Attaching plane engines?

[strider3]

I've run into the usual problem doing a "search" for this...the website locks up tight and I have to use Task Manager to shut IE down. I'm guessing, if "search" would work, that this has been posted before. But, since it doesn't...I am trying to build my very first plane, with a very elementary science rating. Here is what I have, so far:

 

My question is...how do you attach the J-20 Juno's to this plane? I've tried placing them under the wing, but they don't want to attach? What am I missing here?

TIA for any help.

Vic the Newbal

[DD_bwest]

i think if you wanna attach them to a wing you gotta use a strut to make a mounting point, but i could be wrong.  i dont make many planes.   i usually surface attach some tanks to the rear end of the fuselage.

[AeroGav]

Some parts can be radially attached (glued on the outside) of another part, like you are trying to do here, but Junos (most engines in fact) aren't among them.

The can only attach via attachment nodes.

The size 0 liquid fuel fuselage (that holds 50 LF) allows radial attachment so you'll have no problem sticking one under each wing.

This is the core of your engine nacelle.  The size 0 fuel tank has an attach node at the front and back end, so you can put an engine on one end and tiny intake on the other.

BTW that's a heck of a lot of fuel you got in the main body already... you planning to circumnavigate Kerbin?

[bewing]

That's a rather tiny wing, too. You generally want a minmum lifting area of about 2 for each 400 units of lf.

Also, that's a pretty high tech wing. If you have that then you also have access to the Precooler, or the Divertless Intake. You can replace one of your main fuel tanks with one of those, and then replace your rear tailcone with a Juno.

 

[Rath]

You are trying to attach an engine directly to the fuselage.  That will not work, because engines are not able to surface attach.  you need to make a nacelle.  The most basic way to do this is to surface attach a mk0 liquid fuel fuselage to the wing.  Then, on the back of the liquid fuel fuselage place your juno jet engine, and on the front place the mk0 intake.

 

Edited December 2, 2016 by Rath

[Chaos_Klaus]

Oh and by the way ... you need a horizontal tail plane. At the moment you have no way of controlling pitch or roll other then the reaction wheels in the cockpit.

[AeroGav]

6 hours ago, bewing said:

That's a rather tiny wing, too. You generally want a minmum lifting area of about 2 for each 400 units of lf.

Also, that's a pretty high tech wing. If you have that then you also have access to the Precooler, or the Divertless Intake. You can replace one of your main fuel tanks with one of those, and then replace your rear tailcone with a Juno.

 

If he has an NCS adapter he can go from a 1.25m down to 0.625m part in a low drag way.   The FL-A10 adapter is also 1.25m at one end and 0.625 at the other, but it's a high drag part.

The danger is the plane he made might have excess takeoff / landing speed for the weak gear, and also landing off-airport for the survey contracts.

I just went straight from cockpit to tail connector on my basic airplanes.  There is a strake / triangular wing section attached to the top of this cone, making the vertical stabilizer

Edited December 2, 2016 by AeroGav

[Magzimum]

In KSP, jet engines cannot attach radially to wings or tanks themselves. You have to put something in front of them. For the Juno, you have only 2 options, I believe:

1. Use a Mk0 fuel tank, and attach the engine behind that tank. (Yes, that is a little weird, but you'll get used to it).
2. Use the small nosecone.

Note that in this 2nd setup, you have to add a fuel tank somewhere else, and also an air-intake!

Also note that these planes that I posted are not finished. Several parts (elevons, wheels) are still missing. 

Edited December 2, 2016 by Magzimum
adding disclaimer at the bottom :)

[bewing]

OK, so if we're gonna post basic jets, here's mine: (the fuel tank starts out only half full, and you can replace the girders with SciJr's or an empty fuel tank)

[AeroGav]

1 hour ago, bewing said:

OK, so if we're gonna post basic jets, here's mine: (the fuel tank starts out only half full, and you can replace the girders with SciJr's or an empty fuel tank)

Performance doesn't really matter on these early designs but those cubic struts are draggy.  Also those basic swept wings have half the wing area/lift rating of other wing parts, though they have the same lift/drag ratio.

A slightly higher performance version of my basic bird, requires Terrier engine, and retractable wheels. 

Spoiler

https://kerbalx.com/AeroGav/Juno-basic-ssto

 

 

[bewing]

6 minutes ago, AeroGav said:

Performance doesn't really matter on these early designs but those cubic struts are draggy.  Also those basic swept wings have half the wing area/lift rating of other wing parts, though they have the same lift/drag ratio.

A slightly higher performance version of my basic bird, requires Terrier engine, and retractable wheels. 

  Reveal hidden contents

 

 

Yes, it's not an optimal design. The Type B structural wings are a much better deal than those nasty basic swept wings.

