Most snowboard cores are built using vertically laminated strips of various woods to take advantage of the properties of each. Softwoods are used to keep the weight down, with hardwoods placed in strategic areas to add local reinforcement. These strips are known as stringers. Softwoods to consider are poplar, spruce, aspen - long fibred light strong timber. Hardwoods include ash, beech and birch - dense hard woods. I personally prefer spruce and ash cores - ash is nice and elastic and good to work with while not being as heavy as some other hardwoods. Other woods which can be integrated into the core include balsa, bamboo and even end-grained plywood. They each offer a certain property which when strategically placed can add pop, or reduce weight. It`s a fine balance between strength, weight and riding quality.
Building a vertically laminated snowboard core ideally requires the following tools :
o Small circular saw or bandsaw
o Thickness planer ideally - or hand belt sander
o Micrometer to measure thickness accurately
o `Forester` recess cutting drill bit ~19mm
o Centre drill bit ~10mm
o Electric drill and drill press ideally
o Router and wide cutting bit ~20mm
o Router-bridge jig
o Various clamps including ~35cm quick release sash clamps
^ Ash and Spruce Planks
The first thing to do is to construct the core block - a rectangular block of vertically laminated wood strips. If you have a thickness planer, you`ll be able to remove a lot of material easily. In this case you can build the core block significantly thicker than the target core - eg 10mm thick for a 7mm core. This makes it easier to get the core block flat and remove all the excess glue. Without a thickness planer you should make the core block the correct thickness, and sand off the excess glue after using a belt or orbital sander. Slice strips of wood off the planks using a circular saw or bandsaw, all the same thickness and as wide as necessary. I use 20 - 25mm core strips on my boards.
^ Dan slices strips of wood on the circular saw
Using a suitable wood glue - I use PVA - glue the strips together all the way down the length. Don`t forget to mask off the table below ! Use steel bars to hold the strips down and prevent them rucking up, and 35cm quick release sash clamps to push the strips together. If you first tighten the bars across just enough, you can then use the sash clamps to force the strips together and they won`t come apart as you tighten the bars doen fully to hold them in place. Leave this overnight to dry thoroughly.
^ Core block, glued and clamped in place
Once the core block is fully glued together you need to remove the excess glue. This is where a thickness planer really helps - you can do it quickly and cleanly. Next best thing is a hand-belt sander with a coarse belt. Get rid of all that PVA as it won`t bond properly - unlike the wood.
With the thicknesser, now is the time to plane the core down to your target thickness. Use the micrometer to gauge the thickness and ensure you`re not going to overshoot.
When the core block is cleaned up and ready to proceed, clamp your template to it. We use a steel template laser cut from our snoCAD DXF file.
^ Midway through routing the core using the steel template
Use a flush router bit - with a bearing above the cutting head which is the same width as the cutter. This makes sure that the core is exactly the same size as the template. If you clamp it from the sides like we do, you`ll need to move the clamps part way through the cut. To avoid moving the core and template, don`t forget to fix the new clamps in position before removing the old ones. Our templates feature tiny holes along the principal axes to mark out the beginning of the tips, the nose, the tail and the centre. We also have insert holes cut in the template. While it`s clamped to the core it`s a good idea to trace these onto the core so that they can be accurately drilled afterwards.
^ Snowboard shaped core blank
The insert holes have to be placed as accurately as possible and the holes need to be as vertical as you can get them. Insert misalignment makes it tricky to fit bindings later - especially if the discs don`t give you much leeway. I use a drill-press (the kind the electric hand drill clamps into) to ensure my holes are vertical and accurate.
^ Drill press set up for insert holes
The first holes to drill are the ones to produce the recess for the base of your inserts. The inserts must be 100% flush with the core - not below, not above - flush ! I carefully align the centre of the forester bit with the centremark of my insert hole. The first recess is cut slowly and I keep checking the depth until it`s exactly the thickness of the insert base. Then I set the `stop` on the drill press to ensure all the other holes go to the same depth and drill them too.
^ Recesses cut with a 19mm forester bit
Once all the recesses are cut, you`ll have a handy centremark in the middle of each. This can then be used to align the drill for the head of the insert. To drill this part, ideally you need a centre-drill the same width as the insert head. My inserts have 10mm heads. The centre-drill features a pointed tip which tapers to the full width, and is short and stout. This prevents it from wandering while cutting, and guarantees a well aligned hole. Using the drill press and the centre-drill it should be easy to drill for the insert heads.
