Bulge problem - too much unused displacement

[davidlondon]

Perhaps someone can help me.

Starting in 1900, I have an old 5,000 ton, 22 knot legacy fleet CL. I want to rebuild her as a minelayer on the cheap, adding mines, replacing her 8 x 6 in guns with a better model, upgrade the fire control and add light AA. As she was part of the 1900 legacy fleet she has no TPS so I am adding bulges to improve her survivability. Total works come to the small cost of 2,988 spread over four months.

The guns, mines and fire control takes her over her tonnage, but never mind, as the bulges will more than make up for this, and I am planning to use her as minelayer I am happy to take a reduction in speed as I understand from the forum this will make her less likely to be selected for a battle.

However when I check the design I find that the extra 500 ton displacement bulges have added means the re-design is no longer legal as I now have too much unused tonnage.

I do not want to spend more resources just to add weight.

Has anybody had this experience? And what do more experienced hands suggest?

As an aside I have just noticed that adding the bulges only increases the costs by 5. Is this correct?

[rimbecano]

I'm a bit surprised that bulging takes you straight from overweight to too much unused tonnage, but there are certainly reasons that bulging an old hull without adding enough extra weight could be problematic. The extra volume will cause the ship to float higher in the water, which could do things like causing the bottom edge of the belt to be above the waterline, or exacerbating issues with topweight. Neither of those is directly addressed in game, but I believe the unused tonnage limitation is meant to indirectly account for such issues.

[davidlondon]

That is pretty much what I was thinking, she will now ride too high in the water. And since that involves a level of modelling RtW doesn't address it is disallowed.

My understanding is that retrofitted bulges (as opposed to the increasingly sophisticated built in to the initial design torpedo defence systems represented by torpedo defence 1, 2, 3 etc) were usually water filled. Which I assume means that they wouldn't add to bouyancy as the water they contained was broadly equivalent to the mass of water they displaced.

IRL of course if excess bouyancy was an issue presumably the vessel could be balasted to prevent this, which is not catered for.

Has any one got a work around for this?

[emcie]

Have you tried just upping the ammo load to make up the difference?

[jwsmith26]

I believe the prohibition about excess unused displacement was put into place to prevent intentionally leaving excess displacement with the intent of later converting the ship into an aircraft carrier that could then use the excess displacement to create a larger air group. It's an attempt to balance the foreknowledge of future events that players naturally have but was not available to ship designers at the time. Of course, the solution is not perfect and occasionally causes issues such as davidlondon has encountered. 

Bulges were not always added just to add torpedo protection. They were often added to address stability problems. For instance, bulges were added to a number of ships during WW2 to improve their stability that was impacted as they were increasingly overloaded with electronics and AAA. At the time, the slight loss in speed was far less important than the increase allowed in anti-air weaponry. Incidentally, bulges can serve the same purpose in RTW2, adding displacement so additional AAA (or other equipment) can be added.

Personally, I never add torpedo protection to my CLs. They are almost as hard to hit with a torpedo as a DD and I find the cost in offensive power or speed, to these small ships is too high a price to pay for a defensive system that is unlikely to be used. 

My advice would be to first skip the light AA to reduce weight. A ship on TP is unlikely to be targeted by enemy air, and if it is attacked, LAA is going to do nothing to stop the attack (though it may cause some damage to the aircraft after they've attacked). This is an old, slow ship with a new primary mission of minelaying. One of its main objectives should be to avoid combat. It's guns are there only as a last resort if forced into combat. It will probably lose any battle if it's engaged by a newer cruiser. For this reason, I would probably remove enough secondary or main guns to lower the weight to legal limits rather than invest more money to bulge the ship.

[jwsmith26]

Jul 4, 2021 8:17:22 GMT -6 emcie said:

Have you tried just upping the ammo load to make up the difference?

This could work if you have lots of time. The problem with this solution is that any change to a magazine capacity automatically requires a 10-month rebuild. 

[davidlondon]

Thank you both for your replies.
I understood the reason why the there is a limit on unused displacement to prevent building ships for later conversion. I fully support this.

Thinking about it the 500 ton additional displacement for adding anti-torpedo bulges is standard for all large ship classes. I am saying large ships as I just checked and I can't bulge a 700ton KE or a 1,100 ton DD, so I am assuming that only ships of LC and above can be bulged, though his could be a minimum hull size thing.

I take the point about the light AA, I can drop that which means I actually don't need to bulge for weigh reasons. Though I might want to add medium AA later. However, in this case bulging is attractive now as it (1) reduces the speed without re engining, and as far as I understand the lower speed means it is less likely to be sent out to battle, (2) allows me to add new kit, and yet further kit in the future, (3) it is the only way to add a modicum of torpedo protection, (4) it is only costing me 5, which is very little in game terms (probably less than an admiral's tea and biscuits allowance).

I shall follow your advice and drop the light AA and be gratefull for the game we have and await Ironclads to Missile Cruisers.

[hawkeye]

You could try how expensive adding some tertiary guns would be. You can later remove them again (that should be pretty cheap), so you get the tonnage back.

On a legacy CL of 6500 tons in my Austria-Hungary game, in 1909 bulging alone amounts to a cost of 715 and gives me 548 tons of free displacement.
Adding 16 x 3" tertiary guns brings the cost up to 1812 (604 for 3 months) and reduces the free tonnage to 395
Increasing instead the 8 x 4" secondary battery to 16 x 4" brings the cost up to 2425 (3 x 808) (almost the same free tonnage) but _does_ offer the ability to later be turned into a much more effective dual-purpose battery.
Doing both brings the free tonnage down to 244 and the cost up to 3522 (3 x 1174)

[oldpop2000]

I just upgraded a 4500 ton light cruiser built in 1904. I replaced the machinery and converted to oil. Upgraded to improved 6 inch guns and to Improved director. I added 46 mines, the limit. eliminated all torpedo tubes and bulged her. I gained five knots on my speed. I also added six 3 inch guns for good measure. I don't know if this will provide any ideas, but here is the result.