Happy story - I scored some foam - sweeet. EPS which is new for me but really keen to try it.
Good size sheets too, some with a few chunks missing but nothing drastic that I cant fix. I have 6 in total and they measure at about 8’ x 3’10" x 3"
So I’ve read a lot about different construction methods and dug through the garage to find my old but never used car battery charger, pulled the ‘e’ string from my guitar and did a test cut - perfect… works like a dream. So I’ll build a frame and make a hotwire cutter.
What I’m wondering is if there is a way for me to add rocker to these flat sheets without building a rocker table and vac bag set up? If I can do this and cut my plan shape/rail bands with the hotwire then I could get about 12 boards out of the sheets I have! My other option is to make a stringer slightly larger than finished shape and use that as a template to cut a selection of rockered “planks” then glue them up similar to balsa construction.
I don’t really want to vac bag (space issue and I have to convert my old fridge compressor and buy vacbag materials - all too hard at the moment)
basicly Im looking for a fast and easy way out of this… Any thoughts/ideas?
When I was using Home Depot “blanks” I just pre-shaped the stringers to the rocker I wanted. Glue the EPS to that with epoxy and it holds the rocker fine for shaping & glassing.
You could also cut the rocker you want and just save the first offcut and glue it to the last - you’d have the under section + the tips and they’d glule together to make one last blank just fine.
you need a surfboard with removable fins that has a rocker you’re looking for
you need a roll of that saran wrap stretch tape you can get at any hardware or office store
you need the the rest of the wood components
if you plan on using a center stringer and no skins then draw and cut it out on 1/8" luan
rail stringer single sheet process:
cut out your outline fron the flat sheet
lay that on a flat stable surface and shape your bottom contour
cut out and insert HD foam or balsa ovals for your boxes
tape up and cut out your bottom skin out of balsa(light) or luan(heavy)
place your “portable rocker table” ie your board upside down on your racks
place your and position “bottom shaped” flat sheet on the botoom of your “portable rocker table”
using PU glue or epoxy resin with glass attach the wood over the bottom of the foam laying on the bottom of your “portable rocker table” board.
now use the saran wrap strapping tape to tightly compress the foam and wood flat against the bottom of your “portable rocker table” board. seal the lay end piece witha strip of strapping tape to hold it into place.
let dry 12+ hours
with a razor/scissors cut off the plastic wrap and you have a rockered blank with a shaped bottom and bottom skin already attached.
now all you have to do is attach the first band of perimeter rail 1/8" max and shape the deck down out of the 3" slab. You can also hot wire the profile before attaching the rail band and then dome/concave contour the deck.
when the deck’s done use the same process to attach the deck skin with out the need for a rocker table
now finish building out the rail stringer bands to 3/4" and finish shaping the rails before glassiing
if you want to skip the wood skins there are two ways to do it.’
use two thin sheets of foam and some epoxy and glass to attach them togther as described above with out the wood skin or wood rails but it will be stringer less…
if you use a center stringer cut your slab in half and use PU or Roo glue to attach the two half slabs to the stringer as you lay it on your “portable rocker table” board of as a stand alone. if you cut three center stringers you can use two on the out side of your non-outlined flat slab and just uses that to hold everythng in place with the saran wrap. This is a very messy process. compared to the rest…
finally there is another way used by Benny1, Rohan and Neira…
but just cut out your rocker/stringer profile template out of 3" slices from the flat panel and glue up all the 3" slices till you have the width you are looking for with or without the stringer. Each glue line will act as a mini stringer anyway. Then cut out your outline and shape it. Shaping this will be a challenge unless you use something like PU or even better Roo glue which is easy to cut through when it’s dry.
You need to know the density of the foam to decide what method will work best. If it’s the light stuff that Lowes and home depot sells it’s going to need a composite skin for strength.
If it’s heavier like 2 lb foam you can glass it without the composite skin. That would allow you to make a stinger with the rocker and top profile you want then just cut the blank in half, glue the stringer in using the bottom edge as your guide. Clean up the bottom to be the way you want it. If you want a slight concave leave a little bit of foam sicking out past the stringer when you glue it together. Cut the top foam down to meet the stringer with a hotwire or planer or surform, then contour the deck, and do the rails.
You can do a similar thing with perimeter rails. You’ll need to draw out the rails with the rocker shape and take into consideration the curve of the outline. I use 2 pieces of wood, usually balsa, and make both sides at one time to make sure they’re exactly the same. Glue those onto the foam while bending the foam to the rocker. You can use barbeque sticks to hold the rails on, just push them through the rails into the foam.
It helps to have the good flat surface of a rocker table to keep the foam from twisting. You might be able to do something with a couple of 2x4s. We use an existing board’s rocker as our guide/rocker table. Just make sure the foam has an even thickness, or the rocker will be different.
Do a search on “how the hackers do it”, and you’ll se some of the techniques we use.
Sorry to contradict, but the lower density foam works just fine in my expirence (limited i’ll grant). It might need a slightly heavier glass job, but then the core should be lighter eh? It just seems to me that the strength is in the glass no matter the density of foam, and where I’m from the light stuff is half the price…
Yeah other than that your way is pretty much my way…
Thanks everyone for your ideas, I think I’ll give Benny’s idea a try. A long time ago I bought a thick glass table off ebay for $25 so I can convert that to a rocker table pretty easily to assist in supporting the blank while it glues.
If I dont have the results I’d like from that then I’ll go with the glued plank method that rohan etc use. - I spoke to rohan yesterday and he said it was really easy and not to messy.
If Im shaping a stringer I may as well shape two and have a try at both methods anyway so that is probably where I will start.
If you change your mind and give Oneula’s method a shot, after wrapping the foam/surfboard/rocker jig up, you can run a hair dryer over the whole thing to shrink the saran wrap a bit… careful, too much heat will melt the plastic.