The next step of this project was to make the blank. This part of the project was not as straightforward as one would have imagined. The idea was simple: “glue the two pieces of foam together with the stringer in the middle”. However, there were a few challenges:
- There was a hole in the middle of the foam, where the old “stringer” used to live.
- I planned to introduce a flatter rocker than the original soft-top surfboard.
- I didn’t have any glue.
- I did not have any suitable clamps.
I went out and purchased some polyurethane glue. This glue is suitable for gluing a range of materials and surfaces, and it wasn’t going to melt or damage the polystyrene foam. It also has a slight foaming action allowing it to expand and fill small cracks. This solved my glue problem, but the foaming action was not going to be enough to fill the holes in the foam left by the hardwood “stringer”.
Filling the holes
I found a piece of packing polystyrene and cut out small rectangular boxes to be inserted where the hole was. I then used the polyurethane glue to glue the pieces in. Surprisingly, I used almost 250mL of glue just to fill the holes!
Once the holes were filled, the glue had dried, and I had sanded the surface flat, I had to come up with a way to clamp the two halves together. I needed to hold the board together to allow the polyurethane glue to dry well, and needed a way to press and hold the foam to the rocker of the stringer. I tested out using flat pieces of wood to press the foam to the stringer. This is what the test run looked like:
It worked! But it needed some improvements. It definitely needed more pressure between the top and bottom to flatten the rocker of the foam to the rocker of the stringer. I added more wood and tightened the straps to add more force in that axis. I also added cardboard between the straps and the foam to distribute the pressure and protect the rails from a point load.
I spread the polyurethane glue on the stringer with a comb and put it on one of the foam halves. It was messy! Glue was dripping everywhere! I spread the glue on the other side of the stringer and tried to place the other half of foam where it belonged. It quickly escalated into a gluey mess, as the rocker was different and the glue quite liquid.
I had prepared for clamping by placing the straps on the table, with pieces of wood along the length of the table so that I could place the foam on the table after gluing and strap everything together. The only issue was that the whole mess kept falling apart. After much gluing of my hands, clothes, and other random objects, I finally managed to hold the to-be blank in place temporarily. Quickly, I clamped the front and back with standard clamps and some leftover plywood. I loosened the straps to place the wood in between the straps and the foam. BIG MISTAKE. The mess came apart again!
Unfortunately, that meant that I didn’t take any photos during that stage…probably for the best. Eventually, the blank ended up looking like the picture below with the cardboard pieces to protect the rails, and extra pieces of wood to add more pressure top and bottom. FIRST TRY!
(Note: this type of glue expands more if there is a bit of moisture, so I sprayed some mist at the glue to help it fill any gaps better)