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DUI’s TLS350: The Exploration Suit of Choice

By David Sweetin
©DirQuest Vol. 3, No. 2 – Summer 2002

DUI TLS dry suit - modifiedOkay, I know what the website says,” he whispered, “but really, just between you and me, when you’re diving for fun, what drysuit do you really wear?” Glancing quickly over each shoulder, I motioned this inquiring mind closer and whispered, “TLS350, just like it says. Always train the way you race.”

This pearl of wisdom, relayed to me early on in my journey toward DIR, has proven its value to me time and time again. To be truly prepared to contribute safely and efficiently to any team endeavor, one must be completely habituated to every element that impacts one’s diving performance. Without a doubt, the fastest route to achieve this is to always dive configured the way you will be configured on “game day.” As the old adage says, “practice makes perfect.”

Judging from his expression, this was not the answer he was hoping for. Sadly, he is not alone in this reaction. This question, as well as the inevitable disappointment that ensues when this question is answered sincerely, by someone adhering to DIR principles, seem to surface quite regularly; as if “personal” dives do not require one to bring the same skill set or equipment choices to the water as do project dives. What is odd about this belief is that it assumes that one’s skill set or familiarity with equipment can be honed in some other environment other than the one that the individual is engaged in daily.

Diving in the Woodville Karst Plain requires preparation, precision, excellent timing and scrupulous attention to schedules and logistics. To meet project goals competently and safely, preparation and training are constant, and measures and equipment standardized. As a support diver for the WKPP between 1998 and 2000, my duties often included those of Surface Manager. In that role, while working to coordinate the needs of gas divers with the efforts of support divers, I was forced to address a number of key issues. One of these orbited the use of drysuits.

The suit of choice for divers of the Woodville Karst Plain Project (WKPP) is Diving Unlimited International’s (DUI) TLS350 Trilaminate drysuit. Though this suit is not “required” to participate in the WKPP, it has emerged as the ideal suit choice for divers undertaking exploration dives in this demanding environment. Project requirements, announced in mid-2000, and set in force in early 2001, simply mandated that divers use:

1) 400G Thinsulate (Type B) undergarments
2) Drysuits whose material was not subject to varying buoyancy characteristics depending on depth.

WKPP support divers were most affected by this decision. Gas divers were already using the TLS350 along with 400G Thinsulate. What struck me most about the suits the WKPP gas divers were wearing was how well fitting they were. Compared to divers I would encounter at random dive sites, WKPP gas divers looked as if they were wearing a second skin. This observation triggered in me a desire to gain a better understanding of this suit and of the WKPP’s leadership decision.

Beginning in the early 1990s, Bill Gavin, Parker Turner, and several other notable WKPP divers of the day logged many successful dives on the TLS350. Although not adopted outright by the WKPP at that time, George Irvine, former Project Director, promoted the use of the TLS350 and helped facilitate the production of a drysuit that would assist the diver’s efforts underwater; the final result of which was the “Cave Cut” version of the TLS350.

What were identified as the most desirable features of a drysuit were: that it was a well-fitting suit (that it promoted streamlining and efficiency), that it allowed a full range of motion, that it afforded appropriate insulation, and that it was of Trilaminate construction (which made it durable, lightweight, fast-drying and displayed consistent buoyancy characteristics). DUI’s TLS350 met all these criteria.

Other drysuit alternatives did not meet the needs of long-range exploration. For instance, neoprene drysuits lost their insulation properties with compression, were subject to marked buoyancy changes, and were notorious for leaky wrist seals. Quite common in north-central Florida, neoprene drysuits were an effective, low-cost option, considered “disposable” among those who used them regularly, due to a relatively short service life. Adding to their popularity was the convenience that they did not require a diver to wear an insulating undergarment. Another option, vulcanized rubber suits, was also not good choices. Though one could wear appropriate thermal protection, such suits exhibited excessive drag, were notoriously difficult to swim, and alteration from stock was not available. Hence, Trilaminate suit material became the obvious choice, being basically comprised of a union of three layers: Nylon/Butyl rubber/Nylon.

Intended as a material for use in chemical warfare, Trilaminate suit material now sees use in a variety of styles and applications. This material was intended to be lightweight, to require little maintenance, and to be easily patched or otherwise repaired. The first use of this material for drysuits was developed by Typhoon International (UK) in 1976. Since the release of the first TLS350 in 1983, Diving Unlimited International (DUI) has found favor with many groups of demanding divers, from Military Special Forces (Combat Swimmers) to the US Coast Guard and the Secret Service.

Early combat swimmer suits were typically of the vulcanized rubber type, which, although tough, exhibited poor swimming characteristics. While the military searched for a more suitable alternative, an actual swim test was needed to quantitatively compare the vulcanized rubber suit to new designs. The test required swimmers to don their respective suits, and swim a measured distance in a specified time. The TLS350 faired very well with respect to self-donning and “swimmability.” Interestingly enough, the features that made this suit desirable to military divers and search and rescue teams made it desirable to the WKPP.

