Overtonnage and Undertonnage - Discussion

[AnotherDilbert]

First -- Marc did the designs himself. I saw the deckplan in 2017, and saw the design draft in 2019. Naturally I didn't see the overtonnage issue.

OK, thanks. That undermines my position...

And the rules specifically deals with that, where added subhull stuff can cause an increase in the ship's base hull (regardless of detachability).

No? Overtonnage leads to increased hull size. I don't think added subhulls do.

A "random" ship uses a main hull of 400 Dt + 20 Dt pod = 420 Dt (design tonnage). Drive performance is calculated for 420 Dt.
Hypothetically it stuffs enough components (422 Dt) into the main hull to get an overtonnage of 22 Dt. Resulting tonnage is 442 Dt (with the pod), overtonnage is 22 Dt, regardless of the pod is carried or not.

LOL! I see overtonnage as 42 tons, because the drives are pushing 42 tons over their rating. That seems to be what Overtonnage is for: performance calculations.

We just agreed that overtonnage is the difference between design tonnage and resulting tonnage?

The drives are explicitly dimensioned for the design tonnage = 420 Dt, and might even be large enough for 500 Dt (without stage effects). Does not affect overtonnage?

Overtonnage is a penalty for an underdimensioned hull, not drives.

Hence overtonnage can be fixed by adding a subhull or pod, to increase the design tonnage?

 

[AnotherDilbert]

LOL! I see overtonnage as 42 tons, because the drives are pushing 42 tons over their rating. That seems to be what Overtonnage is for: performance calculations.

I see it as a way of avoiding performance calculations. It introduces a bit of leeway without having to bother with pods or oversized drives.

So I'll introduce the term "total tonnage" which is used in key places in T5, and seems to mean "everything attached to the ship".

Agreed, as it always has:

LBB5'80, p27:
L-Hyd tanks are installed outside the hull, and increase the total tonnage of the ship; drives are reduced in their efficiency based on the total tonnage of the ship. With tanks retained, efficiency is decreased, and jump capability is reduced; when the tanks drop away, tonnage is reduced, and the drive efficiency is increased.

Note: Total tonnage ≠ hull.

 

[AnotherDilbert]

No? Overtonnage leads to increased hull size. I don't think added subhulls do.

Sorry, I see we are talking about different things. You are talking of the QSP, I was thinking about excessive overtonnage forcing a bigger hull.


Agreed, the QSP should be based on total tonnage of the ship, including subhulls and pods. But it isn't...

 

[robject]

Be careful what I agree to; I might be lying.

Total tonnage ≠ hull.

Agreed. Total tonnage = hull + attached items.

excessive overtonnage forcing a bigger hull.

Agreed here too.

Gross overtonnage (more than 49 tons) is rounded to the next larger hull. T5 B2 p70.

Here, overtonnage is specifically referring to the hull, not the hull plus other things.

And I think this is an important point, because adding a barge doesn't force the ship's hull to be bigger. It affects total tonnage.

---

To go further:

1. Gazelle. If a ship has detachable bits, then it will have changing performance characteristics.
2. Daring. Marc's example suggests that Pod hulls affect Overtonnage -- perhaps of the Total Design.
3. The implication is that Agility and Stability are about Total Tonnage.

I don't think I can prove this. Add to that the ease at which I get lost in details at this level.

 

[robject]

Found the problem, I think.

Overtonnage applies to the hull on page 70:

Ultimate Hull Tonnage May Vary. Undertonnage improves performance. Overtonnage reduces performance. Gross overtonnage (more than 49 tons) is rounded to the next larger hull.

^ My emphasis above. That last sentence only applies to the hull.

At the same time, the Daring creates an undertonnage based on the total tonnage:

In combat, the ship ideally sheds its two Fighters and Ship’s Boat to create an undertonnage (348 tons) and Agility +2 (total in Atmosphere +3).

Perhaps the Daring's position is identical to the Gazelle's after all (p37):

Standard with Drop Tanks (400 tons): Jump Drive H in 400-ton hull produces Jump-4. Maneuver Drive H = 4G.

Without Drop Tanks (300 tons): ... Jump-2 (based on 60 tons of fuel). Maneuver Drive-H = 5G.

Special (300 tons after dropping tanks): ...Jump-5, with the Drop Tanks shed before Jump initiates.

In the Gazelle's case, the drastic change in tonnage results in a radical change in drive performance.

