Author: Paul Jarvis, 18/11/05.
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This guide will produce a light-weight 120cm x 39cm custom board with medium flex and accentuated tip flex at a respectable 1.9 kg bare weight.
I produced this site because this procedure to atain a "Holy Grail" of 1.9 Kg in a board that didnt snap took me a year of learning and six “prototype” boards (which all had minor faults or worse - snapped !) to refine. It is a result of a lot of research, mainly on groups.yahoo.com! (You will need to sign in as a user, free of charge, on Yahoo to join this group).
Although learning by mistakes was interesting and despite the great information given on Yahoo, this was occasionally a dissapointing and costly learning curve, and a step by step guide for hand layup did not appear to be available.
Method: Many board builders now use vacuum-bagging which can give some savings in weight, production time and finishing time, but requires sourcing extra equipment another complexity and another learning curve. I decided that it wasn’t worth this extra hassle for the small number of boards I was going to make and decided to stick with the classic method of hand lay-up throughout which I have found simple and adequate for my purposes.
I started out with Eric Hertzens plyfoam construction (which was too heavy and of no structural value !) using a rocker table and included a Formica bottom sheet on my first boards, however, it was hit and miss getting full bonding of the Formica without vacuum on the rocker table, and any air bubbles between the formica and foam caused a weak spot and breakage.
Finally I decided to drop the Formica (which saved weight) and I formulated a method which even did away with the rocker table ! This method of "pulling" in the rocker and concave I found to be quicker, simpler and more suitable for the hand lay up method I was using.
Materials: West epoxy system from Westsystem.com, A500 Corecell foam from marineware.com, foamed PVC rails ( I use the backing panels used for external vinyl display signs). Glass cloth 125 g / sq m in 125cm width (this width saves a lot of wastage on a 120cm board as the "cloth width" can be used for the length of the board) from cyb-glassfibre.co.uk
The main tools are an angle grinder with disc for cutting cured resin flashing and various sander attachments for rough shaping, a jigsaw, a sanding block for final shaping, files etc. A credit card is ideal spreading resin when laminating.
Cut the Corecell A500 sheet (15mm thickness) to the outline shape. Note that the outline of the foam blank must be reduced 10mm to allow for the rails. Trace the edges of this foam blank on to the 5mm thick PVC and cut the rails (10mm wide) to match the outline of the blank. Sand the rails (course sandpaper 80 grit) ready for bonding.
Place grease-proof paper below and glue the rails to the foam with thickened "bonding" epoxy on a flat surface, hold the rails in position overnight with tacks.
Bonding the rails;
Turn the board over and sand off the paper and resin residue from the underside of the rails to give a flat finish, don’t worry about gaps at the rail as these can be filled at the next stage, the lay-up.
Roughly shape the deck close to the final shape in order to thin the foam which will allow it to flex more so that the rocker and concave to be pulled, and more importantly held, in the board by the laminate.
Leave excess foam wedges (see photo) at the ends to allow for screw fixings for pulling the rocker in. Attach a piece of wood with a central bolt using two screws where the handle fixings are to be, place foam wedges at the rails and use this central fixing to pull the concave in to the foam. Attach screws at the end of the board to pull in the rocker.
Fixings for pulling in the concave and rocker:
Board is shown fixed to table with concave and rocker pulled in to it and ready for laminating. Supports should be at the edges only to give a tapering concave (NOT across the centre as shown in the second photo below).
The foam must be sanded smooth, then all dust removed from the foam cells using a vacuum cleaner, it must be totally clean and free from all dust.
The bottom lay-up is four layers of 125 g / sq m plain weave glass. The cloth is cut roughly to shape allowing a few centimetres excess at the edges, each layer is rolled up so it is ready to use.
Thickened resin can be used to fill any holes in the foam and this left to gel slightly, then a slightly thickened coat of epoxy is spread (a credit card is a great spreading tool) on the foam to fill the open foam cells and “wet-out” the foam and give good bonding of the first laminate. I make up about 80 to 100 grams (mix is 1:5 so 16g : 80g) of resin at a time and this is about enough to wet out the foam, or add one layer of cloth. Add pigment at 5% to each batch of resin if a base colour is required. I use white pigment.
Carefully roll the first layer of glass cloth out on to the foam starting at one end of the board and spread it out flat using your hands, then wet out the glass using as little resin as is necessary. Pour the resin along the centre line and spread it out quickly and evenly using smooth gentle strokes, avoid snagging or pulling the cloth weave with the spreader.
