Skinning - Steel Gauge

[Curious Slug]

So we are outsourcing our roof-raising needs, which is going well so far. We've just been quoted for the new steel to skin the sides, two options and I wanted to source some advice -

26g 'Flashing' for $390

or

20g for $979

Steel isn't my forte. Hence the outsourcing. We are committed to making the bus as strong as possible but wondered if there was a discernible difference between thickness for skinning? The fabricator said that he was concerned about noise levels ('tin canny-ness') with the thinner stuff, but when I said that we'd be spray foaming he said that this wouldn't be an issue.

Any thoughts?

[Pizote]

20g is just under 1mm thick. 26 is just under .5mm thick.

IMO half a mm thick is not enough. Easy to ding/dent/scrape/rip/etc.

Any vertial sheet will help with structure but 26g might tend to wrinkle. Just look at the big rig trailers their sides at all wrinkled. My guess is that they are using 26g.

Weight is also a consideration. What’s the weight difference? How much wiggle room do you have between stripped and GVRW.

[o1marc]

Originally Posted by Pizote

20g is just under 1mm thick. 26 is just under .5mm thick.

IMO half a mm thick is not enough. Easy to ding/dent/scrape/rip/etc.

Any vertial sheet will help with structure but 26g might tend to wrinkle. Just look at the big rig trailers their sides at all wrinkled. My guess is that they are using 26g.

Weight is also a consideration. What’s the weight difference? How much wiggle room do you have between stripped and GVRW.

GVWR is determined by the builder of the vehicle, that would be you.

[Pizote]

Originally Posted by o1marc

GVWR is determined by the builder of the vehicle, that would be you.

Umm... I think this is incorrect. GVWR is determined by chassis and drive train configuration.

If you take a Tacoma pickup and remove the bed to make a shell and decide the GVWR is 28,800lbs, your frame will bend, crack, etc.

I know that on my CE300, the GVWR is 28,800 but change the pinion gears and that weight will change. Remove springs, that rating will change. Same with brakes, transmission, tires, axles, engine, frame, etc. All together determine the GVWR.

[Pizote]

Originally Posted by o1marc

GVWR is determined by the builder of the vehicle, that would be you.

Here's a definition that came from the interwebs...

The gross vehicle weight rating (GVWR), or gross vehicle mass (GVM) is the maximum operating weight/mass of a vehicle as specified by the manufacturer[1] including the vehicle's chassis, body, engine, engine fluids, fuel, accessories, driver, passengers and cargo but excluding that of any trailers.[2] The term is used for motor vehicles and trains.

The weight of a vehicle is influenced by passengers, cargo, even fuel level, so a number of terms are used to express the weight of a vehicle in a designated state. Gross combined weight rating (GCWR) refers to the total mass of a vehicle, including all trailers. GVWR and GCWR both describe a vehicle that is in operation and are used to specify weight limitations and restrictions. Curb weight describes a vehicle which is "parked at the curb" and excludes the weight of any occupants or cargo. Dry weight further excludes the weight of all consumables, such as fuel and oils. Gross trailer weight rating specifies the maximum weight of a trailer and the gross axle weight rating specifies the maximum weight on any particular axle.

[PNW_Steve]

We have used 18 gauge so far on ours. I would be reluctant to go any lighter than that for fear of excessive oilcanning.

[Jolly Roger bus 223]

A suggestion.
If you are spray foaming all of the interior.then me personally? I would use the metal from removed from the ceiling to skin the exterior roof raise areas and finish the ceiling interior with tongue and groove or a thin enough LUAN that will bend around the ribs.
My 86 bus is all 15-guage inside and out.
To me? I will only equal that or go better than that but I do steel and sheet steal/metal work for a living and have access to a shop for it.
Personally any guage in the 20's is to light for re-skinning and is going to require a lot of extra backing to keep it from twisting,warping, oil canning, or a whole lot of bondo to make the edges match the existing top and bottom. And then fill in between because you can't really taper bond? (You can ) but it would look more like an old 73-79 ford truck that a big indent rub rail in it that was removed and painted.
In my mind.
Good luck

[EastCoastCB]

Originally Posted by Curious Slug

So we are outsourcing our roof-raising needs, which is going well so far. We've just been quoted for the new steel to skin the sides, two options and I wanted to source some advice -

26g 'Flashing' for $390

or

20g for $979

Steel isn't my forte. Hence the outsourcing. We are committed to making the bus as strong as possible but wondered if there was a discernible difference between thickness for skinning? The fabricator said that he was concerned about noise levels ('tin canny-ness') with the thinner stuff, but when I said that we'd be spray foaming he said that this wouldn't be an issue.

Any thoughts?

