Reffiting Destroyers...

[Desertfox]

The temperamental nature of destroyer designs in SpringSharp has got me thinking about how to deal with refitting them and I notice three major issues compared to OTL destroyers.

1) Doing a basic refit say replacing a gun with misc weight or vice versa without touching the machinery can still cause a design to drop under 50% machinery weight. These kinds of refits where extremely common in OTL, see US destroyers swapping main guns and torpedo tubes for ASW and AA guns.

2) Dropping half the machinery to turn destroyers into fast transports is impossible under the current rules. This was a common way to make use of older destroyers, see US four-stackers and Japanese conversions.

3) Trying to refurbish a destroyer with updated machinery is almost impossible under the current rules. You basically have to stuff the same weight in machinery which can lead to insane speeds, and basically negates the reason for doing the update in the first place.

Based on that I would like to recommend the following rule changes specifically for destroyer modifications:

1) A destroyer being refitted where all the changes are superficial (guns, misc weight, etc) in nature, does not have to worry about machinery weight being 50% at the end of the refit. This would not apply if the machinery and/or fuel tonnage are part of the refit.

2) A destroyer can be refurbished, where half of its machinery is removed, and still be considered to be under destroyer rules. In order to use this exception, the refurbishment must meet the following conditions: Half the machinery must be removed (no more no less), the machinery cannot be updated at the same time.

3)  A destroyer can be updated with new machinery that weighs less than the original set. However, the destroyer must have at least the same minimum speed. Speed cannot be downgraded in this type of refit; however, the destroyer can end up with machienry weight being less than 50%.

[Jefgte]

IMO, if DD -Fleet destroyers or Torpedo Boat- are rebuilt or converted, they went out the current rules (Machinery 50% & cross-sectional 50).
Conversion should only look like multiple OTL conversions.

[Kaiser Kirk]

Hmm,

Overall, I'm not really interested in a new rule discussion.
I'm trying to get the Iberian and Norse fleets rounded out, so I have a baseline to calculate the Mayan so that can move forward.
Then I want to get back to Parthia, to move that forward before I need to resolve battles of a war.

Testing :
If I take my 1906 750t Atlatl class and replace the engines with engines of the same speed, but all oil burning,
Then I free up enough weight I can change the main guns from 4x 90mm to  to 8x 120mm, and
have 65 tons additional Misc wt.
If I up the speed from 27 to 28 knots, then I can only have 45t more Misc wt. Still a lot on that hull.

The end result is a much more dangerous ship than I could build new. So that's no good.

Generally speaking, destroyers were viewed at having shorter service (not reserve) lives.
I can't think of examples of them being re-engined, just the Americans removing engines.
to make void space.

The current rules also make the cost of re-engining rather uneconomical for ships with high engine %s.

Currently, removing engines from my Atlatl to get down to 'cruiser rule of 0.9' means down to 21.5knots.
Removing half of them, gets me to 19.8 and 1.15 comp hull, allowing me to add 105 tons of Misc wt.

Shortly with the 1920 cruiser tech, that will be 0.75.
That would mean after halving the engines, I could add 165tons misc wt.

Or, I could keep more of the engines for higher speed and add less wt.

So I think the DE conversion can be managed under the current cruiser rules.

[Desertfox]

We don't have to change anything right now, but did want to throw it out there before I forget.

#3 isnt as important as the other two. But can be a real issue if you want to switch from mixed firing, to oil-firing, which can't be done under the current rules without also changing the engines.

The US four-stacker conversions managed to add 4 small 10t boats, 200 troops, and 40t of cargo. According to our rules thats 520t of misc weight, 320t if we assign 1t per soldier. Cant do that with cruiser rules. At that point you are better off building new using aux rules.

[snip]

Thoughts

1) I'm not strictly against it.
2) No, this is a shortcut to more capable ships then could be built new
3) No, this is a shortcut to more capable ships then could be built new

[Desertfox]

Played around with the Sakura II class to see what dropping half the machinery does (#2). Speed dropped by 5 knots (30+ to 25+), misc weight went up to 150t, 200t if you drop the torpedoes. Not bad but you still have to pay for the DD + the refit. Compared to the Matsu Maru, dedicated fast transports built using aux rules, the Matsus have 420t+ of misc weight and can do 21 knots. The speed on the Sakura conversions is nice, but they cost more than twice (780t vs 330t) as much for only about a third of the capacity.

I can see the arguments against 3) but I have to disagree with 2) being a shortcut, if it is its a very expensive one at that, that can be done a lot cheaper in other ways. Mainly I just want to find end of life alternative usages for destroyers.

[Kaiser Kirk]

I would like to point out that SS indicating a 1000 ton DD with .5 hull having 600 +/- tons of engine
does not mean if you take out 300 tons of engine, there should be 300 tons of things you can stuff in.

Rather, it means we know SS grossly overestimates the weight of engines for destroyers, and we compensate for that by letting the hull drop to 0.5
So any 1:1 conversion of weight is ill-conceived.

'Real Life' destroyers were built with light scantlings, and thinner hull plates, less redundancy, (and generally shorter active service life) lower comfort, and lightweight high performance machinery.
SS doesn't model that well, we have a gross 'Fudge' of the 0.5 hull, and then we have the 'trial speed' on top of it.

Another 'real world' thing is they would frequently add more weight, accepting lower draft and freeboard, to existing ships. Part of the reason the American 'Standards' were heavily bulged
was torpedo standoff distance...but another was to add floatation and bring them back up higher in the water.

