GH5 - bouyancy

Hi all,

I'm trying to figure out how much positive buoyancy I should add to my rig which comprises:

Nauticam GH5 housing

Two Keldan 4X video lights (negative 0.4 kg in total)

Lenses used will be WWL-1 with float collar or SMC-1 (but not both together).

I'm thinking along the lines of getting two of the Nauticam 50 x 300 float arms which will give me a total of 640g positive buoyancy, but I'm really shooting in the dark.  I'd appreciate your thoughts and guidance on this.

Thanks

Keldan sell float rings for their lights buy them as the lights have torque that will bend your arms

The WWL-1 with the collar together with the 35 macro port and the 14-42 MkII is 880 grams negative in fresh water in total you will need 2 KG of lift muvh better to balance the lights and the housing separately and keep the arms light

Stix (or similar) floats are a more flexible and much less expensive alternative to rigid arms. Four jumbo floats provide about 750 grams of buoyancy. The adjustable float belt for ports can provide up to about 1 kg of buoyancy.  I like the ability to adjust total buoyancy to each port.

Keldan makes a cool float / clamp device with a standard 1" ball joint but it is hella expensive

2 minutes ago, troporobo said:

Stix (or similar) floats are a more flexible and much less expensive alternative to rigid arms. Four jumbo floats provide about 750 grams of buoyancy. The adjustable float belt for ports can provide up to about 1 kg of buoyancy.  I like the ability to adjust total buoyancy to each port.

Keldan makes a cool float / clamp device with a standard 1" ball joint but it is hella expensive

Stix floats are not enough with shorter arms to lift the GH5 when you have video lights hence my suggestion to get the keldan floats they are expensive but make the light neutral from there you can try and use stix otherwise it will go down with 5+8 arms even when full of jumbo floats (1.6 Kg lift vs 2.0 Kg of the rig)

Weigh your rig in water using a travel scale, takes the guess work out of it.  Just hang the fully setup rig from a rope or similar and be sure it is 100% submerged.  Fresh water is fine, it has only a little less buoyancy than in salt.  It will be fine if you end up 100gr or so negative in fresh.

Weigh your rig in water using a travel scale, takes the guess work out of it.  Just hang the fully setup rig from a rope or similar and be sure it is 100% submerged.  Fresh water is fine, it has only a little less buoyancy than in salt.  It will be fine if you end up 100gr or so negative in fresh.

Thanks everyone. I have asked for a quotation for the Keldan floats and will be purchasing them. Meanwhile I have purchased a luggage scale. I weighed the housing + SMC1 + single flip + 2 Keldan 4X's and it looks like I will need 1.6kg positive. It looks like I will be getting 2 x the 70 x 300 mm arms with a total of 1.34 kg lift.

I did think that it was a pretty standard sort of rig and that someone would know. But the luggage scale does come in handy.

Arms and clamps will add 400-500 grams if not float
Make sure you allow for that
Also consider that while for wide angle you want a neutral rig for macro you may want it negative


Sent from my iPhone using Tapatalk

Yes, I should have mentioned that I use longer arms, even for macro, so I can get 4 Stix jumbo floats on my rig.  Even with those, it's about 0.5 kg negative, which honestly is fine even on long dives. I would not want it much more negative, so I totally get the point about offsetting heavy video lights. 

I weighed my system with the WWW-1 lens today and it came out at about 1.45 kg. I will be adding a bayonet adapter, which is on order, so the weight should be pretty similar to the SMC-1's 1.6kg.

I also weighed my old system and it came out at 0.65kg negative. I quite like this weight as I can remain in horizontal trim whilst holding the camera out in front of me. So it looks like adding positive buoyancy anywhere between 1 kg and 1.6 kg should be good for me. Nearer 1.6 kg would be better as it will allow addition of things like snoots at a later stage.

I can have one 0.67 kg float arm on both sides to give a total of 1.34 kg positive buoyancy, or I can have 2 x 0.32 kg float arms on both sides to give 1.28 kg positive buoyancy (less the additional pair of ball clamps). Right now I'm leaning towards the former, (one float arm on each side with total positive buoyancy of 1.34 kg) unless anyone knows of any reason why two float arms on each side should be preferred.

The housing and clamps will be 950 grams get two segments close to it with similar lift. If you balance the lights with their own floats this will be fine
It is important to avoid torque as the arms will tend to bend if most of the weight is on the lights. So if your don’t get the keldan floats it may make sense to distribute the lift


Sent from my iPhone using Tapatalk

21 minutes ago, Interceptor121 said:

The housing and clamps will be 950 grams get two segments close to it with similar lift. If you balance the lights with their own floats this will be fine
It is important to avoid torque as the arms will tend to bend if most of the weight is on the lights. So if your don’t get the keldan floats it may make sense to distribute the lift


Sent from my iPhone using Tapatalk

Many thanks. Keldan floats on order. Two segments it is.

Appreciate the advice hitting like or similar
And subscribe my blog you have a lot of reading to do lol


Sent from my iPhone using Tapatalk

On 12/30/2019 at 4:35 PM, Interceptor121 said:

Appreciate the advice hitting like or similar
And subscribe my blog you have a lot of reading to do lol


Sent from my iPhone using Tapatalk

Didn't realise that there was a 'like' button on this forum. Have since found it.

I thought that I subscribed a couple of days ago. Will do so again.

Didn't know that hitting a like button is better than saying thank you...

2 hours ago, Lionfi2s said:

Didn't know that hitting a like button is better than saying thank you...

LOL, one vote for saying "thank you"!

5 minutes ago, TimG said:

LOL, one vote for saying "thank you"!

The wetpixel forum in the new form awards points to people that have liked or loved post and nothing to thank you as it does not parse the text

Moving on with the times

 Hey, I'm an ageing geezer, I still think it's nice that people say thank you....  (AND hit the Like) 

... and I like to hold the door open for people. 

Sorry WK's Gone Diving - this is getting way off track.....

No worries.