Trailer payload calculation

[djbreslin]

When I received my Basecamp 20X, there was a sticker/document inside that listed my final trailer payload capacity (after modifications and with a full tank of water) to be 364 lbs. This seems approximately correct, but I can't account for about 55 lbs of it. I'm not overly concerned, so this is more of a fun puzzle than anything else.

3500 lbs - Airstream Basecamp 20X w/ full LP tanks and batteries (note: my AGMs are supposedly lighter than the stock batteries, but I've ignored that)
4 lbs - vent cover (estimate based on online info)
1 lbs - backup camera (my personal guess)
6 lbs - weBoost (the shipped package is 7.8 lbs, so I subtracted a bit for packing material and manuals)
29 lbs - standard rooftop solar (2 panels @ 14.25 lbs = 28.5 lbs, rounded up for mounting hardware)
22 lbs - additional rooftop solar (2 panels @ 10.78 lbs = 21.56 lbs, rounded up for mounting hardware)
192 lbs - full fresh water tank (the payload document said it assumed full fresh and empty black/grey; it listed full fresh as 192 lbs, which is 23 gal * 8.345 lb/gal)
22 lbs - microwave (it's 21.6 lbs per spec)
93 lbs - AC unit (I don't know the exact model number, but based on process of elimination, it can only be 1 of 4 models and those models are either 90 or 93 lbs, so I took the larger)
12 lbs - AC unit ceiling assembly (by spec it's listed as 3.5 - 12.5 lbs, so I just picked 12 lbs)
--------
3881 lbs - total weight
4300 lbs - Basecamp 20X max weight (GVWR)

419 lbs - remaining payload capacity per my calculations
364 lbs - stated remaining payload capacity per sticker in trailer

55 lbs - the mystery delta

Can anyone see what I might be forgetting that would help account for the 55 lb difference? I've rounded a few values up and ignored the lighter AGM batteries (so that delta could be even bigger, a bigger mystery), but perhaps I've also underestimated some of the mounting hardware (which would close the mystery gap a bit). It's also possible the base weight of the trailer is not exactly 3500 lbs anymore in 2022 due to minor design mods. I'm not sure if my dealer actually weighed the trailer or if they went off listed specs to do the calculation.

Anyway, just a fun puzzle if anyone has a thought...

[Dennis C]

Do you have a tankless or a traditional 6-gallon water heater? A full water heater is roughly 50 lbs.

[djbreslin]

Ah, good thought. I believe the Basecamps come with a tankless water heater.

[kdwalls]

Wonder if it’s the four gallons of unuseable fresh water (the tanks were listed as 27gallons until a month or so ago and changed as there is a slope or design flaw that limits access to that final 4 gallons) plus the weight of the cushions. Thinking cushions may be excluded from dry weight as they are removable.

[djb75]

Or perhaps a spare tire? Seems like that would be part of the dry weight, but if it's optional, then maybe not.

[djbreslin]

Originally Posted by kdwalls

Wonder if it’s the four gallons of unuseable fresh water (the tanks were listed as 27gallons until a month or so ago and changed as there is a slope or design flaw that limits access to that final 4 gallons) plus the weight of the cushions. Thinking cushions may be excluded from dry weight as they are removable.

The 4 gallon fresh water tank delta is a really good idea. I'm aware of that issue, but I didn't factor it into my calculations. Now that I have, I'm left with only a 22 lb difference between my calculated payload and the stated payload. That's a low enough discrepancy that I consider it "solved." Or more to my purpose, that I feel like I can calculate my payload accurately.

Thank you!

[djbreslin]

Originally Posted by djb75

Or perhaps a spare tire? Seems like that would be part of the dry weight, but if it's optional, then maybe not.

The spare tire is not an option, so I think that would be included in the dry weight. Thanks for the brainstorm idea though! Also, your username catches my eye... "DJB" are my initials.