tetryds

Official FAR Craft Repository

1073 posts in this topic

48 minutes ago, FourGreenFields said:

Or just trim the plane (iIrc alt + qweasd, and alt + x removes trim).

Never tried that, does that save, or do you have to do that every time, on every launch?

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1 minute ago, Cratzz said:

Never tried that, does that save, or do you have to do that every time, on every launch?

I don't know a way to save trim per-craft, but this makes it a whole lot easier to set in flight:

 

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7 hours ago, Cratzz said:

Never tried that, does that save, or do you have to do that every time, on every launch?

I'm quite sure it resets prior to every launch. You could just angle the control surfaces for a "saved" trim though (allthough it wouldn't change thrust vectoring).

Or maybe you could write a macro to set trim at spawn (and the rest of the routine, like lowering flaps to takeoff position, etc.). Maybe it'd even be possible to save the trim settings as part of the plane file (as comment?), and have the macro read it.

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10 hours ago, FourGreenFields said:

I'm quite sure it resets prior to every launch. You could just angle the control surfaces for a "saved" trim though (allthough it wouldn't change thrust vectoring).

Or maybe you could write a macro to set trim at spawn (and the rest of the routine, like lowering flaps to takeoff position, etc.). Maybe it'd even be possible to save the trim settings as part of the plane file (as comment?), and have the macro read it.

Yea, it dosen't seem to stick. Dosen't matter, with some wing adjustments and ballast she's now wobble-free at Mach 2+ Success! :D

F14 Mk.2

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Posted (edited)

On 4/23/2017 at 2:20 PM, FourGreenFields said:

Am I right to assume it only reaches critical AoA due to thrust vectoring?

*snip*

Not really. There is only a *tiny* bit of thrust vectoring in the pitch axis (about five degrees maximum) which might be pushing the craft to critical AoAs. I usually don't use thrust vectoring on a lot of my aircraft since I'm not very interested in making supermanuverable planes (I like building planes like they're from the 50's to the 80's), so I might also lock the vectoring on the plane I'm working on.

On the sideslip, I never use the rudder while turning unless it's some sub par 'light' fighters I've made early in my save. Though after adding variable camber wings (more on that later), I did seem to notice a slideslip effect during turning where the nose yaws upwards about ~3-4 degrees. It could be different deflections on the flaps/slats, but I would need to dive into the FAR code and make it show current deflection on the right click menu.

On the 1.2 version of FAR (Not sure if you're asking me specifically), I'm not using it. I bit the bullet and decided to stay with 1.1.3 instead. I know there's a pull on the FAR github page, but I have no idea how to get either the source or the compiled libraries. I want to ask but I'll probably be made fun of and shamed forever.

On 4/23/2017 at 4:32 PM, Nixod321 said:

Generally the modern fast-mover designs like the su-27 and f-14 your aircraft resembles do not have good low speed handling due to the high wing loading (15t/m² is crazy high, even the biggest fighter jets have about 500kg/m2 with full fuel) and the drag inducing vortices formed at high AoA. The swept wings your design exhibits can also induce asymmetric stalls due to tip stalling.

*very interesting and useful things that you should definitely read yourself*

Actually, It seems like I missed a decimal point. It's actually 0.15t/m² with a mass of ~10.51t and ~69.10m² of reference wing area. I keep an excel file with all the masses and wing areas of all my planes and it calculates the wing loadings for me. The most lightly loaded plane I have has a wing loading of 0.12t/m² and effortlessly turns around and shreds everything with its two 20mm guns.

Wing rakes, fences and vortex generators, while very good in real life, don't look like they'll work as effectively in FAR. I don't think FAR models wind vortices yet (If an update adds that, I would kill to get it, it would literally change everything). I added both leading edge slats and AoA activated flaps on the wings and made them taper off a bit more at the end. I feel like the tapering of the wings did very well to improve turn characteristics overall, but I can't solidly confirm that. Though the variable camber wing (made possible by slats/flaps) were a different story. I don't know if adding variable camber either restricted the plane from pitching up into its critical AoA or increased wing lift, but it definitely did something that stopped the plane from pitching up into its doom. 

