Building a fridge from scratch

[Bowdrie]

Originally Posted by wholybee

What about the top/lid? How is that constructed with a double seal and magnetic seal? (Apart from buying a door)
But I'm not sure the best way to build the top/doors (2 doors, one for the freezer and one for fridge).

In the shop I would build a male mold for the top, wax it up and do the fiberglass lay-up.
Pop the top off the mold, then wax it up and use it for the female mold to lay-up the lids/doors, (suitable spacers used to replicate the gasket thickness).
This produces perfectly fitting parts but is not a "quick and dirty" job.
A lot of woodworking goes into making the mold with the tapered sides the lids will fit into, it probably represents close to half of the whole job for a custom box and a bad wax/mold release job will ruin everything.
There are other ways, but sometimes a lot of work can be saved in just buying a pre-made unit.
https://www.rparts.com/index.php?cPa...g63p8k8p1s3e54

[wholybee]

Originally Posted by Bowdrie

In the shop I would build a male mold for the top, wax it up and do the fiberglass lay-up.
Pop the top off the mold, then wax it up and use it for the female mold to lay-up the lids/doors, (suitable spacers used to replicate the gasket thickness).
This produces perfectly fitting parts but is not a "quick and dirty" job.
A lot of woodworking goes into making the mold with the tapered sides the lids will fit into, it probably represents close to half of the whole job for a custom box and a bad wax/mold release job will ruin everything.
There are other ways, but sometimes a lot of work can be saved in just buying a pre-made unit.
https://www.rparts.com/index.php?cPa...g63p8k8p1s3e54

I should mention, I do not have access to a shop (or even a car right now), and everything will be done in the saloon. I am eyeing those rparts hatches, but I want 2 of them, that is over $1000.

My basic thinking is 3 layers of 1 inch foam, under a plywood top. Cut a square, 14x14 in the plywood. Then, cut a square 12 x 12, in the first foam. Then 10x10 in the next. The final would also be 10x10. Then glass it over for strength. This would be done in the saloon, then the whole assembly screwed down on top. Build a lid in a similar way. I would need to account for seal thickness, which might be easiest to do with thinner plywood for the lid.

However, I am not sure about glassing over the "stairstep" seal without a vacuum system of some kind. I can do some basic fiberglass work, but am not a pro, and I don't think I could succeed here. Are there alternatives to Fiber glassing it? I don't think having the foam under the lid bare would be a problem, excepting that if I accidently break a piece of the stairstep down the road it can't be easily fixed.

[RaymondR]

Build the lid first then use it as the male mould for the counter top. Easy to make double step with 45 degree bevels and use thick cardboard strips for spacer between lid and counter top sections.

Piece of cake.

[wholybee]

Originally Posted by RaymondR

Build the lid first then use it as the male mould for the counter top. Easy to make double step with 45 degree bevels and use thick cardboard strips for spacer between lid and counter top sections.

Piece of cake.

How do you get nice sharp inside corners 1 inch away from outside corners with fiberglass without a vacuum? I just don't see how to do that without a shop setup for fiberglass work. Every time I have done any corner at all with fiberglass it is very difficult and often results in failure. Making a double step of only an inch seems impossible.

Also, again, in the saloon of a 38' sailboat. I can do some construction there, and even some basic fiberglass, but not a lot. I am already going to have large foam panels and plywood in there.

[Bowdrie]

Originally Posted by wholybee

I am eyeing those rparts hatches, but I want 2 of them, that is over $1000.

Jeepers, I didn't look at the prices.
Considering that their hatch/frame units are just a couple of vacuum formed pieces of ABS plastic I'm not so sure they're worth it either.
What size(s) are you needing?
You mentioned a 10x10 opening at the bottom of a 14x14 in the countertop.
A 10x10 is pretty small for easy access and 2" of taper in a 3" thick top is pretty severe.
Are freezer and reefer tops alongside each other, (sharing a seam in the finished Formica, or whatever you use for the countertop,) or are they separated?
Are they both the same size?
How big would you "want" them to be, (the size that your eyes see on the finished countertop?

[wholybee]

It's one box that I want to have divided into a Freezer Fridge as a spillover design. It's not huge. Below shows a box rebuild on a sister ship. It'll give you an idea what I am dealing with.

https://www.morgan38.org/morgan38/in...rebuild.15257/

Without measuring (I will, I'm just in the earlier thinking stages right now), I guess the top to be about 16" x 30", Maybe a bit larger. So, a larger opening over the fridge, and a smaller over the freezer half.

The factory opening is quite large, most of the top. With a hinge in the middle of the lid, to open one side or another. Something like that would work well, so I could remove the lid and have great access, or open just one side to not let too much heat in while I grab something.

