Fibreglassing over expanding foam

[flying_wedge]

A reliable base to fibreglass over? Yes, no, maybe?
Would be to get the right shape, and would not be cut out at the end.

[neo]

It might work. There is a special 2part expanding foam that is usually used with fibreglass. i.e. surfboards .

[Infinite]

yup use the 2pack stuff.... we use it at work.

[KinLoud]

I'm sure RomanV used expanded foam to make his mould for his intake plenum.


Dave says in his project thread... near halfway down page 3
viewtopic.php?t=50492&start=40

"Arts and crafts week here at project meaner carina. Rolling Eyes

Been working on airbox for quads, decided to make out of fibreglass.

I got a sheet of fibreboard stuff, and drilled some holes in it so that it could bolt onto the face of the quads. Then built up some walls out of the same stuff, hot glued it all together so it had an open top.

Then got some expanding polyurethane foam stuff, and filled it up.

Which left me with what looked like a miniature coffin overfilled with mashed potatoe, pretty much:



Then pulled the walls off the sides, and then cut the foam to the shape that I wanted to fit the ram tubes, but also clear the clutch master cyl, brake master cyl and brake booster, and the bonnet line.

I mucked around with it for ages to get a shape that I was satisfied with, then I found that if I turned my brake booster upside down I had a hell of a lot more space, due to the shape of it. So started just about from scratch again, more cutting, sanding, filling up again, sanding, etc etc.

Then when I was finally happy with it, I covered the whole thing in brown packing tape, the stuff with the really shiny smooth surface.

Then just started laying down fibreglass/epoxy over the top.

Let it set, then picked out all of the foam from the inside, and all of the tape pulled off easy as.

Put some bog on the outside to smooth it out a bit, still got some work to finish it off, need to make the aluminium base for it once I've finalised exactly where it's gonna be. I need to find my bonnet hinges so I can test fit the bonnet clearance before finalising where it's gonna go, allowing for engine movement on mounts.



Will look a whole hell of a lot better when it's smoothed out and with some paint on it, gonna be colour to match the rocker cover, dark grey.

But is just about finished, thankfully. Surprised

The intake piping part was made near perfectly round by finding a plastic jar with the exact same outside diameter of what I wanted the inside diameter to be, cutting out the middle section, and jamming it into the side of the foam block. Razz"

Ken

[iOnic]

Where does one get that stuff?

[Infinite]

benchmark etc etc

[XS1V]

I have used straight expanding foam for fibre glassing and it works well

Brad

[deanis]

make sure you do a test piece first. some resins melt some types of foam.

[t0ms]

the only thing you'll need to watch is using polyester resins. they will eat some foams leaving you with a gooey sticky napalm mess that used to be you mould...

like the previous poster said just do a litle test piece first.

epoxy resins "shouldn't" eat the foam but are a litle more expensive and are a litle harder to use (exact mix ratio etc)

You can always use the expanding foam to create the mould then cover it in a half dozen coats of PVA glue (thinned with water). before you glass it paint it with a PVA release agent (available at fglass supply shops) and when the glass is cured it'll pop straight off meaning you can re use the mould

[RomanV]

I used gorilla filler, or similar... available at mitre 10.

Was suggested for me to do it that way by a friend who is a coach builder, who's done a lot of fibreglass work.

Brown shiny Plastic packing tape works quite well, to make the glass seperate from the foam. Cover the foam in that before laying down resin etc... pulls straight out very easily afterwards.

My airbox turned out alright in the end, but now knowing what I know, will remake it at some point so it looks a little better.