PVC bow dome made with a central hub

[Jovankat]

So I came across this prototype dome top hub thingo for sale and I wanted to get everyone's thoughts on this approach to building a dome because it's not something I've seen before (as evidenced by how hard I'm finding describing it.)

Prototype central hub unit that can be used in the construction of a ~12-15 foot diameter PVC pipe based hemispherical dome structure. Overall dimensions of your final dome will vary with length of PVC poles you use, desired ceiling height and diameter.

This auction is for the CENTRAL HUB UNIT ONLY!! All other photos/descriptions are provided only to illustrate the final potential structure; they are not included in this auction.

The central hub unit was custom designed around an extremely durable hard plastic disc. The disc was shaped to accept (12) 1-1/4 inch PVC "docking tubes".

Each 1-1/4 inch PVC docking tube was then attached to the hub with (2) U-bolts with plate washers, 1/4" bolts/washers/nuts, and finally topped with an acorn nut. The unit is approximately 25" in diameter.

There is a ton of hardware on the hub, a bit of engineering overkill, but the final product is extremely functional and rock-solid.

The whole unit was first primed with white "primer for plastic", then white enamel paint and finally a coat of polyurethane, making it impervious to all weather.

Many hours were spent in the concept and creation of this hub, please review the photos carefully to see the design, engineering, finish, and condition. As the hub is a prototype it has been used/tested and therefore has some imperfections, none of which affect its function or overall cool look.

The 1-1/4" docking pipe will accept the 1" PVC poles. The PVC poles are set over rebar which is driven the ground in a circular pattern to set the diameter you desire. Note no additional hub hardware/locking mechanism is necessary as the poles are held in place by tension and overlap with the hub docking tubes. See photos for a completed basic structure which I designed and built with basic tools to test the hub.

This central hub unit is the key element for a portable dome that you complete. It sets up/breaks down and covers easily. It would great for camping, back yard fun, greenhouse, festivals, Burning Man!

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I'm wondering;

1. How secure/wind resistant would this bow design be do you think? The geometry seems like it would have a whole lot more flex than a geodesic or even star design both because of the shape and how long the pieces are. But then that works ok with monkey huts so maybe it would be ok here too? Also according to GreyCoyote in this thread a wigwam is stronger than a star dome, where does the bow fit in the hierarchy of dome designs?

2. Is it just me or does the hardware on that hub look like serious overkill? The stuff on the PVC side all looks reasonable but the metal hardware on the back is a bit insane, why would all those little rectangular plates be necessary? Would screwing into the base suffice rather than bolting through with nuts on the other side?

3. Does anyone recognise what the base disk thingy is? I'm guessing it's custom made but a custom plastic moulded disk doesn't seem necessary for this basic idea. I imagine that you could just use a disk of simple ply with the spokes screwed in with roofing screws through the bevelled end in the centre like these ones, then put triangular chocs of wood in between each of the spokes to stop them rotating on the central pivot point of the roofing screw. And then to stop the outer end of the spokes pulling away from the disk once under tension you could screw a matching wooden disk over the spokes to sandwich it all together.

This isn't something I'm actually thinking of buying or building my own version of (not this year anyway) but it's intrigued me and I'd like to hear every one else's thoughts and to see if my guesses and assumptions are reasonable.

Oh! For bonus points what do you think of using the disk idea but having two of them with the spokes on an angle, one disk with spokes going clockwise and the other going anticlockwise and put together like a double decker sandwich (or a Big Mac)? I imagine the two directions being in different layers would allow the struts going in different directions to pass over each other. To add stability I imagine you could bolt them together at each point that they cross.

As you can probably tell this is a little outside of my usual creation so apologies if this is rambly or doesn't use the right words.

[theCryptofishist]

If this doesn't already have a name, I nominate "spiderdome".

[Jovankat]

Aaand now it's creepy and I don't want to hang out under a giant spider. Problem solved, I'll stick with the yurt. Thanks Fishy!

[theCryptofishist]

I aim to please.


(I thought Australians dealt with giant bugs on a daily basis. Epic arthropod battle before breakfast. I have obviously been misinformed. YouTube--once again you disappoint me.)

[FIGJAM]

No Fishy.

The snakes ate them all.

[Ratty]

It looks like my 1960's pop-up tent. It has 6 heavy fiberglass poles and requires 6 tie downs. My tent is too wiggly to bring to the burn.

[theCryptofishist]

Can your tent do the shimmy?

[Jovankat]

Fishy I used to live by myself in an apartment that had a fig tree older than colonisation overhanging it's courtyard that was home to a family of huntsmans, the really big hairy fuckers who have probably seen videos of. I had to deal with them on a roughly weekly basis, always as I was about to go to bed or to work. It was horrible. I actually started sleeping with the light on and developed crazy "seeing things move out of the corner of my eye" skills. I also became hyper aware of spider shapes in amongst other stuff where before I wouldn't have noticed them. It was TRAUMATIC.

[FIGJAM]

[media]

[Popeye]

1. Depending on height/ type of shade cloth/ etc. it should be fairly secure and wind resistant. Depending on the length of the "docking tubes" you might have trouble with the 1" poles slipping out but there are some fairly standard solutions for that.
2. Those little metal plates come with the U bolts and act as washers.
3. I wouldn't use regular plywood, maybe marine grade and definitely not screws into plywood- to much torque.

I wonder if someone has used this arangement as a base for a parachute?

[FossaFerox]

So I came across this prototype dome top hub thingo
. . .
2. Is it just me or does the hardware on that hub look like serious overkill?

There is no such thing as overkill on the playa, only prudence.

[Sunbeam56]

No actual experience - just thinkin'...
I prefer belt AND suspenders.
If the top hub is too heavy, it will bend the spokes down. They are already flexed, so your failure is a snap about 2/3 up the spoke from the ground.
I dont like the stakes inserted in the spoke tubes by itself.
Even if you run a bolt into the spoke to tie into the stakez - i would still run a chain around the base to keep all the spokes confined.
If you dont have the spokes confined - you just have an umbrella shape.
What makez it dome-ish is the smaller footprint.
Keep it tight !!!

[trilobyte]

My experience with campmates who've tried to build domes with PVC (two different people have tried over the years) is that they don't work well. The first one didn't last an hour before the PVC got so melty and warpy that it couldn't support it's own weight, the other didn't last a day. Your mileage may vary, but my impression is that Chromey's monkeyhut design works because it's a magical slice of brilliance, not because PVC is a wonder material that can be used to build any kind of structure on the playa.

[Popeye]

Sunbeam:

I dont like the stakes inserted in the spoke tubes by itself.

You're talking about the 1" going into the hub? I agree, maybe use some kind of innertube/ bungy ball arangement to keep them from popping out? And the same thing on the ground to hold the ribs onto the rebar?

I think of it as rotated ribs from a monkey hut rather than a dome. A dome gets its strength from the cross support of the different elements. You will never have the strength of a dome in this umbrella shape but do you really need that much strength if you are just building a shade structure?