|Here is the final product: A horizontally laminated drop deck longboard with drop through truck mounting.|
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The rest of this post will be about horizontal lamination longboards. I built a few v-lam longboards at the end of the last school year, and it was pretty easy, but I thought that the h-lam boards would be a lot harder. It turns out that the opposite is true. Horizontal lamination is like making your own plywood, and it is how the vast majority of factory-made skateboards are built.
In the DIY skateboard movement, there are two major methods for h-lam construction. The first is to use 1/16" maple veneer sheets, and to glue them together with a foam mold in a vacuum bag. There is a company called Roarockit that sells everything you need to make that happen, and they are very involved in building skateboards in an educational environment. It is apparently very easy. The second method is to use 1/8" sheets of Baltic birch, and press them in a physical press with clamps. This is the method I will be discussing. Compared to the maple-in-the-vacuum-bag method, Baltic birch boards are a bit weaker, less resistant to chips and dings, and you can't shape 1/8" thick Baltic birch into as tight of bends as 1/16" maple.
There is one major advantage though, and that is that you can often buy Baltic birch from local lumber yards and specialty wood suppliers, while maple is only available in most places online through skateboard building suppliers. 1/8" Baltic birch is actually a 3-ply plywood, and you won't find it at a home improvement store like Lowes or Home Depot. They sell plywood there with birch outer veneers (and who knows what on the insides) in a 4 x 8 foot sheet, but you need the 5 x 5 foot sheet, not for its size, but for the birch all the way through and lack of voids in every ply. I live in Springfield, MO, and I buy mine locally from OP Hardwoods for $25 a sheet. There is a strong possibility that the place that sells Baltic birch in your town won't have a website, so you'll need to pick up the phone book. One 5 x 5 sheet is enough to build two big 4-ply boards (four plys of three ply plywood), which may be a bit flexy if you are heavy, or almost two big 5-ply boards, which will be stiffer.
Here's how I build my skateboards:
First, build your press. This is nothing more than a 48" x 14" piece of low grade 3/4" thick plywood with two 48" x 3" pieces glued and screwed to the bottom, 3" in from the sides. Try to make sure everything is square and flat. The pieces of wood on the top are just laying there, and are not attached. After I took this picture I drew a centerline down the middle from end to end, and also from side to side. I also made lines in 1" increments from both centerlines all the way across, and labeled them with just even numbers, starting in the middle. This way you can easily center your forms and plywood. In other words, the lines on either side of the centerline are both labeled 2", the next two are labeled 4", and so on. This way, if you have a 38" long piece of plywood that you want to center, you can place it with each end on a line that says 38" and know it is centered in the press.
Next I made my pressed forms. The two end pieces hold the truck-mounting flats flat, the two center ones form my concave, and the two next-to-end pieces form my drops. You will notice that one of the two drop-forming pieces is square and the other has angles. On my first press with this form the angled one did not adequately press the edges of the Baltic birch, and there were minor gaps between my plys on that end. For the most part, 1/8" Baltic birch wants to be flat, and all of the pieces will naturally press together when you squish it all together, but you have to watch out.
Your next step will be to cut your Baltic birch into your lamination pieces. The grain orientation is important here. The sheet will bend more easily in one direction than the other. Notice that it does not bend as well in the direction that the grain is running on the outside plys (the grain is running the other way on the inside ply). Ideally you will want the outside ply grain running along the length of your skateboard. I purchased an already-cut piece of plywood at a discount for my first try, and I was unable to get all five plys to run lengthwise, so I put the single sideways grain ply in the very middle of the stack of five to minimize the effect of its easy lengthwise bending. You can cut a 60" x 60" (5' x 5') sheet into six ~10" wide x 40" long lengthwise grain pieces, and two ~10" wide x 40" long pieces with the grain running sideways. I have not done experiments to determine the perfect placement of that sideways grain piece in a 4-ply longboard, but I'm pretty sure it should be one of the two center pieces, and probably the upper one.
A note about the number of plys vs. flex: I used 5 plys of 3-ply 1/8" Baltic birch, with the middle ply having its grain (on the outside plys) running sideways. The centers of the truck mounting baseplates are about 32" away from each other (the wheelbase), and I have significant concave (the bending up at your heels and toes on the sides of the board, which reduces flex lengthwise). I weigh about 165 pounds, and my board has noticeable flex. Personally, I like this, as it makes the road feel smoother, but many downhillers going for speed do not like this. A layer of fiberglass on the bottom of the board is the common solution to reduce flex, but that's a whole other setup in the classroom.
Now it's time for a dry-clamping. Lots of big c-clamps are helpful here. After I built this board (and not pictured) I drilled a series of 3/8" diameter holes 1" apart all the way down both sides of the press table. Through this I put 7" tall 3/8" all-thread rod, which I attached to the table with nuts and washers. Then I drilled matching holes just a bit bigger than 3/8" in the pressed forms. Now I can use threaded rod instead of using all those c-clamps, which are needed in the other, non-skateboard-building periods while the glued deck drys. I only put the threaded rod in the holes where they are needed for the pressed form pieces. Threaded rod in every hole would make turning a wrench awkward.
