I've built one box in our previous boat out of blue board and spray foam to fill voids and am planning to build a smaller box (for ice only) in a trailer boat we have, plus it's just become obvious that the box in our Cheoy Lee
40 Midshipman needs to start over.
A few comments. My wife, who usually reads and sometimes posts here, said I should investigate the things in this thread.
On my other box, which we used cruising for a length of time and at the dock
and shorter trips for years, was built of a box I glassed up to fit the space, then used blue board and foam to make a complete solid insulation layer of at least 6" all around. With a super cold machine and the large evaporator bent to fit in a u shape at one end of the box, it cooled quite well, ran maybe half the time or less regardless of temp. While waiting on the fridge unit to arrive we used ice for a couple weeks and could get by on about 20 lbs for nearly a week. Once it was installed, I laid a piece of 3/4" blue board on top of the coils, maybe sealing off 1/4 to 1/3 of the box, not sealed well, and used it for a freezer. We could keep about 12 trays of ice and maybe 20 lbs of meat under the ice frozen quite well. We had no spillover unit, just leakage from the loosely placed blue board. We were quite pleased with the results. We placed steaks in there when we left on one cruise
, and ate them the day before landing in the US 6 months later. We might have come up with a box with thinner insulation, but I don't think we could have had a better insulated box, no matter what we used. Did I mention it was next to the motor
and the motor
ran days at a time?
Now, something that is relevant to the boxes suggested here, particularly the ones using hybrid type arrangements. Lets go to our house we built. The roof is 12" rafters with fiberglass
bats laid between. The building inspectors tried to get me to use something else, like sprayed in solid insulation. I did it my way. The results were just what they warned me of.
When you have heat on one side and cold on the other (ice box or roof, it doesn't matter) somewhere through that thickness the temp will hit the dew point. It'll go from 35 inside to 80 outside, or whatever, but all temps in between will be hit somewhere. Somewhere in that distance will be the dew point. At the dew point, if there is any air, you'll get condensation
. The location where the dew point is will vary depending on temp inside and out. Water
will condense if there is any way whatsoever for air to move around. In the case of my roof, even though I thought I placed the bats nearly solid, there was no way to avoid small air cavities. Through the winter, as temps went up and down, I'd gather condensation
, often frozen, and when it warms up, I get nearly rain sometimes through my ceiling.
If there are any air voids in your insulation, you'll get moisture in there it'll end up wet. Maybe not quickly, but over time it can saturate it, and water
doesn't make a very good insulator.
My first box was built, and the box in the trailer boat will be built pretty much from scratch. I have no problem layering up blue board however I want. I'll build another inner box to fit the area on the trailer boat, layer the foam and build the enclosure.
Our Cheoy Lee
is a different story. It's a big box built as part of the cabinet. I can't get good access to just layer foam around it without tearing everything apart and that is far from my first choice. I can't easily lay up a one piece box and drop it in, so I may have to layer it up and build it in place after the foam is in. I'd much rather make a mold
and lay up polyester on a mold
, but I may have to lay up epoxy
on the blue board. With polyester I can just gel coat it, gel won't stick to epoxy, so that is another problem.
So, the point of the post is to point out the above problem, and say I'll be watching for ideas for the rest of the Cheoy Lee problem.