Thanks for the advice especially about leaving enough space for a layer
of fairing compounding.

Jay Chan

Ron Magen wrote:
Jay,
I was referring to the Don Casey {hardcover} book. I have no problems with
Gougeon Brothers literature, I just consider them more 'pamphlets'. {They
call them 'manuals'}This is more due to their brevity and physical size
{note the 'punching' so they can be 'filed' in a loose-leaf notebook}.

They do a LOT of work & research. In certain ways they are the pioneers in
the field. However, if you read more of their stuff you will note a lot of
redundancy in the illustrations & text. This is because a lot of 'problems'
have the same 'solution'.

Looking at my comp of 'F'glass Boat Repair . . .' I looks like your looking
at Section 4.2.1 which refers back to Section 3.3. They are talking about
the fiberglass SKIN . . . this is only about 1/8 in thick, at maximum.
{Casey implies about 1in or more} Therefore, if you bevel the edges as shown
there would only be about 1/2 inch, or so, difference between largest &
smallest piece. Follow that with the rest of the outlined technique -
peel-ply, vacuum bagging, {or heavily rolling each layer}, implied
'wet-on-wet' application, etc. - and it really doesn't matter which is put
down first.

What ever you do, allow space for a 'smooth coat' of fairing material, and a
1/32in thick coat of Gelcoat, or paint topcoat to blend in with the rest of
the deck.

Regards & Good Luck,
Ron Magen
Backyard Boatshop

wrote in message
ups.com...
Yes, I have read both West System books and Don Casey's book very
carefully. That's why I discover the difference between their two
approaches. Otherwise, I might not even notice the difference.
SNIP

I've tried it and it does some nice things, but I've also found several ways
to screw up.

It is mandatory that all air bubbles be gotten out before the epoxy sets up.

If the plastic is folded by the salesperson, it will remember and you'll
have creases (long narrow bubbles). Mutter and fuss until they find a
cardboard tube to roll it on and carry it carefully so it doesn't fold.
(Easier said than done.) Store the plastic carefully.

If there's any outgassing from the wood, it will create a bubble. Best to
first seal the wood with a thin coat of epoxy and sand out the bubbles, but
sometimes the outgassing pinhole acts as if you've tapped a geyser. Hot to
cold works best.

Then there's the frustration of trying to chase each bubble that you notice
to the edge of the plastic.

The epoxy seems to like the sheet plastic better than the fiberglass. If
you miss a bubble, you'll have a crater with the fiberglass at the bottom.
(Small bubbles don't seem to pull the fiberglass away from the wood.) If
you don't get back to it within the three day window for chemical bonding,
then you have to sand the inside of the crater (or drill it out) so the
patch will adhere.

I like it best for fillets. Cut the plastic sheet shorter than the length
of the corner. Roll the fillet with something spherical, or maybe the end
of your roller. You can chase the bubbles the short distance up the side of
the fillet easily. The result is a well faired join.

Between folding and cutting down to size I only get a limited number of
reuses for the plastic.

Roger

http://home.insightbb.com/~derbyrm

"Brian D" wrote in message
. ..

Some guy posted an article at http://www.duckworksmagazine.com about using
slightly-heavy clear plastic sheeting to fair a boat. If I recall, he put
the glass on the boat, then rolled the sheeting onto it, let it cure and
pulled the sheeting off. The pictures that I saw were marvelous ...glossy
smooth with no imperfections, no boundary marks or lines near edges of
overlapped cloth or at scarfs or anything. Never did give it a try myself
though, but it looked like it worked for him.

I did recently cut off the curved top of a transom to make it flat so I
could run a tuna handline behind the boat (tied to a handline cleat)
without the line rubbing on the transom. It's impossible to get a
perfectly straight cut and all I did to tune it up was to put a thin layer
of microballoon mix + epoxy on it, lay plastic wrap over it, then used a
piece of aluminum angle stock to press the top flat. Came out beautiful.
Ready to fair it in and paint....

Brian D



"DSK" wrote in message
...
Brian D wrote:
I don't think that I've ever gotten a drip of epoxy falling off a
pre-wetted chunk of fiberglass tape. Of course, by the time I started
using that method, I'd gained enough glassing experience to know how
much resin to put into it, but really ...the glass holds the epoxy quite
well. Try it sometime 'cuz I think you'll like it.


Another good way to pre-wet-out pieces of cloth is to use PVC sheet. It's
commonly sold in varying thickness as painter's dropcloth. The .5 mil
stuff is kinda flimsy but can be molded around 3-D shapes pretty well,
the 3 mil stuff is pretty strong and I use it for wetting out pre-cut
pieces on a flat bench or floor. It can be re-used almost infinitely too.
Cured epoxy will not stick to it, makes a great barrier film.

