Insulated or not?

[Woody]

If I Read your question correctly. You can cut out the 3/4" plywood, like you mention, and in the voids install the 3/4" insulation and then apply the exterior skin it and that will strengthen it some. It will take some engineering on the layout. As for as flexing once the wiring is done, if any, the installation of the interior skin it should stiffen it up somemore. Sandwich style construction has it's merits. It would be better for sidewall rigidity is to make the door openings bigger than you need and frame in with some hardwood material to prevent the warpage, plus for door hinge installation and plywood endgrain issues, the scourge of the teardrop builder. Do the same with the perimeter of your door assembly, since doors love to warp by themselves naturally. I watched mine take on a life of it's own warping while cutting the door out. When I built my walls, I had considered the warping that unbacked plywood does. I used 1/2" ply and backed it up with pine 2" x 2" which gave me a cavity of 1 1/2" for insulation and wiring etc. It became super rigid, which helped with the door framing, hinge installation and stiffening the door itself. Granted it does make for a thick door in my case. There many ways to do what you want and I am sure other will chime in here info pertaining to thier builds. Have fun with it. The main thing to consider is have all of your materials prior to starting, like windows, roof vents, galley hatch hinge, etc. and other major hardware available when building. It is a real drag to find things to fit or have to retrofit after the fact, it is easier to build having them around at the beginning

[IraRat]

Just my 2 cents, having never built a tear. Please consider the source.

Both methods appear to have been used and work, so that’s not really an issue…

Cost- a sheet of ¾ ply is about $22 around here, enough hardwood to
frame a side maybe twice that (? or more).

Time- I can cut holes a lot faster than cut and fit for a stick frame.
Those “skilled in the art” may be able to frame as fast. Lindsey
says an hour for the holes, that’s about 3 sticks for me.

Strength- Depends on the structure but with the ply you can beef up the
areas you are concerned about. Also much easier to do a 2D
web with the ply and no joints.

Weight- Either can be over or under done. In our world stick is probably
lighter. Well Engineered, the ply probably is (more design
freedom) but I am guessing here. I’d call it a wash or give the
edge to stick and bow to an ME with data.

Hinges- Wouldn’t use edge mounted hinges directly in ply myself, but
epoxy on the end grain would help a lot. Would be easy to let in
a piece of hardwood for the door hinges: T&G and covered both
sides with sheathing would be as strong as stick. A hinge that
through mounts should be fine, again, I’ll bow to those
experienced. Ply tends to warp less.

Wiring- A ½” hole in ¾ material will not help either; I really don’t see
an advantage either way.

As far as cost, you don't need a lot of pine sticks at all to frame the walls. It's just a matter of whether you REALLY don't want to spend like $30, $35 on this straight lumber for the framing, and would rather use a piece of plywood that you already have to accomplish this function.

With all of the cutting you would need to do on the ply, I would go for the 35 bucks.

[Salivanto]

IraRat quoted me and replied:
> > if I can frame with pine, can I use pine
> > plywood -- or should at least one of these
> > be hardwood/poplar/birch?
>
> You can PROBABLY cut plywood into strips for
> his, but I don't know if I would want to.

Sorry. I phrased this poorly. Let me try again.

If the frame boards can be pine can the plywood siding be pine too, or should at least one of these (either the siding or the framing) be hardwood/poplar/birch?

I have no desire to use plywood as framing and never meant to say that I did.

[asianflava]

Hmmm still confused
Maybe this could clear things up?
You can build it any way you want, that is what makes these thing interesting. You don't HAVE to use any hardwoods at all. Although, places that are highly stressed like hinge points, it is reccommended. The hardwood will hold the screws better, softer woods would tend to pull thru. Your door would fall off eventually.

[IraRat]

Got you, Sal.

You don't need any expensive hardwoods. Some people opt for hardwood SPARS, but that's up to you.

[GregJ]

Salivanto,

If I understand your question, IraRat and asianflava are correct. Also note, the hardwood in the plywool is only a very thin layer and mostly for looks.

[Salivanto]

Salivanto,

If I understand your question, IraRat and asianflava are correct. Also note, the hardwood in the plywool is only a very thin layer and mostly for looks.

Gotcha. It was the "mostly for looks" part that I didn't understand. I wanted to make a woody, but lately I've been thinking that based on my budget and ambition level, latex paint is the way to go.

So, here are my thoughts on wall building at this point:
- Use thin plywood. Probably 3/8" outside and 1/8" decorative on the inside - although I haven't ruled out using two 1/4" boards.
- build a 3/4" thick frame out of the pine boards I have (2x4 and 2x8 - to be ripped to the right size.)
- if I have to buy any more framing boards, I'll use poplar -- perhaps also for the areas around the door hinges, as suggested.
- insulate the walls.

This could all change before I start building. I haven't visited the specialty wood shop or asked the neighbor if he'd be willing to part with any of his wood. (He's got loads of underutilized long boards, 3/4" plywood and even some red oak which could become ant food -- can you frame with red oak?)

