Wall construction?

Anything to do with mechanical, construction etc

Postby Miriam C. » Thu Jun 29, 2006 7:21 pm

Bruce and gang
here are my weights. Perhaps it will help.
4 @ 5'x5'x1/4" = 84lbs.
4 @ 5x5'x1/8" = 44lbs
Total without framing = 128lbs

2 @ 5x10'x3/4 = 258 lbs.
The difference is in the framing. Cost is slightly more for sandwich.
(sorry for the edit! Calculator quit too. Thinking required :oops: )

You can go to Boulter Lumber and they have weights. Call local for pricing.
http://www.boulterplywood.com/

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Postby kayakrguy » Thu Jun 29, 2006 7:43 pm

Folks,

Again, a great discussion, just the kind of input someone like me needs!
I am going to 'parse' madjack's point. Since a 4 x8 piece of 3/4 ply weighs @ 75lbs. and a 1/4 inch 4 x 8 weighs 25 pounds and I need TWO of those in sandwich walls the net savings is @ 25 lbs/wall or 50 lbs for the trailer.

For purposes of discussion, I am willing to accept the 50#'s of extra weight in the walls for my build. I accept the fact that there are greater weight savings to be had in using 1/8 inch plywood--eg. Paul's note--I will return to that point later if need be.

Lets move on to condensation/moisture. Madjack says that in his experience there is no significant advantage to sandwich construction in regard to heat/condensation. In other words, take some hot human bodies giving off moisture and heat in a T with the temperature about 50-40 degrees F, will I see any difference in condensation inside the T? Camp Inn says yes/No?

In the winter when the T is stored outdoors in the north (not being used for winter camping, which mine won't be unless its in FL or AZ etc <g>) will solid walls or insulated walls make much difference in the condensation/mold etc likely to appear over the winter? I think insulation would make no difference here because there is no difference between the inside temp/humidity and the outside temp humidity.

As to 'live in' use in the summer, I plan to have a Fantastic Fan or similar in mine and AC as well. If it is hotter in the T than outside, either of those (or an open window should be helpful) should handle the stiuation and insulation would not make much difference anyhow.

If it is colder outside, will sandwich/insulation in walls make much difference in temperature in the T (granting that the roof and floor are insulated. Let's say it goes down to 40, and I have nothing but two bodies to keep the T warm, will the insulation make a difference in the temp in the T--and if so approximately how much--2 degrees, 5, 10 20--and for how long?

Finally, would reflective paint--white/aluminum on the skin do a good job of helping cool the interior in the summer even if you don't insulate?

Sorry to be long winded, but I think all of these factors weighed together will help all those those who build understand the effort/benefit/cost ratio...and make the decision that works best for them...

Thanks everyone!

Jim
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Postby asianflava » Thu Jun 29, 2006 8:50 pm

I built mine totally using sandwich construction. The floor, walls, cabinets, shelves, and roof; everything except the drawers, some cabinet doors and face frames.

Is it worth the extra effort? I say yes. Once I figured out how to do it, it wasn't that bad. The first side's framing took me all weekend but the second one was done in one night. I made a template so that both sides would be the same. It came in handy, I recently had to pull it out to set up my hatch struts. The main thing is, know where you are going to install everything beforehand. You have to install a strip of wood to back up the screws, otherwise they will pull thru.

From my rough estimates, I figure my walls to be 3/4 the weight of a standard 3/4in ply wall. That is a 1in sandwich; 1/8in skins and 3/4in framing and insulation. Another advantage was, I was able to glue mine up to make 4x10 panels. One thing is for sure, it was a lot easier for me to wrestle those panels by myself.

We camped it both heat, around the upper 90s and cold (for us), in the lower 40s. It rained both times so we experienced extremely high humidity. The only condensation we encountered was at the hinge. There is nothing you can do about that since there is direct conduction from the outside to the inside.

