The perfect video demonstrating the complete failure of the US measurements system. In a metric system 1kg of water = 1 litre or 1,000 mls. 1 cubic metre of water = 1,000 kg. No conversions needed. Simple.
Hello PeterJulianPhotos, sorry to hear that you did not like our video. Nevertheless, we appreciate you watching it and sharing your thoughts with us. Happy diving.
Awesome video. The math behind it makes an easier start point. I tried the freshwater weight guessing game...the following week, I jumped in the saltwater Red Sea off the coast of Jeddah, Kingdom of Saudi Arabia, with 5mm wetsuit, aluminum plate, Al 80 tank, 3mm hood, 6.5 mm boots,rk3 fins, gloves 1.5 mm, and ended up with 16lb to get me down after fumbling on the surface adding weight. It all panned out at 33 ft/10meters, compressed well and enjoyed the dive. But, at 5-10" 183lbs and 10% bodyfat, the math, got me into the ballpark..and take into acct....the comfort level of a 5mm wetsuit in saltwater at 87degree water outweighs all the science and math in the world!...thanks. Constantly check your weight, and document the changes!
Good job explaining this so people can get the basics. Like you said, it's trial by error, but with the basic they can get within the ballpark. Thanks for sharing your videos with us. As usual safe Diving.
Great advice, I'm a data driven diver so I do a lot of pool sessions with tanks at 500psi/35 bar to nail down the exact weight I need given any combo of gear and single/double tanks, my little black book of dive data has all my buoyancy numbers and a lot more, and stays tucked in my logbook.
Short answer: 3% of your weight for seawater and 0.5% for freshwater, works for both imperial and metric. Add the tank effect on top of that (metric users can convert those tank buoyancies by dividing by 2.2). Might want to add for a wetsuit as well, which someone ballparked as 2 lb (~0.9 kg) per mm thickness in a comment below. Very few people are of average density, so this is just a rough guess.
@@LakeHickoryScuba I didn't elaborate, but the 3% comes from combining the numbers given in the video. With a little simplification, all the units other than the person's weight cancel out.
Glad you liked the video searching4279. A good rule of thumb is, for every millimeter of thickness, add two pounds. This again is simply a starting point. The best way to test weight requirements is a simple weight test in the water.
I really appreciate you posting this video Brian! I’ve been wanting to make the switch from a jacket style BC to a backplate and wing. You made a reference about the steel backplate weighing around 5 pounds or so. You really answered some questions that I had about how to establish proper weight with a backplate. Thanks again.
This is a great video and it really helped me get to the weight I needed set for my 7mm wetsuit in Wisconsin Lakes. However now that summer is here and the water has warmed up, I just purchased a 3mm wetsuit. Is there a quick calculation to decide how much weight to remove from going to a 7mm full suit, down to 3mm full suit?
@Lakehickoryscuba Any chance we can get your take/review of the Apeks Exotec BCD? Also thank you for sharing your knowledge. We all really appreciate it!
Hello Zhimaru, unfortunately, I do not have one here to review. I will say this though, Apex makes some amazing equipment. If I get my hands on one, I will definitely make a review for you.
I literally just took my Fluid Dynamics class so all this is pretty fresh to me. It's really interesting how you converted gallons to Ft^3. Anyhoe screenshot for sharing with the buddies. I checked your math, good video.
Hello kirbythebamf, glad you liked the video. Definitely let us know if you ever find a mathematical error in any of our videos, we will be happy to correct them. We truly believe that we should never stop learning.
That is a great question @cwilliams6884, and one that would be better answered by the manufacture. I would refer you to them. In my personal opinion, the difference between fresh and saltwater would be negligible.
Love your videos! They are informative, well presented, and get to the point without a lot of fluff Could you tell me what you mean by a plate for wait, I am unsure as to what that is? If wearing a plate works, that would be a lot easier than trying to build-up a whole bunch of lead weights on a weight belt. I will be going through all your videos since I discovered your channel! Thank you
Hello Stuart Joseph. With a Back Plate, depending on whether it is a soft plate, an aluminum plate, or a steel plate, each will weigh differently. Steel plates range between 5 to 8 pounds. Eliminating the need for that amount of weight on a rig.
@@LakeHickoryScuba unfortunately I don't know what brand they are. I was just calculating and average of 3 pounds. This just confirms what I was thinking. If I'm a pound or two heavy I don't mind. I will then adjust my weights for the following dives.
The crudest method to determine weight of a cylinder is of course put it on a scale. Just remember when you do calculations for Freshwater or Saltwater, make sure you use the right variables. Freshwater is 62.4 pounds per cubic foot and Saltwater is 64 pounds per cubic foot. In general, a diver can use an average of about 6-8 pounds difference between the two. You also have to factor in the weight of air in a cylinder as well, which will change the buoyancy characteristics of a cylinder through out the dive. In short, air weights .08 pounds per cubic foot. Hope this helps.
THANK FOR THIS PRESENTATION IS THAT THE TOTAL WEIGHT ON THE BC. OR EACH PLATE WILL BE 9LBS FOR EACH POCKET. BEACUSE WE WEIGHT ABOUT THE SAME. Thank you Happy Father Day
Thanks Jerard Washington. The weight mentioned in the video is just that of the Back Plate. The BCD weight is irrelevant as its not sufficient enough the effect the calculation.
@@LakeHickoryScuba i am looking to get a pool dive in where i can stack all my weights next to the edge of the pool and keep adding until i am down to about 500 pounds (i should have my steel 100cf tank by then) to start adding or subtracting weight.
This is a good video, but using your formula I would need just over 10 lbs. of weight, but in reality during my last salt water dive using 14 lbs of weight once my air tank hit 1,200 psi I experienced trouble staying down, when I got down to 900 lbs, I absolutely could NOT stay submerged so I ended my dive. My subsequent dive I added 2 more pounds and had no further problems. Body Fat affects buoyancy (I'm 6 ft tall and weigh 235 lbs, yes I need to spend more time in the gym), as hard as figuring body fat into your computations it needs to be in the mix.
