Why is my SSTO breaking apart?

[milosh]

This is driving me nuts, I've made an MK3 version of a succesful MK1 SSTO I have, same design just bigger parts and more power. Additional tanks are attached to the main tank and the wings to the side tanks. The MK1 version is very stable, can roll, loop and so on. The MK3 version explodes as soon as I pitch over 20-25° no matter how gentle I try, SAS or no SAS, with or without payload.

The rapiers are too weak in low speeds which is why I take off with the help of the rocket engines resulting in a much higher TWR at launch (1.5), that's the major difference from the MK1 version. In both planes I've shifted with the offset feature the side tanks a little bit into the main tank which makes them very stable, no wobbling of any parts. I wonder though if the forces in a 200t plane are just too strong or the MK3 parts are too weak for their own weight. Or does anyone see something wrong in my design that's causing it to explode?

Explodes when pitched over 20°:
[IMG]http://images.akamai.steamusercontent.com/ugc/644374753331496973/48D68FA7D4402D658817B9AF008AF73C70B41C04/[/IMG]

[IMG]http://images.akamai.steamusercontent.com/ugc/644374753331497551/51CFF8E7F757FAE93693C55A88F3C69D2F15E137/[/IMG]

This one works perfectly and is very stable, build after the same principle, only smaller:
[IMG]http://images.akamai.steamusercontent.com/ugc/644374753331513616/DF7DACAB5E625BB8B225034957A6874EC2658791/[/IMG]

[Empiro]

Press F3 to see the exact cause. You have a very large craft, so it could be some sort of breakage, though it's pretty hard to do that in stock.

[Venusgate]

Looks like clipping to me.

You are also very stingy on your lifting surfaces. What do you think this is, a space shuttle?

[milosh]

F3 says the link between the side and main tank broke, at least that's the first message after "Lift Off". I had a closer look and found indeed an error, one of the side tanks wasn't properly attached. I fixed that but the plane still explodes as soon as I pitch with the same F3 log.

@Venus: of course, this is the next generation self-fueling space shuttle NASA never dreamed of building :D As long as I don't pitch over 20° the plane is very stable and given the rocket power (lift off V~150m/s) I should be able to pitch well over 40° soon after liftoff and climb to 10k as fast as possible, if it wouldn't break apart this would be the plan anyways.

Could it be that MK3 parts are just not made to be attached to eachother sideways so to speak?