Side Wall Construction

[SteveH]

Shil,

Thanks, and may I ask, has the 3/4" wood side been a problem in any way?

I know there is better insulation, however that is the way they were built in the beginning. Just wanting to know if there is any serious problem with going that way.

[asianflava]

Out of curiosity, does anyone know what a sheet of 3/4 ply weighs? I wonder how much weight I actually did save.

[Arne]

I did a search, came up with 75# for 4 x 8 x 3/4...

Search was 'plywood weight 4 x 8'

[mikeschn]

I touched on the weight of plywood here...

http://tnttt.com/viewto ... =5369#5369

Mike...

[asianflava]

Figuring an equivalent piece of 3/4 ply: 108X60X.75X.0217=105.462

So, I saved almost 35lbs on the floor alone. Cool, that makes me think that the extra work was worth it.

[Cary Winch]

OK, I guess I can share some of our discoveries and design on this subject. We have done the 1/2" wall and now only do 3/4" walls on our tears. the main reason is because of the cutout doors. It is impossible to keep a 1/2" plywood door straight without adding a bunch of reinforcement. 3/4" plywood solves this problem and also helps keep the whole body stiffer and straighter. If you are using a manufactured door then is not so much a concern.

1/2" plywood is more than adequate for the floor. Any more than that is unneccesary weight unless you are building a walk in teardrop. This is common question we get asked, we answer by asking how heavy are the bed boards under your bed. Remember that is all your floor is in a teardrop, a bed. Stiffness and rigidity is not an issue with the floor if you have a stiff box structure for a body.

A composite wall (plywood paneling/foam core/al skin) is going to be your lightest wall. If you are building a wall 1" or thinner you will not see a significant enough difference in R value over 3/4" plywood to justify it unless you go to a 1 1/2" foam like Arne suggested. The other factor to consider with the foam core is air infiltration issues. All edges of the foam must be spray foamed or caulked tight or you will not get the R value you are anticipating. We use foam board to insulate our roofs and then use low pressure foam to seal the edges and remove any possible air pockets. Any air pockets will promote condensation build up in a teardrop roof and cause water to seep out. This happens when fiberglass insulation is used in a teardrop roof unless it has a ventilation system like a house. Remember that alot of your home construction rules do apply here too.

With a composite wall you will incure some extra weight gaining structure back into the unit to keep it strong. This might be in the form of a heavier frame under the teardrop rather than having a stronger "unibody" type construction that you can get with a 3/4" plywood wall construction and a lightweight frame. This being said you might find that there is a false savings.

Here is one that should stir up some controversy. Never, ever insulate your floor. Unless you get out all possible air infiltration areas and air pockets you will have condensation form in the floor cavity. This is the most likely place in the unit. This will cause rot in short order no matter how well you think you have it sealed. This also goes for belly pans and some gravel guards people try to do. From a warmth point of view all teardrops have an insulated floor called a mattress. We use 3" thick foam mattress and that is good insulation that is in the cabin safe and dry.

I hope I don't offend any one on some of these but perhaps it is just better to share.

Cary

[BrianB]

That may be the most informative post I've seen on here. Some numbers for comparison of solid vs composite walls:

A single piece of 3/4" plywood has an r-value of 0.94. A composite wall with 3/4" rigid foam insulation and 1/4" plywood skins would have an R value of 4.6 with a weight savings of about 20%.

[BufordT]

How could you offend any one Cary. U be the man you build CAMPINN teardrop trailers. That's the trailer we are all trying to build. The more you post the better we learn and like it.

Thanks for the info.

Bufordt

[SteveH]

Cary,

VERY informative post. I appreciate the information and I'm shure others do as well.

[Chip]

Cary,,thanks for the information and input,,Its uncommon to find a manufacturer or builder that is willing to share a few of his trade tips,,,eduction in anything is expensive wheather its in the classroom or the practical appliction of a product,,It shows a lot of class on CampInn to share this education with us hackers,,

thanks

chip Hughey

[lee]

Cary, Thank you so much for the good information. Will carry back the fiberglass insulation and get more of the foam board. My husband kept saying we needed some kind of ventilation for the roof. But, how could you get it with the small space. He thought of doing it with foam like they put in boats.
When we finish with ours, maybe we can blow up a picture of one of your trailers and wrap ours with it so ours will be pretty like yours. Lee

[Cary Winch]

Lee,

That is a good move going with the foam board. As Brian noted the R value of 3/4" of foam is notably higher than you would get with fiberglass in the same space. I always did wonder if there would be a good way to create a vented roof system on a tear. Short of a power vent of some sort the only thing that makes sense is fill it solid with foam. And it works very well you will find. We have even done considerable experimentation with two part spray foams. The R value is great with that stuff and it seals so well. But, alas we just haven't been able to make it work yet. Any ideas out there on that subject?

And thank you very much to all that gave so much great feedback. I am happy if any one person can get something usefull from it.

Oh by the way AsianFlava, in hind sight my floor insulation point wasn't meant towards you. I don't consider what you are doing as an insulated floor as much as it is a lightweight composite floor. If all voids are filled and it is well sealed I think you will have something really cool there. From your pictures, it looks like you do in general.


Thanks for finding the R values on the plywood vs foam and 1/4" ply Brian. I was going to try to dig those out tonight, you beat me to it. All I could remember was the 3/4" was about R 1 .


Cary

[BrianB]

I pulled those R values from here:
http://coloradoenergy.org/procorner/stuff/r-values.htm

Handy if you ever need to know the r-value of a brick.

[shil]

Shil,

Thanks, and may I ask, has the 3/4" wood side been a problem in any way?

I know there is better insulation, however that is the way they were built in the beginning. Just wanting to know if there is any serious problem with going that way.

No problem so far. I'm not at all worried about insulation, the tear's replacing a tent, and it's a lot warmer. By the time it gets put away the days are too short for outdoor life. It's not the cold, it's the darkness that kills the season.

[SteveH]

Thanks Shil. I've just about decided to go with 3/4" walls for all the obvious reasons. I'm not really concerned about the insulation as far as cold is concerned down here in South Texas, it's the heat that concerns me. I do plan on insulating the roof because of the heat and sun, and I'm leaning toward white painted aluminum for the same reasons. As far as the weight is concerned, if it comes out anywhere under 1500 pounds, I won't even know it's behind my full size V8 powered Dodge pickup. Let's hear it for American muscle....well, let's see, I think Mercedes ownes Chrysler now, so maybe it should be German muscle.