Recommend me best heating method

[convey]

It would make a difference but the frame would be the weakest link as it has no thermal break within it.

Interesting, do you have a camera that picks up heat signatures? Have you taken shots of your entire boat to work out where it is escape from?

I was thinking of when you just bolt and seal sheets of acrylic directly onto the GRP without any frames. I was thinking of trying two sheets, one inside and one outside, say, one acrylic, one polycarb.

Now, I am pretty sure I know what would happen ... at the earliest occasion you'd end up with irritating drip, or condensation BETWEEN the panes you could not get rid of ... but it should be able to seal well enough. In high end double glazing, they use inert gases between the panes; argon or xenon. May be it would be possible to charge them?

 

[Rappey]

I have a thermal imaging camera that plugs into my phone.
Heat escapes everywhere on my boat but windows and hatches are the worst.
The ideal air gap between your panes should be around 24-28mm
Do aircraft windows have an inner pane and some drain/vent holes on the inside?

 

[srm]

Rather than trying to double glaze the windows why not accept that they are acting as dehumidifiers and collect/divert the moisture harvested from the air? Provided of course we are talking of the small areas that were typical of older designs of yachts. Or a simple insulation foam panel held against the glass could be a solution.

I remember someone proudly showing off double glazing on a pilot house boat, I think the two panes were mounted in a double section alloy frame. Don't know how effective they were as the air gap could not have been very wide.

Alloy frames are a heat loss problem though, I was very surprised at the amount of condensation we got on the alloy frames in my wife's recent build apartment in Toronto. Thought the Canadians would have a better solution for their winters by now.

 

[convey]

There are companies that make double glazing panels for narrowboats in the UK, eg here. Some of them might just fit into sizes used by sailing boats.

I don't have alloy frames. My boat uses the old auto H-style rubber seals to hold the acrylic in place. I am concerned about how much pressure they can take if hit by a big green one. A typical hack is to replace them with oversized panes bolted to the cabin that must be much stronger. I thought given the relative differences in nature of the two plastics, combining both would make them literally bullet proof.

Heat loss a secondary benefit.

Seems logically, not so expensive, although I've never seen it done.

The downside to dehumidify action, is that the water invariably streams down the inside of the foam headliner. Fine when you are aboard to wipe them. Hate to think what is happen when absent for such a time as just now. In my case, it runs down inside the liner, then under the bunk cushions, even into the lockers, and I think has caused osmosis under the gel coat there.

 

[srm]

is that the water invariably streams down the inside of the foam headliner

Which is why I said "collect/divert". Without some sort of drip trap we get problems.

My boat uses the old auto H-style rubber seals to hold the acrylic in place.

A previous boat had these, I ordered replacement toughened glass in alloy frames as we sailed offshore in northern waters. When I came to remove the originals I tapped the first out with a wooden mallet. It came out so easily that I just punched the rest out with the side of my fist. Not much effort needed.

My Prout catamaran had oversize acrylic windows bolted through the cabin sides. Its a fairly fairly common method. There was an ongoing problem with leaks, probably due to different rates of expansion and elderly sealant loosing its elasticity. They really needed removing and re-bedding but I sold the boat before facing up to that task.

 

[convey]

I was never sure about toughened glass, unless it was toughened and laminated. Toughened glass is that glass that shatters into small pieces if it is struck wrongly, yes? Laminated is what they use for bullet-proof or safety glass, no? It'll break in small shards but remain stuck to the plastic layer.

I think Houdini hatches use toughened glass but have those bars to protect them from most strikes. Sods law you'd get a bolt on a piece of wire, or something, whiplashing around and striking them badly. Or a stone being kicked up by a wave.

I don't know this. I've never heard accounts of it. I'm very keen to learn. One advantage is they don't scratch so easily. I always think worse case scenario, etc boom or mast coming free and then banging on a 'light.

Thank you for re-affirming my fears as far as these h-sections. Would a wave, or the above, not knock them in? I had to pry mine out with a screw driver though.

I looked at the manufacturers of glass windows, mainly for narrow boats, and I could just get the sizes made (there are limits to how small the radius can be), but not match the vertical curve. Hence exploring alternatives. A second pane on the inside would at least mean any condensation would run down the outside of vinyl covering. I hope.

 

[JumbleDuck]

I was never sure about toughened glass, unless it was toughened and laminated. Toughened glass is that glass that shatters into small pieces if it is struck wrongly, yes? Laminated is what they use for bullet-proof or safety glass, no? It'll break in small shards but remain stuck to the plastic layer.

Toughend is hard to break and when it does disintegrates into small cubes. Laminated is easy to break and forms large sharp pieces whcih are held in place by the plastic layer. Laminated and toughened is the best of both, but has to be thick for the full strengthening effect of toughening.

 

[Kelpie]

If you're worried about waves kicking up stones and damaging your hatches, I suggest you relocate to deeper water ?

 

[convey]

Laminated and toughened is the best of both, but has to be thick for the full strengthening effect of toughening.

Yes, I looked into it. It's doable but becomes expensive. The pieces have to cut, then sent for toughening, then laminated. Obviously we're not thinking of bullet proofing, so I don't think it needs to be so thick (may be 8mm for a small boat without flat pilothouse-style windows? there are codes and rules to calculate it), but a fairly thin, light and flexible Lexan (Polycarbonate) already is but scratches. I was thinking an ultimate could be a combination of Acrylic (outside - better optics, better UV, better scratch resistance) and Polycarbonate (inside - unbreakable strength). A question really.

I also know nothing about new vinyl and polyester composites.

