Converting real naval warships to BT blue water ships

[Colt Ward]

We have a few examples of BT surface ships (Luftenburg CV, Jormungand BC, Meabh CA, Rapier DG, Andryusha DD, Cliona FF/G and Wakmiya amphib?) though most are parked with the Lyrans the fluff hints at more as appropriate for water or important worlds.  We had warships in the MW4 games though they are not canon its something to ponder- I want to say it was the Thunderchild but I will have to go back and inspect them.  I would say they were corvettes or maybe frigates based on their weapons.

But we also have a lot of interesting warships in various navies designed since WWII which would be some interesting inspiration for conversion to BT ships . . . but which would reflect each House?  Leave aside the 'Davions are Brits/French' bit and just go with the design aspects.  Heck based on the limited ships we do see, what would the construction doctrines for the Houses be?  Can they also be reflecting in the black water naval design?

Since we have so many Lyran ships . . . and for the most part are the largest ships . . . I would say they will fall in line with their mech and space warship design- biggest around, load up on guns & armor and go for a extreme quality angle.  Not sure what IRL designs might compare, but IMO it would be cutting edge for the time . . . like Aegis cruisers & US supercarriers.

I would swing it the other direction for Drac ships . . . generalist budget ships, which seemed to be what they did with their space warships too.  Though occasionally they will spend for capabilities like Lysander CV sub.  Honestly I think here it might be appropriate to duplicate old Soviet designs specs (not performance . . . though maybe) looking at things like not using DHS & MRMs.


Also, what would weapons convert as?

For example, what do 16 inch main guns convert as?

ASROC torpedo launchers?

[Giovanni Blasini]

I don't think we have anything equivalent to a 16" gun, but a Long Tom makes a good equivalent to an 8" gun.  With that in mind, I'd probably treat 6" guns as Snipers and 5" guns as Thumpers.

ASROC....is there an Arrow IV torpedo?  That seems the closest equivalent.  Cruise missiles are cruise missiles , of course.

The biggest issues I see is the lack of a VLS equivalent.  While Arrow IVs can cover the majority of missile roles on modern ships thanks to the variety of munitions, including air defense, surface attack, etc., modern warships depend heavily on being able to throw massive throw weight in a single volley, which a Battletech surface warship can't do.

[YingJanshi]

Are the larger vessels able to mount sub-capital weapons? Or would that have to be on something using the mobile structure rules?

[Colt Ward]

AFAIK surface vessels that do not use combat vehicle rules (I think they are up to 500t) are considered mobile structures and can mount Subcaps . . . which is why I was pondering the heavy subcap AC being a 16 inch, med 14 inch and light 12 inch.  Long Toms & other standard types are smaller caliber guns.

One thread down in the design talked about CMs being different since the launcher & missile weights are much larger than current- but it could be done.  They would also be VLS . . . and VLS is a creation of the late 70s?  I was looking at the Moskva cruiser and thinking it was basically a A4 launcher or two with a single ton of ammo for the launcher.

[Death by Lasers]

  You can make some really cool warships with the TACOPS large naval vessel construction rules.  However, I've found one major issue with constructing RL ships.  The rules don't factor in the real life fuel efficiencies and (relatively) small engines that ships traveling at low speeds have so you have to have spend ridiculous amounts of tonnage on fuel and your engine for large ships.  For this reason it's virtually impossible to make a true to form victory ship or any other cargo vessel.

   In real life ships can get away with proportionally very small engines and extremely high levels of fuel efficiency if they are not concerned with going above 30 knots or so but Btech ships follow the same speed/weight curve that ground vehicles do meaning that the require very large engines and huge fuel reserves. 

  This doesn't stop you from making some pretty cool warships or decent btech approximations of real life vessels but it limits your ability to accurate conversions like you can mostly pull off with ground vehicles.

[Colt Ward]

Hmm, down on the design forums I had someone who did the ships actually make me a Liberty ship and presented two versions.  I kept the info as they filled out BTU IMO and I have already used them in fluff.  The conversation DID get rather involved with fuel range.

Of course for combat ships, XL, LFE and SFE engines for the designs would cut the fuel problems along with providing power.

