We live in an area where choice of materials is limited, so we had to make a special trip to Mountain Home (about 50 miles west) to pick up the insulation board. Home Depot and Lowes are side by side there, but neither of them had what I would have preferred, Polyisocyanurate board, which has the best R factor. As always, we had to make do with what was available.
To complicate matters, our Haulmark cargo trailer (actually designed as a motorcycle trailer) was built with 1-1/4 inch steel ribs, rather than a more standard 1-1/2 inch. We could have bought insulation board in 1-1/2 inch thickness, but nothing is ever that easy. To get the thickness we needed I had to go with whatever they had in stock, and get a combination of 3/4-inch sheets and 1/2-inch sheets. We looked at the pink stuff first, but Home Depot only had one of the sizes we needed. So we went next door to Lowes and found that the blue sheets were a buck cheaper, and they had both sizes, so that's what we went with.
As I said in the previous post, some people may say I should have picked something different, but in this area, we have to go with what we can get. And insulation value is of minor concern, because we plan to travel with the good weather, south in the winter and north in the summer...or at least change elevations, which is easier to do in more mountainous terrain. Our need for insulation was as much for sound as anything else. If you have ever been inside a trailer during a heavy rain storm, or worse yet, hail...you understand.
Our trailer's straight sides are only 68 inches tall. Because the roof bows curve up after that, we have a good six feet of standing room, even near the sides, and that's plenty tall enough for us.
Our conversion van has all the seats in it, and the middle row won't fold down. We laid the electric couch/bed flat, and that provided six feet of length (up to the back of the middle row of seats) to lay anything flat in the van, so it worked out well. We needed nine sheets of both thicknesses of insulation, so I took my drywall T-square and a utility knife with us, and we cut all eighteen sheets to a six foot length. The nine 2-foot pieces were also laid flat in three layers on top of the larger sheets.
As you can see, I have an abundance of plywood pieces (with more lumber and trim on our rear deck), left over from my remodeling days in the four years before I retired. If you want to see some of my past projects, they are at http://hardyhandyman.blogspot.com, and that is yet another blog that I need to add more projects to.
What you see in the photo above will be used to cover cabinet frames and other things. Because we look at this project as temporary, we don't want to get too fancy, but still make it look nice. I'm not going to try to buy new matching paneling and build a lot of fancy hardwood cabinets. This trailer is going to get primed and painted a light color on the inside (maybe white). By doing so, I can use up all this scrap plywood without worrying about what matches. It will all look the same by the time I am done, and it will also be easy to fix in case of dents and dings. It's just more practical in all regards. Besides, the light interior (rather than wood paneling) will be much brighter and seem larger.
I had to straighten up this stack of paneling leaned against the right side of the trailer, and had just enough room to stack the insulation board against it. Now you see why I am doing one section at a time. There's not much floor space left until this stuff gets installed!
So now comes the blocking. I started in the front, on the ceiling. We will have two Fantastic fans, one at the front and one at the rear, so I framed the front one first, making sure to leave enough room around it for the trim. The ceiling light shown will eventually get replaced with an LED fixture, and it can be moved slightly when that time comes, but still, I wanted to leave enough room. Also, you can see the fiberglass front cap of the trailer, which is curved. I wanted to stay away from the rib on the roof where the metal roof joins to it.
The framing is slightly less than standard 2 x 2 size because of the 1-1/4-inch rib depth. Every piece of blocking has to be cut down to that depth in order to fit in the space. The steel ribs have to be drilled with a pilot hole before the screws can be installed. I'm using coated 2-1/2-inch deck screws which I pull off a strip of plastic, which was used with my Senco deck screw gun. You can buy similar screws in boxes.
Where the wood joints meet, I use wood glue to make sure they don't move, although I cut everything tight enough that they will stay in place even before the screws are installed.
This former motorcycle trailer had no plywood ceiling in it, and what blocking you see on the far right in the photo above was only "one by" boards, installed to give them something to strengthen the ceiling where they rounded the sheet metal roof. But they aren't thick enough to be flush with the inside of the rib, so they are worthless as far as inside attachments.
