Achieving Large Depths

[AHarris]

Not sure how ridiculous this sounds, but just going to throw it out there:

If you wanted to achieve deep depths, without using expensive heavily enforced pipe e.t.c. could you just eliminate all air and then use a swimming float for buoyancy?

By this I mean, could you fill the camera housing with a clear resin (may be impractical to get all the bubbles out but give me a chance) and then fill the main housing with potting compound, so you basically just create a heavy brick.
Then, using an ordinary swimming float or polystyrene or similar create buoyancy.

The theory is that since you no longer have any air but still have the buoyancy you could go to much higher depths without the worry of pressure?
I know that some components can't be potted because they have mechanical parts and equally some shouldn't because they have a chance of overheating but would this be possible? Or would the floats not survive higher than average pressures?
I presume they would act like marshmallows in a vacuum (expand and then go back to normal size as it becomes less of a vacuum.

Thanks, just curious.

[Sterno]

Using acrylic resin to "pot" a camera is relatively common practice, as is using oil to fill electronics housings. The problem with your idea lies with the foam; regular eps foam compresses at depth, so the deeper you go the less flotation you'll have (it will also absorb water over time). There are "syntactic foam" products available which is what is used in commercial ROV and other deep depth flotation applications, problem is it's horrendously expensive (I priced it out at $27 per lb of buoyancy).

How deep are you thinking about taking an ROV?

[AHarris]

Hi, thanks for the information about the buoyancy.

I haven't actually planned a depth for my ROV but since I am using non pressure rated plastic I shall most likely employ the resin to the camera compartement and then fill the electrical compartement with oil.
I am planning on using polyethylene floats for my buoyancy, but as you have advised me these may loose buoyancy.

The only real way I shall know how well it will work is to go for it, probably testing until it either; looses buoyancy, warps out of shape or amp draw is excessive from the motors.