I want to (finally maybe someday) start my home depot EPS project, but I’m still at a little debate as to how I should cut the rocker. Hotwire cutter sounds good, but unless anyone knows of a pre-made setup, that’s probably out (I’m a mess when it comes to electricity). So I’ve come up with a couple of other options but I don’t know how they’ll work:
Make 2 “side rails” identical to the pre-shaped stringer and ride a long/flat saw blade (bandsaw?) across all three so everything stays square and even. Then somehow cut the outline from there…
Pre-cut the outline of the board, cut the rocker in a similar manner as above but without the pre-cut stringer. Cut the blank in half and glue up to a piece of stringer material and add more rocker if necessary. Then somehow trim away the stringer. What would be the best way to trim it away without going down into the foam?
If you’re using sheets, you probably don’t have the material to cut it with a hot wire anyway, unless you lay up 3 sheets. I would pre-make a stringer exactly as you want the finished board, and then glue the sheets up to it. Probably plenty info in the archives. Good luck.
Glue your sheets to thickness first. Make a pre-shaped stringer out of decent plywood or solid wood. Then make a copy of it out of masonite or extra plywood or whatever. Split your blank lengthwise. Drill some holes - 3 is enough - in your stringer & its clone. Push big nails through the holes to attach the stringer & clone to one of the blank halves. Use a long hand saw, hotwire cutter, bicycle chain (kidding)… whatever you have to cut in the rocker with the stringers as guides. Then do the same to the other half of the blank.
Glue both halves to the good stringer with Gorilla Glue. Clamp with blue tape or stretch wrap around the whole thing. When its dry - you’ll know because the foaming drips will be hard - remove your ‘clamps’ and use a big 2’ sanding block to smooth the blank. If your stringer sticks up, take it down with a sharp handplane. Sanding it will only remove foam from next to it, much faster than it will take down the stringer. If you must sand, put a couple layers of tape on the foam along both sides of the stringer.
After all that, drop your template on the blank & trace it. You can cut it out with whatever you used to cut the two half blanks for rocker. Try to keep the cut square to the rail. You can then even shape the rails with a surform (the big one with a plastic handle) and then sheetrock sanding screens if you don’t have any power tools or just don’t want to use them on the EPS. Then stiff sponges (dish sponges that have never been wet are fine) with 80 grit wrapped around to make concaves, vee, whatever. Then you’re ready to glass.
Mowie, don’t be too scared by electricity, there’s no reason, you can set up a really really cheap and not dangerous at all hotwire cutter, simply find a Transformer with double 12V output and 1A minimum (costs 6bucks) connecting the two outputs you get 24V and 1A, it’s just enough juice too warm up 80cm of stainless fishing wire, cann’t remember the diameter but i can check it if you ask, if you need more temperature simply short up a bit the wire, i’ll post a pic of the bow i did, but here on swaylocks there’re tons of that… than prepare your rocker template and cut:
It’s really easy and inexpensive, i tried the way you are thinking to, with the two template and a bandsaw… it’s really a waste of time, not precise at all and you end with lots and lots of eps dust.
I used the 2-rocker gides method on each 30cm wide blanks and the results were 50/50. I used a flexible handsaw that flexed too much in 30cm, so I get some 1cm deep valleys. Maybe it will be corrected using a stiff handsaw.
