Weighting the key to Trim, Comfort and Safety

I have recently been asked for my opinion and advice on weighting and weighting systems. When it comes to deciding on the weight that you need is falls into main areas: The Amount of Weight, needed to offset you buoyancy, and The Distribution of Weight, for comfort, trim and emergency procedures.

How Much Weight?

During a divers education they are taught how to calculate and test their buoyancy to ensure they are properly weighted to maintain their position in the water throughout a dive. For many divers this is where it stops and only re-examine the issue if they make a kit change or dive in a new environment, and sometimes not even then.

I think weighting is a much more on-going process than this because many divers, especially to begin with, are constantly making subtle changes and modifications to their kit configuration and the way they dive until the find a system that they are comfortable with. With this in mind I define weight into 2 categories: Useful Weight and Dead Weight. Useful weight is any negative buoyancy that is offered to you through kit that you carry for another diving purpose and is permanently attached throughout the dive. This includes things like the empty weight of a cylinder (but not stage cylinders), torches and battery canisters regulators and empty BCDs and wings. Dead weight is any extra weight (lead) that we add to make our system neutrally buoyant, this could be added to a weight belt, integrated pockets or similar.

 To have the most efficient system possible we want to maximise the useful weight and minimise the dead weight. If we can do this we are then not just lifting and moving extra weight that we don’t really other than to sink. To do this when you are configuring your gear think about every item you are using, do you need it and what benefit does it offer. So if for instance if you are diving in the UK with a dry suit and you know you will need to carry more weight then why not take a larger cylinder (which will also give you more gas for the dive) and make sure it is made of steel. While doing this process don’t get too carried away by just added more kit to your set up that you don’t really need as this just becomes dead weight, and worse can lead to a greater chance of entanglement and confusion. When configuring you kit you should still always be looking to reduce waste and complexity while maintaining everything that you need to complete the dive at hand.  When working the other way to a warm environment where you will typically be less buoyant, and so need less weight, take an aluminium cylinder.

Finally when carrying out a buoyancy check, make sure you do it with an almost empty cylinder and with only items that you always carry and are not disposable. This will give you the minimum weight that you will need to carry even at the end of your dive when you will be the most buoyant.

Weight Distribution: Trim, Comfort and Safety

At the early stages of diving getting down is the most important thing and you have more to worry about than the specific location of your weights. As you develop your diving this should be something that spend a little more time considering.

First let’s look at trim and comfort. Improving your trim allows you to move more easily in the water, reducing drag and therefore reducing your physical exertion and so reducing your air consumption.  The most efficient trim position is a flat body with your knees up in line with your body and your feet above you. To begin with this can be a strange position to be in as we are used to moving with our feet at the lowest point and not above our head. To be able to maintain this position comfortably we need to be in balance and this means having our centre of mass and centre of buoyancy in the same location.

The natural centre of mass of a person is towards the centre of the torso, for men this is slightly towards the shoulders and for women this down towards the hips.This position is the point around which we can naturally balance in equilibrium. For diving this is the point around which we want to balance our buoyancy and weights. Firstly we position all of our standard kit (tanks, Torches, BCD) around this point and should end up with relatively comfortable set up. The easiest way to start positioning weight is to start close to the centre of mass with larger weights and as you move away the weights should be smaller. This is due to the relationship of the moments around the centre.

For men typically using integrated weights or weights attached to a cylinder dives a better trim position and comfort as it is closer to his centre of mass. Women will typically find low integrated pockets and weight belt s more comfortable for the same reason. Women have another added advantage with weight belt comfort and that is their hips, or welt belt retainers, which help to keep a belt from slipping down.

For added comfort splitting weights across multiple locations (less on weight belts to reduce slipping) ensures that no one item is too heavy during kit up, it also has added benefits when it comes to emergencies which we will discuss later.

With regards to trim and comfort the last aspect is ankle weights. Many people have strong views on this and at the end of the day it comes down to personal choice. These are my thoughts on the issue. I personally am not a big fan as I believe that they have the biggest effect on trim as they provide a large moment away from the body centre which drops the feet.

I also think that they are working against you as, with a dry suit especially, the buoyancy in your feet should naturally float your feet to above your head and into a low drag position with no effort to the diver. If you become comfortable and confident with you set up then feet high orientations should not be an issue.

