Scuba Diving from a Sailboat

[Groundhog246]

Haven't done a liveaboard yet and not enough charters to form an opinion, mostly shore dives. I do like the fact that on a boat it's roll or stride off the boat, no wading across a "beach", clambering over rocks, etc.
I have done a couple of dives off our own 26 foot sailboat. Getting back aboard is a bit of a challenge. I'm looking at replacing our ladder this year and putting a gate in the stern rail. With relatively high freeboard (over 2 feet), you can't remove weights and toss em aboard. This summer I'm going to try hanging a milk crate or similar that weights can go in and be hoisted aboard later. Get's really crowded with 2 sets of gear and 4 AL80's and absolutely no place to put a compressor.
Long term, when the kids move out, we hope to move aboard something in the 35 foot range, equipped for live-aboard long distance cruising and hopefully with a compressor. Saw a combo unit advertised this winter. Has a small diesel that runs a generator, water maker and scuba air compressor. Can run any or all at the same time. So while you're hanging on the hook, bringing cylinders back up to pressure, you can top of the battery charge or top off the fresh water tanks. Not an inexpensive unit (and no I don't know who's compressor it uses), but cheaper than all 3 separately and more space efficient.

 

[Genesis]

Check out the 3.5cfm Alkin electric.

220v drive, 2.2kw, should be easily startable by most 8kw gensets.

I just got one (for my house) and it looks REAL nice. The only potential issue is that it has a 5 degree angle of heel listed as maximum - so you would only be able to run it at anchor in calm water - but that's ok - you don't want to be running it in rough seas anyway!

The price is right too - $2500.

 

[Lead_carrier]

scuberd once bubbled...
Sailing is the world's 2nd greatest actvity (after scuba of course) and the chance to do both is my life long dream. Someday I will be sailing around the world on my boat and diving anywhere/anywhen I want.

Scuberd, I believe your tagline says it all.. but if you rate scuba #1 and sailing #2. One of us is doing something wrong..:wacko:

 

[Groundhog246]

Genesis once bubbled...
Check out the 3.5cfm Alkin electric.

220v drive, 2.2kw, should be easily startable by most 8kw gensets.

I can state, without doubt, there will not be an 8kw genset on board. We're talking a sail boat in the 35 foot range, not 35 foot or larger trawler, so space is a big concern. With a main engine (propulsion), genset plus compressor would not fit. The unit mentioned earlier delivers about 60A at 12V (1.2kw), plus the water & air, more than enough to charge batteries.
Running an engine to create electricity, to run an electric motor to run a compressor, is not an energy efficient idea. both the generator and the electric motor waste 30% or more, so wasting over 60% of the engines power compared to running the compressor of the engine.
I expect to have a wind generator and solar panels on board as well as charging capability from the main engine (although the "new" electric wheel" low speed motors are starting to look like a viable alternative for propulsion). I expect a battery bank on the order of 400AH or more.

 

[Gisle]

I was very happy with Viking Liveaboards

I've had a couple of liveaboards with the same company before (then known as Scandinavian Divers), but now with their new boat 'Viking of the Orient' it was amazing

I took this photo while at anchor in Burma:

OK, I see images are not allowed in this forum

 

[Genesis]

you might consider buying a compressor like the one I cited above, and instead of using the motor it comes with, compute out the sheave sizes necessary to get the correct RPM, get a magnetic clutch (as used for auto AC systems), and set that up
on an existing propulsion or generator engine system.

A small Faryman (single cylinder diesel) would easily run this, the watermaker and a nice-sized alternator. I don't know what the "package unit" costs, but I bet you can put the engine plus pieces together cheaper than you can buy the unit pre-fabbed, and the best part is that you'll know exactly how it works and thus how to fix it.

The Faryman can be hand-cranked (!) as well; it has a compression release. This is a good thing if you find yourself with dead batteries some morning!

The biggest issue with a scuba compressor is HEAT rejection. These things generate a LOT of heat, and you NEED to get rid of it if you expect it to last.

 

[Groundhog246]

Genesis once bubbled...
you might consider buying a compressor like the one I cited above, and instead of using the motor it comes with, compute out the sheave sizes necessary to get the correct RPM, get a magnetic clutch (as used for auto AC systems), and set that up
on an existing propulsion or generator engine system.

Certainly worth considering. Will certainly review such options closer to the date (about 10 years) we hope to depart.

The Faryman (diesel) can be hand-cranked (!) as well; it has a compression release. This is a good thing if you find yourself with dead batteries some morning!

In theory, the 8HP Buhk on our current sailboat can be started with a pull rope (compression release). I prefer to leave as an untried theory. A starter motor failure is the more likely scenario. We maintain separate house and starting battery banks, so even if all the lights, etc left on till the house bank is dead, the starter will still crank. When we move up, I plan 2 house banks, plus the starting battery (and possbily a small separate battery for it, if we have a genset)

The biggest issue with a scuba compressor is HEAT rejection. These things generate a LOT of heat, and you NEED to get rid of it if you expect it to last.

Yeah, I've been there when the compressor is running. I'm not positive, but I think the combo unit mentioned has liquid cooling. If you're at familiar with marine gensets, that's the secret behind the compact size of the Fischer-Panda genset. Both the engine and the alternator and liquid cooled, allowing for a very compact size unit, encased in a noise reducing enclosure.

 

[Genesis]

Yes, but you pay a FORTUNE for the Panda unit. Like twice an equivalent capacity genset from anyone else!

I looked at their units when my old Onan croaked, but there was no way I was going to spend what they wanted. I'm also not convinced that they can run seawater through the generator body without problems over the long haul (10+ years.) Their warranty is a joke compared to expected service life; Kohler's is 5 years/2000 hours, which is FAR superior to Panda's.

I don't know about seawater cooling of a compressor head for the same reasons. You're talking about some very, very specialized stuff there if someone is doing it, which means its gonna be MAJOR expensive.

Got a manufacturer for the combo unit? I'd like to see if I can find out more about it and give it a once-over.

 

[Groundhog246]

Genesis once bubbled...
Yes, but you pay a FORTUNE for the Panda unit. Like twice an equivalent capacity genset from anyone else!..... I'm also not convinced that they can run seawater through the generator body without problems over the long haul (10+ years.) ...I don't know about seawater cooling of a compressor head for the same reasons. ...its gonna be MAJOR expensive.
Got a manufacturer for the combo unit? I'd like to see if I can find out more about it and give it a once-over.

I don't like raw water cooling in a marine environment, period. I'll probably opt for heat exchangers or keel coolers (like keel coolers best). I think the maxed out 3 in 1 unit was about $13K. With sailboats in the 30 to 40 foot range, running about $8 to $10K per foot, with very limited space, the $13K is likely cheaper than buying an extra 2 or 3 feet of boat to accommodate other options. And then there's the added ongoing expenses (marina, lift fees, etc) which are often priced per foot. For a couple living aboard we've settled on 34 to 35 feet as being OUR ideal. Still small enough for one person to raise and lower sail, reef, etc without help. Big enough to accommodate our needs. We've actually taken quite a liking to the Saga 35 .
I don't have the info on the unit to hand, but if I can find the magazine it was in, will forward the info.

 

[Amanda]

That's something I'd LOVE to do... but never got to.

I love diving from boats and hate it from the shore. Just not the same feeling, isn't it ? I mean, when you jump into the big blue from a boat, you're really straight into your element, not fighting to enter this shallow water, with your fins on and all the stuff...