Help with housing buoyancy

Good day all,

Been struggling with buoyancy and leveling of my camera since adding on the extended viewfinder. So far this is what I have come up with. Would love any other recommendations or tips on attaching buoyancy or attaching my current buoyancy better. I have put a few small tire weights on the bottom of the dome. It is still back heavy and of course rotates to the right due to the handle. I am a big fan of one handle unless using strobes, to keep the system small.

Thanks!

Hi longbord1

Have you calculated how much extra buoyancy you need? It might be worth doing the dipping-in-water-on-the-end-of-luggage-scales test to see. That would then give you an idea of the scale of what you are trying to achieve.

My suggestion would be to attach an arm horizontally across the camera housing, held by a clamp, with Stix foam on it. You should be able to get an 8" or 9" arm which will hold 2.5 or 3 pieces of Stix. 2.5 pieces will give you 425gms (2.5 x 181gms) of additional buoyancy; 3 pieces 3x 181gms.

On the rotation of the domeport, yeah, tyre weights are the way to go, I'd suggest.

Hey TimG!

I definitely need to do the luggage thing. I bought one, just haven't gotten around to it.

The only problem with the arms is, I want to keep this rig as streamlined as possible. I often use it while freediving and attach it to my weight belt when I need my hands free. So an arm wasn't something I was interested in. I guess I could attach more foam to the free space on the top left of my housing. Any advice on attaching foam? Specific Glue, velcro?

Ahhh, right, I did wonder, given your photo, if you were free-diving. 

Hmm.... you could velcro Stix blocks onto the housing - perhaps using an epoxy to make sure the velcro strips actually stay on the housing and the Stix. But not a very elegant solution and I'm not entirely sure the Stix would stay in place all the time whilst free-diving. 

Or maybe you could drill Stix and bolt them on to the underside of the housing tray? You'd lose a bit of buoyancy of course but not a huge amount.

How do you attach your camera to your weight belt? Do you use a lanyard or the current arm just tucked in? If the latter, would adding an additional, horizontal arm make that much difference?

A Stix-like buoyancy collar around the lens port?

As I set out, it'd be worth knowing how much additional buoyancy you need to add then at least you can visualise what is involved.

Thanks for the advice! I actually attach it to a "land based" Quick release belt mount! It's more bulk and hydrodynamics I'm worried about, as it already slows me down substantially. I will get back to you on the buoyancy measurement asap. But seems like very strong velcro or some other quick release attachment style would be good.

Thanks for the advice

What port are you using? Are you sure it is not front floaty instead of back heavy? Maybe the ikelite port trim arm is what you're looking for?

Whatever solution you come up with, it will probably work better with weight at the bottom and flotation at the top as it gets away from the tendency of the housing to want to flip over.

 I would also say that the cross sectional area and therefore the drag of the whatever buoyancy you use will be the same be it Stix floats or float arms as buoyancy depends on displaced volume for a given weight.    The only time it wouldn't is if you could tuck the floats in behind the cross section of the housing.  You might for example be able to use a single arm about 50-60mm in diameter across the front of the housing, placing it on top of the dome extension so it doesn't add as much cross sectional area. Or as you report it is back heavy sitting above the viewfinder neck.

I would also think a single float-arm may cause less drag than little bits of foam stuck all over the place.  Also on the point of streamlining weights are much more compact than floats - so the question is - do you want it balanced or balanced and neutral and how close to neutral do you want to get? 

If balanced is you main aim - try to do it all with lead.  If you also want it neutral add the minimum lead needed to balance and place it above the centre of bouyancy so it doesn't induce twist.

I would suggest playing with it in a tank to get the front back balance right., then weighing it. to work out overall flotation needed. 

If you get back with weight of the balanced housing this should point you the direction of an optimal solution.