Advice needed for graphite/epoxy bottom coating
Adam Gervais
resistant bottom coating? I'm planning to try this on a 16' driftboat I'm
in the process of finishing. I'm using West's resin. Their literature
recommends using max 10% graphite by weight, but I've read posts on a kayak
group recommending up to 25% graphite.
I'm also planning to add 5% colloidal silica and some white pigment. It
will be applied in several heavy coats with a roller and knocked down with a
foam brush. Recoat will be done while the previous coat's still gelled to
avoid any sanding. I also want to apply a good UV blocking varnish along
the sides where it will be exposed to direct sunlight, but suspect the
varnish may not adhere very well without some light sanding on the final
coat?
Someone Else
on the bottom just as you say, but did not put anything else on top of it.
The graphite epoxy will be gloss black (looks great) and is self-lubricating
over rocks and what not. My boat never got that 'snaggy feeling' when it
slid over rocks. It slid over just fine.
In answer to your percentage of graphite question, it may be possible that
you are reading the same guideline in both places, but stated differently.
I put 25% by volume into the epoxy (WEST Epoxy, WEST graphite), which I
think is close to the 10% by weight specification. Some guy at Gougeon
Brothers told me what to do. It works fine. It's pretty tough stuff no
matter what, so I really don't think the exact amount you put into the epoxy
is that critical, e.g. extra graphite won't hurt, say if you got all the
numbers mixed up and put 25% by weight into it instead. I think it'd be
fine either way. I think the Gougeon Brothers book on epoxy and boat
building actually suggests high ratios like this for low-speed bearing
surfaces like rudder pintles on sailboats for example.
Brian
"Adam Gervais" <ad...@rocketryonline.com> wrote in message
news:a3kgtc$s...@news.or.intel.com...
Klaus
graphite to keep the mixture runny enough for roller application and did not
measure the graphite.
You will get consecutive rougher coats if you do not use peel ply or let each
coat cure and sand it. It is a very messy job to sand and not easy either - its
hell on sand paper ( I used a torture board to sand).
I used this finish on the entire area below the water line, the centreboard,
the inside of the trunk, the rudder blade and blade casing of my boat as well
as on my 10' nesting dinghy.
I'm happy with the durability as applied over epoxy glassed plywood and glassed
lead ballast. It will scratch on rocks (or trailers) but its easily patched. No
problem on fine sand beach landings.
Why would you want to add white pigment to the jet black graphite??
You do need to sand ( 220 grit) the epoxy to apply varnish and then lots and
lots of coats of varnish. I ended up painting a lot of varnished epoxy trim,
the revarnishing took up too much time :-)
Klaus
cbetts
Applied with a squeegee in one thick layer (but then I've never managed to
apply "coats" of epoxy with a roller).
Works OK, but the bottom still gouges when hauling; needs re-finishing every
2-3 years - my ramp is hard gravel, and very pointy rocks - and I just drag
the boat behind the truck (I've heard of people who use a trailer ;-)
Topsides epoxy lasts about 3 years (9 months in the water, 3 months upside
down in the sun) without any paint or UV finish. But then, I don't get too
worked up over appearances.
--
Curtis
remove "-nospam" from address to reply
"Adam Gervais" <ad...@rocketryonline.com> wrote in message
news:a3kgtc$s...@news.or.intel.com...
jon riley
I am building a similar boat. I am using carbon fiber graphite (1 layer, not
sure what percentage this is) with spectra cord. Carbon fiber is expensive
but the same technology is in spactra cord. I am saying this so you can
spend less. Thousands of fine small lines in one cord. The more lines you
have in a cord the strength increases exponentially. Ten lines have hundreds
more strength than one line. Spectra cord is used by rock climbers on ledges
to hold higher strengths that exceed their climbing rope. You can always see
a climber with at least 5 metres of spectra cord. It is really strong with
resin.and makes a great frame support. You have to see it with resin to
understand what I am talking about.
