7mm Overall w/Jacket vs One Piece Wetsuit Weighting Question

[ChimarraoMate]

Have any of you moved from a one piece 7mm suite to the two piece overall style 7mm suits? How different was the weighting requirements? Was it a lot? I ask because that seems to be the case for my 13 year old son:

In 7mm One Piece:
His Weight: 120 lb
Calculated Weights at 10% + 4lb in salt water: 16 lb
Actual Weights: 22 lbs (The rental shop overweighted him, I think the 2x 8 lbs + 2x3 lbs was all they had)
Weights were a slight heavy (it worked good for 5 lb buoyancy gain of used aluminum tank)

Then we switched him to a new wetsuit--7mm Henderson Overall with Separate over one leg long sleeve Jacket:
Using 22 lb, and having 1000 psi in his tank, empty BCD bladder, he was too buoyant and was not able to descend.

We only had a short time to do the second dive and decided to call it a day, rather than head back to the shop and fiddle with more weights.

Is that to be expected with the overalls? I guess the dual lays of 7mm around the torso might add a lot more, but I am not really sure. Part of me wonders if he was just cold getting into the 65 f degree water (45 f outside) in the new suit (he had not had time to let the thin layer of water in the suit warm up much) and although he exhaled, he may have held a little breath(like you might when you are cold) instead of exhaling all the way.

Anyway, the question is, what is the expected difference in buoyancy and weight requirements of the two types of suits?

 

[fjpatrum]

If I'm reading it correctly, he had a 7mm farmer john with a 7mm jacket vice a single 7mm full suit? If that's the case, he's definitely going to need at least a few more pounds of lead in the new configuration.

I would say, though, he probably has some air trapped somewhere. That kind of weight, unless your son is 4 feet tall, seems quite high. I'm assuming you're both fairly new divers? When I first started diving in colder water I had a hard time adjusting to the step in jacket over my suit. I always had to swim down a little before I would stop corking. It took probably a handful of dives before this stopped happening. Is the suit new or was it a rental?

 

[freewillie]

Any time you change your configuration you will need to recalculate your weighting. That is especially true when using brand new wetsuits. The new neoprene has factory new bubbles and will inherently have more buoyancy than the same suit after multiple dives. If you add extra neoprene with a farmer john/jacket style two piece combination wetsuit then you will definitely have to compensate for not only the new wetsuit buoyancy but the extra neoprene as well.

There is no hard and fast rule for adjusting your weight. I had one instructor advise me to add 5 lbs. when adding a vest. I found this a little too much and was noticeably over weighted during that dive. Two lbs. was a better adjustment but after playing with the weights I discovered no compensation was necessary.

In general you need to go through a formal weight check each and every time you change your gear and especially when using a new or different wetsuit. Any other calculations are educated guesses.

 

[ChimarraoMate]

If I'm reading it correctly, he had a 7mm farmer john with a 7mm jacket vice a single 7mm full suit? If that's the case, he's definitely going to need at least a few more pounds of lead in the new configuration.

I would say, though, he probably has some air trapped somewhere. That kind of weight, unless your son is 4 feet tall, seems quite high. I'm assuming you're both fairly new divers? When I first started diving in colder water I had a hard time adjusting to the step in jacket over my suit. I always had to swim down a little before I would stop corking. It took probably a handful of dives before this stopped happening. Is the suit new or was it a rental?

Thanks, and yes the farmer John Style was the newer one he switched over too. At first I thought he was already overweighted, so I did not bring out any more weights. I think it makes sense that air may have been trapped in the suit, because he had not been in the suit long, and probably needed about 5 more minutes to get the wetsuit wet and warmed up like it is suppose to.

Yes, we are new at this. That was going to be our 11th dive, which is why I decided to buy, instead of renting. The Bonneville Seabase, is a man made place out in the Utah desert, for diving. They offered to let us apply his rental charge to the purchase of the suit. Seemed like a fair deal since he needs one for where we will be diving and I've been buying our equipment new, so I only have to rent tanks and weights.

He was a little frustrated changing suits. We had a hell of a time getting it on, but the fit was good once we did. On a side note, we went home later and discovered the plastic bag trick. That works unbelievably well, he was able to slide right into a 7mm suit with ease using the plastic bags.

 

[Vegan Shark]

Nothing wrong with trial and error Just keep note of how much weight he is wearing each dive, and how is buoyancy is at 500 PSI on the safety stop, then add/subtract weight until he hits the sweet spot. Personally, I wear 6-8 lbs more in a farmer john set up. But there is variation between brands, and no sure way to know how much weight you need except to get in the water and find out.