Sneak Peak

[weebiboi.ksp]

Sneak peak of the development of my latest spaceplane at https://steamcommunity.com/sharedfiles/filedetails/?id=1383467003.

Download the original spaceplane at https://kerbalx.com/weebiboi_ksp/Falcon-A2.

[Noobton]

Looks nice Weebiboi! I'm moving this to spacecraft exchange though.

[weebiboi.ksp]

2 minutes ago, Noobton said:

Looks nice Weebiboi! I'm moving this to spacecraft exchange though.

Actually, yes. It did crash during testing. Bad luck or horribly designed craft?

[Shadow dream]

Horribly designed craft it is.

It sounds evil, but what you did is to build a very tail heavy plane. You know what people say: A nose heavy plane flies poorly, a tail heavy plane flies once.

You can notice that by the yellow ball (center of mass) being behind the blue ball (center of lift). It HAS to be the other way round.

Edit: Just for your information, the exact position of CoM and CoL are much about trial end error, but ultimately depends on how fast your craft is supposed to fly. I.e if you build a WW1 type of plane, flying at less than 100 m/s allowes for CoM and CoL to be very close, with CoL being slightly behind CoM. It improves maneuverability. If you want to get faster (e.g. SSTOs) those two need a stronger distance in order to improve stability. However, if they are too far appart, your maneuverability will be poor or non-existent ( = nose heavy plane).

Also you have to look at wet mass and dry mass. The way you place your fuel tanks arround CoM will more or less make CoM shift, which WILL affect your stability and maneuverability. An empty fuel tank has less influence on your CoM which can lead to significant movement of balance. Worst case is when you start with a stable plane, but shifting CoM ends up making your plane tail heavy, which means crashing.

Edited May 11, 2018 by Shadow dream

[weebiboi.ksp]

18 minutes ago, Shadow dream said:

Horribly designed craft it is.

It sounds evil, but what you did is to build a very tail heavy plane. You know what people say: A nose heavy plane flies poorly, a tail heavy plane flies once.

You can notice that by the yellow ball (center of mass) being behind the blue ball (center of lift). It HAS to be the other way round.

Edit: Just for your information, the exact position of CoM and CoL are much about trial end error, but ultimately depends on how fast your craft is supposed to fly. I.e if you build a WW1 type of plane, flying at less than 100 m/s allowes for CoM and CoL to be very close, with CoL being slightly behind CoM. It improves maneuverability. If you want to get faster (e.g. SSTOs) those two need a stronger distance in order to improve stability. However, if they are too far appart, your maneuverability will be poor or non-existent ( = nose heavy plane).

Also you have to look at wet mass and dry mass. The way you place your fuel tanks arround CoM will more or less make CoM shift, which WILL affect your stability and maneuverability. An empty fuel tank has less influence on your CoM which can lead to significant movement of balance. Worst case is when you start with a stable plane, but shifting CoM ends up making your plane tail heavy, which means crashing.

I noticed this but couldn't fix it, so maybe all I need to do is simply rebuild the craft.

[Shadow dream]

When I ran into this problem I realized that I could not build crafts with lots of engines at the rear (where I thought they would make sense and construction easier). Engines are heavy. They are always heavy (opposed to fuel tanks), so they pull your CoM far behind and ultimately behind your CoL. What you could try is to palce your engines closer to the middle of your craft and/or build a BIG tailwing behind your current engines.

Even though MK2 parts are pretty drag heavy, when I use them I usualy put a MK2 fuel tank on the side of the center tank. There I can mount engines (onto bicoupler) and intakes (also on bicouplers), which helps keeping the CoM where it starts. That way it's easier to control the changes during flight.

tldr; get your engines further forwards, as centric as possible, then get bigger tail wings.

[Foxster]

"peek" not "peak". 

[weebiboi.ksp]

On 5/11/2018 at 4:31 PM, Shadow dream said:

When I ran into this problem I realized that I could not build crafts with lots of engines at the rear (where I thought they would make sense and construction easier). Engines are heavy. They are always heavy (opposed to fuel tanks), so they pull your CoM far behind and ultimately behind your CoL. What you could try is to palce your engines closer to the middle of your craft and/or build a BIG tailwing behind your current engines.

Even though MK2 parts are pretty drag heavy, when I use them I usualy put a MK2 fuel tank on the side of the center tank. There I can mount engines (onto bicoupler) and intakes (also on bicouplers), which helps keeping the CoM where it starts. That way it's easier to control the changes during flight.

tldr; get your engines further forwards, as centric as possible, then get bigger tail wings.

Thanks for the tip, I’ll try that when I can