Flooded frame or sealed?

[Stargazerwa]

I am in the design phase of my rov. I am planning on using 3/4" class 200 pvc and assume it should be fine down to 60-75'... Thoughts? I am considering sealing a portion of my frame for buoyancy thereby avoiding large floats. My preliminary calculations are positive. Has anyone else done this?

I found these, but they aren't for my size pipe and they are not at Lowe of course:

http://www.aquaticeco.com/subcategories ... -Inner-Cap

Has anyone plugged off tubing with epoxy or by some other means to get this same effect? My other thought is to use the 3/4 class 200 and seal it all using zip ties and clamps for mounting motors etc.

[Rover]

Both methods, Sealed and flooded are commonly used. The two ROV's I have built were watertight. The third one I am building is also water tight. Each method has it's pros and con's, Depending on the size of the ROV, a sealed hull, can add a lot of bouyancy. Not sure if the inner caps can handle a lot of pressure. They are connly used as a dust cap. At 66 feet you will have approx 30psi of water pressure on your hull, a pressure PVC can handle. A common method of sealing your PVC tube, is to use PVC end caps (glued or threaded on) the tube you want to seal.

Good luck with your build, let us know how it goes.

Rover

[Stargazerwa]

I have decided not to use the inner plugs like those in the link I posted. I am using several of these snap on tee's that are meant to be glued to an existing pipe and then drilled out.

My concern that I need to test is if I make the frame sealed and close to neutral buoyancy will it end up being very stable? I may add some additional floatation at the top and weight at the bottom to keep it stable.

[Zaibach]

Either is probably fine, personally I'm leaning towards flooded. Just to attempt to condense the potential points of failure in my first build from every connection in my frame down to a couple endcaps.

[Billrose]

Reading about this subject of 'Flooded' or 'Sealed'

I have a differing point of view.

1. A flooded tube frame will add. 'Mass' not weight to the rov in water. That is, it will become 'heavy' with the tube frame filled with water. Making it little more difficult for the thrusters to push and pull the rov around.

2. A Sealed frame will ad buoyancy to the rov. But perhaps too much! Thus the rov will not be able to dive!

3. Think about the depth of your Rov diving. How far are you going to go? I think tube frames are good for shallow diving. But if you are going deep..down..into the depths. Then re-think your 'Frame' / 'Shell' / 'Hull'. Something a bit stronger.

Regards. I will post some more on this later.

[Billrose]

These two Rov's have two different kinds of 'Hull' & Frame.

This has a crash metal frame

rov-11.jpg (37.42 KiB) Viewed 4651 times

This is a hull rov.

towable1.png (258.67 KiB) Viewed 4651 times

[Billrose]

In my own experience for a plastic tube frame. I would go for a top sealed tube, for buoyancy.

Then a bottom flooded tube for stability in the water.

But this sort of combination is only good for shallow diving.

[Stargazerwa]

For the rov I am building now, my calculations show that I can achieve a slightly positive buoyancy by sealing most of the frame. I am using 3/4 class 200 pvc which is thinner walled than what others are using, it's made to handle internal pressures of 200 psi.. I am planning on diving no deeper then say 60'. My concern is that my bounancy is along the top, bottom sides etc. and will I have a problem keeping it horizontal?

My goal was to reduce the mass so that my thrust to weight ratio would be more favorable. I realize this gives me more joints for potential leaks, but am confident that I can glue good joints. I do have four 180 degree curved members that I bent using hot sand and a jig. Potentially these could deform or crush if I get too deep.

I may just finish the build and see how it does. I can always drill holes in the frame and add buoyancy tubes along the top.

[Stargazerwa]

Dry fitted the ROV today and it was more buoyant than I calculated. I will be making one of the cross pieces wet. Easy to do when I am using snap on tees.

The good news was that it was plenty stable! I poured some lead sticks to glue to the inside of the lower pipes and was surprised how much weight I needed. Anyway it's looking good, can't wait to finish it