New a6xxx housing from Meikon

[CanadaDan]

That... does not make sense. The camera inside the housing does not change its displacement - only the mass, and the tiny amount of air that it displaces out of the housing is well below the margin of error for measurement. Are you sure you don't have pulley friction throwing off your measurements?

I guess I'll buy a set of tire balancing adhesive weights, plus get an extra set of aluminium arms when I order the housing. It's hard to believe that it is that much more buoyant than the old version though.

I wondered that too so I measured twice... but given the narrowness of the can the string WAS running against the housing.

The housing is bigger than the old one... and that dry dome is a massive volume of air (its a larger diameter than the old wet one too).

 

[Barmaglot]

Yeah, but it doesn't add up, unless I'm misinterpreting your post something horrible. If your housing with camera is +1800g, then you add 4x -80g arms (-320g) and half a dozen clamps (rounding up to -500g) and a tray (probably -300g or thereabouts, so -800g total) and a -40g strobe, then you should still be about 1kg positive before you add the lights and floats - adding your 700g of floats, you come back to ~1.7kg positive, but the two small lights and paralenz with mount somehow make that neutral? What are they made of, solid tungsten?
I'm most thoroughly confused now. I guess the safest option would be to pick up a set of adhesive weights, plus a pair of aluminium arms - this way, if the housing is really that buoyant, I will switch the 2x300g floats for non-float arms and maybe add weights as needed, and if it's not, I'll keep the float arms and use the weights to dial in the exact buoyancy.

 

[CanadaDan]

UW weights are always different... sometimes surprisingly so. I’m doing a pool dive Wednesday evening NA Central time. I’ll report back then to confirm but as near as I can tell the rig as now pictured is near neutral in fresh water.

 

[Barmaglot]

There is no voodoo to it, just weight and displacement... assuming that those are the jumbo (181g lift) floats you have mounted there, and the rig is more or less neutral with them, this means it's 700g negative without - my lights are probably somewhat heavier than yours (-330g each underwater), so even with the float arms (supposedly 300±50g each) I'll still be somewhat negative, which couldn't happen if the housing is over 2kg positive. Oh well - I'll run my own tests once it gets here and see what's what; worst comes to worst, I'll get extra floats and/or weights when I get to Thailand.

 

[CanadaDan]

So I simplified the process. I took the housing alone with camera and battery inside, ziptied a 5lb lead to it and weighed it in and out of the water. No pulleys, no contact with the sides or the bottom of the tank, should be right.

Out 4450g, in 1090g. Gross difference is 3360g. The lead itself accounts for 330g of that when placed in the water.
The positive buoyancy of the housing is therefore 3030g. It's a lot but that dome is huge, dry and the a6xxx housing is larger than the original Meikon a6000 version.

FWIW my 5120g dry weight rig as a whole is 270g negative with the strobe, video cam, lights etc and no floats. Add in the 4 large Stix floats with combined 323g of lift it will be a touch positive.

It doesn't float nicely though. Wants to spin dome up all the time. I may add the float arms back into the equation and attach some lead to the bottom to make it more stable.

Sorry for the confusion... this is all being done with garbage cans for tanks, luggage scales for weighing and some DIY methodology

 

[Barmaglot]

Last I measured, my rig was a bit lighter than yours (about 4.8kg in air), but that was with the older housing, wet dome and 16-50mm lens - 10-18mm is a bit heavier, and the new housing is probably... more than a bit. I can't fault your methodology, but it's hard to wrap my head around a tray, aluminium arms, two small lights and an action camera having over 3kg of negative buoyancy. Is your tray particularly heavy, maybe made out of steel rather than aluminium? In any case, I ordered a box of these - if my rig ends up positive, I'll glue them to the back of the dome. Quarter-ounce increments should make dialing in precise buoyancy fairly easy, and it will help with the trim too.

 

[cruisekingkris]

Any Discount codes floating out there for Seafrogs Website?

 

[Barmaglot]

Never seen one. Most of their housings can be ordered via various Aliexpress sellers at a substantial discount, but only after they've been on the market for a good long while - the fixed-port A6xxx housing that came out about 8 months ago is still selling at full price, and the new interchangeable-port one can only be obtained via meikon.com.hk and seafrogs.com.hk.

 

[CanadaDan]

No test and trim session last night... apparently the pool manager has instituted a no camera policy and it includes underwater rigs (kinda hard to sneak one around). Will have to wait until the shop books into a different pool without the policy.

 

[Barmaglot]

Dammit! Got home after a three week work trip, went to Meikon site to pull the trigger on the new housing and whoops - the white ones are sold out. Black is still available, but the white one is so pretty... kinda torn between waiting for new white stock, which may or may not become available in the 25 days (minus 3-4 days for shipping) before I fly out, and getting a black one right now, before it sells out too and I miss the boat altogether.