|
|
Post by jorgencab on Jun 10, 2019 16:34:49 GMT -6
I do have problem with creating really high speed ships as they were historically constructed such as say the Omaha class of fast cruisers and the like. Even when you add all the option of low freeboard, narrow belt armour, speed focused engines and cramped spaces... the Omaha basically ticked all those boxes... but you really don't save weight enough for an extra knot or two. You can't even build the Omaha at mid 30 technologies let alone in mid 20 as it was historically built. Even if I reduce the 35 designed knots to more reasonable 32 knots I can't build it as it was historically built.
It seem like small ships really have problem to be fast even with little to no armour and all the weight saving options possible in the game.
Any help for building say a destroyer flotilla leader type cruiser that are relatively historical with the game mechanics or should there be some balancing done perhaps?
|
|
|
|
Post by jorgencab on Jun 10, 2019 18:11:15 GMT -6
I will add some more info to my question here from investigations I have done... I think that some of these problem stem from the way that machinery grow in weight in relation to Horsepower the engine delivers. I mean not only will a larger ship require less Horsepower per ton as it grow the engine deliver less Horsepower as it grow in size which I think from my calculation are too restrictive from reality. Sure it is and was an engineering feat to fit more engines and boilers into a ship but having three or four boilers and all the other machinery would not grow so inefficient with the horsepower as it seem to do in the game. Another thing is the deck armour. It seem to be a bit too heavy for for the protected cruiser variant. The deck armour are only suppose to be the flat portion of the deck which is way smaller than in the Flat deck on top of belt version. In a 4000t Light protected cruiser (1900 start) I must put 1" of deck armour at a weight of 398t versus 434t on a Flat deck on top ship. This is not including the sloped areas. Another 1" of the sloped deck (belt armour) we get an additional 146t for the total weight of the deck. I'm not an expert enough on the geometry of the ships but you "must" put allot of armour on these small light cruisers where that often only had perhaps half an inch of flat deck armour in many cases for allot less weight. So there are two things which heavily restrict me building really fast small cruisers... one is the design of the hull itself. A cruiser built for speed should be an option where you get more speed per HP from that of a "normal" cruiser in the same way you get on a destroyer. Perhaps the light cruiser hull type should in general be able to get more speed per HP per ton of weight of the ship to differentiate a bit more between the sacrifices between the two ship types of armoured cruiser and light cruiser hull types. The draw backs should obviously be worse sea keeping (more penalties to accuracy for guns as they are less of a stable platform) in bad weather like that of destroyers. Or at least make it a design choice for light cruiser hull type. Thus I could build a cruiser that can keep up with destroyer speed if a want to. The sleeker more speed favoured hull type of a cruiser should give you some speed advantages over the more stable battleship type platform in relation to HP to displacement tonnage ratio. Currently the game seem to rate battleship hullform to require as much HP per displacement tonnage as that of a sleeker cruiser hull of similar weight. Found some simple and quite informative stuff here... www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/s/ship-shapes-anatomy-and-types-of-naval-vessels.html |
|
|
|
Post by archelaos on Jun 11, 2019 0:52:58 GMT -6
I do have problem with creating really high speed ships as they were historically constructed such as say the Omaha class of fast cruisers and the like. Even when you add all the option of low freeboard, narrow belt armour, speed focused engines and cramped spaces... the Omaha basically ticked all those boxes... but you really don't save weight enough for an extra knot or two. You can't even build the Omaha at mid 30 technologies let alone in mid 20 as it was historically built. Even if I reduce the 35 designed knots to more reasonable 32 knots I can't build it as it was historically built. It seem like small ships really have problem to be fast even with little to no armour and all the weight saving options possible in the game. Any help for building say a destroyer flotilla leader type cruiser that are relatively historical with the game mechanics or should there be some balancing done perhaps?
The calculations in game work on averages, so they can't take into account extreme cases. Omahas were very lightly built which already skew the calculations, but they were also overweight.