But in the Daring's case, the change is less drastic. It's enough to grant an Agility benefit, rather than going the whole way and changing drive performance.

 

[robject]

TOTAL OVERTONNAGE - IMPLICATIONS

If that's right, then the Subsidized Merchant, with its dorsal Launch, could gain an Agility bonus when its Launch detaches. Similarly other ACS with attached boats. Agility could potentially improve, depending on how total overtonnage changes.

+35 tons to +15 tons	+20 tons to +0 tons	+10 tons to -10 tons
-2 Agility to -1 Agility​	-1 Agility to +0 Agility​	-1 Agility to +1 Agility​

 

[Spinward Flow]

This is why I use the terms "clean configuration" to mean there are no external attachments added on ... along with "external load" to very explicitly delineate that there are items externally docked and being towed (jump and/or maneuver) by the ship.

My baseline for thinking in these terms is derived from real world aviation.

In real world aviation, a "clean configuration" means there are no external weapons or pylons or slung load or anything attached to the craft in question. There's "nothing extra" hanging off the wings, there are no external weapons or drop tanks or pods or anything. The only "stuff" the craft is carrying is all internal.

Contrast this with external loads of weapons, stores, slung load cargoes, etc. hanging off the craft at various points. Pods and missiles on external pylons create drag, reducing overall performance. Slung load cargoes reduce top speed/maximum altitude (and so on) due to the external load.

And then you have some aviation assets that are capable of lifting a larger load than the weight of the craft itself. Rotary wing sky cranes, fixed wing cargo planes, blue water container ships.

What you need is a system that usefully describes how drive performance fluctuates when the mass/displacement of what those drives are trying to push around changes. If you add drop tanks/cargo pods/etc. to a craft, how does that external loading reduce/degrade performance?

As @robject points out above ... when you have more drive than you need, you've got undertonnage and performance improves.
When you have less drive than you need, you've got overtonnage and performance declines.
However, in order to make that determination, you need to calculate the total amount of tonnage the drives are attempting to push around ... and that's total tonnage.

 

[robject]

^ It makes sense, but AnotherDilbert and I want to play by the rules, so we want to resolve this by the rules too. It disturbs me that it's not clearer in the rules.

---

Thinking aloud about the Daring, I see that the small craft are added just like any other components, regardless of whether they're internal to the hull or attached.

The Gazelle's interim design (p37) treats drop tanks as components, as well as the ship's boat. Similarly the Fiery on the same page. Note that these are added as components to the ship design, even though they do not fit inside the hull. The Gazelle does things in a slightly strange way, by designing drives for a 400 ton hull, but then starting with a 300 ton hull. On a spreadsheet the difference is the difference between the cost of a 300t hull versus a 400t hull... but that's about it.

And the Gazelle is seriously overtonned for a 300 ton vessel, but fortunately the drives were calculated to work with a 400 ton design, so it's a 400 ton design with a 300 ton hull. Eeek.

The Lab Ship (p40) treats the Fast Pinnace as a component.

The Kinunir's two orbital assault launchers are inline components as well, and the design is overtonned.

 

[robject]

The Gazelle violates the QSP, no matter how you interpret it.

Sharik: "Is it a 300 ton hull?"
Eneri: "Yeah."
Sharik: "But is it Jump-4 Maneuver-4 at 300 tons?"
Eneri: "No."
Sharik: "So it's a 400 ton hull?"
Eneri: "Well...."
Sharik: "Okay then, does total tonnage mean the 300 ton hull?"
Eneri: "Well, no."
Sharik: "So total tonnage means all 400 tons of it?"
Eneri: "Uh no. I mean, sometimes."

<BANG>

 

[Rigel Stardin]

Now you know what I went through when I went through when looking at the Gazelle. The Math and game mechanics just don't jive. That's why in MTU I went with Fuel, Vehicles, Cargo and Externally Mounted Equipment as extra weight. My rule of thumb is if you have to remove a hull plate or it can't fit down a hallway without being disassembled, it's apart of the ship. The Hull size is just the empty weight of the ship minus the fore mention components.

One of the last ships I built under my system, came to 382 Tons so I rounded up it to 400 Ton Hull Size. Those extra 18 Tons are for the items mostly overlooked by Game Designers when they build there construction systems. (One Example: Water and Atmospheric Gases for the Life Support System.) So for me, the Hull Size is really nothing more than the structure and internal components of the ship.