Besides the odd 'slideslip' effect I mentioned earlier, the variable camber did it. I've tried AoA activated leading edge slats before, but I never tweaked them enough to make them really work until now. Here's the (partially) variable camber in flight. I also added variable camber to the wings of that 0.12t/m² I mentioned, and it added a lot more turn stability while keeping roughly the same turn (rate?). Here's a photo of it.

Thanks to both of you for your suggestions and ideas!

PS: Where do you get the transparent cockpits?

Edited by CrayzeeMonkey

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Posted (edited)

On 4/24/2017 at 5:16 AM, Cratzz said:

Jebediah complained about too much positive AoI, making his arms hurt after hammering the stick to keep it from going nose up at certain speeds. So it needs some work. But it's my first craft with variable wings, and IR. So much fun! Wobbles pretty bad though, but im working on building a sturdier variant that works more like the real thing below. Pics when!

hwIm8.gif

Love the design so far Cratzz.

I recently posted a video of the variable geometry wing setup I used for my T-4MS. It's very similar to the picture you linked of the real F-14 wing. I also posted an explanation on the Infernal Robotics Rework thread if you're interested.

 

 

Edited by Elmetian
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I have built some Variable Geometry wings before, but not like Mr. Elmetian.   His design is far better than my own. 

SOMdLcm.jpg

G6sv4dm.jpg

jLmA5DG.jpg

ePBMxbW.jpg

But I am also a huge fan of the leading edge slats or variable camber leading edge.  I use those on most of my current designs to limit wing stall when possible.

KgwD7cL.jpg

Leading edges on that only move a max of 6 deg. 

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On 2017-04-25 at 0:35 PM, Elmetian said:

Love the design so far Cratzz.

I recently posted a video of the variable geometry wing setup I used for my T-4MS. It's very similar to the picture you linked of the real F-14 wing. I also posted an explanation on the Infernal Robotics Rework thread if you're interested.
 

Thanks Elmetian! Yea i shamefully tried to copy that and give it a go, but some IR parts don't work as intended here, but i get the idea!

Love the bomber :cool: Btw what mod let's you do a camera fly-by? And also, i didn't think there were any paint-mods working with 1.2?

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Posted (edited)

Okay, I think my gear are messed up but I'm not sure how to fix it, and it could also be any aircraft problem I don't know. This aircraft flies great but it can't take off.

basic craft setup:

HVwYmVrm.png

As it is shown in the above image, when I start on the Tier 2 runway, set flaps to 2 and just throttle up to full, at around 20m/s it spins out to the left. This is what the FAR derivatives show for this:

AVMby3zm.png

So I'm thinking that maybe the yaw is enough to cause a problem. I found that if I increase the size of the tail fin by just 4%, the red yaw derivatives completely go away - I increased the Mach Number incrementally by 0.01 from 0.01 all the way to 0.3 - no red yaw derivatives. That didn't make any difference. Could it be something in the pitch derivatives?

I tried to play around with different gear configurations:

5zZjoimm.png

wLDZ5adm.png

Each of the above have the wheels the same mass and in the same ground contact positions as the early fixed gear. But in all cases even when I adjusted things to negate any red yaw derivatives the aircraft would still spin out - although in the last configuration it made it to 30m/s before the tail wheel left the ground (as proper) but then it spun out closer to 40m/s.

Really hoping it's just some spring/damper adjustments that are needed but playing around with those didn't help much either.

I've uploaded the base model shown at the top of the post to KerbalX if anyone wants to take a look at it. Thanks!

Additional note that it's pretty much only the swerving that is the problem, if it could stay straight up to ~50m/s it can actually take off. Also I tested it with only the mods needed to get it to load & fly with FAR

Edited by Drew Kerman

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49 minutes ago, Drew Kerman said:

Okay, I think my gear are messed up but I'm not sure how to fix it, and it could also be any aircraft problem I don't know. This aircraft flies great but it can't take off.

basic craft setup:

HVwYmVrm.png

As it is shown in the above image, when I start on the Tier 2 runway, set flaps to 2 and just throttle up to full, at around 20m/s it spins out to the left. This is what the FAR derivatives show for this:

AVMby3zm.png

So I'm thinking that maybe the yaw is enough to cause a problem. I found that if I increase the size of the tail fin by just 4%, the red yaw derivatives completely go away - I increased the Mach Number incrementally by 0.01 from 0.01 all the way to 0.3 - no red yaw derivatives. That didn't make any difference. Could it be something in the pitch derivatives?

