Plane veers to the left. Stumped.

[jsisidore]

All symmetrical, methinks, main chassis at the com, cof slightly ahead of com. When the plane is on the ground as soon as I turn on sas the elevons(yaw) turn left. What does this mean?

[linuxgurugamer]

5 minutes ago, jsisidore said:

All symmetrical, methinks, main chassis at the com, cof slightly ahead of com. When the plane is on the ground as soon as I turn on sas the elevons(yaw) turn left. What does this mean?

Where are you controlling from?

[jsisidore]

Cockpit. Mk3

[jsisidore]

How can I upload it in here so that people can look at it?

[bewing]

34 minutes ago, jsisidore said:

How can I upload it in here so that people can look at it?

A craft file is just a text file. So you copy it into your clipboard, go to pastebin.com, paste it into a page, and post the "raw" URL.

[foamyesque]

Alternatively, if you're using Steam, you can take pictures and upload them through Steam's inbuilt screenshot service.

[Vanamonde]

Hit ctrl-X to cancel any trim you may have inadvertently set, and make sure your joystick is centered. Those are the two most common causes on this sort of thing in flight. If it's happening while on the ground, the weight of the craft may be causing it to sag and flex to the point that the gear is no longer vertical to the ground. 

[jsisidore]

http://pastebin.com/dGbSWyEi here's the link

6 hours ago, Vanamonde said:

If it's happening while on the ground, the weight of the craft may be causing it to sag and flex to the point that the gear is no longer vertical to the ground. 

For that to happen the sagging has to be insane, unless something changed with 1.2. Anyway the gear looks straight!

[Daveroski]

Look at the autostrut visualisation.

If you have more than one 'heaviest part' then sometimes the autostrut connects in an asymetrical manner causing the veering you describe.

It can cause some craft to rotate wile idle.

SAS tries but fails to compensate.

 

[jsisidore]

8 minutes ago, Daveroski said:

Look at the autostrut visualisation.

If you have more than one 'heaviest part' then sometimes the autostrut connects in an asymetrical manner causing the veering you describe.

It can cause some craft to rotate wile idle.

SAS tries but fails to compensate.

 

Sorry. I don't understand.

[Daveroski]

5 minutes ago, jsisidore said:

Sorry. I don't understand.

In the Debug window (Alt - f12 Windows) look for 'physics' and click that. Put a tick in the 'visualise autostuts' and then close the window.

 

[jsisidore]

Ok. The autostruts(new word to me) are symmetrical.

Can you look at it? It is either an obvious mistake I made somewhere, or an obvious bug!

http://pastebin.com/dGbSWyEi

 

 

[bewing]

Hmmmm. I see you are doing this in ver 1.1.3. So no autostruts or anything like that.

When I try it in ver 1.2, the plane blows the hell up from clipping. So I can't really judge the SAS behavior of the little pieces that are left bouncing on the grass.

But I don't see any yaw control except the reaction wheels in the cockpits.

[jsisidore]

15 minutes ago, bewing said:

Hmmmm. I see you are doing this in ver 1.1.3. So no autostruts or anything like that.

When I try it in ver 1.2, the plane blows the hell up from clipping. So I can't really judge the SAS behavior of the little pieces that are left bouncing on the grass.

But I don't see any yaw control except the reaction wheels in the cockpits.

That is weird. The version is 1.2.0.1586 and the plane is quite stable.

I  might have solved the issue a little, after taking off the second set of main gears the veering has subsided, like 20%, ironically the gears are not big enough and this gives the wings a lot of flex. I know I need more gears for touchdown.

There's the struts. Look symmetrical.

This is the mk2 ssto I landed on Dune which was very hard to do. But upping my game to mk3 gives me headaches, its sheer heaviness seems inappropriate for the task.

Edited November 29, 2016 by jsisidore

[Daveroski]

 

I am running 1.2.1 and of course the ship blew up on the runway.

So I turned on unbreakable joints and managed to launch it in one lump.

and after a few alterations even got it to fly.

It needs a lot more SAS as it wants to nose down until it gets up to speed.