[mbear]

  You can make some really cool warships with the TACOPS large naval vessel construction rules.  However, I've found one major issue with constructing RL ships.  The rules don't factor in the real life fuel efficiencies and (relatively) small engines that ships traveling at low speeds have so you have to have spend ridiculous amounts of tonnage on fuel and your engine for large ships.  For this reason it's virtually impossible to make a true to form victory ship or any other cargo vessel.

What about the compact fusion engine? Would that help?

The big issue I see is that BT only allows one engine at all. A lot of naval ships use combined engine systems where they pair a diesel engine for slow speed operation and a gas turbine for high speed sprint speeds.* I suppose you could house rule it, but at the moment the best you could do would be to add a supercharger to an engine to simulate this powertrain setup.

Regarding the VLS equivalent remember that the SturmFeur artwork and fluff says that one of the LRM-20s is actually in a vertical configuration. The Clanner's Mars has the same thing for its LRM-20s so putting a missile launcher at 90 degrees isn't really hard. I'd personally suggest the Extended LRMs for their range, but that's just me.

Also remember that current VLS systems can use a variety of missile types: You'd need a missile launcher that could fire cruise missiles (Tomahawk/Storm Shadow), Arrow IVs (Harpoon/Exocet/Standard missiles), AA Missiles (ESSM), and Light AA Missiles (Quad-packed ESSM) at least. The nearest thing I can think of is the AR-10** used by WarShips. I suppose an MML/ATM could work for the smaller stuff, but they're probably filling the role of the Rolling Airframe Missile. And this still doesn't provide an anti-sub capability. (Note to self: Look into creating "Sea Thunder" LRM munitions that lay a minefield in BT ocean hexes.)

*Not that anyone cares but there are other types of combined engine trains in ships. CODAG, CODOG, etc.

**researching the answer to your question helped me understand how the various WarShip missile launchers like the AR-10 could work, so thanks for that. Here's the relevant passage from the WikiPedia page.

Mk 41 VLS adopts modular design concept, which result in different versions that vary in size and weight due to different "canisters" in various modules. The height (missile length) of the launcher comes in three sizes: 209 inches (5.3 m) for the self-defense version, 266 inches (6.8 m) for the tactical version, and 303 inches (7.7 m) for the strike version.

In my head the Barracuda, Killer Whale, etc. launchers correspond to these dimensions. Barracuda = Self Defense, Killer Whale = Tactical, AR-10 = Strike.

[Cryhavok101]

You can mount subcapital weapons on large naval support vehicles. However except for missiles the rules don't allow subcapital weapons mounted on a non-airborne unit to fire at another non-airborne unit, so they would be no good against other ships, 'Mechs, etc. They would work great against spaceships though.

If you don't mind going somewhat slow, support vehicles can have much smaller engines than the equivalent combat vehicle, because they use entirely different rules to figure out their engine weights, and don't have to match up with the standardized engine ratings other unit types use. I have no idea how well the ration matches up with reality, but it might be closer than any combat vehicle could get.

[Death by Lasers]

  Nah, I've tried to make large naval vessels using the construction rules and they are very different than real life.  For example a 70,000 ton Panamax ship carries 1.5 million gallons of fuel, cruises at 25 knots, and burns 175 tons of fuel a day at that speed in its (crudely estimated from the three times larger Emma Mearsk's 2300 ton Engine) 800 ton engine.  You can't approach anything like this in Battletech as the example below shows a Btech large naval vessel trying to match the stats of a real life cargo vessel and quickly becoming overweight.

               RL Panamax     Btech Panamax (C-Tech ICE engine)
Weight     70,000 tons      70,0000 tons
Speed      4/6                  4/6
Engine     800 tons (est.)  25,200 tons
Fuel         4,200 tons        66,780 tons
Range      26,496 km        26,500 km

[Cryhavok101]

Ah I see what you are saying. I was thinking in terms of modern navy ships, and thinking of using higher tech engines for battletech versions of them. They still don't get quite as light as that engine, but the higher tech ones do make the ratios a lot closer. Also I have to point out that the wiki article on it does give the weight of the main engine, but the propeller shaft also has five more diesel generators, and 2 electric motors powering it. It has a steam turbine that takes a lot of the engine's exhaust and recycles it into more power as well, along with associated electric motors.

