The Bathysphere - Does anyone have tips on building large hollow spheres/hemispheres on a budget?

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mrcarkeys42

Active Member
More of a small set than a prop. I've been reading a lot about Otis Barton and William Beebe's Bathysphere and was considering depicting it in a student film. The only issue is how to construct such a thing!

bathysphere 2.jpg


The design itself is very simple and the exterior will be easy enough to make via miniature, but the interior is where I am left scratching my head. How do you build a small spherical room on a budget? I've been looking into large spheres and hemispheres that you can buy in various materials but once you start getting to the size I need (5') they quickly become very expensive, at least by student film standards.

Metal spheres/domes

Plastic spheres/domes

Fiberglass spheres

polystyrene spheres



Of these I think getting plastic hemispheres might be the best option, if I can afford it (still need to get a quote for 5' diameter ) but honestly I am dubious about the structural integrity of any of these if actors are going to be thrashing about inside. Metal would make the most sense structurally but would be the hardest for me to work with, super heavy at that size, and way too expensive. I'm not experienced with fiberglass and thought that might be a good choice but the largest option is only 4' and even that is over two grand.

I found these kits for framing domed ceilings, and I think something along these lines might be the way to go... But I'm out of my skill set here, and ill need to line the inside with something sturdier than drywall. Maybe a thicker styrene plastic? not sure what material would be best for this sort of thing.


My school also has a 4'x4' CNC machine, so maybe it would be possible to create the framing myself, but again I'm out of my element.

If anyone has experience building spheres and can give tips/advice, let me know!

bathysphere 1.jpg


bathysphere 3.jpg


bathysphere 4.jpg
 
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TazMan2000

Master Member
My idea would be a lot of work, but definitely cheaper than a large plastic hemisphere.
Get one of those novelty/toy large beach balls, and coat it in paper mache. Once dry, paint with fiberglass resin, and then overcoat with fiberglass, or burlap. Filler will be needed and a lot of sanding, but you should achieve a cast iron appearance if done correctly.
The previous suggestion would be for an exterior set. An interior set would involve slicing the sphere in two, or cutting several holes to get the proper camera angles...usually those holes can be hidden by interior components of the bathysphere.

TazMan2000
 

mrcarkeys42

Active Member
My idea would be a lot of work, but definitely cheaper than a large plastic hemisphere.
Get one of those novelty/toy large beach balls, and coat it in paper mache. Once dry, paint with fiberglass resin, and then overcoat with fiberglass, or burlap. Filler will be needed and a lot of sanding, but you should achieve a cast iron appearance if done correctly.
The previous suggestion would be for an exterior set. An interior set would involve slicing the sphere in two, or cutting several holes to get the proper camera angles...usually those holes can be hidden by interior components of the bathysphere.

TazMan2000
Thanks Ill look into this! I've never really worked with fiberglass before though, how strong do you think something like this would be? strong enough for actors to be inside without noticeably effecting the inner surface?

Also looking at beach balls now... Ill check other websites, but is frustrating how they seem to jump from 4' to 8' with no in-between haha

 

TazMan2000

Master Member
Thanks Ill look into this! I've never really worked with fiberglass before though, how strong do you think something like this would be? strong enough for actors to be inside without noticeably effecting the inner surface?

Also looking at beach balls now... Ill check other websites, but is frustrating how they seem to jump from 4' to 8' with no in-between haha


Fiberglass can be incredibly strong provided it is applied correctly without voids. Even a single layer would be strong enough for the walls, but you may need at least 2 layers for the floor. It's not really that hard to do, but it can me messy and stinky.

Widen your search to "inflatable ball 5 feet" and you may have better luck.

If you build it correctly, even a paper mache ball has enough strength to be hoisted by a chain, but of course, wouldn't be strong enough to support an actor.. This might be a good start. Coating with a layer of resin right over the paper mache will make things even stronger. Plenty of videos on the web to show you how to do fiberglass. You don't necessarily need to use the fiber cloth. Almost anything will do, but the fiber cloth is specifically made to be one of the strongest materials for general application.

TazMan2000
 

mrcarkeys42

Active Member
Fiberglass can be incredibly strong provided it is applied correctly without voids. Even a single layer would be strong enough for the walls, but you may need at least 2 layers for the floor. It's not really that hard to do, but it can me messy and stinky.

Widen your search to "inflatable ball 5 feet" and you may have better luck.

If you build it correctly, even a paper mache ball has enough strength to be hoisted by a chain, but of course, wouldn't be strong enough to support an actor.. This might be a good start. Coating with a layer of resin right over the paper mache will make things even stronger. Plenty of videos on the web to show you how to do fiberglass. You don't necessarily need to use the fiber cloth. Almost anything will do, but the fiber cloth is specifically made to be one of the strongest materials for general application.

