In terms of post-war navies for the allied nations I think it would make a lot of sense to see a standardisation around British designs, modified depending on an individual nation's needs. France is really the only other country with the industrial capacity and colonial commitments to justify an indepenent fleet, and logically the Dutch, Belgian, Norwegian, Danish & Polish fleets will need to fulfill ancillary roles to the British in various theatres; North Sea & Atlantic defense and interdiction for the Norwegians & Danes, Baltic patrol and defense for the Danes & Poles, channel protection for the Dutch & Belgians, and deterence against Japan in east Asia for the Dutch.
Once you come to that conclusion then buying from Britain - either using British shipyards or builiding British designs under license - is the only thing that makes sense. From a logistical point of view doing anything else is madness when you are sharing bases and supplies, and will be coming under Royal Navy command & control in the event of war.
The French have too much pride to allow their own fleet to become a British auxiliary, but even so I would still expect to see agreement on things like a common calibre for naval guns and interchangability for electronics and other parts.
Off-the-shelf RN designs aren't likely - the RCNC doesn't have the manpower to design all the world's warships. A collaborative effort under the aegis of the Admiralty is highly likely however - particularly as warships get more complex and thus expensive over time. Multinational projects happened for a reason, and tend to work much better if one person/organisation is ultimately in charge. Here, the Admiralty are in a good position to do exactly that.
My first reaction was "Hmmm. Good point."
My second reaction was "Hey, wait a minute. Isn't that a problem their potential enemies have too?" Don't know about you, old chap, but I would not want to try moving a deep-draft ship inside the Norwegian barrier islands in foul weather unless I had a pilot who knew the local waters like the back of his hand. Too many ways to go crunch, otherwise.
Yes, storm-weather life would suck for the Norwegian MTBs. But knowing the local waters well might give them an edge over almost equally weather-bound large ships.
So far as I'm aware there is very little shoal water in Norway - at least for destroyer-sized ships. Lots of things to run into, but nearly all of them are poking out of the water.
How big/heavy/massy (displacement is a funny thing) does a ship have to get before it can operate in all (Eg: Most) Norwegian Sea conditions?
Depends where in the country you're going. Torpedo/missile boats make a lot of sense in the south, and in OTL there was a major threat there - not just from the USSR but also Poland and East Germany. With TTL's equivalent to the iron curtain being a hell of a long way East, that threat is significantly reduced. Not gone though - the USSR still controls the Baltic states, so figure there is a role for MTBs/missile boats around Oslo Fjord if nowhere else.
It's worth remembering that the sea state a boat can survive in is very different from that it can operate effectively in: MTBs are almost useless as a weapons platform in any sort of sea state at all, and their speed is also severely degraded. Destroyers can operate in most weather conditions, and submarines are almost completely invulnerable to the effects of bad weather.
Depends on what you mean by "operate". Sure, there's a certain minimum tons displacement above which the equivalent of Norwegian foul-weather conditions on the open ocean won't sling you around like a chip in a whirlpool. Which is the problem that would make an MTB crew's life miserable and possibly quite short, if they were trying to operate in really crap weather. pdf27 is certainly right to point out that problem.
The problem is that we're not talking open ocean - the larger your ship gets, the more dangerous an environment like the fjords and in-shore waterways becomes if storm weather can shift you even a little, or you don't have very good maps and soundings. There's no sea room and the water has teeth; there are lots of rip-your-hull-open hazards like skerries that can be hard to detect even in clear weather unless you're right on top of them. (Which is why intimate knowledge of the local waters is such an advantage.)
So the risk level for both MTBs and large ships is going to climb in bad weather. When it effectively shuts down operations for big ships as well as MTBs, the Norwegians win - remember they're playing defense. The right question to ask is about conditions that make MTBs too hazardous to run but don't seriously imperil large ships: how common is that band of sea states?
Some web searchery found an interesting snippet in Wikipedia's entry on torpedo boats that (somewhat to my surprise) actually seems to settle the question: "Although torpedo boats have disappeared from the majority of the world's navies, they remained in use until the late 1990s and early 2000s in a few specialised areas, most notably in the Baltic. [...] Operating close to shore in conjunction with land based air cover and radars, and in the case of the Norwegian navy hidden bases cut into fjord sides, torpedo boats remained a cheap and viable deterrent to amphibious attack."
So it looks like the specific conditions of the Norwegian littoral turned out to be the last best deployment for MTBs. What eventually did kill off them off was longer-range anti-ship missiles; foul weather was not the deal-breaker.
The Baltic is somewhat different - compared to most Norwegian waters it's incredibly sheltered. The problem MTBs have is that the very limited displacement means that they can't fit sophisticated weapons systems, and this in turn means that they can only operate (in the sense of use their weapons system effectively) in good weather.
An excellent example of this is the attack on the USS
Liberty - the MTBs attacking it estimated her speed at 30 kts, partly due to poor radar kit but primarily I suspect due to the fact that they were going flat out and not closing very fast due to trying to make way into a seaway and not appreciating just how much that degraded their performance.
The other thing to remember is that the Norwegians have been watching just how effective a proper navy is in their conditions, and taking part in extended deep-water operations in defending the Narvik convoys throughout the war. That is bound to affect their thinking too.
Will this TL continue into a cold war scenario?
I've got about 60 years postwar sketched out, albeit only some aspects of the story so far.
