Re: [bolger] plywood checking
There was an article in woodenboat in the last 1/2 decade by an
individual who had covered his bright work with light weight glass and
epoxy before varnishing. He said that it did not match the super high
gloss pro jobs, but after 3 months they were about the same. After 2
years he was waaaay ahead.
THE FOLLOWING IS OPINION FOLKS
It was his opinion, and mine, that the fiberglass with its strength in
tension, resisted the natural expansion and contraction of wood enough
so that the not so flexible varnish coating lasted on its UV
longevity, and did not go under because of cracking, and moisture
getting behind it. Most painted/varnished coatings on wood surfaces
fail because the paint can't follow the wood movement not because of
UV degradation, though UV will certainly accelerate the cracking
process, probably by making the paint/varnish even less flexible. I am
past opinion here and into speculation.
I have not had the opportunity to try this, but I intend to. I would
use 1, or 1 1/2 oz fiberglass.
This is one of the eternal dreams of boating, the varnished bright
work that looks great the next spring, so you can go straight to the
water without breaking out the sandpaper and brush.
HJ
individual who had covered his bright work with light weight glass and
epoxy before varnishing. He said that it did not match the super high
gloss pro jobs, but after 3 months they were about the same. After 2
years he was waaaay ahead.
THE FOLLOWING IS OPINION FOLKS
It was his opinion, and mine, that the fiberglass with its strength in
tension, resisted the natural expansion and contraction of wood enough
so that the not so flexible varnish coating lasted on its UV
longevity, and did not go under because of cracking, and moisture
getting behind it. Most painted/varnished coatings on wood surfaces
fail because the paint can't follow the wood movement not because of
UV degradation, though UV will certainly accelerate the cracking
process, probably by making the paint/varnish even less flexible. I am
past opinion here and into speculation.
I have not had the opportunity to try this, but I intend to. I would
use 1, or 1 1/2 oz fiberglass.
This is one of the eternal dreams of boating, the varnished bright
work that looks great the next spring, so you can go straight to the
water without breaking out the sandpaper and brush.
HJ
> 2) The use of glass, even relatively light glass in conjunction with
> resin seems to produce a very durable service. The bottom of my teal
> has 6oz cloth, polyester resin, and porch paint. After two years of
> being exposed to weather and sunlight continuously (other then when
> in use) it is in fine shape. The topsides fo the same boat (polyester
> resin and paint) are checked (again) and require annual painting.
>
>
FBBB --
The following observations are based on my two year old teal and one
year old scooner, both built with exterior grade 1/4 AC doug fir.
1) Checking seems to have something to do with exposure to sunlight.
For example: the underside of scooner decks are not sealed, painted
and are on the outside of a mild bend, yet they have not checked at
all. During winter storage, the south side of my teal (sealed with
polyester and painted) checked much more than the north side.
2) The use of glass, even relatively light glass in conjunction with
resin seems to produce a very durable service. The bottom of my teal
has 6oz cloth, polyester resin, and porch paint. After two years of
being exposed to weather and sunlight continuously (other then when
in use) it is in fine shape. The topsides fo the same boat (polyester
resin and paint) are checked (again) and require annual painting.
The deck of the scooner was painted with epoxy (raka) resin and
painted. It too has checked and needs repainting, while the topsides
(4oz, epoxy, paint) are in fine shape.
3) I built a hatch cover for the after deck of the scooner out of
3/4" luan. It is not sealed, glassed, or painted. Although it has
only been out for a couple of months, it has weathered far less than
I would expect from fir plywood.
4) I roughly estimate it takes me about 1/3 gallons of resin to fill,
laminate, and fair the "C" side of a 4'x8' sheet of fir. That's
about $12 in resin, $10 in glass, plus $15 for the plywood. This
still compares favorable with having marine ply delivered to Montauk.
I guess time will tell if the resulting AC+glass composite is as good
as exotic marine ply alone.
5) A coating of epoxy alone has a decidedly favorable favorable
effect when applied to "natural" wood. The scooner masts are
unfinished, and in the places where epoxy gooped around, the wood has
not weathered, while the bare wood has. (One year continuous
exposure.) I cannot say whether or not $10/gallon paint would have
produced the same effect.
Conclusion:
For me the cost and effort of applying glass and resin is more than
made up for in maintenance reduction. If is has added benefits in
strength or soundness, so much the better. In "The Sharpie Book"
Parker suggest that incorporating light cloth (glass or other) into a
paint finish can improve its durability. I am considering this
approach when I repaint the scooner deck. Or I may just sand the
paint of and give the decks a proper glass job. I am also thinking of
building a punt out of luan. If I do, I'll leave it paint only and
see how that holds up. All exposed surfaces of anything I build from
fir will get glassed.
YIBB,
David
CRUMBLING EMPIRE PRODUCTIONS
134 West 26th St. 12th Floor
New York, New York 10001
http://www.crumblingempire.com
(212) 247-0296
The following observations are based on my two year old teal and one
year old scooner, both built with exterior grade 1/4 AC doug fir.
1) Checking seems to have something to do with exposure to sunlight.
For example: the underside of scooner decks are not sealed, painted
and are on the outside of a mild bend, yet they have not checked at
all. During winter storage, the south side of my teal (sealed with
polyester and painted) checked much more than the north side.
2) The use of glass, even relatively light glass in conjunction with
resin seems to produce a very durable service. The bottom of my teal
has 6oz cloth, polyester resin, and porch paint. After two years of
being exposed to weather and sunlight continuously (other then when
in use) it is in fine shape. The topsides fo the same boat (polyester
resin and paint) are checked (again) and require annual painting.
The deck of the scooner was painted with epoxy (raka) resin and
painted. It too has checked and needs repainting, while the topsides
(4oz, epoxy, paint) are in fine shape.
3) I built a hatch cover for the after deck of the scooner out of
3/4" luan. It is not sealed, glassed, or painted. Although it has
only been out for a couple of months, it has weathered far less than
I would expect from fir plywood.
4) I roughly estimate it takes me about 1/3 gallons of resin to fill,
laminate, and fair the "C" side of a 4'x8' sheet of fir. That's
about $12 in resin, $10 in glass, plus $15 for the plywood. This
still compares favorable with having marine ply delivered to Montauk.
I guess time will tell if the resulting AC+glass composite is as good
as exotic marine ply alone.
5) A coating of epoxy alone has a decidedly favorable favorable
effect when applied to "natural" wood. The scooner masts are
unfinished, and in the places where epoxy gooped around, the wood has
not weathered, while the bare wood has. (One year continuous
exposure.) I cannot say whether or not $10/gallon paint would have
produced the same effect.
Conclusion:
For me the cost and effort of applying glass and resin is more than
made up for in maintenance reduction. If is has added benefits in
strength or soundness, so much the better. In "The Sharpie Book"
Parker suggest that incorporating light cloth (glass or other) into a
paint finish can improve its durability. I am considering this
approach when I repaint the scooner deck. Or I may just sand the
paint of and give the decks a proper glass job. I am also thinking of
building a punt out of luan. If I do, I'll leave it paint only and
see how that holds up. All exposed surfaces of anything I build from
fir will get glassed.
YIBB,
David
CRUMBLING EMPIRE PRODUCTIONS
134 West 26th St. 12th Floor
New York, New York 10001
http://www.crumblingempire.com
(212) 247-0296