TazMan2000

Thank you! I'm going to start researching fiberglass tonight. I think the limiting factor with this method would be the amount of work that will need to go into it and also finding an appropriate place to do something like that at this size. I have zero concept of how much material it would take and how much those materials cost, how expensive do you think something of this size would be?


Also! Alternatively I just had the thought to look into spherical water/septic tanks, which I'm starting to think might be the best choice as far as buying an existing sphere goes, making one myself may still ultimately be the best option. I can get this one for under a grand, its probably much more durable than an acrylic sphere though I'm assuming the material its made out of will be harder to work with. It also already has a stable bottom and a way to access the inside

 

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PoopaPapaPalps

Master Member
RPF PREMIUM MEMBER
As far as interiors go, I think you wouldn't even need to go as far as building half a sphere. You could get away with building a quarter of the thing. It's a tight and confined space, you only need to give the impression that it's like that in reality. If it were me, I would just build a small panel, a portion of the sphere and just film it close and in the dark.
 

TazMan2000

Master Member
Thank you! I'm going to start researching fiberglass tonight. I think the limiting factor with this method would be the amount of work that will need to go into it and also finding an appropriate place to do something like that at this size. I have zero concept of how much material it would take and how much those materials cost, how expensive do you think something of this size would be?


Also! Alternatively I just had the thought to look into spherical water/septic tanks, which I'm starting to think might be the best choice as far as buying an existing sphere goes, making one myself may still ultimately be the best option. I can get this one for under a grand, its probably much more durable than an acrylic sphere though I'm assuming the material its made out of will be harder to work with. It also already has a stable bottom and a way to access the inside


Considering you have no experience with fiberglass and possibly the mistakes you will make on your first attempt, it would probably be even money if you went with the septic tank. Just make sure it's not a used one. :lol:

With half a sphere, you would have the ease of less materials and a much easier way to film, however, as I look at the layout of the bathysphere, there is equipment mounted on all sides and you would have limited angles for filming. However, you are going to have your hands full in trying to find good angles in such a cramped compartment. However, it might add to the drama by showing how tiny the compartment is when an actor is stuffed inside it.

You may want to use my idea of paper mache for a full scale prop if you need one. Perhaps even a miniature.

TazMan2000
 

Borg69

Active Member
I keep picturing something like Jeannie’s bottle prop/set.
 

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mrcarkeys42

Active Member
Great project mrcarkeys42 !
Personally i found this video particularly instructive as a beginner using fibreglass
best of luck with the film (y)
Thanks David3! If you have any other good fiberglass videos for beginners let me know!

As far as interiors go, I think you wouldn't even need to go as far as building half a sphere. You could get away with building a quarter of the thing. It's a tight and confined space, you only need to give the impression that it's like that in reality. If it were me, I would just build a small panel, a portion of the sphere and just film it close and in the dark.
This is a good point and I think we could definitely shoot it that way, but I also think the more of it we have the more flexible we can be. The script is still being written so I'm just trying to see what's possible (the final script may not even depict the bathysphere at all!) once the script is finished and we know what shots are wanted we can see what we can get away with. I think all close-ups would be an easy way to do it and would even be effective given how confined of a space it is, but at the same time I think that at least half a sphere would allow for wider shots of the inside such as this illustration:

otis and will 1.png


with half or even three quarters of the sphere you could push it even further and almost go with cutaway shots like this:

otis and will 2.png


Really its going to depend on what the director and dp want, but if feasible id like to build as much of it as I can!

Considering you have no experience with fiberglass and possibly the mistakes you will make on your first attempt, it would probably be even money if you went with the septic tank. Just make sure it's not a used one. :lol:

With half a sphere, you would have the ease of less materials and a much easier way to film, however, as I look at the layout of the bathysphere, there is equipment mounted on all sides and you would have limited angles for filming. However, you are going to have your hands full in trying to find good angles in such a cramped compartment. However, it might add to the drama by showing how tiny the compartment is when an actor is stuffed inside it.

You may want to use my idea of paper mache for a full scale prop if you need one. Perhaps even a miniature.

TazMan2000
I like the septic tank idea (definitely so long as its new haha) but my main concerns would be shipping price, material (made from hdpe which is very hard to paint and glue) and also its structural integrity after cutting pieces out of it. if i cut it down the middle to get two hemispheres I'm not sure if it will maintain its round shape. Hopefully I can find one locally to check out in person first!
I keep picturing something like Jeannie’s bottle prop/set.
pretty much exactly how id want it cut out for shooting! except even smaller lol



Apparently spherical propane tanks are a thing as well, though I cant seem to find any readily available. Probably wouldn't be able to work with one anyway as I have no welding or metal working experience, but even so I wish i could find something like this locally! This one is the right size and sold for less than 300 dollars! slap a few windows on and it would be a respectable recreation haha

propane tank 2.png
 

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