underwing struts extending either side of the fuselage.

The supports and bracing create extra drag so the parasol wing is not often used. Compared to a biplane it has less bracing and lower drag, and the parasol wing was popular only during the inter-war transition years between biplanes and monoplanes.^{[citation needed]}

 

 

[SlabGizor117]

Cool, thanks.  I figured weight was the problem anyways, which kinda makes sense, how most maneuverable planes are made small.  I guess I'll just make it a heavy fighter.  I actually didn't know about vertical placement of the CoL, only the pendulum effect.  I didn't know low wings increased maneuverability, I just put high wings for the look I wanted.  

After finding that youtuber,SoundWave,

(http://forum.kerbalspaceprogram.com/index.php?/topic/130815-this-isnt-my-channel-but-this-guy-is-amazing)

I started putting more detail in my planes.  I've been going back through my planes trying to make them look better, so I might post a few later at the Spacecraft Exchange.