Posts Tagged ‘SCUBA’

SCUBA Exposure Protection

Wednesday, February 18th, 2009

In the process of diving, we are subjecting our bodies to an alien environment. This environment exposes our bodies to conditions that we are not accustom. Divers need protection in a few different forms:

  • Thermal protection: The major reason for protection is Thermal protection. Keep in mind that water conducts heat 25 times faster than air. In air, our bodies would be warm at 75 deg F. Underwater, most people would chill very quickly at 75 deg F. Our bodies can not tolerate a drop in temperature. Hypothermia develops after a drop of only a few degrees.
  • Abrasion protection: Rocks, shipwrecks, shells, corals can all easily scratch, or cut through exposed skin.
  • Marine organism protection: especially in tropical waters, there are many stinging organisms both on the reef, and floating in the water. Sea Urchins, scorpion fish, lion fish and a long list of others have sharp if not poisonous barbs that can easily hurt a diver.
  • Sun protection: While not as obvious, the sun in the tropics can burn sensitive skin on the deck of a boat, or even while we are snorkeling in the water.

The type of protection available breaks down into three groups:

  • Dive Skin: These provide no thermal protection, but do provide the other three. They are often made of Lycra to hold the suit close to the body and reduce drag.
  • Wetsuits: These are made of Neoprene rubber, which consists of thousands of small gas bubbles. The thicker the wetsuit, the more bubbles, and therefore the more thermal protection it provides. The thickness is measured in millimeters (mil) and varies form 0.5 – 7.0. A small amount of water enters the suit (hence the name) but the body quickly bouncy castle for sale warms this water, and the suit insulates it from the outside water. In order to work properly, they must be snug to prevent water from flushing through the suit and cooling the body.
  • Drysuits: These provide an airspace under the suit that can be inflated to provide protection. An undergarment holds the air in place around the body and reduces air movement to the highest part of the suit.

Which to use:

Since each diver responds differently to cold, it’s impossible to give an exact answer. Here are some factors that affect how much thermal protection is needed:

  • Water temp: Duh. Colder water will need more protection.
  • Depth: Often it is cooler down deep, and wetsuits will lose some of their protection as we go deeper.
  • Air temp: On an overcast day, it can be cooler in the air than under water.
  • The diver: Size, fitness, metabolism, even what was eaten for breakfast will all affect the reaction to cold.
  • Length of dive: Longer exposures will require more protection.
  • Number of dives: More dives done in a day or over a week can cool our bodies slowly.

There is no right suit for all divers under a given conditions. No one can say “you’ll be warm in a 3 mil suit at 80 deg F.”. However, here are some guidelines:

Dive skins are used in very warm water ( over 85 Deg F ). They have little to no thermal protection, but do provide a layer of protection from sun, scrapes, and stinging organisms. In tropical environments, this protection can be very important. Corals, sea urchins, and shells can cause punctures and abrasions. Also, the Caribbean sun can cause dangerous sunburn very quickly. If you don’t need the thermal protection, it’s still advisable to wear some form of dive skin.

If the water temperature is below 85 degrees, many people should consider a 3 mil wetsuit. At 80 degrees, many will wear a suit between 3-5 mil. On the other hand, some very cold people will where a 7mil suit. As the water get colder, the thickness of the suit can be increased.

Since water temperature varies throughout the year, it can be beneficial to consider layers. A 3 mil shorty can be worn over a 3 mil suit when the weather turns cold. Or, a hooded vest can be warn under a suit to keep the core warm.

Below about 60 Deg F, many people are thinking drysuit. Some will stay with a wetsuit as long as possible due to the cost of a drysuit. For longer dives in colder water, drysuits are heaven sent. With a drysuit, dives under the ice in lakes are possible. To handle cooler temperatures in a drysuit, the undergarment thickness is increased to create a larger air space around the diver. Some exotic materials are often used in the undergarment provide more thermal protection for the same size air space.

Unfortunately, when discussing thermal protection, there is no right answer. It all depends on the diver, and trial and error may be the best approach. One parting point: If you’re warm, you can flush water through the suit, or remove your hood to cool off. If you’re cold, you have to end the dive to warm up. It’s better to error toward the warm side.

What is a Rebreather?

