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jchance

How close to neutral buoyancy should I be?

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I weighed my current set-up in saltwater with my various lens/port/extension tube combinations. I use a Nikon 7200 in a Nauticam housing with twin Inon 240 strobes. I also have a Sola light and Go-Pro attached too. I use 2 8" stick arms and 2 8"X2" diameter float arms. I always knew I was somewhat negative but discovered that I am between 2 and 3 pounds negative for every lens combo I use.

 

Should I continue to use it like this or should I add floats or change my stick arms to floaters to get more neutral? What do you think and what if anything would you change?

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I would strive for something close to neutral if not a little positive. if you have to let go of it as it is it will sink to the bottom fast. If it is just slightly positive it will go to the surface and be easier to handle.

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I think positive vs. negative depends on whether you plan on hand holding the rig for the entire dive or whether you occasionally need your hands free and have clip off the housing/let it dangle from a tether.

 

I shoot for just a little bit negative. Yes, it will sink slowly if I drop it, but it's not like a rock. I'd rather have it hang down when its clipped off that have it float up in my face when I'm shooting a DSMB, stowing hoses, or switching bottles around. There are just times when I need my hands and I want the housing out of the way (down).

 

2-3 lbs negative is a lot though.

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Positive buoyancy on gear is never a good idea imho and can actually be pretty dangerous. More than one diver got injured by hunting their upwards-floating cameras not watching decompression stops or ascend speeds.

 

Up to 500 grams (1lb) negative on a larger setup is just fine. Significantly more can get uncomfortable over time.

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I prefer to be a bit negative, that way I let go and my rig will gradually float down. But being a bit positive or negative is personal preference.

 

What I believe jchance is asking is buoyancy advice for his Nauticam D7200 rig.

 

What do others use for additional buoyancy on their Nauticam D7200?

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You are correct Elmer but there seems to a difference of opinions. I am in favor of slightly negative and never realized that I was 3# negative until I checked it. Getting closer to neutral will be a change for the better. BTW--just ordered 2 of the 3.5x8" Nauticam arms to try. That adds 46 ounces of positive. Will be interested to see how that changes my larger dome buoyancy.

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I weighed my current set-up in saltwater with my various lens/port/extension tube combinations. I use a Nikon 7200 in a Nauticam housing with twin Inon 240 strobes. I also have a Sola light and Go-Pro attached too. I use 2 8" stick arms and 2 8"X2" diameter float arms. I always knew I was somewhat negative but discovered that I am between 2 and 3 pounds negative for every lens combo I use.

 

Should I continue to use it like this or should I add floats or change my stick arms to floaters to get more neutral? What do you think and what if anything would you change?

 

I'm using the same camera in a Nauticam NA-D7100 housing - what port are you using? and how did you attach your gopro? I have the opposite problem, I've found my 8.5" port to be positively buoyant which is a real pain as I need to find a way to counteract this.

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Mine is never positive regardless of which lens/port combo I am using. I have a Tokina 10-14mm with the small Zen dome, a Sigma 17-70mm that I use behind a Zen 170mm dome and both a Nikon 110mm and a Nikon 60mm that I use behind a Nauticam Port 30 with the necessary rings for each combo. I am using a Nauticam housing with both a 7100 and a 7200 body. I also use the Nauticam accessory viewfinders. I have an accessory ball on the top of each arm for a total of 4; Nauticam 8" float arms proximal and Nauticam regular stick arms distally with twin Inon 240 strobes. I also have a Sola Photo on one ball and a GoPro Hero 3+ on the remaining ball.

 

This set-up requires 8 clamps with it. I had to swap the 8" regular float arms for the 8" fat arms. Doing this changed me from being 3# heavy to just 1/2 # negative. I just finished 2 weeks of diving and it was a breeze to handle the camera like this.


Why do you need such a large dome? Hard with travelling and much more air space. Are you using and air filled arms?

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Mine is never positive regardless of which lens/port combo I am using. I have a Tokina 10-14mm with the small Zen dome, a Sigma 17-70mm that I use behind a Zen 170mm dome and both a Nikon 110mm and a Nikon 60mm that I use behind a Nauticam Port 30 with the necessary rings for each combo. I am using a Nauticam housing with both a 7100 and a 7200 body. I also use the Nauticam accessory viewfinders. I have an accessory ball on the top of each arm for a total of 4; Nauticam 8" float arms proximal and Nauticam regular stick arms distally with twin Inon 240 strobes. I also have a Sola Photo on one ball and a GoPro Hero 3+ on the remaining ball.

 

This set-up requires 8 clamps with it. I had to swap the 8" regular float arms for the 8" fat arms. Doing this changed me from being 3# heavy to just 1/2 # negative. I just finished 2 weeks of diving and it was a breeze to handle the camera like this.

Why do you need such a large dome? Hard with travelling and much more air space. Are you using and air filled arms?

 

I thought the dome would be a good place to start, and the price was good too... had I have known that I would have these problems, I definitely would have purchased a zen dome. I've got the Stix floats and I've tried different arm configurations, but the floaty dome is still a problem for me. I'm also using sea & sea strobes, which I understand now are a slightly negative weight under water whereas the inon's are a positive weight.

 

I'll be adding the M10 ball mounts to the housing as soon as I can remove the plastic filler plug thats there. I haven't got the removal tool, and they're stuck in pretty tight!

 

I also have the Sigma 17-70 lens, and at some point in the future I will use that in my underwater set up too. Right now, I'm just keen to start taking some photos with the Tokina lens, once I resolve this issue with the current dome.

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I just replied to your dome question, I hope that information may help with your problems.

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Pardon my ignorance, but how do you guys measure lbs negative?

Edited by rgilkes

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Hi rglikes

 

One way of doing it is to set your gear up, tie a short length of rope to suspend it from - and then use a luggage-style hand scale to weigh it whilst your gear hangs, submerged in water similar to that in which you'd dive. The weight that is shown is the negative weight.

 

This will change, of course, between fresh water and sea water.

 

For the type of scale, see for example https://www.amazon.co.uk/FREETOO-Portable-Suitcase-Function-Capacity/

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One way of doing it is to set your gear up, tie a short length of rope to suspend it from - and then use a luggage-style hand scale to weigh it whilst your gear hangs, submerged in water similar to that in which you'd dive. The weight that is shown is the negative weight.

 

 

That makes sense. Thanks!!

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No problem!

 

I can't say I've ever done it. Neutral buoyancy for my camera gear is far more along the lines of, yeah, that'll do.... My macro system with a 105mm is somewhat negative. My 15mm with a 230mm dome is a tad too positive buoyant.

 

It's all personal preferences as you've seen from the various posts.

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