2021 Interstate Lounge Ext Net Carrying Capacity (NCC) Confusion

[BeachBrad]

Newbie Question!

We have a 2021 Interstate Lounge Extended 4x4 where the GVWR is 11,030 lbs, Unit Base Weight is 10,011 lbs > therefore the Net Carrying Capacity is 1019 lbs. The unit says it has seating capacity for 7. If the average adult is ~150 lbs, the weight of just the passengers alone would be 1050 lbs (exceeding the NCC).

This wouldn't allow for any additional weight in the Interstate (no water, no cargo). The NCC accounts for people as well as water (fresh/grey/black) + anything you put in the unit right?

While we don't intend to have 7 adults driving around in the unit, I'm really confused as to why the Interstate is rated for 7 people but not built to accommodate that amount of weight?

Also, the NCC of this unit seems to severely limit how much weight you could put on the rear hitch (ie like a bike rack/cargo basket).

tx for helping me understand these weight topics better. just want to be safe on the road / not overpack.

[Coffee Break]

Brad-
Look at the yellow sticker on the passenger door. This is your OCCC.

Occupant & Cargo Carrying Capacity. This is how much weight you can carry. The Weight of all passengers, weight of your water, and weight of your cargo should not exceed this number.

[billstrong]

I share your pain!

My understanding is that NCC is calculated differently by different builders. You can’t hang your hat on it without knowing exactly how Airstream calculated the NCC.

The photo is of the only sticker on my 2021 AI Nineteen 4x4. This sticker next to useless. It only leads to confusion. The UVW 7784 lbs is confirmed correct by my weighing of my van and the GVWR 9039 lbs is what it is. But WTH is “cargo”?

In my case I weighed my van to determine how much I can carry. So far I have weighed my van on 3 occasions on two different sets of scales. It turns out that my van can carry 439 lbs of what I would call cargo. That is based on my weighing the van with 400 lbs of people, 50 lbs of winterization antifreeze, 12 12 oz bottles of water, 25 gal of diesel, 6.5 gal of DEF fluid and full washer, engine and transmission fluids and 150 lbs of stuff. My total weight is 8400 lbs on certified scales. For calculations I add 350 lbs for full tanks although they rarely would all be full. So there is some leeway with tank weight if you are careful with it.

8400 - 150 + 350 = 8600 lbs

9039 - 8600 = 439 lbs true “cargo” that I can carry including extra people and stuff.

So go weigh your van knowing exactly what your fluid levels are, with nothing in the van unless you want to weigh it with people onboard, and start your figuring there.

You will also want to weigh your van fully loaded with your people onboard to determine front axleweight and rear axleweight to make sure that you are safe and are using the correct inflation pressures.

BTW that Front 47 psi listed on the sticker is inadequate to safely carry my fully loaded front axle IMHO. My axleweights are only 320 lbs different.

IMHO “Cargo” is a nebulous legal copout to keep themseves from being nailed down in a lawsuit.

[billstrong]

P.S.

I feel that I must know I am of a safe weight and that I must be able to prove that I made the effort to comply because if I cause a significant accident then probably the first thing the opposing side will do is weigh my van (some may say not so, but it is not so only until it is so). And besides, I want to know that I am as safe as possible anyway.

The term “ Cargo” should have a strict legal definition. I’m not sure it does. And whenever used on a label that definition should be spelled out as to what it includes and more importantly what it does not include.

Stepping down now.

[B. Cole]

It seems like these Interstates share a common theme- Built overweight.
Right out of the factory gate.
It just is what it is...

[billstrong]

Back up on the soapbox again:

IMHO this “people carrying capacity” thing is the DLS (dirty little secret) of the RV industry that continually blindsides the uninitiated. I know it did me. But fortunately I carry only two people. There is no way I can carry 800 lbs of people and a decent amount of gear even though I have four sets of lap and shoulder belts. The back seats would not be comfortable anyway because of the seats themselves and because of van motion. If I could remove the 4x4 system from my van that would give me another 400 lbs capacity. Then it might be possible.

Don’t get me wrong, I love my AI Nineteen 4x4 and would not want any other RV. But I am discovering that as in all things where you have to put up with a lot - ya gotta love it. And I do.

[SWH]

And the Atlas is even worse!

One thing I don’t understand is why the GL is heavier than the GT. It doesn’t seem like the two captains chairs in the GL would weigh more than the extra cabinetry in the GT.

[preedtx]

I believe an important factor in determining the number of passengers is the number of seats with "approved" seat belts. The nineteen can probably haul more than 4 passengers by weight but Airstream only supplies 4 seat belted seat positions.

[InterBlog]

OP, did you happen to notice my concurrent thread titled Catastrophic tire blow-out in an Interstate?

I have the first generation Interstate, where we face an even more stringent restriction, and in one post I noted "I estimate that Airstream produced our Interstate at 7,823 pounds, give or take. This on a vehicle with a GVWR of 8,550 pounds. Mind you, the thing has six seat belts installed in it. Do the math for yourself and you will see that it's ugly. Put a couple of chunky grandparents in there with a handful of grandkids and a case of Pepsi, and they'll be bumping up against GVWR before they even load in their toothbrushes."

TL;DR - I am responding to the butt-heavy van phenomenon by engaging a number of strengthening measures at this time. Husband and I owned the thing for years before we had a blow-out, but once bitten, twice shy. In doing research post-blowout, I encountered a disquieting number of posters on other forums who have blown tires on Sprinter camper van conversions for no discernible reason (no debris/puncture evident, no tire overloading, no excessive speed, no excessive wear). That prompted me to re-evaluate my own approach, with an eye toward building in greater safety margins.

