So to follow up on this (And admittedly, i'm trying to learn as I go on this, so forgive the occasional dumb question), if i'm looking at these two options:
Option 1: 6 lb Steel plate, no ditchable weight
Option 2: 3 lb aluminum plate, 3 lbs ditchable weight
Wouldn't option 2 be preferable, as you could go at least 3 lbs LESS negative in the event of a buoyancy failure? (And a tad lighter to fly with, given that i'll always be flying)
One of key benefits of a using a Stainless plate with thin suits and buoyant tanks is the ballast is over your buoyant lungs and alongside the buoyant cylinder vs on you waist as is typical with other BC's and or a lightweight plate.
While I'm not dismissing the concerns about baggage fees, it's always seemed odd to me that folks would spend thousands of dollars in a diving vacation and then make less than optimal gear selections in order to save ~3 lbs.
DSS sells light weight, less negative plates for those applications where a SS plate will over weight the diver *in the water* The classic example would be a diver using thin suits and negative steel tanks.
Having said that lets get back to beating the dead horse of ditchable weight.
Again lets start with a neutral diver using a 3 mm suit and buoyant al 80. The suit is 3-4 lbs positive and the cylinder is +4 empty. This diver will need ~ 6-7 lbs of total ballast in order to hold a shallow safety stop with a (near) empty tank. (Actual empty tank generally signal end of the safety stop
)
A SS plate, harness, reg and full al 80 will be -9 ~10 with a full cylinder and ~-4 with an empty tank. A diver using this rig will be right about 5-6 lbs negative at the start of the dive when their cylinder is full.
If they start -5 and manage to fully compress their wetsuit *without* using *any* gas from their tank, i.e. a hot drop to ~180+ FSW. then they may find themselves -9 lbs.
Now lets look at reality. Single tank rec dives aren't hot dropping to 180 ft. So our diver *might* be at most 6-7 lbs negative *at depth* of course if they had to swim this massive 6-7 lbs load up their wetsuit will of course be rebounding as they ascend reducing their negative buoyancy back to the 5 lbs they started with.
Now they reach the surface and discover no boat in sight! and they are -5 lbs with a non functioning wing. If this is really the case their options are to inflate an alternative float, like an smb, or ditch their rig.
Now switch in a light weight plate and add 3 lbs of weight belt. Now our diver only needs to swim up 3-4 lbs (hardly a major difference) and when they arrive at the surface they are still negative, with pretty much the same options as above. Sure may they can tread water longer when they are 2-3 lbs negative vs 5 but negative is negative, after a while you need to kiss the gear good by.
Of course one could add a foam pad infested inherently buoyant BC. Which of course only adds to amount of ballast needed and adds to amount of ballast a panicked diver would need to swim up....... This is IMO as silly as adding ballast so you have something to ditch.
Tobin
