Homemade snorkel-bellows diving apparatus for hull cleaning

[denverd0n]

Originally Posted by OrangeCrush

...imagine you have a rigid metal pipe in a u-shape and you push the bend underwater. Where would the force be coming from to compress the air in the bend of the pipe?

Ah, but the pipe either has to be long enough that both open ends are above the water (not very useful), or the end that is under water has to be sealed (also not very useful). Unseal it -- to breathe through, for instance -- and suddenly it will fill with water because of the pressure. Now you will need pressure on the air column to push that water out.

The bottom line is that somewhere around 2-3 feet you get to be too deep to be able to breathe through an open tube to the surface. At that point the air MUST be compressed, or you WILL NOT be able to breathe it. So, again, if you are more than 2-3 feet below the surface, and you are breathing air, then you are breathing compressed air! No way around it.

[a64pilot]

Think of it this way, the air in a tire is at the pressure of 33' of water, air outside of the tire is at sea level pressure, all is fine until you connect an open hose to the tire, then of course the pressure equalizes and the tire goes flat.

[Offshore454]

People will do what they want to do, but as other actual divers and certified diving professionals besides myself have stated, it's impossible to breath through a hose or snorkel that reaches more than a couple feet below the surface without a compressor or compressed air in a tank. If you want to trust your life on the purity of the air out of a compressor from Harbor Freight, do it. The physics of how air that we breath affects your body at the surface changes radically when it's compressed. That's why there are nitrogen limits on how long we can stay at certain depths, and required deco time and safety stops. That's also why carbon monoxide is even more dangerous in compressed air. Even oxygen can kill you in too great a concentration. It's called oxygen toxicity. You won't get this at 5 feet, but it's an example of why to get certified and not just play with your life. Just sayin.

[a64pilot]

O2 will/ can kill you below about 30'. There were pure O2 rebreathers in WWII and quite a few deaths.
I do Deco in caves with pure O2 at 20'

Oil less compressor cannot make CO, as there is no combustion, a filter is not a bad idea of course to catch any particles there may be.
Don't obviously place your compressor down wind or beside an internal combustion motor.
CO2 is deadly too, ask any rebreather diver

[LLizzard]

So, if you are certified and don't want to mess with big tanks, you could try one of the Spare Air products. I saw the Easy Dive at a show and it was small and lightweight compared to a full blown outfit. Offers "15-20 mins" air supply
Spare Air Easy Dive Explorer Kit

Or the Nomad snorkel/ Spare Air combo. "30 breaths"
https://easydive.us/nomad/

Or just a plain old Spare Air bottle or Pony bottles with your regulator.
Lots of choices on amazon.
https://www.amazon.com/s/?ie=UTF8&ke...l_42er30gfg8_e

[Toys_with_time]

Originally Posted by epiic

Sounds like you are looking for a hookah compressor system

Example:
Built in Boat System W/O Battery

Hookamax Dive Systems

Or you could support a new light weight version that is getting off the ground via Kickstarter

https://www.kickstarter.com/projects...?ref=discovery

TwT

[robbievardon]

A factor which seems to have passed all by is the fact that rigid tube full of atmospheric air or not your chest/lungs are being compressed by the water at what ever depth you are at. Get 6 foot of hose, attach it above water level, stick the end in your mouth and descend to 5 ft then try inhaling.

[Thumbs Up]

I wonder how deep you could go using a cpap machine for an air source?

[robbievardon]

A64 Pilot, your last post could be misunderstood. Should read pure o2 will kill you below 33ft in a very short time. at 330 feet the same applies which is why the breathing mix ratio would change to 20 - 80 the 80 being helium to prevent narcosis. On the extreme depth dives this would again be reduced to 10 - 90. this would be maintained until the SWC returned to surface and the decompression phase started. This would include periods of pure o2. After 2 to 3 weeks under pressure,subject to job, Deco would take 20 hours give or take a bit.Interesting that you are now using o2 for cave deco. Not all my time was deep,had a bit of time at 120 feet planting artificial grass around the spud tanks of a jackup. Pity my last but one post has been scrubbed!!!

[SVNeko]

How would you exhale? Without a regulator and with just a snorkel mouthpiece you would just be pushing stale air back and forth, unless you took it out of your mouth each breath. But that would get old quick. Maybe blow out your nose through your mask?

