New to BP/W. How much lead and lift do I need?

[sadn3sss]

I've only had 10 ocean dives but would like to invest in my own equipment. Going full BP/W and can't decide understand how much lead and lift I need. I've done as much research as I could but I still haven't been able to get an answer that I understand. Hoping you guys can help.

Basic:

I'm 5'8", weigh 155 lbs. When diving with a rental BCD ( that lab tests shows +1 bouyancy), I have about 10 lbs in the trim pockets and 18 lbs in the integrated weight pockets. I wear a 7mm farmer john and jacket and a hood, and an AL80 tank. I haven't had a chance to do a weight check yet but I don't think I'm serverly overweight. I have trouble descending naturally and sometimes have to help myself down by swimming or otherwise.

1) How much lead would I need switching to a BP/W, all else being the same?

Seems like switching from a BCD that's +1, to a BP/W that is -8 lbs (SS/BP - 6, STA -2), I can wear -9 lbs. of lead? So that would be 19 lbs? From what I've read that seems high so I don't understand where my calculations are wrong, unless I started off being too overly weighted.

2) How much lift do I need? Everything I've read tells me 30 lbs is enough for any tank I may use. I'm considering getting a 40 lb wing.

To me it seems like it is enough but barely or maybe not. The figures I got for loss of bouyancy at depth for a 7mm wetsuit range from 15-28 lbs. That seems like a big range. If the 28 lb figure is correct, the wing would have to compensate for that if I were down at 100 ft. With the extra weight of the air and a few other things, 30 lbs doesn't seem enough. What am I missing?

Also, if I chose to put all my weights into the trim pockets and some integrated ditchable weight pockets, the BP/W would have to be able to float at the surface. With 28 lbs of lead and 5-6 lbs of air, a 30 lb wing would surely sink.

What am I missing? Are all these people who said 30 lbs was enough diving in the Carribeans? That's what I thought but some of them were wearing 7mm wetsuits also.

 

[tbone1004]

well, so here goes. You need 27lbs to sink you and the tank, not including 6lbs of gas in the AL80, so you have 33lbs total that you need to compensate for. 40lbs will be sufficient.

17lbs total with the stab jacket, equates to needing roughly 10lbs added on top of a plate. You are in San Jose, support local business and buy from Deep Sea Supply who makes all of their equipment in LA area. You are in standard size range for a "medium" backplate. It may also be worth considering getting the weight plates from Tobin. This will give you an extra 8lbs on top of the backplate, for roughly -14lbs total ballast. A couple of trim pockets or a weight belt with a pair of 4lb weights should be sufficient to get you down once you get a bit more comfy in the water

Deep Sea Supply Medium SS Plate with weight plates, and a Torus35 wing would be my recommendation

 

[cool_hardware52]

Fresh or salt?
I'll assume salt.

Your cylinder is +4 empty and about +3 @500 PSI.

You are currently getting in the water with ~30 lbs of things that don't float. 28 lead and about 2 for your reg.

30 less your bc (1 lbs), less your cylinder (3lbs @ 500 psi) leaves 26 lbs to sink a diver 5'8" x 155 lbs wearing a 7mm suit.

IME that is about 6-8 lbs more than you need. A typical 7mm suit on a guy your size will be in the high teens to low twenties.

I would recommend a medium SS plate. The plate, harness and reg will provide about 8 lbs of ballast, which is usually a good match for divers in warm water using buoyant al 80's and 3mm wetsuits.

For warm water you can use a very small wing. 17 lbs is enough to float your rig with a full tank, and more than enough to compensate for the ~4 lbs of buoyancy the typical 3mm suit starts with.

If you expect to keep diving al 80's and 7mm suits I'd suggest testing the suit. Knowing the suit buoyancy allows one to select the smallest wing possible for cold water diving, and quite often these wings are OK in warm water too.

If you would like me to make a specific recommendation it's far easier to do so via a phone call.

626-799-5074 M-F 9-5 ish most days.

In the interest of full disclosure I design, manufacturer and sell BP&W's

Good luck,

Tobin

 

[tbone1004]

in the interest of full disclosure, Tobin designs, manufactures, and sells bada$$ BP/W's

buy what he tells you, though I do agree that the lead is quite a bit too much, test the suit and verify. I would be surprised if you needed much more than 20lbs. Get your breathing under control and make sure you are descending efficiently and you'd be surprised at how much you can take off

 

[halocline]

It's very unusual for a single tank diver to need a 40 lb wing. You would be smart to make sure your weighting is correct and then calculate how much lift you need. You only need lift to compensate for the compression of your wetsuit and the weight of gas used. You do need to be able to float your rig without you in it, but with the amount of lead you are discussing it would be foolish to put all of it on your rig; much better to split up the ballast between your body (with a weight belt) and the rig (steel plate). Smaller wings are in general more fun to dive with.

