Kryten wrote:It looks like you lose out in both scenarios when launching - a helical tower means the fins rub against the rails, and canted fins would try to twist the rocket on the launch rail, so there'd be excessive drag between the rail and the buttons.
You could help avoid this by having the launch rod go through the middle of the rocket (like the V2 at THUNDA). Ideally you'd want it right in the centre of the rocket, so you'd need to use a cluster of motors rather than a single motor.
That means the rocket would try to spin around the rod when launched, so there'd still be some drag.
It'd probably look cool, though
The whole reason for using a rail is that fins aren't effective, therefore cant will not be effective until you get a considerable way up the rail at least. I suspect it's probably not actually effective until some time after that. Some video of a rocket with canted fins should give you a fair indication of just how effective canted fins are just after launch.