How to build super ultra light and wicked strong cabinets for your van, rv, boat, camper, tiny home, trailer,
Ultra-light weight foam construction technique
This is a companion article to the video HOW TO ULTRA LIGHT & STRONG CABINETS FOAM . Please take a moment to watch the video as it explains a lot of this in more detail
When building a custom van conversion, there are many challenges that prevent many would-be builders from completing the van of their dreams. Among these challenges are:
Tools/Power Tools required
Wood working skillset
Suitable work area
Obtaining proper insulation and ventilation in the van
Prevention of moisture build-up
Obtaining a suitable vehicle with decent fuel economy
The Foam construction technique that I’m going to describe here will touch on all of these challenges, and more! It will enable you to build lighter, cheaper and with fewer tools than any other method that I’ve seen. For those who appreciate aesthetics as well as function, it will also allow you to easily and quickly build custom cabinetry with beautiful finishes and custom touches that can rival even professional conversions. But before we get into specifics, I would like to outline some of the biggest advantages to this technique and explain how they relate to the challenges that are commonly faced by those attempting their own conversion.
Weight: The foam composite that we will create can be more than 10 times lighter than traditional wood building techniques. Not only does this increase your fuel economy (1%-2% per 100 lbs. saved as reported by the US Department of Energy), but it’s also easier on suspension and drivetrain components. Most van builders would never recommend a half-ton van for a conversion, but this technique is so light weight that it lends very well to 1500 series vans! In the two conversions that I’ve already done, both conversions weighed less than they did before converting them!
Strength: Lets get this out of the way early – one would think that anything built out of foam must be weak, flimsy and prone to damage. With the composite techniques I’m about to show you, this simply isn’t true at all! The extremely high compressive strength of XPS foam is used to our advantage and in the end a very strong, light-weight and durable sandwich composite is the result. On my current builds, these foam cabinets have been sat on, bumped into and used without worry. When people see and feel this first hand, it always results in astonishment when they find out that nearly everything is made out of foam! I’ve always found it silly when I see people building heavy van cabinetry out of 1/2″ plywood, when in the end it’ll be holding a few totes totaling 5 to 10 lbs. This foam composite is a much better match for the type of weight typically seen in a van conversion. On a recent cleanout of one of my upper cabinets, I pulled over 80 lbs of canned goods out of it. As hard as it is to believe, this stuff is incredibly strong.
Tools and Skill: All of this can be accomplished with absolutely no power tools at all, and with a very minimal skill set! Most of my first van build was done on a picnic table at a campground. There were no power tools making noise disturbing other campers, or drawing unneeded attention. There is really no comparison here; cutting a nice straight line in plywood with power tools can be difficult even for very seasoned wood workers, but nearly anyone is capable of cutting a straight line in foam with a razor and a straight edge. Mistakes are easy to fix and chances of serious injury are greatly reduced over using power tools.
Insulation AND Structure: Since we will be building with XPS foam insulation, cabinets that we build will not only be structural, but they will also provide insulation to our build! In fact, I believe that it’s the absolute best way to insulate, and for good reason! Normally, insulation is adhered directly to the vehicle skin. The problem is that moisture and condensation can become trapped between the two, causing problems ranging from mold to corrosion. This technique solves this problem by allowing ample air space and ventilation between the sheet metal exterior of the van and the insulation, eliminating common moisture and mold problems.
The few tools we will need are not only cheap, but readily available at pretty much any “big box” home improvement store. This is literally all you will need for a custom quality build! Most of these tools are so common, you’ll probably have half of what you need already available to you.
Long razor blade (the very long type, not the standard trapezoid type razor blade)
Extra razor blades
Philips screw driver
Hand Mitre Saw
The simplicity of this technique doesn’t just stop at the tools! The materials we will need are also cheap and readily available! Any big box home improvement store will carry everything you need.
XPS (Extruded PolyStyrene) Foam Panels. This is the common Blue or Pink insulation board that most will already be familiar with. I do most of my building with 1/2″ foam, but thicker sheets can be used in areas that need more strength.
Gorilla Glue. While I’m sure there are other suitable glues, I have found this stuff to be perfect for gluing foam together.
Wood strips that match the dimensions of the foam you’re using.
Luan or thin plywood for doors, countertops, etc.
Fiberglass door screen material. Aluminum will work too and is stronger, but much much harder to work with!
Glidden Gripper latex primer
Before we get started, I wanted to point out that there are many options available that are all suitable to this technique. Canvas and wood glue works very well for laying up the foam board, thin 1/8″ plywood and wood glue works very well, Aluminum screen and Glidden Gripper work well and are very very strong. I’m sure there is a huge range of fabrics (Dacron for example) that would also wok very well. I’ve personally tested all of these, and in the end, the combination that I prefer to use and will cover in this article is using Fiberglass window screen and Glidden Gripper. It’s easy to work with and plenty strong for what we need (though it’s not as rigid as some of the other options above) . It’s the perfect balance of price, workability and durability for my needs, and I’m sure it will fit the bill for others as well. But don’t take my word for it! Experiment with different options, make some test panels yourself and share what you’ve learned! I’m sure there is a lot of room to improve on this concept that we can all benefit from. I will be soon testing using bed liner directly on the foam to make the process even easier, and will report back results of that test. One other note is that while latex based paints work very well with foam, other paint formulations (such as rattle-can spray paints for example) can melt the foam. If in question always do a test before trying something new.
