How Thin is Too Thin?

[NonProfit]

Hey, I'm a n00b here. Got the bug to build a TD and am hoping to build one someday soon. So my first question; how thin is too thin? Many builders say their first build was overbuilt and way too heavy. I want to avoid that mistake.

It seems there are two popular methods of construction. The heavy builds utilize a wooden frame and the lighter one sandwiches a sheet of .75" ply, removing sections to reduce weight.

My idea is to recreate a woodie look with an exposed frame of structural hardwood (1"x2" birch?) layered over a sheets of .25" marine grade plywood, Celotex and beadboard paneling.

As I see it, the structure only needs to hold together going down the road. Assuming the birch exoskeleton is constructed properly, (with some interior cabinets added for good measure) it seems like I should have no problems. However, all of you who know way more that I do don't build them this way. Why not?

[Shadow Catcher]

Its an aircraft not a tank, you got it right

[len19070]

Built this one with 3/8" Plywood and 3/4" Cedar.



And this one with 1/4" Plywood.



Happy Trails

Len

[NonProfit]

Thanks Shadow Catcher and Len!

That green woodie looks real nice!

[synaps3]

The standie I'm building is light enough to not need a jack in the front, mostly of which I attribute to the wall structure. Even though the camper is a bit over 14' long and 7' tall, each wall weighs around 50 pounds. I can even lift the trailer on one side, from the wheel well when empty. Building a frame doesn't necessarily mean it's heavy.

My construction was pine 1x3s and 1x4s sandwiched between luaun plywood. Here's the process: viewtopic.php?p=655177#p655177

With building a thin frame like that, you NEED a Kreg jig. I use it for everything, the pockethole screws you'll use with it hold amazingly well. If you wanted to go thinner, you could omit the insulation and one layer of plywood. But then the camper would only be good in really temperate weather.

If you are planning on building a larger camper like I am, make sure you're planning on putting some weight in it from cargo, cabinets, etc. Completely unloaded and without the interior, my camper was like having a sail behind me. It got blown all over the place. Weighing down the camper with all our camping gear and luggage made the ride much safer.

[angib]

My construction was pine 1x3s and 1x4s sandwiched between luaun plywood. Here's the process: viewtopic.php?p=655177#p655177

With building a thin frame like that, you NEED a Kreg jig. I use it for everything, the pockethole screws you'll use with it hold amazingly well. If you wanted to go thinner, you could omit the insulation and one layer of plywood. But then the camper would only be good in really temperate weather.

Why build so heavy? 1x3s and 1x4s are much more than is needed - you only need 1x1s to connect the two skins together, though I can see the 1x4s make it easier if heavier round the edges.

Before everyone goes pocket-screw crazy, there really isn't any need to connect the various bits of framing to each other in a sandwich wall - all the framing does is to connect (and space) the two skins to each other. Good butt joints with some glue in them is plenty enough connection between framing.

It's worth repeating once again - these are not little framed houses, where the frame can hold itself up - they are stressed-skin monocoques where the framing just holds the skins together and stops them buckling.

[Larry C]

My construction was pine 1x3s and 1x4s sandwiched between luaun plywood. Here's the process: viewtopic.php?p=655177#p655177

With building a thin frame like that, you NEED a Kreg jig. I use it for everything, the pockethole screws you'll use with it hold amazingly well. If you wanted to go thinner, you could omit the insulation and one layer of plywood. But then the camper would only be good in really temperate weather.

Why build so heavy? 1x3s and 1x4s are much more than is needed - you only need 1x1s to connect the two skins together, though I can see the 1x4s make it easier if heavier round the edges.

Before everyone goes pocket-screw crazy, there really isn't any need to connect the various bits of framing to each other in a sandwich wall - all the framing does is to connect (and space) the two skins to each other. Good butt joints with some glue in them is plenty enough connection between framing.

It's worth repeating once again - these are not little framed houses, where the frame can hold itself up - they are stressed-skin monocoques where the framing just holds the skins together and stops them buckling.