That is 'echoed' in the current rules-  you can "add' displacement in refurbishments by lowering draft & freeboard.
"The waterline may be raised or lowered by 10%.  The trim may be changed. "
For that Alatl class , that lowers the draft by 0.24, increasing the light displacement from 750 to 829.
Rip out half the engines and comply with cruiser rules, and you get your DE.

[Kaiser Kirk]

I tried to explore how destroyer weights work.

They are weird.

The "normal %" we use so we have a 1-stop shop for verifying if the design is allowed, in conjunction with the hull value it is simple and replicatable, and so our "Fudge" for destroyers being built so flimsily and with lightweight machinery.

What effects "Normal" displacement, which is what % of weights is based on?
Base of 467tons, 52.9% machinery

First – What does changes in one category do to that Machinery % ?

Armanent : decrease in Armanent weight increases machinery %, and decreases 'fuel ammunition and stores'.
...and seems to slightly add machinery weight... huh?

Armor : decrease in Armor increases machinery %

Miscellaneous weight :
Void weight : decrease in void weight increases machinery %.
decreases in other misc weights also increases machinery %...
but increases machinery weight slightly. Again, Huh?
Curiously, the fuel/ammo/stores stays exactly the same

The location of the miscellaneous weight does not seem to matter,
but the engine weight can vary by ~2%. 

FUEL seems to effect max draft, but misc weight does not.

Conclusion.... the shift in machinery weight is very odd, but otherwise it makes sense.
Decrease the weight the ship has specified, and the fixed weight of the engine takes up relatively more.
It Does not compensate for unallocated weight.

Moving Misc weight to Guns wound up decreasing machinery weight for some reason.
I ... do not get that.
Keeping Ammo (and displacement) the same, moving it from Guns to Misc ... raised the machinery weight.

Spoofing the System :
So a Destroyer Built with 'understressed',  but 50% machinery
Example – my Atlatl with no guns / misc weight, has engine wt go from 467->485 and machinery %->55%.  "Light Displacement" - due to lack of ammo – increases 11 tons to 761.

Removing 23tons of guns, 18.3 Tons ammo and 34 tons Misc wt: - 75.3tons
Decreasing it to 50% machinery reduces the ship to 23.375kts and 441t machinery, 0.82/.76 hull.
...no guns/ misc weight assigned.

I can add 175t of misc weight (or guns) and keep at .53/.5 hull, but machinery drops to 43.1%
making a supercharged Destroyer escort or gunboat.

Result : simply requiring 50%+ machinery at the start does not work, as it allows run arounds.

Conclusion :
SS is not reliable here.

Swapping guns/misc weight is not a 1:1 process.

Designating some 'special destroyer basic refit' rule as a work around,
probably means we loose the very simple "checks' on compliance – is machinery wt 50% + ...y/n?
Ok, and how about hull strength.. .5+ ok.

[Desertfox]

That right there! That has been driving me crazy, it makes no sense half the time. It turns what should be a fairly basic and straightforward process into a nightmare, and its a process that happened a lot in OTL. Destroyers where constantly getting the equivalent of a basic refit.

My issue with using cruiser rules to get APD conversions is that in ends up making no economic sense. Scrapping the destroyers and building new APDs to Aux rules is cheaper and ends up with much better ships. It'd be a shame to lose out on an entire class of historical ships due to a technicality.

[TacCovert4]

APDs, and the historical conversions done to destroyers to make them asw weapons. 

I might suggest the following for dds being refit out of traditional dd jobs:

1)  Engines cannot be updated.  If you update your engines the ship must remain within dd rules.

2)  the ship class must have at least 5 years in service.  This is to prevent players from building dd classes for the express purpose of conversion. The original ship obviously had to meet dd rules.

3)  you can remove engine weight by unit weight.   So you can't pull 10 tons of engine off.  If you have a dd with say 2 shafts and 520 tons engine weight,  you can remove 130t, or 260t, etc.   You're not replacing machinery,  you are removing boilers.   Your speed will be whatever SS says it is at that engine tonnage.

4)  you may remove main armament, refresh it, or swap them for smaller weapons.  You may not add main guns.

5)  of the miscellaneous weight that you gain by removing engines,  only half of it can be used above water.  At least half must be either left on the table, or used Below water.  Adding fuel bunkering is a Below water addition and acceptable. 

In essence what I'm going for are rules that allow someone to rapidly turn old destroyers with no other real purpose,  into minesweepers,  APDs, or ASW escorts.   So you could pull half the engines out of an old destroyer that might only have 1000 to 2000nm range,  bump it's range up to say 4000nm and add on asw kit.  Or make it an apd.

[Kaiser Kirk]

As I pointed out, the engine weights are not correct. 
The engines displace more than they should.
Therefore removing engines frees up more weight than it should.

You want a DE - degrade the engines and live under the cruiser rules.
Same with APD

If that's more expensive than a new aux...wartime conversions may not have been the most economical
approach either.  It could have something to do with modifying an older hull and engines being easier on the yards than building a hull and engines from scratch.

[Kaiser Kirk]

Regarding "New rule proposals"

Things that aren't working right - like the Destroyer basic refit issues, that should be discussable.

But just posting up new rules that a player wants added ?
NO.
The rules have not been opened for proposals.
Wait for when they ARE opened for proposals.

Which means after we get all the other stuff out of the way.

I do not want to have a new rule discussion at this time on a niche product.

Especially if the initial proposal doesn't seem to have been tested.
I've already twice spent time trying to figure out weights and then posting about them.

I don't want to have to spend time on that.
I have other things I want to do.

The DE/APD discussion is done.

If you want to keep spitballing ideas on the Basic refit part, go ahead.