Sizing is a term used by Platt to mean applying varnish or something to the Kevlar itself, before laying on the Dacron. The idea is that if you DON T do it,Message 1 of 7 , Jan 26, 2008View Source
“Sizing” is a term used by Platt to mean applying varnish or something to the Kevlar itself, before laying on the Dacron. The idea is that if you DON’T do it, when you later seal the Dacron, the Kevlar may act as a wick that could soak the sealant (varnish) from the inside as you apply it to the Dacron on the outside, and cause little holes in the seal on the outside where it touches the Kevlar on the inside.
I didn’t bother with this step and just applied two coats of varnish to the stretched Dacron.
Spraying polyurethane (as opposed to bruching it) on the Kevlar seems like a waste of spray, since only a tiny amount would actually hit the Kevlar. But, if it works for you…
I built the ARROW14 (see in album: moszczak_arrow14). When it came to the waterproof coating on the dacron, I used a WATERBASED POLYURETHANE...as opposed toMessage 1 of 7 , Jan 26, 2008View SourceI built the ARROW14 (see in album: moszczak_arrow14).
When it came to the waterproof coating on the dacron, I used a
WATERBASED POLYURETHANE...as opposed to the commonly carried, oil-
polyurethanes in the market. I had to go to a paint speciality
to get this stuff, because the "big-box Hardware stores" didn't
carry "water-based polyurethane." Most of these idiots didn't know
what I was talking about! I went home and double-checked my
sources...believe me ...they make it!
The major reason I chose this, WATER-BASED is that, from information
other builders and other users, I found that the oil-based
polyurethane, tended to turn the dacron slightly yellow...with
several coatings...(I did a few test squares to prove it to myself)
I found that...the water-based stuff keeps the dacron pure
white... "like the new fallen snow on the convent roof." This only
makes a difference, if you care about this dacron color aspect of
appearance of your craft. I cared!
As I said it's difficult, but not impossible to find water based
product, especially if you
go to a "paint specialty store" ...where people know what they're
about, when it come to paints and coverings...furthermore, forget the
advice from idiots at the big national chain
hardware stores...you don't want them 'guessing' on some product to
cover YOUR water-craft that YOU SPENT HOURS TO BUILD, do you?
Specifically I used a product called: "PETRI DREAM, WATER DISPERSED
made in the USA (it's not cheap at $13 per quart...but Hey, it's my
canoe). I found that I used less than one quart to cover two
of my ARROW14, inside and out, applying the
initial coating...wait till dry...then apply the second coating.
The product itself is "very thin", watery, and milky white in color
in the container, about the
consistency and appearance of skim milk. They recommend not shaking
or stiring..to avoid air bubbles
To apply I used several
disposable SPONGE rollers (forget using the fabric roller
covers...they soak up too much material). Also, I used a small
sash paint brush, for minor touch-ups and application near the
heat&bond tape areas near the gunnels.
I also found one very good suggestion, from these pages...that
being...use an automotive drop-light (or some other good lamp) to
back-light the dacron, from inside your vessel, to view the
skin, when applying the polyurethane...it helps you to spot, missed
areas, drips, and "pinhole" leak areas.
Once finshed, and dry, this product dries invisibly...except for a
very light, and pleasing "sheen" on the dacron surface...but as I
said the craft surface remains pure white...not yellow, as with oil-
base stuff might appear.
The product I used can be sourced, on line. from,
located in Newark New Jersey( just in case you get it shipped).
Hope this helps...it's one persons experience!
Oh yes, I forgot the ARROW14 floats...appears water-tight! How will
it last?...time will tell.
--- In Airolite_Boats@yahoogroups.com, Ken Muldrew <kmuldrew@...>
>minutes, is a snap
> > Good question!.. I'm just about there myself and would
> > sure like to hear what others have done.
> I used shellac, applied with a brush. It dries in a couple of
> to clean up, and it does the trick.
> Ken Muldrew.
An excellent water based polyurethane for sizing or coating wood or dacron is System Three WR-LPU. It comes in satin, gloss and colors. This is a two partMessage 1 of 7 , Jan 28, 2008View SourceAn excellent water based polyurethane for sizing or coating wood or
dacron is System Three WR-LPU. It comes in satin, gloss and colors.
This is a two part water based inear polyurethane. I used the colored
version on my ply/epoxy catamaran and used the clear version for
coating the wood and sizing on my GA classic. It can be found at many
marine chandleries or ordered direct from System Three. Expensive but
very tough and easy to use.