BP&W - what is the proper weighting approach?

[rack201]

I'm planning to get an OMS or Oxycheq BP&W setup, but what is the proper approach to weighting? I've seen posts suggesting a steel BP&W is great as some people do not need additional lead, but others that suggest having no ditchable weight is a risk.

All my diving is currently singles, tropical waters where I wear a 3mm full wetsuit and carry about 6kg. My current BC is a Knighthawk.

A stainless steel OMS backplate and STA comes out at about 4.1kg, so depending on how positively bouyant my current BC is, this setup may mean I don't need additional weight. Is this the aim or should I go with an Aluminium back plate to ensure I keep some ditchable weight on my belt?

Travel weight is not really an issue.

Another question I have is re a STA. Most BPs look like they have slots for cam bands, and suggest STAs are not required, but may hold the tank to the BP more rigidly - whats the go?

Cheers

 

[dkktsunami]

My wing/plate (Golem 35#) does not need a STA, tank remains firmly in place. I carry no ditchable weight. Weight is in SS plate (5 lbs) and in XS Scuba pockets on the cam bands, amount depending on exposure suit and salt v. fresh. To be in any danger from not having ditchable weights would require a double failure - no gas and defective wing and I accept this as a very minimal risk. The risk of a weight belt falling off is considerably higher - I have seen this happen to three divers in one day in the keys. My purpose for weight configuration is to maintain perfect trim. I am long and slender and legs tend to sink without proper weight placement. I travel with this by the way and carry aboard the entire kit.

 

[ScubaFeenD]

I'm planning to get an OMS or Oxycheq BP&W setup, but what is the proper approach to weighting? I've seen posts suggesting a steel BP&W is great as some people do not need additional lead, but others that suggest having no ditchable weight is a risk.

All my diving is currently singles, tropical waters where I wear a 3mm full wetsuit and carry about 6kg. My current BC is a Knighthawk.

A stainless steel OMS backplate and STA comes out at about 4.1kg, so depending on how positively bouyant my current BC is, this setup may mean I don't need additional weight. Is this the aim or should I go with an Aluminium back plate to ensure I keep some ditchable weight on my belt?

Travel weight is not really an issue.

Another question I have is re a STA. Most BPs look like they have slots for cam bands, and suggest STAs are not required, but may hold the tank to the BP more rigidly - whats the go?

Cheers

If you are diving a wetsuit I would tend to keep some weight on a belt for ditching if needed. Doesn't need to be loads of weight, but enough to help you get up off the bottom when you are at depth (Assuming proper weighting initially). You can get a SS plate, or you can get an Al plate and get camband weight pockets which seem to work pretty well for me. Both systems work, but the Al might give you more weighting options, because it is not inherently weighted as much as the Al BP (the downside with Al plate and cambands is that your weight is not more distributed over your lungs).

I have an oxycheq 30# singles wing and I love it. It doesn't need an STA due to built in STA like stabilizer, which work very well in my experience (the tanks doesnt budge, which is how it should be). Also, if you are interested in that wing, Cave Adenturers has a great deal on a hogarthian setup with an oxycheq wing.
here is the link: Dive Rite back plate w/ Dive Rite Basic Harness & choice of wing [DROCpkg] - $325.00 : Cave Adventurers!, We will NOT be undersold!!!

good luck, you will LOVE the BP/W setup!

 

[greylion]

With no ditchable weight you'd still be able to swim the whole rig up. In open water tropical diving with a good dive buddy I wouldn't worry too much about ditchable weight. Better to be properly weighted and not all that negative to begin with.

 

[GrumpyOldGuy]

If you are diving a wetsuit I would tend to keep some weight on a belt for ditching if needed.[-] Doesn't need to be loads of weight, but enough to help you get up off the bottom when you are at depth (Assuming proper weighting initially)[/-].

Fixed, ditching on the bottom is a very weak argument, it is hard to comprehend if it is every needed. If you look at when dives really need to ditch weight (vs. the more common accidental release), it is on or near the surface.

 

[SkimFisher]

It depends on your weight requirements now. Are you diving steel tanks? If not, do you plan to? That can also play a factor. Depending on your weight requirements now, the combination of a steel BP and steel tanks could mean too much weight at the end of the day and make "ditchable weight" a moot point.

 

[Mike Boswell]

After having tried a different manufacturer's setup, my wife and I now both use Oxycheq rigs and love them.

