Freezer/Fridge box construction

[Roy M]

I did a quick search and didn't find any threads devoted to the actual construction of the enclosure for a freezer/reefer box, and I'm looking for confirmation/new ideas/condemnation for my proposed unit. Demolition is about complete and I'm preparing to build the box itself.

The unit will fit below the sterncastle dining table of my Searunner 40 trimaran. This area is in the aftmost section of the main hull, adjacent to the galley area. The floor in the sterncastle is raised a foot above the main cabin sole, and the bilge area beneath is about two feet deep, on average. It lies largely at or below water level. Access is direct for the cook, and allows the remaining bilge area astern to use for access of the compressor, etc., with minimal tubing runs to the holding plate. The freezer is furthest aft, with an intervening foam wall, pancake fan and return port to the freezer for cold air transport to the reefer box. Freezer volume is about twice that of the reefer, about 9 cubic feet total. Access is via two single R-Parts insulated top opening doors, covered with foam backed indoor/outdoor carpet with bound edges and secured to the substrates.

I am actively considering fiberglassed interior facing of 1" polyurethane foam, interior corners with epoxy filler fillets, formed ledgers to support shelves and removable carrier boxes. The holding plate will attach to reinforced studs built in to the wall aftmost in the freezer. I have stolen the idea of using the floor matting, with a small sump below, for cleanout. All surfaces will be coated with linear polyurethane paint. LED lighting will be installed below the top cap, with magnetic switching. I'm even considering a switch to change the color from white to red, should I need some refreshment while on watch.

The core insulation will be the "space-gel" vacuum units distributed by R-parts, on all planes of the box, followed by another 1" of foiled polyurethane, and finished with a 1/4" epoxied Baltic birch ply exterior box. All tubing and wiring will enter via a fiberglass or PVC tube at the upper corner of the freezer box, and foam sealed. No holes will penetrate the vacuum panels. Finally, I will do my best to completely seal the interior insulation panels from any access to ambient moisture that wasn't there when I sealed the box (I don't have a vacuum chamber handy).

I am going to try to make the entire box assembly removeable (after disconnection of the wiring and tubing connections), should I suffer some catastophic hull damage below the box. Bilge drainage has been included in the design, with additional, external foam blocks surrounding the box to reduce airflow (without eliminating it!).

Okay, so have at it folks. I would rather make any changes now than later.

[Strygaldwir]

KollmannMarine Boat Refrigeration Specialist

Is by far the best resource for building a box. Richard is a regular contributer to this forum and his website has an outstanding discussion of the various construction and insulation considerations. I followed his recommendations on box configuration and I couldn't be happier.

[James S]

So far it sounds OK to me.
The freezer sounds a bit large (9cubic ft?)
I think your doing the right thing using off the shelf doors...that will save a lot of work.

[bhenry]

Kollmann is the Guru! He gives a lot of his time to all of us out here looking for answers. Thanks Richard.
I went through this last year and am just now installing the Seafrost air cooled components. Boat building is slow! I used Glacier Bay vip's and added between 3" and 6" of blueboard in case of panel failure. May be overkill and steal valuable space, but the foam is cheap and I don't want to do this again.

Good luck,

Bill

[Badsanta]

I have been looking at the Rparts lids. How do you like them? What is the quality like? They are half the cost of glacier bay lids but you are comparing ABS to fiberglass. Any one use these pre made lids?? Its hard to compare from a photo. Many thanks Al

[Maren]

Originally Posted by Roy M

The unit will fit below the sterncastle dining table of my Searunner 40 trimaran.
...
I am actively considering fiberglassed interior facing of 1" polyurethane foam, interior corners with epoxy filler fillets, formed ledgers to support shelves and removable carrier boxes. The holding plate will attach to reinforced studs built in to the wall aftmost in the freezer. I have stolen the idea of using the floor matting, with a small sump below, for cleanout. All surfaces will be coated with linear polyurethane paint. LED lighting will be installed below the top cap, with magnetic switching. I'm even considering a switch to change the color from white to red, should I need some refreshment while on watch.
...
Okay, so have at it folks. I would rather make any changes now than later.