While the intent of this article is not to be scientific, I thought it was important to touch on a little of the theory behind layered/sandwiched composites like the foam composite that we will be creating. While XPS foam is pretty flimsy stuff and easily damaged, it has incredibly strong compressive strength. To put this into an easy to understand context, Imagine cutting out a 12″ x 12″ square of XPS foam board. This small 1 square foot piece of foam will support over a TON (2000+ lbs!) of weight while maintaining 90% of it’s original thickness! A composite is created when we layer the outside of the foam core material with another material that has high tensile strength and low elasticity. For foam to bend, the outer side of the foam must increase in length while the inner side of foam must decrease in length. By bonding Fiberglass door screen to the outside of the foam, it prevents this dimensional change on the inner and outer surfaces of the foam, making it very, very rigid. Since the fiberglass screen material resists stretching very well – the combination of the high compressive strength of the foam and the high tensile strength of the screen work in harmony together to create a composite that is light, stiff and strong. Entire airplanes have been built out of foam using these same principles! If you want more information on sandwich composites, there are a ton of resources available: https://en.wikipedia.org/wiki/Sandwich_theory
Ok, with all of the boring stuff out of the way, lets talk about building actual cabinets out of this foam composite. While the tools that we will use are different, you will find that a lot of the principles used for building things out of wood still apply. Measuring the space for the cabinet, accounting for material thickness, cutting and joining square corners – these are all universal to building with any material. In our case, it’s just going to be a bit easier and we will be able to do this without power tools. On the flip side, there are a few caveats. The foam composite will not hold screws as well as wood, so things like mount points and hinge locations must be known ahead of time so that we can reinforce these areas with small pieces of wood to hold the screws. In the end I think it’s a fair trade off for the simplicity and flexibility of working with foam, and even the little amount of wood used is small enough to use hand tools to easily cut.
Before we start building, lets talk about what we need to do to prep the foam. As I’ve mentioned before, I do most of my building from 1/2″ XPS foam, but keep in mind that you can get even more strength by going with 3/4″ or even 1″ foam board (though you’ll lose a bit of space due to the extra thickness). You can mix different thicknesses of foam as needed to produce the needed strength for your particular situation. Another thing to mention that I think we forgot to cover in the video is that XPS foam comes with a thin, clear plastic film on both sides. This coating needs to be peeled off, and I normally do this as soon as I get the foam boards home so that I don’t forget. After peeling the plastic film off of the foam on both sides, it’s not a bad idea to lightly sand the surfaces real quick, just to improve the bond with the Glidden Gripper paint later! A standard medium grid sanding sponge does the job very well and it doesn’t take very long. The image below shows this thin, clear film being peeled away from the foam board.
Now it’s time to look the end goal, and make a mockup out of foam. Are we building a single cabinet? Is this going to be a full custom build out that includes upper cabinets, lower cabinets and other trim pieces? Have we taken a bit of time to practice on a few scraps (highly recommended!)? Have you sketched out your layout ideas so that you have something to go by? Once you identify what it is that you need to build, there is no better way than to just get started, one piece at a time if need be. Here is where the beauty of working with foam comes in. You can do things one piece at a time, or you can do a full custom build-out all in foam before even gluing or painting a single piece! Simply construct the build using foam and drywall screws. You can mock out the entire interior this way with nothing but a razor knife and a screw driver along with a handful of drywall screws. On the 2nd van build that I did this year, I used this exact technique and built the entire interior in foam so that I could make changes on the fly until I was happy with the outcome. Only when I was satisfied did I take the foam out one section/cabinet at a time to be glued, then laid up with the fiberglass screen and Gripper paint. Things are very easy to change and mistakes are easly corrected during this stage, as nothing has been made permanent yet with glue. The pictures below show the entire foam build I did earlier this year, and only took a good long day to do the full mockup. Note that this technique made it very easy test-fit major items like the bed and refrigerator before making any permanent changes.
When it comes to actually constructing the mockup, it would be a great idea to learn how to use a few simple tools. Learning how to use both a builder’s square, and the big T-square (also called a drywall square) will pay dividends for you in the end. Learning how to measure and cut nice straight square corners is so important no matter what construction technique you want to use. I use the T-square to cut nice perfect straight openings for doors, and also use it as a guide for the razor blade while cutting. And even though it’s a rather large tool, I was shocked when I saw how cheap it was when I first bought it – only around $10! If there is one single tool you shouldn’t be without for working with foam, the big T-square is the one. Once you have the correct tools, I’m sure you will find that the actual act of building things will come pretty easy. The image below shows this very important tool.
