I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem to
remember that one should NOT wait 24 hours between each application, or one
would have to sand/grind the surface to wax??? Is that correct, and what is
the best time to lay the second and third coats?

The area is about 4 x 4 inside of the hull, so I can pretty well time the
applications as I please. All help appreciated. Thanks RichG

RG wrote:

I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem to
remember that one should NOT wait 24 hours between each application, or one
would have to sand/grind the surface to wax??? Is that correct, and what is
the best time to lay the second and third coats?

The area is about 4 x 4 inside of the hull, so I can pretty well time the
applications as I please. All help appreciated. Thanks RichG



You have options.

1) You can lay all thee at once, if you feel comfortable doing so. One
shot, all done. You may be less likely to end up with excess resin in
the laminate this way.

2) You can allow the epoxy to reach a "green" cure between layers. This
makes subsequent layers easier to position.

3) You can allow 24 hours and still be able to lay consecutive layers
without sanding (assuming that you use a non-blushing epoxy), as the
epoxy will take longer than that for a full cure and will still
chemically bond between layers. While it varies from one product to
another and with the temperature during curing, some will still
chemically bond within 72 hours.

4) You can wait for a full cure, then sand between coats. This produces
a mechanical bond only. 1, 2 or 3 three if preferable.

--
Regards

Brian

RG asks:

I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem
to
remember that one should NOT wait 24 hours between each application, or
one
would have to sand/grind the surface to wax??? Is that correct, and what
is
the best time to lay the second and third coats?

The area is about 4 x 4 inside of the hull, so I can pretty well time the
applications as I please. All help appreciated. Thanks RichG

"Brian Nystrom" writes:

You have options.

1) You can lay all thee at once, if you feel comfortable doing so. One
shot, all done. You may be less likely to end up with excess resin in
the laminate this way.

2) You can allow the epoxy to reach a "green" cure between layers. This
makes subsequent layers easier to position.

3) You can allow 24 hours and still be able to lay consecutive layers
without sanding (assuming that you use a non-blushing epoxy), as the
epoxy will take longer than that for a full cure and will still
chemically bond between layers. While it varies from one product to
another and with the temperature during curing, some will still
chemically bond within 72 hours.

4) You can wait for a full cure, then sand between coats. This produces
a mechanical bond only. 1, 2 or 3 three if preferable.

All of the above get the job done.

Personally, I purposefully wait at least 48 hours between layers for the
following reasons:

1) Can feather the edges of the glass to have a smooth transition between
layers.

2) Level out any uneven surfaces and any resin blobs that maybe you missed
during lamination.

I don't get hung up about getting a chemical bond. The mechanical bond is
quite good. Epoxy is very forgiving stuff.

I use a lot of 16 grit discs and also be sure to wear a mask.

The laminate is still not fully cured at this stage and the dust can be very
nasty.

HTH

BTW, if all you want to do is get rid of the blush, a ScotchBrite pad and
some water will do the trick.

Good luck.


--
Lew

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

Lew Hodgett wrote:

RG asks:



I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem


to


remember that one should NOT wait 24 hours between each application, or


one


would have to sand/grind the surface to wax??? Is that correct, and what


is


the best time to lay the second and third coats?

The area is about 4 x 4 inside of the hull, so I can pretty well time the
applications as I please. All help appreciated. Thanks RichG



"Brian Nystrom" writes:



You have options.

1) You can lay all thee at once, if you feel comfortable doing so. One
shot, all done. You may be less likely to end up with excess resin in
the laminate this way.

2) You can allow the epoxy to reach a "green" cure between layers. This
makes subsequent layers easier to position.

3) You can allow 24 hours and still be able to lay consecutive layers
without sanding (assuming that you use a non-blushing epoxy), as the
epoxy will take longer than that for a full cure and will still
chemically bond between layers. While it varies from one product to
another and with the temperature during curing, some will still
chemically bond within 72 hours.

4) You can wait for a full cure, then sand between coats. This produces
a mechanical bond only. 1, 2 or 3 three if preferable.



All of the above get the job done.

Personally, I purposefully wait at least 48 hours between layers for the
following reasons:

1) Can feather the edges of the glass to have a smooth transition between
layers.

2) Level out any uneven surfaces and any resin blobs that maybe you missed
during lamination.


You can do both of these things with a scraper when the epoxy is still
too soft to sand. It's less work and it doesn't create dust.

--
Regards

Brian

"RG" wrote...
I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem to
remember that one should NOT wait 24 hours between each application, or one
would have to sand/grind the surface to wax??? Is that correct, and what is
the best time to lay the second and third coats?

Read the literature from the epoxy mfgr to be sure; there will be differences
among them.

My experience is with System 3. Using their regular laminating epoxy, their
Epoxy Book says you can wait up to 72 hours without sanding, but I wouldn't wait
that long, especially in a warm environment. I generally waited 12-24 hours
(overnight or the same time next day), based on the convenience to my schedule.
That allowed the epoxy to cure enough that I could easily feather or trim the
edges with a Surform or razor knife as needed, and the surface was not so tacky
as to make positioning of the next layer of cloth more difficult.

"Brian Nystrom" writes:


You can do both of these things with a scraper when the epoxy is still
too soft to sand. It's less work and it doesn't create dust.

For small jobs it certainly works; however, lay 15-20 yards of glass and you
have a whole different set of conditions unless your arms are say 15 ft
longG.


--
Lew

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

Lew Hodgett wrote:

"Brian Nystrom" writes:




You can do both of these things with a scraper when the epoxy is still
too soft to sand. It's less work and it doesn't create dust.



For small jobs it certainly works; however, lay 15-20 yards of glass and you
have a whole different set of conditions unless your arms are say 15 ft
longG.



Absolutely, but the poster was asking about glassing a 4'x4' area.

--
Regards

Brian

"RG" wrote in message ...
I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem to
remember that one should NOT wait 24 hours between each application, or one
would have to sand/grind the surface to wax??? Is that correct, and what is
the best time to lay the second and third coats?

The area is about 4 x 4 inside of the hull, so I can pretty well time the
applications as I please. All help appreciated. Thanks RichG

If the area is workable and you can do it, I would just lay all three
layers at once. Remember, it is easier to draw epoxy up from under
cloth than to drive it down into cloth. Wet out the area good, lay
down cloth, then start wetting out, this makes things much easier. An
average layer of cloth for me goes like this. 80% of the epoxy I will
use for the layer is on the part before I lay in the cloth. For larger
areas I also have a big table with plastic. I wet out the cloth on the
table too, then lay it into the goo. Even then, I paint the table with
a layer of goo, then lay the cloth into it. You can use tacks to hold
it in place temporarily if it is at a bad angle when you put it on the
part. Once you lay the first layer down, wet the next on the table,
lay it on and squegee the excess out and do the third layer. You will
usually end up with a lighter composite, and a lot less work.
Scotty from SmallBoats.com