Andrew...
Thank you for making so much sense!! With gasoline expected to go north of $5 gal this summer on this side of the pond, why would anybody not consider building as light as possible? I have wondered about the pocket screw thing myself. They are probably a handy for cabinet framing, but as you point out, not necessary for sandwich framing. I just came up with a name for my build... "Less is More"

Larry C

[Mini Renegade]

I used 9mm (3/8") ply on my trailer with no framing, other than the interior cupboards and around the door and window apertures and hatch opening. It`s solid as a rock and as light as possible.

[mckenney56]

My construction was pine 1x3s and 1x4s sandwiched between luaun plywood. Here's the process: viewtopic.php?p=655177#p655177

With building a thin frame like that, you NEED a Kreg jig. I use it for everything, the pockethole screws you'll use with it hold amazingly well. If you wanted to go thinner, you could omit the insulation and one layer of plywood. But then the camper would only be good in really temperate weather.

Why build so heavy? 1x3s and 1x4s are much more than is needed - you only need 1x1s to connect the two skins together, though I can see the 1x4s make it easier if heavier round the edges.

Before everyone goes pocket-screw crazy, there really isn't any need to connect the various bits of framing to each other in a sandwich wall - all the framing does is to connect (and space) the two skins to each other. Good butt joints with some glue in them is plenty enough connection between framing.

It's worth repeating once again - these are not little framed houses, where the frame can hold itself up - they are stressed-skin monocoques where the framing just holds the skins together and stops them buckling.

I've been trying to find any way to reduce the weight and the screws themselves are something I thought about cutting down on, and in some cases eliminating altogether. I've seen a few builders here that used screws to hold the ply in place while the glue dried and then removed them.

I add a question here. If you took all the screws out and weighted them, what do you guys think they would weight?

[jstrubberg]

Still drawing mine out, and likely to be doing that for another few months (make mistakes on paper, it's cheaper!). One of the thing I plan to do to keep weight down is to stick build the frame using sitka spruce 1x2 stock. It was widely used for small planes, is very light and extremely strong. The plan at the moment is a sparse 1x2 frame with a sandwich of 1" foam and 1/4 luan inside and out. Cabinetry (except for the doors) will also be sitka spruce. My goal is a queen bed sized 800lb trailer. With camping load, that should keep me under 1200lbs.

I can see that the cutout plywood method is easy, but it still looks to carry a lot of extra weight to me. Plywood is heavy.

[DriverOne]

If you took all the screws out and weighted them, what do you guys think they would weight?

I'd be willing to say as much as five pounds, depending on how many you use. I'm basing this on the bulk box of fine drywall screws I've got in my hand.

[mckenney56]

If you took all the screws out and weighted them, what do you guys think they would weight?

I'd be willing to say as much as five pounds, depending on how many you use. I'm basing this on the bulk box of fine drywall screws I've got in my hand.

I guess I can leave a few of the screws in.

[DriverOne]

What about barbed staples? Is there such a thing? I'd assume they'd be light.

[rowerwet]

my TD is totally held together with PLpremium construction adhesive, screws were used to hold until the glue dried, then removed and the holes filled with adhesive, there are about 10 coated deck screws going through the bottom of the deck into the lower sill of the wall, but they are really overkill as the adhesive would remove the top layer of wood if it ever came loose. other than that I only used screws to hold on hinges. I build boats and see fasteners as weak spots and water entry points.
my walls are 1/4 ply, 1x2 frame, foam board in the voids, 1/4 ply sandwiches, nice and light and really keep the noise down. floor and galley counter are 3/8 marine mahogany ply, and my hatch is marine mahogany ribs skinned with only FRP. Still haven't gotten it weighed but pushing it around and lifting it is wicked easy. I plan on replacing the Tractor supply trailer it was built on with a light weight chassis with a torsion axle, to make it even lighter and a little lower.

[Miriam C.]

1/8th inch on top of 1" x 2" spars and it went through the deck. We had to cut it with a chain saw because they couldn't knock it down. The sides are 3/8" Baltic birch, 1x2 frames, 1" foam and 1/8" inside. These things are tough!