Project, the Third - Now contains collabsible boat tails (1971 VW SuperBeetle)

[freebeard]

Thanks for the custom builders.Looks like they spent thousands of hours having a lot of fun.Nice stuff!

While they were being paid for it!

I've ended up living inside a sort of inverted ferro-cement hull.Living in 'Tornado Alley',it helps a little.

Given that 'low-cost energy-efficient and aerodynamic housing" is an area of interest to me; I'm curious about that experience.

In the 80s I worked as a designer and tooling maker for a geodesic dome manufacturer. They had a picture hanging in the in hallway of an aerial view of a Texas[?] town after a tornado. It looked like an unmade bed, except for a white hemisphere set in the middle. It wasn't their product, probably a Monolithic dome.

I haven't made much progress on the boat-tail; but I weighed the redwood bender board. It's 6 1/2oz/sq ft, so this:

at ~16 sq ft would weigh ~6.5lb. Boxing in the top and bottom would add 8 sq ft. Add 40% for framing and braces and another 10% for gussets and it would weigh ~15lb. At that you could still lift it off for engine access. Full Tropfenwagen would require access hatches. It will use oak dowels where the bike rack mounts now. I've been thinking about how to clamp it to the drip rail.

Remember the Coanda nozzles? Look at this:

That's really close, all it needs is more lip on the inner edge of the opening and it's there.

[aerohead]

Our community's founder had built a ferro-cement yacht,and it occurred to him that one could invert such a structure to create a robust earth-sheltered structure.
Ours are created from an armature of rebar,remesh,and hardware cloth (or expanded metal lath) which is united to the rebar in the slab,then hand plastered with an 8-sack sand mix concrete containing a vinyl bonding agent.
At the time (1981) I did mine the rough structure was costing about $10 /sq-ft.
I had mine foamed with 20-lb/cu-ft density polyurethane.If it ever gets finished and buried it will have the equivalent of around R-90,factoring the thermal flywheel.
It's a 'tiny home' before such things existed.
The dome in your photo,no doubt is from the Monolith folks.They were (are) inflating rubber domes under the reinforcements which allows a continuous 'pour'.It's a slick setup!
I've enjoyed mine.Hope to die there with or without boots.

[freebeard]

1981? That's about the time I was working as a carpenter in the Cerro Gordo Ecovillage. They had the community, but the finances turned into an ugly hairball.

So—started in '81 and not buried? Foamed on the inside or outside? How many square feet?

Having worked on a lot of domes, I got to live in one as a renter for 7 years. Happiest time of my life for varied reasons. It had radiant heat in the ceramic tile floor, and a hot tub in the bathroom.

I've got mixed feelings about Monolith. I don't think spraying concrete against a pneumatic surface give much control over the shape/surface. Maybe they use higher pressures than I realize. And they seem to throw insulation at it until there is no further improvement, i.e., overkill.

Beyond this boat-tail business, I'm working on an 18' diameter garage that could also be an indoor windmill/solar heat pond. Trouble is I'm land poor.

[aerohead]

Originally Posted by freebeard

1981? That's about the time I was working as a carpenter in the Cerro Gordo Ecovillage. They had the community, but the finances turned into an ugly hairball.

So—started in '81 and not buried? Foamed on the inside or outside? How many square feet?

Having worked on a lot of domes, I got to live in one as a renter for 7 years. Happiest time of my life for varied reasons. It had radiant heat in the ceramic tile floor, and a hot tub in the bathroom.

I've got mixed feelings about Monolith. I don't think spraying concrete against a pneumatic surface give much control over the shape/surface. Maybe they use higher pressures than I realize. And they seem to throw insulation at it until there is no further improvement, i.e., overkill.

Beyond this boat-tail business, I'm working on an 18' diameter garage that could also be an indoor windmill/solar heat pond. Trouble is I'm land poor.

*Met a woman,there went the money.No real progress since 1983.Shifted into serious aero mischief-making instead of house-building.
*Foamed on the outside
*About 327-sq-ft living space (17-ft dome plus some alcoves),and rude,dirt-floored shop/studio
*We hand back-plastered the 'crete and Thorough-Sealed the inside as a high-albedo reflective stucco.
*I don't heat it.
*Lived off the grid for 10-yrs.
* I do air condition due to 'pestilential swamp' (Howard Hughes) climate.
------------------------------------------------------------------------
The garage project sounds like a bunch of fun,space allowing.

