Custom weights

[the_one_who_waits]

I am new to drysuit diving and have been putting together a rig for local dives, I realized I need way more weight than I'm used to in comparison to wetsuit diving. As I was researching weights and options, I come to learn that the soft weight pouches are just filled with lead shot.

Well I happen to be a trapshooter (primarily Olympic/International/Bunker), and go through 1-2k rounds a month. During the latest ammo shortage of 2021, I thought about getting into reloading and started accumulating shot, powder, primers, etc. Well, I never got into reloading and just have a small stockpile of components I completely forgot about until yesterday.

And so it just made perfect sense to use the shot I have to pack my own weights. I was going to go with fabric/mesh bags but then thought of the possibility of the stitching and threads becoming loose over time before my weight pockets start spilling out shot everywhere. Then thought about ziplock bags, but did not have any sized to fit into my weight pockets. And I remembered I have a Foodsaver vacuum seal machine I use for sous vide which would be perfect for the job, as the bags can be sized to any dimension.

But safety first. Working with lead shot means a lot of lead dust and fine particulates. I turned on a small fan that circulated air out of my workbench area, opened my garage doors for ventilation. Wore a 3m half-face respirator, safety goggles, and disposable gloves. Had wet wipes on the side to wipe down the scale and Foodsaver machine immediately after.

I made a mixture of different sized shots from BB to #8.
Used the weight pocket insert as a template to size the bags. The widths should wider to match the depth of the pocket. The length should be an addition 2-3in longer in order to properly seat into the machine.
Filled the bag up to the desired weight.
Vacuumed and sealed the bag.

I ended up double-bagging them as additional precaution (dive safety is all about redundancy, right?). Since they are vacuumed-sealed (the pressure inside is negative), if they ever develop a leak it will be visually-apparent. It all took about 30mins. I remember paying about $2/lb for the shot, which in retrospect is a great value compared to the pre-packaged ones going for $5-$7/lb.

I think this is process is ideal for anyone else like me that still is figuring out weighting and balancing, and don't want to end up with a small collection of various weights. Plus I'm pretty sure I will be going through this several more times as I dive more and decide I want to add some weights to adjust trim and such. Also, I did do a search after the fact and it turns out some of you have done this, or mentioned the idea, many years prior (so can't say I am the first).

 

[Badger7]

I really like the concept. I think the spot price of bulk lead is somewhere around $1/lb while scuba weights can get in the neighborhood of $5/lb, so your $2 is a lot more reasonable. Those bags are pretty tough, but you're not really pulling much of a vacuum when sealing, just removing the air that doesn't fill the spaces between the shot. When taking them to depth, I'm curious how much more stress the skin of the bag will experience. The plastic film will get "sucked in" tighter, but that lead shot will nicely support the film over a large area without leaving much linear space for the plastic to dimple in, my guess anyway.

Are you going to be zipping those into a weight pouch / bcd pocket so if they aren't quite as durable as you'd like, even double bagged, that you aren't pouring shot out of a quick release pouch and going positive unexpectedly?

 

[NW Dive Dawg]

I think the seal-a-meal idea might be good to prevent or reduce any "bleeding" or lead exposure.......but I'd still put them into some ballistic nylon or cordura pouches just for overall durability...

 

[the_one_who_waits]

I really like the concept. I think the spot price of bulk lead is somewhere around $1/lb while scuba weights can get in the neighborhood of $5/lb, so your $2 is a lot more reasonable. Those bags are pretty tough, but you're not really pulling much of a vacuum when sealing, just removing the air that doesn't fill the spaces between the shot. When taking them to depth, I'm curious how much more stress the skin of the bag will experience. The plastic film will get "sucked in" tighter, but that lead shot will nicely support the film over a large area without leaving much linear space for the plastic to dimple in, my guess anyway.

Are you going to be zipping those into a weight pouch / bcd pocket so if they aren't quite as durable as you'd like, even double bagged, that you aren't pouring shot out of a quick release pouch and going positive unexpectedly?

Good point about the tightening/shrinking at-depth. But they're packed pretty tight now which means there's not very much air left for movement. But definitely will keep an eye on it every couple dozen dives.

I packed these into a pouch that slide into pockets affixed onto the waistband, which are made out of 1000-Denier Nylon. So two layers of sturdy nylon serving as additional buffer.

 

[Badger7]

One other thought - they are going to be pretty close, but unlike solid lead weights, or regular shot weights with a permeable bag that lets water infiltrate, 4 lbs of lead isn't going to provide 4 lbs of negative buoyancy, since the plastic will keep the water out of the spaces in between, you'll have a package with measurably less density than solid lead. A quick google search looks like a tightly packed mass of small spheres can at best comprise 74% of any given volume. Back of the napkin math then says 4 pounds of lead shot in a sealed pouch would only act like 3 pounds of lead underwater.

Since you have that luggage scale handy, might want to take one of those weights for a quick dip in the kitchen sink to see how much "less" they weigh underwater in actual practice.

 

[the_one_who_waits]

One other thought - they are going to be pretty close, but unlike solid lead weights, or regular shot weights with a permeable bag that lets water infiltrate, 4 lbs of lead isn't going to provide 4 lbs of negative buoyancy, since the plastic will keep the water out of the spaces in between, you'll have a package with measurably less density than solid lead. A quick google search looks like a tightly packed mass of small spheres can at best comprise 74% of any given volume. Back of the napkin math then says 4 pounds of lead shot in a sealed pouch would only act like 3 pounds of lead underwater.

Since you have that luggage scale handy, might want to take one of those weights for a quick dip in the kitchen sink to see how much "less" they weigh underwater in actual practice.

Yes!!
I omitted some steps in my first post as I was worried there would be too much detail, but I'm glad you mentioned it. I first started out using only BBs and #2, as they are least in-demand (shotgun sports are regulated to #7.5 and smaller). I bagged 5lbs of that but then realized how much air was being trapped in-between the shot. I weighed it in a bucket of water and it resulted in 3.5lbs. This led (hehe) me to mix in smaller shot to fill in as much of the space as possible, and added an additional pound to account for any air still left. End result is 9.92lbs in-water, which for me is 'good enough' as a first step in figuring my weighting and balancing of my rig.

Carrying weights with variable buoyancy is definitely not ideal so I also have been entertaining the idea of filling the bag with an environmentally-friendly and viscuous liquid (such as vegetable glycerin) in the meantime.

 

[johndiver999]

why not add water to the shot and then seal it? You have no compression at depth then?

 

[Boarderguy]

Add water or sand. Sand will fill in most of the small spaces and won't cause a giant mess when your bags inevitably leak on the drive home.

 

[rx7diver]

Have you considered purchasing/borrowing a mold and making your own solid weights, melting down your Pb shot using a propane stove or similar?

My GF and I made our first solid weights this way, but used discarded auto wheel weights. Long time ago (1988?). Still have and use these weights.

rx7diver