Hello Mike, you are absolutely correct. This is why we stated its nothing more than a starting point. Doing a proper weight test in the pool is very important to get a diver's buoyancy spot on.
Great video. Just came across and will be watching many more. Weighting has been my biggest issue. Large guy, 260. Mainly Caribbean vacation diver. What are your thoughts on putting as much weight as I can on my equipment. Then only having to carry the weight of the air in the cylinder? How much lift cell do you recommend. SS backplate, trim weights on tank. Jet fins, and any other weight trying to just have no weight belt.
Great question Garth. Me personally, I dive a balance rig, with no ditch-able weights (Steel Plate-34 pound lift- Trim pouches on bottom tank strap). Unless of course I am Ice Diving, then I have so much weight on, I disperse it between my rig, weight pouches, and a weight belt. Balanced rigs take practice. You will always need enough lift to hold yourself in a positively buoyant position at the surface. You can easily use lift theory to determine how much lift you need. Dispersing weight on you rig is a simple matter of getting yourself trimmed after doing a proper weight test. I would slowly transition into this type of rig, until you feel comfortable with it. Its always better to have some ditch-able weight. The biggest concern is to never overweight yourself. Don't get too caught up on the math. Doing a simple weight test in the pool is still the most accurate way to weight yourself.
Good stuff. Trying to make universal Excel (that will nicely translate this to Metric as well :) ) but have questions. In your calculation here, what suit thickness you used? None, correct? (later will be adding 2lbs per 1mm). An additional question is, why in this table are there are values for gallon 8.34/8.55 if they aren't used later?
That's really a great explanation and I think you covered everything really well. It's just a pity that The US persist in using the Imperial system of units because that tends to complicate the math. I can understand that you're aiming the instruction at an American audience so that you've only used Imperial units in your video. Fortunately, I'm able to understand the principles you've described and make the necessary conversions to metric. Unfortunately there are many out there who either don't understand the underlying principles sufficiently well enough to do the conversion or might not want to bother to do so. Nevertheless, well done.
Thanks for the kind words DF. We actually train all of our students in both Imperial and Metric. We see a benefit in understanding both methods. As far as the video is concerned, each one of our videos takes 1-2 days to produce, so between running a Full Service Training Center, and trying to produce videos here on RUclips, we have to pick one or the other. This video came via request from another viewer, so we made the video in the Imperial system. One final note, we would rather see divers do a simple weight test in the pool then spending to much time figuring out the math behind it. And as stated in the video, this is used more just as a starting point than an exact measurement of how much weight they need. As a matter of fact, this video is not even shown to our Open Water students, only to our Perfect Buoyancy students. We stress to all of our students to never overthink Scuba Diving, but more so, simply enjoy Scuba Diving. Sometimes we get to caught up in the math and science behind it, and we lose the fun of Scuba.
@@LakeHickoryScuba Fair enough and thanks for the reply. If anything, my comment was aimed at trying to promote the benefits of a single system of measurements, but if you guys are happy with two systems it's your choice. I do find your videos informative nevertheless.
I understand exactly where you are coming from, and will admit the metric system is easier. However, due to cultural differences, I doubt there will ever be a single system that the entire world will adapt.
Hi Bryan There might be an error in your calculation. The website you reference for the lbs/gal for the average human being might have done a mistake. It says that the weight is 8,3lbs/gal witch they say equals to 1010kg/m³ but in fact it equals to 994kg/m³. All the websites I checked confirm 1010Kg/m³ and that would translate to 8,43lbs/gal throwing you calculation off. Taking you calculation for salt water the results would be 6.31lbs instead of 9,4lbs. Can you double check ? If I ask Google to translate lbs/gal to kg/m³ the results differ if I turn the question around so there might be a mistake there.
Hello Freddy Gaertner, it is completely possible that I made a mistake, but considering that we only use this formula as a starting point, the difference would be negligible at best. When it comes to lift theory, no two humans are identical. So, when it comes to weight requirements, we try to find a starting point.
Hello Leandro Chayra, in regards to wetsuits and weights, a general rule is to add 2lbs per mm of thickness of wetsuit. With Steel 80's or 100's, you should be able to look up the information from the manufacture on the buoyancy characteristics, and simply added it as a variable to the formula.
@@LakeHickoryScuba I have a new Henderson Thermaxx, that means I should plan an extra 14 pounds to start and then subtract what my steel 80 is at 500psi?
Sorry about that, we shot this video about 2 weeks ago, the night before we flew down to Cozumel, Mexico for a little bit of fun diving (stay tuned for a highlights video of that), and was limited on time. We will try to make another one using the metric system very soon.
@@LakeHickoryScuba im guessing most of your viewers are from this US so i understand. Hope Mexico treated you well! Really like the work youre doing, always some good insight. Im sure the metric crowd out there would like a video like this very much!
I will try my best to get one with in the next week shot for the metric crowd. We have several other videos are ready uploaded, they just haven't went live yet. We also have a boat sinking video, a haunted pool video and some more salvage videos coming out this week. Stay Tuned
Hello zachary holbert. In short, calculating proper weighting for the end of the dive is the most efficient way to do it. One thing that is consistent with every dive we make is, we will always end with less air than we started.
Does using a 7mm semi-dry make a difference. I have 80 lbs on you and dive Monterey so its always the 7mm and steel 100s. Does any of that make a difference?
Yes johncannuk, using a 7mm suit would make a difference. But not so much to the basic calculation. In general, we tell divers that a good rule of thumb is to add additional 2 pounds per mm of suit they wear. So in a 7mm, you would need 14 pounds.
Bryan would your weight be more accurate if you added the weight of your fins and bcd to your body weight or would the fact that they have different buoyancy characteristics change the calculations?