I know this because the designer of carbon fiber graphite told me this. He
was one of 10 students at Cambridge University than were designing the
fuselage for the 747 in 1965. I thin Cambridge and a Aerospace company own
carbon fiber.
"Adam Gervais" <ad...@rocketryonline.com> wrote in message
news:a3kgtc$s...@news.or.intel.com...
Adam Gervais
coats, or possibly plan on doing lots of sanding on the final coat.
I'm adding the white pigment to help with the UV protection (in case I don't
feel like revarnishing as often as I should...) and to make the final color
a medium gray. The rest of the boat exterior will be burgandy, and gray just
seems to look better than black next to it.
"Klaus" <K.Suss...@curtin.edu.au> wrote in message
news:3C5E4434...@curtin.edu.au...
Brian
orbital sander and 220-grit between coats, and it came out super smooth and
glossy. No waviness or any other defects. I mixed it 25% by volume like
Gougeon Brothers recommended, rolled it on with a black foam roller, and
tipped it out with a black foam brush. All that work with a long board and
peel ply just isn't necessary.
My driftboat slid over rocks just fine and got beached constantly, and the
bottom was bullet proof. Only time I ever gouged the bottom was when I had
a "wide load" guy and his "wide load" wife in the front seat when the boat
was beached. They offered to scoot back to help get the boat in the water,
but I was polite and said "no problem". It was a tough lift to do,
especially when you're trying not to show it, and the boat was sitting right
on a jagged rock. The rock left a small gouge about an inch long and about
1/16" deep. Since there were 3 layers of 10-oz glass under the graphite
epoxy coatings and the gouge didn't even reach the first layer, I never
bothered to repair it.
Keep it easy on yourself and use the method I used above ... no torture
board, no sweat, works like a champ, Chump!
Brian
--
- Remove the 'NS' characters from my email address
"Adam Gervais" <ad...@rocketryonline.com> wrote in message
news:a3n6cu$j...@news.or.intel.com...
Adam Gervais
"Brian" <bria...@credenceNSvisionNS.com> wrote in message
news:mpG78.21587$ym3....@rwcrnsc51.ops.asp.att.net...
Brian
to smooth out some other filler (like wood flour) and to make something
thixotropic when it isn't otherwise (like microballoon powder.) If you mix
the graphite in at the 25% by volume ratio (or a little higher even), then
it rolls on pretty much like regular unthickened epoxy. Just roll it on
thin, rolling in alternate directions to make sure it's an even coat, then
tip it out with a foam brush. I always brush from a newly rolled patch back
into a "just rolled" patch. It works. It's simple. Don't know why you may
want silica in it. The black epoxy stays in place the same way clear epoxy
does!
Brian
--
- Remove the 'NS' characters from my email address
"Adam Gervais" <ad...@rocketryonline.com> wrote in message
news:a3nffr$p...@news.or.intel.com...
Joe Stafford
for strength use the silica smooth and then apply the carbon based mix. I
used for dagger board and rudder on trimaran. Running a-ground on shell and
sand bars seems to have little or no effect on it, will know better on that
after a couple of years. I'm in FL sun, But I'm pretty sure that after a
year or so in the sun you will see no deterioration in the graphite
covering. I would not even bother with the varnish etc. I don't think you
will be able to tone down the color of the graphite. You can get a sort of
gray by applying near dark when humid and allowing it to kick over night.
Would be wonderful discovery if you could find a way to get colors other
than black for final finish.
joe
"Brian" <bria...@credenceNSvisionNS.com> wrote in message
news:r_K78.23344$ym3....@rwcrnsc51.ops.asp.att.net...
Sheldon
tougher. I adds a gret deal to the abrasion resistance, If you doubt
that, try sanding it!
This worked well on my stripper canoe.
Brian
light that strikes the bottom of the boat is indirect. It'll get some
exposure due to reflection off the water and what not, but the graphite will
help a lot in preventing it from going deep into the epoxy. I'd plan on
rolling on a new coat every 2 or 3 years and call it good. Mine went 6
years without any degredation at all, and it got used a lot. But between
trips, it was stored in the garage. So, if yours is outside all the time, I
suspect that you should get plenty of time between coatings. If you're
worried about build up of epoxy, just sand it with 80-grit prior to the new
coat going on.