My method is to get a piece of the plastic sheeting that's at least twice
as big as the fiberglass cloth I'm laminating, lay the cloth into one
half of it, then add some mixed resin. Fold the other half of the sheet
over, then roller it so that the resin gets spread eavenly thru the cloth
and you don't get ick all over your hands or the roller. You can really
get a great resin-glass ratio and handle the piece without fear of runs
or drips.


And isn't the concern over a drip here and there a bit like being
concerned about getting wet when you go fishing? Be careful, but don't
sweat the occasional drips and runs. Buy a 3" wide carbide scraper
(with handle, and a knob above the business end) and the SurForm tool
with the short handle and 2" by 1-1/2" (approx) curved cheese-grater on
the end and you'll no longer sweat the little accidents ...they come off
easily after curing and it's easy to leave a smooooth finish behind.
Home Despot has these things for cheap and no epoxy user should be
without them. Forget sandpaper for fixing drips and runs ...bad idea.
Relax and enjoy the build.


Or get a plastic putty knife and scrape up the dripping / running resin,
take it over to your wet-out work area, and re-use it on the next piece
of cloth. Economical and saves clean-up time.

I've seen a heck of a lot of people working in fiberglass who seem to
bring an unshakeable woodworker's mentality to the process.... make it
thick, then cut it or sand it... then add some more and sand it off...
etc etc. Shucks, the beauty of molding composites is that you can make it
any shape you want, in less time, and make it *strong*. Get the material
to work for you, not against you.

Not that I'm an expert or anything, but I've made a lot of stuff out of
epoxy resin added to various other materials... including carbon fiber...
over the years.

Fresh Breezes- Doug King

In general,

In hand laid structures, edges and seams should be buried.
(the deeper the better)

The components (layers) are weakest in peal loads - at the edges.
So a smaller layer on top of a larger one might be expected to peal off?

All that takes is breaking an edge loose and letting it work for a while.



YMMV

Richard

(corrected to bottom posting to preserve teh thread)

If you go from the smallest piece first you have a chance of trapping
concentric rings or squares of bubbles in the laminate. Sam


wrote:

Can you explain a bit more on your observation of this problem? I
don't quite follow you.

Thanks.

Jay Chan


You need to try it to see for yourself.

Bubbles are bad.

The are air spaces inside the laminate.

Not good for dimensional stability - or strength

DSK and Brian gave me a weird idea...

Those white plastic shrink-on covers on the new boats..

I wonder if that stuff would be stiff enough to lay-up a glass hull?
Strong back and transom and shrink wrapped hull form?


Might be a cheap way to lay up a hull?

Richard

You mean like using a boat as a male form and the shrink wrap plastic as a
mold release? Boats have been used as male forms before, but I can't say
that I've seen anybody using plastic as a mold release. Generally, the
lay-up needs to be flexible or in more than one part however, else you may
not get it off the form. Mold release or not. Be sure to take pix!

Brian D


"cavelamb" wrote in message
k.net...
DSK and Brian gave me a weird idea...

Those white plastic shrink-on covers on the new boats..

I wonder if that stuff would be stiff enough to lay-up a glass hull?
Strong back and transom and shrink wrapped hull form?


Might be a cheap way to lay up a hull?

Richard

cavelamb wrote:
(corrected to bottom posting to preserve teh thread)

If you go from the smallest piece first you have a chance of trapping
concentric rings or squares of bubbles in the laminate. Sam


wrote:

Can you explain a bit more on your observation of this problem? I
don't quite follow you.

Thanks.

Jay Chan


You need to try it to see for yourself.

Bubbles are bad.

The are air spaces inside the laminate.

Not good for dimensional stability - or strength

But why putting the smallest piece first will increase the chance of
having air bubbles inside the laminate?

Jay Chan

For strength, there needs to be a high ratio of glass to epoxy, thus one
squeegies (sp?) out as much resin as possible. If the selved edge of the
narrow piece creates a step that wasn't sanded down, the wider layer of
glass will bridge the step and the space under the bridge will be filled
with air. That's why the plastic sheet overlay is so effective.

Roger

http://home.insightbb.com/~derbyrm

wrote in message
ups.com...
cavelamb wrote:
(corrected to bottom posting to preserve teh thread)

If you go from the smallest piece first you have a chance of trapping
concentric rings or squares of bubbles in the laminate. Sam


wrote:

Can you explain a bit more on your observation of this problem? I
don't quite follow you.