Edited December 2, 2016 by bewing

[foamyesque]

11 hours ago, bewing said:

That's a rather tiny wing, too. You generally want a minmum lifting area of about 2 for each 400 units of lf.

Also, that's a pretty high tech wing. If you have that then you also have access to the Precooler, or the Divertless Intake. You can replace one of your main fuel tanks with one of those, and then replace your rear tailcone with a Juno.

 

That's a structural C, which is on the first aero node along with the cockpit, elevons, and juno. Am I missing something?

 

As far as basic plans go, this is my layout:

 

It'll go supersonic in a shallow dive, and cruise at Mach 0.95 level flight.

 

It also fits my primary design criteria, which is: "Looks like a plane"

 

Edited December 2, 2016 by foamyesque

[AeroGav]

4 hours ago, Magzimum said:

 

1. Use the small nosecone.

 

Note that in this 2nd setup, you have to add a fuel tank somewhere else, and also an air-intake!

 

That's awesome, i never realised they could radially attach.    @WanderingKid was trying to make a Juno SSTO.  He had access to the larger circular intake but was having to  stay inside the 30 part limit.  This could save a fair bit of part count on a quad (or more) engine setup.

[bewing]

4 hours ago, foamyesque said:

That's a structural C, which is on the first aero node along with the cockpit, elevons, and juno. Am I missing something?

No, I just forgot which tech node it was on.

4 hours ago, foamyesque said:

It also fits my primary design criteria, which is: "Looks like a plane"

 

Did the Wright bros first plane look like a plane?

[Tex_NL]

5 minutes ago, bewing said:

Did the Wright bros first plane look like a plane?

A little. And it flew ... a little.

@foamyesque is correct. Planes that look like a conventional plane usually fly best.
That doesn't mean unconventional planes won't fly. But conventional designs are more predictable.

[bewing]

3 minutes ago, Tex_NL said:

 

@foamyesque is correct. Planes that look like a conventional plane usually fly best.
That doesn't mean unconventional planes won't fly. But conventional designs are more predictable.

I disagree. Canard designs are technically superior in almost all ways, which is why Burt Rutan exclusively built them. Conventional designs are relics of ossified conventional thinking from almost 100 years ago.

[Tex_NL]

7 minutes ago, bewing said:

I disagree. Canard designs are technically superior in almost all ways, which is why Burt Rutan exclusively built them. Conventional designs are relics of ossified conventional thinking from almost 100 years ago.

To be honest I do not consider canards to be unconventional.
What I meant by unconventional are the Kerbal planes you see on the forum. Planes with half a dozen wings and no tail or canards. For me a conventional plane is one with one set of wings (single or double deck) with ailerons and perhaps flaps. A tail or canards for pitch control. And one or more vertical tails for directional stability and yaw.

Edited December 2, 2016 by Tex_NL

[foamyesque]

5 hours ago, bewing said:

I disagree. Canard designs are technically superior in almost all ways, which is why Burt Rutan exclusively built them. Conventional designs are relics of ossified conventional thinking from almost 100 years ago.

 

There are advantages to a tail stabilizer over canards; they're usually more forgiving of command errors, for example, and since they tend to be elevated above the CoM they will also add roll damping (which may or may not be desirable depending on the rest of your wing layout, but it certainly can be an advantage). It's also generally easier in KSP to extend a tail spar backwards than it is to stretch the nose of a craft out, so you can get longer control arms. I prefer canard layouts in KSP because they give you much more control authority for the same mass and are better able to give you high-angle flight, which are important considerations for a spaceplane, but if I were building a KSP airliner I'd go with a tail stabilizer tuned to avoid generating anything beyond about a 20 degree AoA, flaps engaged, for landing.

 

EDIT:

Also, canards look dumb until pretty late in the tech tree

Edited December 3, 2016 by foamyesque

[strider3]

23 hours ago, AeroGav said:

BTW that's a heck of a lot of fuel you got in the main body already... you planning to circumnavigate Kerbin?

I want to do contracts on Kerbin and, to be honest, since this is my first plane I have no idea how much fuel I will need.

[strider3]

OK...got the engines attached (Thanks!!). And the comment on wing size was spot on...could not get off the ground at speed. So I went with a bigger area of wing and finished off the tail area. It took me a few tries before it dawned on me that the wings don't come with ailerons or elevons...so I added those and a short wing on the ends (probably overkill there):

As I said...my first try at a plane so...I am really flailing around. My problem now is exploding on take-off...the tail hits the ground when I lift the nose. Not sure why the tail cone has to be that long?

Edited December 3, 2016 by strider3

[AeroGav]

Could swap to one of these instead, much lighter, a bit draggier but not by much.

How is the centre of mass when the fuel tanks empty? does it move forward much?

You've got engines directly over CG,  relatively heavy cockpit in front of CG, but not much at the back, other than fuel, which can end up getting used.