[Bowdrie]

Ok, I blew up the pics for a good look.
What I saw was a fairly simple single stage seal for the lids.
One that could use a single gasket on a flat plane.
Not a complicated tapered 3-step set-up.
For doing everything "on hand/in the boat" it looks quite sufficient unto the cause.
You should be able to basically copy what he did without a lot of fussing with complicated forms/molds/release agents.
And nothing wrong about using Teak for edge work.
Forget the magnetic stuff, 3M and Taco both have self-adhesive sponge neoprene gasket in rolls that will work quite well.
One thing I would change;
Gasket life and cleaning around the flange/rim of the box is MUCH easier if the gaskets are on the lids rather than the rim of the box.

[RaymondR]

Originally Posted by wholybee

How do you get nice sharp inside corners 1 inch away from outside corners with fiberglass without a vacuum? I just don't see how to do that without a shop setup for fiberglass work. Every time I have done any corner at all with fiberglass it is very difficult and often results in failure. Making a double step of only an inch seems impossible.

Also, again, in the saloon of a 38' sailboat. I can do some construction there, and even some basic fiberglass, but not a lot. I am already going to have large foam panels and plywood in there.

Interesting fact from Simms Engineering Formulas on conduction coefficients in (Btu-in/h-ft^3.deg F) white pine wood=0.80, urethane, foamed 0.84.

So you could frame both the inner and outer parts of the hatch in wood and then seal them and paint them with little sacrifice in insulation efficiency.

Years ago I was wondering how they built those massive insulated tanks they store and export by ship LNG in and was surprised ti find that to get the required structural properties to support the metal inner tanks they sometimes used wood because of it's combination of it's relatively high compressive strength and insulation rating.

[mvweebles]

I just finished a built-in fridge and a separate built-in freezer. For fridge, I wanted a front door for loading, and a top-hatch for grabbling drinks and such. I'm a trawler so have ample power, though setup for longterm anchor-out with 800W solar and 700AH (12V) LFP. I went with 4-inch rigid insulation and went a size bigger on the evaporator. PITA was the front door. These are tricky to build with an adequate bevel.

I had heavy duty SS wire rack shelves built custom (HERE). I think they were about $125/ea for 34"x16"

Peter

[s/v Jedi]

For fabrication of parts, consider using a combination of plywood and fiberglass for the outer shells. Later, you use styrofoam to fill it up and epoxy to glue the shell together.

I often use thin, 6mm / 1/4” plywood to construct something, using 3M blue tape to keep parts together, then “weld tacks” using thick gel CA glue or 5-minute epoxy to replace the blue tape, then epoxy glue and fillet the inside corners and immediately put a 2” wide 6 ounce fiberglass tape over the fillet.

After cure, I use an epoxy putty like TotalFair or AwlFair to close and shape the outside corners. When that is cured, you can wrap it all in something like 1708 fiberglass.

Here is an example I just built. This is 6mm plywood and these outside corners are rather sharp because in this case I didn’t need to wrap in fiberglass, so it’s a TotalFair job, finished with paint. If this would be the underside of a refrigeration lid, I would use a larger radius fillet on the inside and use a router with round-over bit to shape the outside corner for the fiberglass.

You can easily do this on a salon table aboard.

[wsmurdoch]

Originally Posted by RaymondR

Interesting fact from Simms Engineering Formulas on conduction coefficients in (Btu-in/h-ft^3.deg F) white pine wood=0.80, urethane, foamed 0.84.

Something may be wrong here. Marks' Standard Handbook for Mechanical Engineers, 9th ed, page 4-84, Table 4.4.3 gives a thermal conductivity (k) of 0.021 for Polystyrene, expanded "Styrofoam" of 0.021 and of Woods, oven dry, Pine, white of 0.060 with units of BTU/h/ft^2/°F/ft.

[RaymondR]

Didn't look in Marks and I have found errors in Simms before. In any event there's not much area in just a surround and timber is the easiest material to do that job with. As can be seen the lid on my project is fairly complex and I had thought to hot wire carve it in Styrofoam and glass it over but have now decided on a timber frame with polyurethane filler.

[RaymondR]

On pondering on it I realized that Simms specified per inch of thickness and Marks a foot so there will be more than an order of magnitude difference.