Also, Battletech as far as I understand it, would also be including the weight of the propellers and all the other machinery working to propel the ship forward in it's abstract "Engine weight", which would account for some of the disparity.

That fuel efficiency difference sucks though. I have no explanation for that.

A C tech rating Fuel Cell engine that goes 3-5 would be 8736 tons, and the fuel for that 34,725.6, with a super charger adding another 873.6 tons. That is much closer tot he other's engine weight, though even that is ten times the weight.

In terms of modern navy ships, my biggest beef with the current rules is the how they determine the available space. You can remake WWII ships alright, but recreating 21st century ships becomes more difficult because you have the tonnage, but lack the space to recreate them.

[Colt Ward]

Well . . . some of its going to come down to abstracting weapons instead of a 1 for 1 exchange.  The other would be realizing the 'cruise' missiles are more like SCUDs than Tomahawk or ATACMs for size, accuracy and damage.  Same sort of deal might apply for for single, double or triple gun turrets.

And while the rules do not say they can use SubCap weapons, IMO it would be logical . . . just like I would say they could use the lightest NAC which might be comparable to the largest cannons ever made.  Missiles, easily . . . naval gauss would get interesting.

Their role, as discussed in other threads would IMO be mobile fire support for ground forces as well as interdiction & orbital control.  Some of the conversation came down to do you want a single supership (like the LCAF's Luftenburg) or perhaps smaller ships mounting a single mid-sized SubCap missile launcher to take shots at Dropships?  Sure the smaller ship is easier to sink . . . but its also easier to hide and with it costing less can be spread around on more worlds.  Or if you took the Davion approach with the Rapier DDGs, you can transport them in to help defend your LZ.

[Cryhavok101]

And while the rules do not say they can use SubCap weapons

Actually the rules do say they can be.

TO pg 343 lists the two letter codes for each unit type that can use the item. The item in question, subcapital weapons, lists SV, as in support vehicles. The entry does not restrict that to only satellites. The chart on page 411 reinforces this giving the space it takes to mount each sub capital weapon on a support vehicle.

I have never seen any restriction for the type of support vehicle they can be mounted on anywhere, so the rules allow them to be mounted on any SV that has the required weight and space.

Well . . . some of its going to come down to abstracting weapons instead of a 1 for 1 exchange. 

I was looking at the AA VLS systems on frigates and wanting to put that many arrow IVs on instead, but there is no way to enough on to engage the same number of aircraft as our modern destroyers do.

[Colt Ward]

Sorry, let me be clear . . . I meant the rules does not say they can target other surface objects- missiles are the only thing capable of S-S modes.

[Cryhavok101]

Ah yes, true, my apologies for the misunderstanding.

[Death by Lasers]

  Good point on Btech including propellors, etc., in engine weight.  Still, even throwing all that in when include all the structures, engines, etc. the Panamax has more than 50,000 tons of Dead Weight Tonnage for fuel and cargo meaning the engine plus structure weight is no more than 20,000 tons.  The heart of the issue with fuel efficiency is that the engines are too heavy for slow moving ships and fuel use is based on engine weight.  With ships the efficiency curve goes down very steeply when you add speed.  To represent this better I would give ships a very low Base Engine Factor but also a steeper Movement Factor formula, something along the lines of X+Cruising Speed^3 rather than X+Cruising Speed^2 as it is done with land vehicles.

  Moving on to representing weapon systems we have some good weapons to choose from.  The neat thing about the weapons choice for making Btech warships is that they actually work pretty decently for modern weapons systems.  For ship-to-air or ship-to-ship guided missiles you have Capital and Sub-Capital missiles, and for Cruise Missiles you have... Cruise Missiles.  You also have Long Toms for 8" guns and Arrow-IV missiles for smaller ordinance.  Although admittedly Btech missiles are huge, for example a Piranha Sub-Capital missile weighs 10 tons versus a real life 1.6 ton Tomahawk missile.  A 200kg Arrow-IV missile is probably a closer representation but I honestly can't think of anything between 1 and 10 tons in Btech's missile inventory.  Still, they work well enough to make some decent representations.