My final thoughts on weighting are to do with emergencies and were touched on earlier.  I strongly believe that a diver should not have their weight all in one location as it doesn’t provide many options in an emergency, you can either dump your weights or not. If you distribute your weights across 2 or 3 locations it means that if you did have a situation when you believed dumping your weights in the only option then you can dump a small amount to make you slightly positively buoyant and allow you to have a slightly more controlled ascent than just dumping all of your weight. Also in terms of diver problems I think that many could be solved before you dive by having proper weighting as it is surprising how many divers dive with wrong weights, especially too many.

I hope that this blog helped and might have sparked some new thoughts along the way. I would be happy to learn your views and opinions because at the end of the day it all comes down to personal preference.

Go Pro Hero HD – Video System and Lighting

For my brother’s last birthday (October 2011) we bought him the Go Pro HD video camera and underwater casing. We made it our mission over the winter to get the system up and running for the New Year and make 2012 a year of capturing our dives in stunning HD.

Low Light

The first issue that we faced was recording in low light conditions, which is essential for recording at depth in the UK. Our first attempt was with no lighting at all and this just left us with black. We next used a standard Tec light (Green Force LED Umbilical) which worked well for small areas but gave a limited field of vision and the powerful and fine beam left hot spots and the centre of filming. We decided to bite the bullet and get hold of a Green Force Squid 1500 lumen light which gave a fantastic result. We did find that in enclosed zero light areas that one light did give a limited picture on one side of the video and so for future dive we will be using 2 Green Force Squid lights (1 x 1500 lumen and 1 x 1850 lumen). The first attempt at the double light set up was unsuccessful as we are running them from one battery pack (Green Force Flexi 2) which due to its age the cells were unable to run both lights at the same time. We replaced the cells in the pack with cells from Strikealite and the system now runs both lights through a double umbilical with no problems at all. The system offers 1hr to 1.5hrs of constant burn time.

Focus

Our next issue was focus. At first we were getting a circular blur in the centre of the image and we first thought that this was low light related. Now we have fixed the lighting issue we have discovered that it is a tolerance issue between the case and camera. If the tolerances get too close with the goforfocus flat lens (which you need to use as the curved lenses can't focus correctly underwater) and the camera then it causes the lens to make contact with the case and then case the blue in the image due to not being able to focus correctly. We fixed this issue to using an after-market lens kit which provides large gap in front of the lens and a conversion ring to hold standard colour filters. (Oculus Lens from Thailand). To improve the depth of colour we use a magenta green water filter, from Bristol Cameras, for use in fresh water. If you want use the goforfocus lens option then you simply need to use a spacer on the front of the camera to insure the lens to case distance is maintained (with this option just make sure that the spacer is not oversized as it can case the case to leak).

Mounting

We tried several mounting arrangements from head mounting through single hand mounts to our final bespoke mounting system We have settled on our home made mounting array which holds both the video lights securely and the Go Pro Camera. The system is neutrally buoyant and provides 2 hand hols locations to help with stability. The mount also allows the double umbilical to be routed neatly and out of the way. We have also fitted the Go Pro video display to the back of the camera.

The Configuration

1 x Go Pro Hero

1 x Go Pro Display Screen

1 x Go Pro Housing

1 x Oculus Lens

1 x Bristol Cameras Filter

1 x Green Force 1850 Squid Video Light

1 x Green Force 1500 Squid Video Light

1 x Green Force Flexi 2 Power Pack (New Cells)

1 x Green Force Double Umbilical

1 x Bespoke Mount

Video with 1 Light Only (1850 lumen Squid)

                                           

Easter 2012 Weekend Swanage Dive Trip

Objective and Background

Swanage, Dorset in the UK has always had an important place in my heart, especially for diving. Swanage was where I first learnt to dive at the age of 16 and is where I always return to when there is a personal course that I want to take to expand my experience. 

Swanage was that kindled my love of wreck diving, with the Kyarra being the first large and significant wreck I ever dived. I still return regularly to dive the Kyarra but this time my brother and I want to go with the intention of using the new video set up. To try and capture the Kyarra’s magnificence over 3 dives. (Let’s hope the viz is good!!)

