Have any of the board builders tried making anything out of an EPS blank, sandwiching on PVC with glass and epoxy, then glassing over the top with PE resin? thinking of a surfboard rather than a windsurf board, mainly to keep the cost down a bit, and i hate sanding epoxy! This is mainly because i have eps blank, and PE resin going unused.

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jontyh said..
Have any of the board builders tried making anything out of an EPS blank, sandwiching on PVC with glass and epoxy, then glassing over the top with PE resin? thinking of a surfboard rather than a windsurf board, mainly to keep the cost down a bit, and i hate sanding epoxy! This is mainly because i have eps blank, and PE resin going unused.

I don't do it but you can do it. Old coil grid tech was ploy lam over an epoxy lam on eps. I do it on some surfboards, no problems.

Just be aware PE and epoxy don't mix well. I banned PE from my workshop, too much trouble with epoxy not going off because of PE contamination.

For me PE resin is polyester resin. You can use polyester resin on most epoxy and vice versa. Years ago voc epoxy could inhibit poly set but modern 2:1 vic free epoxy are chemicaly compatible. Epoxy should be fully cure and thoroughly scuff and "wash" before poly coat. For better results you should choose a polyester resin with same or near elongation to break, isophtalic and or acrylate modified poly for example. Most epoxy have an higher elongation to break and a lower stiffness modulus than poly so under stress epoxy skin flex and come back while poly break and chips off.

I wouldn't. You only need one pinhole and the fumes alone from PE will melt the core. I don't think epoxy is bad to sand at all when u use additive in the hot coat. plus it's sooooo much stronger why wouldn't you? I honestly dunno why PE exists anymore except in swimming pools and cheap boats.

Unless you have solid field experience, mixing resin systems will likely end in tears. I'd use the aging poly to make some solid blanks with any excess/offcuts fibre and whittle up some rad fins.

If you go this route, make sure you put enough pc stringers and bulkheads in the core so that it will work as a hollow board

Ok, sounds like a bad idea, and as i can get (fairly) cheap log blanks (PU) i might just do that, and use the EPS for insulation! Thanks all.

I know many pro builder that make eps core boards with epoxy lam and poly finish since mid 80's for the older one's. That was the standard way in europe for long time, thousands boards. Personaly i make around 250 boards like that, never have a problem. I find poly finish coat chips off when ding easier until i find right poly system and right process.

I build an EPS core board with sandwich foam bottom and cormat deck using epoxy.
Then did the outside lamination with vinyl ester resin with a white pigment.
Had carbon foot patches then rest was S glass and came out really good and very quick to finish with no painting.
A little heavier than standard but sailed well, it was built for jumping.
Didn't need to repair and thrashed it in Maui tradewinds sailing every day for over 2 months

At the time the factory was using two pot epoxy undercoat then fill pin holes, wet sand the two pot topcoat.
Later that season we changed to light grey undercoat, white rails and deck as influenced by guy building for F2 on Maui

I build an EPS core board with sandwich foam bottom and cormat deck using epoxy.
Then did the outside lamination with vinyl ester resin with a white pigment.
Had carbon foot patches then rest was S glass and came out really good and very quick to finish with no painting.
A little heavier than standard but sailed well, it was built for jumping.
Didn't need to repair and thrashed it in Maui tradewinds sailing every day for over 2 months

At the time the factory was using two pot epoxy undercoat then fill pin holes, wet sand the two pot topcoat.
Later that season we changed to light grey undercoat, white rails and deck as influenced by guy building for F2 on Maui

I see some guys that use bodycar polyester mastic as sanding coat on epoxy lam before paint.
Instead coremat you can use sphertex if you can find it. It's also a bulker but made with glass volumised with thermoplastic microsphere, same weight than coremat but bending stronger by itself. This is what rico-shape.com/ use.

I also do that as car products are formulated for proper filling and sanding with ease.

But that's over top final lam. I still think if you have only bagged PVC over EPS and thin glass layer, there will be a little hole somewhere so PU at that stage is fraught with danger - for no good reason.