Different frames

[minnow]

Was at the Tampa RV show looking for a 30' +/- fiver. Found a few that we liked the floor plan. Comparing a couple different manufacturers where the floor plan was darn near identical. However one has a net carrying capacity of 1500 pounds and the other was nearly double. Given that these were the same length and layout, I assume (?) the frame on the lesser NCC unit is less robust ? Is having a NCC of 1500 lbs not practical ? Our current fiver has a NCC of 2800 lbs and although 10 years old now, has held up very well. I don't want to buy a new unit with a weak frame.

[Mile_High]

Like most are saying here, check the axles each are using on the tag by the left front - GAWR, and you might see the difference, and also look at the tire size amd capacity. Both are used to calculate payload. Has nothing to do with the frame.

Gross weight is just axle/tire capacity plus estimated pin weight.
Cargo capacity is just what is left of the gross after they subtract the empty weight.

Ours came with an axle option - it we gained 2,000 lbs of cargo capacity on the sticker over the standard factory units just by ordering the higher capacity axles and tires. Still the same frame.

[Dayle1]

minnow wrote:
Thanks to all that have replied. So, in the grand scheme of things, how much the NCC differences between two similar floor plans and similar length be considered then? If brand X has a NCC of 1500 lbs and brand y is 2500 but brand X was 2 thousand less which would you choose(again given that both are very similar floor plans and are within inches of each other on length).

I would consider 1500 lbs as the minimum NCC, but more would be better because that means the running gear, etc. will have more safety margin when typically loaded. And I would have to look more closely into why there is a 2000 lb difference in dry weight because it is very unlikely that a bunch of minor details will result in that much weight difference. In my mind the big differences to look at are: 1) electric or hydraulic slide-outs vs cable or Schwintek slide-outs. Really, under floor vs above floor mechanisms. 2) one or two layers of lauan backer board behind the exterior fiberglas skin (or even aluminum siding vs. fiberglas siding). 3) type of wall construction and frequency of studs. 4) height and gauge of the main frame rails.

Lighter weight does not necessarily mean inferior. Vacuum laminated walls with minimal studs and single layer lauan can be much lighter yet still stronger than hung-wall methods. And a lighter body means a lighter frame will work. But light weight slide mechanisms are also a must and they may be problematic for some owners.

[minnow]

Thanks to all that have replied. So, in the grand scheme of things, how much the NCC differences between two similar floor plans and similar length be considered then? If brand X has a NCC of 1500 lbs and brand y is 2500 but brand X was 2 thousand less which would you choose(again given that both are very similar floor plans and are within inches of each other on length).

[geotex1]

Dayle1 wrote:

geotex1 wrote:
Perhaps one has standard windows and the other has dual-pane (glass adds a lot of dead weight).

Reality check. Glass weighs 161 lbs per cubic foot. 50 square feet of window area, 1/8 inch thick glass. That extra pane of glass is 0.52 cubic foot or 84 lbs extra weight. Very minimal impact.

Thanks for the reality check. We use 1.64 lb/sq ft for 1/8" tempered glass. However, my point must have not been clear. That is, a culmination of many "little" and "unseen" items in two identical floorplans can erode CCC when considering the summation of their dead load. Identical floorplans don't indicate identical window coverage, which I was trying to get at, and the unit weight of glass is more than the unit weight of typical composite camper walls.

[laknox]

Old-Biscuit wrote:
Cargo carrying capacity is derived from 'unladen weight' subtracted from GVWR

Unladen weight is based on construction materials...wood/aluminum studs, thickness of plywood--roof/subfloor, furniture/appliances, components etc.

GVWR is based on frame, axles, tires ratings etc.

2 similar/identical floorplans.....not necessarily same construction/components

You can only turn a shoe box so many ways :B

My published specs are over 4000 CCC. I've got 3 45 gallon tanks; full, that's 1100 lbs. 2 full propane tanks is about 55 lbs; 2 6v batteries is about 140 lbs. This is about 1350 lbs; I =know= I'm not loaded with 2650 lbs of clothes, food and "stuff". My only conclusion is they weighed (or simply estimated) the "dry weight" with NO interior installed at all, just the frame and shell, then count the interior as part of the "cargo". Given the usual b.s. the manufactures play with the numbers, this shouldn't surprise anyone.

Lyle

[Dayle1]

geotex1 wrote:
Perhaps one has standard windows and the other has dual-pane (glass adds a lot of dead weight).

Reality check. Glass weighs 161 lbs per cubic foot. 50 square feet of window area, 1/8 inch thick glass. That extra pane of glass is 0.52 cubic foot or 84 lbs extra weight. Very minimal impact.

[Bamaman11]

Old-Biscuit wrote:
Cargo carrying capacity is derived from 'unladen weight' subtracted from GVWR

Unladen weight is based on construction materials...wood/aluminum studs, thickness of plywood--roof/subfloor, furniture/appliances, components etc.

GVWR is based on frame, axles, tires ratings etc.

2 similar/identical floorplans.....not necessarily same construction/components

You can only turn a shoe box so many ways :B

The published dry weight is what the manufacturer's projected the weight will be before adding your personal possessions or any fluids carried in your tanks.

Unfortunately, my 2015 fifth wheel ended up being about 500 pounds more than the builder's estimates. And it's 700 lbs. heavier on the kitchen/entertainment side than on the couch slider side.

Last thing manufacturers do as their trailers roll out of the factory is roll them over a set of certified scales.

[benb21601]

Axles and tires are going to have more to do with cargo capacity than frames. One is prob on a pair of 6000lb axles vs the others 5000lb. Unfortunately lippert makes the vast majority of frames in the industry and they will be very similar between manufacturers. Check axle capacity and check tire weight ratings... That's where you will find the difference between the two.

[Old-Biscuit]

Cargo carrying capacity is derived from 'unladen weight' subtracted from GVWR

Unladen weight is based on construction materials...wood/aluminum studs, thickness of plywood--roof/subfloor, furniture/appliances, components etc.

GVWR is based on frame, axles, tires ratings etc.

2 similar/identical floorplans.....not necessarily same construction/components

You can only turn a shoe box so many ways :B

[laknox]

I often have questions about how the different manufacturers actually come up with "dry" weight and cargo capacity. My FW just baffles me that it can carry 4,000+ lbs of "cargo". I've often suspected that the entire interior is counted as "cargo".

Lyle

[geotex1]

What leads you to believe it's the frame? Could be the axles used. They could honestly have the exact same frame and running gear from say Lippert and even the same floor plan, but wall and roof framing may be significantly different. Perhaps one has standard windows and the other has dual-pane (glass adds a lot of dead weight). There are too many variables to the possibilities for the difference without providing the actual makes, models, and options considered.