Made another board from pieces of XPS foam I get as coolers in the mail. The foam is 1.5" thick and up to 11" square, but not all the foam is 11", most is about 9" square. I had more than enough for another board, so I made a board for a standing wave pool.
I start with a stringer I made from spicing 4’ long model airplane Balsa sheets, then cut the foam to match the rocker. I glue up rocker pieces 2 layers thick overlapping the joints, then glue them all together to make a wide enough blank based on an outline I have in mind. Once I have all the foam glued up, I shape it by hand with my planer, surforms and a bunch of homemade sanding blocks. I have several blocks with curves to make concaves and this board has a double barrel concave or spiral vee.
It was supposed to be 5’ but I add a 1" perimeter strip of foam to get a cleaner rail and it ended up 5’ 2".
All the shaping is done with an electric planer, surforms, and sanding blocks. I don’t have a good hot wire, but if I did, I could use the hot wire. Hot wiring XPS is supposed to be more toxic though.
I use a rocker template and I draw the rocker onto the foam. I lay out pieces of foam to get the length, then I draw the rocker. I lay out the foam in 2 layers that have the breaks alternating to have the glue lines backed against solid foam. The foam pieces are only 1.5" thick and are squares that are only up to 11". Once the rocker is drawn out, I cut the foam with a small band saw, but I can use a jig saw or a hand saw. I cut out 2 layers of foam to make a single 3" wide rocker slice, I glue them together using the rocker template to make sure they will be set right. I cut the foam about 1/4" wider than the line and it gives me some play when I glue multiple rocker slices together to get the width. I only put a narrow bead of glue down the center of the foam to avoid having hard glue lines to cut through, but sometimes I end up with glue spilling out and I have to cut through that when I shape.
I have the outline pre-drawn on paper but it is narrower than the final because I add a 1" perimeter rail that is a single long piece. I use the narrow outline to know how much foam I need, and I only needed 16.5" for this board. As I get to the outer slices, I only need the middle part of the rocker slice, so I cut shorter sections that are just long enough for the outline. Less waste. Once the rocker slices are glued up, I use a planer and smooth out the foam just a bit higher than the precut wood stringer. Then I re-draw the outline. In this case I changed the outline from the one I started with. I think I ended up with a wider nose than I originally planned to do. I cut out the outline then add the perimeter rail piece and finish shaping the board.
What a job! You are a master of planer.
I bet you would not be happy with hot wire, if you have to cut pu foam glue, lot of distorsion cut.
I use sometimes xps as center stringer to increase my eps block for sup but always scared with epoxy adhesion even if i only had delam on xps rails when boards were dinged
Thanks Lemat!
Lately the XPS has been delaminating with the heat. I never had problems before, but I think climate change is taking effect.
I prefer EPS for the weight and good flotation, but the company sending my wife medication doesn’t use EPS anymore. I like using XPS for rails because if it gets a ding, I don’t have to worry about it and go in right away. Same for using the XPS as the core, but the XPS I’m getting now seems more dense and the flotation is different. I only make these boards because wea box mailed to us about once a month and I don’t think they get recycled properly here.
