Cargo Plane How-To?

[The Space Dino]

I'm wondering, how do you guys make a working cargo plane that can fly?

I tried once, and my plane could not even go as high as 500m. I also had to hold the 'S' key to keep the nose up, if not it would just start to lose altitiude. Plus, the plane had nothing in its cargo hold!

On one occasion, my plane crashed in the sea at 150m/s and my plane got shredded, but my kerbals survived!

<hails the fixed 1.0.5 hydrodynamics>

So how exactly do you build a cargo plane?

Thanks!

[Columbia]

There are a lot of things to factor in, but the relation of the Center of Mass and Center of Lift are important. (The CoL has to be just *right* behind the CoM for maximum stability.)

Do you have an image of your cargo plane? There might be outstanding issues that we could explain with it.

Edited May 6, 2016 by Columbia

[Blaarkies]

That will get you sorted. If you already know how to build a plane, then just follow those principles, but with MK3 parts 

"...and my plane could not even go as high as 500m."
That sounds like patience, rather than wings or thrust. If it can fly, it should be able to reach up to 5 000m, given enough time though.

If you find it hard to go faster than 300m/s, then you might need more thrust(you shouldn't need more than 0.8 TWR on aircraft), or you need more altitude to break Mach 1

If you pitch you nose up to 15' but the prograde vector stays at 0'(meaning you are pointing upwards, but your altitude remains constant), then you need more wings.

"...I also had to hold the 'S' key to keep the nose up,..."
-Add more pitch control: any control surface for up/down movement on the tail will do...just go bigger?(You can also add them to the nose.  CAUTION: Too much will make it "flip-happy")

-Or, move your wings around some. In the SPH, click the Center-of-mass button, also the Center-of-Lift button. What you are describing is called a "land-dart"...it does what arrows do. That happens when the yellow-ball is too far in front of the blue-ball. 
  > So move wings around until the blue-ball is only slightly behind the yellow-ball(the balls should  touch).
  > Right-click a fuel tank and empty it. This shows how the yellow-ball is moving around in flight as you deplete fuel...keep that in mind, because if      the yellow-ball is BEHIND the blue-ball at any time in flight...you will be having a bad time ("flip-happy").

If you want to make cargo spaceplane, i suggest trying to build something similar to SKYLON. It does not even need to look like that, but it should function the same.
 -Canards at the nose(like pitch elevators)
 -High tail fin
 -Elevons on wings(for roll)
With those basic components, things start handling pretty easy, even at re-entry speeds. I built one with the B9 mod part pack, and it is the most stable plane i have ever seen...re-entry at 60' pitch without my keyboard input, without any tendency to fall over/flip around.
It weights 59t at launch, and can put about 7t in LKO. It is not figher-like super maneuverable...rather it does slow and predictable movements, like a 747...at Mach 5 

Edited May 6, 2016 by Blaarkies

[The Space Dino]

Thanks for the useful tips!

And Columbia I do not think I saved the craft I built but I will try to find it.