I know that some divers that use Drysuits have to use less weight but for example most of them use heavy rubber fins to weight down the legs cause of the air inject in.
He Chuck, that was a great question. I know my Apollo Bio Fins are 3.6 pounds and negatively buoyant BUT I don't know if that still holds true at depth?? Suits will compress at depth but I don't know if that holds true for other gear. Good question on your part.
@@roycabalo1537 I worked in a Diving Center/School that the main instructors, that was previously a professional diver, he used fins like the ones you use but from scubapro in hard rubber and he used a dry suit. Everything suffers from pressure but that's hard rubber, it maintains is negative buoayncy, if you look at a alot of dry suit divers and cave divers you will see that most of them uses those king of heavy duty rubber type fins, mostly jet fins. Not only for it's durability but also for it's weight to help keep the legs weighted cause of the hair injected inside.
All of our equipment makes a difference when it comes to figuring out how much weight we need, but some of it is very minimal, so minimal I don't even calculate it. This video was intended as a starting point for divers, then it is very important for them to use the trial and error method in a pool. Fine tuning a diver's buoyancy is achieved by doing several things. One of the most important things for a diver to do, is to relax while diving. The more you relax, the more you exhale, which is a big issue with new divers. They do not typically fully exhale out, thus they assume they have to add more weight to sink. This in return usually makes them over weighted. I look at the weight of my fins and other items as a minimal change to my overall buoyancy characteristics, and more of an assistance to my overall trim (which is different than buoyancy). I tend to wear heavy fins in a drysuit, not so much for added weight, but more so because of the requirements of the types of dives I do while wearing a drysuit. I can change fins out with out having the need to add or subtract weights. So at the end of the day, I don't consider my fins as part of my overall buoyancy. The difference they make are so minimal, I don't even calculate them into the equation.
Hey brother, I have a question that hopefully you can answer. How big of a wing (size on pounds of floatation pounds) would a person need diving with twin Aluminum 100’s, to dive a minimum 300’?
Just as a frame of reference, I dive twin 80's in Sidemount configuration, with only 10 pounds of weight while diving in a Drysuit. The wing I use only has 34 pounds of lift, and I have never had an issue with staying positively buoyant at the surface.
Ok, yes there is no problem staying buoyant at the surface with a small amount of lift. What I’m asking is, at 300’, with the compression of the air at that depth with say four tanks (2 on the back) how big of a wing do most people use to not experience the free fall, or to stay neutrally buoyant at those depths????
How much does wetsuit thickness affect your weighting. I was told to use ten percent of my body weight which is approximately 23 pounds. But using these calculation I would only need approximately 4.2 pounds.
It can changing your weighting requirements exponentially. The best method for weighting is still trial and error. Go get in a pool and play around with weights until you get the right amount.
That math is begging to integrate the gallon to cf conversion constant into the water density or vice versa into the body density, one or the other, and thus be rid of that extra calculation completely when plugging in different body weights for an answer. Solid explanation otherwise.
Hello Chris O, from a physics standpoint, yes, it does. This of course primarly only effects the diver in extremely cold waters, such as when we go Ice Diving. Another way this can effect you, is when you wear a shell based Drysuit, and thick undergarments.
So, I've been wandering around the internet and looking at the various dive weight calculators out there. I started with your formula, and after plugging my numbers into the other dive calculators, the numbers are WAY off from each other, 15-27 lbs, depending on the calculator. Are there different weight calc equations, or are they just bad calculators?
Hello Brad Scarp. The key that we want divers to take from this video is, no matter what equation or formula you use, trying different amounts of weight in the pool is the best and most accurate way to determined how much weight you need. Our formula is simply meant as a starting point. There are way to many variables to say this works for everyone. I encourage all our students to use the internet as a quick reference, but nothing will ever replace actual experience in the water.
Hello sayittrue, we can most definitely make you a metric version of this as well. Feel free to send us an email, and we will also be happy to send you the formulas we used (in the metric form). We typically teach our students both in metric and in imperial, so they are better prepared for real world diving. lakehickoryscuba@gmail.com
True, I dive throughout the world and they will look at you funny as soon as you mention PSI on your pressure gauge. Dive master in Fujeirah looked at me and said, I have no hand signals for 500 PSI ....tell me 40 bar🤷🏾♂️
Thank you for the video! By the formula you gave, I need 10.5 lbs of weight (my weight is 230 lbs). I believe by your formula this is a minimum I can go in saltwater. And if I put a wetsuit on, I need to add weight. I usually use 14 lbs if I'm in 3-5 mm rental wetsuits, but I feel like I can put less. Actually, you can invent an updated formula that would consider body fat percentage and buoyancy by gear. But as you said, it's a great starting point. Thanks!
Hello Andrey Karayvansky, as stated in the video, this is not intended to give you an exact number, but simply a starting point. In regards to adding neoprene (wetsuit), the rule of thumb is 2 pounds per millimeter of thickness.
The biggest issue with weighting calculations with neoprene is, all neoprene is different and had different buoyancy characteristics. On average, a good rule of thumb is to add 2 pounds per mm of wetsuit. So with a 3 mm, you would add an additional 6 pounds of weight after the weight you added from our calculations above.
@@LakeHickoryScuba looking back into this I personally would like to disagree, I think from person to person it can very quite a bit. Me personally, I use 6 pounds in a 5mm with 5mm hood and 7mm gloves, yet I am a skinny guy.
You make a valid point, it definitely varies from person to person. As stated in the video, this is a starting point not an exact science. In regards to the neoprene calculation, it too is just a generalized Rule of Thumb. More of a starting point than an exact science.