Thanks.

Jay Chan


You need to try it to see for yourself.

Bubbles are bad.

The are air spaces inside the laminate.

Not good for dimensional stability - or strength

But why putting the smallest piece first will increase the chance of
having air bubbles inside the laminate?

Jay Chan

Makes sense, but note that the gap can also be filled with thickened epoxy
mixes. If you are being religious about it, you'd use glass microfibers
plus silica (to make the mix nonsagging.) If you are going with the
wet-on-wet approach, then the outer layers of glass tend to press down those
selvage edges and what's not entirely pressed down will typically fill with
epoxy anyway ...and you can spot and fill bubbles (syringe) after curing as
well. But if allowing each layer of tape to cure prior to applying the
next, then the thing to do is to use a carbide scraper (plus light sanding)
to taper the selvage edge nicely AND fill the remaining 'gap' (as you call
it) with thickened epoxy. Most people will just use phenolic microballoon
or glass microsphere mixes for this, but like I said, if you were entirely
anal about it, you'd use glass minifibers and silica to fill the gap with
something that has a bit more tensile strength. But IMHO, using glass
minifibers and silica would be ENTIRELY unnecessary. If the structure is
weak enough to gain from such techniques, then you've already blown it and
should re-think your engineering anyway.

Brian D


"derbyrm" wrote in message
m...
For strength, there needs to be a high ratio of glass to epoxy, thus one
squeegies (sp?) out as much resin as possible. If the selved edge of the
narrow piece creates a step that wasn't sanded down, the wider layer of
glass will bridge the step and the space under the bridge will be filled
with air. That's why the plastic sheet overlay is so effective.

Roger

http://home.insightbb.com/~derbyrm

wrote in message
ups.com...
cavelamb wrote:
(corrected to bottom posting to preserve teh thread)

If you go from the smallest piece first you have a chance of trapping
concentric rings or squares of bubbles in the laminate. Sam


wrote:

Can you explain a bit more on your observation of this problem? I
don't quite follow you.

Thanks.

Jay Chan


You need to try it to see for yourself.

Bubbles are bad.

The are air spaces inside the laminate.

Not good for dimensional stability - or strength

But why putting the smallest piece first will increase the chance of
having air bubbles inside the laminate?

Jay Chan

I screwed up on my first boat with the wide over narrow, wet on wet. Now I
use the plastic overlay and avoid almost all the effort you describe while
still getting a high glass/epoxy ratio for taped joins. It doesn't really
matter which goes on first anymore.

Roger

http://home.insightbb.com/~derbyrm

"Brian D" wrote in message
. ..
Makes sense, but note that the gap can also be filled with thickened epoxy
mixes. If you are being religious about it, you'd use glass microfibers
plus silica (to make the mix nonsagging.) If you are going with the
wet-on-wet approach, then the outer layers of glass tend to press down
those selvage edges and what's not entirely pressed down will typically
fill with epoxy anyway ...and you can spot and fill bubbles (syringe)
after curing as well. But if allowing each layer of tape to cure prior to
applying the next, then the thing to do is to use a carbide scraper (plus
light sanding) to taper the selvage edge nicely AND fill the remaining
'gap' (as you call it) with thickened epoxy. Most people will just use
phenolic microballoon or glass microsphere mixes for this, but like I
said, if you were entirely anal about it, you'd use glass minifibers and
silica to fill the gap with something that has a bit more tensile
strength. But IMHO, using glass minifibers and silica would be ENTIRELY
unnecessary. If the structure is weak enough to gain from such
techniques, then you've already blown it and should re-think your
engineering anyway.

Brian D


"derbyrm" wrote in message
m...
For strength, there needs to be a high ratio of glass to epoxy, thus one
squeegies (sp?) out as much resin as possible. If the selved edge of the
narrow piece creates a step that wasn't sanded down, the wider layer of
glass will bridge the step and the space under the bridge will be filled
with air. That's why the plastic sheet overlay is so effective.

Roger

http://home.insightbb.com/~derbyrm

wrote in message
ups.com...
cavelamb wrote:
(corrected to bottom posting to preserve teh thread)

If you go from the smallest piece first you have a chance of trapping
concentric rings or squares of bubbles in the laminate. Sam


wrote:

Can you explain a bit more on your observation of this problem? I
don't quite follow you.

Thanks.

Jay Chan


You need to try it to see for yourself.

Bubbles are bad.

The are air spaces inside the laminate.

Not good for dimensional stability - or strength

But why putting the smallest piece first will increase the chance of
having air bubbles inside the laminate?

Jay Chan