I have been making one off patterns molds and parts regularly for the boat
and can tell you what works for me but I don't know what would be available
where you are. Scandinavia is a big place. I think Denmark and Sweden have
some good sources for composite materials.

Mold finish: I sand to about 120 and spray on a polyester based tooling
primer called Duratec Surface primer. It is a soft high build polyester
primer. Wet sand from 400 to 1200 then an automotive compound and finally a
fine polish like McGuire's. Two coats of cake type carnauba based
automotive wax as a base for the mold release.

Mold release: PVA is polyvinyl alcohol. A green liquid that dries to a
thin water soluble film. Spray a very light coat as a binder coat. After
about 10 minutes it will be dry enough to spray a wet coat.

Glassing: To do a proper job you need several different glass fabrics and
the Home Despot is definitely not toe place to get them. Price is way to
high and you will be lucky to find anything outer than 6 oz plain weave
cloth.

Some terminology: "Gel Coat" is a thick surfacing polyester with lots of
solids. It is the surface that you see when you look at most fiberglass
boats. "Cloth" is a plain weave material. It comes in various weights from
..5 oz/sq yard to 8 oz. and is used to reinforce the surface. "Roving" is a
very heavy yarn woven into a loose fabric. It is used for strength and
mass. "Mat" is a random oriented fiberglass felt like material used to fill
the voids in the coarser roving and prevent the weave pattern from printing
through the gel coat. "Sanding Aid" is a liquid wax additive that is mixed
with the last coat of polyester resin. Polyester does not cure hard in the
presence of air. The wax migrates to the surface and forms a shielding
layer to keep air away from the curing resin.

Start with a sprayed on polyester gel coat as soon as the first coat has
flashed off spray on another. You can roll it on but be careful not to
damage the PVA release. Repeat until you have about 30 mills of thickness
and let is cure for an hour or so. Then you can roll on some regular
polyester resin and lay a scrim of 2oz cloth followed by a layer of 6 oz
cloth and a layer of 8oz mat. You want the resin to fully wet out
everything. Next come several layers alternating roving and mat to build
the thickness you need. Cover the last layer of mat with some 6 oz cloth
and seal it with resin with the wax additive..

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Q" wrote in message
...
I need to make a couple of horns ( for audio use ) and have a couple of
questions as I never worked with this stuff before...

The local Home Depot clone ( in scandinavia ) sells the glass fibres,
polyester resin, hardener and gelcoat wich should be everything I need ?

The mold is made from a big chunk of MDF ( Medium Density Fibreboard )
that
I laminated from several smaller sheets, then cut the horn flare contour
in
it on a lathe..

To give you an idea of what I am trying to do I put a picture of an
existing
horn he http://www.naeslund.dk/peter/files/oprydning/hpt42.jpg The
mold
I made fits inside the horn.. Note that the actual horn I am trying to
make
is round, not rectangular like this..

Can anyone give me some idiot proof instructions on where to go from here,
before I waste 100$ worth of fibreglassing ingredients?

If not, heres a few questions:

How do I get the surface thats touching the mold as smooth as possible? (
The mold was turned on a lathe, so it is smooth, but I'd prefer the fancy
shiny surface :-)

How do I keep the fibreglass from sticking to the mold?

Any tips that may come in handy?

I know that this process involves nasty chemicals and nasty dust, so I
will
be doing this outside wearing some sort of dust filtering mask..

Thanks in advance

/peter