Teardrops n Tiny Travel Trailers

Thought experiment, please link to relevant previous discussions, or images / web pages to inspire brainstorming.

Flexible but strong structural framework, maybe temporary if no heavy roof / rack loading.

Curve / shoulder shapes and dimensions optimize balance between slipstreaming vs standing / storage space.

Maybe screening fabric for added strength, aluminum vs plastic?

And/or traditional dropcloth / canvas.

Not flat boards with 90° corners for foam though, the fabric gets stretched over the "sapling" framing, maybe bracing / twine tensioned to get everything nice and rigid, then spray or paint the Glidden Gripper (or what?) to "freeze" the shape

Coat, dry, further coats, maybe measure to get PMF shell to a given standard thickness.

Obviously a manufactured smooth rigid "mold" for commercial production, but I'm thinking hand made artisanal primitive roughness is part of the charm.

Once done, 100% dry and judged "strong enough" on its own

**spray** two-part urethane foam to the inside, again optimizing balancing lost space vs need for extra strength or insulation for a ski-bum scenario.

Even coverage a big challenge here.

Maybe an inside vs outer skin, gap in between then use two-part **poured** urethane foam. Denser at the bottom, lighter at the top?

Plastic pipe used for the sapling framing between skins, fill with dense foam, very rigid shape before skinning, no thermal bridging, likely load bearing enough for panels up top.

Semi-flex panels fit to the curve but mounted rigid, very light?

Entry / windows could be framed in, likely easier to get openings waterproofed, but maybe just do a unitary sealed shell for strength and shape-integrity, then cut out and frame later.

Okay, just for the sake of discussion:
Skin the inside first.
Spray the foam on the outside surface.
It is far, far easier to sand and shape the outside in prep for the outer skin, than it would be to sand and shape the inside to prep for the inner skin.

Better yet, keep it simple and be camping already.

What is this "skin" of which you speak, what sort of substance?

I was thinking the initial structural surface would likely be exposed, whether inside or out.

Hope the materials tech and application method would ideally not require any sanding or shaping.

If there's both an inner **and** outer structural surface, then the poured foam fills in the gaps.

Key for an engineered-look aesthetic would be preventing either skin from getting deformed from too-forceful expansion.

But if a rough / primitive, "organic" look is the goal, lots of room for irregularities.

> Be camping already

Different strokes. . .

I always thought that was a credible idea ...

Yes that's the "organic" aesthetic.

My thought is to get that slipstream effect and frugal simplicity in a larger size, using more modern materials for durability and thick insulation.

Thinking maybe combine with that "Duckworks split shell pop-up" idea, bottom say 3-4 feet of the walls would need to be vertical.

You posted a pic of a ground-based structure in your original post. Is that what you're looking for, or are you looking for a mobile shelter?

If a mobile shelter, you might want to look into the "gypsy wagons" of a foregone era. You might get some ideas from that.

Roger

Yes, seen those, and the Vardo designs.

I'm just spitballing using that basic form factor as the basis for a mobile living space.

Aerodynamic and very efficient, while still IMO suitable for implementing with cheap / low-tech construction methods.

Aesthetically might not appeal to current mainstream tastes, but I think calls back to Bucky Fuller, or rather, his designs called back to the indigenous designs.

I really like the idea of a lashed frame.
Skin on frame kayak sort of thing. Much stronger than fastening by drilling a hole through the spar and it will flex.
But the sapling idea is too irregular to use realistically unless you can refine it. Whether you use a table saw to rip and then laminate curved members with epoxy (fast and strong) or go primitive and shave pieces down on a horse with a draw knife (painfully slow) or somewhere in between the skin will want to be relatively smooth which will require fair and refined spars. Further refinement might be to carve recesses to make the lashing lay flush. Scarfing long pieces are totally possible with lashing providing there are cross dowels of some hard material to keep the pieces from sliding.
Then there is the skin. Leather or animal skin and tree bark have largely been superceded by synthetics but canvas and paint could work. My preference might be nylon and Titebond II. Then again you could pile up dirt in a rounded shape the way you want it, lay burlap feed bags over the dirt, spray with foam stuff, then coat with PMF. No framing needed as long as all your walls were compound curves for eggshell strength. Even layered paper layed up with glue or paint would work.