LIGHTWEIGHT AND FLEXIBLE

As a much thinner material, intended simply as a barrier to the water, TLS material is lightweight. With the addition of an undergarment, warmth is assured, and affords the diver excellent flexibility.

“SWIMABILITY”
The TLS’ telescopic torso design yields a suit that is both streamlined and self-donning. It allows enough material to be available for a full range of motion without at the same time promoting drag. Because fabric suits do not stretch as much as neoprene suits, if there is not enough material available, the diver’s range of motion will be restricted. Also, to ensure longevity while still maintaining a full range of motion, the number of seams must be kept to a minimum. This requires a careful balancing act. Utilizing Special Production (i.e. Cave Cut) or appropriately sized stock suits, a proper fit can be achieved, allowing a diver to have the most streamlined and “swimable” exposure protection possible while incorporating sound thermal protection.

Turbo soles (which allow for the use of rigid, non-split fins), proper pockets, a p-valve (where needed) and a proper valve/inflator fitting, rounds out the desirable features of this flexible drysuit. These were some of the reasons why this easily maintained, lightweight, easily-drying TLS350 was an obvious choice for WKPP divers.

No treatment of the TLS350 would be complete without looking at DUI’s modification of this classic design. There are essentially two major modifications: the “QuickZip” and the “ZipSeal.” The “QuickZip” is, essentially, an adjustment and repositioning of the diagonal zipper. It allows divers greater ease in donning and removing the drysuit. The “ZipSeal” is likely to find great success in rental and recreational dive applications, as it accommodates instant changes of latex seals. Multiple sizes can be fitted to a single rental suit, ensuring a proper fit and a warm, comfortable dive. Recreationally, ZipSeals allow divers to immediately change a damaged seal at the dive site, substantially decreasing the risk of missed dives due to seal failure. For divers operating in extreme environments, the use of ZipSeals may be more debatable, as the integrity of their exposure suit outweighs the value offered by the ability to easily exchange seals.

RECOMMENDATIONS FOR FITTING A TLS350 “CAVE CUT” SUIT

To many, the “Cave Cut” remains somewhat of a mystery. This is not unusual as DUI is still at work refining this idea. However, before deciding on a suit, it is vital to recognize that not all divers require Special Production “Cave Cut” suits. Larger divers, and divers with above average muscularity, may, because they are more difficult to fit, given the relationship between surface area and volume. This is because a flexed muscle sees volume increase by the cube, while surface area increases by the square. In real terms, this means that to maintain a full range of motion, the suit must be cut to allow enough material to complete that motion, without contributing to drag.

Many people find a stock suit that fits them. However, for a proper fit, be prepared to spend a few hours trying on suits and undergarments. One common mistake I see divers make is that they will spend the time to be properly fitted for a drysuit, but blindly order an undergarment that they have never tried on. In some cases where a diver experiences a restricted range of motion, the actual culprit is not the suit, but rather a poorly fitting undergarment. In the end, time invested in sizing pays off.

If a diver needs to order a special production drysuit, he or she should find a competent measurer. Often people fail to grasp the instructions or fail to follow them; in other cases they do not measure enough to maintain the skill. In any case, the result is a disaster. Because there are six critical measurements (chest, waist, hips, floor to crotch, girth, spine to wrist), any mistake here can render the resulting drysuit impossible to repair; hence the need for an experienced measurer. I’m convinced that experience with this sort of thing plays an important role in producing a properly fitting suit.

Divers should play an active role in their fitting. They should read and understand the measuring instructions and be aware of what is going on during the measuring process. As a measurer, I read the measuring instructions aloud to ensure my accuracy and to ensure that the customer fully understands what I am doing as I measure his or her suit.

Divers should try on stock suits and undergarments. They should then make notes as to how they fit (or do not fit) and pass those along to DUI. If a facility does not have stock or rental suits on hand, I would not consider them “experienced” DUI dealers. As such, the measurements a diver gets from someone of limited experience will be highly suspect.

At all times, someone being measured should stand with his or her feet at a comfortable shoulder width, and look straight ahead, not at the measurer.

The person being measured should be barefoot when he or she is being measured. He or she should then have the measurer trace and measure the resulting foot tracing, and write the measurement on the tracing. The tracing should be submitted with the measurement form. The diver’s shoe size should be noted on this tracing.

The person being measured should wear form-fitting clothes, something they would normally wear at the gym, or on a run.

DUI will require a signed non-standard suit waiver.

RECOMMENDED TLS350 SPECIFICATIONS:

  • Standard Latex Seals
  • “Turbo soles”: CF 200 boots with molded sole. To ensure proper fit try on several suits with the appropriate undergarment boots.
  • Pockets: Standard Velcro Bellows (Left side), Standard Utility Pocket (Right Side)
  • Valves: specify which you prefer: Swivel Apeks inlet valve and older Apeks, High profile dump valve
    SiTech inlet (recessed button) and exhaust valve
  • “Tough Duck” overlay material (available in various colors)
  • Balanced P-valve (where appropriate)

Also Read:
Drysuit Dump valves – An addendum to “The Exploration Suit of Choice”