One thing I have seem discussed in this thread is Armor and it's effect on the ship's overall weight. Do you consider it a component or an add on?

 

[Spinward Flow]

The Gazelle does things in a slightly strange way, by designing drives for a 400 ton hull, but then starting with a 300 ton hull. On a spreadsheet the difference is the difference between the cost of a 300t hull versus a 400t hull... but that's about it.

And the Gazelle is seriously overtonned for a 300 ton vessel, but fortunately the drives were calculated to work with a 400 ton design, so it's a 400 ton design with a 300 ton hull. Eeek.

The Gazelle is a whackadoodle design.
I get the feeling that it was trying to be a "pocket Kinunir" (lasers and particle accelerators) at a time when the starship design rules were rapidly evolving and changing out from under the Gazelle, so the Gazelle tried to demonstrate the (at the time, new) L-Hyd drop tank fuel system option and basically faceplanted along the way into just being a mess. The EP budget is so horrendous under CT that the class has Agility=0 ... which is "no way to run an escort" (except for target practice).

My personal opinion that a fighter tender with even a modest load of fighters would be a superior option for budget, combat effectiveness and patrol/escort duties than the Gazelle as originally detailed. Let the fighters do the interplanetary leg work, (small) ship to ship combat as well as recon and space denial with the starship operating as a carrier base and jump transport and you have both a more flexible and effective combination for both the tonnage and the price.

 

[kilemall]

Disturbed by unclear rules?

You do know which franchise you are working, right?

 

[Grav_Moped]

The EP budget is so horrendous under CT that the class has Agility=0 ... which is "no way to run an escort" (except for target practice).

If it was designed under HG '77, agility was less of an issue. This is also a problem with the Kinunir and Lightning classes.

 

[Spinward Flow]

If it was designed under HG '77, agility was less of an issue. This is also a problem with the Kinunir and Lightning classes.

I get the feeling that it was trying to be a "pocket Kinunir" (lasers and particle accelerators) at a time when the starship design rules were rapidly evolving and changing out from under the Gazelle

Already ahead of you ...

 

[Grav_Moped]

Already ahead of you ...

But you missed the point of the Gazelle It's not a pocket Kinunir, it's the High Guard implementation of the Type T Patrol Cruiser concept. With matched acceleration and 1 Jn higher with the tanks retained, just to show off how much better HG ships are.

 

[AnotherDilbert]

Sharik: "Is it a 300 ton hull?"
Eneri: "Yeah."
Sharik: "But is it Jump-4 Maneuver-4 at 300 tons?"
Eneri: "No."
Sharik: "So it's a 400 ton hull?"
Eneri: "Well...."
Sharik: "Okay then, does total tonnage mean the 300 ton hull?"
Eneri: "Well, no."
Sharik: "So total tonnage means all 400 tons of it?"
Eneri: "Uh no. I mean, sometimes."

<BANG>

There is no contradiction, it's:


Not:





In this scenario the Gazelle is a 300 Dt pickup with a 100 Dt trailer (total tonnage 400 Dt), it is not a 400 Dt truck where the trailer is loaded into the cargo bay.

The pickup with trailer is slower and uses more fuel. The pickup without trailer is a smaller total package, faster and uses less fuel, right?

Whether towing the trailer or not, the pickup is still just a pickup, the chassis is the same. It does not turn into a truck when you attach the trailer...


Sorry, I'm not trying to be facetious, but this is the problem some people seems to have with the Gazelle.

Yes, while carrying tanks it's a 400 Dt ship (total tonnage) with a 300 Dt hull. Drop the tanks and it's a faster 300 Dt ship (total tonnage) still with the same 300 Dt hull.


Note that the USP, and presumably the QSP, is a momentary snapshot of the total vehicle as it is right now:

Without the tanks it's a size 3, J-5 ship, with the tanks it's a size 4, J-4 ship.

I imagine the QSP behaves the same way, without the tanks it's CE-CU55, with the tanks it's CE-DU44. It always has a type C (300 Dt) hull. The QSP describes total tonnage (not just main hull), as it is just now.

 

[Rigel Stardin]

As I explained in the Gazelle Study, the stats are off. I believe the Gazelle with Tanks should have Manuver of 3 with tanks and 5 without. Jump should be something like 4 with with tanks and 5 without. I think the real problem some people have with the design is the designer gave the ship 4 hardpoints when it should have had only 3.