Yes, my thinking personally is modern manufactured high-tech materials, just stealing the shape and general idea.

Adhesives are crazy strong and reliable nowadays, many acting as sealant, remaining flexible forever too, I don't see lashing / scarfing etc needed myself.

Any flexible or bendable tubing will act as main load-bearing support "saplings". Bigger / stronger in fewer numbers spaced out, or lots of weaker ones like a basket-weaving concept would both work, I think the latter likely to both be stronger and give a more unified aesthetic.

Pretty sure Glidden Gripper will be better against water long-term than TB2.

And sure, expensive synthetic may be worth the extra cost, but I'd start with cheap dropcloth or ex-hospital sheets.

I like the positive mold idea, but sprayfoam as the main structural element would I think need to be reinforced somehow even if sprayed pretty thick, with highway-speed wind forces, tree branches off-road etc.

But maybe not, would be cool to try, big long pile of sand somewhere would certainly be a cheap.

I like the idea of a catenary arch profile, so maybe a negative mold, cloth, strings, netting suspended from a tall frame, doing the PMF / papier-mâché process "upside down", and/or pouring the foam rather than spraying, might give good control for a nice smooth shape.

I remember seeing a demo of very hard dense foam, painted over a balloon. . .

I was thinking that what would allow one to eliminate some or most framing would be if the walls had compound curvature. Curving in both directions. Most teardrops I see have flat walls and many have flat areas in the roof. Adding just a slight curvature adds a lot of strength. Making a compound curve with a flat piece of plywood is difficult or impossible. Compound curvature would be an advantage that flat materials would not have. Many natural organic life forms use this concept. Turtle shell, Egg, seeds, Insect bodies. Very few use flat two dimensionally curved structures. I cannot think of any but there must be some. A catenary arch is a two dimensional curve. A three dimensional curve (could be catenary arches going both ways) would be stronger. Google https://www.bing.com/images/search?q=anagama+kiln&id=594845D77246F18FBD6047C90F3088B54A9D4821&FORM=IQFRBAAnagama%20kilns to see what I'm talking about.

VT Steve’s right !!! That’s why we did the FoamStream that way ( much Stronger )

The Foamstream appears to use compound curves only on the upper part of the nose. Is that right GPW?
The rest of the body appears to use two dimensional curves. I could be wrong. I have yet to see a truly compound curve structure
on a teardrop except for the commercial fiberglass molded Mypods and a few others. https://www.bing.com/images/search?view ... tedIndex=5
The Plywood kit by Chesapeake Lightcraft are close but are actually curved flat panels.
I think skin on lashed frame maybe with a double fabric wall with foam injected between might be possible, Could be super light and strong.

The shape is exactly what interests me.

A fat sausage is a simple curve along the cylinder section, but sliced longitudinally the bond with the flat floor gives a very stable arch.

Further strengthened by the semi-hemispherical, or ellipsoid ends, there's your compound interest.

The big challenges afaic are practical / build implementation, not design / theoretical.

If mass-produced like Airstream, a big investment in high-tech molds etc is justified.

A limited-budget DIY once-off can get the functional stuff down, but getting it to "look nice" will be **hard** for a noob like me.

Also, now that I think about it, What about using the same concept as the Chesapeake Lightcraft but doing it in say 1/2 inch foam? the foam panels are bent with one curve meeting another...like a barrel stave sort of. Like comparing the strength of a barrel to the strength of a box. I can imagine cutting several staves from one pattern and springing them together and holding them with tape and covering with PMF or epoxy. No framing at all.

Sure with a good CAD/CAM setup and a CNC router to get the gores just right.

http://mathforum.org/library/drmath/view/55168.html

Maslow open hardware / FOSS model might just be precise enough, but $500+ investment and that's **super** cheap for a 4' x 8' unit.

https://www.maslowcnc.com/

Personally I think you'd still need mold / bracing to keep the shapes precisely in place while bonding the gores together, then canvassing, painting etc.