Trailer roof edge question.

[freebeard]

Well, it's what you get when you push the 'aerodynamic trailer' hot button.

Thanks for the opportunity to hi-jack your thread. If you combine the squircle and that gypsy wagon with this:



you've got my current thinking on a teardrop—the Aerodynamic Template rendering in curved fiberglass rod. It would have a inner lined with the rods through sleeves and then a sock pulled over the outside.

You could think about the plan taper starting at the tow vehicles rear tires. Swap your pickup box for a utility bed with outside storage. Then round off the rear corner lockers following Mair.

The house-on-a-truck had a custom flatbed with curved sides. And he is 6'5" so he made the roof shoulder height and then put a plexiglass bubble at the center top that fit him like a hat.

For the overhead storage look at aerohead's post on canopy drag

Edit: Here's a rear trailing edge by Luigi Colani for one of his Bonneville racers.



The lower scallops act as endplates for a divergent duct, then the sides are cut away for better sight-lines. The long, flat duck-tail comprises a box cavity. The backlight is flat on the bottom but about 120° of circular arc on top. And angled back so the whole back of the car is a diffusser.

Also, PVC and fiberglass are nasty stuffs. What about redwood and cedar. Or prefinished sheets of something? My vote for better materials/less finish work would be bamboo slats rabbeted for Polymetal fill panels.

[ThomCat316]

Hijack away! You're sticking to topic, regardless of how much your topic and mine are diverging... You're enjoying the "road less traveled"!

As for material choice, I'm soooo at home with composite structures that your suggestions seem like daunting tasks in comparison (but I'll bet you don't have a 6'x20' vacuum table for making up panels!) I like the variety of means to ends I find out in the BBS world - I learn a little something almost every time someone takes the time to type it out, even if sometimes it takes me five readings to make it sink in to my skull.

Typically I'll use PVC in two ways - either as a very well controlled slightly flexible (pipe) mold surface for rounded sections or as easily fabricated light (foamed PVC) sheet goods, though often I'll use polypropylene honeycomb sheet faced with fiberglass as a lighter alternative. Laminating three 1/4" layers of honeycomb under vacuum over a PVC pipe mandrel makes for a very light and rigid curved section that bonds very well into flat and curved panel sections to make up a stiff monococque structure, removing the need for a separate frame for the trailer, significantly reducing weight and complexity. I use pultruded fiberglass sections as edge stiffeners and fastener rails in the lower part of the trailer structure.

The sail-like Conestoga top will be getting a representation on this trailer, as the planned side-shade tunnels. I don't like having "stuff" sitting in the boundary layer, so I'll be building pockets into the solar panel fairings to accept battens for a curved side-shade "porch" like all good RVs seem to have. This one will be more durable than most seem to be - I am trying to find a source for remnant Tenara cloth.

[freebeard]

Thanks. There's another thread I could mention where I seem to have sent the thread completely off the rails.

Alrighty then! I was picturing a frame made of PVC with the fiberglass cloth stretched over it and the resin painted with a brush. With vacuum-bags and pultruded sections I can see how a monocoque is a reasonable goal.

I look forward to the pictures. I hadn't heard of foamed PVC sheet so I Googled it. And the pockets for the curved side-shades will be interesting.

I've been known to draw a sketch with a sharpie, take a picture with a pocket camera and crop and sharpen it in Preview.



What do you think of basalt as a material? Basalt Guru, your source for basalt information and products.

2015 Tesla Model S builds bodykit with basalt fiber
Posted on April 29, 2015 by Basalt Guru • 0 Comments

The new Tesla Model S Elizabeth by Larte Design includes basalt fiber on top of carbon-fiber-reinforced plastic (CFRP) in the bodykit. The basalt fiber has better physicomechanical properties than fiberglass, and is significantly cheaper than carbon-fiber. Plus, basalt fiber has higher impact resistance and toughness, as well as shock-absorbing properties, which not only make the Model S lighter, but safer in case of a crash as well. The material is also resistant to moisture, salt solutions and acids. Larte says basalt fiber is the future and we certainly agree!

[ennored]

I'll drag up an old thread:

Aero trailer mods

Because that's where I mentioned one of my favorite aero trailers (that's an actual, useable, built in a driveway, trailer):

[ThomCat316]

Unfortunately, I am a better builder than artist. My "sketches" usually need a translator.

As for basalt, it's not here yet in my opinion. I LOVE the concrete reinforcement products, but the price and performance niche that the impregnable fabric occupies for now is not attractive. Yet.

It has the potential to have wider acceptance in the market, but for now.....if performance boatbuilders are using S-glass and carbon fiber instead of basalt, there's likely a reason.

The folks here - Basalt fibreglass - have a nice discussion about it.

[freebeard]

ennored -- the boattail is visible as a shadow on the ground. Doesn't it clam-shell open just ahead of the taillight? Aluminum truss and skin sides and top?
________

I'm pretty interested in basalt. deejaaa showed some samples at http://ecomodder.com/forum/showthrea...tml#post437859 but I never saw any result of the testing we talked about there.

The linked discussion was interesting, positioning it relative to E-glass, S-glass and carbon fiber. Sizing vs sizing, etc. I was thinking more along the lines of a fishing-pole-sized frame with a flexible skin in tension.

[ThomCat316]

Originally Posted by freebeard

...but I never saw any result of the testing we talked about there.

You might consider sponsoring the materials and labor for a Hydromat panel test (see "The Importance of Testing" in this article) using comparable weights/thicknesses/layups of E-Glass, S-Glass and Basalt. Gougeon Bros./WEST System is very helpful with this sort of thing, and they love to see folks creating interesting things with their epoxies.

The linked discussion was interesting, positioning it relative to E-glass, S-glass and carbon fiber. Sizing vs sizing, etc. I was thinking more along the lines of a fishing-pole-sized frame with a flexible skin in tension.

I'd strongly suggest staying away from glass/basalt/carbon for this sort of application, and going in one of two directions - PVC or urethane coated polyester fabric, or polyester aircraft covering fabric (cheap, easy to fabricate) or Gore Tenara cloth (expensive, difficult to obtain, challenging to work with). Both are used in tension structures. The problem with using the stiffer (glass/basalt/carbon) fibers in inherently flexible skins is that the individual fibers tend to break at the flexure lines, causing eventual linear "zipper" type failures.

[freebeard]

Ah well, I was hoping to end up with a fireproof Faraday cage teardrop trailer. That I could sell to the 'preppers'.

[ThomCat316]

Originally Posted by freebeard

Ah well, I was hoping to end up with a fireproof Faraday cage teardrop trailer. That I could sell to the 'preppers'.

You could always laminate a layer of copper mesh in the layup....

Looking at the prices for Faraday cage materials, I think (if I were concerned in that way) that I'd just optimize my EMP-sensitive stuff to be primitive (easy to fix) and small (easy to stuff in aluminum boxes). Additionally, for high levels of energy you'd want your cage to be perimeter bonded to a solid ground....

(I'll see your "off topic" and raise you a "meandering all over the place")

Now where were we?

[freebeard]

Somewhere around here:



So the monocoque box, door and it's frame and a dorsal rib are achievable with epoxy or other resins. Even the curved, fishing-pole sized ribs. What I'm not finding is whether it's possible to weld basalt rebar.

I'm not even sure if you can make a Faraday cage with a dielectric material. But the fire-proof, bullet-proof, shock-proof parts are still there.

And there is a glass-coated fabric that takes resin without changing color so it stays a nice golden-brown. Wrap the door with that.