Weight Reducing Framing

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Billiam
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Location: Waveland, MS

Weight Reducing Framing

Post by Billiam » Mon Jan 30, 2017 4:13 pm

Was an RVIA Certified Tech for more years than I care to reveal & have since retired.
As cabinetmaking has been a lifelong hobby, I have an idea for framing a camper in a lighter fashion I wan to run by...
By using 1X2's (rather than the standard 2x2's) & making each joint a half-lap, each joint glued & doweled for strength, gluing the entire inside wall structure to the framework, and using Luan & Filon for the outside walls; the intent is to replicate the monocoque construction of the aircraft industry (my 1st career....)
The corners would of course be strengthened using 2X2'2 & a 1X2 laminated to it for jacks (using power Happijacs) & the walls insulated with foil-backed foam.
My query is as to weight savings; I'll be darned if I can locate any sort of chart for lumber weight, I suppose because of the moisture factor involved making an exact calculation difficult. So has anyone else out there tried this concept? I've called a couple of Factory Engineers, but no one has apparently experimented, most likely because of the labor-intensive requirements. But I'm retired & time is NOT of the essence!!!!
Award is about the closest in concept - they're the only ones I know of that radically differ in construction techniques & they were no help - weren't even interested in communicating.
Just thought I'd toss the idea out there....!!!

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Bill Edmundson
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Re: Weight Reducing Framing

Post by Bill Edmundson » Mon Jan 30, 2017 5:02 pm

Biliam

Welcome.

I've been playing with the idea of a trailer for a while. My thought is framing with 1 x 2's laying flat (3/4 x 1 1/2) with an interior skin of a light paneling glued to a 3/4" foam core. Then glued to a light aluminum exterior panel, making a stress skin panel. I had a pick-up truck shell made that way by Winnebago. Super strong!

Is that what you're talking about?

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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Billiam
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Re: Weight Reducing Framing

Post by Billiam » Mon Jan 30, 2017 10:33 pm

In a way. The issue with the aluminum skin glued directly is thermal transfer & moisture issues. The metal doesn't expand & contract at the same rate as the wood & tends to delaminate over time - that time varying by temperature variations where you live. And if moisture EVER gets inside the laminations it eats away at the skin quickly. Winnebago dropped the idea over the years & went a slightly different route.
Modern Filon-style panels (as opposed to what we call "stick & tin") use either a pressure-bonded or vacuum-bonded wall assembly of Filon bonded to Luan with a framing & foam core center then bonded to an interior Luan wall panel. The process is a bit tricky for DIY, but can be closely replicated with some work. A bit labor intensive, but my time is free, LOL.
I want to lay the 1 X 2's out using the 1 1/2" as wall thickness to add extra insulation thickness with each of the horizontal & vertical framework pieces being a single piece through the entire length used with no joints other than the half-laps (if that makes sense). No nails, screws or hardware, just added dowels for rigidity. The inside & outside Luan panels would then be glued to the framework & the Filon glued to the outer walls (THAT'S the fun part!!!). The option there is eliminating the outer Luan & Filon & use RV Aluminum stapled in the traditional stick & tin style. Lighter weight true, but somewhat less structurally stiff due to the loss of the outside Luan structure.
This may not be as much of an issue for a trailer, as there is the steel (or aluminum) frame which a truck camper does not have. Part of this issue MAY be addressed by building a double-floor for the camper (something I would do at any rate for the insulative qualities that provides).
Pretty long winded reply, I now realize, to a relatively simple question - forgive me. It's my stupid Engineering background that causes me to often overstate things (and I HATE Engineers LOL)!!!

JimmY
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Re: Weight Reducing Framing

Post by JimmY » Tue Jan 31, 2017 3:54 am

Boat building with plywood has a table on wood "densities", so the information must be out there somewhere.
-Jim
Nothing says poor craftsmanship like wrinkles in your duct tape!

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Bill Edmundson
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Re: Weight Reducing Framing

Post by Bill Edmundson » Tue Jan 31, 2017 8:18 am

Billiam

Don't hate me. I'm a retired Civil/Structural Engineer. I worked on and designed power plants. When weight was an issue, we usually wanted more because of equipment vibration.

