As long as I remember, all of my DSLR rigs have been negatively buoyant. Nowadays, with ViDSLR, adding weights to balance out the dome (if you use acrylic domes) and housing with lights/strobes means it can be as heavy as 1kg(2.2lbs) negative. And anyone who has a 230mm+ diameter glass dome port will agree that some buoyancy compensation is necessary.
Strobe/light arms have pretty much been always negative, constructed out of aluminium or marine steel. Some arm manufacturers have made positive buoyancy arms of aluminum, and others have added buoyancy foam (like Stix) to offset the weight. However, these solutions mean added weight and bulk for travellers.
The Sea Gadget Carbon arms. 29mm diameter on the side arms, The fat one in the middle is the prototype 60mm.
In April @ ADEX, I mentioned seeing a new product that promised to be a game changer (well not that new, it’s been around since 2009). Arms made of carbon fiber that were lightweight yet offered positive buoyancy up to 85% of it’s total weight. Carbon fiber is a very strong woven material that is extension used in automobiles, bicycles and even airplanes to to minimize weight. I was sold and I wanted them!
David Cheung of Scubacam Singapore, kindly offered to let me try his Sea Gadget brand carbon fiber arms. I chose arms based on what I needed to offset on my different rigs. For example, the 41mm arm, with a diameter of 29mm, weighs 131g and gives 110g of buoyancy! The 60mm diameter, 200mm arm weights 240g and gives 200g of buoyancy. Mmmm choices choices!
With these arms, my housing is now about 100g negative for wide angle shooting with the big dome and 200g for macro. This alleviates arm fatigue and even carpal tunnel syndrome (a friend of mine actually got CTS from diving with his unbalanced heavy rig, but he was always a bit limp wristed! ☺)
There are a few caveats:
1. UV light degrades the epoxy used to seal the carbon fibers. There are epoxies which are UV resistant. I have not been able to ascertain the product life cycle obviously.
2. The carbon fiber weave paint job can be scratched with abuse. I managed to scrape it during my South Africa trip but that’s serious pounding in 3m swells!
The carbon fiber paintjob can be scratched off. It takes a lot of abuse to get there, but it can happen!
3. The ball heads aren’t exactly industry size, but a little smaller. This does make clamping them harder work. They still work well with ULCS, TLC and Seacam clamps, among others.
4. Physics demands that the buoyancy efficiency be inversely proportionate. The shorter arms have correspondingly less buoyancy. My 28mm long arms only have 50g of buoyancy and weighs 113g.
I now own a set of 29mm and will be buying a set of 60mm to offset the big domes, 3D GoPro video housing, hartenberger strobes and focus light for my macro set.
DISCLOSURE: These arms were originally loaned to me from David Cheung of Scubacam. I bought them after the test because I liked them. All at retail price.