So I designed a ship a couple weeks back, I made a deckplan and everything. Its a 500 ton Corvette dubbed the Hero-Class Corvette.
Its combat role is either an escort ship or as a fast attack ship, acting in squadrons.
What's the general opposition it's likely to face? Corvette, and escort ship, generally implies pirates, which in turn implys less-than-top-gun opposition (always a good sign!)
Unfortunately I can't decide what would be practical to arm it with.
The layout I first had was 2 Triple Beam Laser, a Triple Missile launcher and 2 Double Pulse laser/sandcaster turrets for point defense.
this seemed ok but I wondered if I could afford to drop one of the defense turrets.
Why pulse lasers for point defence? Quick double check - have you got access to High Guard? Only the Beam and Pulse Lasers sort of swapped role. Pulse lasers hit pretty hard but have an accuracy penalty that sort of rules them out of PDL role as soon as Beam Lasers become available.
I then realised with 80 tons of cargo space I could easily fit a bay weapon (I'm thinking missile bay)
What do you think? What would be the most reasonable weapon set for this ship?
Not sure. Big thing to bear in mind is that pirates are generally lightweight raiders, upgunned civilian ships, etc. Nothing designated 'corvette' should be taking on a proper warship. As Phavoc notes, the big problem with ordnance is running out of it. If you are likely to be deploying forwards on extended patrol or escort duties, I'd avoid ammunition-based weapons, especially since a missile launcher isn't all that much more powerful than a laser anyway, just longer ranged.
By the by, Its TL 12 and I'm avoid using Particle Beams on ships of the line.
Fair enough.
Suggestions
I'm assuming pirate suppression and escort duties:
1) Your main weapons threats are things like lasers and missile type weapons.
2) Primary protection is Reflec-coated armour and good point defence installations.
3) Two Beam Laser/Sandcaster turrets are good, a third is better but possibly overkill, since it's biting into your main armament. If packing one or more bay weapons, though, that'll do fine.
4) Your main task is to protect yourself and the (probably pretty vulnerable) merchies in your convoy. If both sides disengage unhurt at the end of the battle, that's a net win for you.
5) If you don't want particle weapons (nice to see someone use something else!) then a fusion cannon bay might be good. They are short range, but are very cheap for their punch, meaning low maintenance costs, something appreciated in a 'second line' escort ship. Alternatively a meson cannon is a good general purpose weapon - meson screens are a bit high-end for most small warships, allowing you to bypass even fairly heavy armour.
6) That leaves you with one hardpoint, and even with miniaturization upgrades you won't really be able to mount a second bay - railgun and missile bays yes, but the ammo requirements for two bays means that you'll struggle to carry a meaningful magazine, you don't want particle bays and meson and fusion bays are too high a TL for you to miniaturize. Something simple like a double or triple pulse laser with accurate and high yield upgrades gives a nice backup weapon in a pinch without using too much volume.
The best bet might be to designate your weapons volume as modular. A bay and four turrets that can be swapped out at will will set you back 11% of the cost of the Hero-class's hull, but it doesn't half make it more flexible, allowing you to swap out defensive armaments for more missile turrets and a missile rack if you have ready access to a friendly arsenal and expect to face someone big (at that point, many nuclear missiles are your friend)