Just a few questions first:

1. Are you still planning on using the Bitzer compressor?
2. Have you ditched the holes and cork idea?
3. Could you clarify the "LED lighting will be installed below the top cap" part? I am specifically wondering about the wires and placement of the LEDs for protection vs lighting.
4. Could you clarify the "idea of using the floor matting, with a small sump below"? Are you are referring to the 1" industrial rubber matting with hole? And, no pump for the sump, right?
5. Where is the propellor shaft in relation to the box?
6. Any, uh, chance you could photograph this (and post the results)

bhenry & strygaldwir -- you may wish to review this thread.

[senormechanico]

We bought some LED strips from LEDs - underbody kits, cathodes, flexible LED strips, dome lights
These guys have lots of possibilities for lighting.
We're very happy with the
Tri-Chip LED Tube - Amazingly bright & economical - LED Home Lighting
for our kitchen under counter lights.
No affiliation, just a happy customer.

Steve B.

[bob kingsland]

RoyM, sounds like a plan to me. I used the rparts vac panels (2 layers, joints staggered) and then 4 layers of blueboard, and slowly poured foam to fill any voids on the outside of the foam at the inside of the outer plywood box. Made a fibreglass box for the reefer/freezer inner liner, set it on vac panels on blue board, then carefully placed the vac panels around the sides, then blue board, then pour between the blue board and the reflective foil on the inner edge of the ply. Seems to work fine. Then the lid with the rparts double sealing doors, which are a good piece of kit. Badsanta, I like the rparts doors just fine. If you're careful handling the panels then I can't see a problem, because once it's all done up there's nothing exposed and nothing to damage. I guess time will tell whether they slowly lose vacuum, but I also have a lot of blue board.

Best, Bob S/V Restless

[Roy M]

Maren,
1. Yes, on the Bitzer compressor. It will offer some data for this thread in the future. If it doesn't perform as desired, it can be replaced by another technology, maybe, by then, carbon dioxide or small scale fusion reactor. I've got it, it fits well in my setup, so I'll give it a fair whack.
2. Holes and cork have been displaced by moving air actively into the reefer compartment via the pancake motor, returning via a 3/4" hole to the freezer compartment.
3. The LED array will be adhesively bonded to the overhead panel, around the perimeter of the two compartments. Bob Van Ness, my personal guru in these matters, has been using his for several years. When I saw it, I wanted it, it was that cool (no pun intended).
4. Floor mats: Kendall Products Dri-Dek Panels (or equivalent), available at WEST Marine. Correct! The sump is going to be about half the size of a kitchen sponge, set below the Dri-Dek panels, to catch any condensation, spills, etc. for easier cleanup. No holes, whatsoever.
5. The prop shaft log is located forward of the sterncastle, aft of the mainstrength bulkhead. Beneath the reefer/freezer box are the reinforcing plate and fastener bolts for the shaft strut. The folding prop sits just forward of the rudder skeg, which is equal in chord length at the hull to the rudder width, aft of the transom. There will be a couple inches between the bottom of the reefer box and the bolts so that I can visually inspect them (with mirror and flashlight). Murphy's Law, being in full effect, the entire box will be capable of being disconnected and removed for hull repair, when (not if) that becomes necessary.

6. Yes! I'll take some photos after I finish the demolition, during the construction process, and after installation of the unit. I want to get ahold of some of the testing units, especially the recording chip that can be downloaded into the laptop to show the cycling and temperature fluctuation. If anyone can also recommend an amp-hour recorder that I can place in the freezer electrical supply circuit, that would be cool too. This will be handy to know when I get into tropical waters, then transit to the Pacific Northwest, then back to San Diego.

