The two most important things about trilaminate drysuits that hardly get mentioned.

To put you out of your suspense, it’s the fabric membrane and the seam construction, yep not very sexy.

The fabric membrane is the film or coating that is actually keeping the water out, the two fabric elements are there to protect that membrane from abrasion and puncture, important but not as important as the membrane itself

The seam construction involves how the suit panels are stitched together and then how that seam is waterproofed. Obviously being well sewn together is vital but it is the tape behind it that’s keeping you dry.

There are basically two types of membrane, Breathable and Butyl and two types of seam tape, heat tape applied by a seam sealing machine and hand glued rubber tape. Here at Seaskin (Aqualand Ltd) we use both types of fabric and both types of taping. I think this gives us a very good appreciation of the options. So why do we make our DIVING drysuits from butyl trilaminate with hand glued rubber tape and our drysuits for SURFACE use from a mix of butyl and breathable fabrics with machine applied seam tape?

This information is about DIVING drysuits.

We feel that the combination of a butyl trilaminate with seams sealed with hand glued rubber tape gives you the best chance of having a dry dive over the lifetime of the suit in a word more durable.

The butyl membrane is around three times the thickness that a typical breathable membrane. This gives it a far greater hydrostatic head, a measure of its resistance to water penetration and to being punctured.

The multiple Butyl Rubber coats are applied individually to both the soft comfortable light weight inner lining, and to the heavier tough abrasion resistant outer lining. Both inner and outer linings each have approximately 4 to 6 very thin coats applied to them. Using multiple thin coats rather than a single thick coat ensures improved flexibility of the overall waterproof Butyl layers. The first coats are special “locking coats” designed to bind onto the textile offering maximum ply adhesion, with the remaining coats ensuring an optimum blend of flexibility whilst at the same time maintaining complete water impermeability. Additionally, by coating the inner and outer textiles separately, then doubling them together using heat and high pressure rollers; will ensure that should there be any weakness in either of the sets of coatings that might cause a leakage over time with heavy drysuit usage; then this cannot extend through the full waterproof Butyl membrane. This ensures that your Butyl Trilaminate drysuit will remain dry for the full useful life of the drysuit.
The Polyurethane based single layer and breathable membrane drysuits get stiffer as they age and eventually crack due to attack by the Ozone present in our atmosphere whereas Butyl rubber is impervious to Ozone attack and tend to get more pliable and supple with use.

Comparing heat tape with neoprene tape we again return to thickness of the waterproofing element, the butyl being up to seventy time thicker than breathable. The ultra-thin breathable tape membrane is vulnerable to being worn through from inside the suit as its protective knitted layer is also very thin, this often means that seam at the crutch and under arms need to be doubled taped to protect seam integrity. Additionally heat tape is made up from many layers and delamination of the tape itself is not unusual particularly in high flex areas.

So, what does this mean diving drysuits? A brand-new top end breathable suit with heat taped seams is going to feel fantastic from new because fundamentally its waterproofing components are thinner and therefore lighter and more flexible but may quickly start to let water in as the membranes breakdown, how quickly depends on many factors but it will start to have problems before a butyl/hand taped drysuit. If the breathable layers begin to delaminate then the suit is unrepairable. From the repairs that we see come in this seems to be at around 150-250 dives. Some divers think that this is okay for the suit working great straight from the box, the cost per dive being acceptable to them, at $1000-$2500 per suit many do not. If you are kitting up in very hot temperatures, I can see that breathable suits start to make a bit more sense, here in the UK just opening the zip or dropping the top half of the suit solves this issue on 99% of days.

A third approach it to make diving drysuits from butyl trilaminate but seal the seams with heat tape. Why do this? Cost and time. Heat tapes are half the price of neoprene rubber tapes and much quicker to apply. They should have a coat of adhesive applied to the suit seam before the heat tape is applied using a seam sealing machine. The heat tape still has the longevity issues outlined above. Whilst this type of drysuit construction will last longer than a PU / Breathable Membrane drysuit; it will not out last a Butyl Trilaminate drysuit with hand glued neoprene rubber taped seams.

Laying down a rubber tape covered in contact adhesive by hand is a highly skilled job and our technicians have many years of experience. Once that tape is placed and rolled down, its down for the life of the suit. This is an expensive and time-consuming process, but worth it. Some of our suits that come in for service are twenty years old with hundreds of dives completed.

Membrane A butyl drysuit may start its life slightly less flexible than a PU / Breathable drysuit, but like traditional denim jeans or a leather biker jackets become beautifully soft a supple over time. The fabric taking on folds at the back of the knees and elbows as it moulds to fit you giving many years of comfortable dry dives. That is not to say than other components like seals, boots and zips will not wear out and need to be replaced but the fabric and seams of the suit will always be serviceable.

Don’t get too hung up on stitch type and number of rows as long as it is stitched and taped and not just glued and taped (I have manged to stick my finger through to many unstitched seams!). We “twin needle” our seams, so you see two rows of stitches, there is actually a third row concealed within the fold of the seam, safely away from any abrasion. Drysuit seams do not come apart due to stitch failure.

As mentioned earlier we make drysuits using both systems, we are big fans of breathable heat taped drysuits but do not feel confident with the current fabric and tape technology to recommend them for diving applications. That may change as progress continues!

Newer Blog Post Older Blog Post Back to Blog