Frameless construction

[reiltear]

Hi everybody!

I don't have a teardop yet, but plan on starting to build one right after the holiday craze. Recently I got hooked on the "frameless", "trailerless" or "ultralight" designs, such as Mike's ultralight and Dwgriff1's TDs.

One thing that I wasn't so sure of is the platform design. The usual "overbuilt" concerns, or "better" still, the thing one put so much time, effort and money into falling apart on the highway...

I asked almost everyone at a local college and looked on the internet about the torsion boxes, but came up with one of the two answers - duh? or doh?. I didn't give up though, and last night I typed "honeycomb panels" into the search ebgine and came up with this:

http://www.bellcomb.com/detail.asp?PRODUCT_ID=BSP1183

This should lead you to the description of a honeycomb panel that might become a boon to teardrop builders.

What do you all think? Pro's and con's? I personally don't care if their sales go up or down, just asking for your opinions(I remember how a lot of people "circled their teardrops" against a "new manufacturer" not long ago...).

Thanks in advance, Ilya

I'll be back here this evening [/url]

[angib]

Welcome, Ilya.

I ran some numbers on that sandwich panel and I reckon it's got 50.3 lb of ply, leaving 5.3 lb of paper core. It is much stronger than is needed in a teardrop - it's easily strong enough to support sleeping elephants, instead of people! Really we need something with 1/8" skins, though that might be sufficiently 'puncture resistant' for the top skin, even if it is strong enough.

But all ready-made sandwich panels suffer from the problem that there's no easy way to join them - you really need to router out the core material from the edges and let in a solid wood insert (say, a 1x2) to which the rest of the body can be fixed. The same is true to a lesser extent where the galley bulkhead comes, though probably gluing and screwing to the top skin is sufficient there.

And finally, it could be a real nuisance that these panels are 47.5"x95.5", though the 47.5" width shouldn't be a problem.

You could make a sandwich panel of your own with a 1/4" top skin, 1/8" bottom skin and 1x2s running crossways at 12" centres. It would weigh 2-3 lb less than the sandwich panel, cost maybe half as much and be perfectly strong enough.

If you want to go to a full laminated sandwich panel, you would do well to copy Rik Keller's panel construction of 4mm (5/32") birch ply skins bonded to a 3/4" Styrafoam core, with some 1x2 framing at the edges. That would be about 12 lb lighter than the honeycomb sandwich panel.

Andrew

[EZ]

At 56 ponds it seems kind of heavy. Moisture resistance is fair. Fire restistance poor. What is the R-value? Seems to me that the sandwich panels many of us already build weigh that little, insulate great and are much more moisture resistent. Cheaper too.

Ed

[reiltear]

Thanks a lot to both of you!

As far the elephants go... I am trying to avoid the trailer a la Superleggera, or I would actually prefer to have a single 2" square tube like Mike's Ultralite. I can see the attachment problems, but I do own a very nice router, so the only thing I was worried about would have been Kraft paper wrapping itself around the bit... until I saw the $50 handling charge for orders less than 10 panels!... plus shipping... There go the labor savings!

I looked at Rik's design and it doesn't seem that there are any weight advantages - at 2 lbs per square foot his floor is actually heavier(64 lbs for a 4X8 platform vs 56 lbs for the honeycomb), PLUS it sits on top of a steel frame. The last 2 things in defence of the honeycombs are:

1 Assuming the TD is built weathertight, like they all should be under ideal sircumstances, water resistance most likely won't be an issue. Don't most builders paint their TD's bottoms with some kind of waterproofing anyway?

2 Fire resistance poor? Unless the TD is clad in aluminum, the varnished plywood goes off like a roman candlelight - Iwouldn't smoke in one of them things unless somebody paid me $1,000,000, and then I'd upgrade to a bigger tent on wheels... like a B-Touring Cruiser maybe...

All things said, I'm going back to the drawing board, you guys convinced me!!!

Ilya

[asianflava]

The final weight will depend on how many stringers you install. My floor was (5'X9') was 71lbs. You could use the honeycomb but it will be pretty expensive. There is also a question of how to closeout the exposed edges.

[dwgriff1]

The final weight depends on a hundred decisions that add a few ounces at a time.

A single layer of 1/8 on the floor would support a mattress, but would seem flimsy while under construction. A few scraps to kneel on (they could be 3/4" for that matter) would solve that.

The ribs can be milled pretty thin without compromising strength. The one place I want strength is on the tongue wood and the side wood where the axle attatches.

It will be a trick to get an insulated and lined 5 by 8 to weigh much under 500#, I fear.

dave

[TRAIL-OF-TEARS]

couldn't you use hollow core doors like Rolly did on his stacker? I think you could use 2 doors put together. that should be light and cheap-ish.

I just used 1/2" ply, for my floor, bolted to a minimal trailer frame.

[alaska teardrop]

1 Assuming the TD is built weathertight, like they all should be under ideal circumstances, water resistance most likely won't be an issue. Don't most builders paint their TD's bottoms with some kind of waterproofing anyway? Ilya

Ilya,

Right on. But the other source of moisture damage to the floor, roof and wall cavities comes from interior condensation. Therefore, IMHO, extruded polystyrene (XPS) is the best choice for strength, moisture absorbsion resistance and resistance to moisture damage.

If you haven't already seen it, here's an interesting link to a discussion of what you might have in mind. http://tnttt.com/viewto ... light=sips

Good luck on your new project, Fred

[Roly Nelson]

The floor on the "Stacker" is holding up fine. Remember, we never stand on the floor, just sit or lay on it. I strengthened my edges with solid douglas fir lumber, glued in place with the trusty Titebond II. If additional strength is needed, another layer of 1/8" should do the trick.

Roly, always recommending that we think out of the box.

[dwgriff1]

There is nothing wrong with using a hollow core door.

Shucks, why not just make one, and make it any size you wish!

Substitute foam insulation for egg crate and you can do it!!

dave

[Arne]

My current thinking is 3/8 on top, 1.5 inch high stringers (probably 1/8 or 1/4, spaced every 8 inches) and foam core, and 1/8 on the bottom.... No trailer frame x-members except front (for strength) and back (where heavy battery, microwave, etc. will be located)... It will be heavier than I would like, but it will be insulated and rigid, and probably a tad lighter than an uninsulated 3/4" floor.

[dwgriff1]

Arne,

I'll bet you could leave out half of that and stilll get a solid build.

dave

[Arne]

re the top, I sit on a milk crate and slide around to paint the inside... yes, after it is done, could probably be 1/4", but I'll bet I slid around 1/2 mile doing paint, wiring, molding, etc... just a little reluctant to go thinner.. but then, I have not started building no. 2 yet... but getting close.

[dwgriff1]

I prefinished all the component parts so I spent about an hour actually inside (before I started sleeping in it).

You are courageous, I am lazy!

I have double 1/8 floor over panel insulation and single 1/8 underneath. If I were doing it again, I'd go with single 1/8, and add a few pieces of 1/4 or 1/2 where I was kneeling and working, then take them out when I finished the build.

dave

[Arne]

Ah, prefinishing makes a lot of sense... never really thought about it.. I usually build and assemble then paint... not build, paint, assemble and touch up... but I sure like the idea...

Could do it with the wall, but i don't think I could with the ceiling.