I use fixed weapons (weapons mounted inside the hull and take away from interior space) but try to stay to the hardpoint rule because, technically I could up gun every combat vessel by adding fixed weapons every where I could find usable space. For the Gull's weight it's under gunned, so is the Cygnus by Traveller rules. By moving bunks or double occupancy every stateroom, I could have added upto 34 more weapon systems to the ship? But I didn't because for long range survey missions, you need space for the crew. Living in a tin can for up to six months with three people in one space or 'hot bunking' does go very well with the crew...

 

[AnotherDilbert]

Agreed. Total tonnage = hull + attached items.


Here, overtonnage is specifically referring to the hull, not the hull plus other things.

And I think this is an important point, because adding a barge doesn't force the ship's hull to be bigger. It affects total tonnage.

But you are arguing that pods are overtonnage, here you are saying that (larger) barges are not overtonnage? They go by the same rule, but are perhaps treated differently in the examples.


Making the (main) hull larger makes some kind of sense in either scenario. If you deduct external craft from hull space, you are in effect making the main hull smaller in order to keep total tonnage constant.

Take the Daring for example; As the example is written it has a 400 Dt hull plus 50 Dt small craft treated as overtonnage. To avoid the overtonnage penalty only 350 (or so) Dt components are stuffed into the hull, so that the total tonnage goes down to 400 Dt, right? In effect the main hull is only 350 Dt + 50 Dt craft = 400 Dt total tonnage.

You are changing the size of the main hull to compensate for the overtonnage caused by the external craft. At some point the main hull get so small it should be a smaller size. Or vice-versa if you allow too much overtonnage.

 

[AnotherDilbert]

As I explained in the Gazelle Study, the stats are off. I believe the Gazelle with Tanks should have Manuver of 3 with tanks and 5 without. Jump should be something like 4 with with tanks and 5 without.

The math works fine. It's based on LBB5 where drives were not linear.

In T5 it is based on the Drive Potential Table:

An H drive gives potential 4 in a size D (400 Dt) ship, and potential 5 in a size C (300 Dt) ship.

With the precise method we can calculate that 800 EP gives potential = 800 / 400 × 2 = 4, or in a 300 Dt ship potential = 800 / 300 × 2 = 5.333, rounded down to 5.



In LBB5'80 it had a 20 Dt jump drive and a 44 Dt M-drive:

CE-3455881-000000-00000-0        MCr 385         300 Dton    Ag=5
CE-4444681-000000-00000-0        MCr 385         400 Dton
               Cargo=43 Fuel=85 EP=25 Agility=4 DropT=100

Dual Occupancy                                       43       385
                                     USP    #      Dton      Cost
Hull, Part Streaml  Custom             3            300    
Configuration       Close Structur     4                       18
Scoops              Partial                                     0
                                                           
Drop Tanks          100 Dton                                    0
Total tonnage       400 Dton                                
                                                           
Jump Drive                             4    1        20        80
Manoeuvre D                            4    1        44        22

which is more than enough for:

CE-3455881-000000-00000-0        MCr 369         300 Dton
                         Cargo=0 Fuel=174 EP=24 Agility=5

Dual Occupancy                                    -  40       369
                                     USP    #      Dton      Cost
Hull, Part Streaml  Custom             3            300    
Configuration       Close Structur     4                       18
Scoops              Partial                                     0
                                                           
Jump Drive                             5    1        18        72
Manoeuvre D                            5    1        42        21

I even made a table of drive capability in one of my spreadsheets, just for an earlier iteration of this very discussion:

This shows J-5 up to 333 Dt and M-5 up to 314 Dt. The main hull's 300 Dt is no problem.
We could even do J-1 while carrying 700 Dt drop tanks.

 

[AnotherDilbert]

I think the real problem some people have with the design is the designer gave the ship 4 hardpoints when it should have had only 3.

The original (JTAS#4) was a LBB5'79 design. It was a 240 Dt hull + tanks with two turrets and (presumably) a small 10 Dt bay, which is apparently legal, in LBB5'79. The bay was reskinned to two barbettes for LBB2 combat.

The LBB5'81 remake emulated the armament as four turrets on a 300 Dt hull, which is indeed not correct. They were just trying to keep as close to the original as possible. In effect it is house-ruled, by the "House".