Anyway, my point being, you can re-jigger your cargo, but only up to a point, and you are never going to escape the reality of your van's weight. Your job is to parse that in terms of how you feel you should best respond to it. That deduction is different for every owner. For me at this juncture, it's changing out my Load E tires for Eurometric C tires, a new TPMS system, and suspension upgrades (I'm omitting a lot of detail for brevity as it's being covered here and also here and on another thread not yet launched).

[Lily&Me]

I appreciate that you love the challenge brought by various upgrades and tweaks to your rig, IB, but are you concerned that you are trying to push it beyond its intended limits by trying to get it to successfully carry more load?

You’ve had an engine failure and tire blowout in less than a year, when your rig is probably better cared for than any other here.

Just sayin’...not all challenges are meant to be met.

Maggie

[BeachBrad]

first, you guys are great. thank you so much for all the thoughtful responses. I will definitely read the posts that you reference (ex. tire blowout one). we recently installed the TST 507 Series 6 Flow Thru Sensor TPMS system (had to buy 2" metal valve extenders for the rear inner tires)...so HOPEFULLY that, combined with being careful with weight (per all of your great advice) will help.

As you can probably tell, we're trying to "plan smart" so we don't overload the Interstate. As I added up the water tanks (grey/black/fresh) at an assumed 75% full each (probably not likely but just wanted to play it safe) + another 5 gallon portable water jug that's about 400 lbs of water. mom/dad/child another 365 lbs. that right there is 75% of our NCC leaving about 254 lbs for "cargo" if we maxed out at the full NCC. I've seen on other posts people putting bikes on the back (that might be another 90 lbs for 3 bikes), extra cooler for food storage b/c the interstate fridge is so small (another 50-75 lbs?), some even carry an extra generator for boondocking....the NCC seems to fill up fast.

It SEEMS like making sure the grey/fresh/black water systems don't all simultaneously come close to 75% filled up is the biggest variable you can control to keep the weight down (other than not loading it up with people I suppose).

anyway, thank you again for all the advice. this community is great.

[coasttocoast]

Two's company, three's a crowd.
Keep it light, and keep it simple.
Some people will load an Interstate up with pots and pans and try to cook.
Seriously?
You can easily use a hitch-mounted rack or cargo box and carry stuff.
Just don't exceed the capacity.

[Lily&Me]

Originally Posted by BeachBrad

It SEEMS like making sure the grey/fresh/black water systems don't all simultaneously come close to 75% filled up is the biggest variable you can control to keep the weight down.

I agree with this, also the overall approach as much as possible that “lighter is better”, whether that is cookware, clothing, food, dishes, etc.

I fill with fresh water when I empty tanks, repeat as needed.

Maggie

[InterBlog]

Originally Posted by Lily&Me

I appreciate that you love the challenge brought by various upgrades and tweaks to your rig, IB, but are you concerned that you are trying to push it beyond its intended limits by trying to get it to successfully carry more load? ...

No, I'm trying to be more responsive to the load dynamics that the van naturally experiences, in order to expand its safety margin.

Expand its safety margin.

Expand its safety margin.

Everyone please internalize the fundamental difference between that ^^, and "carry more load". The former reflects good engineering practice; the latter is a reductionist oversimplification.

History is full of examples of engineering that was "supposed" to account for all stresses on a system such that an adequate safety margin was provided by design. But if hidden variables are not accounted for, failures routinely occur. The Hyatt Regency walkway collapse. The Florida International University bridge collapse. Closer to topic, here's an article titled Five of Car Engineering’s Biggest Blunders.

Some hidden element of engineering insufficiency MAY OR MAY NOT be the reason for one or more of my van failures - I have no way of determining this. Our rigs are rated for a certain mass, and our tires are rated for a certain load, and our engines are rated for a certain turboboost, and all of those things can be kept within their proper operating ranges, and the rig can STILL fail if there are hidden additional variables exerting on the system that are not properly accounted for in its design.

These are still inherently experimental vehicles, and the variables are not completely understood. Therefore, it makes good engineering sense to harden the vehicle if repeated failures occur, even if the failures appear like they might be unrelated. It's a well-established means of essentially taking pot shots at potential variables that can't necessarily be identified on their faces.

[Titus]

While I haven't bought one yet, I am going to try the Blueskysea T-650WF for a TPMS. It is available on Amazon for $120 - far less than the price of a TST 507. Specs seem very similar - and the sensor actually weighs less than the TST cap sensor. I could find nothing on-line but they were very responsive to my request for an operators manual. The setting instructions are a bit confusing but it seems to have the features I want.

[InterBlog]

Originally Posted by Titus

While I haven't bought one yet, I am going to try the Blueskysea T-650WF for a TPMS. It is available on Amazon for $120 - far less than the price of a TST 507. Specs seem very similar - and the sensor actually weighs less than the TST cap sensor. I could find nothing on-line but they were very responsive to my request for an operators manual. The setting instructions are a bit confusing but it seems to have the features I want.

This South African page suggests that it is intended for a 4-wheeled vehicle towing a 2-wheeled trailer, for a total of 6 wheels. And yet the receiver, by design, implies dually. Weird.

Do you have a direct link? I can't find it on Amazon - maybe they pulled the listing. All I can fetch is (paste) "Brands related to your search".

[InterBlog]

Aside on van masses generally:

An interesting DIY build can be viewed here, not directly comparable to the OP's because this one is not an EXT. Nor is it directly comparable to mine despite being a Sprinter 2500, because this is an NCV3 whereas mine is a T1N. But it's a point of reference.

The builder states his loaded weight at 7,600 pounds.

Impressive - why so low? Because he was selective in his design and use of materials.

Moral of the story: Camper vans do not have to be as heavy as Airstream Interstates tend to be. It takes research, time, and money to do it differently, but lower weights can be achieved.