Hover Submersibles

Hover Subersibles are a subclass of hovercraft  making use of the common parts of both hovercraft and some submarines: the use of lift propellors underneath the vessel.

The Monitor-Spiteful's hoversub - going forward on cushion

Both hovercraft and submarines tend to have a weakness against standard surface vessels: they are both incredibly fragile due to their low stability, fragile engines and their carefully balanced frames. As a result, they use select stratagems to try and circumvent this downside. Hovercraft, use their speed and agility and submarines use the depth of water, to proect them from incoming fire. However, in both cases there are significent tradeoffs. 

Submarines are by nature much slower in the game than their surface counterparts, and frequently also less manueverable. This allows the surface vessel to choose the terms of the engagement, rushing in to drop depthcharges or fire hedgehogs and then darting out again, frequently faster even than the submarines main underwater torpedos. Should a submarine surface for any reason, one or two hits is normally sufficeient to prevent them from submerging again, and normally enough to sink them all together. This tends to make submarine vs. surface warships, a waiting game, where the patient player tried to get the other player to make a mistake. 

Alternatively, the hovercraft is a fast, agile ship, balancing on its four lift propellors. Normally lacking the stability of larger vessels it has to avoid heavy 46cm fire while pumping out its own heavy calibre fire. Often a single broadside will knock out its critical engines, forcing the ship off cushion. This turns the hovercraft in to a comparitively unstable, slow surface ship. 

This makes both ship types glass hammers, and opens up the door for a hybrid vessel that takes strengths from both classes to reduce some of the down sides. While still a fragile vessel, the hover-sub has a few tricks in its bags that will surprise a few players. 

How it Works

The hover sub is built like any normal hovercraft, 

1/7

designed to run fast and have lightweight, but heavy hitting

firepower. However, its density is in the 0.5 to 0.6 range, and it has angled blocks on the rear and carefully managed weight distribution to allow it to quickly submerge when it is thrown into reverse. Underwater torpedoes round out the package, allowing a skilled player to navigate the vessel underwater at between 40 and 60kts to launch a strike against superior vessels. 

Should the enemy vessel attempt to come in for a depth charge barrage, the hoversub quickly reverses power, popping to the surface and unleaching a heavy broadside, possibly using its quick acceleration to get a good firing angle, or popping back undewater to follow up with more torpedoes or mines. 

Armament

The hoversub is an incredibly fragile vessel, much more robust and forgiving than the average submarine, but still as fragile as a normal hovercraft. For this reason it must be given the best possible weapons to even the fight.

5" Mk45 gun

This will be your primary weapon. This is used like you would on any lightweigh ship such as a destroyer or cruiser, darting in and out and landing your hits strategically on the target whilst avoiding his heavy return fire. Attempting to destroy his engines and main armament should be your priority so that you can close and finish him off. Its also vital for fighting enemy air wings.

46cm battery 

The Mk45 is almost useless against 400mm and 600mm armour, chipping away so slowly that you could spend hours and not get anywhere. The 46cm gun is there to knock out critical enemy parts in a single volley so that you can finish the target with torpedoes or mines. 

Torpedoes

These are what make the vessel and without these the ship is useless underwater, and you might as well build a regular ship. Underwater torpedoes at least are a must, but oxy-torps and normal torpedoes also have their place. 

Mines and Depth charges

These are optionals, but nice to have nevertheless. Usefull for fighting other subs (which now will have a serious fight on their hands) and for limiting the mobility of tougher enemy vessels, these are decent game changers.

Harpoon Missiles

Usefull against slow, tough targets, these might allow you to use the other weapons more effectively. Also has a usefull side effect where they accidentally lock onto enemy fighters or torpedo bombers. 

Pros and Cons

Pros

1. Fast and agile surface vessel that can also be used as a submarine in a pinch. 
2. Doesn't have the usual downsides of submarines.
3. Choose to fight the engagement on your terms, using either speed or stealth.
4. Freaking cool!

Cons

1. Stability and toughness is still and issue.
2. Top heavy vessel, so a very unstable submarine - large rudder is a must.
3. Engines are your life - lose them and die. 
4. Difficult to build.
5. Difficult to use.

Building Guide

The Monitor - by LtSpiteful

This vessel is the "Monitor", named after the original USS Monitor from the US civil war, but actually taking inspiration from the coastal monitor destroyers and submarines that were supposed to have a low profile but heavy armament and named after the same.

The Monitor - Spiteful's HoverSub

 It is a feasibility study ship, and requires huge amounts of resources, so it's not for the beginner, but it's design is my gift to you, and I ask that any improvements to the ship or to the concept is posted here so that everyone can benefit from her design. 

She reaches a top speed of 125 kts on the surface and about 45-50 kts underwater. She's armed with 3 46cm cannons and powered by 3 Angled boilers and 4 large carrier boilers.

I'll demonstrate how to build her below.

The Base

Under the water she is similar to most hovercraft. There are 4 Large Carrier engines, a 1/2 hull angled skirt and 4 lift fans on the extreme edges. Lightweight 3*2*1 400mm armour make up the majority of the base. I've used 1/2 hull blocks on the back to allow it to submerge gently, and it also adds decent speed tweaking benefit. 

Weight Distribution

Here you can see the superstructure in which 3 Angled Boilers sit, the distribution of the 3 46cm guns and also the minor tweaks to the hull for better speed and diving ability. Notice the angled blocks on the front to push the tail down when the ship dives. 

The Front

Here you can see the greater detail of the front and the top. The small hull blocks are 600mm armour and the superstructure is 400mm armour. 

Due to the top heavy structure, a change from submerged to surface mode is tricky and best done rapidly, rather than gradually. 

Summary

This is a fun ship with heaps of potential, but its primary weakness: that of low stability, is likely to continue to hinder this class. While it would be interesting to track the progress of this vessel, it is unlikely to become common due to its difficulty in design and use.