half sphere build for Little Prince

Doug Lowthian

Active Member
Doing Little Prince. I need planets. I'd like to use a technique I have seen in many productions on-line.
It consists of a half sphere, flat side down, decorated and painted to look like a planet. Actors can walk up on top of it.
Looking and about 2.5-3.5 feet in diameter. Any ideas how to frame and build such a thing?

Thanks in advance!
 
Doing Little Prince. I need planets. I'd like to use a technique I have seen in many productions on-line.
It consists of a half sphere, flat side down, decorated and painted to look like a planet. Actors can walk up on top of it.
Looking and about 2.5-3.5 feet in diameter. Any ideas how to frame and build such a thing?

Thanks in advance!
@Doug Lowthian Since none of CB's scenic construction gurus have hastened to your aid, YET, I'll tell you one of the Stratford Festival's approach's although I'm not seriously suggesting it's the right / best method for you in your situation.
In Stratford's main prop shop, Frank Holte would often purchase 4' x 8' sheets of white styrofoam in thicknesses up to 24" then cut, glue and laminate them as necessary.
One specific example springs to mind:
One 4 by 8 by 2 foot sheet was cut in half and laminated to become a 4 by 4 by 4 foot cube.
1" dowels approximately 3' long were lathed and tapered at one end.
The surface deemed to become the bottom had lines drawn diagonally from corner to corner to indicate the center point.
Measurements were taken and marks made approximately 1' from the center point on each of the four radials / diagonal lines.
Pilot holes, perhaps 1/4" in diameter were bored on the four marks with an 18 or 24" bit.
Glue was glued was poured into the pilot holes and the 1" dowels pounded into each of the four holes with a mallet until they were flush with the surface deemed to become the bottom.
While the glue was drying, an approximately 30" square of 3/4 inch ply was cut, center lines added and #8 or #10 pilot holes drilled through the ply to precisely align with the centers of the four dowels.
With the glue thoroughly dry, 3" or 4" long wood screws passed through their clearance holes in the 3/4" ply leaving 2.25" to 3.5" of thread exposed to securely grip the dowels; pilot holes were likely pre-drilled into the dowels to accept the wood screws.
AND NOW you'll think I'm totally daft if you're not thinking so already.
If you're familiar with wood and / metal lathes, you'll know materials are normally chucked in a 3 or 4 jawed chuck and often stabilized by a pilot hole in the end / side opposite the chuck by a live or dead center; you'll also know face plates can often be located on the opposite end of the shaft rotating the primary chuck. With this face plate now outside the lathe's bed, materials far exceeding the lathe's normal diameter limitations can be spun and machined.
HERE'S WHERE IT GETS EVEN WEIRDER:
When lathing a 4' cube of Styrofoam, you'll want to begin at a VERY slow rotation.
In Stratford's main prop shop they have, or at least had, a basic (Plane Jane) wood lathe, nothing fancy just a basic bare bones machine.
The lathe's headstock was securely bolted atop an approximately 30" high wooden base positioning the chuck's rotational center line approximately 40 - 42" above the shop's floor.
Frank Holte had a V-belt pulley fitted to permit the lathe to powered and spun by a long V-belt looping around the pulley AND the tire-less rear wheel of a an old bike mounted on a base such that a minor props minion could sit on the bike, with her / his back to the lathe and pedal at any speed decreed by the person operating the lathe. Accompanying the lathe was a shop fabricated steady-rest which the operator could position, stand on the bottom of for ballast, then select the weapon of her / his choice as their tool begin lathing away. Huge amounts of Styro-foam turnings littered the floor often landing on plastic drop cloths making for easier collection and dumping into large rubber garbage pails.
You had to see a 4' cube of white styro being lathed into a 4' tall by 47 (ish) " diameter flower pot with its innards lathed out, four legs /feet added to its smaller diameter lower end and all covered with an assortment of fabrics glued in place then sanded to perfection prior to painting to look like a large, ornate, planter suitable for the veranda of a stately mansion in a time long before me. The finished product was considerably shallower within than any real planter of its size and when the piece was TOTALLY finished it'd pass for real while your pushing it on a dolly from off-stage storage to back stage. The finished piece looked THAT good, even from that close, until you lifted it off its transit dolly and instantly realized it was NOWHERE near as heavy as it looked. The finished pot was painted to appear weathered and aged from decades of service on the veranda of its mansion.
@Doug Lowthian I suspect you could do something similar but I'm confident many of our scenic / props gurus will be along posting far better options, if they haven't all ready while I've been typing.
Toodleoo!
Ron Hebbard
 
