Changing out heavy steel flatbed for aluminum

[Jfet]

Sorry for jumping around on topics here but we are brainstorming our camper setup and trying to explore options.

We were discussing upgrading our truck from a NRR to a F series or GMC T series truck to go from 19,500 GVWR to 25950 GVWR.

The problem right now is we are around 16000 GVWR with the camper and garage on the current NRR/flatbed leaving only 3500 pounds for passengers, cargo, fuel, water, motorcycles. Tight for an extended trip. I would really like an extra 1000 to 2000 pounds and the T series would give it to me.

The truck currently has a 20 foot steel flatbed which weighs a bit over 2000 pounds, based on scale measurements and the dry weight figure of the NRR from the body builder guide.

What if instead of swapping out our truck, which we put brand new M608Z tires and had injectors replaced, we instead had someone construct a 20 foot aluminum flatbed? What weight saving might we expect going from a 2000 pound steel flatbed with big headache rack to a aluminum flatbed with small lighter headache rack?

Would an aluminum flatbed support our camper and garage as well as the steel flatbed, in terms of strengthening the Isuzu frame rails?

I am including a few pictures to show our current setup. Thank you for any help/advice.

 

[dwh]

I don't have an answer on the steel vs. aluminum question, but it's a question I've wondered about.

One question I have is how much does that oak flooring in the bed weigh? How much would be saved by replacing the wood with say steel diamond plate or expanded metal mesh?

 

[Jfet]

I don't have an answer on the steel vs. aluminum question, but it's a question I've wondered about.

One question I have is how much does that oak flooring in the bed weigh? How much would be saved by replacing the wood with say steel diamond plate or expanded metal mesh?

Yes, that is a good question. How much does does that oil/water saturated weathered oak weigh compared to just a light surface such as what you suggest. Perhaps the wood is 500 pounds of the flatbed weight?

Another question is the funky way the frame was extended. It almost looks like the steel flatbed has been made into part of the frame extension to get the 20 foot length (the Isuzu frame rails stop right past the rear wheels). How would aluminum hold up to this extension section and how might one attach a trailer hitch for pulling a relatively light trailer (attach hitch just to aluminum flatbed or have a super long hitch going back to the steel frame rails?)

So many questions..

 

[dwh]

Well...not an expert in woods, but searching around, I came up with a weight of 3.9 lbs. per board foot for white oak (kiln dried). I roughed it as 20' x 8' so 16 2" x 6" planks of 20' each, which came out to 320 linear feet.

According to a board foot calculator I found, a board foot is 1" x 12" x 12" (or 2" x 6" x 12" which makes it easy) so to figure it, the formula is: Thickness (inches) x Width (inches) x Length (feet) / 12.

2 x 6 x 20 / 12 = 20 board feet per plank * 16 planks = 320 board feet.

320 board feet x 3.9 pounds per board feet = 1248 pounds.


Someone should certainly double check my math on that - but as near as I can tell, you're looking at more like 1200 pounds of wood in that bed, than the 500 you guesstimated.

 

[dwh]

According to this page on expanded metal, 1/2-13 XM (whatever the hell that is) with diamond holes of .5" x 1.2" weighs 1.28 pounds per square foot. 20' x 8' = 160 square feet. So 160 x 1.28 = 204.8 pounds.

So I'm guessing you could shave 1000 pounds or so off that bed weight by replacing the wood with expanded metal - which can be welded to the bed frame and should help maintain stiffness.

 

[dwh]

Hrmmm...forgot to add in the weight of the spacers - you'd have to put in 2" channel crosswise to bring the level of the crossbraces up to the level of the side rails after removing the wood. So add some more pounds there.

 

[Jfet]

Thanks for the work dwh.

I made some exact measurements of the wood bed. The boards are 19 feet 9 inches long and span 90 inches. They seem to be 1.75" thick.

I found that pressure treated wood (not sure how that compares to oil/water soaked oak) is 0.024 pounds per cubic inch.

Total cubic inches is 37327 times 0.024 = 896 pounds

That is in between our guesses and likely close.

Depending on the gauge expanded metal used, it would be around 200 to 300 pounds. Spacers could be light gauge tube and would not add more than 20 pounds or so.

This is looking like it would save us 500 to 550 pounds, which is significant and likely worthwhile. We could also cut down the headache rack to about 20 inches high which I have previously calculated would save 60 to 70 pounds.

Definitely would be cheap compared to other options.

 

[dwh]

The work is no problem - like I said it's a question I'd wondered about anyway. Just never got around to trying to actually figure it out.

No idea how oak compares to pressure treated weight wise. I do know that pressure treated dries out over time, and the weight goes down as it does. Still, 900 pounds sounds about right after you shave off the extra padding I added by rounding up the size estimates.

So figure a savings of 600 pounds or so. That bumps your usable weight up over 4000.