I tried to play around with different gear configurations:

5zZjoimm.png

wLDZ5adm.png

Each of the above have the wheels the same mass and in the same ground contact positions as the early fixed gear. But in all cases even when I adjusted things to negate any red yaw derivatives the aircraft would still spin out - although in the last configuration it made it to 30m/s before the tail wheel left the ground (as proper) but then it spun out closer to 40m/s.

Really hoping it's just some spring/damper adjustments that are needed but playing around with those didn't help much either.

I've uploaded the base model shown at the top of the post to KerbalX if anyone wants to take a look at it. Thanks!

Additional note that it's pretty much only the swerving that is the problem, if it could stay straight up to ~50m/s it can actually take off. Also I tested it with only the mods needed to get it to load & fly with FAR

Where's the CoM? Should be slightly behind your main gear, but only slightly. If that's still possible, try to reduce the drag of the main gear, and increase that of the tail wheel. And make sure the gear doesn't flex.

Also worth a try to pull during takeoff run, to increase pressure on the tail wheel.

That being said, are you sure the thing will lift off at 50m/s at the AoA it has when sitting on the runway? I don't consider it impossible, but AoA seems relatively low - might still be sufficient if the craft is light though.

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1 hour ago, Drew Kerman said:

Okay, I think my gear are messed up but I'm not sure how to fix it, and it could also be any aircraft problem I don't know. This aircraft flies great but it can't take off.

*snip*

Gear in 1.1.3 is bugged. What is happening is the early wheels are so weak that even the lightest aircraft will cause them to build up "stress" and lose lateral traction. You can turn off auto friction control and turn it all the way up to max and it will solve the problem, but if you try to steer at all you will spin out wildly. The fixed landing gear do not work at all and cannot be used. The first retractable wheel only works for very small craft. The only way I found to fix it is to either modify the wheels' files and quadruple the stress tolerances, or cheat and get the later models. Both will solve the problem.

If you are not running 1.1.3, here are some fixes that I know work from experience:

1) Go into the rotate function in the editor, turn on angle snapping, and drag the rotate wheel a little bit in both planes. The gear should still face the same way, though. This forces the gear to snap exactly into alignment (you should see a little movement when you first rotate the wheel), and may solve your swerving issue.

2) Attach a strut to the gear pieces from a central fuselage piece.

3) make sure your gear are attached as firmly as possible, preferably to a fuselage piece. If the gear flex and change orientation even a little bit it can throw the aircraft into a spin.

Beyond that, I can't help. Some designs just do that with no indication as to why and can't be fixed. If you still can't get it to work, just make a new plane.

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7 hours ago, FourGreenFields said:

Where's the CoM? Should be slightly behind your main gear, but only slightly. If that's still possible, try to reduce the drag of the main gear, and increase that of the tail wheel. And make sure the gear doesn't flex

this is all as good as can be already

7 hours ago, FourGreenFields said:

Also worth a try to pull during takeoff run, to increase pressure on the tail wheel

yup, helps a bit but overall ineffective

7 hours ago, FourGreenFields said:

That being said, are you sure the thing will lift off at 50m/s at the AoA it has when sitting on the runway?

Yes. it's a tail dragger, so the rear wheel comes off the ground first, then you nose down to level and lift off from there. At least, that's what you're supposed to be able to do :P My tail wheel comes up but then it's spinny time

7 hours ago, Nixod321 said:

You can turn off auto friction control and turn it all the way up to max and it will solve the problem

Nope :(

mRdos67m.png

I had the PAW pinned and the entire time the plane was flipping out the wheel stress bars were all zero. I also turned on rigid attachment.

7 hours ago, Nixod321 said:

If you are not running 1.1.3,

Oh, I forgot to mention I'm on v1.2.2 - are the fixed gear still salvageable?

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8 hours ago, Nixod321 said:

Gear in 1.1.3 is bugged. What is happening is the early wheels are so weak that even the lightest aircraft will cause them to build up "stress" and lose lateral traction. You can turn off auto friction control and turn it all the way up to max and it will solve the problem, but if you try to steer at all you will spin out wildly. The fixed landing gear do not work at all and cannot be used. The first retractable wheel only works for very small craft. The only way I found to fix it is to either modify the wheels' files and quadruple the stress tolerances, or cheat and get the later models. Both will solve the problem.