For some reason between Thanksgiving and Easter, I tend to be more buoyant as well. Maybe its the cold winter months and all the great cooking my wife does. LOL
Hey Brian, how are you doing today? This is an interesting subject, and one that always on my mind. I Use a 7.5mm suit since i started diving, and recently acquired a semi-dry 7/8mm wet suit (but still haven't got the chance to test it). I used in the beginning 10kg of weight , cause I weighted 68kg and the suit was thick, i tried 6 and 7 at the time and still had dificulty to keep me down or more neutral underwater, specially when i did "emergency" exercises like take my BCD with tank underwater and put it on me again. So i did a bit of trial and error and found out that i needed 10kg and i was always looked weirdly by other more seasoned divers, but that was the truth. I didn't feel overweighted cause i could dive up without the help of the bcd with no problems, cause my fins are a big longer with good propulsion and i have good legs. I had custom made some weights for me, I use long flat weights on my BCD pouch wich weights 1,75 KG x 4, 7kg in total on the BCD, and used 2 x 1,50 on my belt. Since I lost weight, now i'm at 62kg, I dropped the weight belts and use only the ones on the BCD and feels great, even when I had to "tow" a fellow diver across a 150m bay to the boat, didn't feel like they weighted me down. I still haven't tested the weights with my new 7/8mm semi dry suit so i don't know if i need to reajust but probably not, i hope, cause here we use more steel cylinders, from 10 to 12l and 250psi, but for safety the compressors only load them with around 225 and when they cool down they drop to 200 more or less. What do you think about my weight? Have a fantastic day and once again, thank you for the fantastic video. Hugs from Portugal Ronaldo
Hello VashBlaster, as stated in our video, this video was designed as a starting point for divers to get their weights in order. When you start adding neoprene to the mix, a good rule of thumb is to add 3 pounds of weight for ever millimeter of thickness. Then you would take the difference of that number and the number from the calculation and it should be pretty spot on. Trial and error is still the best method for fine tuning your buoyancy and for working on trim. Lastly, make sure you utilize your log book to document all the information so that it is easier to keep track of your weighting needs in the future. In regards to you switching from a 7.5 to a 7/8, you should still be around the same amount of weight. As long as you can swim up from any depth, without having to ditch weight, then I would agree that you are not over weighted.
@@LakeHickoryScuba Yep, I can swim up and down and come to the surface at this moment. I just have to wait and see for the next season to start diving and try the new suit!
Hello Tommy Strid, we have been asked multiple times to reshoot this video in metric instead of imperial. I will see what we can do for you. Stay Tuned.
No worries, we completely understand. When it comes to training, we ask our students during their first day of class whether they would prefer to learn the Metric or Imperial system. Some ask to learn both, so we teach both. At the end of the day, it doesn't really matter to us which system is used. They both work, and we feel that by teaching both it better prepares new divers.
Awesome video! It's nice to have a full explanation for all the numbers I've been given for weighting during diving
Thanks Anthony, glad you liked the video.
This is incredible. Thanks for sharing. I can’t believe it took me 5 years to finally find a good, science based explanation/starting point
Hello kero shen, glad you liked the video and found it helpful.
I'm glad the shop survived covid. Good information on this video. Stay safe
Hello Lawrence Stark, we feel very blessed to have survived Covid. We actually stayed very busy during Covid on the Salvage side of our company.
Thank you so much! I would love to see more on physics and scuba
Hello francis bevacqua, we have an entire series on scuba diving physics.
The perfect video demonstrating the complete failure of the US measurements system. In a metric system 1kg of water = 1 litre or 1,000 mls. 1 cubic metre of water = 1,000 kg. No conversions needed. Simple.
Hello PeterJulianPhotos, sorry to hear that you did not like our video. Nevertheless, we appreciate you watching it and sharing your thoughts with us. Happy diving.
You teach it well and simple ! To the point and you don’t waste my time like other RUclips videos. Thanks!!
Hello WhazUpMike, glad you liked our video and found it educational.
Awesome video. The math behind it makes an easier start point. I tried the freshwater weight guessing game...the following week, I jumped in the saltwater Red Sea off the coast of Jeddah, Kingdom of Saudi Arabia, with 5mm wetsuit, aluminum plate, Al 80 tank, 3mm hood, 6.5 mm boots,rk3 fins, gloves 1.5 mm, and ended up with 16lb to get me down after fumbling on the surface adding weight.
It all panned out at 33 ft/10meters, compressed well and enjoyed the dive.
But, at 5-10" 183lbs and 10% bodyfat, the math, got me into the ballpark..and take into acct....the comfort level of a 5mm wetsuit in saltwater at 87degree water outweighs all the science and math in the world!...thanks.
Constantly check your weight, and document the changes!
Thanks James Battle, glad you liked the video, and that you found it helpful.
You lost me at cubic foot… (speaking as a metric guy) :). But thanks for sharing I will look for metric version 😅😅
Hello R M, we have had a lot of request for a metric video on this topic.
Good job explaining this so people can get the basics. Like you said, it's trial by error, but with the basic they can get within the ballpark. Thanks for sharing your videos with us.
As usual safe Diving.
Thanks divindragon, glad you liked our video.
An excellent, presentation starting point to figure out the beginning diving weight. I will be reviewing this video again.
Hello Bernard, glad you liked our video, and that you found it helpful.
It always hurts my brain to see calculations like this done in imperial rather than metric units :D But thanks for the video :)
Hello m1ch4Lko, sorry to hear about your brain condition. Glad you liked the video though.
Great advice, I'm a data driven diver so I do a lot of pool sessions with tanks at 500psi/35 bar to nail down the exact weight I need given any combo of gear and single/double tanks, my little black book of dive data has all my buoyancy numbers and a lot more, and stays tucked in my logbook.
Thank You, glad you liked the video.
Short answer: 3% of your weight for seawater and 0.5% for freshwater, works for both imperial and metric. Add the tank effect on top of that (metric users can convert those tank buoyancies by dividing by 2.2). Might want to add for a wetsuit as well, which someone ballparked as 2 lb (~0.9 kg) per mm thickness in a comment below. Very few people are of average density, so this is just a rough guess.
