weight question for using steel 120

[eastcoastbas]

I'm going to curacao this weekend to participate in the Lionfish challenge and will be using steel 120's. It's a two dive event and will not have time for a check dive. Can anyone tell me how much weight I need to drop? I normally dive with aluminum 80's and 100's, wear a 7mm suit and use 16lbs. of weight. I have never used steel tanks so have no reference and no time for trying stuff out. I hope there's someone here who is used to switching between alu and steel tanks and can answer this.
Many thanks,
Bas

 

[MMM]

I don't suppose you will be wearing the 7mm suit in curacao. Or will you?

 

[eastcoastbas]

yes, I will. I live on Bonaire and wear a 7 in the cold months. It's nice to be comfy when your dives often go over 100 minutes. 2 of those in a row and I get cold, add another long nightdive and I freeze in a 3mil. Also, I dive almost every day.

 

[ktomlinson]

I doubt you will need any even if you wear your wetsuit. If you are wearing a wetsuit and have no time to check before the dive, you could take 2-4 lbs with you just to be safe. A full 120 can be anywhere from -10 to -26 lb buoyant according to the chart linked below whereas your al80 is only -1.8 when full.

http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

 

[Craig66]

I would take off 3 and depending on how over weighted you feel maybe another one or two on the next dive. Average I have found has been about 4-5. I did the same switch in Coz recently and lost 4 immediately and then another 1 over the next day.

Now its your turn - what kind of water temps can I expect in May in Bonaire - I need a 5mm for anything less than 80 and a 6-7mm for anything less than 76? I was thinking of bringing a 3mm and a 5mm?

Thanks and good luck on slaying those lions

 

[herbdb]

I own Catalina 80s and Worthington HP E-7 120s. I use 6-8 lbs more weight with the Aluminum tanks.

Al empty +4 Full. -2
St empty -2 Full -10

Could be slightly different for your specific tanks.

 

[eastcoastbas]

Thanks Craig & Herb, those are the answers I was looking for! I'll drop 4lbs and see how it goes. Rather have a little too much as I can compensate for it but have no room for rocks
As for your suit question, Craig. I'm on celcius but I think the temp will be getting close to the 80's. If I was you, go with the 5mm. Don't think you'll regret it. Especially after a few days. You can always let some water in if it gets a little warm, more difficult the other way around.
Thanks again, that was really helpful. As for the LF.. those gonna be looong dives, lots of time to do some damage and round up a lot of them. I'm really looking forward to it, also because there's a lot more lf on cur than on bon.

 

[jd950]

Never mind.

 

[idive2]

I own Catalina 80s and Worthington HP E-7 120s. I use 6-8 lbs more weight with the Aluminum tanks.
.

I dive steel LP85's and used to go with about 6 lbs more when using a back-up AL80 but last time
I ended up with what appeared to be about an 8 lb difference. standard disclaimer: a proper weight check
should always be done when changing gear configuration prior to diving.

 

[midas6t6]

I have AL 80s and Faber HP117s. I use 8 pounds less with the Fabers.