Weighing advisements

[barnaby_s]

Just after a guesstimate/starting point for weighting when swapping from a buddy commando and 12l to twin 12s with a 3mm backplate and wing.

Currently on 16kg on fresh water (5'9, 100kg and a more fat than is healthy), what would be a good starting weight for my weight check?

[Nickpicks]

I used to dive a single 12 with 8kg in fresh water. Swapping to twin 12s and a 3mm backplate, I dropped to 2.5kg, so a starting point of around 10kg might be a good place to start.

[jb2cool]

What’s the backplate made of? Steel, aluminium or something else?

[barnaby_s]

Sorry, steel backplate

[Steve Clark]

It will depend on your undersuit.

As a starter, I’m 6’2, 110kgs. I dive 5kgs of v-weight with a thick 400g undersuit, d12s, steel plate in fresh water. I add 3-4kgs on a weight belt for the sea. I only put enough air in my suit to lose the squeeze and keep warm. All buoyancy driven by the wing.

[witchieblackcat]

I'm a similar size to Steve Clark above. With FE Arctics I used 3kg in fresh water and added 2-4kg in salt (probably only needed 2 but err on the side of overweight rather than underweight).
I did all my buoyancy through the suit and never used the wing unless I had a couple of stages.

[barnaby_s]

Thanks for all this.
I have the RoHo thermocline, which seems to displace about the same as a 100gsm thinsulate.

[Vanny]

For me I’d do a weight check. So go in with no lead , preferably close to empty cylinders. Take a weight belt and get your buddy to pass you lead until your able to sink. If it’s done in fresh water add 2/3 kg for salt , if you can’t do it on close to empty cylinders you’ll need to calculate the weight of the gas and add that to your sinking weight. Something like this will help with the gas ; https://www.subaqua.co.uk/cylinder-buoyancy.php you don’t need to wear the belt just hold it if your comfortable with that. Somewhere shallow like near the edge at Stoney is ideal so it’s easy for your buddy to help you sort it out.

[barnaby_s]

I will be doing this at Stoney on Saturday, assuming no extra local lockdowns there, but it will be with full cylinders. I am quite a floaty person so just wanted a starting point as I am sure I will need some extra weight.
At the end of the day I might be able to try again with nearly empty cylinders to confirm.

[profpointy]

For what it's worth I have similar steel backplate and twin 12s, and use a 1kg fixed tail weight for trim, and use maybe 4kg of lead on my belt (not needed in fresh water) I am maybe 80kg so you'll likely need a bit mire lead than me all other things being equal

[Allan Carr]

At the end of the day I might be able to try again with nearly empty cylinders to confirm.

I never bother with weight checks with empty cylinders, I just calculate the weight of gas and adjust accordingly.

[Energy58]

As a first stab drop about 5 kg going from single to twin twelves with a "normal" thickness SS backplate and bands and not changing anything else - assuming your single rig was a BCD.

But you need a proper weight check - the extra bulk of twins does make it feel "different" and you need to be comfortable

[Allan Carr]

The easiest way to check the buoyancy of individual configurations is using one of the scales for weighing baggage before you fly. Lower the kit into the water until submerged and compare the readings. If the cylinder is buoyant, just add a known amount of weight to it until it submerges. You can use this technique to compare the buoyancy of different configurations without doing a suck it and see in the water.

[MW1963]

For what it's worth, I went from a 15 and 3 Litre Pony wearing a 7mm Neoprene Dry suit, remember them!! to Twin 10 300 Bar and didn't need a weight belt, it was the poor buggers on the RIB hauling the twinset aboard who suffered:<)

[barnaby_s]

For what it's worth, I went from a 15 and 3 Litre Pony wearing a 7mm Neoprene Dry suit, remember them!! to Twin 10 300 Bar and didn't need a weight belt, it was the poor buggers on the RIB hauling the twinset aboard who suffered:<)

I have been one of those poor buggers in the past...