Tuesday, January 13th, 2009

Many people see my dive gear, and ask “What newfangled contraptions is that”? Ok, maybe they don’t use the word “newfangled”, but you get the point. I dive a Closed Circuit Rebreather (aka CCR). While people think of these as “new”, they actually predate the gear we consider standard SCUBA (also called Open Circuit or OC).

History: Early rebreathers were used not for diving, but for escape. Mines and Submarines both presented situations where a compact breathing device was needed to allow crews to escape to safety. Theses were developed back in the early 1900, and produced in quantity by 1910. Open Circuit SCUBA was not commercially available until the mid 1940s.

How do they work: Let’s start with a quick review of metabolism. Our cells take in food and Oxygen (O2). These are combined to produce energy, but have a toxic byproduct of Carbon Dioxide (CO2). Our Cardiopulmonary system takes some of the O2 from the air we breath, and distributes it to our cells. At the same time it takes the CO2 generated bouncy castle for sale by our cells, and releases it into the air that we exhale. The O2 and CO2 exchanged by our lungs is actually a small percentage of the volume of gas that we breath (about 3%-5%).

On Open Circuit, when a diver inhales, the regulator provides the diver with gas (usually air) at same pressure as the surrounding water. When we exhale, the gas is vented out into the water producing the column of bubbles associated with diving.

When a CCR diver exhales, the gas is vented into a flexible chamber called a counter lung. Within the Rebreather, O2 is added back into the gas, and it is passed through a “scrubber” which removes the CO2. We then inhale the same gas which again contains the proper O2 percentage.

With OC 95% of the gas we exhale has not been affected by our respiration. It is not used. It is wasted. On CCR, this 95% is recycled, cleaned of CO2, enriched with O2, and breathed again. This allows us to make use of smaller tanks, as our O2 consumption does not change with depth.

The devil went down to Georgia, and brought a rebreather!

Monday, October 6th, 2008
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Prop and shaft

Due to a last minute cancellation, I was able to jump on Richie Kohler’s wreck exploration trip down to Savanna Georgia. Richie and Captain Dan were the crew for the trip. The passengers included Dive Marshall Bill and myself, along with a few of Richie’s students from Canada, and Arizona. The captain was a long time local fishing operator with a long list of hang numbers from 40’ to 300’.

Bill was driving down, and was kind enough to offer transportation of our gear. Since work has been nuts this last month, this allowed me a few extra days before getting underway. We met at the hotel on Friday night, and discussed the plans. We had an assortment of CCRs aboard, and a token OC diver to keep the sharks away.

In this area the slope of the bottom is very shallow, even 30 miles out the depth is only 100ft. Many of the numbers were in 40 – 80 ft. At that depth, decompression is not a consideration, and in 78 degree water, hypothermia is not either. The main issue getting back to the dive shop before it closes.

We loaded up the boat in the morning, and headed out towards Ossabaw Sound. The first set of number (known as secret spot 32) was not so secret. There was a local fishing tournament in progress, and the area was teaming with boats. One boat was anchored over the exact numbers. We moved far enough away to give the boat room, but still could see relief on the depth finder.  Richie dropped in to check it out. The ball started moving off then we saw the tell tail bubbles (never good). It turned out to be reef rather than a wreck. I was unaware that Georgia had reefs, but apparently they do, and this one had 20ft of relief. Personally, I would have jumped in to take some pictures, but the rest of the crew was looking for wrecks. The decision was made to head out for another set of numbers.

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Tied into … the anchor

To make a long story short, we hit a number of hangs before landing on a nice wreck in 45 ft of water. Of all things, Richie had us tied into the anchor which was located next to a large boiler. The wreck was covered in sponge, hard coral, and gorgonians. Navigation was easy in the 50’ visibility. Several rows of beams headed off  toward the bow. Obviously behind the boiler was the engine prop shaft, and prop. A large school of spadefish hung just above the wreck. Barracuda were here and there, often gathering into an ominous school of their own. Within the wreck, particularly the boilers were large grouper waiting for prey. My old friends the seabass were out and about, along with a few large fluke. It was odd to see them swimming around with angle fish, and trigger fish. I expected to see a few lionfish, but there were none to be found.

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An ominous looking school of baracuda

Swimming about, I found the other divers fanning in the sand near the boiler, engine and around the various wreck structures. When my camera flashed, Richie popped his head out of a cloud of silt with a brass valve in hand. Others held various pieces of porcelain and brass. I entertained myself behind the viewfinder.

