DSC for MOB rescue
Like Tom Taylor and Joseph DiMatteo (see Mailport PS August 2019), Ive stopped using inflatable PFDs and instead wear inherently buoyant foam versions. I found that ones designed for dinghy sailing are often very comfortable and have convenient pockets for knives, whistles, flashlights, and even handheld VHFs (I keep one with GPS and DSC on myself, especially when single-handing).
My main disappointment is that I cannot find foam PFDs that also have harness rings built in. When I want to clip on to jack lines, I need to swap the inherently-buoyant PFD with a harness or an inflatable harness/PFD. I presume that the USCG has not approved any foam PFDs with built-in harness rings, but I wonder if Practical Sailor or any of its readers have any suggestions.
Don Miguel, Catalina 34
San Francisco, CA
PFD TESTING IN CHICAGO
We have had more than a half dozen PFD clinics in Chicago in the last few months. The one I attended included representatives from the three major inflatable PFD manufacturers. We include more abbreviated information in our clubs Crew School. Everybody is paying better attention. The manufacturers representatives at the clinic said they do not recommend activating the CO2 self-inflation system during routine inspection, or for checking operation. (I spoke to one retired and one active Coast Guard service member about using the CO2 pull-handle for testing and they said they do it all the time.) We pulled the handle on an expired Hammar inflator as part of a demonstration in Crew School. I figured Id leave it inflated for 24 hours to check for leaks. In fact, it deflated observably in less than 24 hours. But then I re-tested, inflating orally. Inflated this way, it seemed to hold the pressure indefinitely. So either higher pressure from the CO2 cylinder over-stressed a seal in the PFD causing it to leak, or orally inflating enabled the seal to seat better. If the seals don't seat, thats another reason to do the regular oral inflation test.
Shungite Water Purification
Regarding your report on rain-catching (see PS December 2012, The Raincatchers Guide), our catamaran has a rainwater collection Bimini and the water passes through a filter en route to the tank. However I suspended a mesh bag of Shungite in the tank to make sure. It is a mineral mined in Russia that Roman soldiers added to their water bags. I remove the collection hoses when not in use since loops cannot be avoided and do not connect until after an initial rain has rinsed the Bimini off. Even so, we have an RO water-maker.
Amaleo, Kennex 38
St. Petersburg, FL
We have no experience with the high-carbon content mineral shungite, but we have tested a variety of filters that use activated carbon (see PS June 2012, Water Filters).
Rewiring Made Easy
I am an ABYC certified electrician and have been using 1 x 19 rigging wire for decades. It is far superior to anything I have found commercially. I crimp a small copper ferrule to each end to keep it from unwinding. Then I round the ferrule on a grinder so it slides through more easily. Also, I never used liquid soap or thick lube. These items congeal, gum up the works, and can attract and hold dirt and debris. I spray the 1 x 19 with T-9 while it is coiled and do the same thing with the cable I am pulling-especially transducer cables. I not only fish the cable but protect and clean the chase at the same time. I have been at this for 37 years and have never had to cut a transducer cable and can count on one hand the number of RJ45 connectors I have had to cut. Beware: The color sequence of an RJ45 connector is usually reverse of what it is on the other end. These can be a real challenge.
ABYC/NMEA certified Electrician
Punta Gorda, FL
Air conditioning at Anchor
Regarding your recent article on the Velair air conditioner (see PS August 2019), any way you slice it, running an AC unit on a boat or RV using battery alone is, in a practical sense, an impossible task. The engineering numbers done properly simply do not add up. You would not even get one short night out of the average battery bank.
Gary Wiseman P. Eng,
M. Eng. Marine Engineering,
M. Eng. Naval Architecture
Thanks for your letter. We received this response from the author of the article, technical editor Drew Frye:
Yes, the Velair unit is a 120 V, not 12-volt, and we have since clarified this in the article. We also explained in the June 2019 report that a 12-volt air conditioner actually would not be of much benefit, since the 12-volt components are generally less efficient. Indeed, in theory, it would seem that running an air conditioner on battery power alone would seem improbable for many boats-and there are strict limitations. In practice, however, we and many others have been able to accomplish this in moderate climates with a well-designed charging system, BIG battery banks (lithium helps), and by working within the strict limitations of the system.
A few formulas and rough conversion factors will keep the discussion moving forward. Battery capacity varies with temperature and rate of draw down. Voltage varies with the battery state of charge and rate of draw down, and charge controller and inverter efficiency influence power conversion efficiency, but they are close enough for discussion purposes.
The focus is simplicity. In practice, add 30 percent or more battery and charging capacity to make up for approximations, battery aging, and inefficiencies in charging.
Watts (W)=volts (V) x amps (A). Since the AC voltage is about 10 times the DC voltage, but there a 5-7 percent loss in the inverter. As an approximation assume the 12-volt DC draw will be 11 times the 120V AC draw.
Amp-hours (Ah) at 12 volts is related watt-hours (using the device for an hour) by Ah = Watt-hr/12. An air conditioner rated at 1,000 watts draw will draw about 90 Ah from the batteries when running full time. It will typically run full time for during the day and for 1-2 hours cooling the boat down, but will run far less at night.
Is it practical for the average boat to run AC on batteries? Not really, and we said that. My original article (see PS June 2019) included a discussion of the inefficiencies mentioned above. Obviously, batteries age and that needs to be accounted for as well. However, what many have overlooked is that the AC runs at full load only when cooling a hot boat. Once the boat is cooled down, and specifically at night, the load can be several times less, and this is what we have experienced. The AC cycles, and it is actually off most of the time.
Thus, although it is impractical to air condition a boat during the day without a large generator, it may be practical for a boat with a good power system to use AC only in the sleeping cabin during sleeping hours. This is, in fact, proven. I often ran the AC for several hours in the morning, after leaving the dock, because the family was sleeping in. The cabin was already cool, so the load was light until the sun got high.
The 250 Ah battery bank we gave for our example is actually small for many cruising boats; my cat had that much. Many cruising boats have 2-3 times that battery capacity.
No doubt AC at anchor is impractical for many boats. It would be impractical on my F-24. It was practical, and in fact practiced, on my PDQ catamaran. If I had wanted to do it more regularly and for 8 hours, I could easily have increased my solar and added several more batteries. I probably would have, had I not sold the boat. It had a very well designed power management system.
I am writing with a full endorsement of the Fin Delta Riding Sail. My schooner, a 57-foot Nigel Irens Design, has a fair amount of forward windage due to the big, unstayed, rotating carbon fiber masts relatively forward. She, Farfarer, can motor around a lot.
I purchased a Fin Delta and found it worked great. In August, 2011, we had a bit of a Southeast blow here in Maine. Winds to 50 knots, gusting. She rode fine in the harbor.
You say in the story that the riding sails should be somewhat offset from the centerline. That is not true for the Fin Delta, and, in any case, is rather problematic to me. The Fin Delta two tails are already offset.
Farfarer, Nigel Irens 57
St. Georges, ME
Chafe gear Update
The Goyer Chafe gear featured in the August issue is no longer available. Practical Sailor apologizes to readers for any inconvenience. A long-standing manufacturer of chafe gear, Fjord, does make a polyurethane-coated commercial version of a chafe protection product that weve tested rigorously. Our report on chafe in this months issue (see PS October 2019 Revisiting Chafe Protection Options) has prompted a closer look at using Climb-spec webbing combined with RP-25 coating as a viable DIY option. Also see PS October 2012 for more details on this and other products-as well as DIY solutions-that will help protect against chafe.