[boat driver]

Originally Posted by Madehn

1) i put 6 inches of insulation on the bottom- worth it
2) drain - definitely yes- even put a little external pump on the freezer because it is deep
3) brackets welded into internal box that can support adjustable sliding shelves
4) shelves were made from easy to clean 1/2 inch polycorbonate- shelves all have pattern of holes drilled into them to facilitate air circulation
5) both fridge and freezer have two large holding plates in each-- these take up a lot of room along with accompanying piping which is inside box
6) digital thermostat- yes-- also get one with an alarm and remote temp readout
7) used 2 part foam to seal in cracks and areas that i could not get to- nasty stuff to work with but effective--- put at least 6 inches of insulation on side of box facing outside hull particularly in hot climate
8) VERY IMPORTANT- i have an air pipe with a small computer fan that circulates air top to bottom in my large fridge box-- keeps temps uniform and greatly improved performance and utility- it runs continuously as power draw is minimal
9) my unit draws around 6 amps at 12 volts DC and runs at about a 50% duty cycle keeping food at 15 degrees F in freezer and 36 degrees in fridge- i have separate compressors in each
10) agree with hinged hatch as well as making sure you have excellent seal on top -- door/hatch insulation should be at least 4 inches
11) highly recommend cool blue technautics as a source for parts- no affiliation they just did a great job for me
12) system running on easily replaceable 134a ( easy to source and to carry extra gas on board
13) i fabricated a cutting board that fitted over the hatch to provide even more insulation and seal- be sure to put a rim around hatch at the top if counter can get wet to prevent water from draining into box
14) if i had to do over again, i might put a water tank on one side with an external insulated tap so that i could get cold water without opening the box- may do that yet
15) oversize wiring to compressor to prevent voltage drops - compressors must be well ventilated (mine are air cooled, i would not want water cooled due to power draw and more complexity)- locate compressors where you can clean the heat exchange portion easily
16) freezer and fridges may well have different solutions in holding plates if separate boxes
17) a removeable basket at the top may be as easier than top shelves
good luck

I installed a two gallon water tank with a foot pump under the box floor-it was freak opportunity- that allowed all fresh water to be pumped thru that cold area. yes, it does rob cold but it is really nice and I believe helps accelerate the ice cube tray. Most important, I believe it significantly reduces the need to open the top (which is a 3" insulation/cutting board) and introducing heat.

I would add to above description- - using two part closed cell pour in foam to insulate- which allows the ability to strengthen box structure and not waste any space with fabricated foam boards.(be sure to allow expansion and temporary bracing box walls for bulging) This allowed the entire box to be installed, cold plate conduit installed, water system, etc. and then final phase was pouring in foam.
my compressor runs only via engine, takes about 30 minutes to freeze cold plate, and ideally I install frozen food in the bottom.
Since the compressor (just an automobile a/c type unit) is in the engine compartment, it is all part of the program.
By design needs, I do not intend to leave the boat long term, so the engine compressor does fine. There is space to add an electric compressor later, but I do not "hold" food when not in use. I would suggest this is a glorified ice chest. But most important- If packed (by experience) it will hold frozen/refrigerated temp for about 6 days before I worry about all frozen material thawed.
reverse engineer by the cold plate and system- then build box to suite. Be sure to recognize room to remove cold plate, and easily clean.

[Martkimwat]

I bult a 65 litre top loading fridge in my 26 sailboat about three years back. It is very efficient drawing around 21 Amps p/d. I used vacuum insulated panels 1" thick as there was not enough room to put anything thicker without reducing volume even more ( I had a maximum of 1 1/4" each on two opposing sides). The VP panels were around £400 but well worth it as they are equivalent to around 6~8" of closed cell foam (Kingspan etc) Because it's only a small box, I used an Isotherm BD 35 compressor. The box is of GRP and I manufactured a GRP lid with foam seals and a magnetic catch along the front edge although the weight of the lid keeps it closed.(I used a pair of double pivot hinges that allows a bit of movement of the lid when opening and closing). I got my information from Nigel Calders Boatowners Mechanical & Electrical Manual. I don't have a drain as it adds complexity (hard to fit vacuum panels around) and is a source of heat ingress into the box. I managed to compress one corner of one of the PV panels enough to fit the refrigerator tube and temperature probe plus another digital temperature probe to allow me to check the internal temperature. The BD35 draws around 4Amps whilst running but only runs about a quarter of the time or less. I wrapped the box in 3mm underfloor foam to ensure no sharp edges to puncture the PV panels (only covered in thin Mylar film) and then another layer on the outside and finally wrapped the whole lot in a thermal space blanket which may not be doing anything but just made it easier to see any snagging whilst I was fitting it and cost next to nothing ( I think they were about £2.99 each). I'm very happy with it. It will freeze but will use a lot more power if doing so although I have had it cycling around freezing point and it still only used about 35Amps p/d.The hysteresis on the Isotherm set up is around 3.5~4º. The cost of the PV panels was more than usual because the box was a truncated wedge shape to fit the side of the boat hull. A straight forward box of five sides and a lid would be cheaper. The PV panels are from a company that makes travel boxes for temperature sensitive items (think transplant organs etc). There are a couple here in UK and I believe a lot more in the US.