  The rules aren't as good for WWII like warships since we have nothing to represent the big guns as we have been discussing.  What you could do is substitute Cruise Missiles for heavy artillery.  A Cruise Missile/120 is for all intents and purposes a 16" (or larger maybe larger :D) gun rules wise.  The launcher is light and the ammo is heavy but Cruise Missiles are virtually identical in function to dumb fired artillery shells in the Btech rules.

[Cryhavok101]

Interesting fact, the Japanese battleship Yamato had 200ish ton main guns, so if we could point them at other surface ships, subcapital weapons would work great there.

[Giovanni Blasini]

Wiki lists the Yamato's guns at 147.3 tons, whereas a light subcapital cannon is 200 tons.  A light SCC seems like you'd be pushing your luck, at a full 33% bigger than anything ever fielded in real life, and bigger SCCs seem looney tunes.

As for the one mention of an NAC, the NAC/10 is 2000 tons, or close to the standard load of a Fletcher class destroyer. The entire destroyer.

[Death by Lasers]

  A Cruise Missile/120 would be a good approximation of a 16" gun at 135 tons.  Well, sort of, the ammo for the CM/120 is 60 tons per shot while the 16" shells are about 3 tons each IIRC.  Still, fluff aside they are functionally very alike, they have similar ranges with CM/120 at 60km and the Iowa at 40km.  I started trying to make a Battleship using Cruise Missiles only to realize their are some pretty strict space caps that keep from putting more than 5 CM/120s on a 60k ton ship.  Still, might keep working with it to see what kind of monster I could make.

Edit: Subcapital missiles might be a better choice.  You can put nine on your Battleship for 225 space slots with each launcher weighing 120 tons and each missile 12 tons.  Sure it's technically a missile launcher but just think of it like a Gyrojet cannon ;)

[Cryhavok101]

Wiki lists the Yamato's guns at 147.3 tons, whereas a light subcapital cannon is 200 tons.  A light SCC seems like you'd be pushing your luck, at a full 33% bigger than anything ever fielded in real life, and bigger SCCs seem looney tunes.

As for the one mention of an NAC, the NAC/10 is 2000 tons, or close to the standard load of a Fletcher class destroyer. The entire destroyer.

I had known they matched up with SCL/1s fairly well, I just got their weight mixed up, and should have checked before posting. Sorry about that.

[Colt Ward]

Well, the thing I could not find for the 'gun' weight . . . I think its JUST the tube.  Because when I find the weights it gives one with and one without the breech.  Which means its not taking into account any of the other weight in the turret . . . BT weapons lump in all the power & targeting feeds, ammunition feed and traversing/elevation mechanisms into a single weight.  So yeah, the gun tube with breech comes in at 171 tons IIRC for a Iowa.

I still think current Cruise Missiles are more like SCUDs than Tomahawks.  One thing with some warship armaments is you have a few designs that have external missile launchers that are single shot- and we unfortunately do not have A4, CM or SC Missile single shot launchers yet.

[Cryhavok101]

They don't even make Thunderbolts single shot.

[Daryk]

Now that's an idea crying out for a house rule...

[kato]

For example a 70,000 ton Panamax ship carries 1.5 million gallons of fuel, cruises at 25 knots...

That would be better modeled with a 3/5 engine, not a 4/6 engine. It's not like that Panamax ship is capable of a top speed of 35 knots. With a 3/5 the same design would be about 32,000 tons lighter.

[Cryhavok101]

Another thing to consider is that real world cargo ships that size don't accelerate to full speed in a matter of seconds either.

[YingJanshi]

Another thing to consider is that real world cargo ships that size don't accelerate to full speed in a matter of seconds either.

That would be fun to watch...  [watch]
(Wouldn't want to actually be in or on said vessel at the time though...)

[truetanker]

I don't think the rules say you can't make Sea Mine T-Aug missiles.

Just that you should mark the RS with what type of mine ammo.

