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eyu

Subal ND7100, is buoyancy needed?

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Dear Fellow Wetpixel Members,

 

I am considering getting a Subal ND7100 housing and a Nikon D7200 body.

 

Those of you who are using the Subal ND7100 with two Inon Z240's and a 60 mm macro port, how much added buoyancy is needed to make this rig neutral buoyant?

 

Thanks,

Elmer

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The flotation for my Subal ND800 works fine, made of Plexiglass or ABS sheet and closed cell PVC foam (must be closed cell to not get water logged), attached with stainless bolts. The Plexiglass top is shaped with a hand power saw and drill and a hand coping saw, with 4 ULCS balls and a compass attached.
The flotation is Divinycell foam, with a volume of about 0.6 liters. Two PVC pipe spacers provide rigidity and hold the bolts, through 25 mm holes in the PVC foam. The foam pieces can be glued together with plumbers PVC glue, or held with cable ties, and spray painted black.
The carrying handle is nylon cloth tape, with a hole (burned with a hot nail) at each end for a SS bolt, inside a flexible plastic tube with side holes drilled in it to free flood.
Flotation for each Inon Z240 strobe is eight 50 x 15 mm bars of foam secured between two duct tapes; a rubber band cut from an inner tube holds it on the strobe. Each 4 inch arm and clamps has separate foam floats, about 0.36 liter volume.
Underwater the entire assembly weighs just a few hundred grams. The idea is to have just a bit of negative buoyancy, with the centers of flotation for the housing and each strobe being more or less directly over their centers of weight, to allow for free camera and strobe placement.
Materials I used:
Divinycell foam, 1 or 3/4 inch thick PN 01-12600 or -12800 Aircraft Spruce, https://www.aircraftspruce.com/catalog/ cmpages/divinycellfoam.php.
Plexiglass or ABS 4 mm sheet, 305 x 80 mm,
Stainless hex head bolts, four 5 x 60 mm & four washers,
Thin-wall 3/4 inch PVC tube, two 50 mm lengths (Sch40 is too thick walled),
Nylon climbing tape 16 x 500 mm,
Tygon tube, 13 id x 300 mm,
PVC glue or cable ties,
ULCS ball mounts, four, SKU: ul-ba-aqw,
Bolts & nuts, eight, 1/4-20, aluminum or SS,
Black spray paint,
Old inner tube or thick rubber bands,
Drill w 1/4" bit, coping saw, wood saw, sharp blade.
-
Good luck!

 

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Hi Elmer,

 

Yes you will definitely need some buoyancy, how much will depend on the combined elements of your rig and how close to neutral you want the system in water. It is always interesting to see other photographers solutions. I use home made cork collars around the port and a couple of fishing net floats at the back of the housing over the viewfinder. Whether you home engineer a solution or use commercially available floats/arms you will need to experiment with quantity to find the best lift combination for your needs.

 

Mark

 

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Hi Elmer

 

I'm sure you have sorted this by now......

 

On my Subal housing (D800) with two Inons, I use Stix on the four ULC arms: 2x 8" and 2x 5". Although this still leaves my setup negatively buoyant with a Nikkor 105mm and Subal M/AF port, I've never found this a big problem. Yeah, if I let go it'd head downwards pretty sharpish - so I have lanyard attached to it and my BCD. But for handling the camera it's not an issue and the Stix on the arms don't get in the way or add too much bulk.

 

With a 230mm Subal port, EXR and a Nikkor 16-35 it's only slightly negatively buoyant. Downward drift is slight. Damn heavy though topside!

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With a 180 viewfinder, FP 90 port, two Z240's I have found that two Nauticam 90 mm x 150 mm carbon float arms with two 8' ULCS arms with one jumbo Stix each works.

It is just negative. Attaching the buoyancy arm next to the housing helps with the tendency of the housing wanting to turn port up.

Will need to try attaching some floats to the 180 viewfinder to further balance the rig.

 

PS: this is my wife's rig, so it is imperative I keep her happy

 

Elmer

Edited by eyu

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