Propex Heaters

dancrane said:
I know what you mean. Whatever system I use, I'll make sure I can pull a lever to select between drawing in fresh air from outside, or re-circulating what's already in the cabin.

There'll be plenty of times when it's beneficial to suck in some fresh cold night air - possibly every hour or so in a very small cabin - but as long as the cabin air is perfectly breathable, it's always going to be much easier, faster, more efficient and cheaper to raise the temperature of air that's already been through the heater in the last hour.
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Indeed, if heat and cost of it is your only consideration, but outside fresh air usage reduces condensation and increases freshness as anybody who has the facility will attest, my favorite install is a Y valve where recirculated air is used to get a rapid temperature rise and then either blended with outside air or wholy outside air for freshness and condensation reduction. Y valve and a bit of extra trunking is rarely more than £50 or so. Of course if the heater is under rated for the job it will not be capable of sufficiently raising the outside air temperature so it is then pointless trying.
 
Y-valve - that's the bit of kit I was subconsciously thinking I'd need. :)

I was reading today about the huge improvement of comfort for liveaboards using a dehumidifier. These could shift over a gallon of moisture from the cabin air in the course of an ordinary day - though the machine draws 300-600 watts as it does so. I wonder if the desiccating process could in some clever way be achieved just by heat, from burning LPG (outside the cabin, obviously) rather than by high electricity consumption? But I suppose it'll still always need a fan, even if the heat doesn't come from electricity.
 
Dehumidifiers cool the air to condense the moisture then reheat the air. Desiccant types use a desiccant to facilitate the removal of the moisture; they need more power to run as the desiccant has to be regenerated, normally by heating it but are more effective.

Theoretically, you could make a gas dehumidifier using the same system as a gas fridge, but you'd still need the fan and I hae ma doots about its effectiveness!

Keeping the boat warm and well ventilated should mean you won't need the dehumidifier, but the well ventilated bit means bigger heating bills unless you have some sort of clever heat recuperation system.
 
Dan,

I would definitely go Propex,my parents have one in their camper and it works a treat.

I spent a course on a Gib Sea 42 with an Eber and it was a serious pain, very noisy fan, not a huge amount of warmth, and the current draw was enough to be a bother even on that boat !

Coupled with the regular ' I'm stuffed by my complicated & expensive Eber ' threads here, I'm glad I only have an Origo heater ( which is spiffing for 22' ).
 
Good points, well made. In spite of the popularity of Webasto/Eberspacher heaters, I've never admired them or envied their owners.

I can see that burning stuff in the cabin, thereby producing moisture & monoxide, is a simple way to create heat, but I've always thought a propane-burner outside the cabin, heating perfectly clean air which is ducted back in, must be vastly preferable, and also preferable to diesel heaters deep inside the accommodation, requiring flues and venting.

The name "Zodi" is associated with so-called tent-heaters, allowing the burning of propane to occur safely & separately from the intake of air to be heated. I wonder why they're always out-of-stock? I think it would be ideal for mini-cruisers. http://zodi.com/tent-heaters/hot-vent-tent-heater ...I s'pose the Propex is a bigger version on similar lines.

Isn't it bliss, discussing cold weather solutions when it's warm? :D
 
Steve, your words on dehumidifiers have made me think. David's, too. Unlike my earlier assumption, I now suppose it's easier simply to heat fresh cold air from outside, allowing it to replace the humid fug that had built up inside, rather than recirculating the moisture on the basis that it's relatively warm already.

Please forgive my being so slow on the uptake. But...assuming one has fitted ample insulation to bulkheads and ceilings, is it fair to say that moisture building up in the cabin will stay 'airborne' and be removable by simply opening a forward hatch while heated air from outside is pumped inside, further aft?
 
dancrane said:
Steve, your words on dehumidifiers have made me think. David's, too. Unlike my earlier assumption, I now suppose it's easier simply to heat fresh cold air from outside, allowing it to replace the humid fug that had built up inside, rather than recirculating the moisture on the basis that it's relatively warm already.

Please forgive my being so slow on the uptake. But...assuming one has fitted ample insulation to bulkheads and ceilings, is it fair to say that moisture building up in the cabin will stay 'airborne' and be removable by simply opening a forward hatch while heated air from outside is pumped inside, further aft?
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The major advantage of forced fresh air is that condensation is kept to a minimum as the humid fug generated just by breathing, without cooking and other activities is quickly expelled before it accumulates as it does with recirculated air.
 
The other thing with opening the forehatch to let the fug out is that when you're at anchor or on a mooring, you'll often be lying to the wind, which means the forehatch will tend to let cold air in, rather than the fug out.

Funds permitting, I plan to fit a heater to Jissel later this year and I'm thinking that I'm going to need an outlet as far forward as I can manage, ideally in the point of the V berth and another at the forward end of the saloon, as low as possible. I'd have the recirculation air intake aft and ventilation out through the companionway. Of course, that's easy to write from the safety of my computer, doing it in practice may be a little different...
 
Thanks for that, gents, several significant clarifications to my plans for the dream-boat. I intend there to be hot showers, espresso machines and plenty of merrily-boiling tea-kettles on my ideal yacht, so I'll trust newly-heated, ducted fresh air rather than dehumidifiers and recirculation...

