Fuel tank balancing

[Crai-Crai]

In the last big update, the small fuel tank was made bigger, apparently to "balance" the small and large tanks. So now the large tank can hold 3x the fuel of the small tank, but costs 5x the price and still has a much bigger footprint. It seems that the 344,000L tank is the only good choice now. Just, lots and lots of them in parallel. What am I missing?

[RoxiSinister]

IIRC, the large tanks are 7x7 footprint, and the small tanks are 4x2 footprint. 3 small tanks would have an 8x6 footprint, making them roughly equivalent to the large tank. I also think the small tanks are less than 1/3 of the price....$27k vs. 104k? Something close to that, anyway.

[Crai-Crai]

Thanks for taking the time to reply. I checked the numbers. The large tank has a 7x7 footprint as you say, at 49 tiles. Six small tanks would have a footprint of 48 tiles, at 8 tiles each times 6. Six small tanks would cost $134k and have a capacity of 2,064,000L. Same footprint, 30% more cost, and 106% more capacity. So I don't know how the devs thought this was balance.

[LVGameDev]

@Crai-Crai -- You make great points and have the numbers to back them up, love it.

Honestly the balance adjustment here was one that we didn't actually run numbers very closely on; what we were really looking to do was just to make the small tank actually be useful. At the time (and I don't have the prior numbers off hand) what we were seeing was that no one ever used the small tanks, instead opting to go directly to the large tanks every time due to the price/capacity ratio being askew in the other direction.

Based on the numbers you've provided, it sounds like we achieved that at least! ;) Really though, they're at least fairly close in terms of cost/benefit now, though the capital outlay for the large tanks is a hurdle that has to be overcome obviously.

Totally open to your suggestion on what numbers you think would make sense to strike a good balance here. For clarity's sake, the intent on our side is largely to ensure that both are viable options -- each being a "right tool" for a given airport's job, or point-in-time of gameplay -- with the larger tank being slightly more ideal but coming with a somewhat burdensome capital outlay.

FWIW, at some point in the future we'll be sitting down and going through these kinds of balance details much more closely; at the moment though we're generally spending our time either fixing bugs or adding systems/content, the latter of which often can throw off balance further meaning re-work (and number crunching for balance on the whole is more time consuming than we'd have ever realized!). :)

If you've got some numbers that make sense, we're all ears though -- we really love this kind of specific feedback!

[Crai-Crai]

@LVGameDev - thank you for the reply. Good to know the dev is listening and still making progress.

I get that it was imbalanced the other way, at 10x the volume. Glad to know you were taking that gameplay into account.

I gave it a little thought and crunched some numbers.

A 314,159 L cylindrical tank (to use a "round" number) at a diameter of 120 metres would be 28 metres tall. That's 394 feet across and 92 feet high in American.

A 1,000,000 L cylindrical tank, at a diameter of 180 metres, would be 40 metres high. That's 590 feet across and 131 feet high. Interestingly, MS Calculator gave me the sidenote that this is equal to 2.37 jumbo jets across and 0.53 jumbo jet lengths high. (I once worked on a $30,000,000 contract building 14 tanks for an oil project, and I don't think any of them were that big.)

Have you considered underground tanks? These are pretty huge tanks to take up space on ground level, if they are going to be realistic.

If you want to create an interesting choice between two tanks, how about underground vs above-ground tanks? The underground would have to be placed before putting any runways or buildings on top of them (or you'd have to demolish the surface structure and rebuild after putting the tank in). The above-ground tank would take up valuable real estate on ground level, and would probably have to be small volume.

Would players be upset about losing the 1,000,000L tank if they got another option instead?

[RoxiSinister]

Yeah, it would be 6 small tanks for the 8x6 footprint. I always use the smaller tanks because they're easier to work with and cheaper to buy.

So, I did some sensible numbers on volume. I used inches in the measurements so I could arrive at cubic inches to then convert to gallons and finally liters. I'm an American...sue me. ;)

A vertical cylinder (large tank) measuring 28 ft (8.5m) wide by 50 feet (15.24m) high would have a volume of 230,307 gallons (871,808L), which is a reasonable measurement for a larger tank, IMO.

Using those numbers I approximated a smaller tank at the previously used scaling (48 inches per tile) to come up with a smaller tank. It would be 8ft (2.4m) wide by 32ft (9.75m) long and have a volume of 12,032.4 gallons (45,547.6L).

The smaller tank should cost more per gallon/liter than the larger tank, but the larger tank should be a financial hurdle to attain because of its size. Perhaps using similar scaled volumes, the smaller tank should stay as is, and the larger tank should be closer to $500k to build? Just some thoughts.

EDIT: I should add, that is roughly a 17.5:1 ratio on volume.

EDIT: Also notable, a Boeing 747 has a fuel capacity of 48,445 gallons (183,380L). In contrast, an A320 has a capacity of 7,185 gallons (27,200L)

[LVGameDev]

Awesome stuff. Here's what I'm hearing as "actionables" -- though hopefully not totally whiffing! =D

• Large tank: increase cost to ~$500k, decrease capacity to 871k liters
  
• Small tank: leave cost at $22.4k, decrease capacity to 45k liters
  
• Add underground fuel tank; requires level -1 and nothing above it on level 0 for placement & until construction is completed

Let me know if that sounds right & agreeable -- if I've gotten anything wrong I apologize, please definitely do correct me. Whatever we come up with here we'll be getting into the current edge dev cycle for sure. :)

Edit: Underground tank, let's make its footprint occupy Level -1 and Level -2 w/ the connector on Level -1. So it'd require Level 0 be 'clear' for placement & during construction, and it'd occupy -1 and -2 permanently.

