Switching from 3mm full wetsuit to 7mm full wetsuit in Salt Water

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scubajoe86

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When in doubt it is time to ask the experts. My wife and I have both logged about 200 dives but mainly in the warm Caribbean waters off of Cozumel. We're headed to the Galapagos islands and this is our first experience with cold water diving. We are switching from 3mm full wetsuits to brand new 7mm full wetsuits with hoods, and I need some help on a good starting weight for our checkout dive. I'm not worried if I'm a little off as I can trim out the weight on subsequent dives, but I'd like to avoid being grossly under or over weight to start.

We are both fairly small people and with our 3mm full wetsuits in salt water we typically use 8lbs of weight. I wear a men's medium wetsuit and my wife wears a women's size 8 wetsuit. Keeping all other gear considerations the same, can anyone tell me a good starting point for weight using the 7mm wetsuits?

Thanks in advance for the help. Cheers Joe
 
I am 5' 8" and about 175lbs. I use 8 lbs with a 3 mm suit and about 21 lbs with a 7 mm semi dry. Your body may be different and your weight may be different but this should get you in the ballpark...
 
Depends on the tanks you are using.

I use 2 kilos on my waist plus a 1 kilo weight on a camband at the bottom of an AL80 when diving a 3mm suit

With my 7mm semi dry, 4 kilos on my waist plus the 1 kilo on the tank

If I had steel tanks it would be different, probably lose the tank weight for starters, and when I dive doubles I rarely use a weight belt unless I am diving dry.

I am 170 cm and weigh 67 Kg - Medium sized wetsuit
 
I typically go from zero with a 3mm to 8lbs for 7mm and a 4mm hood using the same gear setup otherwise.

Couple of points for you. If the hoods don't have a vent in the top then make a hole in them to get rid of air. When you descend do so vertically and pat the hood to get rid of trapped air. You may also need to duck dive and fin down the first couple of feet. If you are weighted to sink at the beginning then you might find yourself overweight a the end. The first dive with a dry 7mm is when it's at its most buoyant
 
I just got a used (but almost new) 7 mil farmer john. With the old one (used, bought 10 years ago) I was using 37 lbs. with an AL80 tank (6', 195 lbs.). I kept on doing weight checks until I reached the needed 45 lbs. (!!!). So I can see how it's age affects a wetsuit.
 
I must be a "lucky" weight /height. for me its 1kg for every mm of suit seems to be the formula.
 
When I used my 7mil wet suit with the farmer john, I needed 26 pounds. I also recommend you bring your lighter suit. I found I did not need the heavier suit and was really happy not to have to use all that weight. Plus, you can layer it if you need to. You might want to buy a hooded vest to increase your options.

The live aboard will have a checkout dive, probably the first day, and they will get you properly weighted before you decend for that dive. There will probably be other divers who have a new, thicker wetsuit to get weighted for. They will expect it.

Hope you have a great time. Please write a review when you get back.
 
I just got a used (but almost new) 7 mil farmer john. With the old one (used, bought 10 years ago) I was using 37 lbs. with an AL80 tank (6', 195 lbs.). I kept on doing weight checks until I reached the needed 45 lbs. (!!!). So I can see how it's age affects a wetsuit.

I've always assumed that an older wetsuit is less buoyant.

I'm amazed at the amount of lead people have to wear. I'm 6'2 & 200lbs even when I restarted and with 20 dives I was only at 26lbs - that was with a 5/7mm a 4mm shorty on top, a 4mm hood and a BCD. I know I was then diving a 12l steel - but that's only worth -6lbs on an AL80 (assuming AL80 is +4 t end of a dive)

Now I dive a wing and over the last 2 years have reduced from a SS plate, to an Al plate (-4lbs) and now I dive without a plate. I dive a 15l steel which is -10lbs full and -4lbs empty and wearing a 3mm in the summer I've been a bit too negative at dive end.

Even though we're supposed to have a high (er) salinity here I can only presume that because colder water is more dense it's a lot more buoyant. Given TMHeimer's experience and that we're a similar size - it must be the water temp that increases the amount of lead people wear!


Another mark against cold water diving for me
 
Been a long time since I dove in those. The only tip I'd have is get a big thermos. If you're going to have a short surface interval and don't want to get out of it, some warm water can be nice.
 
I've always assumed that an older wetsuit is less buoyant.

I'm amazed at the amount of lead people have to wear. I'm 6'2 & 200lbs even when I restarted and with 20 dives I was only at 26lbs - that was with a 5/7mm a 4mm shorty on top, a 4mm hood and a BCD. I know I was then diving a 12l steel - but that's only worth -6lbs on an AL80 (assuming AL80 is +4 t end of a dive)

Now I dive a wing and over the last 2 years have reduced from a SS plate, to an Al plate (-4lbs) and now I dive without a plate. I dive a 15l steel which is -10lbs full and -4lbs empty and wearing a 3mm in the summer I've been a bit too negative at dive end.

Even though we're supposed to have a high (er) salinity here I can only presume that because colder water is more dense it's a lot more buoyant. Given TMHeimer's experience and that we're a similar size - it must be the water temp that increases the amount of lead people wear!


Another mark against cold water diving for me
Not necessary to add lead if cold.. Here in NY I am 5'11 weight 175 and use 16 to 18 lbs of lead in a 7mm wetsuit.
in a DUI cf200 and 400 gram thinsulate I am up to 24 lbs of lead . This is in salt water. Much less in fresh water. Tank can be a HP steel 80 or alum 80. I usually do not bother taking less lead when using steel tank. BCD is a Dive Rite transpac with rec wing bladder.
 

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