If you are not running 1.1.3, here are some fixes that I know work from experience:

1) Go into the rotate function in the editor, turn on angle snapping, and drag the rotate wheel a little bit in both planes. The gear should still face the same way, though. This forces the gear to snap exactly into alignment (you should see a little movement when you first rotate the wheel), and may solve your swerving issue.

2) Attach a strut to the gear pieces from a central fuselage piece.

3) make sure your gear are attached as firmly as possible, preferably to a fuselage piece. If the gear flex and change orientation even a little bit it can throw the aircraft into a spin.

Beyond that, I can't help. Some designs just do that with no indication as to why and can't be fixed. If you still can't get it to work, just make a new plane.

I'm in 1.2.2 and I have the same problem of @Drew Kerman; I build two different planes, one with the fixed gear and one with the first retractable gear and always have this "imaginary" force that push my planes sideway around 30/40 m/s.

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@Drew Kerman tilt your main wings upwards a little bit, this will reduce the weight the wheels have to carry.

Also use the gizmos on global mode with snap on and align them perfectly straight, your plane should not be tilted on the editor, it should be pointing forward.

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56 minutes ago, tetryds said:

tilt your main wings upwards a little bit

already are as much as I can - the cockpit naturally slopes back so the wings are not flat when the plane is horizontal. It's about 3-4° down pitch for level flight at cruise speed

56 minutes ago, tetryds said:

Also use the gizmos on global mode with snap on and align them perfectly straight

Done, but I still get some red yaw derivatives and as soon as my tail starts to swerve even a teeny bit the wheels flip out before I can correct with my rudder, which has the authority to counter it but the extra weight on one wheel makes the craft swerve off the runway

VOrrIPcm.png

1 hour ago, tetryds said:

your plane should not be tilted on the editor, it should be pointing forward

If I tilt the plane back to rest on all three wheels like it would be during the initial takeoff roll, FAR gives me different values for its data + stability derivatives than if I leave it level. That seems to me like I should be positioning the craft in the actual position I want to measure its performance in no?

About ready to say "eff this" and just keep dropping it from 600m to recover into level flight

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Posted (edited)

1 hour ago, Drew Kerman said:

If I tilt the plane back to rest on all three wheels like it would be during the initial takeoff roll, FAR gives me different values for its data + stability derivatives than if I leave it level. That seems to me like I should be positioning the craft in the actual position I want to measure its performance in no?

Short answer: No.

Long answer: Your plane gets unstable when your tail lifts up, I have build plenty of airplanes that do this, and almost every airplane from the BAD-T challenge are capable of doing this.

Aligning your wheels while your airplane is tilted may result in a misalignment when the tail lifts, causing side forces and flipping you.

The best way to solve this is not increasing wheel friction, but decreasing it, as your wheels take lateral force you will simply drift around until you are fast enough to take off.

Not the best solution, but it works while you figure out better configurations for it.

About wing tilt, it doesn't need to have enough lift to take off while sitting on the ground, but when the tail is up, so yeah never tilt your airplane on the editor unless you want to see how it looks like while landed and that can cause a lot of confusion.

If increasing your wing tilt shifts your aerodynamics center you are relying on your horizontal stabilizers for lift, which is not a good idea, you may have to shift it in order to get a stable lift point from your main wings.

Remove your horizontal stabilizers and place the main wings so that their lift acts on the center of mass of the airplane, then add them back, this is going to be a lot more precise.

Ah, never forget to lower your wing mass, default wing mass strength is insanely high.

Edited by tetryds

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6 minutes ago, tetryds said:

Aligning your wheels while your airplane is tilted may result in a misalignment when the tail lifts

hard to see, sorry bad angle but the image I posted the aircraft is level. I didn't try to align the wheels when it was tilted, it was only tilted for the FAR analysis

6 minutes ago, tetryds said:

The best way to solve this is not increasing wheel friction, but decreasing it

Will give that a try next time and see what happens

7 minutes ago, tetryds said:

so yeah never tilt your airplane on the editor unless you want to see how it looks like while landed and that can cause a lot of confusion.

ok, well my rationale was that this is how it's going to be running along the ground up until the tail wheel lifts off at ~30m/s so I figured that's how I should model its stability derivatives to see if there are any red numbers during that time.