Then we reach major question - is game displacement short or long tons? Is it standard, normal or full? Omahas were 9500t full, and you can easily build 9500t CL in game that has all the major features of Omaha-class... except you can't build CLs bigger than 8000t before 1928. But even on 8000 you can get nice representation of Omaha IMHO:
|
|
|
|
Post by stevethecat on Jun 11, 2019 1:03:22 GMT -6
The game doesn't have Transom sterns either and those typically helped ships gain a knot or two.
|
|
|
|
Post by jorgencab on Jun 11, 2019 3:53:19 GMT -6
I do have problem with creating really high speed ships as they were historically constructed such as say the Omaha class of fast cruisers and the like. Even when you add all the option of low freeboard, narrow belt armour, speed focused engines and cramped spaces... the Omaha basically ticked all those boxes... but you really don't save weight enough for an extra knot or two. You can't even build the Omaha at mid 30 technologies let alone in mid 20 as it was historically built. Even if I reduce the 35 designed knots to more reasonable 32 knots I can't build it as it was historically built. It seem like small ships really have problem to be fast even with little to no armour and all the weight saving options possible in the game. Any help for building say a destroyer flotilla leader type cruiser that are relatively historical with the game mechanics or should there be some balancing done perhaps?
The calculations in game work on averages, so they can't take into account extreme cases. Omahas were very lightly built which already skew the calculations, but they were also overweight.
Then we reach major question - is game displacement short or long tons? Is it standard, normal or full? Omahas were 9500t full, and you can easily build 9500t CL in game that has all the major features of Omaha-class... except you can't build CLs bigger than 8000t before 1928.
But even on 8000 you can get nice representation of Omaha IMHO:
If you look at the HP to weight ratio it is closer to the standard long ton requirements of ships, so I guess that is what the game is balanced around. The Omaha would with it's 90.000 HP and at 7500 ton be able to make 33 knots on the game where is was about 35 knots in real life which require about 110 HP in the game. From my investigations the game also seem to require in general too much HP for any given tonnage (even when using standard long tons) and it usually gets worse the smaller the ship except for destroyers that seem to use a separate table for HP to tonnage ratio. In my opinion different hull frames such as BB, BC, CA, CL or pretty much every hull type should have its own HP per tonnage table. A light cruiser tend to require less than a standard cruiser for the same tonnage in HP to propel the ship the same speed. A standard cruiser of the same tonnage as a battleship would also require less HP per tonnage, the same goes for battle cruisers. In fact the IOWA class battleship was more built like a battle cruiser in terms of hull form than contemporary battle ships and also had worse sea going capabilities than some other battleships as a result but it was faster and more manoeuvrable which was a good trade off and was stable enough for being a good gunnery platform for its 16" guns. Machinery in general also seem to weigh too much, there are very few real ships that you seem able to create with roughly the technology level given for that year as far as I have tried to make them from 1900 to about 1935. |
|
|
|
Post by archelaos on Jun 11, 2019 7:06:06 GMT -6
If you look at the HP to weight ratio it is closer to the standard long ton requirements of ships, so I guess that is what the game is balanced around. The Omaha would with it's 90.000 HP and at 7500 ton be able to make 33 knots on the game where is was about 35 knots in real life which require about 110 HP in the game. From my investigations the game also seem to require in general too much HP for any given tonnage (even when using standard long tons) and it usually gets worse the smaller the ship except for destroyers that seem to use a separate table for HP to tonnage ratio. In my opinion different hull frames such as BB, BC, CA, CL or pretty much every hull type should have its own HP per tonnage table. A light cruiser tend to require less than a standard cruiser for the same tonnage in HP to propel the ship the same speed. A standard cruiser of the same tonnage as a battleship would also require less HP per tonnage, the same goes for battle cruisers. In fact the IOWA class battleship was more built like a battle cruiser in terms of hull form than contemporary battle ships and also had worse sea going capabilities than some other battleships as a result but it was faster and more manoeuvrable which was a good trade off and was stable enough for being a good gunnery platform for its 16" guns. Machinery in general also seem to weigh too much, there are very few real ships that you seem able to create with roughly the technology level given for that year as far as I have tried to make them from 1900 to about 1935. Machinery weights were adjusted during RTW1 development as players tended to build too fast ships, especially early on. Maybe the curves were not adjusted properly for later game tech as cut off date was 1925, and forgotten? The problem is that early game engines were simply huge - heavy, yes, but also inefficiently built and thus having large dimensions. As result, fast ships had to devote majority of space to machinery. Size of engines pushed bow and stern guns to the extremes of hull, making it impossible to fit twin turrets (as those places can't be wide in a ship that is supposed to go fast). This effect is not in game (there are no ship dimensions) so it has to be artificially forced through increased machinery weights. Another problem is that in game max speed is not max speed from trials. It is max sustained speed under combat load, and that is always less than trials max speed. Sometimes (for example in case of Italian cruisers from 20s-30s) those speeds are comically different (Italians did trials of ships with almost no equipment). So, when I try to make historical design as a rule of thumb I deduct 1-2 kts from declared max speed to get in game speed, unless I find sustained speed data. |
