Question Cheap method to check balanced rig/trim weights?

[rsingler]

I’ll probably need the weights to do that too since the XLS estimates my full 7mm (wetsuit, hood, gloves, booties) to be 33.6 lbs. positively buoyant!

One source of buoyancy error in the spreadsheet is taking manufacturer "thickness" at face value.
Those buoyancies are calculated from neoprene densities alone.
But if your "7mm" actually has 5mm of neoprene and a couple of layers of Bare's "graphene" super material, that changes things. The graphene is probably neutral buoyancy and part of the thickness may not be closed cell, but instead traps warm water along the skin.
That's a long way of saying,
1) Examine the material (usually at a zipper where there's a cut edge) and determine how thick the closed cell material is.
2) Enter only the thickness of the closed cell material in the spreadsheet, no matter what the advertised thickness of the suit is.
Manufacturers take some liberties in their thickness claims, when the suit should probably be marketed as "as warm as a 7mm suit."

I'm on my way to Key Largo on Sunday for a week of diving, and to test out my new Bare 3mm Reactive 2 graphene wetsuit. I'll compare my usual 3mm suit weight requirement and let you know.

 

[rsingler]

Here is "5mm" Bare Reactive glove material.

You can see how entering 5mm in the spreadsheet would overestimate both buoyancy and weight requirement.

 

[BoltSnap]

Here is "5mm" Bare Reactive glove material.
View attachment 753148
View attachment 753147
You can see how entering 5mm in the spreadsheet would overestimate both buoyancy and weight requirement.

The bottom part is thicker than the upper part of the boot?

 

[rsingler]

The bottom part is thicker than the upper part of the boot glove?

Could be. I'll check in a couple days. Sorry, but I just packed up the gloves for a week in Key Largo.

 

[gmerick]

Cheap method: start out slightly over weighted. Fill two 2 liter pop bottles from the lake as you go down to 5m. Gradually blow air into the pop bottles, and release air from your BC until the BC is empty. once you are neutral, and still under water, check the level of air in the pop bottles, an empty bottle will be contributing 4.5 lbs of lift. Subtract the pop bottles lift from what you are wearing, and add weight corresponding to the air remaining in your tank(s). (7.65 lbs per 100 cu ft). Once your total weight is right, you can spend the rest of your life working out distribution of trim weight between ankles, belt, or shoulders.

 

[Calatinus]

Great tool. Have you measured your wetsuit buoyancy? That's the largest uncertainty in the calculations.

As for the trim, I suggest borrowing an assortment of lead from your local shop. Ideally they also have a pool to use.

Out of curiosity: could you theoretically (or even practically) bundle up your wetsuit in a mesh bag, tie it to a luggage scale and try pulling it just below the pool surface to check its positive buoyancy?

 

[rsingler]

Out of curiosity: could you theoretically (or even practically) bundle up your wetsuit in a mesh bag, tie it to a luggage scale and try pulling it just below the pool surface to check its positive buoyancy?

Almost. Put it in a mesh bag, and add weights until it's just awash. No sense ruining a luggage scale in the pool. But yeah, that'll work.

 

[Calatinus]

Almost. Put it in a mesh bag, and add weights until it's just awash. No sense ruining a luggage scale in the pool. But yeah, that'll work.

B-b..but ... that's what you suggested in the other thread

 

[inquis]

Out of curiosity: could you theoretically (or even practically) bundle up your wetsuit in a mesh bag

Absolutely. Put a bunch of lead in the bag. No need to be precise. (I used an old rusted vice as ballast the last time I did this, as I didn't have enough lead to sink a 7mm.) Weigh the bundle with and without the wetsuit. The difference of those two measurements is the wetsuit buoyancy.

 

[rsingler]

B-b..but ... that's what you suggested in the other thread

Assuming you aren't teasing me, and therefore responding as though this were a real question, one needs to think about what the luggage scale suggestion means in both cases. This explanation is really for the lurkers, who may be confused but have not posted...

To determine in-water weight of the plate, you hold the scale above the water, and dip the plate below the surface, connected to the scale by a string.

To determine in-water buoyancy of the suit, you submerge the scale (and probably yourself below it), and pull down on the scale until the bag is just submerged. But don't pull it down to the bottom of the pool, because now, wetsuit compression will reduce its buoyancy, which was the whole reason for creating the Optimal Buoyancy Computer in the first place. In either case, the scale is probably now toast, or soon will be.

If this was a real question, your "Oh, duh!" moment may now commence.