Saturday, December 22, 2012

Dehumidifier vs Desicant

Four years ago, in the fall I noticed something I had not seen before; the dreaded black spots, this time on cabin carpeting. Clearly, better humidity control was in order for the cooler season.

A large compressor unit would be a beast on a small boat. Though I have a 30-pint unit at home, the downsides are major:
  • A lot of amps on the shore power cord.
  • A back injury waiting to happen; the unit is huge and awkward.
  • In the way.
  • Loud.
  •  More capacity than I needed.
So I looked around and found the Eva-Dry 2200. The no-compressor  principle is elegant, the only moving part being a small fan. The over simplified explanation is that of a thermocouple, but in reverse. Instead of a temperature difference creating a small electric current, the current is forced in the reverse direction through a whole stack of thermocouples, creating a cold plate. Water condenses on the cold plate and runs into a tank.

The size and weight (just a few pounds) are appropriate; when not in use it's easy to swing it into a cabinet for storage, although for day sailing I just put it in the sink to keep it from falling. They are prone to icing in temperatures below about 45F, but deicing by controlling the run cycle with a light timer is simple; 8 hours on at night and 6 hours off during the day. Even in the depths of the winter, the interior of the boat warms above freezing during the day due to solar heating.

I modified the tank by drilling a hole and tapping in a 1/4 NPT x 3/16" ID hose barb. The hose runs to the sink so that it never fills and to prevent freezing and breaking in the winter.

 So far--four years--the unit has just  purred along, removing 2-8 ounces per day, keeping the relative humidity at 45-65% at temperatures from below freezing to 95F. The boat is always dry, the bedding fresh, and interior corrosion issue non-existent.Just like home.
 Cold plate frosted

Cold Plate Thawed 

The only real alternative is calcium chloride descant. I did an article about these for Practical Sailor  magazine and still had a few left over. I held a race several years ago, the Eva-Dry in the port cabin and a large absorbant bag on starboard. It wasn't even close. It would take ten 5-pound buckets of CaCl2 to do what this unit will do over 3-4 month winter season.

I also tested a cheaper version from Perfect Home. It lasted about 8 months, just like the reviews said it would.

Tool Box

There is a window shelf outside the head that is of no particular use. Sometimes we keep shoes there, but because of the hatch, spray is always a possibility, limiting possible uses; nothing that can't get wet, nothing tall that might block the hatch. I reasoned a light box I can pick up and move will find some purpose and stow some clutter. I like the semi-traditional look; it kind of works on a sailboat that is only semi-traditional. Though sailing is by nature nostalgic, multi-hulls have to keep there distance. No baggy wrinkles here.

A simple scrap lumber project, it is made of 3/4-inch pine to make the ends strong and 1/4-inch ply to keep it light. What will we keep in it? Though I stuffed some harnesses, tape, and cables ties in it for now, we won't really know until we've been cruised with it for a while.

Monday, December 17, 2012

EG vs PG: Conventional Wisdom That is Provably Wrong

rev. 2-4-2013

Some time ago, maybe 30 years ago, winterizing anything with ethylene glycol (EG) became completely unfashionable. Politically incorrect was the new term. Everything had to switch to propylene glycol (PG) because it was lower in toxicity and thus more environmentally friendly. We had always understood that PG must be used in potable water systems because of EG's toxicity and the potential for someone to take a drink before the system was well flushed. Reasonable enough, and we assumed, right or wrong, that people weren't chemistry smart enough to keep these differences straight. But the connection between toxicity to humans and damage to the environment was never correct. It turns out EG and PG are equivalent and it is only metabolic pathways unique to mammals that make EG dangerous to people.

MSDS Information. Producers of products with any hazardous or toxic ingredients must disclose and explain these to commercial users through OSHA's MSDS program that most of us are familiar with. Though there are many products using EG and PG, these 2 sheets present representative data from the same manufacture:

Ecotoxicity in water (LC50): >5000 mg/l 24 hours [Goldfish]. >10000 mg/l 48 hours [guppy]. >10000 mg/l 48 hours [water flea].
Ecotoxicity in water (LC50): 41000 mg/l 96 hours [Fish (Trout)]. 46300 mg/l 48 hours [water flea]. 34250 mg/l 96 hours [Fish (bluegill fish)]. 34250 mg/l 72 hours [Fish (Goldfish)].

Though they have expressed the data in different terms, we can readily see that acute toxicity requires percent levels (about 3-4%) of glycols; as a practical matter, the fish will die from low dissolved oxygen before direct glycol toxicity is important. Why the great difference? EG poisons only at relatively high doses in humans, primarily by the action of specific metabolic byproducts; it should be no great surprise that marine organisms deal byproducts and salts differently. This turns out that this is true of all non-mammal organisms. I don't see this as a surprising contrast; zinc is incorporated into many bottom paints because of its high marine toxicity (0.5ppm is quite lethal) and yet the pharmacy sells zinc pills for humans as a dietary supliment. You don't feed chocolate to a dog.

