Interesting discussion.
A few points.
• IMO the rationale for the T31 concept as first proposed is gone. A frigate with only 12x CAMM and no sonar was ridiculous from the beginning but due to a stable security environment HMT pushed it through. Times have changed and the T31 will have to change. IMO @Tempest414 has it spot on with the first two hulls: 57mm, 2x 40mm, 40x CAMM and 8x NSM with another 8x NSM easily added if required. Hulls 3,4 and 5 can follow the same format or upgrade.
• The original T31 requirement is now not satisfied. Building another batch of lightly armed T31 would do it but it would be a decade before they arrive and planning doesn’t have the luxury of kicking the can down the road for a decade anymore. Therefore I would suggest that five vessels need to be rapidly procured to fill the original T31 requirement. A patrol vessel built to an OPV+ standard with a 57mm backed up two 40mm, TACTICOS and NS50 or NS110. A generous open deck capacity of at least 6x TEU should be included for containerised CAMM and/or MLRS along with the ability to rapidly add a basic TAS. Set the budget at £150m to £175m and aim for 50 core crew plus flight and an EMF of 50.
• The containerised CAMM should not be controversial as it would rarely be fitted but it would be essential self defence in some instances. It may also become necessary for the MRSS and FSS to occasionally embark it also. Why not design a unit that can be used on land and at sea? The more simple and straightforward the better.
• The reason these 5 patrol vessels are needed to still meet the original T31 requirement is because RN will now be stretched everywhere all at once but not necessarily in kinetic exchanges. RN will need additional mass to successfully mitigate these challenges and the vessel described above is all that is required in the next 5 years to provide the extra mass. These OPV+ vessels would be especially effective when paired with the MRSS such as an Enforcer 14428 or stretched Vard 7 313.
• RN would then have a compact but extremely well balanced fleet plus a clear pathway to continue enlarging if the global security landscape started to deteriorate further.
By 2030 RN would have:
- 6x T45
- 8x T26/T23 ASW
- 5x T31 GP with 40x CAMM and 8x NSM
- 5x OPV+ with Wildcat and 57mm, 2x40mm
- 5x RB2 with zero upgrade
This could followed in the early 2030s with another 5x T31/T32 and 6x MRSS providing excellent strength in depth which could be easily added to if required.
It isn’t perfect but RN has few other options to add mass within the next decade.