Up north, we don’t often get to see wrecks with this amount of light and visibility. Shallow inshore wrecks have the light, but the vis is short. Offshore, deep wrecks have the vis, but there is little ambient light. This was a nice compromise, and I wanted to take advantage of it. The school of spadefish seemed willing to paint a picturesque background for most of the shots. The Barracuda also appeared willing to add to the shots subject matter. This was good, as the divers were too busy to model.

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A school of spadefish paint a backdrop

At the allotted time, we started up, and back to the dock. Plans were made for the next day. We cleaned our gear, and headed to bed. It had been a long day.

The offshore forecast was not cooperating, so the next morning we boarded the boat and headed north to Hilton Head. There was an inshore wreck there reported to be producing china and bottles. Upon arrival, Richie jumped in to tie us in. Again this was a shallow wreck at 30 ft with about 15 ft of relief. Had it been in the channel, it would have been a hazard to navigation. We let the other passengers clear the deck, then geared up and splashed.

According to Richie, we were tied into a winch at the bow. I’ll take his word for it, as I could not identify much. The visibility was varied anywhere from 2 feet to 2 inches. Inflatable Water Slide The skin of the ship was clear, as were the massive boilers and engine. I tried to find my way back to the props, but was unable to navigate clearly. I kept ending up back at the up line. I tried going along the skin of the ship, but kept finding myself in washouts in pitch black. (Pitch black, and 2 ft of vis is not my idea of fun.) Then I tried to go along the top of the vessel. Here there was light, and lots of spadefish. After passing the boilers, and what appeared to be the engine, I was be back over sand again.

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A toadfish I think

After the fourth attempt to find the stern, I heard the worst sound a diver can experience, the boats engines (never good). The engine pattern did not sound like a recall. Perhaps a diver had come up down current, and the boat had to go after him. This would mean that they would go off, then come back and shut down. I reeled in the line slowly heading back. By the time I reached the up line, it was clear that something was wrong. The engines had been running too long. It was also clear that there was no tension on the up-line.

I ascended to find the boat a short way off, the line had parted, and they were adrift. Once I was on the surface they threw me a line, which I quickly attached to the up-line, handed back up. I swam off and waited for the engines to shutdown. Once onboard, Dan explained the details of the incident.

Richie had used a Polypropylene (poly) line for the tie in rather than the standard nylon. Poly line has some advantages in price, and the fact that it floats. On the other hand it does not stretch like nylon, is not as abrasion resistant as nylon, and does not have the strength of nylon. Elastic stretch is good for an anchor line as it absorbs the stress of boat pitching up and down in the waves. In these rough conditions the line had overstressed and chaffed at the bow cleat, and snapped. Lesson learned.

The last few divers eventually appeared. They had varying degrees of success in the hunt for bottles and glassware. None had paid much attention to the sound of the engines.

We strapped down for the trip back to Georgia, and then broke out lunch and hops infused beverages. Richie presented an antique bottle to the captain, who mentioned mounting it with a plaque about “when the rebreathers came to town”.

With the weather picking up, Bill decided to head down to Ginny Springs for a few cave dives. some of the group decided to join him.  However, work was calling so Captain Dan and I opted to head home. Back to those NJ wrecks.

The Wreck of the Delaware – August 18th by Lee Letwin

Thursday, August 16th, 2007

by Lee Letwin:

When we arrived at Clark’s Landing Marina at 6:30 AM, the wind was blowing from the west and we knew we were not going to the Algol, 20 miles offshore. Captain Dan Bartone of the Independence II figured the Pinta was a better choice.

Leaving Manasquan Inlet and heading north, the seas were surprisingly calm but after only 15 minutes we started to get beat up and decided to turn around and head south back to the wreck of the Delaware. The Delaware was built in Philadelphia. She was built as a freighter but during the Spanish -American War was refitted to carry passengers as most of the passenger liners were being used to carry troops. In July of 1898 she left her berth on the East River and was heading to Charleston and Jacksonville. Ten miles out to sea and east of Barnegat she caught fire. All 66 crew and passengers got off safely and were rescued. The wreck, burnt to the waterline, sank two miles offshore just south of Point Pleasant while being towed back to New York by a salvage tug.