Biodegradability.  No important differences. Both are attacked by bacteria as readily as sugar. In fact, when glycols are used in the air conditioning systems of large buildings it is required practice to either add a biocide or to control the pH at very high levels, which is also lethal to all organisms. Both products exhibit equivalent biological oxygen demand (BOD) is water and both can cause fish kills by this mechanism if discharged in large amounts to small waterways. This is occasionally seen around airports that deice airplanes in the winter. Again, they have found no difference between EG and PG. There is a preference for PG over EG in this case because they spill large amounts--perhaps 5000 to 20000 gallons during a snow event--and for mammal wild life to drink from puddles is plausible.

From the experts: In fact, I could not find any scholarly (fact-based) work that gave a contrasting opinion.

From Risk World (European conference)
"Based upon the limited available data, no general distinction can be made between aquatic toxicities of ethylene and propylene glycol formulations."

From the World Health Organization (WHO)
"Ethylene glycol has generally low toxicity to aquatic organisms. Toxic thresholds for microorganisms are above 1,000 mg/litre. EC50s for growth in microalgae are 6,500 mg/litre or higher. Acute toxicity tests with aquatic invertebrates where a value could be determined show LC50s above 20,000 mg/litre, and those with fish show LC50s above 17,800 mg/litre. An amphibian test showed an LC50 for tadpoles at 17,000 mg/litre. A no observed-effect concentration (NOEC) for chronic tests on daphnids of 8,590 mg/litre (for reproductive endpoints) has been reported. A NOEC following short-term exposure of fish has been reported at 15,380 mg/litre for growth."

From the US EPA, study of airport deicing with EG and PG. Please, read the whole study (447 pages). Marine toxicity is never mentioned in the executive summary because they could make no case against it. They are the same. Neither is good, true enough, but they are the same. They did conclude--correctly based upon my expereince in marine toxicity testing--that the thickeners used in wing deicers are quite toxic because of their effect on gill tissues, but this is not relevant here. Many "non-toxic" cleaners, even common dish soaps such as Palmolive and Dawn, are quite toxic to marine shrimp because of this effect. I've done those studies. They also report that some of the anti-corrosion additives are toxic, it is important to note that as diluted in the formulation for use in a boat (about 3000:1) they contribute very little.
"Table 9-1 summarizes aquatic toxicity data from studies that directly compare ethylene glycol and propylene glycol under the same or similar experimental conditions. In general, the data show that ethylene glycol and propylene glycol exhibit aquatic toxicological effects at concentrations within the same order of magnitude. Although EPA does not use such a system, the U.S. Fish and Wildlife Service Classification System for Acute Exposures defines “relatively harmless” as any chemical with an LC above 1,000 mg/L (3)."

What about the corrosion inhibitors? In PG formulations common inhibitors are dipotasium phosphate and other relatively harmless salts. In engine coolants organic acids and azoles are common. 2-ethylhexanoic acid has an LD 50 for marine organisms of around 100 ppm, but multiply this by 133 for actual use concentrations (LD 50 = 13,000 ppm).
tolyltriazole (TT) has an LD 50 of about 50 ppm, but multiply this by 6000 for actual use rates (LD 50 = 300,000 ppm). Both are biodegradeable and neither is thought to bioaculmulate. So while the inhibitors do contribute to toxicity, small amounts of diluted engine coolants remain far below levels of concern.

What conclusions can we draw from this?
  • EG and PG are simply no different when released into a large body of water.
  • The conventional wisdom regarding EG vs PG marine pollution potential is just plain wrong. Perhaps the PG manufacturers have pushed this. Perhaps folks writing web site copy for good boating practices didn't actually research their writing; those I interviewed commonly related that their information was simply copied from another popular site.
  • Both can be recycled, and this is a good practice whenever possible. But it isn't always possible and the damage of discharging a few gallons is equivalent to tossing an equivalent mass of wood chips in the water.
And a closing point. In all 50 states, all ethylene glycol based engine coolants include a bitterent (Denatonium benzoate) to reduce the probability of accidental ingestion. I've tasted it and can't believe anyone could manage swallowing it now. Suicide perhaps, but not by accident. The notion that antifreeze is "sweet tasting" is simply out-of-date and accidents are historic, not current.

Why does this matter? Because PG is not so good for certain materials of construction and EG is better. Specifically neoprene and nylon don't react so well, and these are common in sanitary and engine systems. That's why.

Update 2-4-2013: Neoprene becomes about 2 times stiffer after 30 days of exposure to 25% PG and about 3 times stiffer with 5% swelling after 3 months exposure. Identical EG exposure causes no change. However, stiffness and size return to normal within 48 hours when soaked in fresh water. Any lasting harm? Not certain.

Friday, December 14, 2012


It's often said that boats are sold by the pound; epoxy, glass, aluminum, stainless, and the labor to put it all together. Multihulls run higher than monohulls because the keel is cheap in relation, they don't need 2 of so many things, and because the construction is less convoluted. I'll stick to multihulls, since it's what I know.