Note: I don't like the idea of putting any varnish or anything else onto the
graphited epoxy. I think that partially defeats the purpose of the graphite
in the epoxy, and you want to be able to easily repair the boat bottom at
any time. Sanding, wiping down, and putting on a fresh coat of black magic
takes no more than about 45 minutes if there is no varnish to strip off
first. Ugh! Who wants to strip a boat before re-coating!?
--
- Remove the 'NS' characters from my email address
"Joe Stafford" <jsta...@earthlink.net> wrote in message
news:MdS78.11161$3E5.9...@newsread2.prod.itd.earthlink.net...
Brian
enough silica in it to make a significant difference, and then also put the
25% by volume graphite into it, you'll probably end up with a mixture that
no longer rolls on and tips out very well ... it'll probably be too thick.
Why not roll on a silica slurry first, give it an 80-grit sanding to smooth
it just a little, then roll on the graphite-only layer on top of that? The
graphite will help the boat slide, and the silica is right behind it to help
guard against deeper grooving or gouging. In fact, fiberglassing the bottom
would get the most 'silica' on the boat and it's easy. My driftboat got 3
layers of 10-ounce fiberglass, clear fill coats of epoxy in between each
layer (and sanded too) prior to adding the graphite coatings. The bottom
treatment was about 1/8" thick and 80% fiberglass. The original finish had
2 coats of the black magic on it, then I added another layer later on (using
up extra graphite). That was one tough boat bottom!
--
- Remove the 'NS' characters from my email address
"Sheldon" <sdf...@netrover.com> wrote in message
news:ch306ukk3kjton9k1...@4ax.com...
Glenn Ashmore
permanent.
I think everyone needs to understand that graphite works to reduce
friction by wearing off. The structure is microscopic plates loosely
bonded to each other. When the surface is stressed by friction the top
plates sluff off preventing microscopic "snagging".
To get the best results, you need to produce a very smooth surface with
a lot of graphite particles exposed. The easiest way to do that is to
roll and tip the graphite loaded epoxy with no other fillers. You want
to add graphite until just before the mix gets to stiff to apply with a
roller. 25% by volume is a good starting point but in warmer weather it
can take a little more. Two or three coats applied at the gel stage
works great.
Overcoating it with anything prevents it from working. It does not need
UV protection because the graphite blocks light penetration. If you
store the boat upside down for a couple of seasons, the surface will
dull but that will not effect its anti-friction capability. If you
insist on showing a shiny bottom to the fish you can give it a quick
buffing to bring it back.
Adam Gervais wrote:
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Gary Zwissler
website. I used the 25% by volume ration for my boat's bottom. Originally
I was going to keep my boat on a trailer so I coated the bottom for UV
protection and lower friction when putting the boat on and off the trailer.
Later I decided to keep my boat in a slip. I was quite concerned about
painting over the epoxy/graphite mix - would the bottom paint come off?
Fortunately System Three and Interlux both recommended an 80 grit sanding
followed by bottom paint primer and the bottom paint. No problems. I
really like the look that a graphite bottom provides, so much so that when I
decided to put on bottom paint I chose black! Heres the link:
http://missrebecca.com/Jackhull.htm
I glassed the bottom with two layers of six ounce cloth first (four layers
on the chines and keel). The glassed surface was sanded fair, then I
applied three coats of epoxy over that. All sanding was done the day after
each coat of epoxy so I could get a chemical bond with the next coat. By
the time I got to the graphite/epoxy mix the hull was extremely fair. A
light sanding of the graphite epoxy mix with 320 grit after the third coat
was all that was needed. Of course I eventually hit it with 80 grit to prep
it for bottom paint, but before that it was smooth as a baby's behind and
really sweet.
Glenn Ashmore <gash...@mindspring.com> wrote in message
news:3C6116CC...@mindspring.com...