building a coolbox - any good links, tips, articles etc

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niccapotamus

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We (that is the royal "we") but really my other half have decided that rather than buy an expensive square coolbox to keep our stuff cold for up to 10 days I am going to build one into the boat!

Makes sense really - the place it is going to go is in the triangular bit in the forecabin over which sits the infill to make a double berth as it is the only place where we have space.

I don't really have much idea about how to go about doing this other than I recall that it has been mentioned over the years in articles that I have probably ignored in various yachting magazines.

Where do i start please, I have three sides already of a box so I guess i need a marine ply front, then layers of insulation and then an inner box lined so it is waterproof. Add a drain hole and a lid and I'm all finished. simple! I guess I'm going to make a GRP inner lining?

my basic questions must be

where do I get the insulation
how do I make a grp inner lining to the box
what about lid design and seals

thanks

Nick
 
niccapotamus said:
where do I get the insulation
how do I make a grp inner lining to the box
what about lid design and seals
Click to expand...

Make sure you deal with radiation as much as with convection and conduction, by having as many shiny layers as possible between the outside world and the inside of your coolbox. For example, use foam insulation with aluminium foil surfaces, or get creative with a space blanket. Lots more coolth is lost ("heat is gained" for the physicists) through radiation than most people think.
 
I've just been through this and my first bit of advice is expect it to take twice as long as you originally imagine!

I Build a ply box out of 9mm. It was fairly rough around the edges as the base of my space was the hull. Then I tried to seal that with a combination of polyester resin and celotex insulation tape. I bought 2 sheets of celotex insulation, one 50mm and one 25mm and cut boards out to slot inside the ply box. Celotex is easy to cut with a hacksaw. The boards were glued down with a spray glue I bought from East Coast Fibreglass. I think it was called aerofix 2 or something like that. After each layer of insulation I sealed the edges by running a strip of the insulation tape around where the insulation boards joined. (I'm not sure how necessary all the steps I took to create moisture barriers are, just seemed sensible and I'd already bought the tape!) I also cut out bits of celotex to form ridges suitable for shelves to rest on.

The next step was a layer of polyester resin and chopped strand matt. I used fairly lightweight matt and didn't do a particularly good job as trying to fibreglass the overhead surface via the hatch hole was a nightmare. Sanded that back very roughly with course grit and painted flowcoat over it. Then it was just a process of building up a couple of layers of flowcoat and sanding back to a smooth surface. Overall I think the glass and flowcoat layer is about 2mm thick, probably 3mm on the base of the box and the whole thing feels very sturdy.

The lid is just a peice of ply with a sheet of 50mm celotex stuck to it and a slightly smaller sheet of 25mm stuck on to that so that the lid has a lip. The box itself has the corresponding lip for this to rest on. The lid also got glassed and flowcoated (just over the insulation not over the ply).

I also installed an evaporator plate and compressor for mine.
I have 100mm on insulation on most faces, 75mm on one side due to space constraints and 75mm on the top surface. This is the thickness of the actual insulation and the ply and fibreglass will add a bit of insulatingness as well. Anyway I am very impressed with how cold it stays andvery pleased with the finish inside. But the job did take me a lot longer than expected!

Apart from the active cooling bits I think I spent about £150 and got everything I needed from Wicks and ECF.

PM me if you want more details and pictures.

Good luck and sanding resin and flowcoat gets dust everywhere and you'll want a mask!
 
I wouldn't bother with a drain hole unless you want smelly water going into your bilge. There are always bits of something end up in the bottom of a fridge or cool box. Much better IMHO to clean it out regularly or sponge out any water from condensation or drips.
 
I've never done this so treat this advice with caution....

I think it would be easier to glass up the inner liner away from the boat and then slot it into position.

I would make up a ply box with rounded corners, paint and fill it to a very smooth surface, wax and lay up the inner liner on the outside of it. When cured, the ply box could be broken up and extracted.

You then should have a very smooth inner surface with the minimum of effort
 
Spyro said:
I wouldn't bother with a drain hole unless you want smelly water going into your bilge. There are always bits of something end up in the bottom of a fridge or cool box. Much better IMHO to clean it out regularly or sponge out any water from condensation or drips.
Click to expand...

Mine melts 1kg - 2kg of ice per day. That's a lot to sponge out, and I'd need to empty it every time, so into the bilge it goes. It's not at all smelly.
 
niccapotamus said:
Where do i start please, I have three sides already of a box so I guess i need a marine ply front, then layers of insulation and then an inner box lined so it is waterproof. Add a drain hole and a lid and I'm all finished. simple! I guess I'm going to make a GRP inner lining?

my basic questions must be

where do I get the insulation
how do I make a grp inner lining to the box
what about lid design and seals

thanks

Nick
Click to expand...

