Stress Panel Construction

[angib]

Rocosil,

It seems to me there are a lot of older trailers around with very light single-skin and double-skin panels. The loads to be carried in a teardrop are so low that it is the durability of the skins (puncture resistance, for example) that is the limiting factor on skin thickness, not overall strength.

If a single skin of 1/4" ply with a bit of framing is strong enough, why make the structure much more difficult? I'm a great fan of double-skin construction (built many racing yachts that way) but the strength and stiffness isn't really needed for a teardrop.

Just my twopennyworth.

Andrew

[Arne]

That stuff is impressive.... if you use 3 pieces in a 3/4 inch space you get an r value of 12? expensive, but one roll might do a whold tear with very impressive insulation values... never seen the likes of it before...

5 to go.......

[Chris C]

Yeah, arnereil, it's great stuff. I've been in my van in below 0 temps and the little ol' engine heater will just about run me out of the vehicle! Likewise, in the summer, the standard A/C keeps the entire thing cool. Amazing.............expensive, but amazing. I'm for comfort, if given a choice, and will gladly spend a little extra for insulation.

[Joanne]

Among the many posts related to framing and light-weight, insulated construction I have yet to find any reference to building TDs with stress panels. Maybe there is a thread on this subject somewhere in this marvelous forum and I simply haven't found it yet. The search feature gives me lots of returns for "stress" and for "panel", but not for the two words linked as one concept. If it is somewhere, please point me to it and don't bother to read the rest this voluminous blather.
Cheers,
Bob

Hi Bob,

http://www.oneoceankayaks.com/Sandcore.htm

Although this isn't exactly what you were speaking of, it does address some of the technical aspects of stressed skin dynamics. I'm not an engineer and don't play one on TV, but I'm enough of a nerd to enjoy reading pages like this or Andrew's discussion on trailer tongue strength.

Joanne

[George Kraus]

Here is the guy that is doing what you are talking about http://www.happitrails.com

[Rocosil]

Thanks for that link, George. That's exactly what I was after. I'm happy to know that someone is using this type of construction and, being an old oil-patch hand, I'm quite comfortable with the West Texas way of making things hold together. Now all I have to do is work out the details.
I'm thinking of going with clear-finisheded hardwood ply, and covering the outside with epoxy and glass, a medium I'm quite familiar with, because of the structural integrity it provides when used over joints, as well as the impact resistence it would give to the outer skin.
I've been admiring the "sandwich" construction that Steve Fredericks, AsianFlava, and several others have been doing, but I was surprised by the amount of structural lumber that goes between the the two skins. I figured there had to be a way of making the foam carry more of the structural load and provide more efficient insulation at the same time. Looks like there is.
Mmmmm, now I have to start thinking of how I would go about making a trailer frame out of laminated ashwood. I bet that's been done before as well.
Cheers,
Bob

[denverd0n]

I was surprised by the amount of structural lumber that goes between the the two skins.

Well, you have to have structural lumber in there to support the doors and cabinets. Most of the sandwich-wall teardrops I've seen only have structural lumber around the outsides and in the places where other stuff needs to attach to the wall.

[Rocosil]

No doubt you need some, but my goal is to keep it to a minimum. As I said earlier, where you need it for doors and windows you can route out the foam and glue in wood. Cabinetry can be self-supporting and moved in as a unit. All you need is some minimal hardware to lock it in place. Alternatively, you can build it up on cleats glued to the inner skin. Even 1/8" ply can support a lot of weight in shear. I admit, I don't know much about teardrops, but I have built a few boats that weighed less than half what their conventionally built sisters weighed, and they were just as strong, or stonger. So, while I admire the fine work being done, as I study the various building journals, I get the impression that many of those tears are over-built. I understand perfectly that if you put that much money and effort into building one of these things, you don't want to take chances that it will come apart on you, particularly not while you're on the road. Most likely, what I have in mind won't work, but if it does, I'll get a kick out of having tried something just a liitle bit different and succeeded; even if it won't revolutionize the way people build tears.

[angib]

I get the impression that many of those tears are over-built.

If you're gonna get serious about lightweight construction and you do good joints, then I'd guess that 1/16" ply either side of 3/8" Divinycell or Corecell would make a perfectly sound teardrop body.

But 8" wheels are going to be too heavy for this application and you're gonna have to make your own aluminum suspension....

Andrew

[mikeschn]

and you do good joints

Is that what you have in that pipe of yours?

Oh, I think bicycle wheels are in order for ultra lightweight wheels!

Mike...

[Chris C]

I would think two skateboards would be even lighter than bicycle wheels, don't you agree, Mike? That would also lower the tear so it projected less surface area to the wind.............so it would sort of "draft" behind your vehicle.

[Rocosil]

make your own aluminum suspension....

Andrew[/quote]
So you think that laminated ash would be to heavy ?

[angib]

So you think that laminated ash would be to heavy?

No, the laminated ash is fine, but you just can't get the leather straps like you used to.....



Andrew

[Rocosil]

And you had the last word on this subject! Thanks for playing.

Cheers,
Bob

[Chris C]

No he hasn't!!!!! That's got to be the best looking "tear" I've seen on this site. The craftsmanship is right up my alley!!