Badsanta: I have one of the lids ( the largest size) from Rparts. I've built lids for others, and this one is very, very nicely made. The rim is stepped three times, with magnetic tape on the inside of the flat of one of the steps, to work with the magnetic seal of the lid. The lid is completely surrounding the vacuum panel, for full protection. I will be using an epoxy coated 1/4" plywood cover to protect the top of the lid, and additionally covered with foam backed indoor/outdoor carpet to keep dust from entering the reefer/freezer compartments. Again, when I get to that point I'll provide some photos. At the moment, I'm still painting, formica covering and installing new overhead panels. The reefer work is temporarily delayed until income gets steadier.

[Maren]

Roy,

Thanks for the clarification; it sound like a really good plan.

[s/v Jedi]

I've seen a mention of aluminium foil in the thread which is cheap but important (radiation barrier, shiny side out). But I don't think enough is said about moisture. Moisture is what kills foam insulation and the R value of it. All the inner liners are good but the protection of the foam from the outside often is not. Also, the biggest trouble-maker is the hole(s) for refrigerant lines, thermostat sensor etc.

I spent 3 months rebuilding our 3 boxes and this is a job no-one wants to repeat. Make the outer lining as much vapor tight as possible so use epoxy. Put the aluminium foil onto the gelled epoxy to tackle 2 jobs in one go.
For the holes for lines/wires etc. I used an 8" long 1/4" drill bit for pilot hole and followed it up with a hole saw from both sides. The diameter a relaxed fit for a thin-wall 1.25" PVC pipe (check that the fittings can pass through it... I found they fit through 1.25" thin wall even though the manual says 1.5" and that must be for thick wall, this is Frigoboat connectors). Use the pvc pipe to cut the foam that you couldn't reach with the hole saw. Next I used silicone to seal around the pipe at both ends so that nothing can get to the foam. After all installing and testing has been done, fill the pipe with expanding foam from a spray can. The thinner the pipe the less conduction of heat through the pipe-wall. Now, the only foam that can be hurt from condensation on refrigerant lines etc. is the sprayfoam inside the pipe, not half the box! (which is what killed my old insulation)

For the inner lining I used the description from Nigel Calders book on boat refrigeration (hard to find sometimes) which is plywood-fiberglass composite. His system of fiberglassing a big sheet and cutting the panels from that works very efficient. I painted it with Awlgrip which is safe for food.... after curing ;-) I learned how to make good looking epoxy fillets with this job. A lot of sanding... use a piece of hose of equal outside diameter and put some sandpaper around that. For the corners I used a cone-shaped abrasive scotchpad-like bit for the Dremel.

The dry-deck panels work great but I didn't add a sump. I just left a corner free from the panels and put one of those no-drip sponges there. Works just as good and really easy in use.

ciao!
Nick.

[Roy M]

S/V Jedi,

Thanks for the excellent suggestions. Regarding the finishing of the fillets, next time try the following: Sanding fillets is a real pain in the fingertips. So, next time, have a bowl of water with a splash of detergent added. As the epoxy filler is beginning to firm up, dip your fingers in the soapy water and begin to massage the fillet, just like a potter does with wet clay. As the epoxy hardens up, go back and keep smoothing the surface. The result can be a fillet so smooth that it looks molded. I use this technique a lot when making fiberglass repairs with epoxy, and learned it when I built my own boat thirty years ago, with WEST System. It's quick, it's easy, and even fun! I can't say the same for sanding or grinding epoxy resin once it has gone off.

Thanks again about the suggestion of the no-sump, sponge corner. That is much simpler and even easier to clean. It will definitely be a part of my final installation. I'll document the process for this thread. I was just remarking to myself how this website, Cruiser's Forum, represents one of the truly admirable aspects of the Internet: the ability to share useful information, the opportunity to learn new technologies, and the chance to correspond with nice folks. Thanks to all of you, contributors, administrators, and even those folks who pay for the advertising that makes keeping this institution on-line. Now, back to work.

[s/v Jedi]

Roy: I think the PVC pipe for the holes through the box are the most important feature and improvement we did. It makes sure we never have to do this again and I am convinced it is impossible to do this with some sealant alone.

have fun with the project!
Nick.