TT

[Death by Lasers]

That would be better modeled with a 3/5 engine, not a 4/6 engine. It's not like that Panamax ship is capable of a top speed of 35 knots. With a 3/5 the same design would be about 32,000 tons lighter.

  You still wouldn't save very much weight though since you have to go at flank speed to match the 25 knots cruising speed and per the TechManual every velocity point of flank speed costs twice the fuel as cruising speed.  However, because of the lighter engine you still have a net efficiency gain of 5% so a 3/5 engine would be a better choice but you aren't saving 32,000 tons.  Even with the smaller engine we still are off by an order of magnitude when compared to real ship engine weights and fuel efficiencies.

  The problem is that mathematically Btech models ships like ground vehicles.  A 70,000 ton cargoship is treated like a giant 18 wheeler even though in real life a typical cargoship gets about 514 mile-tons per gallon of fuel while an 18 wheeler gets 59 mile-tons per gallon.  Ships get huge fuel efficiency savings for traveling slow orders of magnitude beyond what you can achieve with a ground vehicle.  For example if our Panamax was traveling at 18 knots (Btech speed 3) it would burn 55 tons per day versus 175 tons per day at 25 knots (Btech speed 4).  Trucks can save a little fuel by cruising slower but not on this order of magnitude.

Another thing to consider is that real world cargo ships that size don't accelerate to full speed in a matter of seconds either.

  In fairness neither can Battletech large ships.  They can only add or subtract one velocity per turn so it would take a full minute for our ship to come to full speed.  I know at full reverse a real life cargo vessel will take five miles to come to a halt versus 700 meters for our Btech Panamax so you are still ultimately right but I thought I would point that out.

[kato]

  The problem is that mathematically Btech models ships like ground vehicles.

That's more a problem with the ICE engines themselves. Ground vehicles - especially when you get into small support vehicles - instead get ridiculously mileage out of their fuel on ICE compared to reality, and that with "realistic" engine weights; for Tech Level C "cars" of around 1 ton with a 7/11 engine run somewhere around 150 mpg at their 75 km/h cruise speed.

Perhaps applying a factor comparable to what's done for the final cost calculation could fix this somewhat in both cases. The (1+(tonnage/x)) factor, with different x variables depending on type of vehicle and motive system. Though working out that variable for various vehicles isn't something i'd want to do.

[Cryhavok101]

  You still wouldn't save very much weight though since you have to go at flank speed to match the 25 knots cruising speed and per the TechManual every velocity point of flank speed costs twice the fuel as cruising speed.  However, because of the lighter engine you still have a net efficiency gain of 5% so a 3/5 engine would be a better choice but you aren't saving 32,000 tons.  Even with the smaller engine we still are off by an order of magnitude when compared to real ship engine weights and fuel efficiencies.

Can you point me towards where it says large naval support vehicles use fuel points? They certainly aren't assigned any during construction. I know aerospace units follow that rule including the airborne support vehicles, but naval units don't even use velocity, much less fuel points as far as I can tell. Their fuel is calculated based on range, so lowering to a smaller engine would lower the fuel needed as well whether you are using flank speed or not. So far I have only seen stuff about aircraft using more fuel at max thrust, so I could use a page number for this if you can find it.

  In fairness neither can Battletech large ships.  They can only add or subtract one velocity per turn so it would take a full minute for our ship to come to full speed.  I know at full reverse a real life cargo vessel will take five miles to come to a halt versus 700 meters for our Btech Panamax so you are still ultimately right but I thought I would point that out.

Ah I forgot that, thanks for the correction. Still, a minute to speed up to 35 Knots, vs a lot longer for a real world ship the same size.

[Death by Lasers]

Can you point me towards where it says large naval support vehicles use fuel points?

  Turns out it was in StratOps, my bad.  On page 35 under the section for support vehicle fuel consumption: "All fuel consumption rates are for Cruising movement rates; the rate of consumption is double at Flanking speed".

[Cryhavok101]

Thanks for finding that, just read that, and the only fuel consumption rates it mentions are battle/search and rescue, which costs 500 km of fuel, and maintenance/repair cycle, which costs 50 km of fuel. It says nothing about general travel. That paragraph is poorly worded and ambiguous in my opinion, however I won't dispute it here, because:

3/5 is still more accurate than 4/6 as a speed, because even in the real world, cargo ships don't travel at top speed. They save fuel by travelling quite a bit slower. It saves the companies in real life a ton of money on fuel and the longer travel times are still financially worth it.

