On Mon, 29 Mar 2010 20:03:05 +0100, Justin C
wrote:

In article , Bruce wrote:

I just went through a fairly extensive blister repair and basically if
you use epoxy and fill gouges with chopped mat and epoxy the repair
will likely be stronger then the original hull, assuming that the hull
is polyester.

[snip]

Please excuse my ignorance. Are polyester and epoxy the same thing?
Also, you say 'assuming the hull is polyester', do you mean as opposed
to wood, steel or aluminium?

No, as opposed to other composites. "composite material, properly
known as fiber-reinforced polymer (FRP) or glass-reinforced plastic
(GRP and commonly called "fiberglass" in popular usage."

Polyester and epoxy are not the same. In general terms, epoxy is a
stronger material and polyester is a cheaper material. Retailers here
are selling epoxy resin at nearly double the price of polyester. Epoxy
bonds well to many things, including polyester while polyester bonds
less well to most things, including epoxy. However, as polyester bonds
to itself satisfactorily it is normally used for constructing
"fiberglass" items, such as boats, as strength is adequate and price
is low while epoxy is often used to repair "fiberglass" as it is
stronger and bonds well.

However, having said that there are may variables. Repairing a
fiberglass hull can frequently be done with polyester, and making a
plywood boat is often done with epoxy. Of course there are reasons to
select one, or the other, what is used to construct a F1 car tub, for
instance, is probably not the ideal material for a fishing boat.

OK, maybe I should know some of this stuff, especially as my boat is FG,
but are there different resins used to bond FG? If so, when carrying out
repairs should one stick to the same type or does it not matter once
it's all hardened?

In practical terms the strength of the materials probably isn't as
important as the ability to bond to whatever you are repairing.

There are a couple of dings on some corners (yes, I did both of them,
but I'm getting better), I say corners, but they're hard edges, not
curves, one at the bow, and one where the transom joints the port side.
Both of these parts have already been coated with what looks like paint
- it has brush-strokes, unlike the rest of the hull - and the strip
extends about an inch onto each surface. It's possible a previous owner
tidied up similar knocks the same way... anyway, I'd like to repair
those dings as they aren't attractive and are a constant reminder of
abuse I'd like to put behind me. I'll have a look at the West site, but
I want to be sure of the answers to my two questions before I tackle
these.

If these areas are gel-coat then you can't match the finish unless you
apply gel-cost over your repair, which can be done but isn't a
particularly simple task. In addition, no matter that the gel-coat
looks white if it is very old you will discover that new, white,
gel-coat doesn't match in color.

Interesting reading so far, and thank you for any help you can give with
my questions.


Justin.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)