|
|
|
Post by jorgencab on Jun 11, 2019 7:33:32 GMT -6
If you look at the HP to weight ratio it is closer to the standard long ton requirements of ships, so I guess that is what the game is balanced around. The Omaha would with it's 90.000 HP and at 7500 ton be able to make 33 knots on the game where is was about 35 knots in real life which require about 110 HP in the game. From my investigations the game also seem to require in general too much HP for any given tonnage (even when using standard long tons) and it usually gets worse the smaller the ship except for destroyers that seem to use a separate table for HP to tonnage ratio. In my opinion different hull frames such as BB, BC, CA, CL or pretty much every hull type should have its own HP per tonnage table. A light cruiser tend to require less than a standard cruiser for the same tonnage in HP to propel the ship the same speed. A standard cruiser of the same tonnage as a battleship would also require less HP per tonnage, the same goes for battle cruisers. In fact the IOWA class battleship was more built like a battle cruiser in terms of hull form than contemporary battle ships and also had worse sea going capabilities than some other battleships as a result but it was faster and more manoeuvrable which was a good trade off and was stable enough for being a good gunnery platform for its 16" guns. Machinery in general also seem to weigh too much, there are very few real ships that you seem able to create with roughly the technology level given for that year as far as I have tried to make them from 1900 to about 1935. Machinery weights were adjusted during RTW1 development as players tended to build too fast ships, especially early on. Maybe the curves were not adjusted properly for later game tech as cut off date was 1925, and forgotten? The problem is that early game engines were simply huge - heavy, yes, but also inefficiently built and thus having large dimensions. As result, fast ships had to devote majority of space to machinery. Size of engines pushed bow and stern guns to the extremes of hull, making it impossible to fit twin turrets (as those places can't be wide in a ship that is supposed to go fast). This effect is not in game (there are no ship dimensions) so it has to be artificially forced through increased machinery weights. Another problem is that in game max speed is not max speed from trials. It is max sustained speed under combat load, and that is always less than trials max speed. Sometimes (for example in case of Italian cruisers from 20s-30s) those speeds are comically different (Italians did trials of ships with almost no equipment). So, when I try to make historical design as a rule of thumb I deduct 1-2 kts from declared max speed to get in game speed, unless I find sustained speed data. Yes.. I understand that you might be inclined to build very fast ships... the problem is that if you had different hull forms to choose from each would come with some downsides such as worse gun platform and/or limited in top weight and gun size, worse heavy weather performance etc... You should be able to build sprinter ships with the same kind of problems they faced with them in real life. The Omaha for example was very fast but the Navy was not really satisfied with its performance. It was poor for long voyages and not that sea worthy and the low freeboard was a problem for example, not to mention it was top heavy. But you should be able to build flotilla leaders and proper small scout cruisers. The way you solved this in real life was making the ship in general more speed performance so you could use a smaller engine. Armour would also be heavier since the ship wold be longer rather than wider for example. So... it would come at a price. Would have been nice to play with those options in the game though. |
|
|
|
Post by Antediluvian Monster on Jun 11, 2019 7:43:12 GMT -6
The game doesn't have Transom sterns either and those typically helped ships gain a knot or two. Transom sterns were rare in this period. I have gotten the impression that while they were known in latter part of the period (e.g. Fiji and La Galissonniere had one) they were often unused even where a more modern designer would add one. |
|
|
|
Post by jorgencab on Jun 11, 2019 8:05:23 GMT -6
I would just like to see a small difference between the choice made in hull shaped between at least destroyers, cruisers/battle cruisers and battleship. In game only the destroyer give you a different HP to weight ratio where I would like to see a small HP to weight ratio in the other hulls as well going from light, heavy, battle Cruiser to Battle Ship. Where if a Battleship displaced 10.000t and you had a light cruiser at 10.000t the battleship would need more machinery to reach the same speed given very light or no armour. On the other hand the battleship would need less weight for armour and would be more stable platform for larger guns at the same weight than a light cruiser.