For the sake of argument, let's say you can buy a Gemini Legacy for $275,000/9,400 pounds, or about $30/pound. A performance boat like the Stiletto 27--if one could be bought new-- would be about $80,000/1,250 pounds, or about $65/pound. Gunboats run about $80/pound. Ouch. Used cars, on the other hand, run perhaps $2-$4/pound; though they don't float so well, they do fly to windward.

What would we pay for a lighter boat with better performance, strength being the same? Would we pay $40/pound? Most of us bought used--I paid about $13/pound--but I'd spend a little for speed, maybe $20/pound. By that logic, we would pay ~ $30/pound for every bit we could save on our current boat, whether from taking out the trash. Hauling less fuel when practical, or pumping the holding tank more often. We would evaluate every project, looking for places to swap composites for steel and Spectra for stainless steel cable.

Anchors. A 35-pound new-age anchor seem to be the thing if you want to stay in one place. Certainly the second anchor should be a Fortress? A $239 Fortress F-16 compares with a Danforth 16 for $89, but at 6 pounds more. $25/pound for the savings. And of course the Fortress is much easier to handle, so very OK; doctor bills for my back add up.

Chain. Proof coil or BBB vs. G4. For a given rating, G4 is cheaper. Perhaps it is less durable in the very long run, but given the value we place on weight savings, an easy call.

Chain. G4 vs rope. Again, rope is lighter and cheaper. But rope doesn't feed through the windlass as well and cuts are possible. I chose 100 feet of chain backed by rope as a compromise. In the shallow waters of the Chesapeake that puts me on all-chain 98 % of the time. All-chain for a multihull is hard to defend, and I would rather have some rope for shock absorption in extreme conditions. A dollar per pound foolish compromise? The windlass made the decision for me.

Lifelines. Stainless is about 3 times heavier and 70% more expensive than Amsteel, even when the Amsteel is sized to be 3 times stronger.  Only $12/pound for the savings and a $120 savings for my boat. Durability seems good, as the first reports trickle in. I've seen corroded stainless snap without warning. I'm going with 3/16-inch Amsteel in a few years. Should be good for a 0.02 knot improvement (yes, I calculated that figure).

Locker stuff. Always a hard call. It's always hard to say which spares and what toys will save the day, but at $20/pound to haul it around we need to be circumspect. Certainly seasonal items such as quilts and wet suits can go home for dry storage. How much is the labor? Heck, they need cleaned or serviced anyway.

Fuel vent filters. A 1-pound vent filter eliminates the need to keep a full tank to reduce breathing, perhaps reducing by 100-150 pounds the amount of fuel that must be carried day sailing and on short trips. Only about $1/pound. A bargain. They also reduce evaporative fuel loss, making them free in the long run.

Down-sizing ropes. So long as the stretch and handling characteristics of the high-modulus lines are suitable, makes sense even for the non-racer. But sometimes the handling and stretch characteristics are wrong--I like some stretch in the traveler and topping lift. I like lines with some size, nothing below 3/8-inch. I put in a free Spectra traveler line and I don't like it better. I have Spectra genoa sheets an they are fantastic. I would decide based upon function, not weight.

Leaks. Are any of the crash tanks holding water? A hundred pounds of water would create a $3000 loss in value, one more reason to get it fixed.

Aluminum or composite propane tanks. A good weight savings (~ $15/pound) and non-corroding. I'll go that way if mine get shabby, but I keep them painted for now.

Holding tank. Pumping more often couldn't hurt, but I'm lazy. A Raritan Lectrasan might make sense for some folks--it weighs about the same as 10 gallons of water when full--but that is about what I average in my tank and I prefer the practice of shore-side pumping-outs. Additionally, my home marina and local sailing area is a no-discharge-zone. No weight savings for smaller boats or smaller families, but worth considering for larger boats.

Freshwater tank. There's really no reason for it to be full all of the time. But I never know when I'm going to head out for a day or two.

Batteries. There may be some real opportunity in the near future, when laptop tech (lithium) approaches lead/acid for economy. We'll need to look at pounds/amp-hour and cycles.

Projects. Yep, I've added a few pounds here and there. But I use aluminum and light ply/composite constructions where ever practical, instead of stainless or solid wood or glass. The solar panel mount was aluminum and minimal. With the exception of the sea chest (composites would have been all wrong there) most of my shelf and box projects are 1/4-inch ply, glass and epoxy. I use fabric in place of wood where possible. Lashings and stropes save ounces.


So what's on my lighten-up list? A Mast-Mate mast ladder; haven't used it in years, will do a quick inspection climb and take it home. I keep accenders on-board anyway, so in an emergency they will serve. My bike rack can stay at home with the bike. I've got some spare blocks that could be at home. I've got a little gut to lose before ice climbing season. What stays? Any part I've used before: sheer pins, spare props, oar locks, cabinet catches, engine parts, electrical stuff, and some bits of rope (2 extra rodes and some small stuff). Food and beer.

Weight saving projects? There is certainly a noticeable difference, loaded for cruising vs. empty tanks and no crew. I remember the sea trial on the day I sold my Stiletto; emptied of superfluous stuff and with a clean bottom she flew, reaching at well over wind speed, into the high teens under working sail alone. I wanted to keep her.