I didn't think building it was that bad. But like everything with building teardrops, it's up to you. Do the pros outweigh the cons? I don't know. Not until I've built and used an non-insulated trailer will I be able to give a definitive answer.
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Postby madjack » Thu Jun 29, 2006 10:50 pm

...let me echo(sorta) asian's last paragraph...specifically this...my experiences are with a solid wall construction...I have never used or built a sandwich wall for comaprison...
...My thoughts on the matter stem from the fact that the volume and surface areas on a TD are just so fracking small that it just doesn't seem like it would make a great deal of diff either way...as I and many others have said...it's yours, doit like ya want to...
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Postby riverfront » Thu Jun 29, 2006 11:12 pm

This is great information - just what I was looking for when I started this thread - THANKS!!!

Nuder question:
Has anyone a cost comparison between sandwich and 3/4 ply? Please specify size inner and outer ply etc... I can get a local price on 3/4 but someone out there should have a cost per sandwich wall figured?

Has anyone built both and what are your thoughts?

Thanks again!!!
Bruce
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Postby Todah Tear » Fri Jun 30, 2006 5:56 am

To address the moisture issue during storage, or during use for that matter, has anyone ever used dessicant pouches (a substance that promotes drying. e.g., calcium oxide absorbs water and is used to remove moisture). Sometimes when you receive a product by mail, the box will have a dessicant in it to prevent moisture accumulation. They are also used in facilities to help control moisture around equipment.

Perhaps, a few pouches (strung like potpouri pouches) strategically place would help control the moisture prob. :roll:

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Postby Joseph » Fri Jun 30, 2006 7:04 am

riverfront wrote:First: IF the floor and roof ARE insulated (which I am doing) will insulating the walls make much difference in condensation when using the trailer? When storing it in Northern winters--very damp?

Why insulate the floor? The mattress will do that.
Second: When building sandwich contruction, what in the world do you use to attach 1/8 inch ply to walls and roof?

PL Premium Polyurethane Construction Adhesive. Check out the "Teardrop Construction" album on my Yahoo Photos page.
Has anyone a cost comparison between sandwich and 3/4 ply?

Well, mine was rather pricey since I used six sheets of high-dollar 3mm marine plywood at about fifty bucks a sheet. Cheaper luan would save you a bundle. Also, if you're skinning the outside in aluminum you can dispense with the outer layer of ply. But a cost comparison should be easy enough to figure out with a visit to your local lumber company.

Weight-wise, I can tell you exactly what mine weighs, since I weighed everything before assemby - the sides (including door, window and hardware) weigh 42 lbs. each.

One final thought - if I were going to build a single-wall trailer I'd use 1/2" plywood for the sides - that's how my '70 Scotty was built.

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Postby Sonetpro » Fri Jun 30, 2006 7:47 am

After thinking about it. Mine is not fully insulated. I only insulated the cabin. The bulkhead between the cabin and the galley is also insulated. The galley is solid wall.
Another advantage to the frame and insulated was the ease of the inside roof installation. It layed on the shelf built with the frame construction as per Steve Fredrick's techniqe.
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Postby Miriam C. » Fri Jun 30, 2006 10:28 am

Temporary Hijack,
Todah Tear wrote:To address the moisture issue during storage, or during use for that matter, has anyone ever used dessicant pouches (a substance that promotes drying. e.g., calcium oxide absorbs water and is used to remove moisture). Sometimes when you receive a product by mail, the box will have a dessicant in it to prevent moisture accumulation. They are also used in facilities to help control moisture around equipment.

Perhaps, a few pouches (strung like potpouri pouches) strategically place would help control the moisture prob. :roll:

Todah


Todah and all,
They make larger cans of that for closets and small rooms.

Joseph,
Did you use the "construction adhesive or one of the others PL makes?

Back to walls.
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Postby kayakrguy » Fri Jun 30, 2006 11:21 am

asianflava,

About those 4 x 10 walls...did you build them from regular 4x8 sheets or did you buy 4x 10 x 1/8 sheets?

