Trying to figure out how to waterproof an AUV hull

[wcmartin]

Hi, I'm relatively new to designing underwater robots but I'm currently working on a project to implement a unique AUV.  However, I've hit a bit of a snag with creating the waterproof hull.  I am hoping to have one primary chamber (like a cylinder) on the AUV that can be taken apart at the middle.  So far I have constructed mold plugs for the shape I want and am planning on using fiberglass to create a hull from these. 
My issue is that I have no idea how to connect the two halves (essentially two halves of a cylinder). 

In my head I was hoping to have an o-ring seal the two halves, but to do this I imagine I need some sort of threading between the two halves.  I don't think I can really do that with fiberglass (or can I?) but is there something I could add/do that would allow this.  I had the idea of fiberglassing some sort of o-ringed coupling to the two parts but I have no idea where to find such a thing.  That also seems like it might be a bulky and clumsy solution.

Does anyone have a nice way to connect the two halves so that they are waterproof and can be taken apart later?

Thanks so much for your help! 

[corrado33]

How you waterproof it really depends on how deep you want it to go.  The deeper you go, the better it has to be waterproofed. 

Just look at waterproof containers.  You should be able to get a lot of ideas from them. 

[Soeren]

Hi,

If it's OK to have clasps on the outside, 3 or more of these

or similar would be my choice, together with a simple gasket.
O rings are comparatively expensive, especially in larger diameters and they need a carefully machined groove. A simple gasket can be made from any kind of "rubber" that'll handle the environment it's destined for - perhaps just cut one from an inner tube.

You can also make a gasket mounted on one of the mating surfaces, by smearing a generous amount of semi-fluid RTV silicone on it and resting it a few mm above something non-sticky, like Teflon baking paper or the carrier paper for self adhesive labels. You just need some way of holding the body that takes the gasket above eg. a table, at the distance that gives the correct thickness.