(For the history of the S.S Kyarra visit http://www.sskyarra.com/)

The Kyarra now lies between 24m and 32m depending on tides. It is usually dived twice a day at slack tide using DSMB for the drifting ascent as the tide really starts to run. Viz is typically best at high spring tide and worst at low spring tide. Boats run from Swanage Pier with a couple of options to choose from and air and nitrox fills available on the Pier from Divers Down the oldest UK diving school. 

(http://www.diversdownswanage.co.uk/) 

Thursday 05/04/2012

9pm - Final kit preparations and plan finalisation, pack car, charge torch (Lights for Me 7XPG) and set dive computer (VR3 OC and CCR Trimix). For information only the plan settled on is:

30m ---------40min-----------32% Nitrox

6m-----------8min---------100% Oxygen

Friday 06/04/2012

6.45am – Get up and prep for the day

8.30am – Car packed and off we go. For a bank holiday, traffic seems light and it looks like it will be a good day until problem 1!! The Tom Tom decides to freeze and thinks that for the whole journey we are still in Redditch. Never mind we know the route well. After a couple of hours all is well and we stop for the obligatory coffee and rest stop. We set off again and all is still good until we hit the bank holiday traffic of people looking to enjoy the Dorset Easter. An hour delay and much cursing of Sunday drivers, on a Friday, and we are off to finish the journey.

13.30pm – We finally arrive in Swanage to the sight of a peaceful sea and glorious sun, though slightly chilli. Our first bit of luck, there is space to park on the Pier. We unpack, catch up with a few of the local divers and instructors and get an idea of conditions. We grab a burger and chips, have a walk around the town and then head to the pier to load to boat.

15.30pm – Gear loaded, without the camera for the first dive, and we now find that we are the only divers on the boat. I wonder why!? So our private charter sets out with a couple of tag along boat riders and a dog.

16.00pm – As we head out we make final preparations to of our gear and get into our suits. Finally kitted we arrive slightly earlier than planned. We now have to wait for the slack to allow the shot buoy to pop up and mark the wreck. We wait….5….10….15….20 mins. Almost half an hour of waiting and now feeling quite sea sick the sea finally releases the buoy and we get ready to enter the water.

16.40pm – As we pull down the shot line the current is still running strong. The viz is down to a couple of meters and as we descend the light quickly disappears. By 10m I have to put on my torch or be plunged into complete darkness and easily lose my brother and we are still on the shot. We finally reach the wreck at about 23m and start the tour of the dive. We start to slowly acclimatize to the low light and the poor viz. I’m just glad that we both have good torches otherwise you could have easily found yourself alone on a hump of wreckage in the dark. As we slowly move around the wreck, almost navigating by touch, we both have to carefully check our gauges for depth as we have no visual reference and it is impossible to judge our position in the water. We float about bumping into various bits of wreckage until we finally give in and call it a day. Ian starts to put his DSMB up using its built in inflator bottle. The seal leaks like a fountain and only a dribble of air actually finds its way into the SMB. After a moment of trying to fix it we decided that we won’t be able to do it here and that there is enough air in the SMB to provide a reference line and so let it go. We ascend to our 6m stop which is amazing as there is enough actual ambient light to turn off the torches. We have no actual deco to do as we cut the dive short but for good measure I switch to my 100% Oxygen while we do our 5m, 3min safety stop. We finally reach the surface and get back on the boat. Like all good dive boats once we are de-kitted we are presented with a hot chocolate for the boat ride home.

18.00pm – We disembark, load the car and head off to our accommodation for some good food and hope for better tomorrow.

Actual Dive Details (VR3 Dive Computer)

25m ---------35min-----------32% Nitrox

6m-----------3min---------100% Oxygen

Saturday 07/04/2012

Dive Plan

28m ---------35min-----------26% Nitrox

17m ----------2min-----------26% Nitrox

6m-----------5min---------100% Oxygen

7.00am – We arrive at Swanage Pier to be greeted by grey skys and a blowing wind. We decided that due to the previous days viz that we would cancel our third dive and put the filming off to our next trip. We had a full English breakfast, walked down the beach and had a coffee.  Feeling fortified we headed back to the pier.

9.00am – I got my cylinders topped with air to give me a 26% mix. We decided that this would be fine due to the shorter dive plan and that the deco wouldn’t be too long.

10.30am – We load our gear on to the boat and things are already looking more promising as the skipper has managed to fill both boats for the dive trip, always a good sign. The weather has already started to improve and all the signs are there for a good dive. We arrive at the dive site about 5min early and just wait for the slack. With the time to spare we discuss the potential of a new building material made of Sea Gul droppings and that the skipper is in the wrong business with his dislike and frustration at divers and their kit damaging his new shiny boat J.

10.50am – My brother and I enter the water first to test the conditions for everyone else. We hit the shot and the current is only running slightly. As we descend it is obvious that the high spring tide is paying off and the viz is much better. Even as we hit the wreck at about 25m there is just enough light to see without torches. We set off for our tour. The dive was much more enjoyable and the Kyarra started to release some its magic. Large schools of fish which call it home are visible and making the dive fantastic, and at least this time you could once again tell that this was once a ship. The time passes quickly and uneventfully, even the SMB decided to behave itself on this dive. We made our ascent, completed our small decompression obligation and then waited on the surface for the boat to pick us up. We had our well-earned hot chocolate and headed for shore.

12.30pm – We get back to the pier unload and head into town for some of Swanage’s amazing fish and chips. After a full lunch we settle our bills, say our good byes and head for home. I now just look forward to our next Swanage trip and getting some filming done and also our up coming week of wrecks in Scapa.

Actual Dive (VR3 Dive Computer)

28m ---------30min-----------26% Nitrox

17m ---------2min-----------26% Nitrox

6m-----------2min---------100% Oxygen

The Real Value of Scuba Instruction

The Relationship between an instructor and student is a very special one and if you get it right it can produce fantastic results. I always find it amazing that people compare diving agencies and courses and how ingrained diving politics is from a very early start even though all the agencies teach very similar courses and skills in very similar ways as that is the best way that diving is done. This is even more amazing considering many instructors teach for multiple agencies, even the ones that they often turn you against.

Whatever the course it is only ever as good as the instructor teaching it. If you can find a good instructor then I would say stick with them. You may do courses with others as well but it is always worth coming back to the person that you trust to give you their opinion. I still keep in touch with my original instructor on a regular basis and except for my professional qualifications he has taught me every course I have ever done from Open Water to Trimix. I still to this day ask his advice and opinions on diving and we often discuss teaching methods and approaches. He has an amazing wealth of diving knowledge and teaches for PADI, BSAC, TDI and IANTD, and has always given me a balanced view on the pro’s and con’s of all these agencies. Always remember no system is perfect and depends as much on the instructor as the system they are delivering. Ask yourself this “Would the last course you were taught have been really any different if the same instructor had taught it from a different organization? Would the key facts and information have been any different?”

 I know that in the courses I teach I try to draw on the positives I have seen from all the agencies and different instructors I have trained with. I also try and work out the con’s. For example I teach the PADI system as I have always found the books and materials to be the most user friendly and accessible, however I have also always tried to include my students in an active diving group/club which I have always liked about the organisation of BSAC.

The most important aspect of learning to dive is finding an instructor to trust and makes your experience rewarding. When you have found a good instructor who can offer you the courses you need then why look elsewhere? Your instructor should be on hand to offer support and advice on diving while on a course and after it as well. They shouldn’t be there to squeeze you for every penny you have but should offer you services they think you need and they believe in.

I personally always try to get my students to get to at least rescue diver as I think the skills you learn at this level are the minimum any good diver should have. I also try and get them to book courses in blocks. This allows not only discounts,  as I can structure more efficient training, but also gives more time to explore other aspects of diving. Say you did a dry suit course, a deep course and an enriched air course. Doing them separately you get 2 dry suit tuition dives, 4 deep tuition dives and 2 enriched air tuition dives. Now if you booked them as a package all together you could have the chance to do 8 dives in which you could use a dry suit and enriched air while diving deep while still focusing on the specific skills that each dive would require for certification. You come out with 8 enriched air dives, 8 dry suit dives and 8 deep dives, now which diver do you think would be better?

The dive industry is often its own worst enemy, especially in holiday locations where they tend to “pile’em high, sell’em cheap”. Having seen instructors with 8 students in Open Water I wonder how they would cope if it went wrong. In the UK we are governed by HSE and so a much more realistic ratio of 4 students to 2 professionals is more the norm, and also the numbers I would try to offer where ever I was diving. I always think that you get what you pay for and if you pay almost nothing for tuition in life support skills then don’t be surprised if you don’t always get the quality you are looking for.

On almost all of my diving courses where I was the student, I have had a 2 to 1 ratio or more often than not 1 to 1. This meant that the attention and focus was always on me and my improvement and we could always work on the areas in which I was weakest. To get this high level of tuition and also the custom focused courses I have always paid a premium and it is a premium that I am always willing to pay. Next time you think of booking on a course don’t just look at the cost but the value. I always apply a very simple equation in any situation where I am looking for instruction:

Cost Per Min of Direct Instructor Time = Course Cost / ((Course Time (min)/Students on Course))

Let us compare2 Open Water Courses, 1 which is £450 with 2 students on the courses and one at £250 with 6 on the course. Let us say you have 20 hours of direct Instructor class time doing theory and water session.

The 2 student course:

Cost per Min of instructor time = £450 / (1200min/2) = 75p per minute of direct instructor time

The 6 student course:

 Cost per Min of instructor time = £250 / (1200min/6) = £1.25 per minute of direct instructor time

So you tell me who is getting the best value for money and who will be the better divers?

We all look to get different things from diving and I would never want diving to become to elitist that it priced out people who can experience so much from it, though I would always say get the best training that you can afford and that if it is the difference between some new shiny gear or paying a little more for your training then I always think that the training will always offer the greatest return.

Safe Diving Practice and Problem Solving Part 2 – Gas is Time, Effective Planning

Any problem is solvable with enough time, and in diving Gas (Air) is time. As long as you are breathing you can deal with what is going on. There are 2 aspects to ensure you have enough gas for any situation:

• ·         Gas Planning and Management
• ·         Emergency Procedures and Redundancy

Let’s first explore as Planning and Management. During this blog I use Gas which maybe Air, Nitrox or Trimix depending on the dive you are planning. Firstly Gas Planning. It is important to be sure that you have planned a dive that is actually possible to do. Many divers do dives that I class as ‘Suck it and see dives’, where you dive until you reach a set bar level. This is ok for shallow dives and with greater experience you can start to judge how much you breathe on any particular type of dive. However if you want a more accurate method then you can employ a technical diving method.

First you need to know how much gas you have, and with the metric system it is nice and easy.

Liters of Gas (ltr) = Cylinder Capacity (ltr) x Cylinder Pressure (bar)

For example a full 12 ltr cylinder at 230 bar

Liters of Gas (ltr) = 12 ltr x 230 bar

Liters of Gas (ltr) = 2760 ltr

The next stage is to know how much you breath, this is known as you Surface Air Consumption (SAC). To work this out accurately swim at a constant depth for 10 min and measure how much you breathe in bar and then convert this to how much you breathe at the surface:

SAC = (Pressure of Gas Breathed (bar) x Cylinder Capacity (ltr)) / (Time (min) x Pressure of Depth (bar))

For example you swim at a steady pace at 20m for 10 min and breathe 20 bar of air from a 12 ltr cylinder:

SAC = (20 bar x 12 ltr) / (10 min x 3 bar)

SAC = 240 / 30 = 8 ltr/min

Another way to calculate a quick average SAC is to take the average dive depth from your computer and use the total gas pressure used through the whole dive and the total dive time.

For example your average depth is 15.5m and the dive was 40min. In that time you breathed 80 bar from twin 12 ltr cylinders (24 ltrs total):

Avg. SAC =( 80 bar x 24 ltrs) / (40 min x 2.55 bar)

Avg. SAC =1920 / 102 = 18.8 ltr/min

Now you know how much gas you have and how much you breathe you can work out how long you can dive with redundancy gas left for emergencies. In Tech diving we use the rule of thirds: 1 third to dive away from the entry point, 1 third to get to the exit point and 1 third in reserve for emergencies.  In No Decompression diving people tend to plan to leave around 50 bar in the cylinder at the end of the dive. Whatever safety margin you decide it should reflect the type of dive that you are on. Here is how to calculate how much time you have on a dive. First work out how much gas you have and the amount of safety margin you want and then divide the useable gas by your SAC at depth.

For example you have a 12 ltr cylinder with 230 bar and you are planning a 20m dive and you know your SAC is 18 ltr/min. You want to end the dive with 60 bar how long can you dive for.

Cylinder Capacity = 230 bar x 12 ltr = 2760 ltr

Safety Margin = 1 – (Reserve Gas Pressure / Start Gas Pressure)

Safety Margin = 1 – (60 / 230) = 0.74

If you are using the Rule of thirds the Safety Margin is always 0.67

Gas for the Dive = Capacity x Safety Margin

Gas for the Dive = 2760 x 0.74 = 2042 ltr

Max Dive Time = Gas for Dive / (SAC x Depth Pressure)

Max Dive Time = 2042 ltr / (18 ltr/min x 3 bar) = 2042 / 54

Max Dive Time = 37.8 min

Obviously this s an average dive estimate so if you will be working harder than normal then account for this by increasing you SAC. In a stressful situation it is easy for a SAC rate to double if not triple!

If you use this set of rules then as far as a dive plan goes you should never run out of gas. During the dive is when gas management becomes key. You need to keep a regular check on you SPG throughout the dive and have a set turn pressure at which you will end your dive. Also you should be able to tell if you are using your gas more quickly than expected and shorten your dive accordingly. Trust me, no dive is ever that good that it is worth pushing past your planned end gas pressure. 

Safe Diving Practice and Problem Solving Part 1 – Know Your Limits

One of the most important skills a good diver needs is to be able to handle and solve any problem that arises underwater. This then allows then to make a controlled and safe ascent to the surface to dive another day. Most major problems arise due to a series of lesser problems, which after a point can really leave you in it. For example running out of air is caused by not checking gauges often enough, not having enough gas for the dive you have planned (depth or time), not properly maintaining kit (free flows) and being too far away from your buddy or not having a redundant air source. All of these are simply solved problems that can result in catastrophe.

The above diagram (the Pit of Despair) shows the chain of events that can lead to a lung overexpansion injury, one of the easiest diving injuries to avoid.

This part of problem solving is going to focus on knowing your own ‘Personal Limits’. All divers should be aware of how good a diver they are and the point at which they start to feel outside of their comfort zone. Don’t kid yourself; we all have limits and points at which we are no longer comfortable (these may also change from day to day, dive to dive). Know these limits and stay within them.

The easiest limit you can identify, and yet the one most often broken, is that of certification and depth. This limit is stated in black and white on your certification card and diver training. To an Open Water diver you might not see the difference in diving to 30m over diving to 18m or a deep diver the difference in diving to 50m over 40m and some of the time there might not be a noticeable difference.   However, you haven’t had the training to plan a dive beyond your qualification and how to deal with the situations when it goes wrong. Think back to your Open Water course, you spent most of the time learning what to do if it goes wrong:

• ·         You run out of Air
• ·         Your Mask floods or comes off
• ·         You lose your Regulator

Diving itself is pretty easy and very enjoyable when it is going right. You swim around, breath and look at some amazing sights, but when it goes wrong you need to know how to deal with it. Trust me a problem at 50m is much different to that at 40m and at 30m it is very different to that at 18m. So first of all to be a good and safe diver able to deal with problems know and stick to the limits of your certification and experience. Remember they are not targets to be met but limits to be adhered to, this means a newly qualified Open Water diver should build up to 18m and not make it your first unaccompanied dive after certification .The same goes for whatever level you might be. Think of the limit set on any certification you get as the limit for an experienced diver of that level. 

Scuba Spud Blog Introduction

Scuba Spud Introduction

I am a scuba diver who first took to the water in 2002. I became a diving professional in 2008 and have been teaching people to dive ever since. This blog is a gathering of my thoughts and feelings on scuba diving and also how I think that it should be approach at all levels. I do not profess myself to be a world expert and the views and opinions here are drawn from my experiences as both a recreational and technical diver. I have had the pleasure of diving with and learning from a large number of different instructors and training agencies throughout my diving career. In this blog you will also find points where I have drawn upon my experience as a Martial Arts Instructor and Mechanical Engineer as these all influence the diver that I am today.

I hope that you enjoy reading my work and I am always open to comments, discussion and input from people who are also interested in expanding their knowledge of the subject.