Wetpixel Live: Housing Buoyancy Primer

Adjusting an underwater housing's buoyancy and trim can help improve imaging productivity. Depending on the type of diving being carried out, some divers prefer to dive with neutrally or negatively buoyant housings. @Alex_Mustard and @adamhanlon discuss the importance of buoyancy and how to add buoyancy to a housing if required. 

What is your opinion on float arms that can be partially flooded to fine-tune buoyancy? Weefine WFA37/Kraken KR-FA01, Hugyfot HugyFloat, Adjustable, etc.

I’ve recently been playing around on this theme (in the bath only so far)

Trim weights added to 8” acrylic dome. This in combination with a ~300g net buoyancy arm that spans between the handles just above the eye piece, puts the housing just below the waterline. There is still maybe a 30degree tilt upwards from horizontal, man those acrylic are floaty!

This is with no strobes/arms by the way. I have separately weighted one ‘arm system’ that comprises a Inon z240 and a LFM video light on a triple ball clamp. These are on 8” (narrow) + 6” (fat) float arms. This ‘arm system’ is about 200g negative. With the pair added to the slightly positive housing, I’m hoping I’ll end up with the whole thing neutral and maybe a tad negative.

Too big to float the whole system freely in the bath, so trial run at Capernwray soon!

My off camera video lights (Scubalamp v6k pro) are very negative (about 750g + in real life). Carrying two has a massive impact on my weighting, so I’ve been trying to find a way to overcome this.

Enter the stealth (not) float! It results in ~100g net negative in fresh (the bath). The shape is an added bonus as if I lay them down in a rocky area, a bit of weight added to the back (shown here as a finger) will point the light upwards, avoiding a hotspot on the ground.

They are a bit big, but hopefully better than acting as an anchor!

Any feedback or ideas welcome

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Many vendors report UW weights for their gear your V6K lights are reported to 560 gr UW, your Z-240 are only 77gr UW.    INON provide UW weights for all their gear,  clamps are 33 gr each UW.  Then you need one more arm, so about 730 - 800 gr per side. 

On your  float for the lamp  - what sort of foam is it?  can you compress it by hand?  If you can you'll lose that buoyancy as you descend.

A good option for your system might be the INON Mega float arm M which has 650 gr of buoyancy and should nicely offset the light plus strobe/arms and be maybe 100 gr negative per side.  http://www.inon.jp/products/armsystem/arm.html

Many vendors report UW weights for their gear your V6K lights are reported to 560 gr UW, your Z-240 are only 77gr UW.    INON provide UW weights for all their gear,  clamps are 33 gr each UW.  Then you need one more arm, so about 730 - 800 gr per side. 

On your  float for the lamp  - what sort of foam is it?  can you compress it by hand?  If you can you'll lose that buoyancy as you descend.

A good option for your system might be the INON Mega float arm M which has 650 gr of buoyancy and should nicely offset the light plus strobe/arms and be maybe 100 gr negative per side.  http://www.inon.jp/products/armsystem/arm.html

 

For clarity, I am happy with my setup pending a full scale test in the big salty.

FWIW I have found the in-water weight of the Scubalamps to be higher than reported (no surprises- just like overstating lumens!). I have previously tried the ‘calculation method’ and found there is no substitute for actually putting the stuff in the water.

The lamp float is a ‘modified’ commercial fishing float. EVA foam good to 1000m or something. Given the stealth look with some hobby paint.

I’ll post another pic of the full setup later.

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