One at a time, roll out the other three layers of cloth smoothing and wetting out each layer as described above.
Once the final laminate is tacky (after about an hour or two), a thin final coat or two of slightly thickened resin can then be applied with a credit card in order to just fill the weave of the cloth and give a smooth finish. I find that slightly thickening this final coat makes it easier to get a smoother finish as it runs less and will hopefully also give a tougher finish.
Leave the laminate to fully cure, then remove the board and cut the most of the excess cloth from the edges, I find careful use of an angle-grinder disc is a very quick method.
Finished bottom laminate and rocker fixings:
Next cut off the flashing cloth and mark the positions of the fin inserts and cut out the foam down to the bottom laminate taking great care not to score the bottom laminate.
Mark the positions of the threaded inserts (I use a drilled template) and carefully cut out the foam to the required depth, wet out the foam first with resin then bond them all in with thickened bonding resin.
Important Note…. Insert the threaded inserts so that they are about 1 mm proud of the surface to allow for the thickness of the deck laminate. Fin inserts are simply made from pieces of abraded 5 mm plastic rail material.
The photo below shows a drilled Perspex “hole template” for the fin fixing holes, footstrap inserts and handle inserts, the strap inserts are shown glued in place 1mm proud of the surface, and the central deck area foam has been marked with < > just outside the foot-straps to locate the position of the first two layers of “foot area” reinforcing glass cloth.
Add pigment at 5% to each batch of resin if a base colour is required, I use white pigment.
Roll out the first layer of cloth on to the wetted foam and wet it out to just past the < > markings at the central deck area, then roll out the second layer of cloth ensuring it is straight and there are no wrinkles, again wet this layer out to the markings.
Then lift the cloth at the < > markings and cut it along these lines. Lay it flat again, then wet out the top two layers of cloth on top, these two should cover the entire deck area. Ensure that each layer of cloth is only just wetted (excess resin will cause wrinkles and bubbles and cause the cloth to float) and that the weave is not distorted or wrinkled.
The heel areas will need reinforcement and I use two layers of 180gsm carbon cloth cut to the shape of the heel of the deck pads, if using plain glass cloth, more layers would be needed.
After an hour or two when the resin has gelled, add a smooth finish coat or two of resin to just fill the weave. The photo below shows the finished deck with heel reinforcements.
The photos below show the dried deck with the heel pads sanded down and the insert cap drilled off (with an intact insert beside it). The next photo shows the finished deck with the flashing removed and rails shaped with a sanding block.
Prepare for painting with wet and dry paper making sure you only sand the surface resin and don’t remove the glass cloth.
Drill the fins positions using a template and spray paint the board (matt finish will hide any surface imperfections).
1) The most basic and common problem that occurs for a newbie builder is that the board ends up weighing considerably more than the desired weight, even as little as 100 to 500 grams can be classed as “considerably more”. A 120 cm board of 2.3 KG bare weight will feel fairly heavy in the hand compared to a 1.9 KG board !
The solution is that you have to consider and minimise the weight of every component you add to the board during construction, while still maintaining strength.
For example, you would not normally consider it, but even the finish adds weight, a couple of layers of varnish would add say 100 grams, car spray paint will add less as the VOC’s evaporate.
Along with the glass and foam, resin is one the heaviest components and is the most likely to cause excess weight as the amount added can be varied. So use resin very sparingly where possible, especially during lay-up, but also when bonding components etc.
The combination of two smaller layers of cloth then two full layers at the deck is a bonus as it is not only utilised to give flex at the tips, it also saves the weight of cloth and resin, which is probably about 150 g, at that area where strength is not required.
I have reduced the glass and hence the resin used during development, and may be I could lose another layer of glass (or part of), but the general rule seems to be to have a total of at least 500 to 600 grams per square metre on the top and bottom of the board.
I have 500 g / sq m per side, and I think overall strength would be compromised with less.
2) Corecell foam may be perforated, so when laying up the bottom, you will need to cover the holes with thickened resin and allow it to gel for 15 minutes before laminating the bottom. If not, resin will drip through the board to the deck and cause problems.
3) It is by far best to complete the laying up and finishing in one go, i.e. on one day, because if the resin cures past the gel phase (a few hours), further coats will not chemically bond to it and a waxy residue will form on the surface. If this happens it will need to be left to cure fully then wet-sanded and washed to remove the waxy residue. If this is not done thoroughly, the finishing layer of resin will “fish-eye” as shown in the photo below.
Waiting for the boat after a great dayz kiting on Coche, Margarita
The lovely Vikki... mmmm :)