Thanks for all the feedback.

[Salivanto]

Salivanto,

If I understand your question, IraRat and asianflava are correct. Also note, the hardwood in the plywool is only a very thin layer and mostly for looks.

Gotcha. It was the "mostly for looks" part that I didn't understand. I wanted to make a woody, but lately I've been thinking that based on my budget and ambition level, latex paint is the way to go.

So, here are my thoughts on wall building at this point:
- Use thin plywood. Probably 3/8" outside and 1/8" decorative on the inside - although I haven't ruled out using two 1/4" boards.
- build a 3/4" thick frame out of the pine boards I have (2x4 and 2x8 - to be ripped to the right size.)
- if I have to buy any more framing boards, I'll use poplar -- perhaps also for the areas around the door hinges, as suggested.
- insulate the walls.

This could all change before I start building. I haven't visited the specialty wood shop or asked the neighbor if he'd be willing to part with any of his wood. (He's got loads of underutilized long boards, 3/4" plywood and even some red oak which could become ant food -- can you frame with red oak?)

Thanks for all the feedback.

[toypusher]

you might want to save the red oad for the cabinets. I think that red oak is very attrative wood and have made lots of things out of it. I would not use it in framing except for maybe the hinge side of the door and maybe a spars for the hinge area of the galley hatch. It is heavier than pine or poplar and would not give you any real extra strength in the sandwich wall construction. Pine and polyurethene glue will make a plenty strong side wall construction.

Kerry

[IraRat]

You're gonna rip any lumber you already have to 3/4 thick, right? (You can probably improvise on the width.) 3/4 is the thickness of the insulation tyou want to stick in there.

Also, have you seen any "standard" plans for framing on a 3/8 side wall? For my Cubby, it's NOT that elaborate or complicated. Plus, the ONLY curved portions that you have to cut and use plywood for is around the door, and if you have other lumber that's a couple of inches wide, you can use THAT instead. There's NO framing at the top, curved portions.

I'm doing 3/8 walls, 1/8 interior and exterior skins--period. (I may use a gold alloy aluminum sheet for the roof, but the jury is still out.)

Finally, you say you may paint the outside. Remember--now that you're putting on those exterior skins, you have a LOT of design options for staining and such.

[Dave Nathanson]

Anybody here every been too cold in an uninsulated tear? How about one with an insulated roof but uninsulated walls?

Yeah, I sure have. My TD has 1" solid plywood walls, and 1/4" roof (+-) plus 0.050 aluminum skin. Plus a 1/8" oak in the inside. But no insulation.

I got talked out of insulation because of all that thick wood. Wrong! It's chilly in there at night! Within 3-5 degrees of the outside temp. How about that? We camp a lot, usually in the So Calif deserts, where it's often warm in the day, and low 40's at night. What temperture are you comfortable sleeping in? Even if you camp in the desert in summer, insulation will help keep it cooler inside for those afternoon naps.

What I have learned is that an uninsulated Teardrop is a cold TearDrop. So I stapled up some fiberglass house insulation across the inside roof to see if it helped. I covered that with some wood grain adhesive shelf paper to keep the fiberglass away from us, and try & make it look a little better.

It's still not Toasty in there at night, but it's a heck of a lot better than it was. We have been taking the really thick feather comforter with us, and it helps a lot too. So does *carefully* burning 3 small candles. So this is insulated roof only, and that just the roof that you can see while inside the cabin. I plan to do better.

But the front wall does get kinda wet overnight due to condensation. Just like the single pane windows do.

I have now ordered some 1/4" thick R14 Film/Foam/Film insulation which I will be retrofitting. Retrofitting is a lot more difficult then just doing it right in the first place. But I have come to the conclusion that insulation is imperative. I bought PRODEX High R (FfmF) Foil-Foam-Foil Insulation from
http://www.insulation4less.com/highr_FfmF.asp

I have an "open beam' construction, & I like the look of it. So the thin insulation is going to work out better for me. Plus, according to the i4L website ordinary fiberglass batting style insulation looses 36% of it's powers with a 1 -1.5% humidity change in the batting. This film stuff is also watertight. Anyway, it sounds really good, and I'll let you guys know how it goes after I've installed it & had a chance to test it out in various conditions.

[Chris C]

Dave,

I haven't built my tear yet..................but when I bought my Dodge van (18 1/2 foot delivery van) and turned it into a camper, I glued 4 layers of that insulation on the inside walls and ceiling before putting up 3/8" plywood walls, ceiling, and carpet. I have used this "camper" in seriously adverse conditions and can attest to the insulating qualities of the material. Also, the reflective surface of the insulation repels the heat amazingly. My van is dark maroon and even in the Summer sun the vehicle remains almost uncomfortably cool with the A/C running. In the winter, the heater more than adequately heats the entire vehicle. It is extremely flexible. I plan to use it when I insulate my tear. I can't think of a more satisfactory material. I give it a BIG....