This was one of the problems they face with putting armour on cruisers in the first place, it was simply not worth it since it weighed too much and reduce their speed too much, it was better to use the dreadnought platform that could fit more armour for less speed reduction to a reasonable degree of speed. If you had a 15.000t cruiser with the same thickness of armour and overall protection as a battleship then the battleship would be faster than the cruiser because the cruiser would need more weight for armour for the same level of protection due to the hull shape.
You faced the same problems with battle cruisers... since you wanted a really big ships with both protection and offensive firepower you had to try to get something that was neither a cruiser or a battleship. So given the same weight and proportion it could not have neither the same armour nor the same heavy weapon turrets as that of a battleship or the speed and grace of a cruiser.
|
|
|
|
Post by ramjb on Jun 11, 2019 8:55:28 GMT -6
Transom sterns aren't a "wonder ticket" into highspeedland. They had advantages, but also disadvantages, and for the most part the disadvantages outweighed the advantages in the timeframe the game is set up. Certainly there were very few ships (in the grand scale of things) with transom sterns than with conventional "Canoe/cruiser" sterns.
It all boils down to the fact that in engineering everything is a compromise, and whatever advantages you get from something in one way,you'll pay in disadvantages on another way. So it's a balancing act between your needs, your resources, what your navy can handle (or not), so you decide on which drawbacks you can accept in order to get some benefits elsewhere...or the opposite, which benefits you want no matter what, as long as you can cope with the drawbacks.
I'll quote here an explanation I read years ago in another forum, written by Bob Henneman. Might make things clearer to understand on the use of transom sterns:
"Transom sterns had benefits that became apparent during water tank tests in the 1920s and 30s. The transom design cut drag a bit at high speed because you got much smoother separation of the water flow from the hull (the British found it was worth 1/3 of a knot of extra speed at full power on Vanguard, for example), and through a bunch of math I don't understand it basically mimicked the hydrodynamics of a very long, every gradually tapered hull form- this saved you weight if you were looking to make the hull shorter by using the transom instead of a longer stern form. And if the transom was designed to carry below and above the waterline, then the stern of the ship was always constantly underwater and propeller efficiency increased because water flow was more consistent as the ship 'squatted' as acceleration was applied, or pitched the stern up and down in a seaway. The also eliminated the tapered part of the stern, which was impossile to protect with a torpedo defense system.
The transom stern is not perfect though- the benefits did not really show up until high speed, and at lower speeds it actually increased drag because it creating an area of 'dead water' that was pulled behind the ship. All else being equal, it used more building materials, so if you were not using it as a substitution for hull length it cost you tonnage. And the effects of a transom on ship vibration, performance, propeller efficiency, rudder performance, etc, and the effect of hull appendages like rudders, shafts, shaft supports, etc, were unknown, as no one had built a ship larger than a cruiser with a transom in that time frame. In fact, these still present a challenge, even in today's computerized world, so when designers had to rely on tow tank results (which often do not scale up to a full sized vessel for reasons no one can really fully explain) designers were often unwilling to take a chance on something radical or unknown to them. You only had so many slots for them under the treaties and only so much construction budget, so in the super-dreadnought era you really couldn't afford to screw up and build something that ended up not working.
So US designers, with no length restrictions; a concern for operational range across the Pacific that made cruising efficiency more important than efficiency at max power; and only trying to get 27-28 knots out of North Carolina, South Dakota, and Montana anyways; stuck to what they knew and liked: skegs on a cruiser stern. The skegs gave support and let the stern be very wide (ever notice how pear shaped South Dakota was compared to KGv, which looked like a canoe from the top?) but hollowed out underwater, giving the strength and space benefits of a wider design but the hydrodynamics of a long, narrow design. Plus the skegs had a nice side benefit of protecting the other shafts from an explosion that damaged one of them, and of holding a damaged or bent shaft in place so it would not hog out a huge hole in the hull. So why change what isn't broken, especially when you think you are onto something that is probably better?
