Re: [Paddlewise] stripping urethane from S&G kayak

Pamvetdr_at_aol.com wrote:
> Hi!
>    I would appreciate any advice on stripping urethane from a peeling stitch 
> and glue wooden kayak. The fiberglass has a few dings that need filled, but 
> the finish is the main concern, as I will be trying to sell it immediately.
>      One person suggested I remove all the loose finish, sand the edges and 
> the old finish to give the new coat good adhesion, and put on a new coat.

Pam, that is the only sure way to fix this.  It is not that bad a job.  Get 
some 80 grit sandpaper and put it on a sanding block (available same place 
as the sandpaper).  Use that to _carefully_ knock down all the gnarly 
spots, especially on edges.  Avoid heavy sanding with this grit.  You just 
want to knock off the really loose bits.  Don't worry if you cut into the 
glass a little here and there; the coating you apply later will take care 
of that.

Then switch to _wet_ sanding.  Yes.  WET SANDING.  Start with a quarter 
sheet of 100 or 120 grit "wet-or-dry" sandpaper, tri-folded, and hand-sand 
the entire hull, keeping the hull wet ahead of the sand paper with a mist 
from a garden hose, and rinsing behind the paper.  [Note:  ordinary 
sandpaper will disintegrate if used wet; get the stuff designed for wet 
sanding.  Second note:  experienced finishers will use a power-sander for 
this; don't; it is easy to over-sand with power.]

You want to have enough water on the surface so that the paper does not 
clog.  Periodically rinse the hull thoroughly and wipe dry, first with a 
sponge, and then with a soft towel.  This will expose any areas that need 
more sanding.  You are just shooting for a matte finish everywhere. 
Probably you will run through four quarter-sheets (e.g., one sheet, cut 
into quarters) before you are done.  When a sheet begins to lose its bite, 
get a new one.  Sandpaper is cheap; your time is not.

If you feel like spending the time, repeat the above using 220 grit.  This 
will go faster than the 100/120 grit treatment.  You are just reducing the 
roughness of the surface with the 220.  I've prep-sanded a lot of glassed 
surfaces, and if you are going to apply a polyurethane finish, there is not 
a lot of difference in the end result of you skip the 220.

All this sounds like a lot of work; it's not.  Probably you can knock it 
out in 3-4 hours and half a six-pack.

Now comes the important part:  get a quart of System Three Clear Satin 
Two-Part Water-Reduced Linear Polyurethane (they call it WR-LPU Topcoat 
nowadays) from these folks: http://www.systemthree.com/p_wr_lpu.asp This 
stuff is easy to apply if you pay attention to the instructions, thin it to 
the max, avoid arid conditions and direct sunlight (dries too fast).  It 
dries quickly between coats and will be tough as nails when you are done.

I apply it using a wide foam brush, tipping as I go with another foam brush 
(barely moist; they send instructions on this with the paint).  And, being 
a water-based finish, it has extremely low VOC, important if you plan to 
use your lungs for breathing 20 years from now.  The satin version is 
better than clear gloss for a rehab project, because it conceals defects 
and blemishes better than clear gloss.  A gloss finish will reveal all the 
things a buyer will not want to see ... but will be putting into the finish 
when he/she paddles the boat, anyway.

Two-part polyurethanes are like ordinary polyurethane finishes ... but on 
steroids.  The System Three variant, which I have used _a_lot_, is simple 
to use but expensive.  Hardware-store polyurethanes are massively inferior, 
but if all you want is to get the boat into someone else's hands and you 
are not worried about the longevity of the finish, get one of the 
_exterior_ Minwax products, in a water-based formulation.  Be sure to check 
the label for a statement that it has UV protection.  The S3 stuff does, in 
spades.  S3 does coatings for the serious yachting trade.  They know their 
stuff.  Nice people, too.

No affiliation with System Three, just a long-time satisfied customer.  The 
boat I built these last two years is covered with their 2-part LPU, some 
clear, most of it pigmented.

Remember, sanding is very Zen, and good for the complexion, also. 
Painting, not so much.

-- 
Dave Kruger
Astoria, OR
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