the trouble with corvettes is that they tend to cost a lot more than is originally planned. There is the risk of ending up with a ship that has small displacement and limited ability against nation states, but the cost is a high proportion of the cost of a destroyer.
Perhaps is better instead of talking vessel size, to talk vessel money.
A 7000t destroyer is say 1 to 1.5 billion dollars. An OPV is 100 to 150 million a piece. What is the cost of a corvette? 500 million, 600, maybe more. The original rational of the OPV was to replace the Armidale class at around 30 million dollars apeice. Do you want a 600 million dollar vessel checking up on fishing boats?
There is a definate need more an OPV. Cheap, long range, endurance, modest crewing etc. If you start to go down the corvette route with nukla decoys etc, the unit price is going to triple or more. There are heaps of areas where a lightly armed OPV would be fine, Solomons, Fiji, PNG, Polynesia, disaster relief, fishery protection, border protection.
Its nice to have a third carrier, its nice to have nuclear subs, its nice to have more money spent on items, but there are only so many dollars. What can be done for x dollars is the question. Australia comes in around 14th in the world in spending. Assuming is defence expenditure gets up to 2 percent of GDP (and thats a big if, since we cant balance the budget now), it might rise from 1.8% GDP to 2.0% GDP, thats roughly a tenth extra.
So working out what we want, has to be constrained by how much money we have. As to more amphibious capability in the Karl Dorman class, why add another class of vessel, why not just get another Choules, I am sure Britain would build us one if we asked.
I just ask, that when talking about ships, think of how much they are going to cost and what can be afforded
You missed the point entirely, probably because you haven't bothered to read my earlier posts.
First of all what you have written about corvettes could just as easily apply to any naval platform that isn't adequately planned or project managed.
Two the terms I am using, light frigate and corvette, refer to a frigate that is smaller and lighter than the RANs AWDs and desired 5000 to 7000t and a smaller combatant that is faster and better armed than an OPV making it suitable for fleet task force operations. It would actually be easier if we called the planned new frigates destroyers, then I could just refer to my concept as frigates.
Three the remaining FFGs and all ANZAC ASMDs are full of useful, up to date systems that could be easily and cheaply refurbished and reused on a new more modern platform. While still very capable these systems are of little value for the proposed ANZAC replacements but would transform the capability of the light frigate. I am not just referring to weapons but also sensors, propulsion plant, and auxiliaries.
Four, if you look at modern platforms such as Singapore's Formidable class you will see that a capable frigate can operate with a very small crew i.e. 70, perhaps even less. The Sigma class as operated by Indonesia fits the size we are meant to be considering for our OPVs / OCVs have a complement of 80 and German's K130s have a crew of 65. A patrol boat division, of which there are seven, has three PB crews and two Hull POs, which is about 65 to 70, meaning we can easily crew several "light" frigates without increasing manpower.
Five steal is cheap and air is free, meaning a more capable OPV of 4000t (such as the BAM at almost 3000t and the Dutch Holland class at almost 4000t are viable alternatives to smaller the 1500-2000t vessels we seem to be talking about. This extra size would provide a hanger and multi-mission deck for very little extra cost and make it comparatively easy to design in the ability to integrate USN LCS Mission Modules, such as MCM, as well as potential Australian developed hydrographic modules.
Six, combining refurbished and upgraded propulsion systems such as the ANZACs diesels (which could be ungraded to the same T93 spec as the RNZN) and even LM2500 GTs, would provide better performance than an OPV with new diesels, at lower cost. We already own the eight cell Mk-41 VLS on the upgraded Adelaide and ANZACs, the 76 and 127mm guns, Mini Typhoons, Nulka, Phalanx (there is an RAN pool of these weapons), Mk-32 torpedo tubes (upgraded for MU90), CEAFAR radars, Vampir NG IRST, Spherion B sonar, torpedo decoy, SRBOC. There are even items of equipment such as diesel generators, compressors, pumps, motors valves, etc, that could be refurbished and reused for much less than buying new items from overseas. Even the some of the SAAB 9LV combat system could probably be reused as it is also used on the LHDs and continues to be developed and improved.
When you look at the quantity of useful equipment we have at our disposal it is quite clear that it would be possible to build a larger more capable vessel using that equipment for lower cost than building a smaller less capable vessel with all new systems. The smaller OPV would need new systems as apart from the Typhoon and .50cals, pretty much everything else on the Armidales is shagged or not up to what is required by an OPV.
Long story short, my proposal has the potential to deliver much more capability for less cost than the proposed OPVs. Build six or eight frigates, six or eight corvettes and six or eight OPVs to replace the PBs, MCMs and hydrographic ships. Use as many pulled through systems as possible and where that is not possible use common systems between the vessels to keep costs down. The use of so much in-service equipment reduces training and logistics costs of a new class in addition the obvious fact we already own the stuff and don't need to spend hundreds of millions buying new equipment.
The reason the FFGs and ANZACs are being replaced is the platforms are shagged and too limited by size to be further upgraded to face modern threats. Their systems, fitted to new platforms would save money while increasing capability and providing a very useful complement to the proposed twelve primary surface combatants. I have stated this many times in previous posts as you would be aware if you had read them, so by all means disagree with me and point out any issues you have with my thinking, but please do not tell me how to suck eggs when the primary issue is you have not been bothered to read what I actually proposed.