dton frame of reference

[Matt Wilson]

[edit: didn't format the table, so I swapped for an image]

I've seen the article in freelance traveller about tonnage and some of its examples. What I would find handy is a general guideline of what that tonnage range compares to. Has anyone ever put together a chart like this? I couldn't find one so started making my own.

I'm trying to stick with WWII ships as much as I can, since a) the size-to-class relationship changes over the TLs, and b) I like ships of this era. I'm not sure what a good example from this era would replace the 50-70 ton range of modern-ish CG patrol boats (e.g. USCGC Sea Fox).




Thoughts? Suggestions?

 

[bookwyrm]

Something like this would make it easier to create ships in a small ship universe with something to compare them to without having to do all the math conversions and 'dtons' of research online. (yeah, I'm a little lazy, usually)

There are a number of posts on the CotI that do a comparison of ships from historically wooden to modern steel based on dtons.

 

[coliver988]

I think for current real-world ship displacement the below is valid. I back spaceships from 0Hr and the 3d model gives displacement, so I can convert the ships to Traveller dtons. not that there is ever enough fuel for jump-capable ships but I can wing that

First, 1 ton is 100 cubic feet. This is 2.831685 cubic meters, and when dividing by 13.5, gives you .2098 Traveller tons per 1 "standard" ton. So simply multiply his tonnage by .2098 and you get Traveller displacement.

dTons = 0.2098 x tonnage​

 

[whulorigan]

I think for current real-world ship displacement the below is valid. I back spaceships from 0Hr and the 3d model gives displacement, so I can convert the ships to Traveller dtons. not that there is ever enough fuel for jump-capable ships but I can wing that

First, 1 ton is 100 cubic feet. This is 2.831685 cubic meters, and when dividing by 13.5, gives you .2098 Traveller tons per 1 "standard" ton. So simply multiply his tonnage by .2098 and you get Traveller displacement.

dTons = 0.2098 x tonnage​

Or you can be lazy and say it's a 5:1 ratio, std tons to dtons, as a quick rule of thumb.

 

[FreeTrav]

Or you can be lazy and say it's a 5:1 ratio, std tons to dtons, as a quick rule of thumb.

Yes, this is close enough for our purposes, especially since the de-metric-ized GURPS Traveller made the displacement ton equal to 500 ft³.

For comparison, the exterior dimensions of a typical CONEX container is (in feet) 8 × 8.5 × 10 (or 20 or 40), for a total displacement of 680 (or 1360 or 2720) ft³, which probably makes them eyeball-compatible with 1, 3, or 5 Traveller dtons. It's not 1, 2, and 4 because of the excess in all three sizes; it adds up...

The 30-dton module for the Modular Cutter is 18m long, round in cross-section, and has a diameter of 7.5m. Set on end, for those of you familiar with grain silos and farming, this would be about 24.5 feet across (two lanes on a typical highway) and six-to-seven stories tall, near the lower end of size for grain purchasing stations.

 

[AnotherDilbert]

First, 1 ton is 100 cubic feet. This is 2.831685 cubic meters, and when dividing by 13.5, gives you .2098 Traveller tons per 1 "standard" ton. So simply multiply his tonnage by .2098 and you get Traveller displacement.

dTons = 0.2098 x tonnage​

Yes, for the old Gross Register Tonnage (GRT), but not the current Gross Tonnage (GT) rating, where
GT = V × ( 0.2 + 0.02×log₁₀(V) )
https://en.wikipedia.org/wiki/Gross_tonnage#Volume_from_gross_tonnage

Gross tonnage is also metric, so uses m³ and tonnes, unlike gross register tonnage which uses Imperial units.


Essentially V = K × tonnage_GT, where K is in the range [3 , 5], so about
Dton ≈ [0.2 , 0.35] × tonnage_GT, with 0.2 for very large ships and 0.35 for very small ships.


Example: A modern ship like M/S Viking Glory of 65.200 GT would have an enclosed volume of approximately V ≈ 3.2 × GT, or Dton ≈ 0.23 × GT ≈ 15.000 Dton.

A large yacht like Symphony of 3.000 GT would have an enclosed volume of approximately V ≈ 3.6 × GT, or Dton ≈ 0.26 × GT ≈ 770 Dton.

 

[TamsinP]

Yes, for the old Gross Register Tonnage (GRT), but not the current Gross Tonnage (GT) rating, where
GT = V × ( 0.2 + 0.02×log₁₀(V) )
https://en.wikipedia.org/wiki/Gross_tonnage#Volume_from_gross_tonnage

Gross tonnage is also metric, so uses m³ and tonnes, unlike gross register tonnage which uses Imperial units.


Essentially V = K × tonnage_GT, where K is in the range [3 , 5], so about
Dton ≈ [0.2 , 0.35] × tonnage_GT, with 0.2 for very large ships and 0.35 for very small ships.


Example: A modern ship like M/S Viking Glory of 65.200 GT would have an enclosed volume of approximately V ≈ 3.2 × GT, or Dton ≈ 0.23 × GT ≈ 15.000 Dton.

A large yacht like Symphony of 3.000 GT would have an enclosed volume of approximately V ≈ 3.6 × GT, or Dton ≈ 0.26 × GT ≈ 770 Dton.

I found this online calculator to go from Gross Tonnage (GT) to m^3:

Convert Tonnage (Ship Tonnage Measurements) to Cubic Meter (m³, Metric)

Online conversion from Tonnage (Ship Tonnage Measurements) to Cubic Meter (m³, Metric). Capacity And Volume Converter.

www.convert-me.com

I'm sure there are others out there.