Buoyancy Change With Thinner Wetsuit?

[laikabear]

I usually dive SoCal cold water with a 7mm wetsuit, hood, & gloves. I have a SS backplate and use a steel HP 100 tank, and only need 8 lbs of ditchable weight. I'm going on vacation to Cozumel in a couple of weeks and wondering if going down to a 2.5mm wetsuit (but using an AL80 tank) if that will work with my SS backplate. Both wetsuits are by Waterproof (W4 and W30).

In essence, is there a way to guesstimate the difference in buoyancy between my usual thick wetsuit and hood vs. a thinner suit?

When I bought the plate (DSS) I discussed possibly diving tropically with Tobin, and it sounded like the steel plate would still be ok assuming using an aluminum tank. But at that time I was using more weight. Now that I am more comfortable underwater I need less.

 

[Jayfarmlaw]

Most dive ops can guess your weight needs damn near spot on. They will err on the heavy side so you can always leave some weight on the boat for your second dive, or probably even pass some weight to the DM during the dive if needed. Diving my 7.5 mm takes an anchor 22# to get me to sink, my 3mm takes about 12# in Coz. That's with a Scubapro Glide X BCD and an 80 aluminum in fresh water.

Most dive ops will use 80 aluminum tanks, or a 100 for $10 more. There are a few that will use steel 120's (Aldora and I think living underwater)

I wouldn't worry about it, your dive op will get you dialed in. We will be there 4-15 to 4-20 and diving with Aldora, staying at Casa Mexicana.

Good luck, safe travels,
Jay

 

[laikabear]

My concern was that with only 8 lbs of ditchable weight up here, that might leave me with none if I dive the SS backplate down there. If I'm too heavy with the plate and thin wetsuit, then it won't be a matter of how much weight, it will be down to renting a BCD which I'd rather not do.

I am staying at Casa Mexicana also (solo), maybe will see you there. (16-22)

 

[dbulmer]

I have the Waterproof D30 and with an ali plate I would use 1 to 2 Kg. In the Red Sea I used a 5mm D4 and used 10kg to start with and came down to 8kg.

I think from your description that you won't need any weight with the steel backplate and provided you can swim up with whatever tank you use, all will be fine.

Not needing a weightbelt is really nice

Use your first dive as a checkout. If conditions allow, empty your wing and swim up. It might take a second or 2 to get used to doing this but you should be able to ascend.
Don't forget to tell your buddy or DM that you are going to try this just in case they are wondering what you are doing. If you find it hard just add a little gas to your wing to compensate

 

[JohnnyC]

You'll be fine even if you don't need any weight. If you can't swim up a single aluminum 80 I would think you would need to evaluate whether or not you were in the sort of physical condition to partake in scuba diving as an activity.

 

[Patoux01]

If you find it hard just add a little gas to your wing to compensate

Which 200% defeats the purpose of that "exercise"...

Might be fine with the SS plate. I'd give it a shot as I know I can swim that up with no problem. Except if you're talking 6mm SS plate, then it gets on the very heavy side imo.

I'd also never count on someone telling me "you need this amount, trust me I'm spot on", as that is usually wrong.

 

[Lorenzoid]

My concern was that with only 8 lbs of ditchable weight up here, that might leave me with none if I dive the SS backplate down there. If I'm too heavy with the plate and thin wetsuit, then it won't be a matter of how much weight, it will be down to renting a BCD which I'd rather not do.

I am staying at Casa Mexicana also (solo), maybe will see you there. (16-22)

With a 3/2 full wetsuit, a steel DSS plate, and an Al 80, I put about 2 lbs. of lead in trim pockets on the cambands to help with trim. I could probably dive just fine with zero lead. It's enough ballast that I can hold a safety stop. And I can easily swim up from depth with a completely deflated wing. So I have no need for ditchable lead. The combination of a SS plate, an Al 80, and a thin suit is the best!

 

[decompression]

Crunch the numbers....
BP is -6
Tank is +4
Suit is +4

You will be very close to neutral, maybe add 4 lbs at first. Congrats!

 

[scubadiver888]

I usually dive SoCal cold water with a 7mm wetsuit, hood, & gloves. I have a SS backplate and use a steel HP 100 tank, and only need 8 lbs of ditchable weight. I'm going on vacation to Cozumel in a couple of weeks and wondering if going down to a 2.5mm wetsuit (but using an AL80 tank) if that will work with my SS backplate. Both wetsuits are by Waterproof (W4 and W30).

In essence, is there a way to guesstimate the difference in buoyancy between my usual thick wetsuit and hood vs. a thinner suit?

When I bought the plate (DSS) I discussed possibly diving tropically with Tobin, and it sounded like the steel plate would still be ok assuming using an aluminum tank. But at that time I was using more weight. Now that I am more comfortable underwater I need less.

I dive the same gear in Canada that you are listing for SoCal. I have a 7mm wetsuit, hood & gloves, SS backplate and HP100. I tried using my setup in the pool but I switched to an old 3mm wetsuit. I found I was diving with no ditchable weight and negatively buoyant. I switch to an AL80 tank and found myself neutral with no ditchable weight. With a 2.5mm wetsuit you might be slightly negative BUT my plate is 8lbs. If your plate weighs less than 8lbs you should be able to get away with using it in Cozumel.

That said, when I dive in my 3mm now I use an aluminum plate and an AL80. This lets me put a little ditchable weight on.

 

[JBFG]

Crunch the numbers....
BP is -6
Tank is +4
Suit is +4

You will be very close to neutral, maybe add 4 lbs at first. Congrats!

Don't forget +4 for salt water.