Based on that, I would say 25 knots is the Emma Maerk's flank speed, which you would get closest to with a 3-5 engine, or better yet, we could go with a 2-3 engine and a super charger for just slightly slower at 22 knots top speed. For this theoretical 70,000 ton ship, that 2-3 engine would come out to 10,080 tons, and fuel for it would be 26,712 tons. The super charger would be 1,008 tons. At cruising speed it would be going ~12 knots which is what currently our cargo ships are doing for long distances.

[Death by Lasers]

  Yeah but then you would need to increase the fuel range because a real life Panamax is only burning 55 tons a day at 18 knots (versus 175 at 25 knots).  Even cruising at 2 we still are still spending 26,000 tons of fuel to move a 70,000 ton vessel 26,000 kilometers versus a real Panamax's ability to make that distance cruising at speed 4 with under 5,000 tons of fuel.  We are looking at half the speed for five times the fuel cost.

  I have fudged around with the rules in the past to try and make a cargo ship close to reality but I've come up short.  For example you could use the naval tug rules that allow a vessel to tow/push five times its weight and assume the total range is unchanged because you are moving at reduced speed.  This way you could break a Panamax into a tug and cargo components and make a 12,000 ton tug to tow/push a 60,000 ton trailer for our 70,000 ton vessel.  It's better but still a lot less fuel efficient than a real ship and your cruising speed is effectively capped at 2 (10 knots) if you want to have room for fuel for the tug.  You can also use mobile structure architecture to make a cargo vessel.  I honestly don't remember how well they performed but I think they were still not very fuel efficient compared to real life vessels.  They are also capped at cruising at 2 (or 3?).

  For warship construction though I'm starting to realize it doesn't make a huge difference do to the space caps built into the system.  It's hard to put much more than 1,000 tons of guns on 60,000 ton warship given its 635 units of space.  The Luftenburg and the Jormagund work pretty decently a Carrier and Warship despite the fact that the rules require them to have bloated engines or be made mostly of fuel (actually, given the Jormagunds staggering 55 knots speed it probably would require a gargantuan engine to replicate IRL).  You can even deck them out with a heavy payload of subcap weapons (that have great space to tonnage ratios) and only use 5,000 tons of the ships weight.

[kato]

You can also use mobile structure architecture to make a cargo vessel.  I honestly don't remember how well they performed but I think they were still not very fuel efficient compared to real life vessels.  They are also capped at cruising at 2 (or 3?).

You're capped to 4 MP for naval mobile structures. And their fuel efficiency is utterly ridiculously good.

Emulating a Template E (>30.000t) Tech Level C large naval support vessel, you'd get a 6-level, 9-hex mobile structure. Now setting both at 4 MP with ICE engines:

- the large naval support vessel (depending on size) requires between 10,800.5 t at the lower end and 36,000 t at the upper end for the engine.
- the mobile structure requires ICE engines of 648 tons for the power system.

Note that at lower speeds the margin is less, since for the naval vessel it scales virtually exponentially.

One day of travel at full speed (=23.3 knots), i.e. 1036.8 km, costs the large naval support vessel 1119.8 to 3732.5 tons fuel; the same for the mobile structure would be 134.4 tons.
For the mobile structure this is in line and rather favourable in comparison with current ships - which burn around 140-150t per day at that high speed.

However for cargo, mobile structures are rather bad:
- The large naval support vessel comes with a deadweight of between 13,334.5 t (for a 30,000.5t vessel) and 44,450 t (for a 100,000t vessel)
- The mobile structure comes at maximum (CF150 fortress) with a deadweight of 7357.5 t

The remaining deadweight of a mobile structure with fuel loaded is lower than that of a naval vessel as long as the desired range is less than 6288 km / 3395 nm (in comparison to 30,000.5t -> 6,542t remain) to 10688 km / 5771 nm (in comparison to 100,000t -> 5,971t remain).

