Had a question...

[Draconiator]

With the new Aero, fins are A MUST when launching now. but I've learned that anything large does not need fins, such as my Fuel Transporter:

Why can my transporter get away with not having fins, where anything smaller MUST have them?

Edited October 14, 2015 by Draconiator

[Kelderek]

I'm guessing that the more mass a vessel has, the less that the aerodynamic forces can push it around. Fins at the back of a rocket are to add drag in order to hold the vessel straight.

[sal_vager]

Well, you have rather a lot of engine gimbal there.

[Red Iron Crown]

Gimbal++. Also, a lot of draggy struts behind the CoM by the look of it.

[Snark]

I'd say it's mostly engine gimbal. That, and having lots of mass, = more mass per surface area, = aero is less of an issue.

Also, what sort of TWR does that craft have? Sure, a Mammoth packs a lot of punch, but in your picture each one's shoving at least 4 of the giant fuel tanks in front of it. I'd guess your TWR is fairly low. If that's the case, then it may also be that you're already at a fairly high altitude before the speed really builds up, which would tend to make aero forces less.

[FancyMouse]

Well, to prove whether it's gimbal or not, just turn off SAS and see if it flips.

[Draconiator]

I'd say it's mostly engine gimbal. That, and having lots of mass, = more mass per surface area, = aero is less of an issue.

Also, what sort of TWR does that craft have? Sure, a Mammoth packs a lot of punch, but in your picture each one's shoving at least 4 of the giant fuel tanks in front of it. I'd guess your TWR is fairly low. If that's the case, then it may also be that you're already at a fairly high altitude before the speed really builds up, which would tend to make aero forces less.

Surface TWR at least 1.7, this one is going to refuel a Duna driller, sorry for the delay.

[Lynch]

Imagine throwing a paper straw towards the sea, and imagine a paper straw having a stone tied at the end of it towards the sea.

Now imagine just throwing an iron pipe towards the sea.

Paper alone is so thin and weightless that it loses against the drag; yet anything fairly light requires fins. And gimbal issue is also correct.