I remember once seeing a photo of the unprotected hand of a motorcyclist that was hit by a stray wheel nut while riding on a freeway at 70mph. Now, you you ask yourself, what are the chances of that happening in all of the millions of miles covered, by 100,000s of riders, striking a target just 2" x 4" tall. But it does. Ditto, heard of some guy being hit by an unmarked lobster pot buoy in a storm at night that was basically a length of scaffolding pole. Just imagining a worst case scenario because at present I certainly don't have a best solution.

 

[ghostlymoron]

Convey, "How do the eberspacher types work, do they have an external intake and external exhaust and then just recycle cabin air?"
There are two configurations; one draws circulating air from inside the boat, the other is to heat fresh air from outside. The former is more economical but risks gradually depleting the oxygen level and doesn't dry out the interior. The second is recommended by the major manufacturers resulting in a dry interior but greater fuel consumption.

 

[noelex]

Toughened glass is strong, but it can be broken by small, high speed particles such as a stone hit at freeway speeds in a car. Small, high speed particles are rare on boat, but not impossible. If toughened glass breaks it shatters into blunt particles rather than the sharp shards of untreated glass. It is therefore unlikely to injure anyone, but if broken you can be left with a large hole that can let in water.

Laminated glass is a little weaker (although the difference is small), but the plastic film tends to hold the broken structure together so it is more likely to maintain some degree of watertight integrity even when broken. However, the major drawback is moisture can creep along the plastic inner layer creating unsightly hazy patches near the edge. The only cure is to replace the panel.

Toughened and laminated glass is slightly the strongest option, but has the same problem of moisture creep.

For our new boat I elected to specify hardened glass to minimise any possible future problems, but I have aluminium storm covers that can be easily attached in the unlikely event of a break.

 

[srm]

A window breaking need not be the end of the world. I had a large (plastic) front window on my first (plywood) catamaran smashed in by a wave. Soon made almost watertight with a bunk cushion backed up with a seat locker hatch and braced by boat hooks and sundry lengths of wood lashed in place.
External storm shutters are the ultimate answer, or less onerous carry pre-cut plywood patches for each size of window with soft foam pads to seal and the means to easily fix them in place.

 

[PetiteFleur]

Interesting - strength of polycarbonate v acrylic. I replaced the acrylic windows on my previous boat as they were badly crazed. I took them home and tried to break them, the only way was with a lump hammer with the acrylic in a heavy metal vice. I was impressed, especially as they were not contained in a frame. I replaced wit 6mm acrylic and was happy. Also replaced the acrylic in my present boat but did not try and break the old ones. The video shown appears to use thin acrylic and polycarbonate - about 2/3 mm?

 

[Hot Property]

Thanks for all replies. Currently googling Wallas and Sigmarine.
Is it fair to say that you do not get more for your money by paying the price premium on the Webasto and Eberspächer brands ?

Correct, and this maybe the reason why.....

Press corner

 

[convey]

What I'm look for is some kind of double ended screw or fixing (imagine a rod with a fat washer in the middle of it), that can be used to hold the panes in place, but also be used to hold stormboards in place about them. Easy enough to have made up (e.g. take some hex rod, turn it down, and thread may be). How do people work that out?

Something that you could just slip into on the bottom, and then attach with a thumbscrew on the top might be better. I tend to think for hairy sailing, you would not need full boards if you had big deadlights. Just a full size but leaving a cut out for light would do.

What are the forces we are talking about, it;s in the 10,000s lbs per sqft (a wave at 7 mph produces 200 pounds of pressure per soft, right?).

That recycling configuration of the Eberspacher must be sucking in a small about of fresh air ... or does it have a separate air intake for combustion purposes? Sorry, I am being lazy and should really go read a manual. But, I refer back to an early post I made about there also being air heating and water heating models.

My understanding is that the water heating models were designed to heat a radiator that would then heat air being sucked into the car/van, but which could then be used to heat simple convector radiators.

The video shown appears to use thin acrylic and polycarbonate - about 2/3 mm?

I'd guess about 3 to 3.5mm, measured in inches though, as American. It's a motorcycle screen.

 

[doug748]

I think some may not have seen this, from a sailor who operates at high latitudes summer and winter, with an uninsulated boat:

His other videos are remarkable, esp if you are into skiing or winter sports.

 

[convey]

It's notable how humble and gentle the Nordic's tend to come across as, despite doing some serious stuff, in comparison to many of the Yankee Youtubers. Sadly his boat got damaged in a storm when not it but the entire jetty broke off its moorings. He pretty comprehensively covers this topic in one video.

Haven't found where he or an equivalent covers insulation yet.

 

[ip485]

A slightly different thought (but noting space and power considerations) a hydronic heater might work - it isnt any bigger than an air heater.

There are a host of advantages - it will give you all the hot water you need through the calorifier, without resort to shore power or engine, is a lot less noisy that an air blown, and you can have a good convection radiator and towle warmer maybe.

I appreciate size may be a constraint, but I am really pleased with mine.

 

[wully1]

Haven't found where he or an equivalent covers insulation yet.

He has not fitted any insulation...it’s a stock boat.

For what it’s worth I lined my cabin with camping Carry mat to insulate it better on a previous boat - cured the overnight condensation drips. I removed all the lining panels, glued battens to the hull /deck head thick enough for a tiny air gap, stuck the carry mat to the hull with hot melt glue then refitted the panels. Cheap, simple, effective and invisible.

 

[srm]

Hi Convey,
Just wondering if you are over thinking the window situation. Definitely replace the H mounting system with a seaworthy solution.
Its just that over the years I have come across a number of long distance cruising boats, two of which had spent time around Patagonia.
When it comes to boats I have an eye for detail, but did not notice anything other than standard looking cabin side windows in any of them.