I moved the wings back to get the COL back behind the COM as it wanted to do a flip as soon as it left the runway.

I added nosecones to the tailends of all the engines to get rid of the drag from the open nodes from the engines (you can see it if you look at the top of your Nivs.) I changed your air intakes and put small round nosecones on in front.

I didn't notice anything wrong with the elevons. They all reacted as expected.

 

 

[jsisidore]

Sorry wrong design, this is the old version. This won't escape Kerbin's gravity as it needs more nerv engines.

This is definitely it:

http://pastebin.com/VjHM7Zb4

Edited November 29, 2016 by jsisidore

[Tex_NL]

3 hours ago, jsisidore said:

That is weird. The version is 1.2.0.1586 and the plane is quite stable.

I  might have solved the issue a little, after taking off the second set of main gears the veering has subsided, like 20%, ironically the gears are not big enough and this gives the wings a lot of flex. I know I need more gears for touchdown.

There's the struts. Look symmetrical.

[PicSnip]

This is the mk2 ssto I landed on Dune which was very hard to do. But upping my game to mk3 gives me headaches, its sheer heaviness seems inappropriate for the task.

[PicSnip]

Every time an issue like this comes up I wonder why I even bothered to start a FAQ.

And now to your question.
It doesn't surprise me one bit that this design has issues on the runway. This thing is guaranteed to be 'wheelbarrowing'.
First issue lies with  the control surfaces being too close to the rear landing gear. Pushing the tail down will proof difficult. The second issue also comes from the landing gear. The rear landing gear is way too far backwards. It should be just behind the CoG. As an added bonus moving the rear wheels forward will make it much easier to push the tail down.
Those two issues combined will result in 'wheelbarrowing'. At speed you will start to generate lift. But since you are unable to push the tail down the lift will start to raise it. And since the only wheel left on the ground will be the nose gear the plane will tip over and steer off the runway.
(The wheels don't actually have to leave the ground for this to happen. Even just partially taking the weight off a wheel will reduce friction causing it to steer.)

Edited November 29, 2016 by Tex_NL

[jsisidore]

1 hour ago, Tex_NL said:

Every time an issue like this comes up I wonder why I even bothered to start a FAQ.

And now to your question.
It doesn't surprise me one bit that this design has issues on the runway. This thing is guaranteed to be 'wheelbarrowing'.
First issue lies with  the control surfaces being too close to the rear landing gear. Pushing the tail down will proof difficult. The second issue also comes from the landing gear. The rear landing gear is way too far backwards. It should be just behind the CoG. As an added bonus moving the rear wheels forward will make it much easier to push the tail down.
Those two issues combined will result in 'wheelbarrowing'. At speed you will start to generate lift. But since you are unable to push the tail down the lift will start to raise it. And since the only wheel left on the ground will be the nose gear the plane will tip over and steer off the runway.
(The wheels don't actually have to leave the ground for this to happen. Even just partially taking the weight off a wheel will reduce friction causing it to steer.)

Thank you for your input, please refer to my last post in this thread for the actual design, the design you're describing is one of the first concepts I've made, too heavy, too wobbly and not powerful enough.

This is the newest one, please give it a go:

http://pastebin.com/VjHM7Zb4

Edited November 29, 2016 by jsisidore
grammar

[HalcyonSon]

As Tex_NL alluded to, WET (full fuel) and DRY (zero fuel) screenshots showing the CoM, CoL, and CoT in the Hangar are helpful in diagnosing takeoff and landing problems.  If a plane lifts off at all, a variety of in-flight problems can be prevented by varying fuel load in the Hangar as it would be used in-flight and checking the CoM and CoL.

[Tex_NL]

54 minutes ago, jsisidore said:

Thank you for your input, please refer to my last post in this thread for the actual design, the design you're describing is one of the first concepts I've made, too heavy, too wobbly and not powerful enough.

This is the newest one, please give it a go:

http://pastebin.com/VjHM7Zb4

Is that the one in @Daveroski's images? Juts by looking at the pictures that one too suffers from quite a few stability issues:
It doesn't have a vertical stabilizer. It's very short compared to a very wide weight distribution. The wheelbase is very narrow. And just as with the first plane the control surfaces are again very close behind the landing gear.