 

[sadn3sss]

So that's what I've been doing but I'm getting different answers from different sources. I guess I'll just have to finish my weight check at 15ft/500psi and/or test the wetsuit to get a clearer answer.

It seems all you guys are in agreement regarding the possibility of me being overweighted. You all seem to think that about 20 lbs of ballast should be enough. If that were the case, I think a 30 lb wing would be adequate.

As it is, a 7mm 2-piece, plus hood/gloves/boots, I use 28 lbs. I'm already having trouble going down but we'll see. It's possible I still have air pockets. I need to resolve that first.

However, all the local shops suggest a starting point would be 10% of body weight (10% x 155 = 15.5 lbs) plus 12 lbs. Which is why I have about 28 lbs of ballast.

That seems to match the suggestions of two websites I went to within a range (24 lbs for expert, 31 lbs for novice). They go something like this

10% of body weight plus 4-5 lbs = 20 lbs,
add gloves/hood/boots = 2 lbs,
add salt water = 5 lbs,

Adds up pretty well.

Estimating Weights for Scuba Diving
Estimated Diving Weight Calculator | DiveBuddy.com

As an aside, I once dove with a size M Aqualung Pro HD. The integrated weight pockets held 30 lbs but the lift capacity was rated at 29 lbs. Not very smart of me or the manufacturer. I only went as deep as 50 ft so didn't lose all the buoyancy in the wetsuit.

 

[Sevenrider860]

As an aside, I once dove with a size M Aqualung Pro HD. The integrated weight pockets held 30 lbs but the lift capacity was rated at 29 lbs. Not very smart of me or the manufacturer. I only went as deep as 50 ft so didn't lose all the buoyancy in the wetsuit.

I do the majority of my diving using DSS backplates and wings..so I will repeat what has already been repeated. You cannot go wrong talking with Tobin and getting a DSS kit. On occasion I do use an Aqualung BCD...

The Medium Aqualung Pro HD has a 29 pound lift capacity. The maximum detachable weight capacity for size XS to ML is only 20 pounds. Size L through XL is 30 pounds and those have a lift capacity of 44 pounds (L) or 55 pounds (XL). These maximums are indicated on the BCDs. If 30 pounds was placed into a Size Medium Pro HD...it was not on the manufacturer.

 

[Imla]

Considering you have merely 10 dives, the difficulties sinking could be due to wrong technique.
Often new divers tend to do things in the wrong order, and hence end up taking a breath in when they shouldn't.

Try this the next time you are ready to descend:
1. Take a deep breath in and HOLD (Yes.. you are at the surface... no harm done )
2. Empty your drysuit/BCD completely (WHILE holding your breath)
3. Cross your feet and lean slightly forward (You are still at the surface as you haven't exhaled yet...)
4. Now... you can exhale and lean even more forward. You will end up around 2-3m in a horizontal position and deep enough that a breath in won't push you to the top again.
5. Keep Calm and continue breathing

Often, the problem is that you empty your lungs before your bcd is empty and as a result you need to breathe in too soon and go back up again with the feeling that you do not have enough lead. Keep note of the "Cross your feet" section. A lot of new divers are unconscious of their finning action, and being in a vertical position, your finning only directs motion one way... UP.

 

[Neilwood]

A technique my instructor gave during my AOW was to breathe in, kick up and then, once you are near the top of the kick, vent the BCD and breathe out. That way all your air is on its way out as you are already going down.

I now feel like I can descend a bit easier that way.

 

[tbone1004]

the local shops are idiots, no offense. Simple math and physics, you need to figure out how floaty your exposure suit is, and how sinky everything else is. Easiest way to do this is with a mesh bag, a bunch of lead and a luggage scale. Go to the ocean ideally if you can, but a pool and some math will be fine. Load a bunch of lead, in this case 30 or so pounds into a mesh bag with a zipper to keep everything inside, and hang it in the water from a luggage scale. You need more lead than the suit requires to get a reading obviously, but that's how it's done. Everything else is rough math. Most of the time people have trouble getting down because they don't exhale all the way, they don't stop moving, try crossing your ankles for descent, and they have air pockets somewhere. A 7mm farmer john is a lot of neoprene and you have to make sure that thing is fully flooded before you try to descent.

There are no weight differences for expert and novice. Intentionally overweighting yourself or someone else is negligent and dangerous.

At 50ft you lost most of the buoyancy in the wetsuit btw. Focus on making sure you are exhaled all the way, not moving your feet or hands, and have the wing completely empty