...although...I've often wondered if a Propane burner operating safely outside the accommodation, might heat water which could be pumped through interior floor-panels. I visited the Fishbourne roman palace on a miserably cold day this year and was impressed by the underfloor heating in the museum there. Of course I'm comfortably in the land of theory, but are there any staring reasons why such an efficient form of heating, wouldn't suit yachts?
 
I don't know how big a boat you're thinking of Dan, but it will have to be significantly larger than an Osprey to accomodate a hypocaust and the slaves to run it; or a raised sole & 18" headroom ?
 
:rolleyes: Thanks Andy. As I mentioned earlier, I was in the dreamy realms of the boat I don't yet own.

The heater question comes up every winter, but I guess anyone wanting all-season use from a yacht, needs to think ahead about how insulation, heating and moisture-reduction can be achieved. It only occurred to me today, how many small yachts would have their living space significantly reduced, just by the thickness of bulkhead/ceiling insulation.
 
Dan,

since you mention it, I fit polystyrene tiles between the ply headling and the coachroof; also silver foil, partly for insulation and partly as a completely unscientific idea to boost the radar signature...

The boat stays quite warm in winter - once lived aboard at a marina for a few weeks with thick snow on deck - but it's condensation which is the enemy, particularly from the windows; if I was a proper liveaboard I might seriously consider some sort of secondary glazing.

We had 240v and a fan heater with a thermostat then so were toasty, but for normal operations when it's a bit nippy I just have a free standing Origo spirit heater, only useable at rest; it works well,my only gripe is it doesn't last the advertised 12 hours, more like 10-11, and I don't feel like topping up the spirit once it's got hot.

I find one of the snags with winter sailing is the long cold nights, it's easy getting the boat warm but the idea of cracking the hatch in order to get to the pub / chippy becomes a thing of dread, preparing and kitting up like going into battle !
 
dancrane said:
It only occurred to me today, how many small yachts would have their living space significantly reduced, just by the thickness of bulkhead/ceiling insulation.
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The usual main criticism of the 'unsinkable' Sadlers is that their interior volume is small for their length/size. YM even declared that the 34 was too small for long-term cruising, although we have been doing just that for the past ten years and have met owners of the 26 doing the same. However, it all pays off in winter, when the streams of condensation that we had come to accept as normal simply do not exist. As Seajet says, it's the windows that attract the wet but a simple remedy such as Clingfilm or perspex inserts will reduce that a lot. Aluminised bubble-wrap type insulation, sold by Homebase and others, is quite effective and can be stuck beneath plywood head linings and hull liners without making a lot of difference to internal volume.
 
I find all this very interesting. Granted in the UK, sailing is very seasonal and most boats wouldn't be used in winter even if they were adroitly designed to be comfortable then.

And undoubtedly, interior space, cost, even displacement will change if a small boat is to keep its crew warm & dry inside when temperatures are mostly below 10°c outside.

Maybe the many yachts and motor-sailers produced in the Baltic are better prepared for the cold? P'raps that accounts in part for their high prices.

Personally I've always liked the idea of motor-sailers largely because an interior helm allows some low-season navigation...but I s'pose some less obvious rethinking is needed to a boat's fit-out, to make it genuinely comfortable in winter.
 
Dan,

I think there's a factor long before one gets to boat design; quite simply cost - if one can afford a marina, at least for the winter, it may well be a go-er keeping her in.

I have done this a few times in the past, Emsworth Marina is a lovely place to have a ' cottage ' with all sorts of nice hostelries, cafe's, restaurants, chandleries, close to heaven even in winter on a 22 ( there were 3 of us BTW ), for that matter I've had the odd summer there too.

In my present circumstances I'd find it expensive, and really, really don't fancy a swinging mooring even with full tidal dinghy access ( surprisingly difficult and a factor often overlooked ) and insurance agreeing.

With a safe space ashore and the club run boat hoist, coupled with the inevitable ' to do ' list of boat jobs, winter ashore becomes a no brainer for me.

If I lived aboard a boat, which would almost certainly be bigger thus more hassle and expense to lift out, I'd vote to stay afloat; as it is I've decided my mast is staying up for a year or two as I'm fed up re-rigging so will go round Hayling Island for lift out this October.

As for winter sailing, I don't find it cold when under way, it's the long evenings and nights when one really needs a heater.
 
My Propex is coming up to a year old, and having sailed all winter, every weekend, it's been great. It's powerful enough to make a 27ft boat lovely and warm, and in general, I turn it off when I go to bed, and make a mad frozen dash to turn it on again in the morning, and it's safe to get out of bed in about 5 minutes...

As far as consumption, it's really irrelevant to me. I always have a spare gas bottle in a locker, and the price of gas is so tiny, that the £1000 I saved by going propex will buy A LOT of gas bottles! I think I'm going through a 5kg one every 4-6 months?
 
Glad to hear another vote for Propex. I'd like a boat on which everything could run on bottled gas - LPG-converted outboard, stove/oven, Propex, Honda suitcase generator...

Yours is the voice of reason Andy...I'm sure there's plenty of improved comfort from the availability of shore-power, and even from having neighbours close at hand in a marina; although if I could cover the cost of a marina berth, I reckon I'd be dreaming of spending that money on making the boat feel really winter-proof, out on a swinging or drying mooring.

I suppose yachts designed for work in high latitudes, are built with double glazing? And motorsailers with whopping great windscreens...they must suffer badly from condensation.
 
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