We use the Mach V 40# wing so as to have a little extra buoyancy for emergency/Rescue situations. It is the same length as the 30# but an inch or so wider, and won't wrap under the bottom of a tank creating a wear problem.

The wing does not need an STA as it has a built-in stabilizer for the tank. The plate is bent at the correct angles so as to give the wing room to expand properly. This also permits a more compact wing.

Using a single tank (we use HP100's), the Oxycheq wing's offset inflator elbow won't interfere with the tank valve or jam into the regulator the way a center-mount elbow does.

We use waist belt pockets with velcro flaps for lead. With a 7-mil wetsuit (HP100s) we use about 8 lbs total, and with no wetsuit (AL80s) we use about 4 lbs total.

A tri-fold pocket on the waist belt holds whatever other stuff we might want to take (mask, car keys, etc)

With a full HP100 tank, this rigs floats on the surface.

With the lead in waist pockets I can easily empty one or both lead pockets quickly if the need ever arose, and I don't have to worry about a weight belt slipping down or falling off.

 

[ScubaFeenD]

Fixed, ditching on the bottom is a very weak argument, it is hard to comprehend if it is every needed. If you look at when dives really need to ditch weight (vs. the more common accidental release), it is on or near the surface.

If you start out properly weighted (ie you can stay at 15-10 ft with essentially empty tanks) then in the beginning of a dive you will be slightly negative. Plus, with the compression of the neoprene you will further be negative depending on how deep you go. If you dont have any ditch-able weight to help make you more positive you will need to ditch your gear if something happen where you have to get off the bottom.

If you dont want to wear a belt you can wear camband weight pockets on your tank which would also allow you to ditch weight should the need arise.

It depends on your weight requirements now. Are you diving steel tanks? If not, do you plan to? That can also play a factor. Depending on your weight requirements now, the combination of a steel BP and steel tanks could mean too much weight at the end of the day and make "ditchable weight" a moot point.

I love diving steel tanks, but I would prob not suggest them if there is so much negativity with them that you have no hope of achieving neutrality; steel tanks are going to add significantly to your weighting. Al in tropical water should suffice and will help you regarding not being negative (or at least too negative)

 

[SkimFisher]

I love diving steel tanks, but I would prob not suggest them if there is so much negativity with them that you have no hope of achieving neutrality; steel tanks are going to add significantly to your weighting. Al in tropical water should suffice and will help you regarding not being negative (or at least too negative)

Again - contingent upon your current weight requirements. Some people just don't need much. Many divers diving doubles are extremely overweighted due to the tanks alone. That doesn't make it wrong. I don't subscribe to the theory that one MUST have ditchable weight, but that's a topic for another thread entirely.

For most shallow tropical diving/vacation diving/insta-buddy situations - you are correct. Steels are overkill.

 

[TSandM]

The topic of ditchable weight is a controversial one. I think it makes sense to ask yourself when you might need to ditch weights. One possible case would be that of a total wing failure, so that you could not hold any gas in the bag to speak of at all. But let's look at that: If you are diving an Al80, you have about 5 lbs of usable gas, so, if you are properly weighted, you start the dive 5 lbs negative. If you are diving a 3 mil wetsuit, you don't have much buoyancy from your exposure protection to lose (my experience with mine is that it's about 4 lbs). So, at the very beginning of a dive, at 100 fsw or more, you may be as much as 9 lbs negative. Most people can swim up about 10 lbs -- you might want to try that, and see if you can. (Best way is to put a 10 lb weight belt on the bottom of a pool, and try to pick it up and swim it to the surface.) If so, you can swim your rig up from the bottom in a worst-case scenario.

By far more common would be needing to be as positively buoyant as possible on the surface. If you are on the surface, with a total wing failure, you can shed your gear and you and your suit will be positive. If you have a tear in the wing, you can take your gear off and orient the bag so that the tear is at the bottom, and it will hold some flotation gas.

Note that all these calculations change and become much less reassuring, if you change to larger or more negative tanks, or if you switch to heavier exposure protection. This is the origin of the recommendation not to dive deep in a heavy wetsuit, and not to use steel tanks with a wetsuit (although the latter was really aimed at steel doubles).

If you are a novice, or envisioning these scenarios worries you, then use the lighter plate and a weight belt.

I don't like STAs. I use DSS wings with wobble-stoppers, and they hold the tank absolutely still. I believe Oxycheq has a similar system.