^ Snowboard materials waiting for layup
^ Durasurf base material off the roll
Snowboard and ski bases are produced from UHMWPE - ultra-high molecular weight polyethylene, a dense hardwearing thermoplastic with low friction, and capable of absorbing wax. The material is flame treated for bonding with epoxy resin. P-TEX and Durasurf are brand names.
Bases are made in two main ways. Extruded bases are made from polyethylene pellets melted down then forced under pressure through a thin slot and rollers which gauge the thickness of the emerging sheet. Extruded bases are cheaper, can be harder wearing but hold less wax, and are slower. The plastic when not dyed is notably clearer than sintered material.
Sintering involves crushing polyethylene pellets together under high pressure. This causes them to melt together and fuse, although tiny porosities are left between the clumps. Then the whole mass is turned, and a blade shaves off a uniformly thick slice as the cylinder rotates. The porosities hold wax, and break down surface tension of water under the base. The result is a faster board.
Both types of material come in clear and coloured variations. Remember, through clear P-Tex you can still see the teeth of your edges, and any bubbles in the resin. This can look a bit messy, and coloured P-Tex prevents this. Graphite bases contain graphite powder added with the pellets. Graphite does several things - it hardens the plastic, decreases the friction coefficient and conducts static electricity - all preventing the board sticking to the snow.
Cut the material with a sharp stanley knife, or router and clamp your template rock steady.
^ Steel edge material
The edges are there to cut into the snow and give you grip in the turns, plus they also protect the board from damage on ice and rocks. Made from steel, the edge consists of a 1.5mm square spine with T-shaped prongs or squares protruding off it at close intervals. These prongs bond into the epoxy and retain the edge in place on the board. Various profiles are available in different sizes, be sure to get the right size for the base material you will be using.
A full perimeter edge wrap needs more bending and is harder to fit, but gives more protection to the board whilst adding a slight weight penalty. Put the join on the tail of the board, and leave plenty of excess edge to act as a lever to help you bend.
A partial wrap is easier, extend the edges into the tip just beyond the contact points. For neatness, a nick should be cut into the base to tuck the edge in and prevent a little resin (weak) triangle blending the end of the edge into the base. You may want to grind the flange off the end of your edge, then bend the flangeless edge inside into the layup to strengthen it against edge blow. This is done by Mervin (Gnu / Lib) and Santa Cruz among others.
The quality of a home-built board can often be judged by the way edges are incorporated, take time and be precise to get good results.
^ Steel edge, bent and tacked to base with cyanoacrylate glue
^ Vertically laminated core blank, made from spruce with beech insert stringers and end-grained ply stringers
The core of the board is the component which most contributes to its performance. The weight, thickness and durability of the core determine the riding characteristics of the board. Most cores are built from vertically laminated strips of wood. Laminated strips make the board stronger - a single plank of wood contains knots and irregularities which will affect the strength and flexural performance of your board. By using many strips these artefacts are reduced and the properties of the core are homogenised.
^ The sidewalls glued to the core
Sidewall designs need to have plastic strips bonded to the outside of the core. The material choice is usually ABS (acrylonitrile butadene styrene) or UHMWPE (P-Tex) both resillient and hardwearing. We use Durasurf (UHMWPE) which comes in large sheets, abraded and flame treated on one side.
^ Raw sheets of Durasurf, before skinning with veneer and slicing into strips
We bond a layer of thin maple veneer to the treated side of the sidewall and use this to give us a wood-to-wood bond with the core. It makes for an easier and stronger process. Use a circular saw to slice strips off the block. A bandsaw tends to melt the plastic too much and wander around.
^ Hex based 6mm stainless snowboard insert with red plastic protective cap
^ 4 x 4 insert holes and the centre-drill used to make the inner hole
Even more crucial is blocking up the insert holes during manufacure. If epoxy resin flows into your inserts they are ruined. Use small sticky circles (cut them from sticky backed plastic with a hole punch). Inserts from snowboard material suppliers usually come with a plastic cap already attached.
Some insert caps are magnetic, which means they can be easily located after pressing using iron filings.
^ UHMWPE tipspacer butt-joints the core in an arc. Excess plastic extends over the perimeter of the base and edge
A tip spacer is a plastic or composite insert used when the core ends before the tip of the board, to fill in the space and close out the walls of the board. It also closes out honeycomb panels used in the tips to safeguard against crushing. Materials to consider are ABS, polyethylene, nylon or glassfibre.
All tip spacers add weight when compared to a full length wood core, but can offer protection against direct impact with rocks and skiers.. The spacer can be left oversize to hang off the side of the board during layup, and can be trimmed afterwards. Glass fibre tip spacers mean adding extra layers of glass in the tips during layup, and is a heavier but very durable construction.
^ Cutting triaxial stitched glassfibre from the roll
Composites are the primary structure of the snowboard and serve also to bond the other components together. A composite material is a combination of two or more seperate component parts which do not actually mix, but cure together to form a single material whose mechanical performance is a sum of the component parts. In snowboarding terms this means a fibre reinforced plastic. The plastic is formed by taking a resin and a hardener or catalyst and combining them to kick off an exothermic reaction. The resin polymerises (forms into long molecular chains) and sets hard into a dense plastic material. Two types of resin are widely available. Polyester resin is the cheapest kind, and smells horrible. When cured it is quite brittle under dynamic loading and is not recommended for high performance sports equipment. Epoxy is tougher, does not smell bad and tends to cure more predictably - it is less likely to go off too quickly and exotherm spoiling the batch. The resin is combined with hardener, and stirred up to begin reacting. Pigments can be added to colour the finished board, or metalflake particles or other additives can go in. Mixing too vigourously causes bubbles to form in the resin, which weaken the finished structure, so go easy.
^ Epoxy resin is squeegeed onto the top of the core
Glassfibre is the usual reinforcement for snowboards, and comes in woven fabrics of different fibre orientation and density. The weight of the cloth is a measure of the amount of fibre going into the board, and is expressed in grams per square metre (gsm). Structural layers will typically use 300 - 600 gsm fabrics. We tend to use approx 630gsm glass either side of the core, be it as 2 layers of 600gsm glass, or laminated smaller layers to a similar weight. In addition our carbon or glass topsheets use 1 layer of 280gsm material.
^ Encapsulated graphic over a carbon fibre top layer
^ Sublimated topsheet during layup with protective film to keep it clean
The topsheet serves two functions - to protect the structural composite part of the board from abrasion and UV light (eventually breaks down epoxy) - and to retain the board graphics. Material choice varies from PBT, polyethylene, nylon, polyester - and blends of these, or composite. Materials should be thin (300 - 400 microns or <200gsm composites), capable of bonding to epoxy and not too heavy. Proper topsheets often have a fleece material bonded to the back for optimal adhesion with the epoxy. Some topsheet materials are suitable for sublimation, and these usually come in white. Others are suitable for screen-printing and these usually come in colourless transparent.
^ Bondable rubber used above the edges to dampen vibration and improve strength
Bondable rubber strips can be placed above the edges, and they serve two functions. Firstly they dampen unwanted vibrations from the board, leading to better grip on ice and a calmer ride. Secondly they provide a shear layer between the edge and the composite to absorb different rates of expansion in addition to shocks. This increases the strength of the edge.