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Anybody try spray foam to make float arms?


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#1 Lwang

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Posted 20 October 2012 - 09:14 PM

I was looking at ways to make float arms. I see plenty of DIYs here that has marine foam sheets glued together into squarish blocks, plumbing pipes tie-wrapped to the arm or pipe insulation/neoprene foams. I wanted to try the marine foam scheme, but getting my hands on those marine sheet foams seems a bit inconvenient (need large sheet, etc). I was thinking of using the polyurethane spray foam that they use for insulation since they are easily available.

I thought the easiest way is to cut the ends of an 1 liter soda bottle, keeping only the cylindrical section, spray the foam into it, then just drill a hole in the middle and insert it into my arm (I can cut the bottle after spraying the foam and letting it dry so there are less steps).

If I want to make it more fancy, I would get some 2 or 3 inch paper tube (or use the same soda bottle as above), grease the inside, spray the foam into it and slide the solid foam out when dry.

I can use bigger bottle for more buoyancy or small bottle for less.

Anyone tried this before? Will these compress in depth? They seem to be super stiff in the store.

#2 rtrski

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Posted 21 October 2012 - 08:28 AM

I've wondered about that myself (the "Great Stuff"?). They do seem to have a couple different grades, one which claims to remain a little more flexible after curing for around windows and doors and such, and the normal stuff. I think there's also a more environmentally-hardy (e.g. less sealed use) grade.

Personally I'm not sure I'd trust the foam itself to provide enough 'skin' to prevent water ingress. I'd think the way it's made it should result in a closed-cell final construction, but if you were to use the long straw wand and inject it into say a 20-oz soda bottle from the 'bottom up' without cutting the ends off, then just trim excess that spooged out of the neck as it expanded (after it dries, of course), you might have a servicable float you could attach somehow.

If you did try either the cut-the-bottle or greased tube trick, you might want to try hitting the exterior with a layer of fiberglass resin or something for a better final seal. Then again, these would be cheap (as in inexpensive I mean) so replacing after water ingress and abrasion wouldn't be much of an issue, would it?

As an aside - we put in an air-jet tub, which uses basically a big hairdryer type hot air motor to bubble thru the water vs. circulating the water itself (no water 'sits' in the plumbing between uses, getting nasty), and the blower/heater motor was noisy as heck. So I put a trashbag in around the tub (between the tub wall and the constructed tile enclosure) and blew the sprayfoam into it and let it expand, being careful to keep an inlet path for the blower. Not only did it create one heck of a sound dampener, it also insulates around the bottom of the tub and helps keep it hot. That "Great Stuff" is indeed pretty useful....

Edited by rtrski, 21 October 2012 - 08:28 AM.

Current rig: Sony SLT-alpha55 in Ikelite housing, Sigma 105mm f2.8 DC Macro w/ Ike 5505.58 flat port or Sigma 8-16mm f/4.5-5.6 DC HSM behind UWCamStuff custom 5" mini-dome. Dual INON z240 Type IVs triggered with DS51 for TTL mimicry, or DS51 alone with home-made ringflash assy for macro.

 

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#3 Lwang

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Posted 21 October 2012 - 08:39 PM

Using the bottle closed off with the spray foam inside would be the lowest tech way if I was to use the foam, and I would not be able to run the arm thru it. From all I read, they seem to be 'waterproof'. If it retains water, then I might just make more from my soda bottle/cardboard tube molds.

Enclosing it in fiberglass would make this EZ project much more complicated, and it will still not seal the hole where the arm goes thru.

#4 ChrigelKarrer

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Posted 21 October 2012 - 11:21 PM

I tried various things to make floats and ended to buy a 80$ sheet of special closed cell foam; problem solved.
To protect the hard but still not very resistant foam i covered it with epoxy putty bt a wrap of fiberglass would be better.
I cut pieces one wider and 2 smaller to create a U shape where the arm sits inside, all zipped together.
The housing floats perfectly neutral with the heaviest lens/dome combination and if i use the macro lens for example
i just bend some stripes of lead around the handle to get a neutral buoyancy with lighter lens/dome combinations.

The best solution was aluminium drinking bottles but even filled with foam they implode loud 30 meters deep.
PVC piping work better but it is too bulky and the heavy material give only a bit of buoyancy.
Chris

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#5 Lwang

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Posted 23 October 2012 - 06:05 PM

I tried various things to make floats and ended to buy a 80$ sheet of special closed cell foam; problem solved.
To protect the hard but still not very resistant foam i covered it with epoxy putty bt a wrap of fiberglass would be better.
I cut pieces one wider and 2 smaller to create a U shape where the arm sits inside, all zipped together.
The housing floats perfectly neutral with the heaviest lens/dome combination and if i use the macro lens for example
i just bend some stripes of lead around the handle to get a neutral buoyancy with lighter lens/dome combinations.

The best solution was aluminium drinking bottles but even filled with foam they implode loud 30 meters deep.
PVC piping work better but it is too bulky and the heavy material give only a bit of buoyancy.
Chris


So have you also gone down the spray foam route? I could probably make 100 of them from one bootle, so even if they eventually let water in, I could just toss it after a few times.

I was thinking about those alum bottles since I had some around, but if they implode, then that's that. I wonder why they implode so easy, they are cylindrical like submarines.

I never knew how buoyant the PVC pipes were, but I see pix of people using it. I always thought the airspace is quite small inside those pipes, but there are people with their formulas saying it is how much water that is displaced, no matter what it is displaced with.

#6 ChrigelKarrer

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Posted 23 October 2012 - 09:12 PM

I solved the problem with the special closed cell foam for probably deep sea buoys and covered them with epoxy.
Have a look here: http://www.easydive....nt_e.asp?ID=113

Spray Foam:
Spray foam inside a plastic bottle will not work as it crush under pressure

Aluminium bottles:
they implode at approx. 30 Meters, filling them with spray foam will not make them significantly more resistant.
They work fine till 30 Meters!

PVC Pipes
Thick wall high pressure PVC pipes are heavy adding more negative buoyancy to the whole rig and they have a small air space so you need a lot of them.
Low pressure PVC pipes don't work as they implode under pressure as well.

Chris

Nikon D800 - Sigma 15mm - Nikon 105mm Micro VR - Hugyfot Housing - 3 Inon Z-240 strobes - 2x2 8'' ULCS arms

Canon G12 with Patima aluminium housing - Fuji E900 with Ikelite housing
Visit My Costa Rica Website - Visit My Italy Website


#7 rtrski

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Posted 24 October 2012 - 09:33 AM

A couple 'support spokes' or ribs would probably help the crush issue, but getting them in a bottle would be hard. Have to start with a simple tube, add the reinforcements, then cap the ends, and the end caps being flat would be a possible issue still (maybe one end-to-end rod for support in the axial direction).

Port extensions are thickwalled enough not to collapse, so that gives you a minimum wall in some sort of plastic to shoot for.

Edited by rtrski, 24 October 2012 - 09:33 AM.

Current rig: Sony SLT-alpha55 in Ikelite housing, Sigma 105mm f2.8 DC Macro w/ Ike 5505.58 flat port or Sigma 8-16mm f/4.5-5.6 DC HSM behind UWCamStuff custom 5" mini-dome. Dual INON z240 Type IVs triggered with DS51 for TTL mimicry, or DS51 alone with home-made ringflash assy for macro.

 

Topside, unhoused: Sony SLT-alpha99, Sigma 150-500mm + 1.4TC (Saving for Sony 70-400 G2), Sigma 15mm diagonal fish, Sony 24-70mm f2.8 CZ, Tamron 180mm f2.8 Macro...all the gear and nary a clue...