Plane Design Help

[SelectHalfling0]

So I just built my first successful spaceplane (after 358 hours of playing KSP), and now I'm designing the Mk2 "Cargo Variant". The original plane had it's COL in front of the COM, but now this new plane has a far lighter cargo (the first variant used a 2 ton crew module, this one has a total .75 ton cargo, both mounted directly behind the cockpit). Can anyone tell me what the difference is if the COL is in front or back?

-Thanks in advance!

Edited October 11, 2014 by SelectHalfling0

[Pecan]

You can imagine all forces acting on, or around, the CoM. A force going directly through the CoM will push the vehicle in that direction, out of line it will tend to rotate the vehicle. So if all your engines are above the CoM they'll be pushing the top of the vehicle more than the bottom, making it tend to tip nose-down.

CoL works the same - if it's behind the CoM it will tend to make the plane nose-down, if it's in front it will tend to make it nose-up (off to the side, the plane will roll, etc.). While a plane that wants to go up sounds good in practice it makes the vehicle to prone to flipping which is why standard designs put the CoL just behind the CoM - too far and it'll be too hard for other things like wings/control-surfaces to counteract and the thing will never get off the ground.

[SelectHalfling0]

Thanks for the clarification!

Off to build MOAR spaceplanes!

[nine_iron]

I love the tiny spaceplanes I build with the MRS mod and its mini jet engines, those things are very cute!

I made a cool little drone testbed which I use to go straight up, fly level, run test, land.