All the divers aboard the Independence II did two dives on the Delaware and we all had a great day on the water despite difficult conditions. Our crew included Captain Dan, with Dave Oldham and Bill Trent working as crew. Dave tied us into the wreck wrapping the chain on the shot line solidly around a huge chunk of metal at the bow section of the wreck. There was little chance of pulling off the wreck with Dave’s tie-in despite the conditions. Inflatable Water Slide In fact, Captain Dan sent a line to a second dive boat that showed up after us (the advantage of us being on a fast dive boat) and the two boats held tight. Bill Trent played host to everyone and prepared lunch, which was provided as always by Adventure Scuba.

While unloading our gear we talked to the crew of another dive boat docked at the same marina. They had tied into a barge, did one dive and during their surface interval while being tossed about in the waves their anchor line parted. At that point they called it a day.

Its August, and its friken Cold! SS Carolina trip aboard the Independence II

Wednesday, August 1st, 2007

The Independence II made a run out the SS Carolina early Sunday morning. The plan was to stay overnight. To make a long story short, NOAA’s favorable forecast on Saturday night, was revised when we got out there. This cut our trip short, but we still got in some good dives.

Upon arrival, Captain Dan circled the wreck a few times as his depth finder readings did not look right to him. Bill and I jumped in to find the line right beside the wreck, but the wreck didn’t look right. Over the winter, the wreck has collapsed. I recall the starboard side standing some 20-30 ft off the bottom. Now it lay almost flat. Bill was much more familiar with the wreck, and was taken back by what he saw. I guess this explains why Capt Dan was circling.Inflatable Water Slide Bill was unable to find his favorite tie-in spot, so we grabbed the closest spot that looked good. One Ling cod was either very interested in what we were doing, or very pissed that we were digging in his hole. Either way he was never more than a few inches from us during the operation.

Vis on the bottom was a clear 50ft, but dark. We tied off a our beacons. Bill signaled “let’s go swimming”, and off we went. Before long we saw some china in the sand, and started to sift through them. It turned out to be mostly shards, but Bill was able to pull out a small ash tray. I had my hands on a large piece of porcelain, but was unable to get it out from under the decking. I was not sure what it was, but it was big, and the hole I was working in was too small for it to move. My planned bottom time was running short, so I signaled Bill and headed back to the line.

Looking at my computer during the ascent, I noticed something I hadn’t before. Its 42 degrees! It’s August, how can it be 42 degrees? That can’t be right, check the backup. Yup, 42 degrees! I could still see the beacons at the first deco stops start at 160, but the thermocline starts back at 50 ft. This was going to be friken COLD. There was little to no current on the line, but the cold started to get really bad. Our work load had prevented us from feeling it on the bottom, but now it started to set in. My body was warm enough, but at that depth, Neoprene gloves lose most of their insulation. Mine are 7 mil, but just looking at them, I can tell they are compressed.

At 70 ft the temp jumped up to 44, and I can actually say it felt good. At this point I was in the surface water which had to be 100+ ft of visibility. I could see Bill’s bubbles rising out of the cloudy layers below. At 50 ft the temp rose to 52 degrees, then at 30 it rose to 78. Now I’m sweating in my suit, but it felt much better. I was a little startled when a large Mula-mula swam right by me on the line. He looked at me for a moment, then swam toward Bill. Due to the cold and workload, I stayed a few extra minutes at the 20 ft stop. I could see Bill as he passed through the thermocline some 70 ft away.

On the surface the seas had turned to 4-6, and the forecast was to get worse tonight. Some of the other divers had passed me on the line. When Bill surface, he and Captain Dan discussed the changes in the wreck at length. Dan geared up and went in. The other passengers came up commenting on the cold. Discussions of numb fingers, and cutting bottom time short. Everyone mentioned the change in the wreck. There were descriptions of large lobsters, but no one wanted to grab them with their cold hands. I guess if they had delayed their dive until we surfaced, they could have switched to dry gloves. Dan had checked out some spots of interest, and came up with a brass shirt hanger.

Other than the cold, the conditions had been fantastic! When I jumped in to pull, the sun was now higher in the sky, and the wreck came into view shortly after the beacon. I didn’t really need my light. If the surface conditions were better, I’d love to have gotten more dives in. This is a great wreck with lots to see.