9 minutes ago, tetryds said:

If increasing your wing tilt shifts your aerodynamics center you are relying on your horizontal stabilizers for lift

no issue here, the wing tilt is just to align with the fuselage and produces all the proper lift I need in this configuration

9 minutes ago, tetryds said:

Ah, never forget to lower your wing mass

check. I've had the main wings at 0.4, the horizontal stabilizers 0.35 and the vertical stabilizer is 1.5 with the ctrl surfaces for the main wings 0.35

Thanks for the help. I know you have tons of experience with this, so I appreciate it

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On 5/13/2017 at 8:06 AM, Drew Kerman said:

wLDZ5adm.png

Hello Drew Kerman. Your aircraft style is recognized from e.g. here

I have a suggestion to improve the aircrafts. Switch the green and red navigation lights with each other. Please. It might make some Kerbal aircraft engineers and pilots jittery otherwise, you know. Not naming any names of course *innocent whistling*. :wink:

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Posted (edited)

Flying wing with differential split-rudders

I finally managed to make a flying wing that has yaw control just by differential break rudders. Just stock parts, no reaction wheels, no thrust vectoring, no other mods. Others have probably done this, but I still think this is kinda cool :wink:

How does it work?
The wings are canted upwards into a slight V form. On each wing there are 4 pairs of split elevons - that is two elevons stacked on top of each-other. The elevons are set to +/-100% yaw (-100 top/+100 bottom) with full ctrl deflection and ~30% roll. I tried using a M-form for the wings but that didn't look as nice, although I did experience less roll-pitch coupling.

How do you fly it?
Carefully. Immediately after take-off set SAS to prograde and never ever turn it off. Minimum take-off speed is around 60m/s. For landing use airbrakes and reverse thrust and touch down at less than 80m/s. The plane suffers from some buffeting due to the SAS, but you can manually counter that. It does have some inertia coupling so it's best to roll, wait, and then pitch. Other than that this is actually flyable and stable even at transonic speed (tested up to mach 1.05). No warranty!

Get it here https://kerbalx.com/capnrotbart/V-Wing-Y5

Edited by CapnRotbart
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11 hours ago, Rodhern said:

Hello Drew Kerman. Your aircraft style is recognized from e.g. here

I have a suggestion to improve the aircrafts. Switch the green and red navigation lights with each other. Please. It might make some Kerbal aircraft engineers and pilots jittery otherwise, you know. Not naming any names of course *innocent whistling*. :wink:

What the $h!t I checked where they should be before placing them. Oh well, I got it correct here https://www.flickr.com/gp/kerbal_space_agency/8L0Bu6

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Been working on a (relatively) realistic stock MiG-17 for FAR this week, so I figured I'd make a short cinematic showing it off. As with all the aircraft I build for FAR, the cockpit reaction wheels are disabled so that only the control surfaces are used. Some of the footage was sped up a tad to make it fit the tune better, but most of it is in realtime:

 

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Posted (edited)

On 2017-06-01 at 10:16 PM, Elmetian said:

Been working on a (relatively) realistic stock MiG-17 for FAR this week, so I figured I'd make a short cinematic showing it off. As with all the aircraft I build for FAR, the cockpit reaction wheels are disabled so that only the control surfaces are used.

I always disable the cockpit reaction wheels, much more satisfying. You probably know of the (Semi-)Saturatable Reaction Wheels mod, but if you haven't tried it i really recommend it for that added bit of feel :D I have to do a MiG-17 too, looks fun to fly, thx for the inspiration!

Edited by Cratzz

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On 6/4/2017 at 4:05 PM, Cratzz said:

I always disable the cockpit reaction wheels, much more satisfying. You probably know of the (Semi-)Saturatable Reaction Wheels mod, but if you haven't tried it i really recommend it for that added bit of feel :D I have to do a MiG-17 too, looks fun to fly, thx for the inspiration!

Yeah, I think I tried that mod a year or two ago when it was first released. Not had much time to keep up with mods lately, might give it another go on my next install (I'm still playing with 1.2.2 at the moment)

Anyway, here's another short cinematic showing off the Bogatyr Mig-17 ripoff from the last video, as well as my Flanker/Fulcrum ripoff called the Kossack, both of which are designed solely for FAR and use only stock parts:

 

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