[Dulce Suenos]

New user as of today. Hello all. I have something I would like to hear comments on. I have a 38ft boat and want to change anodes, scrub the hull, maintain the rope cutter, etc. I am not qualified to dive. I was in the military in submarines. We had to do the 100 foot deep escape tower training every 3 years. There is an accommodation bubble on the side of the tower at the 100 foot deep level. We went in, shut the outer door, flooded the accomodation bubble, equalised ears as it flooded, breathed the air as it was compressing and obviously when the pressure equalised at 100ft we could open the access hatch (which of course was below the water line) to the main tower. Our heads obviously in the air bubble above. We ducked down, through the hatch. As we exited the accommodation bubble a trainer swam across from the other side of the tower towards us from a diving bell that had previously descended from the surface. The trainer would return to this whilst waiting for the next person to exit the accommodation, breathing the compressed air at 50 psi. So, we ascended the tower obviously breathing out constantly all the way to the surface.

So, diving bells, pressures, air pockets, breathing out, etc. all perfectly understood. So, now to the boat and needing to spend time at say 3 to 5 feet (2.5 psi). I gather that each breath is about 5 litres. So take 10 litre inverted bucket with sufficient weight on it either weighted to the seabed if in a shallow bay or suspended from the boat if in deeper water. Set the "breathing chamber" at say 5 feet depth. Run a breathing quality hose from a 12v electric double diaphragm pump such as the xx model (dont know if its permitted to say the make). It can produce up to 300mbar (4.2 psi) bar at 150 litres per minute flow, mount the hose so it pumps into the inverted bucket. Excess air will bubble out to the surface, the pressure in the chamber would be at the 5 feet depth (2 psi). Run another breathing quality hose from inside the chamber to a snorkel mouthpiece and take breaths from that when needed. Exhale into the water, not into the mouthpiece. Better still use a proper inhale/exhale mouthpiece. Breathe out on the way back to the surface (I wanted to write that in capitals). The air is clean due to the electric diaphragm pump (is it really?). The pressure is slightly above the depth of the person. In the military we used 1.25 psi above depth pressure so 4.2 psi less 1.25 = 3 psi ish = 6 feet ish of depth capability and ease of breathing in. Excess pressure is not an issue as it releases itself from the breathing chamber, carbon dioxide and monoxide are not an issue. It will be possible to draw breaths. The compartment flood technique we trained for in the tower was tested in real life to 600 feet from a submerged submarine so the idea is obvously good. So it comes down to maintaining sufficient air in the "breathing chamber" and at the correct pressure, by using an electric air pump and then breathing from the chamber. Any comments ?

[fstbttms]

So your plan is to swim back to the bucket (from wherever it is you are around the boat) to take a breath? Sounds like an exhausting, time-consuming way to clean a boat bottom.

[Dulce Suenos]

Hi, thanks for replying. No, the idea is the bucket just stays nearby (We have very little tide in the med) topping up and bubbling away and there is a second breathable hose (say 3 metres long) fixed up inside the bucket to breath from. That way theres enough hose to move around a bit to unbolt a shaft or hull anode, change the rope cutter blade, change the bow thruster prop, brush off the main prop, etc. Im trying to create a workable, safe (although maybe a bit cumbersome) system to give me 10 minutes underwater in a nice calm Formentera bay using basic and sound principles without spending a lot of money on a hookah which will likely sit in a locker deteriorating. Theres a lot of experience and knowledge in this forum so I wanted to bounce the idea to see what comes back.

[chris mac]

I doubt you could dry air using the second hose. There won't be enough pressure behind it to get it 3m to you.
Also you say you don't want to spend the money on a hookah. Your plan has a compressor, food grade hose, possibly a mouth piece. Buddy, that's basically a hookah. Your just complicating things adding a bucket and free flowing the hose.

[Dulce Suenos]

Thanks. The idea is that the bucket depth is varied so it is slightly deeper than the depth of the persons chest, therefore the breather hose will have slightly more pressure in it than the depth of the person. The person operates horizontally at this depth (working on a particular boat component) therefore wont the pressure in the hose be sufficient to breath from?. I can imagine that if the person goes deeper then there will be more difficulty in breathing and if they come shallower they will feel more pressure in the mouthpiece. I recognise that the person has to recognise that if they are floating up towards the surface, even from 3 feet there is a danger in over pressuring the lungs. The mindset is to stay at the correct depth working on whatever and then throw the mouthpiece and breath out to the surface. I often free dive to 10 metres so i am very aware of breathing out. The idea is to get down to no more than 4 or max 5 feet. Mostly around 3 feet. The pump pressure is just over 4 psi, 150 litres per minute.