If it proves to be an issue you could think about attaching engines to back end of main fuselage instead.   Or even a Science JR.  You're probably going to start getting survey contracts soon some of which will be surface surveys, so a) make sure this plane can land anywhere and b) may as well do some science while you're at the biome

[Tex_NL]

2 hours ago, Victor3 said:

OK...got the engines attached (Thanks!!). And the comment on wing size was spot on...could not get off the ground at speed. So I went with a bigger area of wing and finished off the tail area. It took me a few tries before it dawned on me that the wings don't come with ailerons or elevons...so I added those and a short wing on the ends (probably overkill there):

As I said...my first try at a plane so...I am really flailing around. My problem now is exploding on take-off...the tail hits the ground when I lift the nose. Not sure why the tail cone has to be that long?

Loose the rear fuel tank and attach the tail directly to the front tank. Move the horizontal and vertical stabilizers to the tip of the tail. Tilt the main wings back slightly to increase lift.
To improve stability you can also move the main wings upwards to raise the CoL slightly above the CoG.
And if you have access to it yet in your career use the "Tail Connector B". It is swept up so you'll have better luck avoiding a tailstrike.

Edit: After some additional minor tweaks it turned into a plane that flies remarkably well. It's slow and sluggish but it does fly nice and stable.

Edited December 3, 2016 by Tex_NL

[bewing]

5 hours ago, Victor3 said:

My problem now is exploding on take-off...the tail hits the ground when I lift the nose. Not sure why the tail cone has to be that long?

One other thing you can do is just not lift the nose. You build the plane so that the nose wheel is "taller" than the two rear wheels, so it sits normally with the nose tilted up just a little. When you get up a little speed, the thing will lift off all by itself. It's actually safer that way, because it's one less maneuver you have to do right next to the ground.

[foamyesque]

8 hours ago, Victor3 said:

As I said...my first try at a plane so...I am really flailing around. My problem now is exploding on take-off...the tail hits the ground when I lift the nose. Not sure why the tail cone has to be that long?

Tail-strikes are pretty much a constant hazard. There's ways to reduce or even eliminate them -- larger wing area, tweaking gear positioning, angling the tail spar upwards (either by using the tail B/slanted adapters, the rotate gizmo, or both), higher TWR, etc -- but there's tradeoffs involved elsewhere if you do. The tail cones are long so that control surfaces mounted on them can have long lever arms to maximize their impact on the aerodynamics; you're not taking full advantage of it. You're also suffering from building a pretty long plane for the early gear.

@Tex_NL's redesign is pretty much exactly what I would suggest doing, although personally I might use the offset tool to slide the tail control surfaces even further back. Control surfaces in general should be mounted at the ends of a plane, and tails in particular can go right to the very end. I usually set them up so that only the very front tip of them actually touches the tailcone, and the yaw stabilizer and pitch stabilizers visually touch, looking like an extension of it. That gives you the maximum possible lever arm and control effectiveness as a result.

Another possibility I haven't seen mentioned for dealing with tail strikes yet is to change your gear from a trike layout to a taildragger. Put the tall fixed main gear in front of your CoM, and the small steerable unretractable gear at the back of the tail. What should happen then, if you get your gear positioning correct, is that the plane will start with a nose-up attitude, rotate through to level, and then be able to take off with a minor pitch command (or even do so on its own, depending). And even if you over-pitch and bring the tail down too far, it has a wheel on it to take the impact, so you're safe there. The downside is that, when you try to land them, taildraggers have a tendency to pitch forward and nose strike, particularly if you're applying brakes. There's a fairly narrow window of gear placements between "won't rotate forward on takeoff" and "will smash nose into ground on landing", so be careful.

[AeroGav]

5 hours ago, foamyesque said:

Tail-strikes are pretty much a constant hazard. There's ways to reduce or even eliminate them -- larger wing area, tweaking gear positioning, angling the tail spar upwards (either by using the tail B/slanted adapters, the rotate gizmo, or both), higher TWR, etc -- but there's tradeoffs involved elsewhere if you do. The tail cones are long so that control surfaces mounted on them can have long lever arms to maximize their impact on the aerodynamics; you're not taking full advantage of it. You're also suffering from building a pretty long plane for the early gear.

You forgot to add, adding incidence to the wings.  This reduces the pitch angle required to leave the ground.

Perhaps he should just must the airplane a tail dragger?  Can't have a tailstrike if the tailwheel is right at the back anyway.  Though it find them a bit hard to keep going straight on the ground.

Another layout change - loose the long tail.   Swap to a canard layout, mount the main wing high on the mani fuselage, then use strakes attached to the main wing to create twin tail booms.   That will have some serious ground clearance.

^^kinda like that, but high mount the wing.