P.S.: A naval mobile structure of that size is physically capped to a maximum mass of somewhere around 127,500 tons due to its water displacement, and for that it'd need a relatively odd shape filling all hexes.

[Colt Ward]

Really?  B/c the set up for the Jormungand is 6/9 . . . which is a bit faster than a max speed of 4 moving its 60kt.  The Meabh at 10kt is 8/12 . . . even the Luftenburg is 3/5 with its 100kt hull.  The Rapier DDG is 5/8 which is interesting since during the FCCW one could have been chased down by a Jormungand . . . with unfortunate results for the Rapier.

[Death by Lasers]

  Are you sure about that.  After reading your post I tried to make a Panamax using the mobile structure rules and got something with hideous gas-mileage.

Type: Hangar (25 CF per Hex, 75 ton Capacity with 300 ton max per 4 four levels)
Size: Four 13 Level by 15 Hex interconnected segments (58,500 ton capacity, ironically can't fit through Panama canal)
Power System: 195 Hexes per segment x 3 MP (Max for surface vessels) x 3 ICE Engine = 1755 tons per segment or 7,020 tons for the whole vessel.
Motive System: 195 Hexes per segment x 2 Naval x .3 Hangar = 351 tons per segment or 1404 tons for the whole vessel.
Fuel Weight: 260 Hundred Kilometers x 0.02 ICE x 1755 ton Engine = 9,125 tons of Fuel or 36,500 tons for the whole vessel.

  From these calculations it would take our Mobile Structure Panamax 36,500 tons of fuel to cruise 26,000 kilometers at speed 3 versus under 5,000 tons of fuel for the real ship to cruise at speed 4. 

[Death by Lasers]

Really?  B/c the set up for the Jormungand is 6/9 . . . which is a bit faster than a max speed of 4 moving its 60kt.  The Meabh at 10kt is 8/12 . . . even the Luftenburg is 3/5 with its 100kt hull.  The Rapier DDG is 5/8 which is interesting since during the FCCW one could have been chased down by a Jormungand . . . with unfortunate results for the Rapier.

  The Jormungand uses the naval vessel construction rules.  You can also make a naval vessel as a mobile structure which limits you to a max speed of 4 for submersibles and 3 for surface vessels (maybe 4 for surface vessels also, the table is ambigious).

[kato]

Are you sure about that.  After reading your post I tried to make a Panamax using the mobile structure rules and got something with hideous gas-mileage.

Hangars look good on paper, but actually have for given CF ranges above a certain size they have the worst deadweight ratio. Since the fuel usage is fixed at (0.0002 * power system multiplier * MP * hexes * levels) per km only the deadweight per hex is decisive.

Ran it through a rather nasty Excel spreadsheet just now. Basically, if your target numbers are 25,000 km range and 50,000+ tons net payload then to put it in a single mobile structure you need a CF150 fortress. No way around it. For singular mobile structures with that range given, the maximum payload is 56,400 tons for a surface vessel (for 3 MP) or 45,600 tons for a submersible (for 4 MP). In either case CF150 fortresses at 20 hexes and 30 levels.

If combining multiple structures you should go down to 19 hexes for better alignment and accomodate 450 tons in linkage , thus yielding 53,130 tons per structure for a surface vessel and 42,870 tons for a submersible.

If you want to think a bit bigger, the net payload yield for covering the 250 square miles water of the panama canal in a linked mobile structure array would be about 43.39 billion tons for surface vessels and 35.01 billion tons for submersibles. If we dredged it to 90+ m depth first ;)

[Death by Lasers]

  Ah, I see, mobile Fortresses are a lot more fuel efficient.  I got much better but not quite good fuel efficiencies with your construction.  I made a 54,000 ton capacity Fortress ship but it still needed about 17,000 tons of fuel to make 26,000km at speed 3.  Still, a real ship of that capacity can make it at speed 4 and burn only about 5,000 tons of fuel and if moving at speed 3 they would need only 1,600 tons of fuel if traveling at speed 3.  However, this is much better than standard naval construction that costs you 43,000 tons of fuel for the same range and speed.

