GURPS 3e/V2e question: Explosive Reactive Armor weight

[Curmudgeon]

Originally Posted by dcarson

From a PDF I fond on msm.sk

Using the figures and coverage given in the PDF, we arrive at the following formulae and results, which suggest that you are actually looking at HRAP from VXi, with a weight errata being necessary:

Surface Area (using Complex Option for Armor by Location): 400 sq. ft. (turret) x 4/5 (facings, top of turret is indicated as being included in the ERA facings, which wasn't the case in the previous calculation) + 500 sq. ft. (body) x 4/6 (facings, top of hull also counts as an ERA facing which wasn't indicated earlier) = 320 sq. ft. (turret) + 333 1/3 sq. ft. (body) = 653 1/3 sq. ft. (total).

Total weight of ERA = 2700 kg. = 2.7 metric tons = 5,940 lbs.

Weight of ERA/sq. ft. = 5.940 lbs./653.33 sq. ft. = 9.09 lbs./sq. ft.

This is very close to being 9 lbs./sq. ft. As said, 90 lbs./sq. ft. seemed excessive, although as Rupert pointed out, not insanely so. It's possible that NEXREARM is, despite its marketing, effectively just RAP with a weight of 9 lbs./sq. ft. instead of 8 lbs./sq. ft., and thus just a difference between models that can be statted using the real world weight. On the other hand, it's also possible that it really is HRAP, which may indicate that the 90 lbs./sq. ft. was subject to a misplaced decimal point and should be the subject of an errata as 9.0 lbs./sq. ft.

Given that errata for Classic GURPS isn't the highest priority, I wouldn't necessarily expect it to be reported, assuming that an errata is needed.