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trial and error...lots of error!

I tried the boat builders for info on glass over foam and you can't really get much from those guy's (they argue about EVERYTHING!) and feel no one with less than 30 years experience shouldn't be allowed to order resin.

However the surfboard guy's are great! (if you can get past the Kewl...dude!) they start with a foam blank and glass over top. Here is what I've learned/learning:

- The cheap foam blue/pink stuff from the hardware store sands well, the problem is almost EVERYTHING melts it! I cut my shapes and glue it with 5 min two part epoxy and hold it together with paneling nails while it dries (they have little ribs and won't pull out until your ready to remove them). After 10 minutes or so I remove the nails and use an exacto knife to slice a v grove in the foam where the epoxy has squeezed out, if you don't then it won't sand like the foam and will leave high spots. After you sand everything to shape, I use 60 grit paper to scuff the entire surface, this lets the resin bite into the foam.

- I use epoxy resin, and lay two layers of 7 to 9oz glass at a time. The epoxy is good and bad, the good is it doesn't eat blue foam, it doesn't stink up the house and it's slow to set. the bad is it's slow to set...like 24 to 48 hours depending on the temp and hardener you use.

- I paint the foam with a coat of resin then lay the first layer of glass and wet it out by rolling a foam trim roller brush (this is also putting down another coat of resin for the next layer)

- After the second layer is on I use a bondo spreader to squeegee the surface (it pops any bubbles and pulls the excess resin off), then I wrap the edges (Wax paper, thumb tacks, what ever it takes). I trim all the edges with an exacto blade after 24 hours (too much longer or too many layers and it will take a saw to cut it)

- I sand down any high spots or puddles that may have formed and lay a 3rd and 4th layer of 7 or 9oz and do the same. After 48 hours I level and again and fill any low spots with more resin using the bondo spreader to build it up a little. Grab a block sander and let her rip.

- At this point a stray away from others do in that I use a light filler to build in any fillets or fill problem areas. After everything is sanded, I layer two more layers OVER the filler and finish with a layer of 4oz cloth (this gives a smoother top layer and encapsulates the filler).

- I apply 4 layers of 9oz cloth on the other side of the foam, and lay strips in corners high stress area's etc... Normally this would not be enough glass, but because it's a foam core layup it's VERY rigid! and pretty light just like a surfboard!!

- Remember to subtract about an 1/8th inch from the edges of the foam because the top layer will be about an 1/8th thick and the bottom under an 1/8th.

Here is two or three other things to remember:
1. chop strand can not be used with epoxy resin.

2. unlike poly resin epoxy is also a glue so the entire layup doesn't need to be done in one session as long as you scuff and wipe down the previous surface with acetone first.

3. poly resin won't dry over epoxy resin but epoxy will dry over poly? however poly fillers don't care as long as the epoxy has cured.

After it's done you end up with a surface that you can feel the cloth patten, normally this is blocked out by the gel or tooling coat but since it's built up backward and gel coat won't bond well, I use slick sand, It's a high build primer and is ready for paint once it's block sanded.

PooK

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