Hello Paul Billings, that's definitely one way to think about it.
@@LakeHickoryScuba I didn't elaborate, but the 3% comes from combining the numbers given in the video. With a little simplification, all the units other than the person's weight cancel out.
Sounds good.
Thanks for that ! Now to add for the suite.
Glad you liked the video searching4279. A good rule of thumb is, for every millimeter of thickness, add two pounds. This again is simply a starting point. The best way to test weight requirements is a simple weight test in the water.
I really appreciate you posting this video Brian! I’ve been wanting to make the switch from a jacket style BC to a backplate and wing. You made a reference about the steel backplate weighing around 5 pounds or so. You really answered some questions that I had about how to establish proper weight with a backplate. Thanks again.
Hello Kenneth, glad to know our video was helpful to you.
Excellent explanation. Thank you very much. Very clear. Can you perform a calculation in metrics ?
Hello Leonel Nava, we can most certainly do it in metric for you.
Metric make these calculations so much easier
Hello RUclips user, alot of divers feel the same way.
@@LakeHickoryScuba not divers, anyone who does maths. Fact not feeling. That’s why the rest of the world uses it.
@@LakeHickoryScuba ruclips.net/video/hid7EJkwDNk/видео.html
Thanks for sharing your thoughts with us RUclips user.
Great teaching! I'm headed back in to the water in a couple weeks and this was an awesome refresher, especially with my newly added Corona 24ish!
Thanks Leandro Chayra.
Best explanation I've seen for weight. Thanks.
You're welcome Steve Michel, glad you liked the video.
Very good explanation. Thank you
Glad you liked the video @Charley1973.
This is a great video and it really helped me get to the weight I needed set for my 7mm wetsuit in Wisconsin Lakes. However now that summer is here and the water has warmed up, I just purchased a 3mm wetsuit. Is there a quick calculation to decide how much weight to remove from going to a 7mm full suit, down to 3mm full suit?
@Lakehickoryscuba Any chance we can get your take/review of the Apeks Exotec BCD? Also thank you for sharing your knowledge. We all really appreciate it!
Hello Zhimaru, unfortunately, I do not have one here to review. I will say this though, Apex makes some amazing equipment. If I get my hands on one, I will definitely make a review for you.
I literally just took my Fluid Dynamics class so all this is pretty fresh to me. It's really interesting how you converted gallons to Ft^3. Anyhoe screenshot for sharing with the buddies. I checked your math, good video.
Hello kirbythebamf, glad you liked the video. Definitely let us know if you ever find a mathematical error in any of our videos, we will be happy to correct them. We truly believe that we should never stop learning.
@@LakeHickoryScuba you can call me kirby
Sounds good Kirby.
are those cylinder buoyancy weights accurate for fresh and salt water? thank you
That is a great question @cwilliams6884, and one that would be better answered by the manufacture. I would refer you to them. In my personal opinion, the difference between fresh and saltwater would be negligible.
Love your videos!
They are informative, well presented, and get to the point without a lot of fluff
Could you tell me what you mean by a plate for wait, I am unsure as to what that is? If wearing a plate works, that would be a lot easier than trying to build-up a whole bunch of lead weights on a weight belt.
I will be going through all your videos since I discovered your channel! Thank you
Hello Stuart Joseph. With a Back Plate, depending on whether it is a soft plate, an aluminum plate, or a steel plate, each will weigh differently. Steel plates range between 5 to 8 pounds. Eliminating the need for that amount of weight on a rig.
@@LakeHickoryScuba thank you for taking the time to answer my question
I actually need to know the difference between the 80 and 100 tank for my dives next week.
Thank you once again!
Hey Joe, what manufacture are the cylinders are you using? Most have a chart on their website that you can use to compare cylinder weights.
@@LakeHickoryScuba unfortunately I don't know what brand they are. I was just calculating and average of 3 pounds. This just confirms what I was thinking. If I'm a pound or two heavy I don't mind. I will then adjust my weights for the following dives.
The crudest method to determine weight of a cylinder is of course put it on a scale. Just remember when you do calculations for Freshwater or Saltwater, make sure you use the right variables. Freshwater is 62.4 pounds per cubic foot and Saltwater is 64 pounds per cubic foot. In general, a diver can use an average of about 6-8 pounds difference between the two. You also have to factor in the weight of air in a cylinder as well, which will change the buoyancy characteristics of a cylinder through out the dive. In short, air weights .08 pounds per cubic foot. Hope this helps.
@@LakeHickoryScuba Thanks for the extra info..
You’re welcome
Thanks again for the advice,
You are very welcome Dana Crosby.
great explanation
Thanks Thomas Tse.
THANK FOR THIS PRESENTATION IS THAT THE TOTAL WEIGHT ON THE BC. OR EACH PLATE WILL BE 9LBS FOR EACH POCKET. BEACUSE WE WEIGHT ABOUT THE SAME. Thank you Happy Father Day
Thanks Jerard Washington. The weight mentioned in the video is just that of the Back Plate. The BCD weight is irrelevant as its not sufficient enough the effect the calculation.
Thanks lots of good info from your channel.
You're welcome Andrew Hobbs, glad you liked the video and channel.
How about wearing a full 7mm wetsuit, to include hood, gloves and boots? Obviously that makes a difference in buoyancy
It sure does. As a good rule of thumb, you will need to add approximately 2 pounds per thickness of neoprene.
@@LakeHickoryScuba i am looking to get a pool dive in where i can stack all my weights next to the edge of the pool and keep adding until i am down to about 500 pounds (i should have my steel 100cf tank by then) to start adding or subtracting weight.
