Boat Forum / Building / June 2008

On Jun 24, 4:57 pm, rons...@localnet.com wrote:

I am not an expert in this area.

Don't forget to put a thin layer of epoxy over the last piece of
fiberglass before the epoxy in the fiberglass has completely cured.
This is to fill in all the texture of the fiberglass surface.  When
you need to apply the final fairing over the fiberglassed area, you
will need to sand the area to allow the fairing mixture to have a
better bonding with the cured epoxy.  If you hadn't filled in the
texture of the fiberglass surface, you would see a lot of tiny shiny
dots after you light sanded the area.  Those shiny areas need to be
roughed up in order to get a better bonding.  You would have to sand
heavily to remove those shiny dots.  I mention this because the
instruction from West System booklet (otherwise a great instruction)
only tells us how to do this but doesn't explain why we need to do
this.  Without understanding the "why", I easily forgot about doing
this in some areas that I have fiberglassed.  Now, I have told you
"why" you need to do this, please read the West System instruction
booklet to know exactly "how" to do this.

The other thing is that you may need to test the epoxy before using
it.  I used to have a bottle of epoxy resin that didn't cure days
after I had mixed it, and I had to throw it away (luckily I didn't use
it on my boat).  May be this had something to do with the fact that I
left the pump on the bottle instead of sealing the bottle with the
cap.  Regardless what caused this problem, the lessons are (1) do a
test batch before using the epoxy if we haven't used it for quite a
while; (2) cap the bottle at the end of the day.

Just to share some of my recent experience with you.  As of your
original question, I think you should put down the second layer of
fiberglass right after the first layer.  Then you can use less epoxy
and you don't need to sand between layers - save money and save time.

Jay Chan