Author Topic: Converting real naval warships to BT blue water ships  (Read 8712 times)

Cryhavok101

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Re: Converting real naval warships to BT blue water ships
« Reply #30 on: 24 June 2017, 18:02:35 »
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

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Re: Converting real naval warships to BT blue water ships
« Reply #31 on: 24 June 2017, 18:52:16 »
  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.
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kato

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Re: Converting real naval warships to BT blue water ships
« Reply #32 on: 24 June 2017, 20:37:47 »
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.
« Last Edit: 24 June 2017, 20:46:13 by kato »

Colt Ward

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Re: Converting real naval warships to BT blue water ships
« Reply #33 on: 24 June 2017, 23:22:51 »
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.
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Death by Lasers

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Re: Converting real naval warships to BT blue water ships
« Reply #34 on: 24 June 2017, 23:43:57 »
  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. 
“I do not love the bright sword for its sharpness, nor the arrow for its swiftness, nor the warrior for his glory. I love only that which they defend.”

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Death by Lasers

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Re: Converting real naval warships to BT blue water ships
« Reply #35 on: 24 June 2017, 23:47:16 »
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).
“I do not love the bright sword for its sharpness, nor the arrow for its swiftness, nor the warrior for his glory. I love only that which they defend.”

J.R.R Tolikien, The Two Towers

kato

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Re: Converting real naval warships to BT blue water ships
« Reply #36 on: 25 June 2017, 08:49:12 »
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

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Re: Converting real naval warships to BT blue water ships
« Reply #37 on: 25 June 2017, 16:47:29 »
  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 ::). 
“I do not love the bright sword for its sharpness, nor the arrow for its swiftness, nor the warrior for his glory. I love only that which they defend.”

J.R.R Tolikien, The Two Towers

mbear

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Re: Converting real naval warships to BT blue water ships
« Reply #38 on: 17 July 2017, 09:55:32 »
They don't even make Thunderbolts single shot.

Can't we use the one shot launcher and improved one-shot launcher for Thunderbolt missiles?
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Cryhavok101

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Re: Converting real naval warships to BT blue water ships
« Reply #39 on: 17 July 2017, 10:46:56 »
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
Quote
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
Quote
Improved One-Shot (I-OS) Missile Launchers function exactly as their standard counterparts

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

mbear

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Re: Converting real naval warships to BT blue water ships
« Reply #40 on: 18 July 2017, 07:03:03 »
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.
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Empyrus

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Re: Converting real naval warships to BT blue water ships
« Reply #41 on: 18 July 2017, 17:39:26 »
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.
« Last Edit: 18 July 2017, 17:46:57 by Empyrus »

Colt Ward

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Re: Converting real naval warships to BT blue water ships
« Reply #42 on: 18 July 2017, 18:03:23 »
Heck, I would love OS Cap and SubCap missiles . . . or Cruise Missiles, which IIRC another topic do not exist.
Colt Ward
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Cryhavok101

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Re: Converting real naval warships to BT blue water ships
« Reply #43 on: 18 July 2017, 18:38:03 »
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

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Re: Converting real naval warships to BT blue water ships
« Reply #44 on: 18 July 2017, 21:14:10 »
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

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Re: Converting real naval warships to BT blue water ships
« Reply #45 on: 18 July 2017, 22:45:06 »
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

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Re: Converting real naval warships to BT blue water ships
« Reply #46 on: 18 July 2017, 22:48:01 »
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.