And yes, just a bit cheaper than a new truck.

 

[dwh]

Re-doing the math on the oak using your actual measurements comes out to 1011 pounds BTW. If the oak is heavier than the pressure treated, then your savings could be as much as 700 or 800 pounds depending on how much the new metal weighs.

 

[CodyY]

The savings will not be that dramatic.

Expanded metal will never hold up to the span between the lateral framing. It would be like trying to park on a chain link fence. A considerable amount of material will need to be added to support the mass, and make up the depth of the removed wood.

A much better option would be to replace the wood with an aluminum extrusion of similar dimension. Much like the floor of a Uhaul truck.

 

[Jfet]

The savings will not be that dramatic.

Expanded metal will never hold up to the span between the lateral framing. It would be like trying to park on a chain link fence. A considerable amount of material will need to be added to support the mass, and make up the depth of the removed wood.

A much better option would be to replace the wood with an aluminum extrusion of similar dimension. Much like the floor of a Uhaul truck.

Cody, yes I was thinking about this last night while trying to get some sleep. I was going over in my head how I might support and attach the expanded metal and thought about aluminum planks and if they exist. The span would take 22 four inch wide extruded planks that are almost 20 feet long. Another option would be to have some space between the planks which would still form an acceptable surface but use fewer planks.

I need to see what exists and if something exists that would be a light drop in replacement for the 1.75" thick wood. Thanks.

 

[riptilyaflip]

In general aluminum is 40% lighter than steel for the same load capacity.
For a quality 20'x8' aluminum flat bed with headache rack you could expect to pay around $7,000
I think in the end, you will be much happier with the bigger truck. More power, better braking and handling, safer.

 

[Jfet]

In general aluminum is 40% lighter than steel for the same load capacity.
For a quality 20'x8' aluminum flat bed with headache rack you could expect to pay around $7,000
I think in the end, you will be much happier with the bigger truck. More power, better braking and handling, safer.

I most definitely would be happier with a bigger truck but having put a decent amount of money into this truck I am not sure how much I am going to lose on the swap (new tires, new injectors, new interior seats, paying sales tax on purchase). Add to that my limited range and model (must be a 25950GVWR Isuzu F series or GMC T7500 that has no DEF (pre 2007) and is relatively low mileage and modern (so post 2000) and it gets to be difficult to find. They all seem to be in New Jersey or Florida

As a temporary measure to get us on the road, it isn't sounding too bad to ditch the wood for aluminum planks and save around 500 to 600 pounds. I am finding 6 inch wide planks that are about 2.2 pounds per square foot so about 300 pounds total vs the wood being 800 to 900 pounds. Cost for the aluminum planks would be about $1500 and a lot of labor to remove the old wood planks (but my wife had a idea about how to do that which involves using a hole saw to core out each screw then using a pipe wrench to remove the screw and core after the wood planks are gone).

 

[Pinnacle Campers]

Doesn't the camper have a floor? By the looks of the picture below you could just tear up the floor, put some strips on those I beams and put the camper back on?

View attachment 266500

I don't think your garage has a floor so you would need to do something there, motorcycles, snowmobiles, and gear is fairly light in comparison to what it was built for. Maybe consider nidacore type panels or fiberglass reinforced plywood with some aluminum "treads" and tie down rails.
I like the build and have been following. The multifunctional aspect appeals to me. That said modding the flat bed does remove some versatility of the truck/ bed itself. Maybe a heavier duty truck makes sense.

 

[Jfet]

Doesn't the camper have a floor? By the looks of the picture below you could just tear up the floor, put some strips on those I beams and put the camper back on?

I don't think your garage has a floor so you would need to do something there, motorcycles, snowmobiles, and gear is fairly light in comparison to what it was built for. Maybe consider nidacore type panels or fiberglass reinforced plywood with some aluminum "treads" and tie down rails.
I like the build and have been following. The multifunctional aspect appeals to me. That said modding the flat bed does remove some versatility of the truck/ bed itself. Maybe a heavier duty truck makes sense.

The garage also has a floor. It is made similar to the camper (2x1 steel tube spaced on 16 inch center with 2 inches of polyiso foam then 3/4" marine plywood screwed on top. Very strong. Both the camper and the garage pod easily support themselves on three jacks while staying level, meaning the floor does not flex much.

I think a bigger truck might be in our future but it would be nice to get the kinks out of everything with this truck. I sure could use that extra 500 pounds by doing the swap to aluminum. It would also take about 300 of those pounds off the front axle which would be a big help. I think we could go with nothing at all in the flatbed but that does make it a bit useless for when you are dropping the camper and garage and driving just the truck around. It would be worth it to me to replace the split, weathered oak or apitong? with $1400 of a aluminum.

Don't have to make a decision until we finish the garage pod. We don't set off on our journey till this summer.