As thick as you can work with. 18ga is about as perfect as you'll get. I've used some 20 for single window deletes but I wasn't 100% happy. Now I've got 6 sheets of cold rolled 18ga. I get em in 4x10 for 60 or so depending on the wholesale pricing.

[Jolly Roger bus 223]

Sorry. Indent on an old ford where the rubber rub rail was removed.

[o1marc]

Originally Posted by Pizote

Here's a definition that came from the interwebs...

The gross vehicle weight rating (GVWR), or gross vehicle mass (GVM) is the maximum operating weight/mass of a vehicle as specified by the manufacturer[1] including the vehicle's chassis, body, engine, engine fluids, fuel, accessories, driver, passengers and cargo but excluding that of any trailers.[2] The term is used for motor vehicles and trains.

The weight of a vehicle is influenced by passengers, cargo, even fuel level, so a number of terms are used to express the weight of a vehicle in a designated state. Gross combined weight rating (GCWR) refers to the total mass of a vehicle, including all trailers. GVWR and GCWR both describe a vehicle that is in operation and are used to specify weight limitations and restrictions. Curb weight describes a vehicle which is "parked at the curb" and excludes the weight of any occupants or cargo. Dry weight further excludes the weight of all consumables, such as fuel and oils. Gross trailer weight rating specifies the maximum weight of a trailer and the gross axle weight rating specifies the maximum weight on any particular axle.

When I strip the bus and build an RV I become the manufacturer of that vehicle and I alone set the GVWR to what I want. There is no benefit to change it to a higher GVWR because the fees go up accordingly. But I can lower it to less than 26K lbs for my build and as long as I don't exceed that I'm good, and the registration fees drop substantially.

[Pizote]

Originally Posted by o1marc

When I strip the bus and build an RV I become the manufacturer of that vehicle and I alone set the GVWR to what I want. There is no benefit to change it to a higher GVWR because the fees go up accordingly. But I can lower it to less than 26K lbs for my build and as long as I don't exceed that I'm good, and the registration fees drop substantially.

IMO it's all about structural engineering, not what I want. We just have differing opinions.

[o1marc]

Originally Posted by Pizote

IMO it's all about structural engineering, not what I want. We just have differing opinions.

My opinion coincides with the federal governments.

[Pizote]

Well I’ve never know the overnment to have a valid opinion ;)

They also state technical guidelines. Not wants and wishes.

It would be interesting and educational to see the federal opinion that places what a manufacture wants over engineering specifications. Can you provide a reference for me to read?

[o1marc]

Originally Posted by Pizote

Well I’ve never know the overnment to have a valid opinion ;)

They also state technical guidelines. Not wants and wishes.

It would be interesting and educational to see the federal opinion that places what a manufacture wants over engineering specifications. Can you provide a reference for me to read?

No, but feel free to waste your time trying to prove me wrong.

[Tango]

Best bet is to mike the existing skin and match it. Most skoolies seem to be between 15 -16-18 (several use metal to their own specs...like BB).

[Curious Slug]

Ignoring the GVWR thing, thanks for everyone's comments.

I've asked for pricing on 18g, suggested we consider the roof panels (Good suggestion, I'd forgotten about these) and will check what the original sheeting was. Sounds like the flashing is a no-go, not really worth the risk of it looking crap - we'll use minimum 20g.

I really appreciate the help everyone!

[Ninjakitty]

I used 20 ga galvanealed (paint ready) steel. I spray foamed 2"~ inside. No issues at this point

[bus-bro]

Has anyone used Filon (reinforced plastic) for this. They use it on motor coaches, hi-end RV's and semi-trailers for siding.

Not that I did a roof raise, but I bought a roll of it and, among other things, used it to blank half (and counting) of my bus's windows.

Regardless, it's great stuff to have around for bus building. Though I would question those who use it for things like sink backsplashes, as I have done.

[Ninjakitty]

Originally Posted by bus-bro

Has anyone used Filon (reinforced plastic) for this. They use it on motor coaches, hi-end RV's and semi-trailers for siding.

Not that I did a roof raise, but I bought a roll of it and, among other things, used it to blank half (and counting) of my bus's windows.

Regardless, it's great stuff to have around for bus building. Though I would question those who use it for things like sink backsplashes, as I have done.

I think that stuff would be good for blanking windows from the inside, especially if you could get some commerical grade vhb tape. The good stuff that they're using on trucks and trailers now

[culpspecial]

The manufacturer of the chassis usually determines the GVWR according to engineering specs. The the body manufacturer that installs the coachwork will come up with a number depending on the weight of the coachwork Springs, suspension, tires, frame etc figure into it. You should be able to find the tag on the bus and go by that as it was probably figured full of people, two to a seat etc. as to what your gross weight for the vehicle can be. And there is probably a fudge factor figured in there.
Hope this helps.