help with drysuit buoyancy calculation

[orange_diver]

No need to if you are properly weighted. For weights you add some (3-4kg or 5-9lbs)
when going to ocean from fresh water, but with bouyancy such compensation is not needed.
To be accurate in the ocean you need less bouyancy capacity compared to fresh water.

my OP was trying to determine the wing lift i would need, i.e. 30# or 40#, so it would matter how much lead i was carrying in case i needed to float the rig at the surface if it was all weight integrated.

so, i guess no one out there except Scared Silly has figured out how much buoyancy their trilam drysuit and undergarment have??

 

[TeddyDiver]

my OP was trying to determine the wing lift i would need, i.e. 30# or 40#, so it would matter how much lead i was carrying in case i needed to float the rig at the surface if it was all weight integrated.

so, i guess no one out there except Scared Silly has figured out how much buoyancy their trilam drysuit and undergarment have??

Sorry beeing inaccurate.

The weight you have trying to balance you in the pool with the DS is only for measuring the volume ie boyancy of the suit, which is needed for the spreadsheet you are calculating the proper wing size for you. Note also that wing got to give you enough bouyancy at the dpth you are, not just on the surface.

The amount of lead is only a part of the boyancy formula.

Most have (I have) I quess, but it's a sum of variables, and there's no right answer for you except to do the test and/or calculation yourself.

 

[TSandM]

I got in the pool with my trilam dry suit and undergarments, and it took 28 pounds to get me neutral. I'm 5'4" and 120 lbs, but I wear a lot of undergarment.

 

[orange_diver]

I got in the pool with my trilam dry suit and undergarments, and it took 28 pounds to get me neutral. I'm 5'4" and 120 lbs, but I wear a lot of undergarment.

do you dive steel singles with your drysuit? if so, can you please tell me your set up, how much weight you use (28 i guess?) and where you've distributed the weight?

TIA...

 

[TSandM]

I dive Worthington 95s with a SS backplate (5 lbs). I carry 18 pounds on a weight belt, 3 on my cambands, and 2 in a can light. It doesn't quite add up, but I think I may not have emptied the suit real well the day I did the measurements. The weighting I describe trims me out horizontal and allows me to hold a 10 foot stop while hanging onto an inflated SMB, with 500 psi.

 

[cummings66]

I have a 30lb lift wing and it's fine for my cold water diving.

My weights are basically 20 lbs of lead for a Viking Arctic Extreme undergarment which is actually heavier than a 400 gr only undergarment because it has a fleece layer as well. Not to mention I wear fleece thermals under it.

Well, I would. Normally I dive with my other Viking undergarment which is basically a 200 gr thinsulate undergarment with fleece thermals under it. (the thermals absorb the sweat so I don't have to wash the undergarment as often) and it's fine. I use 10 lbs of lead on a belt for that.

Additionally I have a can light for about 2 more lbs, and my BP and it's weight plate come in at 13 lbs. So you could say with my Viking Extreme drysuit and the 200 gr thinsulate I need a total of about 25 lbs. Now with my Viking Sport I need only 15 lbs to get neutral. It's a heavier rubber suit and fits tighter as well.

You can see that with two vastly different drysuits, both of which are membrane, that I have widely differing weight requirements to get neutral. However, wing lift never needs to be more than 30 lbs with either drysuit or undergarments.

I dive a single steel HP120 tank with that, sometimes a steel HP100.

 

[orange_diver]

great stuff everyone, thanks for all the info...

 

[*Floater*]

i'm trying to figure out how big a wing i need to dive my drysuit and a single steel faber LP. i don't have one currently but will be purchasing a SS bp/w with hog harness. this is for socal ocean dives. i'd love to be able to get away with a 30# wing, but think i may need 40#.

i've read all the posts, thank you especially to Tobin and someone else who posted an excel spreadsheet and the one peice of info i'm missing is this:

how much buoyancy does my dui CLXse (shoulder entry CLX450) and wheezle extreme undergarment inherently have that i would have to compensate for?

i was hoping people could weigh in with their experiences with the same or like materials, i.e. trilaminate suits and 200 - 400g thinsulate garments...

thank you all in advance.

Why would you need 40#? A large tank carries about 10# worth of gas, so if you are correctly weighted you should have 10# worth of positive buoyancy in your wing at the beginning of the dive to compensate for the full tank and then as the tank gets lighter you vent the wing until the wing and tank are both almost empty...

The CLX450 is a trilam drysuit, right? So it doesn't loose any buoyancy as you go deeper since you'll be adding gas to it to compensate.

In what scenario would you need 40# worth of BC lift?

 

[orange_diver]

perhaps if there's a major flood in the drysuit? let's say it happens at the beginning of the dive when i have all the gas weight. let's say i have 26lb of lead, variously distributed. i really dont know how much extra weight that flooded drysuit would add, but a 30# wing may not be enough to lift it.

of couse, i'd be swimming it up and have some of that 26lb as ditchable as a worst case scenario, so that may be a moot point.

i don't know if i'd need 40#, that's why i'm here. ; )

30# is better as i'm trying to get the most streamlined possible. let's go the other way, then, would a 26# wing be enough?

 

[ScottB]

I do not drive a drysuit.. so forgive me if I am wrong.. but my understanding is that

Flooding a drysuit does not *add* weight, it *removes* buoyancy by removing the air which is inside...

The only *weight* of the drysuit is the material itself.. so if you can calculate it's inherent buoyancy.. or just assume it's dry weight as negative buoyancy it will give you safety factor...?

Having the ability to add air to the dry suit would act as a safety in the event of the wing failure, but if your wing can support you, the negative buoyancy of the suit material itself (if it is even negative), the weights you add to compensate for the buoyancy of the air in your drysuit, a full tank, and any other stuff you carry... then it is large enough..

Right?

Take care,