What is the correct/best method to glue together two surfaces of made
from polyester resin with epoxy glue? This is a structural bond not a
cosmetic one.
Will roughing up the surfaces with 180-grid sandpaper and then
cleaning with acetone be ok or do I need to do more than this.

Clean with acetone first, sand with 80 grit or coarser, then wipe the dust
off. THicken the epoxy as needed with colloidal silica, milled glass or
other structural filler. Don't over-clamp.

bruce wrote:

What is the correct/best method to glue together two surfaces of made
from polyester resin with epoxy glue? This is a structural bond not a
cosmetic one.
Will roughing up the surfaces with 180-grid sandpaper and then
cleaning with acetone be ok or do I need to do more than this.

"bruce" writes:
What is the correct/best method to glue together two surfaces of made
from polyester resin with epoxy glue? This is a structural bond not a
cosmetic one.
Will roughing up the surfaces with 180-grid sandpaper and then
cleaning with acetone be ok or do I need to do more than this.

The above won't get it done IMHO.

Use a right angle sander with 24 grit to really roughen both surfaces, then
sweep clean.

(I use a brush and a blow gun)

Be aggressive. If you grind away an 1/8" of polyester, it's NBD since you
will be replacing it with epoxy anyway.

Mix epoxy with some Cab-O-Sil and Micro-balloons to achieve a peanut butter
consistency.

(You need both, especially the Micro-balloons)

Spread epoxy on both surfaces and position pieces leaving about 1/32"-1/16"
gap for the putty to fill.

Allow to cure for about 7-10 days before subjecting to a load.

HTH


--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures

I agree with Lew. I use a sander with either 16 or 24 grit paper and get
real aggressive with it. I would only add you should start by de-waxing the
surface first. It will clean the surface and reduce the clogging of your
sand paper. I use Dupont Y-3919S Prep-Sol solvent. It's available at
automotive paint supply houses. Pettit also makes a fiberglass de-waxer
that's sold in marine stores. Be sure to use a respirator approved for use
with paints.

Rusty O

What is the correct/best method to glue together two surfaces of made
from polyester resin with epoxy glue? This is a structural bond not a
cosmetic one.
Will roughing up the surfaces with 180-grid sandpaper and then
cleaning with acetone be ok or do I need to do more than this.



I have not done exactly what you are describing, but when sanding cured
polyester in preparation for bonding with epoxy -- say for doing an epoxy-glass
repair to a polyester boat -- I would probably sand the polyester with 50 or
100 grit (probably 100 if the surface was already smooth). If the surface had
any wax on it or anything else that might affect the bond, I would wash it
first, wipe down with acetone, and then sand it. I would probably change
sandpaper at least once if the surface had wax on it. I am not sure that
wiping down with acetone after sanding buys you much.
Alexander "Ali" Meller
http://www.sailing.org/int505/

This is all good feedback, thanks for the tips. Now to find the time
in the next month to get this part of the project done.

Regards
Bruce

On Wed, 21 Apr 2004 17:19:06 GMT, "Lew Hodgett"
wrote:


"bruce" writes:
What is the correct/best method to glue together two surfaces of made
from polyester resin with epoxy glue? This is a structural bond not a
cosmetic one.
Will roughing up the surfaces with 180-grid sandpaper and then
cleaning with acetone be ok or do I need to do more than this.

The above won't get it done IMHO.

Use a right angle sander with 24 grit to really roughen both surfaces, then
sweep clean.

(I use a brush and a blow gun)

Be aggressive. If you grind away an 1/8" of polyester, it's NBD since you
will be replacing it with epoxy anyway.

Mix epoxy with some Cab-O-Sil and Micro-balloons to achieve a peanut butter
consistency.

(You need both, especially the Micro-balloons)
Lew,
Why do you need both, espicially the Micro-ballons?
What about below the water line? Or in my case, replacing the sail
drive mount?

Spread epoxy on both surfaces and position pieces leaving about 1/32"-1/16"
gap for the putty to fill.

Allow to cure for about 7-10 days before subjecting to a load.

HTH

"Dan" writes:

Lew,
Why do you need both, espicially the Micro-ballons?

The micro-balloons provide the necessary filler and bonding characteristics
while the fumed silica improves the "hang time" and abrasion
characteristics.
(Sanding fumed silica filled epoxy is a real bear)

If I were to use only one, it would be microballoons.

What about below the water line? Or in my case, replacing the sail
drive mount?

No problem below waterline.

Replacing a sail drive mount will probably also require some added glass.

You have to remember filled epoxy is basically just fairing putty. Makes
great glue but it is not a structural member.

HTH




--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures