Wreck and Cave

DUI suit features

The information on this page is not specific to the DUI TLS350, but it is in our opinion the most versatile drysuit in the world today. It is well fitting, allows a full range of movement, and is extremely hard wearing. We’re going to talk through the features of this suit, and explain why it is such a good choice.

Front entry zipper and protector

Dry sealing zippers are expensive items. Therefore the shorter you can make the zip for a dry suit, the cheaper it will be to manufacture. As a consequence, the back entry drysuit is a popular choice as it requires a shorter zipper. The downsides are unfortunately are many, and often unforseen. Firstly, the stiff zipper across the back reduces the mobility of the diver and can limit the divers ability to reach valves - a vital requirement for all divers. Secondly, the ability of a diver to dress themselves is compromised. We’ve all seen divers being zipped into and out of their own suits.

DUI suits come with the option of either a back entry or a front entry (self donning suit). Here at Wreck and Cave we strongly recommend the self donning version, the same as we use in our own diving. The DUI self donning suit comes with a zipper protection layer, incorporating a second, regular, zipper. This protects the dry zip from abrasions in and out of the water.

Braces

Everyone who has every dived a dry suit has got out of the water after a dive and, rather than completely remove the drysuit, has removed themselves to the waist. This often has the unfortunate result that the suit falls down when we walk around. Braces, attached at the belt level on the inside of the suit, allow us to walk around out of the water without tripping up on our sleeves!

Telescoping torso

The telescoping torso feature of a DUI suit is related to a self donning suit. To put these suits on, the torso of the suit needs to be a little taller than the diver, so that we can put our arms into the suit first, and then place the neck seal over our heads. Once the neck seal is in place, we are left with an excess of suit material. A DUI suit folds this material at the waist level, and constrains it using a small crotch strap.

This actually has a hugely beneficial effect, in that it allows the diver great reach and mobility as the excess material is released as the diver stretches, and then retracts as the diver relaxes. Valve shut downs will never be easier.

DUI had patents on the internal braces and telescoping torso for many years, but these have now expired. You will see these features copied on other suits, but the manufacturers rarely understand all the reasons behind their use, so they often don’t work as well as the original DUI version. Beware of cheap imitations!

Seams

Anyone who’s owned a drysuit for any length of time will know that, unless you rip a hole in it, it will eventually start to leak at the seams. DUI drysuits are glue sealed, which is much more flexible than the usual tape used on most other suits. This results in a longer lasting suit. DUI are so confident in this seam technology that they offer an 8 year warranty on the integrity of the seam. If you’re considering another brand of suit, ask if they’ll match that.

Dump valves

You put gas into the suit as you descend to eliminate the suit squeeze. So on ascent, it needs to come out right? DUI offer a range of dump valves - Apeks high profile, low profile and also the Scitech valves. All of this is irrelevant if the valve is in the wrong place. DUI suit dump valves are placed on the outside of the left arm. Not on the side, not under the arm, not in a fold of loose fabric. Dumping excess gas on ascent is then easy as the valve is always at the highest point in the suit, it floats away from the undersuit and allows a clear path for the gas to exit.

Days of bashing the dump valve to vent, wrapping your arm in duct tape to prevent it jamming the valve, standing vertically upright in the water and other such remedies are a thing of the past with a well placed dump valve on a well fitting suit.

Warm neck collar

Our bodies pump around 20% of our blood up to the head, and most of this goes through the carotid arteries in the neck. Having a cold neck is a great way to get your whole body cold. It’s why we wear scarves in winter! Underwater, a scarf isn’t really a viable option, so DUI have come up with the warm neck collar. This allows the heck of your hood to be tucked into a neoprene flap on the suit that sits over the top of the neck seal. The amount of water flushing around the neck area is dramatically reduced, and the diver remains warmed for longer.

It sounds like a gimmick, but it really does work.

DUI suit options

In addition to the standard features described above, there are a range of extra features that you can choose to have added to your suit. Depending on your application, you can add them in, or leave them off.

Pockets

An instructor once asked me if I have any trousers that don’t have pockets. I did at the time have one pair, but I never wore them, because they didn’t have pockets! I now cannot imagine having a dry suit without pockets. There would be nowhere to keep SMB’s, spools, wetnotes and the host of other things I carry with me on a dive.

DUI offer a range of pockets, but the cargo pocket is the best. It’s a very simple device, big enough to hold all the stuff you need, and the top closes with a velcro flap, meaning that it will close on its own if you forget, unlike a zipper pocket.

There is another option, and that is to add a Halcyon pocket. These are truly marvelous objects, if you can describe a pocket in such a way. There are so many nice touches. Starting with the velcro opening.

Built in to this is a small pocket, with ready-fitted attachment loops. Useful for cave line arrows, spare boltsnaps, basically anything small that you don’t want to end up at the bottom of a big pocket.

The main pocket compartment comes with bungee loops already installed. Also, a small, low profile inner pocket is included for sliding wetnotes in and out without emptying the rest of your pocket, or getting them jammed when replacing them.
These are seriously nice extras to have on your suit, and you will not regret the extra cost.

Boots

DUI offer two variants of boot. Both are low volume, reducing the possibility of “floaty feet”. The choice comes down to Rock Boots and the more traditional Turbo soles. Rock boots comprise a simple compressed neoprene sock that is attached to the drysuit. Once the suit is donned, the diver then puts on a tough outer boot, the Rock Boot. These are very tough and if you do a lot of diving involving clambering over rocky shores or rough terrain then this boot suit be considered.

The turbo sole is essentially a neoprene sock, with a stiff sole attached. It is meant to be close fitting and is designed for in-water use. Rough terrain does not suit it so well, as your foot will slide around inside the boot, which may damage the neoprene if you roll onto sharp rocks.

In water, the turbo sole is by far the best, having low volume and no laces to come undone. The rock bot by its nature is larger than the turbo sole, so some divers may find they need bigger fins to accommodate the boot.

P-valve

“P-valve”, “overboard discharge valve”, call it what you will. It enables you to urinate while in the water. This is invaluable on long dives, and has important safety value or more challenging decompression dives, as the diver can maintain full hydration, and even drink during the dives, without risking soaking the suit from the inside, so to speak. The Halcyon valve is a nice compact unit, fully balanced, and easy to use. No more crossed legs on the deco stop!

Zip seals & gloves

This is probably one of DUI’s finest innovations. The failure of a dry suit seal most often happens as the diver is putting on the suit. That generally means that the dive is cancelled until a repair can be effected. The Zip seal allows a diver to carry a spare set of seals, and simply swap one out if it fails. The technology is similar to that used on “ZipLock” bags, and the new seal can be in place within minutes. The technology extends to dry gloves as well, and it is possible to install gloves to the suit, again in a matter of minutes. The Zip seal can also be installed on the neck.

Many people are justifiably sceptical about these seals, and fear that they will leak, or worse, come apart underwater. It’s difficult to persuade that they won’t, but the true test is to try and pull a set apart. Almost impossible. They have to be removed by “peeling” the seal away from the mounting ring on the suit, and the presence of the divers wrist makes this impossible while the suit is being worn.

Knee pads and crotch pad

Reinforcement around the knees is nice for those of us that spend time kneeling on the bottom, loading up with stage cylinders and scoters, for example. Also, the crotch pad allows increased protection if you use a scooter a lot. These are nice options for a suit, and will add years to the life of a suit if you dive in aggressive environments.

I frequently get asked how much weight a diver will need for diving a particular equipment configuration. It seems like an easy question, but not many people are aware of how to select equipment, and then how to choose the correct weighting for that configuration. Most people will be familiar with the concept of carrying enough weight to hold a short stop at 6m, with very little gas in their cylinders, and with an empty buoyancy compensator. This allows a diver to hold a decompression stop in the event of having run out of gas. It essentially identifies the minimum amount of weight needed to conduct the dive, and is tuned to the end of the dive. This is an important aspect of the weighting process.

However, there is an often-overlooked aspect of weighting, and that is weighting at the start of the dive. At this point, we are at our heaviest, as we are carrying gas in our cylinders, and we are dependent on the buoyancy compensator to achieve neutral buoyancy. Should this now fail (elbow coming away from the bladder, or the inflator unit malfunctioning) we run the risk of becoming negatively buoyant. The first thing that we should do is to ensure that our BC has sufficient lift to maintain neutral buoyancy at the start of the dive. It really doesn’t need to be much bigger than that, other than to maintain decent floatation if you hang around on the surface in a swell after a dive.

It should be fairly easy to see that failures at the start of a dive can be just as concerning as running out of gas at the end of the dive. We need to be very careful in our equipment choices to avoid placing ourselves in a dangerous situation. For example, very heavy cylinders such as a set of 300Bar doubles, full of gas, would cause us a lot of trouble should we experience a wing failure. A lighter set of doubles, such as aluminium 80’s would be much more buoyant and possibly a better choice.

Another consideration is the use of wetsuits. These require a large amount of weight to sink them at the surface, but once at depth, they compress, and loose their buoyancy. Consequently, the weight we needed at the surface is now effectively “dead weight” at depth. Again, the failure of a wing may leave us no option but to ditch some of this weight. This may then make the ascent less controlled than we would otherwise like.

The combination of heavy steel cylinders and wetsuits start to become a very unattractive option.

Up until this point, the discussion has been rather subjective. I’d like now to try and be a bit more scientific about the whole thing. We can start to do some rough calculations to see how different equipment configurations would affect our buoyancy in the water at both the start and end of the dive. They way we do this is to categorise each piece of our equipment (and gas supply) as either positively buoyant, or negatively buoyant.

We need to make sure that at all points in the dive the negatively buoyant components are balanced by the positive ones. This concept is sometimes referred to as a “balanced equipment configuration”. So the next step is to start applying some real numbers to the table above to see what happens. We’ll stick with a wetsuit example for the time being.

We now need to calculate how much weight we should carry. Remember that this is done with no gas in the wing, and an empty cylinder. The Total negative buoyancy comes to 2+3=5kg, and the total positive buoyancy is 12kg.

So we need to carry 12-5=7kg on the weightbelt.

At the start of the dive, we need to offset all of the negative buoyancy (15kg). 12kg of this comes from the suit, and the remaining 3kg from the wing. This will increase at depth, to a maximum of 15kg (assuming wetsuit is compressed to nothing). So 15kg lift wing is all that we need.

OK, now we move on to looking at what happens if the wing fails at the start of the dive. On the negative side, we have: 2+3+3+7= 15kg, and 12kg of positive buoyancy.

That makes us 3kg negative, which should be possible to handle, dropping the weightbelt if necessary. Now, if this occurs at depth (say 30m), when the suit is compressed to 1/4 of its thickness, we can re-do the calculations.

Suddenly we find ourselves 15kg, negative, and only 3kg positive, a discrepancy of 12kg. This is going to be very difficult to manage at depth, and highlights the need to choose equipment with care. We can ditch the weightbelt to make us 6kg negative, but this would still be a strenuous swimming ascent. A solution could be to use an aluminium cylinder, which has a positive buoyancy of around 1kg.

This would make the negative buoyancy 3+3 = 6kg (weightbelt dropped), and the positive 1+3 = 4kg, leaving us with 2kg negative buoyancy. While not being pleasant, this should be manageable by a competent diver.

This example highlights the dangers of using thick wetuits with steel cylinders, and the working through shows you how to go about “balancing” the configuration. Try playing with the numbers and see what you get. For example, try working out what would happen if using a set of double 12L cylinders instead of a single.

You should find that it becomes increasingly difficult to manage a full wing failure as the amount of gas you carry increases. For this reason, dives utilising a drysuit for these kinds of dives is recommended. Firstly, as the dives need more gas, you are likely to be spending longer in the water, so thermal considerations begin to dictate drysuits. Secondly, a good tri-laminate drysuit will not change its buoyancy characteristics with depth, so the problems associated with wetsuit compression are eliminated. Finally, the drysuit can act as a secondary source of buoyancy in the event that you do have a wing failure at depth, and this will allow you to manage your ascent.

Lets just run that through the planning table again:

Look at the difference in the wing gas requirements - because the suit doesn’t compress at depth, the large 15kg required for the heavy suit is reduced to 3kg. You’d probably still elect to use a larger wing, purely for surface buoyancy though.

So, from this, you should be able to see the importance of correct equipment selection. Don’t go changing bits of your equipment, particularly ones that are substantially negative or positively buoyant without first considering the effect of the balance of your overall equipment configuration. Likewise, when purchasing equipment, make sure that it will work well with the equipment you currently have, and that you are not going to compromise the overall performance of your gear.

If you’re unsure about how any of this works in a real-world example, then feel free to get in touch, and I’ll try and work through the problem with you.