This is a good video, but using your formula I would need just over 10 lbs. of weight, but in reality during my last salt water dive using 14 lbs of weight once my air tank hit 1,200 psi I experienced trouble staying down, when I got down to 900 lbs, I absolutely could NOT stay submerged so I ended my dive. My subsequent dive I added 2 more pounds and had no further problems. Body Fat affects buoyancy (I'm 6 ft tall and weigh 235 lbs, yes I need to spend more time in the gym), as hard as figuring body fat into your computations it needs to be in the mix.
Hello Mike, you are absolutely correct. This is why we stated its nothing more than a starting point. Doing a proper weight test in the pool is very important to get a diver's buoyancy spot on.
I'll wager you're diving with aluminum cylinders, switch to steel, problem solved
you should make a video on how depth effected lift. as in how much lift do you need at 200' with 4 tanks. that kind of thing.
Great video idea djjoshua007. I will see what we can do.
Great video. Just came across and will be watching many more. Weighting has been my biggest issue. Large guy, 260. Mainly Caribbean vacation diver. What are your thoughts on putting as much weight as I can on my equipment. Then only having to carry the weight of the air in the cylinder? How much lift cell do you recommend. SS backplate, trim weights on tank. Jet fins, and any other weight trying to just have no weight belt.
Great question Garth. Me personally, I dive a balance rig, with no ditch-able weights (Steel Plate-34 pound lift- Trim pouches on bottom tank strap). Unless of course I am Ice Diving, then I have so much weight on, I disperse it between my rig, weight pouches, and a weight belt. Balanced rigs take practice. You will always need enough lift to hold yourself in a positively buoyant position at the surface. You can easily use lift theory to determine how much lift you need. Dispersing weight on you rig is a simple matter of getting yourself trimmed after doing a proper weight test. I would slowly transition into this type of rig, until you feel comfortable with it. Its always better to have some ditch-able weight. The biggest concern is to never overweight yourself. Don't get too caught up on the math. Doing a simple weight test in the pool is still the most accurate way to weight yourself.
you use 8.3 FW number dor Sw 64 but i think you need to use 8.55 maybe im wrong
Good stuff. Trying to make universal Excel (that will nicely translate this to Metric as well :) ) but have questions.
In your calculation here, what suit thickness you used? None, correct? (later will be adding 2lbs per 1mm). An additional question is, why in this table are there are values for gallon 8.34/8.55 if they aren't used later?
Hello Oleg Janas, these calculations were done with out any exposure protection. A good rule of thumb is 2 lbs per thickness of suit. Hope this helps.
That's really a great explanation and I think you covered everything really well. It's just a pity that The US persist in using the Imperial system of units because that tends to complicate the math. I can understand that you're aiming the instruction at an American audience so that you've only used Imperial units in your video. Fortunately, I'm able to understand the principles you've described and make the necessary conversions to metric. Unfortunately there are many out there who either don't understand the underlying principles sufficiently well enough to do the conversion or might not want to bother to do so. Nevertheless, well done.
Thanks for the kind words DF. We actually train all of our students in both Imperial and Metric. We see a benefit in understanding both methods. As far as the video is concerned, each one of our videos takes 1-2 days to produce, so between running a Full Service Training Center, and trying to produce videos here on RUclips, we have to pick one or the other. This video came via request from another viewer, so we made the video in the Imperial system. One final note, we would rather see divers do a simple weight test in the pool then spending to much time figuring out the math behind it. And as stated in the video, this is used more just as a starting point than an exact measurement of how much weight they need. As a matter of fact, this video is not even shown to our Open Water students, only to our Perfect Buoyancy students. We stress to all of our students to never overthink Scuba Diving, but more so, simply enjoy Scuba Diving. Sometimes we get to caught up in the math and science behind it, and we lose the fun of Scuba.
@@LakeHickoryScuba Fair enough and thanks for the reply. If anything, my comment was aimed at trying to promote the benefits of a single system of measurements, but if you guys are happy with two systems it's your choice. I do find your videos informative nevertheless.
I understand exactly where you are coming from, and will admit the metric system is easier. However, due to cultural differences, I doubt there will ever be a single system that the entire world will adapt.
Thank you!
You are welcome Dana Crosby
Hi Bryan
There might be an error in your calculation. The website you reference for the lbs/gal for the average human being might have done a mistake. It says that the weight is 8,3lbs/gal witch they say equals to 1010kg/m³ but in fact it equals to 994kg/m³. All the websites I checked confirm 1010Kg/m³ and that would translate to 8,43lbs/gal throwing you calculation off.
Taking you calculation for salt water the results would be 6.31lbs instead of 9,4lbs.
Can you double check ?
If I ask Google to translate lbs/gal to kg/m³ the results differ if I turn the question around so there might be a mistake there.
Hello Freddy Gaertner, it is completely possible that I made a mistake, but considering that we only use this formula as a starting point, the difference would be negligible at best. When it comes to lift theory, no two humans are identical. So, when it comes to weight requirements, we try to find a starting point.
just so im not confusing anything is it supposed to read for the steel 100 cylinder -.59 or +.59?
Hello bigval46, the steel cylinder is negative (-).
Do you have a video on calculating added weight for a new 7mm or diving with a Steel 80 or 100? Thank you.
Hello Leandro Chayra, in regards to wetsuits and weights, a general rule is to add 2lbs per mm of thickness of wetsuit. With Steel 80's or 100's, you should be able to look up the information from the manufacture on the buoyancy characteristics, and simply added it as a variable to the formula.
@@LakeHickoryScuba I have a new Henderson Thermaxx, that means I should plan an extra 14 pounds to start and then subtract what my steel 80 is at 500psi?
Correct
No metric this time? You're normally very good at showing us both
Sorry about that, we shot this video about 2 weeks ago, the night before we flew down to Cozumel, Mexico for a little bit of fun diving (stay tuned for a highlights video of that), and was limited on time. We will try to make another one using the metric system very soon.
@@LakeHickoryScuba im guessing most of your viewers are from this US so i understand. Hope Mexico treated you well! Really like the work youre doing, always some good insight.
