Wednesday, 8 January 2014

HOW TO: SET UP A TWINSET - PART 2: WINGS

This article is designed to allow the reader to set up their twin cylinders based on a Hogarthian/DIR setup.  The information below is based on how I dive and how my equipment is configured (unless teaching where agency standards dictate otherwise), however other methods are available.

Overview
On my previous blog I showed you what to look for and how to setup twin cylinders as well as discussing what a Hogarthian setup and DIR is.  If you haven’t seen it it can be found here.  Now moving forward we’ll discuss wings.

Happy reading.

Wings
So what do I need the wing for; single cylinder or twins?  What size do I need?  What shape is best; horseshoe or donut?  Bungee or not?  Single or double bladders?

Firstly lets look at what you need it for.  A wing that claims to be able to work for both singles and twins generally will be far from ideal for both.  If you have a twinset wing it can only be used efficiently on twins as it will be far too wide for a single cylinder as the kidney dump will not be where one would expect it.  Instead it will be wrapped around the side of the cylinder.  If you have a single cylinder wing it may not fit and may not have enough lift for a twinset.
Halcyon 40lb Evolve v Halcyon 30lb Eclipse   
Now what size do I need?  Wings come in a variety of sizes from around 30lb – 100lb.  As a general rule a 40lb wing is fine for diving twin 12’s (plus stages).  Larger (50-60lb) wings are only for larger cylinders, say twin 15’s – twin 18’s otherwise you will get the wrapping issue as mentioned above.  A 30lb wing is fine for a single cylinder.
Halcyon 40lb Evolve v Halcyon 40lb Explorer v Halcyon 55lb Explorer
Halcyon 40lb Evolve v Halcyon 40lb Explorer v Halcyon 55lb Explorer
So what shape do I need?  Both a horseshoe or donut will work fine, however a donut shaped wing will allow gas to move around the wing much easier.

Do I need bungees?  If you use the correct size wing for the type of diving you do then bungees are not required.  Bungees are often used minimise the wing’s volume when it is not inflated.  These are not recommended for a number of reasons.  In the event the wing was punctured the gas would be forced out of the wing resulting in loss of buoyancy (in a non bungeed wing this can be managed by firstly being correctly weighted followed by the transference of gas to the other side of the wing).  Orally inflating the wing would be harder as you’re fighting against the resistance.  And finally the bungees could snag. 

Do I need a double bladdered wing?  Probably not.  Most divers use their wing as their primary means of buoyancy so in the event of a failure, the gas (buoyancy) may be lost.  Additionally if diving a drysuit the diver has another form of buoyancy, and if the diver is carrying a few kilos of ditchable weight they may be able offset the gas loss.  Remembering at this point the dive would probably be aborted and any remaining gas trapped in the wing will expand when ascending.  The other downside of a double bladdered wing is there’s extra dumps and an extra LPI which may add to confusion in a rescue, especially with a buddy who isn’t familiar with your equipment.  Some agencies though require redundant buoyancy as an agency standard on their courses so if wetsuit diving you may need to dive a double bladdered wing.  If you do, I would suggest that your second LPI is left disconnected at the inflator until you need it to prevent accidental inflation of the second bladder that could result in an uncontrolled ascent.
Halcyon 40lb Evolve v OMS 100lb Double Wing 
Halcyon 40lb Evolve v OMS 100lb Double Wing 
Finally
Is there anything else that still hasn’t been covered?  Some wings are only single skinned and by this I mean the outer is also the bladder and if torn will result in a loss of gas.  I would strongly recommend a wing that has a separate bladder with a cordura style outer.

I would also look at the length of the low pressure inflator (LPI).  It should be long enough that it comes over your shoulder, through the o-ring/bungee loop and sits just past your upper d-ring.  Any longer and it will dangle causing a snag hazard.  The pictures showing the Halcyon v OMS show this really well.

Finally I would look at the location of the dumps.  A DIR style wing just has the one located on the left hip.  It’s easy to reach and because it’s at the highest point gas will naturally vent out.  You can encourage this further by rolling slightly and pulling the dump around the cylinders.  Some wings also have a shoulder dump but I would avoid using this, as generally you have to break out of horizontal trim to use it.  The final point with dumps is that it may be worth removing the toggle from the hip dump and replacing it with a small knot.  This is to prevent the toggle from becoming trapped behind stage cylinders and operating the dump by accident.

I hope you enjoyed this article and if you have any questions please ask.  I would however always recommend speaking to an instructor about your own individual equipment requirements.

The boring bit!
All opinions expressed in my articles are my own and may differ to other instructor’s and agency guidelines; by no means are they wrong and I would not wish to disrepute any of them.  This article is for information only and should not replace proper training.

Safe diving!

Timothy Gort
BSAC, PADI & SDI/TDI diver training
l Mob: 07968148261 l Email: tim@rectotec.co.uk l