Newbie: How do I build a really long triple-rocket?

[Deslan]

So, I wanted to start out really simple, but do something fun. So I put together three rockets with one of those 1-to-3 thingymajigs at the top. I used those long solid fuel ones. Then I put on some separator thingies, and another set of long rockets. Then I put on a bunch of smaller solid fuel rockets, and sidemounted them with three more. So my takeoff is with 6 small solid fuel rockets, then I jettison those and start three long ones, and then a final stage with three more.

Problem is, this thing is falling apart. On the starting platform, it's all jiggly. And once in the air, there is sort of a pendulum effect and the rockets aren't attached to eachother so usually there's just a large BOOM at some point.

Even with my structural instability, I did at one point manage to get so high speed that my nose cone started glowing red from atmospheric friction. Just what I wanted! But it is currently more based on luck than anything else. Also, it's nigh impossible to steer this long thing, but I guess I can figure out the steering myself eventually.

What I need to know is how to tie those long rockets together. I want to keep them tight together like that, 3 of them, but so that they don't jiggle away from eachother. I want one single really long rocket, that acts as if it's solid. How do I add that structural integrity?

[sjwt]

Try strut setups like this one below, its extremely strong, you use symmetry on 6X and the small cubic struts(or two cubits/large ones if you need to get past overhanging edges). Use this kind of setup to really strengthen wobbly bits. Also use cross struts when dealing with all struts, makes them much more than twice as strong.

[capi3101]

EAS-4 Strut Connectors: The most useful part in the entire game for keeping the whole stack from coming apart. You'll find them more and more useful as your rockets get larger and larger.

Incidentally, if your nose cone is glowing red on takeoff:

1) You're going too fast. You're wasting fuel.

2) Nose cones don't do anything in the current version of KSP besides adding do-nothing mass. You might want to consider removing them...

[Sirrobert]

Easiest way is ofcourse to not make it as long.

If you want it long, maybe make it wider?