Building a Hollow Wooden Surfboard - 6'2" Fish School Project Part 1

Namaste Wiley Wood Workers and welcome to this installment of building a 6'2" Fish hollow wooden surfboard. I was recently contacted by Wally, a manual arts teacher at a High School in Sydney. Wally was interested in introducing a wooden surfboard building module for students in his year 12 Industrial Technology course which would contribute towards their HSC (Higher School Certificate). Being new to wooden surfboard construction but an old hand at woodworking, Wally was looking at doing a couple of wood surfboard builds for his two sons first and then using this experience to refine the process for his students in the school workshop. Lucky Lads. He has access to a state of the art workshop with all the tools including a CNC machine and a laser cutter. The school kids were totally stoked about building wood surfboards for themselves in school time, I was totally stoked to be involved and Wally was just generally stoked that it was all starting to come together.

Multicam M1 CNC router with 950 mm x 1150 mm bed. A nice addition to any workshop and a  permanent fixture in Wally's.

Epilog Laser 45W with 610 mm x 457 mm bed. This is an awesome machine also in Wally's workshop. It not only cuts but it can also burn artwork into your wood surfboard.

DESIGN

The first step was to gather some design requirements. They were as follows: a Fish style board, and 6'2" in length. A little light on but a good start. So we did a little research and put together a summary of Fish design attributes. This is by no means definitive but helpful in putting together a Fish design.

A wide nose with a slight point which is stable and maneuverable.

A wide thick board for buoyancy and stability making the board easy to paddle and stable to ride. A little like me.

A flatter rocker for speed and ease of catching waves.

A wide tail (with swallow tail) – a couple of reasons for this. Easy to turn but also a higher aspect ratio (tail width to board length) to assist the board in getting up on the plane.

Thick rails through the middle, sharp at the tail.

Fin setups – twin, quad and thruster. Why not go for all three and install 5 sets of fin plugs and interchange the fin setups as required.

Fish plan shapes can vary from classic shapes to modern hybrids.

Volume. Now this is a personal preference and dependent on how much buoyancy is preferred and how much paddle power is on tap. Some guys like less, some more. I approach this from a couple of angles.

1. If someone has a favourite surfboard that they enjoy surfing, I assume the volume of that particular board is okay and I measure it using AKU Shaper. I photograph the outline and side profile and use the images to do a rough design of the board in software. Once the design is complete, AKU calculates the board volume (in beers or litres). I've never really understood the metric system so I work in beers.

2. I use a rough formula of 0.6 x body weight of the surfer (The Cater Formula). This seems to work well for the average surfer. My coefficient is a bit higher (about 0.7) because I am a fat, lazy, paddle-phobic chimp.

In this case we used the formula and settled on a volume of 45 litres.

So after a few iterations in AKU we went with a 6'2" x 22 ¾” x 2 ¾” and 45 litres in volume with a flat bottom contour and slightly sharp rails towards the back. The rails up the side are quite full (60/40). 45 litres is probably a good volume for a 70+ kg person. The ribs have been spaced at 150 mm with the deck and hull fibre glassed internally to give the board added strength and longevity.

Here's a screen shot of the wooden surfboard outline in AKU Shaper. AKU Shaper doesn't seem to like designing swallow tails so I've had to go with a square tail in the design. The swallow tail can be drawn manually on templates in the work shop or added in CAD software. The outside centre point for the swallow tail is 110 mm from the tail end.

The view of the rocker/profile.

The first slice near the nose. Slices spaced at 150 mm.

The centre slice.

The tail slice at 170 mm from the board rear.

The final set of templates produced by Hollow Board Template Maker. This PDF file was converted to a DXF file, cleaned up and imported into the CNC software as machine code. 

The next section will be of interest to those of you wanting to use a CNC machine to cut out your wooden board templates.

Converting PDF File to DXF Files.

Wally's first challenge was to convert the PDF file produced by the Hollow Board Template Maker software into a form that he could use on his CNC Router and Laser Technologies. After a number of phone calls and trials of PDF to DXF converters online he succeeded with Aide DXF PDF Converter. This software was easy to use and produced DXF files with curves which were polylines and relatively simple to edit.

The DXF file opened in Autocad 2013.

 Many hours late at night were spent working out how to best edit the DXF drawing in Auto CAD. The DXF file was 19,529KB (almost 20 Meg) and when saved as a DWG file it was much smaller at 1,616KB. It was much quicker to edit as a DWG file.

EDITING

One of the first issues Wally had to deal with was mulitple lines under lines which is a problem with CNC machines. The skin lines on the rails needed to be deleted. The best way to overcome this was to select each entity by clicking each polyline and not clicking and dragging the mouse. This ensures that only the top layer of entities are selected. Select the smaller lines first, as they are much easier to see. 

Use the zoom function to to make sure all entities are selected. Don’t select the shaded areas of the spline. Once selected use the "Move" command to move entities to the right of the existing lines. Duplicate lines will be left and can be deleted.

Use the Trim Command to select lines 1-5 shown above then right click and select the parts of line to Trim. Remove the lines near the center spline first to avoid problems with the others.

A continuous loop is more difficult to Trim. Zoom in and draw a line close to the intersection and then use the Trim command. Then use the Chamfer command to clean up any corners. If at any stage the entities don’t Trim properly use the Extend Command to ensure the entities are in contact to enable Trimming.

PEDIT COMMAND

PEDIT is used to combine entities into a continuous loop needed for the CNC machine. To join lines to form polylines in a continuous loop, type PEDIT, Enter,  Press down arrow, then click Multiple, select all the entities, Enter, Join, fuzz Distance 2.

Move the mouse cursor over the joined entities and ensure that they have joined correctly. If the line doesn't form a complete loop, zoom in and search for the reason why.

 
The drawing needs to be scaled to size. Measure a known entity and scale to correct size.

When all entities have been cleaned up and the PEDIT Command used to close polylines Save file as a R12 DXF. Import file into the CNC software in Wally's case Multicam Toolpath and look for open shapes.

The green shapes are open shapes and need to be checked to determine why they haven’t joined properly. Wally found that main problem was that the corners were not trimmed. Also some curved shapes had a small gap near the spline. He used the Trim, Extend and Chamfer commands as a means of editing the entities.

At this stage he found it helpful to check for duplicated entities. He clicked on each entity and moved it aside to determine if multiple entities existed. He found a few which were deleted. The PEDIT and JOIN Commands were used extensively to join entities.

There is a problem in the Multicam Toolpath software. Wally could not reverse (for the mortice) the machining parameters from outside (blue) to inside (red). This stumped him for a few days until he Exploded one of the rectangles and found a duplicate shape underneath.

The next step was to do a trial run on the CNC machine using MDF board.

The detail of the dovetail joint for the spine and rails. The spine and rails have been cut in two sections so that they fit within the bed dimensions of the CNC machine.

 Heavy duty rocker table also designed by Wally.

The rocker table fresh from the CNC machine. Still warm!

The rocker tables getting glued up. One for the Fish and another for a 9'1" longboard.


The Fish frame cut in MDF to make sure it all fits together. The production frame will be cut out of 6 mm paulownia.

 Another photo of the MDF frame.

And from above.

More to come in Part 2 (Due sometime in 2017/2018)

Here's a link to the template file for this board if you are interested in building it.
https://drive.google.com/open?id=0Bz-5_Htew1q5N2l2WGt3NEVWSTA