The front wall of the trailer was actually two pieces of plywood, with a joint down the middle. I could have done that on the ceiling, but a 4-foot width down the center works out just as well. The upper cabinets will cover the edge of the plywood in most places (except above the entry door and the head of the rear bunk). So I carefully measured to the center, and then 2-feet to either side, and snapped a chalk line where the edge of the plywood would be. After cutting the 2 x 4 pieces down to the size I needed (2-1/2" wide by 1-1/4" thick) and doing a little notching to clear existing roof screws and the curvature in the corners of the ribs, I made a mark 3/4-inch in from the edge, and placed that to align with the chalk line on the ribs. It takes a lot of trial and error cutting and fitting to get everything just right, but is worth it in the end, and there isn't really that many to do.
This is an ideal location, because the upper side cabinets will also be screwed into this blocking, and to the side walls, and the edge of the plywood will be covered by those cabinets, giving the ceiling a "one piece" appearance (except for the one end joint somewhere in the middle, since the trailer is 12 feet long). The curvature of the ceiling and front corners of the trailer will be covered with bent sheet metal, such as aluminum flashing material.
Because some of these "2 by" blocking pieces have to be toe-nailed at an angle, I have been using a special 1/8" by 6" long metal bit, that I eventually broke. Home Depot didn't have any, but I found them at Lowes, and bought three...which I proceeded to break the same afternoon that I brought them home!
No one around here has them, so I had to order some online, which I am waiting to arrive so I can go back to work on the blocking. Trying to drill at an angle into metal is quite tricky, even when going through a pilot guide hole in the wood.
And you never want to drill at an angle toward the outer skin of of the trailer, or you take the chance of drilling through it! ALWAYS drill your pilot holes so that no matter how deep your screw goes, it won't go through the trailer skin!
Some holes can be drilled straight through, if you have room to get your drill and bit behind it, but still, use a center punch to keep your bit from wandering.
As of yesterday, all of the walls in the trailer have been insulated and the plywood re-installed. I removed the wall switch totally and those wires will be spliced together to make the light circuit hot all the time. The dome lights already have switches on them, and besides, I need to tap into those wires to provide power to the two Fantastic fans, which also have their own switches on them.
The only things that need to be insulated yet are the edges of the curved roof down both sides of the trailer, and the front cap area. The sides will be easy. I just need to score the back side of the insulation so it can be bent around the curve of the roof edge. The front cap will be the tricky part. It is curved with the roof, as well as around the front of the trailer, so nothing is straight on it. I can't just fill it with foam because there is wiring up there that has to remain accessible.
The plywood ceiling will have to be installed first, and even the front section of that must be cut in a curve and then bowed to the ceiling curvature. Before I install it, I will have to use spray adhesive to attach foam board to it in front of the last roof bow, as that is the only way to get the rigid board in there or to hold it in place. The same will have to be done with a removable filler panel that will attach to the front wall between the top plate of the wall and the ceiling, so as to make the wiring accessible. Also, that panel will have to have some backing behind the top of it to fasten it in place, so the ceiling will have to extend beyond the vertical plane of the wall so that I can glue and screw some 2 x 2 blocking to it in short sections. That's the only way to get around the double curvature. The wall panel will then screw into the blocking. All that is complex enough without trying to fit insulation behind it, too, but it has to be done that way.
In the process of everything that has been done so far, I have seen many things about this trailer that I would not want to see if I were buying a new one. But rather than get into naming all of the issues I have seen, I think it is more prudent to write a new post pointing out the things to watch for when buying a new (or used) trailer for the purpose of converting it to a camper.
As I said, this post will be updated with more pictures and text as I can get the last of the blocking and insulation work done, but even if you forget to return here, I think you get the idea of what I am doing with the blocking.
After that will come some wiring for the fans, and the ceiling will be ready for the new luan plywood sheets to cover it up. On the sidewalls, I re-used the existing 3/8ths plywood. It's going to get primed and painted anyway, so it saves money. But it had to be removed first, to block and insulate, and then put back on. After the ceiling and front wall are done, then I will start on the floor. It will get new luan underlayment plywood, and then we'll install new 1/8th inch thick commercial tile over it. That is solid vinyl tile in which the color goes all the way through it, and it is practically indestructible. After that. we'll start building the interior components.
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So now that you see what I am doing, and why, what are your thoughts? C'mon...speak up!