After your foam and drywall screw mockup is done, we have to figure out where we want our doors and where we need to add wood reinforcements. We will be adding small wood pieces where we know we will need to mount hinges and for mounting points to attach the cabinet to the vehicle, as well as any other areas we feel might need the added strength of wood reinforcement. For me, the normal work flow starts with using the T-square and marker to mark out door locations and locations where hinges will be along the door edge. After this, I cut out the door openings and make cutouts for the wood we will be inlaying into the foam at these key locations. Using a simple hand miter saw, we can go ahead and cut all of these small pieces of wood, marking each one for the position they will be installed when we start gluing. For the wood, just look for strips of wood that match the thickness of foam you’re using as closely as possible. If none can be found that’s a good match for the foam thickness, you could always buy larger dimension wood and enlist the help of a handyman to rip the wood down to the correct size with a table saw. The picture below shows one of these blocks of wood inlaid where I will eventually install a hinge. This will be covered in screen and paint along with the foam, so be sure you know where they are or it might be hard to find later!
Now that we have a foam mock-up, we’re finally going to start making things permanent. First, we can use a marker and mark how a particular piece went together. We will be removing the drywall screws temporarily so that we can use Gorilla Glue to glue the pieces together. The drywall screws will be reinstalled and lightly snugged down to act as a clamp while the glue is curing. Gorilla glue will foam and expand as it cures, so these screws are very important in keeping things in place! I also glue in the wood blocks at this point to get the gluing out of the way – it’s a pretty messy process and gorilla glue is very hard to get off of the skin! Latex gloves will save you a lot of cleanup time!
After the glue has cured, you’ll probably see that some will squeeze out between the joints in the foam. Before we lay up the foam with our fiberglass screen, we need to take a little time to trim this excess glue with a razor blade so that the screen lays nice and flat with as few imperfections as possible. This part is a little tedious and the glue is pretty tough to cut, but take your time and you will be rewarded with a nice smooth finish later on! In fact, you’ll find that it’s worth the effort in the beginning to do a neat glue job right from the start to avoid as much of this trimming step as possible! Another tip is that as long as the glue squeeze out isn’t major, I leave the inside corners alone, as the screen will radius around it as long as it’s not huge globs. The pictures below shows how much glue typically squeezes out as the glue is curing. The picture on the right I wouldn’t bother trimming since it’s very minor and on an inside corner. The picture on the left I would probably use a razor blade and clean the larger globs up a little.
We are now ready to start laying up our foam! I feel that having high strength in the corners is very important, so I always start by taking some fiberglass window screen and cutting a bunch of 2″-3″ strips. These strips will be laid up with Glidden Gripper paint in all of the inside corners of the cabinet. This will give a little extra strength to the corners as well as allow for overlap when we lay up individual panels one section at a time. When using paint and the fiberglass window screen to lay up the foam, I typically brush a nice thick layer of Gripper onto the foam, then immediately lay the screen into the wet paint, then brush on the first layer over top of the screen while it’s still wet. When doing the inside corners, use the bristles of your paint brush to really push the fiberglass screen tightly into the inside corners and work the paint in behind the screen. If you have multiple cabinets to do, I’d recommend doing all of your inside corners together all at once to give a nice quick work flow. I think the video linked above shows this part in good detail, so refer to it if you have any questions.
Once all of the inside corner strips are done, we can start laying up the cabinets. I’ve done this step both immediately after putting the corner strips in and after the paint has dried, and it really didn’t make a difference- so it’s up to you if you want to let the paint dray first or not. Try to pay the closest attention to the outward-facing surfaces while doing this – these are the parts that will be most visible and imperfections now may bother you later. I typically don’t waste too much time on interior surfaces, since they will rarely be seen by anyone but me. The brown paper bag covering technique that I typically use does a very good job of covering up imperfections, but keep in mind that other finishing techniques might not be as forgiving. As always, doing a few mockup tests before actually taking this on will give you invaluable insight and experience when it comes to how your finish will come out on your cabinetry. After the cabinet is laid up and the paint dries, it’s a good idea to go over the cabinet and look for imperfections such as paint drips, exposed edges of fiberglass screen, etc. Simply sand and trim with a razor blade as necessary. After this I typically do one more coat of Glidden Gripper paint. One thing to point out is how to handle cabinet openings. The center image below shows it pretty well – I simply bridge right over the opening with the screen material when covering the outside faces of the cabinet. Once the paint is dry, simply cut the screen out of the opening. You can then decide if you want to leave the exposed foam edges (pretty cool to show off your foam-building prowess), or even paint the raw foam edges for a better finish. The images below show a few cabinets at various stages of completion to give you an idea what a raw finished composite cabinet looks like:
Congratulations! At this point your cabinet is finished and should be as strong as it needs to be to store your possessions! In a future article, I’m going to cover various finishing techniques you can use on your new light-weight composite cabinets. This ranges from painting, to covering with maps and the brown paper bag technique that will make the cabinet look like a fancy worn leather. The image below shows a finished foam cabinet with the brown paper bag technique for a nice finish, stained and polyurethaned luan for an attractive counter top, and cheap 1/2″ aluminum angle to dress out the edges (weighing a grand total of about 7 lbs!). There are so many possibility for finishing that you are only limited by your imagination!
By "Into The Mystery 13"
FULL WRITE UP: http://intothemystery13.com/ultra-light ... technique/