I'm also no scenic guru. That said, if you have what I assume to be plenty of money and some strong stagehands (if these need to be moved about during the show), you could maybe use these stainless steel playground dome climber things. They're clearly rated to take the load of people clambering over them. As a much cheaper alternative, maybe you could find an old disused satellite dish? I doubt many people would notice if your planets are parabolic rather than hemispherical. If the dish can't be used on its own, it would seem to me to make a nice mold for laying up fiberglass or something similar.

If I had to construct something like this, I'd probably either work out a geodesic shape and cut lots of triangles of plywood and attach them to appropriate framework (which sounds like a lot of persnickety work), or else construct some simple wooden arc-shaped trusses, arrange them radially around the central axis of the planet, connect them with circumferential stringers, and "floor" the whole with plywood gores of sufficient thinness to be bent into the required shape. If the flooring seemed insufficiently sturdy one way of strengthening and stiffening it would be to add a second floor layer underneath with a gap between the layers and then fill the gap with low-expansion spray foam. That would make a composite structure, a wood-foam-wood sandwich, which is much stronger and stiffer. In either case some surface finishing and/or forming would presumably be required to keep it from being obviously faceted.
 
Is it a true half sphere - so 3' diameter is 18" tall? Or more truncated?

And is some variation in size necessary? Not just one mold per se? And how many?

For 30" half spheres, I think I would experiment with a sheet of 1/4' plywood, cut maybe 3" wide X 48" across sheet, and bend the easy way, maybe with an 18" post. Cover with muslin and glue. Probably no more the 3-5" gaps at the edge. Thats 8 or so 3" strips with 3'' gaps if my quick math isn't off. I don't think it would be too squishy. If it worked for 30", I'd have to think about best way to go to 42".

More of a truncated dome than a half sphere would be easier.
 
Being a sheet goods kind of guy and working out of 3/4 of a 2 car garage, I'd cut 4 1/2" ply "half" circles. By half, I mean a radius that gets me enough height at the peak to give the impression that it's an actual half sphere but isn't as steep a climb for the actors. Two of the arcs will get slots cut so they nest as a X, another 2 will be cut in half to fit in the quarters. This form would be screwed and glued to a 1/2" ply circle. The resulting form would then be skinned in 1/4" ply wedges or bendy board. If I had more than a few, I'd consider pulling a mold of the first and making the rest out of fiberglass.

Michael
 
Could you do a 1/4 sphere and the actors walk up from behind it on a short ramp or stairs? The Least expensive manner I could see building a walkable half sphere like that would be a bluefoam base and a covering of either luan, ply or fiberglass. Also a full half spherewould be extremely difficult to climb; 3.5' in diameter would be 3.5' in height in just 1.75'. perhaps 3.5' in Diameter by 1.5' in height if you are going full circumference.
 
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Could you do a 1/4 sphere and the actors walk up from behind it on a short ramp or stairs? The Least expensive manner I could see building a walkable half sphere like that would be a bluefoam base and a covering of either luan, ply or fiberglass. Also a full half spherewould be extremely difficult to climb; 3.5' in diameter would be 3.5' in height in just 1.75'. perhaps 3.5' in Diameter by 1.5' in height if you are going full circumference.
From an actor safety standpoint I like the quarter sphere with an upstage platform/steps.
 

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