Lost Wing Bolt in High Current

[SgtKashim]

I'm a very new diver - this incident occurred on dive 8 for me. We were diving the Clackamas river, a relatively small river just outside of Portland Oregon. The current is quite strong, but at Big Eddy there's a swirling current where the river hits a large rock that creates a pocket of relatively slow water. Max depth is under 20 feet fresh.

I prepped my gear the night before, checking my weights, regs, tank pressure, and bp/w. Before both dives I did the BWRAF check as taught - but didn't double-check the backplate, or really modify the check for the backplate I was diving with. During Open Water we used jacket BCDs.

Dives were scheduled for 9AM and 11AM. First dive went without incident, though crossing the strong current to get to the hole was a new experience. I found a lost GoPro in the hole, and generally had a smooth ride. Crossing the current required pulling myself along the bottom using a rock - finning against it was futile.

Dive 2 started fine. I was caught a bit by the current, and flipped by the fins and bounced off a rock before I regained control. About 20 minutes in I felt a *lot* more current drag than previously. I assumed we were in a different spot, or that I was more tired than the previous. A few minutes later my buddy pointed at me, signaled problem, and indicated surface.

Apparently one of the wing nuts on my backplate came loose in the current. My tank was hanging funny, and my wing was now a sail in the current. We surfaced, swam to shore and walked back to our camp. No injuries except to pride.

Moving forward - I'm modifying a few things to prevent future incidents. First up, I'm creating an explicit pre-dive checklist, with specific points to check on the backplate. It will be written up, laminated, and put in my dive bag. I'm also going to swap the nuts holding the STA to the plate - going to NyLock instead of basic wing-nuts. This will mean I need a tool to swap anything on the plate, but I have no plans to do that any time soon. If you have additional recommendations, I'd like to hear them.



Lessons:

1 - Double check *all* of your gear. Even between dives 1 and 2.

2 - If your gear is different from the gear you trained on, modify your checks and procedures to match.

3 - If something feels wrong, thumb the dive.

4 - River current can be *INTENSE*.

 

[rongoodman]

The bolts on my rig loosen from time to time, but I can feel the tank loosen long before the bolts are actually ready to come off.

 

[sea_ledford]

Skip the nylocs and just use a lock-washer instead. Since I added those, my wing nut loosening has been non-existent. You might look into getting a more substantial hand mountable nut to replace the standard wing nut like this:
Delrin Scalloped Thumbwheels | Dive Rite

Just be aware there are different sizes of bolts, so get the correct size. There are several mfg of those handwheels, the dive rite one is just the one I looked at most recently.

You'll still have to check tightness before dives though.

-Chris

 

[covediver]

I was relatively new to BPW from a conventional BC. I had a similar experience recently where the wing nut/lock washer came loose. I have since replaced the wind not with a nylock nut and have no problems. I have also gotten back into the habit of checking them before dives.

 

[SgtKashim]

The bolts on my rig loosen from time to time, but I can feel the tank loosen long before the bolts are actually ready to come off.

In retrospect, there was some wobbling. I missed it. File that away too.

I was relatively new to BPW from a conventional BC. I had a similar experience recently where the wing nut/lock washer came loose. I have since replaced the wind not with a nylock nut and have no problems. I have also gotten back into the habit of checking them before dives.

Sounds like I'm on the right track. Based on other discussions as well - I assembled this rig vertically. It's possible I didn't actually have the bolts all the way down when I tightened the nuts - the threads might have jammed against the plate. Other discussion on this has emphasized *always* assembling a BP/W horizontally.

Skip the nylocs and just use a lock-washer instead. Since I added those, my wing nut loosening has been non-existent.
...
-Chris

Hmm... Interesting. Thoughts on the plastic vs. steel threads?

 

[2airishuman]

I use a DSS single-tank wing that doesn't require an STA.

I have three twinsets. Two have plastic nuts, two have stainless steel ones. There isn't much of a difference.

 

[merxlin]

I'll chime in here re Delrin thumbwheels. I will admit to the same lack of check prior to my dive as it was not the first dive of the day. It was actually the second dive of the second day of a 3 day trip (dive 6 for this trip). The boat we were on (88ft) had a fairly high bow gate, so we were doing 10ft-12ft giant strides into the water. Quick surface check with my buddy and down the anchor line we went. Rig felt a bit wiggly but not enough to stop our decent. At about 70ft we hit the reef and as I turned my tank and wing came apart (tank and bands were on an STA- wing sandwiched between the plate and STA/tank). My buddy came over and grabbed my camera to free up my hands. I cradled the tank under my right arm, and used the inflater hose to control the wing as we made our accent up the anchor line. I was in a drysuit so used that for buoyancy, just had to raise the left shoulder to vent it as needed.

I am not sure why they let go. They were checked when the rig was packed to head to the boat. A few theories: 1) they had come loose on the wing and that last entry gave the wing enough leverage to pull them apart. Once loose they worked off completely. 2) I over-tightened them and stripped them. It just took that long to come apart. 3) someone else on the boat really liked them and removed them from my rig. I didn't notice and jumped in without them. (OK- a long shot).

I replaced them with wing nuts and lock washers, then Nylocs once I got home. No one I know and talked with has seen the Delrin knobs fail so my best guess is option 2 (operator error). That said, I'll stick with nylocs (I swapped out the wing nuts as I rarely take the wing off). No issues since.

FYI- there is a dive site off Big Sur now called Wing Nuts.

 

[sea_ledford]

Hmm... Interesting. Thoughts on the plastic vs. steel threads?

I don't actually use them, I just stick with the standard wing-nut (and keep a bunch of spares).

If you use an STA, that might also be a contributing factor. Especially the one piece ones put the tank a little bit further of the back so rolling side to side has more leverage to wiggle things loose.

I used a rental unit once when diving the Spiegel Grove and the every time I'd roll a little one way or the other the STA would bang back and forth. It was driving me nuts before I even got to the bottom, so I had to take off my gear and re-tighten. I can't imagine letting it go long enough that the hole thing would fall apart... too OCD for that I guess

-Chris

 

[SgtKashim]

[QUOTE="sea_ledford, post: 8066662, member: 66885"

If you use an STA, that might also be a contributing factor. Especially the one piece ones put the tank a little bit further of the back so rolling side to side has more leverage to wiggle things loose.

-Chris[/QUOTE]

Worse than that, I have an STA that's been filled with lead. Great since I need to carry 32lbs for saltwater here, and putting some of that up by the tank helps me trim... but it means everything hangs heavy.

 

[dberry]

I don't need a STA with my OxyCheq wing, so the cam bands are threaded completely through the plate. I use bolts, but I thought they only matter when you don't have a tank in the rig. Otherwise the bands hold the tank against the plate trapping the wing. I don't see how the wing could flap loose with this set-up. It could only be a problem if your bands are threaded through a STA which is then bolted to the plate, no?