^ 4 x 4 insert holes and the centre-drill used to make the inner hole
The next step is to glue your sidewalls to the core. This needs to be done with care as you must attempt to get as much of the sidewall inside the board as possible yet keep enough overhanging so that any small misalignments do not result in the sidewall being inside the steel edge. My sidewall material is UHMWPE (Durasurf) and comes in 8mm thick planks, abraded and flamed on one side for bonding. I laminate a sheet of wood veneer to the treated side. The wood gives me an easy way to glue the sidewall to the core using wood glue.
Slice off sidewalls from the plank using the circular saw. I have had trouble doing this on a bandsaw due to melting plastic getting everywhere. The width of the strips should be chosen to correspond to the thickness of the core.
You may need to cut a recess in the core using a jigsaw to get the sidewall material sufficiently inboard of the edge. My sidewall is 8mm wide. The core is the same size as the base. The edges add 2mm to the base. If I recess my sidewalls 5mm into the core, 2mm will sit directly over the edges. This gives me a spare 1mm overhanging the edges in case of misalignment. It`s not a lot but it works for me. I get 7mm inside the core. Remember how much sidewall is inside the core as it will help you figure out what angle the sidewall can be machined to later. In my case, 7mm tall by 7mm wide means that 45` might be a bit too close. I`ll use 30` on these sidewalls.
^ The sidewalls glued to the core
Snowboards are not the same thickness along their length. They taper outside the bindings towards the tips, and may be thinner - or thicker - between your feet.
So how on earth do we achieve this in our garage ?
One technique - and one used by a lot of home builders - is the `router bridge` method. This involves building a jig to guide the router in a smooth path along the length of the board, smoothly controlling it`s height above the wood. Our jig uses two hinged guides - one at each side of the base board. These can be adjusted to the correct angle using a screw adjuster. The router sits upon a wooden `bridge` which rides up the guide beams at each side. The router is able to move side-to-side on the bridge.
^ Dan uses the router bridge to profile the core
You are best routing in two passes - one to remove about half the material. It puts less strain on the core and the sidewalls especially and prevents catastrophic destruction. I also cut to the right, in accordance with the bit I use, then run over the same area right-to-left as I return for the next cut. This cleans up any rough areas and leaves a finish which needs very little sanding.
^ The profiled tip ready for sanding
^ The router bridge, showing the router riding up the guide bars on the bridge
^ Router bridge viewed from above
^ The flat part of the tip during profiling - here the tip has been routed and the taper will be done next - usually in 2 passes
Another method which I favour these days is the planer jig method. This involves using a thickness planer to cut the taper. It is a very fast method of cutting the taper, and if done well is very accurate. However there are numerous pitfalls - the planer is a monster and will easily snipe and damage cores. The way to avoid this is to hold the core down very well - our planer jig uses 3 mechanisms - grip tape to prevent on-axis sliding, screwtips sticking up to bite into the underside of the core and prevent slippage, and hot-glue (between protective layers of duct tape) to hold everything down. We also pass the core and jig through the planer low-side first so the planer blade does not have to collide with the tip of the core but progressively bites into the core which rises on the jig to meet it.
^ Our planer jig with a core in place
We use hot glue across the very tip, across the widest point of the core, and just in front of the inserts to hold the core firmly down to the jig. If we hot-glued the core directly to the jig it would be hard to remove, and there would be glue residue all over the core and jig. We put strips of duct tape across the jig and in corresponding places across the underside of the core. The hot glue goes between the layers of duct tape. Removing the core from the jig is a matter of unpeeling the tape, which comes away beautifully cleanly.
When profiling on the planer, be patient and take material off in little steps - especially as the material gets thinner. We begin removing 0.5mm per pass and as the cut progresses and the material thickness approaches 1.5mm we reduce this to 0.25mm per pass. With two people passing the jig back and forth it is surprising how quickly the core can be profiled.
Our jig is made of two sheets of MDF using aluminium strips as spacers to set the required profile. We have chosen a configuration which works pretty universally if the core is positioned in the right place for the size of the board being built, so we do not adjust the jig very often.
The last stages of production are to trim the tip of the core and fit a tipspacer. Simplest tipspacers are made by using base material. Cut a shaped recess into the tips and make a matching section in plastic to close out the edges of the wood.
The sidewalls must also be thoroughly sanded on both sides best using a belt sander. Then flame treat the plastic using a blowtorch - run the torch over the sidewall at about 2.5cm per secord - until it just slightly yellows. Don`t forget to do both sides. The inserts can be fitted just before layup - the holes being painted with epoxy and the inserts pushed into the holes.