The next step is to apply glue to both sides of each piece of Baltic birch, except for the top of the top and bottom of the bottom pieces. I used a lot of Titebond III and a coarse paint roller. You could also spread it with a spreader or a stiff paintbrush. I felt like I ended up with a lot of glue in the roller when I washed it, which is somewhat wasteful, but whatever.
I pulled my board out after 6 hours. Even for my first attempt, I could not believe how well everything turned out. I had some slight delamination on the edges at the bottom of the drop (as discussed earlier), but other than that it was very solid. I filled those spots with more wood glue and clamped them back down overnight.
OK, so I've got a 4 x 4 foot Shopbot CNC router in my wood shop, and I love it. By trade I'm a designer and drafter, so it plays right into my strengths. It makes life so easy at this stage of the process, which is cutting your board to shape. Now, the whole point of the wood shop class that I'm building skateboards in is to introduce students to the CNC, so this is perfect. If you don't have a CNC, now is the time to draw your longboard profile by hand, or from a pattern, or by tracing an already completed board, and cut it on the bandsaw or jigsaw. For me though, now was the time to draw my board on the computer. I used Autodesk Inventor 2015, but I would have preferred AutoCAD 2000. It is ideal for this type of work. If you have a CNC, you probably already know how to use it, but I will offer this one useful tip. Set the origin of your design to the left side of the board, right on the centerline. It is always easiest and most accurate to work from the centerline of your board as opposed to a corner. You can see in the pictures below that I marked the centerline of my board for positioning on the CNC bed. Make sure you mount your cutting bit deep enough to clear the curvy sections too. Your material thickness will be the distance from the top of the highest part of the board to the table. I cut through the air a lot before the sides got cut.
You may notice that I did not cut my truck holes at this point. The reason for that is that I hadn't chosen my trucks yet (I have since purchased Independent 169s) and I wasn't sure where my wheels would contact my board, so I may need to move those around as I decide where they go, and I'll probably drill those holes by hand. In my experience it is critical that you use a guide to drill the holes. On my first board my bits walked (even though I used a center punch) and I had to waller them out to get everything to fit right, which was just unprofessional. I now use a truck riser as my guide. If I did know what I was doing, truck-wise, you can bet I would have drilled my mounting holes on the CNC.
Here is what it looks like after sanding the surfaces and corners, and a single coat of Minwax Polycrylic. I used to use Minwax Polyurethane on my boards for the superior durability, but I have found that it yellows badly with time. I don't have any long-term observations with the polycrylic yet.
I wanted my students to be able to add some graphics, and I researched rice paper printing and water slide decal methods, but both seemed like a hassle, didn't involve any woodworking equipment objectives, and didn't seem like they were going to look that great anyway. I decided to make a Sharpie holder for my CNC so that we could draw or download some graphics and have the CNC draw them for us.
I only drew the outline of the graphics on the CNC, so I had to color it in by hand. I'm not sure what would have happened if I had made the CNC fill it in, but it probably would have taken all day. I ended up coloring it all in with a Sharpie chisel tip. It is important to note that you must put a coat of finish on your board before you use a Sharpie, or the ink will run with the grain and make everything blurry in one direction. I will put the remainder of my poly coats on over the Sharpie.
Here is the final product, as of yet, between a finished vertical lamination board and a work-in-progress v-lam. Note that the light wood on the left polyurethaned board and the light wood on the right unfinished board is maple from the same board. I am not into that yellowing.
At this point all it needs is the grip tape and truck holes to be considered a finished deck. You can mount your deck to your trucks in a top-mount configuration (normal style) or, like I did, in a drop through mounting style. A drop through means you mount the base of your trucks to the TOP of the board, so you have to cut a square hole for the body of your baseplate to pass though, but just the body, and not the flat surface with the mounting holes. This lowers your deck by the thickness of your deck plus the thickness of your truck mounting baseplate surface. I used my CNC to cut the holes for the truck baseplate body, but hand drilled the 3/16" mounting holes using the baseplate holes as a guide.
I finished my board off with Independent 169 trucks, ABEC 11 Freeride wheels, and Bones Reds bearings. My grip tape was not quite wide enough, so I added a stylish stripe to make it wider.
I recently purchased a longboard truck, wheel, and bearing combo package from Amazon, and the trucks were so badly constructed that they were almost unusable. The kingpin fit very loose in the baseplate, but I have a plan to fix the kingpin in the baseplate with JB Weld to make them usable. It's tough to beat a sub $40 wheels, trucks, and bearings package on price, but that's probably what's in my student's price range.
I gathered almost everything I know from the Longboard Building Forum at Silverfishlongboarding.com.
There is a giant trove of downloadable longboard shape templates on those forums here.
Other common types of Baltic birch DIY longboard presses are the Toothless and the Dimm.
Edit 8/16/15: added picture of final product, notes about drop-through truck mounting, and 5 ply flex.