Thanks for the info.
Filon looks better for several reasons. It would be easier to handle, comes in sizes that would eliminate many seams, and is cheaper.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

Billiam
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Re: Weight Reducing Framing

Post by Billiam » Tue Jan 31, 2017 12:13 pm

LOL!! No real hate here -
My Degree is in Aerospace Electronics, so......
Worked at Boeing & Lockheed both & realized I hate electronics, so got out of it & into RV's, having grown up with them.
The Filon needs a backing (adding weight), so my framing idea is to reduce/offset that weight. That & building hollow-core cabinet doors rather than solid & minimizing add-ons. Just the 2 of us, so no extra bunks, eliminating the dinette cabinetry to go with 2 reclining chairs & a pedestal table, etc.
(Just got a working 8' Norcold reefer for $100, so that's a start on the project!!!)

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Mr Hot Rod
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Re: Weight Reducing Framing

Post by Mr Hot Rod » Tue Jan 31, 2017 6:34 pm

For lumber weights, see Chapter 5, Boat Building Lumber, Softwoods from Boatbuilding with Plywood by Glen-L Witt.

Richard in Tasmania used a similar build method :
We're in the process of replacing the aluminum skin on our Palomino pop-up truck camper with a fiberglass skin to eliminate the leak-prone joint caps and caulking. Epoxy fairing compound is applied to the wood/foam panel, faired to get it smooth and then laminated with 10 oz. fiberglass cloth. We're using high-build primers and an inline air sander which makes short work of finishing fiberglass panels.

More info here :

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Billiam
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Re: Weight Reducing Framing

Post by Billiam » Tue Jan 31, 2017 7:42 pm

I'm going to stick with the Filon (Fiberglass/Nylon blend) rather than straight Fiberglass panels primarily because they are already surface-sealed. The material comes with a removable plastic "covering" & has a slight "fiberglass mat" finish. I don't like the delamination issue that RV's regularly suffer, but I know by properly addressing the problem I can beat that.
Lots of folks (including Mfgr's) use Silicone for sealant, and it's a poor product for Filon because it simply WILL NOT adhere. (You can lift one end of a beaded seam & peel the silicone off in one long piece!!). technology has produced far better products - ProFlex Brand, for one. WAY, WAY better - adheres well & has fantastic flexibility characteristics.
The other issue is discoloration of Filon - don't yet know whether to just accept it, or go with a Gelcoat finish. Maybe just go hog-wild & paint the entire thing!!!!
More or less just going to stick to Southern Pine (here in Mississippi it's easy to get!) and depend on the Monocoque-style construction for the strength factor. That & dowelled lap joints + GOOD wood glue should do the trick. (The wife says I'm overthinking the whole thing & that there's medication for people like me.....but she's been saying the same thing for 35-some years, so.....)

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Bill Edmundson
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Re: Weight Reducing Framing

Post by Bill Edmundson » Wed Feb 01, 2017 2:36 pm

Billiam

What does stick to Filon? Do you know if 3M5200 will stick? I know 5200 will stick to everything you don't want it to stick to!

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

Billiam
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Re: Weight Reducing Framing

Post by Billiam » Wed Feb 01, 2017 5:47 pm

ProFlex from a Company called Geocel sticks well & is very flexible.

https://www.geocelusa.com/

Lots of glues will adhere to the reverse side to bond it to the Luan backing, but the face has a coating that makes it a bit more "slippery".
Bonding to Luan backing, I've used 3M 1300L & 3M 30NF (both sprayed) - think I myself prefer the 30NF for the "color change" when dry & ready for contact.

GSD
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Re: Weight Reducing Framing

Post by GSD » Mon Feb 13, 2017 1:38 pm

http://learnframing.com/calculate-weigh ... ted-green/

here is link that will give you lumber weights

I am also looking at trailer weight reduction

1st I am using Aluminum channel for the frame

Filon sheeting can bought by the roll in several lengths @ 108" wide to reduce seams

Ralph

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