Im sure the metric crowd out there would like a video like this very much!
I will try my best to get one with in the next week shot for the metric crowd. We have several other videos are ready uploaded, they just haven't went live yet. We also have a boat sinking video, a haunted pool video and some more salvage videos coming out this week. Stay Tuned
I didn't know why you calculated tank at 500 psi. But i got it
Hello zachary holbert. In short, calculating proper weighting for the end of the dive is the most efficient way to do it. One thing that is consistent with every dive we make is, we will always end with less air than we started.
Thanks!
You are very welcome Yevgen Skachenko.
Awsome video !!!
Thanks Daisy Duke.
Does using a 7mm semi-dry make a difference. I have 80 lbs on you and dive Monterey so its always the 7mm and steel 100s. Does any of that make a difference?
Yes johncannuk, using a 7mm suit would make a difference. But not so much to the basic calculation. In general, we tell divers that a good rule of thumb is to add additional 2 pounds per mm of suit they wear. So in a 7mm, you would need 14 pounds.
Bryan would your weight be more accurate if you added the weight of your fins and bcd to your body weight or would the fact that they have different buoyancy characteristics change the calculations?
I know that some divers that use Drysuits have to use less weight but for example most of them use heavy rubber fins to weight down the legs cause of the air inject in.
He Chuck, that was a great question. I know my Apollo Bio Fins are 3.6 pounds and negatively buoyant BUT I don't know if that still holds true at depth?? Suits will compress at depth but I don't know if that holds true for other gear. Good question on your part.
@@roycabalo1537 I worked in a Diving Center/School that the main instructors, that was previously a professional diver, he used fins like the ones you use but from scubapro in hard rubber and he used a dry suit. Everything suffers from pressure but that's hard rubber, it maintains is negative buoayncy, if you look at a alot of dry suit divers and cave divers you will see that most of them uses those king of heavy duty rubber type fins, mostly jet fins. Not only for it's durability but also for it's weight to help keep the legs weighted cause of the hair injected inside.
All of our equipment makes a difference when it comes to figuring out how much weight we need, but some of it is very minimal, so minimal I don't even calculate it. This video was intended as a starting point for divers, then it is very important for them to use the trial and error method in a pool. Fine tuning a diver's buoyancy is achieved by doing several things. One of the most important things for a diver to do, is to relax while diving. The more you relax, the more you exhale, which is a big issue with new divers. They do not typically fully exhale out, thus they assume they have to add more weight to sink. This in return usually makes them over weighted. I look at the weight of my fins and other items as a minimal change to my overall buoyancy characteristics, and more of an assistance to my overall trim (which is different than buoyancy). I tend to wear heavy fins in a drysuit, not so much for added weight, but more so because of the requirements of the types of dives I do while wearing a drysuit. I can change fins out with out having the need to add or subtract weights. So at the end of the day, I don't consider my fins as part of my overall buoyancy. The difference they make are so minimal, I don't even calculate them into the equation.
Hey brother, I have a question that hopefully you can answer. How big of a wing (size on pounds of floatation pounds) would a person need diving with twin Aluminum 100’s, to dive a minimum 300’?
Just as a frame of reference, I dive twin 80's in Sidemount configuration, with only 10 pounds of weight while diving in a Drysuit. The wing I use only has 34 pounds of lift, and I have never had an issue with staying positively buoyant at the surface.
Ok, yes there is no problem staying buoyant at the surface with a small amount of lift. What I’m asking is, at 300’, with the compression of the air at that depth with say four tanks (2 on the back) how big of a wing do most people use to not experience the free fall, or to stay neutrally buoyant at those depths????
How much does wetsuit thickness affect your weighting. I was told to use ten percent of my body weight which is approximately 23 pounds. But using these calculation I would only need approximately 4.2 pounds.
It can changing your weighting requirements exponentially. The best method for weighting is still trial and error. Go get in a pool and play around with weights until you get the right amount.
Another great video!!!
Thank You.
That math is begging to integrate the gallon to cf conversion constant into the water density or vice versa into the body density, one or the other, and thus be rid of that extra calculation completely when plugging in different body weights for an answer. Solid explanation otherwise.
Thanks Kimon Froussios.
Does water temperature have a noticeable impact on weight needs?
Hello Chris O, from a physics standpoint, yes, it does. This of course primarly only effects the diver in extremely cold waters, such as when we go Ice Diving. Another way this can effect you, is when you wear a shell based Drysuit, and thick undergarments.
Is there a way to get the buoyancy of various wet suits?
Hello Kyle Knicherbocker, not that I am aware of, other than trial and error. A good rule of thumb though is, two pounds per mm of thickness.
So, I've been wandering around the internet and looking at the various dive weight calculators out there. I started with your formula, and after plugging my numbers into the other dive calculators, the numbers are WAY off from each other, 15-27 lbs, depending on the calculator. Are there different weight calc equations, or are they just bad calculators?
Hello Brad Scarp. The key that we want divers to take from this video is, no matter what equation or formula you use, trying different amounts of weight in the pool is the best and most accurate way to determined how much weight you need. Our formula is simply meant as a starting point. There are way to many variables to say this works for everyone. I encourage all our students to use the internet as a quick reference, but nothing will ever replace actual experience in the water.
Can you do this in metric for us in Europe as most of us haven't clue in imperial measurements
Hello sayittrue, we can most definitely make you a metric version of this as well. Feel free to send us an email, and we will also be happy to send you the formulas we used (in the metric form). We typically teach our students both in metric and in imperial, so they are better prepared for real world diving. lakehickoryscuba@gmail.com
Google Conversion...saves the butthurt!
True, I dive throughout the world and they will look at you funny as soon as you mention PSI on your pressure gauge.