[Daveroski]

Despite being lumpy and camel like in it's gait on the ground it does lift of rather easily.

I had to stick a big SAS behind your huge tank of Monoprop in the boot and a smaller one behind the Shielded Docking port on the front.
I also moved all the wings back a bit so that your COL was behind your COM. As you drain fuel from that big front tank your COM falls backward. If you use that fuel and then come back into an atmosphere you will be wondering why it is flipping oven and over on the way down. Having fuel up front is good.
I think your ratio of Nirvs to Rapiers is a bit too high to go hypersonic in this craft. I would lose a couple of Nirvs on each wing and replace them with rapiers making it 8 Rapiers to 4 Nirvs. Then you might be able to fill up those mid tanks on each wing so the extra Rapiers could use the fuel.

Oh.. and I found it took off better if I disabled the steering in the rear and front wheels.

 

2 minutes ago, Tex_NL said:

Is that the one in @Daveroski's images? Juts by looking at the pictures that one too suffers from quite a few stability issues:
It doesn't have a vertical stabilizer. It's very short compared to a very wide weight distribution. The wheelbase is very narrow. And just as with the first plane the control surfaces are again very close behind the landing gear.

I say.. do try and keep up.

 

[Tex_NL]

What. Wait. That big Mk3 tank is monoprop? What a waste. I have no idea what you're planning but I doubt would need more than just a fraction of it.
Add a few roundified or cilindrified monoprop tanks and substitute the big tank for LFO. The plane will weigh nearly the same but has a LOT more dV. Nerva's are VERY heavy. Adding more will not increase effectiveness. Instead it hurts effectiveness badly. Use as few as possible to safe weight, or use a more powerful but lighter one.

P.S.
Actually adding some equipment to use the monoprop could be beneficial.

Edited November 29, 2016 by Tex_NL

[Daveroski]

4 minutes ago, Tex_NL said:

What. Wait. That big Mk3 tank is monoprop? What a waste. I have no idea what you're planning but I doubt would need more than just a fraction of it.
Add a few roundified or cilindrified monoprop tanks and substitute the big tank for LFO. The plane will weigh nearly the same but has a LOT more dV. Nerva's are VERY heavy. Adding more will not increase effectiveness. Instead it hurts effectiveness badly. Use as few as possible to safe weight, or use a more powerful but lighter one.

P.S.
Actually adding some equipment to use the monoprop could be beneficial.

Sorry old boy but you are adrift again.

The monoprop is 'in the boot'

I clearly suggested losing Nirvs and replacing them with Rapiers.

[Tex_NL]

7 minutes ago, Daveroski said:

Sorry old boy but you are adrift again.

The monoprop is 'in the boot'

I clearly suggested losing Nirvs and replacing them with Rapiers.

OK, then I misread. I read you stuck an SAS reaction wheel in the boot. Behind the big monoprop tank. As in: the boot is behind the big tank.
And since there is a cargo bay directly behind a big tank ....

And yes. I did read you also suggested loosing the NERVA's. I just mentioned them to make clear more in this case is less. Adding more NERVA's is counter productive.

[Daveroski]

 

Oh my.. I almost forgot.. The Elevons.

They are trying to turn the craft because the craft is moving slowly down the runway.
The runway cambers slightly towards the hangar making your craft want to go right. Your SAS is very weak and so has to pile it on a bit to make a dent. SAS also controls the elevons in an effort to keep your craft pointing the same way.

So when your craft is first loaded it drops down to the ground. You see in your navball that the craft is 'aware' of its orientation.

If the navball hasn't settled down and you turn on SAS it can over compensate with the elevons.

It is better to quickly turn on the brakes and let everything settle down just before you launch. Hardly anyone does this though including myself and I am fully aware of the problem.

18 hours ago, jsisidore said:

All symmetrical, methinks, main chassis at the com, cof slightly ahead of com. When the plane is on the ground as soon as I turn on sas the elevons(yaw) turn left. What does this mean?