If you used 4 x 8 where did you put the seam? I am puzzling that question-- if I used 4x8 I dont want the seam near door, dont want it near hatch...?

Jim
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Postby alaska teardrop » Fri Jun 30, 2006 1:27 pm

    Other than the interior panels, I use no wood in the walls, roof or floor (odd ball around here). :? But, I do have some experience building homes in the arctic. So, my 2 cents.
    The studied experts advise twice the insulation value in the roof & floor as in the walls, because the heat loss is about half. While wood retains heat within itself (log cabin), it has virtually no insulation value. The framing in a stud wall is a thermal break. An example of this would be my own cabin, because the sun doesn't melt the frost on the north wall in winter. And even though the interior is completely sheathed with urethane isocyanurate and vapor barriered you can see exactly where all the studs are from the outside. Just like an infrared picture. Therefore, in a sandwich wall, floor, roof teardrop, you must subtract the area in square inches of the framing from the total to obtain the truly insulated portion.
    Furthermore, unless the framing is totally vapor barriered on the inside between the interior panel and the framing, moisture will eventually penatrate into the wall, roof and floor. Have you ever been in an old pre-vapor barrier house where you can see all of the drywall nails/screws under the paint? That's caused by moisture from the inside.
    If I were to build with wood, I think that I would choose solid walls for these reasons and the ones already mentioned.
    Fred :peace:
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Postby asianflava » Fri Jun 30, 2006 3:15 pm

The sidewalls are made from 4X8X1/8 luan, the seam is along the hinge line of the door.
It is obvious in this pic:
Image

The reason I put it there because the framing is thick there and it runs from top to bottom. Everything else except for the top roof skin is 5X5X1/8 baltic birch.

This is how I attached the roof to the walls. It looks like there is no mechanical attachment between the top skin and the wall but actually the aluminum trim has screws that go thru.

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Postby Miriam C. » Fri Jun 30, 2006 3:30 pm

Asianflava,
What have you used to attach the 1/8 to the framing?
(I really appreciate that you guys are reviewing all this since I am (someday,) putting walls up. Starting on inside since I have wood for it.
Miriam
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Postby Ira » Fri Jun 30, 2006 3:37 pm

I came to this party late:

The Cubby plans just call for 3/8" ply walls, and only 1/4" interior skins. (I myself just used 1/8" beaded birch for the interior skins on the sides, and 1/4" bendy birch for the interior roof, because the place didn't have 1/8" bendy.)

Framing with 1 by 2s, this gives you room for 3/4" insulation on the sides, and 1 1/2" in the roof.

I guess the point I'm trying to make is you can make it sandwich-style and still make it real light and strong. Heck, mine survived Wilma without even hardly moving from its SPOT, whereas boats were flown all over the place right near me.

Thank God none of them hit ME.

And I guess it bears repeating (bares?), because we have a lot of great new guys here and I haven't seen this sentiment posted in a long time:

A lot of us overbuild the CRAP out of these. It might make us feel good to do so, but it isn't necessary and probably worse than just going with that we really need.

Ahhhh...I still remember the poplar spars versus pine spars war. I enlisted with poplar, but who the hell knows for sure?
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Postby asianflava » Fri Jun 30, 2006 3:58 pm

Miriam C. wrote:Asianflava,
What have you used to attach the 1/8 to the framing?
(I really appreciate that you guys are reviewing all this since I am (someday,) putting walls up. Starting on inside since I have wood for it.
Miriam


I used epoxy thickened with microfibers. I may have used a staple or 2 but that was just so the skins wouldn't move when I used my gravity clamps.

Scroll down to the bottom of this page http://asianflava.journalspace.com/?m=11&y=2004 and work your way up. I have all the pics on my build log. Eventually I will make a different webpage that organized by assembly rather than chronologically.

The roof skins were held with PL polyurethane caulk and brads. I did put screws in the sides but they were removed after everything set up.
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