[RoxiSinister]

Well, my numbers are not tne end-all, be-all, per se. They are just a guide for scaling. I think the original comment from Crai-Crai was along the lines of they are not really scaled correctly to one another and need further balancing, both in capacity and capital expense.

A 50 foot high tank might be too tall for an airport...I don't hang around airports often, and when i do it's always as a passenger. Alternatively, it might be too short, or too narrow, or capacity too low. They just need to be scaled better so they are both viable. Big tanks would be expensive and only found in very large airports, while small airports would utilize the smaller tanks as their flights have lower capacities to consume.

What I can tell you is this. With a fuel farm as it stands right now, if you can buy 6 million liters at $0.75, it will last a medium sized airport a couple of months (~60 days) being sold at $2.00/L and you'll make a ton of money from it with a crazy low overhead for having it around. With the new small tank capacity it only takes a handful of tanks, so it doesn't take a lot of space for the tanks to hold it, and you'll sell to around 20% of your flights while it's below $1.30/L at market. If it goes above that, you'll sell even more (but with lower profits if you don't modify selling price).

Here are some ideas on dimensions of various fuel tanks with their capacities: https://www.engineeringtoolbox.com/fuel-oil-storage-tanks-dimensions-d_1585.html

EDIT: I guess the real question is, "How do you, the dev, imagine the in-game scaling?" My numbers assume a ~1m square tile. The medium planes (737, A320)would then be ~15m long, which seems awfully short. Maybe a 2m tile is more realistic scale. They would then be ~30m, which is still a tad short in reality, but much closer. If this is assumed correct, then the tanks would be double my capacities as they would double their dimensions.

[RoxiSinister]

Also, I LOVE the idea of underground tanks!!!

[LVGameDev]

I also really like the idea of the underground tank -- it's actually being worked on by our artist right now even! :)

Okay, so scaling is a tough one, and its been talked about a lot. Originally, and still true (though we sometimes wish differently) really, there are two distinct in-game scales. An "outdoor" scale and an "indoor" scale.

For the most part everything in each respective category is scaled roughly right relative to other objects in that category. Some exceptions definitely apply and for varying reasons including gameplay / time-scaling concerns, performance, and even just legacy reasons (ie runways were originally 40 tiles long & no other sizes/options or upgrades existed, hah).

Basically though, the outdoor scale is scaled substantially smaller -- just looked through notes for the numbers we used back in early 2016 and can't find them off hand, though have posted them on here in the past too (most new stuff is just done relative to existing as far as sizing goes) -- but yeah, that's really the gist on the history of the 'scale' topic. :)

[LVGameDev]

As far as absolute terms, the main driver of the original fuel tank capacity settings was that we went with (IIRC) realistic numbers for the respective aircraft capacities, so we just wanted to ensure that the tanks weren't so severely under-sized to be useful (or completely emptied) by a single fueling.

At the time things were much different, though -- the in-game economy didn't "chug along" quite as well as it does now generally speaking. Being able to afford & construct a 'fuel farm' wasn't really a thought that concerned us, or really even entered our minds. :)

[Crai-Crai]

I really messed up my volume calculations there. Thank you CobaltGirl for the reality check. I forgot to convert cubic metres to litres. Good thing I'm not a pilot or ramp agent.

So a 6m diameter by 12m length, similar to current art for small tank, gives you 340,000L. This would fit nicely underground and take up -1 and -2 as you suggest.

I like the actions you came up with.

[Crai-Crai]

Could we have small, medium and large sized tanks? Unless players won't use them.

[LVGameDev]

Current thinking -- and subject to change as always, based on ideas & feedback -- is for the underground tank to be an "XL" tank. Reason being that it will have the most advanced / difficult requirements: ground floor clear for placement/construction + occupies the entirety of its footprint on both -1 and -2.

[RoxiSinister]

Also, I like the numbers I gave earlier. Even if you double the calculated tank dimensions (to better fit with other outdoor objects) they make good sense to me, which would be 90k for small tank and 1.6M for large tank, and then came up with a figure to base the cost of each tank based roughly on capacity, I think they would work quite well. Cost could maybe be caculated at $0.50 per liter for small, and $0.40 per liter for large? With the doubled numbers, it would be ~45k for small tank and ~640k for large, which is reasonable, IMO.

Originally posted by Crai-Crai:

So a 6m diameter by 12m length, similar to current art for small tank, gives you 340,000L. This would fit nicely underground and take up -1 and -2 as you suggest.

Actually, it would be about 170k liters.pi*r^2*l = (3.1417)(3*3)(12) = 169.464 cubic meters, which converts to 169646L. Now it is much easier for me to use cubic feet instead of cubic meters, personally, so my math may be incorrect...but I am pretty sure 1 cubic meter is 1000 liters?

[LVGameDev]

What's hilarious is that, some how, we ended up with the actual "config" for this on our end being in milliliters (we're US based). Haha. I'd have to look up the conversion TBH.

I'm a little confused now actually -- the numbers you've got here are approximately 2X what was outlined, which I can get onboard with, mainly just want to understand "the why" so we can be informed enough to reason about it intelligently too. =D