No drain holes in mine, but I guess I don't need them as I won't be using loose ice to keep it cool.
For making the grp liner, I used the spray glue to stick the chopped strand matt onto the insulation and then 'painted' the resin onto it. You get a lot more resin per weight of cloth than recommended but that's not really a problem as I expect you aren't trying to lose that last 200g.

Oh and for the lid seal, I've bought some magnetised rubber strip from ebay. I haven't done anything with it yet but my plan it to use this to ensure the lid fits pretty airtightly. Gravity keeps the lid down but the lid isn't particularly heavy and so I hope the magentic pull plus the weight of the lid will be enough to squeeze the rubber so that it molds to any inconsistencies in the surfaces and everything seals.
 
Would it not be better to syphon it. I suppose it depend what you put in your cool box but I buy langoustines off fishing boats and the last time some of the juice from that lot stunk up my coolbox something chronic. I would not want it in the bilge. It took a lot of effort to get the smell out of the coolbox and I don't think I would have suceeded with the bilge. I would have had to scuttle the boat!
JumbleDuck said:
Mine melts 1kg - 2kg of ice per day. That's a lot to sponge out, and I'd need to empty it every time, so into the bilge it goes. It's not at all smelly.
Click to expand...
 
pmagowan said:
Would it not be better to syphon it. I suppose it depend what you put in your cool box but I buy langoustines off fishing boats and the last time some of the juice from that lot stunk up my coolbox something chronic. I would not want it in the bilge. It took a lot of effort to get the smell out of the coolbox and I don't think I would have suceeded with the bilge. I would have had to scuttle the boat!
Click to expand...

Mine's the sort which is cooled by loading ice cubes into it, so anything potentially smelly gets wrapped before it goes in.
 
PaulMcC said:
I've just been through this and my first bit of advice is expect it to take twice as long as you originally imagine!

I Build a ply box out of 9mm. It was fairly rough around the edges as the base of my space was the hull. Then I tried to seal that with a combination of polyester resin and celotex insulation tape. I bought 2 sheets of celotex insulation, one 50mm and one 25mm and cut boards out to slot inside the ply box. Celotex is easy to cut with a hacksaw. The boards were glued down with a spray glue I bought from East Coast Fibreglass. I think it was called aerofix 2 or something like that. After each layer of insulation I sealed the edges by running a strip of the insulation tape around where the insulation boards joined. (I'm not sure how necessary all the steps I took to create moisture barriers are, just seemed sensible and I'd already bought the tape!) I also cut out bits of celotex to form ridges suitable for shelves to rest on.

The next step was a layer of polyester resin and chopped strand matt. I used fairly lightweight matt and didn't do a particularly good job as trying to fibreglass the overhead surface via the hatch hole was a nightmare. Sanded that back very roughly with course grit and painted flowcoat over it. Then it was just a process of building up a couple of layers of flowcoat and sanding back to a smooth surface. Overall I think the glass and flowcoat layer is about 2mm thick, probably 3mm on the base of the box and the whole thing feels very sturdy.

The lid is just a peice of ply with a sheet of 50mm celotex stuck to it and a slightly smaller sheet of 25mm stuck on to that so that the lid has a lip. The box itself has the corresponding lip for this to rest on. The lid also got glassed and flowcoated (just over the insulation not over the ply).

I also installed an evaporator plate and compressor for mine.
I have 100mm on insulation on most faces, 75mm on one side due to space constraints and 75mm on the top surface. This is the thickness of the actual insulation and the ply and fibreglass will add a bit of insulatingness as well. Anyway I am very impressed with how cold it stays andvery pleased with the finish inside. But the job did take me a lot longer than expected!

Apart from the active cooling bits I think I spent about £150 and got everything I needed from Wicks and ECF.

PM me if you want more details and pictures.

Good luck and sanding resin and flowcoat gets dust everywhere and you'll want a mask!
Click to expand...

that's really helpful thanks - yes a link to some pictures would be really helpful. so to be clear you put csm straight onto the insulating board to make up the inner "box" covered with flowcoat, rather than made up a plywood box liner which you then covered - and this seemed to work out ok? I will PM you. At least it sounds like a project that won't break the bank ! (which is unusual!!)
 
JumbleDuck said:
Mine melts 1kg - 2kg of ice per day. That's a lot to sponge out, and I'd need to empty it every time, so into the bilge it goes. It's not at all smelly.
Click to expand...

I wasn't thinking about melting ice. Any ice I have is in Packs or bottles. Why not keep your's in a waterproof bag then dump the melted ice over the side ?
 
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