The British, who DID have a length restriction (Vanguard was almost the same displacement as Iowa, but was 75 feet shorter to fit in the existing drydocks); and had previous experience with transoms on minelayers (bad experience) and cruisers (good experience); were less concerned with range due to their extensive overseas base network and areas of operation; were attracted to the transom, so they tried it on the never-built Lion Class, and the Vanguard.
Even today transoms are not universal, and different stern types are used in different applications based on the design priorities, be they speed, space, maneuverability, or whatever.
.
.
.
The transom stern is an excellent choice for modern destroyers and cruisers. The transom and it's false length is best suited for high horsepower to tonnage designs; it allows for a very shallow, flat-bottomed stern form that is excellent for high speed and maneuverability; it allows for the fitting of two screws and rudders on a narrow ship without overly long shafts; and it leaves a nice wide deck for first depth charges and later helicopter pads. The low-speed drawbacks are not nearly as relevant these days, mostly because in the 1930s fleet cruising speeds were in the 12-14 knot range where today 20+ knots is the norm for task forces or independent operation- nuke carriers do not have to worry about fuel efficiency, after all, and gas turbines are pigs at low speed anyways."
|
|
|
|
Post by Antediluvian Monster on Jun 11, 2019 9:27:29 GMT -6
It's worth noting that the period destroyers were already being built to such cruising-be-damned-high-speed-is-everything hull forms. Transom would be perfectly consistent with this (and Brown says as much), but still not generally used.
|
|
|
|
Post by jorgencab on Jun 11, 2019 15:17:53 GMT -6
I basically did some minor modding to the HP to weight ratio so that smaller ships gain some extra bonus that taper of at larger ships, this make smaller cruisers somewhat faster.
So basically roughly...
3000-4000t +2.5 knots
5000-6000t +2 knots
7000-12000t +1.5 knots
13000-14000t +1 knot
15000-16000t +0.5 knots
Not sure but I don't think balance will be upset too much by that...
|
|
|
|
Post by rimbecano on Jun 11, 2019 18:11:32 GMT -6
"Transom sterns had benefits that became apparent during water tank tests in the 1920s and 30s. The transom design cut drag a bit at high speed because you got much smoother separation of the water flow from the hull (the British found it was worth 1/3 of a knot of extra speed at full power on Vanguard, for example), and through a bunch of math I don't understand it basically mimicked the hydrodynamics of a very long, every gradually tapered hull form-...
...
The transom stern is not perfect though- the benefits did not really show up until high speed, and at lower speeds it actually increased drag because it creating an area of 'dead water' that was pulled behind the ship.My understanding is that the upshot of the math that the guy you're quoting doesn't understand about how transom sterns mimic a long, tapered hull form is basically that the "dead water" behind the ship takes approximately the form of a cruiser stern and interacts with the bow wave in approximately the same way. So when you're traveling fast enough that wave drag is significant, you benefit from the increased effective hull length, otherwise the water you're pulling around behind you is dead weight. |
|
|
|
Post by brygun on Jun 12, 2019 19:10:17 GMT -6
We could add a structure strength selector affecting the amount of hit points for the tactical structure. In exchange you could get less hull weight which ought to add to the speed.
If that sentence made sense to you congratulations.
|
|
|
|
Post by jorgencab on Jun 13, 2019 10:24:03 GMT -6
It's not all about weight here, I think that is my point.
It is rather simple. A ships with wider beam in comparison with its length will be slower than a ship with smaller beam in comparison with its length. The drawback with a smaller beam is overall sea-keeping and stability to fire heavy guns or any guns at all in extreme cases. So, there could be a choice for cruisers to use a faster hull frame or a more traditional hull frame. If you use the faster frame you are more limited to top space and what sort of weapon you can fit and will experience lower rate of fire or accuracy penalties. The ship can also be more effected by harsh weather conditions.
This way there is a trade off between offensive firepower and speed that have little to do with weight and you might be worse of in harsh weather.
|
|