[freebeard]

[I'm living in 256sq ft. It's on the grid but I pay something like 5¢/Kilowatt-hour.]

I'm really slacking on this, but I went back into Wings3D and redid the two parts I'd made. I'm trimming as much as I can. So the lower aeroform is now not extended at all, where it was 18" before. I adjusted the contour on the upper part and shrunk it to fit closer to the drip rails.

Here are three renderings. I haven't dealt with lower difusser parts yet. The full deal:


The upper part lowered to allow engine cooling:


And the Upper part removed completely:


How much streamlining do you think I lose in the latter two? I think it would be considerable, because the vortexes would be back.

Edit: For sake of completeness:

[arcosine]

Why not get a kit car body.

[freebeard]

Originally Posted by arcosine

Why not get a kit car body.

Because:

• I already have a SuperBeetle
• It's already hard enough for me to get in and out of the SuperBee
• It's more of an intellectual exercise than a burning need to save gas in the 100miles/month I drive
• To prove a point (going from 0.42 Cd and 26mpg to 0.26 Cd and 42mpg)
• It's a goal achievable on my limited income (well, after the Holidays)
• I've stockpiled 100s of lineal feet of redwood benderboard and I'm looking for some way to use it.

Years ago, when I had a wife and 3 kids I wanted a 2-seater, the Amante/Gazelle:




I'm over that now. I'd be more interested in a fiberglass version of the Volkhart-Saggita (claimed 0.17 Cd):

[Sven7]

That last one's gorgeous. I'd like a 1:43 model of it!

You could probably mount some NACA inlets on the C pillar area of the boat tail and duct air past the cooling outlets, finally exiting the rear of the tail. The air moving through the ducts and into the wake would suck the cooling air right out, and probably not add too much drag- especially when compared to not having an upper part.

Actually, put the inlets up top like an RS200 (but of course use NACA ducts):



This is the one I'd choose, but it might be worth the effort of smoothing out those interior corners that develop between the rear fenders and the body sides. Think about building a custom rear bumper?



It would be neat to find a ratty Bug body , hack it off where your boat tail begins, and build a new rear end with perfect curvature.

Last thing.
If you're doing this version, use some '63 Thunderbird taillights to make it look like a rocket ship. And add NASA logos to the side

[freebeard]

That last one's gorgeous. I'd like a 1:43 model of it!

Thanks. Models scales drive me nuts. 1/10th? 1/18th? 1/24/25th!?! 1/32nd? 1/35th (military)? That said, I like 1/43 (easy to store), and 1/24th (1/2 dollhouse scale or 1/2" to the foot).

You could probably mount some NACA inlets on the C pillar area of the boat tail and duct air past the cooling outlets, finally exiting the rear of the tail. The air moving through the ducts and into the wake would suck the cooling air right out, and probably not add too much drag- especially when compared to not having an upper part.

Actually, put the inlets up top like an RS200 (but of course use NACA ducts):

I'm picturing something sort of horn-shaped, that would have a horizontal slot that overhangs the drip rail and 'eats' the vortex that is trying to form as the air spills over the drip rail. But, yeah...

And that exit duct? Coanda Nozzle.

Back in the 50s, someone raced a Porsche that had the exhaust pipe on each side in the center of a high-bypass duct that pulled air through the engine. No mechanical fan. [citation needed]

This is the one I'd choose, but it might be worth the effort of smoothing out those interior corners that develop between the rear fenders and the body sides. Think about building a custom rear bumper?

I understand about filleting, but I also consider buildability. These renderings are only approximate. I can hold the parts up against each other, but I can't Boolean AND them together—yet. The lighting and rendering comes easy; the modelling, not so much.

The next round will have the upper part shortened forward to where the bike rack sits now. In fact if I chop the rack about 2—3" it would work perfectly. The lower part will extend back about one foot (down from 18"), and be curved to the contour of the stock rear bumper. Two 1/8"x3"x16" steel straps would relocate the bumper and carry any diffuser parts required.

It would be neat to find a ratty Bug body , hack it off where your boat tail begins, and build a new rear end with perfect curvature.

Last thing.
If you're doing this version, use some '63 Thunderbird taillights to make it look like a rocket ship. And add NASA logos to the side

Always one of my favorites. I wonder what they weigh.

Maybe something about the size of a 5-gallon bucket lined with red LEDs, with a soap bubble generator fed by pumped engine cooling air?

[arcosine]

Wood can be formed by softening in boiling water first, then bend around form and clamp.