  It would work if we could say that the ship has max acceleration of 1MP per turn but can build that up to a cruising speed of 4 if traveling over great distances.  This would give a container vessel with 1MP move, 5,000 tons of fuel, and a cruise of 4, and the same 26,000km range.  However, this is just changing the fluff/rules on my part ::). 

[mbear]

They don't even make Thunderbolts single shot.

Can't we use the one shot launcher and improved one-shot launcher for Thunderbolt missiles?

[Cryhavok101]

Can't we use the one shot launcher and improved one-shot launcher for Thunderbolt missiles?

Nope, those specifically state what launchers they can be used with.

TechManual pg 230

A variation on the LRM, MRM and SRM systems (including Streak launchers, torpedo launchers and even the Narc missile beacon launcher) the single-shot launcher—also known as one-shot or OS—is a curious concept that did not so much go extinct in the Succession Wars as fall into general disuse.

TacOps pg 327

Improved One-Shot (I-OS) Missile Launchers function exactly as their standard counterparts

Though I admit, my interpretation of that could be wrong.

[mbear]

Nope, those specifically state what launchers they can be used with.

TechManual pg 230
TacOps pg 327
Though I admit, my interpretation of that could be wrong.

Well, I think that's going to get a house rule.

[Empyrus]

SSW has one-shot T-bolts. I'd check MegaMekLab but i seem to have deleted it. (MML usually has stuff based on errata'd and official rules so it should be reasonably reliable for checking stuff like this.)
I'm not 100% but i think errata made OS and iOS available to all missile weapons, including T-bolts (but not 'Mech mortars, which aren't really missile weapons).

EDIT TM won't mention any special missiles because it only lists those in it. Logically there is no reason to limit OS ability to specific missiles and leave out some like T-bolts. And if T-bolts are left out, then so are ELRMs and other such, because they're not explicitly mentioned anywhere.

[Colt Ward]

Heck, I would love OS Cap and SubCap missiles . . . or Cruise Missiles, which IIRC another topic do not exist.

[Cryhavok101]

I'm not 100% but i think errata made OS and iOS available to all missile weapons, including T-bolts (but not 'Mech mortars, which aren't really missile weapons).

If you find it I'd love to be pointed towards it.

EDIT TM won't mention any special missiles because it only lists those in it. Logically there is no reason to limit OS ability to specific missiles and leave out some like T-bolts. And if T-bolts are left out, then so are ELRMs and other such, because they're not explicitly mentioned anywhere.

I agree, I think if they can do it with one missile launcher, they should be able to do it with any. Hell, they should probably be able to do it with Ballistic weapons too, since the ammo feed isn't exactly necessary to fire a weapon once. It seemed odd to me when I found it. I didn't generally pay it much mind until I stumbled across it making sure I could do one shot MMLs. I don't generally use OS stuff beyond rocket launchers and some SRMs.

[Empyrus]

Hell, they should probably be able to do it with Ballistic weapons too, since the ammo feed isn't exactly necessary to fire a weapon once.

Pretty sure the rules do limit the effect for missile weapons. And technically this might cover 'Mech Mortars...

Realistically, yes, you should be able to create one-shot ballistic weapons... but why would you?

Hrm, may need to do a rules question about this, if there isn't one already...

[Cryhavok101]

Realistically, yes, you should be able to create one-shot ballistic weapons... but why would you?

I ask the same about most missile weapons honestly lol. There are few things worth making one shot. As to why I might: some attempt to recreate civil war era iron clads that had to reload their weapons by hand. Can't think of any reason to do it in the modern battletech era of course, but with retrotech becoming a thing, I could see it get put to use when you are going all out on the primitive tech. I'd certainly never do it on a mech, since they don't have a crew to be reloading the guns manually with.

[Cryhavok101]

Back on the topic of recreating real naval warships, if any of you are interested in messing around with it, I just posted my first decent version of my support vehicle calcculator here: http://bg.battletech.com/forums/index.php?topic=58085.0

It can do the large naval ships, so feel free to use it to recreate modern ships. If you have any problems with it or need anything explains, PM me or ask in the thread there. The example is the Large Naval support vehicle I posted a few days ago. I hope some of you find it useful.