*Floater*:
I sort of like this type (urethane) inner bladders because they look like you could basically repair them with a simple bike tire patch. My LCD30 also has a similar looking inner bladder and it made my DIR-F instructor gringe as he had just finished explaining that the Halcyon explorers use 400 denier nylon bladders so that they would be sufficiently puncture resistant for WKPP needs (these bladders look somewhat similar to the common outer bladders for those who haven't seen them). Admittedly the Halcyon inner bladders do look more rugged, but they also look harder to repair (though my DIR-F instructor contested this suggestion) and neither seems particularly likely to pop underwater anyway. Shifting gas inside the wing also made a distinct noise with my ex-explorer 40, which I don't recall hearing with the Torus (urethane inner bladder), though I could be mistaken as I was wearing a thicker hood when I used the latter.
Anyway I brought it up because I was hoping to hear Patrick's and Tobin's side on the urethane vs. 400 denier inner bladder issue, as well as other people's thoughts and experiences. Advantages? Disadvantages? Opinions?
Floater,
Denier is a measure of the density of fibers, but in this context denier is roughly a measure of the size of the fibers used to weave a textile. A 70 denier "Taffeta" is a much lighter weight fabric than a 200 denier "Oxford", and a 400 denier packcloth will be heavier still, but no where near as heavy as a 1050 "Ballistic"
Single bladder wings, and lift bags, Safety Sausage etc. are typically made from a nylon fabric of some denier (200-400 typically) that has a thin layer of urethane laminated to it. The urethane layer is impermiable to gas, and allows RF welding. The Urethane is on the inside, permitting a urethane to urethane weld.
Is a 400 denier nylon laminated with a thin layer of urethane a better material for inner bladders in wings? I don't think so. In my experinece the main cause of damage to wing bladders is "pinch flats" not penetrations by sharp objects. Dropping the corner of a Backplate onto a wing on the side walk of boat deck is typically the cause. In my tests the coated nylons did not perform much different from the pure urethanes.
One of the downsides of coated materials is that they do not stretch, and when a "2D" bladder is asked to fill a "3D" wing you will have some "puckers" around the edges. Think of a inflated lift bag. These puckers can imped venting.
I won't claim that a "silent wing" is necessarily a design criteria, it has been noted that some wings using coated nylon inner bladders are "noisy" My guess is the puckers are the source of this noise.
In my experience coated materials are more difficult to patch, because the urethane in on the inside of the bladder, and it may be difficult or impossible to access the repair site though the fitting holes.
The pure urethane bladders are easier to patch if necessary, as the patch and or adhesive can be applied to the outside of the bladder.
I would agree with Patrick that a thicker Urethane Bladder is more puncture resistant than coated nylons.
Regards,
Tobin
