Insulated vs. solid walls

[Model_A Bill]

Hi Folks:

Are the walls heavier with solid wood as apposed to sandwiched insulated walls, or vise a versa? Or does it really matter?

Thanks
Bill

[Podunkfla]

3/4" plywood is quite a bit heavier than most insulated walls...
If you use 1/4" outside, simple 3/4" pine framing and 1/8" inside
like a lot of folks have... It prolly weighs a bit over half as much.
It may be more work, but I think insulating the walls is the way to go.
Just my .02 worth.

[Ira]

3/4" plywood is quite a bit heavier than most insulated walls...
If you use 1/4" outside, simple 3/4" pine framing and 1/8" inside
like a lot of folks have... It prolly weighs a bit over half as much.
It may be more work, but I think insulating the walls is the way to go.
Just my .02 worth.

Ditto.

And remember Bill that insulated walls give you a bit more flexibility on running wires to outlets, switches and appliances, and where you place them. Those who use go solid walls run electrical through the roof and come down with their wires.

[mikeschn]

A 3/4" 4x8 sheet of plywood weighs 75 pounds.

An insulated wall...

outside skin (aluminum) 18 #
pine sticks for framing 10#
inside skin (1/8 plywood) 12.5 #

so roughly 40 1/2 pounds

Now if you were to use 1/2" plywood for the sides, you'd be at roughly 50#.

Insulation is nice, but it is more work.

You decide.

Mike...

[Esteban]

Mike, exclusive of aluminum, wouldn't an insulated wall for an 8 ft. teardrop weigh about 47.5 lbs?

12.5 lbs. inside plywood (1/8")
10 lbs. pine boards
25 lbs. outside plywood (1/4")
? lbs. insulation (some plywood will be cut off so figure it's a wash)
47.5 lbs. total for one side wall

Insulation can make a teardrop lighter, provide protection from outside heat, cold, and noise, so you sleep better. It seems worth a little more work, to me. In the end it's your decision to make for your needs.

[mikeschn]

Sounds right to me.

Mike...

[Keith B]

10' long, 4' tall, 3/8" ply exterior; 1/2" framing, 1/2" insulation, 1/8" interior.... 50#s (per bathroom scale); total wall thickness was 1-1/16"

[dhazard]

I did my walls with a slightly different technique. This was done with a ¾” sheet that I cut out the parts that were not required for the structure. It is 1/8” oak ply, ¾” ply, 1/8” ply. Making it into a 1” wall that is about the same weight as a ½” wall.

[Model_A Bill]

I don't mind the extra work. Sound by your inputs that I'll get a better wall, more flexability with wiring, and lighter.

Seems to me the benefits far outweigh the extra work.

Thank you for your input

[kennyrayandersen]

I'm new and haven't posted much becasue I'm just learning, but I am an aerospace engineer who's specialty is structural analysis. Couple of questions and then some comments:

The 4X8 sheet I called about weighed 12# -- are all y'all using something really light weight and if so, where you getting it?

If someone comes across a 1/16 or 1/32 inch thick source of 'cheap' plywood do share -- I can get it through aerospace suppliers, but it is quite expensive, and generally not in a 4X8 sheet dimension (plus it's difficult to ship as the size is awkard.

Why?

Because I plan on using a composite sandwich layup of either very thin plywood (not 1/8", because it is too heavy) with a ridgid foam core. The facesheets and core will be joinded wet layup using epoxy (becasue it won't melt the Home Depot foam core). Because I can't find a cheap source for the extra-thin plywood, I had consigned myself to making the interior and exterior sheets out of fiberglass (maybe 2 inside, 2 outside, with a bit heavier in the floor -- monocoque like).

Panel built like that will be much more rigid an strong compard to solid wall construction and will also provide insulative properties that are desireable (I think). I'll make a more detailed description of what I have in mind as soon as I get a few more details worked out, but I'm shooting for an extraordinarly lightweight trailer.

[Miriam C.]

Kenny, is the weight between 2 sheets of 1/8 and 1/16 that significant? Also How will that relate to a heavier window? (still have to do my door)

I framed with 3/8 baltic Birch. The side was not very heavy even with two sheets and the framing. I kerfed my framing so it isn't very heavy, Once the window and doors were cut it weighed even less.

Plywood weights
http://www.hoganhardwoods.com/hogan/pag ... eights.htm

wood weights. (per 1000 board foot)

http://www.hoganhardwoods.com/hogan/pag ... eights.htm

[Esteban]

If money was not a concern, not like that's ever gonna happen, I'd build with Okoume plywood. It's light weight marine grade plywood available in sizes up to 4'x10' and 5'x10'. Boulter Plywood's website http://www.boulterplywood.com/MarinePlywood_4.htm indicates a 4'x8' sheet of 1/2" plywood weighs 37 lbs. With 10' long sheets you could build a 5'x10' teardrop without seaming the sides or floor together from smaller 4'x8' sheets. It comes as thin as 1/16". Sure wish it didn't cost so much.

[Ira]

I'm new and haven't posted much becasue I'm just learning, but I am an aerospace engineer .

You're going to have a blast planning and building your TD, but I'm gonna repeat something many have often said here before:

You're NOT building the Space Shuttle here.

For a tear, a 3/8" ply wall, 1" framing, insulation, and 1/8" cabin skin/wall is PLENTY. Hell, mine survived a DIRECT hit from Hurricane Wilma without a scratch.

What possible worse event could occur to test a TD's structural integrity?

And let's not forget the most important point to my story here:

I'm a total spastic when it comes to building, and the thing still held up like a ROCK.

We repeat the expression "overbuild" here a LOT, and we do it for a reason.

[john]

What Ira said: Wayyy lighter and makes a good place to hide the wire.


After running the A/C on a muggy night I can see the outline of the 3/4" ply as condensation on the aluminum skin the next morning. There is no condensation where the insulation is. i need to get a pic of that.


What dhazard said:





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[kennyrayandersen]

Thanks for the welcome. Don't mistake my title to mean I aim to build a brick outhouse -- quite the opposite. After looking at most of the designs I believe that they are generally overbuilt.

To contribute to this particular thread, structurally, it doesn’t matter whether the walls are solid or hollow, but rather how each is executed that matters. I prefer the insulated because I want to be able to use my lil’ tear all 4 seasons. I shant hijack the tread, but will post my general idea here:

http://tnttt.com/viewto ... 915#207915