Dive master in Fujeirah looked at me and said, I have no hand signals for 500 PSI ....tell me 40 bar🤷🏾♂️
Thank you for the video! By the formula you gave, I need 10.5 lbs of weight (my weight is 230 lbs). I believe by your formula this is a minimum I can go in saltwater. And if I put a wetsuit on, I need to add weight. I usually use 14 lbs if I'm in 3-5 mm rental wetsuits, but I feel like I can put less.
Actually, you can invent an updated formula that would consider body fat percentage and buoyancy by gear. But as you said, it's a great starting point. Thanks!
Hello Andrey Karayvansky, as stated in the video, this is not intended to give you an exact number, but simply a starting point. In regards to adding neoprene (wetsuit), the rule of thumb is 2 pounds per millimeter of thickness.
How to calculate including 3mm wetsuit??
If you want to scuba dive in Puerto Rico I have the contract a good price!!!😉
The biggest issue with weighting calculations with neoprene is, all neoprene is different and had different buoyancy characteristics. On average, a good rule of thumb is to add 2 pounds per mm of wetsuit. So with a 3 mm, you would add an additional 6 pounds of weight after the weight you added from our calculations above.
@@LakeHickoryScuba looking back into this I personally would like to disagree, I think from person to person it can very quite a bit. Me personally, I use 6 pounds in a 5mm with 5mm hood and 7mm gloves, yet I am a skinny guy.
You make a valid point, it definitely varies from person to person. As stated in the video, this is a starting point not an exact science. In regards to the neoprene calculation, it too is just a generalized Rule of Thumb. More of a starting point than an exact science.
I need a LOT! I’m buoyant 🤣
For some reason between Thanksgiving and Easter, I tend to be more buoyant as well. Maybe its the cold winter months and all the great cooking my wife does. LOL
LakeHickoryScuba 🤣
The world uses the metric system apart from USA, dam crazy.
Hello Belinda, so to hear that our video was confusing to you, since it wasn't in the metric system.
oh ok i re watch it
Hope the video was helpful to you user-jk3fw4fv3s.
Hey Brian, how are you doing today?
This is an interesting subject, and one that always on my mind.
I Use a 7.5mm suit since i started diving, and recently acquired a semi-dry 7/8mm wet suit (but still haven't got the chance to test it). I used in the beginning 10kg of weight , cause I weighted 68kg and the suit was thick, i tried 6 and 7 at the time and still had dificulty to keep me down or more neutral underwater, specially when i did "emergency" exercises like take my BCD with tank underwater and put it on me again.
So i did a bit of trial and error and found out that i needed 10kg and i was always looked weirdly by other more seasoned divers, but that was the truth. I didn't feel overweighted cause i could dive up without the help of the bcd with no problems, cause my fins are a big longer with good propulsion and i have good legs. I had custom made some weights for me, I use long flat weights on my BCD pouch wich weights 1,75 KG x 4, 7kg in total on the BCD, and used 2 x 1,50 on my belt.
Since I lost weight, now i'm at 62kg, I dropped the weight belts and use only the ones on the BCD and feels great, even when I had to "tow" a fellow diver across a 150m bay to the boat, didn't feel like they weighted me down.
I still haven't tested the weights with my new 7/8mm semi dry suit so i don't know if i need to reajust but probably not, i hope, cause here we use more steel cylinders, from 10 to 12l and 250psi, but for safety the compressors only load them with around 225 and when they cool down they drop to 200 more or less.
What do you think about my weight?
Have a fantastic day and once again, thank you for the fantastic video.
Hugs from Portugal
Ronaldo
Hello VashBlaster, as stated in our video, this video was designed as a starting point for divers to get their weights in order. When you start adding neoprene to the mix, a good rule of thumb is to add 3 pounds of weight for ever millimeter of thickness. Then you would take the difference of that number and the number from the calculation and it should be pretty spot on. Trial and error is still the best method for fine tuning your buoyancy and for working on trim. Lastly, make sure you utilize your log book to document all the information so that it is easier to keep track of your weighting needs in the future. In regards to you switching from a 7.5 to a 7/8, you should still be around the same amount of weight. As long as you can swim up from any depth, without having to ditch weight, then I would agree that you are not over weighted.
@@LakeHickoryScuba Yep, I can swim up and down and come to the surface at this moment. I just have to wait and see for the next season to start diving and try the new suit!
@@LakeHickoryScuba Up above you stated 2 pounds per millimeter of neoprene and here you say 3 pounds, is there a reason for the change?
Can we get this in meters?
Hello Tommy Strid, we have been asked multiple times to reshoot this video in metric instead of imperial. I will see what we can do for you. Stay Tuned.
Wouldn't life be so much easier if you used a metric system? The whole world has woken up to this, but the US ..... nope
Possibly.
To hell with imperial system! Go metric!!
A lot of divers would agree with you vnoockthbrain. This is why we ask our students which way they prefer and all of our instructors can teach both.
LOL..... You displace Pi........... Nevermind, nerd joke.
Yep, 3.14. I also displace plenty of APPLE, COCONUT, and PECAN pie as well. LOL, I love that stuff.
@@LakeHickoryScuba lmao
American education, everyone
We love our education system.
Gallons? really?
Hello @theCUBE403, for the formula we use, yes.
can we just talk in metric.... can't actually relate.
Hello BlackPaw, sorry our video was confusing to you. We will try our best to integrate both the metric and imperial system in future videos.
Typical American, doing everything in gallons and feet. Seems like they never can't cope with the international metric system, IMO
Hello E. Sanchez, sorry to hear that you did not like our video. Nevertheless, thank you for watching our video and commenting, it means a lot to us.
@@LakeHickoryScuba the video was great, it's just the units that I don't agree with. I watched and actually used some of your videos as DIY
No worries, we completely understand. When it comes to training, we ask our students during their first day of class whether they would prefer to learn the Metric or Imperial system. Some ask to learn both, so we teach both. At the end of the day, it doesn't really matter to us which system is used. They both work, and we feel that by teaching both it better prepares new divers.