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Walls - 1.5 or .75 ?

PostPosted: Thu May 18, 2006 12:22 pm
by Gerald_G
Hi everyone - my first new subject on the board.

I am planning a project starting as early as next week.

(It is not technically a teardrop, but I hope you guys don't mind me hanging around this board since I am planning light and simple, and you have a lot of great info here. I may build a TD too someday!)

I am planning on building (basically ground up) from an existing doner travel trailer. Since there is heavy wall rot etc, this will be from the frame up. I plan to narrow it, lighten it, and wedge the front for wind resistance. Like the squidget project almost, but to sleep 4.

What I am asking about is the difference between 1.5" walls and 3/4" walls.

I believe most travel trailers since the 70's have been basically 1.5 X 1.5 wall construction. I am wondering if anyone can post some pros and cons of choosing 3/4" framing, or 1.5" framing. Anything relating to this question would also be welcome information.

My theme is going to be K.I.S.S. Not the rock band, the "Keep it Simple" version. Every time I have to choose between simple and complicated, I hope to choose simple.

Thanks in advance - Gerald

PostPosted: Thu May 18, 2006 1:33 pm
by Joseph
My Scotty doesn't have framing - just 3/4" plywood sides and a Masonite roof covered with aluminum. These are so cheaply made it's a wonder so many survive, but there's still a lot of 'em around. Of course, I know of several that have been rebuilt from the frame up.

Joseph

PostPosted: Thu May 18, 2006 2:51 pm
by josephhanson
I built my trailer with the walls just thick enough to sandwich the insulation. I let the insulation thickness dictate my wall thickness. I found one inch insulation used 1/4" luan on the outside and inside and used 2x4's cut down to 1-1/2" X 1" for the studs in the walls. It turned out to be very sturdy. Might not be the "right" way, but it was "my" way

Joe Hanson

PostPosted: Thu May 18, 2006 3:08 pm
by Gerald_G
Thanks - not a bad idea to find my insulation first. Like you say, frame to match.

I had planned on only having rigid sheeting on the inside, and using regular aluminum RV siding on the outside. The siding stapled on would not add too much rigidity to the walls.

Since it's going to be just over 6' tall, I was thinking that 3/4" might make for bows in the walls in that one direction.

On the other hand I have plans for closets on either side which would lend rgidity in this direction as well...

PostPosted: Thu May 18, 2006 4:06 pm
by Gerald_G
Joseph wrote:My Scotty doesn't have framing - just 3/4" plywood sides and a Masonite roof covered with aluminum. These are so cheaply made it's a wonder so many survive, but there's still a lot of 'em around. Of course, I know of several that have been rebuilt from the frame up.

Joseph


I've read a couple of web-logs on Scotty rebuilds. Not sure that solid ply is the way to go for me. Weight is a factor too.

PostPosted: Fri May 19, 2006 7:23 am
by josephhanson
My trailer is just over 6' tall. I used the same method for the roof/curv that I used for the wall - 1/4" luan-insulation-1/4" luan. the ridged insulation curved around the radius and P/L glued inplace just fine. It is nice to have the insulation.

Joe

PostPosted: Sat May 20, 2006 12:35 am
by Artificer
If you want to go with the 3/4" wall framing, I would add a 1/8" layer of plywood to the outside, and make sure both skins were well glued to the insulation and framing. This stiffens up the wall considerably. I'd have to crunch some numbers, but I would think the 3/4" sandwich construction would/might be as stiff as the 1 1/2" without the outside skin. (or using fiberglass batt insulation)

You could split the difference, as Joe mentioned, and go with 1" foam/framing. This is what I did for my trailer walls.

If you have 1 1/2" framing/insulation, and add the 1/8" plywood to the outside, under the alluminum skin, you would have the strongest walls of the mentioned choices. If you take a look at this thread, you can see Captain Sam demonstrating the strength of the sandwich construction method.

Pro/Cons... Thicker is heavier, but not much. Thinner is less stiff, but can be compensated for with the sandwich construction method. Thicker is, uhm... thicker. Less interior space if you keep the same exterior dimensions.

Are you rebuilding the trailer, or just using the doner trailer for parts? The windows and doors will be probably be easier to use if you keep the wall thickness the same.

Insulation choice: I would go with extruded polystyrene insulation. Its the pink or blue stuff. People have mentioned that the white foil/fiberglass faced insulation may not be dimentionaly accurate. (or measure each sheet before you buy it, so you're not supprised)

Good luck, and welcome to the obsession.

PostPosted: Sun May 21, 2006 9:38 am
by Gerdo
My side walls are 3/4" solid plywood (no insulation) I did insulate the roog and floor. I have been in 20* weather and still warm.

PostPosted: Mon May 22, 2006 11:40 pm
by Gerald_G
Thanks for the replies everyone.

I am not really planning on "rebuilding" the trailer. I am building a new one, but getting a lot of parts fromt the doner.

I am also getting windows from a doner motor home, furnace, door and possibly windows from a truck camper doner. Since these are all likely 1.5" walls, the windows and doors etc. would likely fit best back into 1.5". Very good point.

re: rigidity of 3/4" I think it would still work since I was planning a small bulkhead at the 4' back point, and there are closets 1/2 way back that would work in the same way.

As I write this I lean towards 1.5" for the doner parts ease of fit, but will decide finally once I've inspected all the doner parts.

Thanks again for the input.