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Refinishing a boat bottom with graphite (Read 12994 times)
11/09/11 at 16:03:56

Los Humungos   Offline
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I remember reading awhile back a thread about an epoxy recipe formula using graphite and aluminum powder (or something like that) that is used as a super strong final coat on your hull.  Previously, I just have always used a resin (epoxy or polyester) without any additives to coat the bottom.  Recently, however, I started a project and thought I might like to try something new on the bottom of the canoe.

Can anyone give me advice on this formula or point me to a link to the thread?  Perhaps I am just remembering poorly too.

Any advice would be greatly appreciated.  Thanks in advance for your help.

Hut,
Wally
 

Sometimes when you are man, you wear stretchy pants...its for fun... -Nacho   
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Reply #1 - 11/09/11 at 16:18:55

yankeeclipper   Offline
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I have never heard of graphite powder as a strong final coat. I know some people mix it with epoxy and have painted it on the underside but the strength is in the epoxy not the graphite.
 
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Reply #2 - 11/09/11 at 16:48:13

jfawcett   Offline
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I believe the strength is in the epoxy, but the graphite powder adds some abrasion resistant qualities... helping the boat slide more easily over obstructions. I know Bryan Hopkins has done this to his boats a few times. Maybe he'll chime in.
 
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Reply #3 - 11/09/11 at 17:19:09

yankeeclipper   Offline
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Abrasion resistance would create drag. Most use of graphite is for its lubrication qualities, it has no strength as kevlar does. There was a thread sometime back about finishing hulls and getting more slide from them.
 
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Reply #4 - 11/09/11 at 19:01:22

Manitou Paddler   Offline
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Every one is right in a way and perhaps wrong too  Smiley

Graphite can do wonders to prevent abrasion...because it lubricates....basically if you hit a rock....the graphite in the epoxy acts like little ball bearings and boat will grease over rock with way less damage than with no graphite powder mixed into epoxy....I know this to be true.....not theory, it really works

Down side is black hull gets hot in sun

FYI epoxy by itself or with powder additives is actually pretty weak....must use cloth fiber (carbon, fiberglass, or Kevlar for strength.....we are talking a final coat and hull refinish here....which is not for strength per se, but smooth drag free surface

I will post specific instructions and a new finish coat/polish I discovered and really like when I am not thumbs on a smart phone Smiley.....can get a very smooth surface that resists even Missouri river mud line on hull

Bryan
 

river is as river does
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Reply #5 - 11/09/11 at 19:47:01

Joewildlife   Offline
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Bryan,
yes I look forward to hearing your thoughts on a new slick coat for a boat...

Wally what boat are you working on?  A green/white f/g Loon?

A certain green/white kevlar Loon finished 10th men's solo in the last 340 y'know.  With this weak *ss paddler.  I still got those rudder pedal parts if you need them.
Joe
 

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Cause I ain't too old to die
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Reply #6 - 11/09/11 at 21:13:32

Manitou Paddler   Offline
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Ok...here is my hull finish approach

Mask off hull to have a nice border from bottom of hull to sides of boat....at water line for instance

Light sand entire hull with 200-300 grit sandpaper

Fill in all gouges with thickened epoxy (I like to use fumed silca to thicken epoxy...gives glass like finish)....tip: for small gouges use clear packing tape on top of gouge after applying epoxy...often don't have to sand at all when epoxy sets...just pull off tape on filled in gouge

Sand again with 400 grit...then apply epoxy coat: use 1/8 volume graphite to epoxy mix....add just a drop or two of acetone to get fluid epoxy mix and apply hull with smooth roller....let set

Repeat epoxy/graphite coat...2-3 times more

After full cure (2-3 days)....wet sand by hand from 400 grit to 600, then 800' then 1000 grit

Will have now a cool dull grey chaulk board appearance

Wipe down hull with rubbing alcohol

Apply liquid glass auto polish....this is not really polish as it has to set and bind to hull (follow instructions, including let bake in sun for 2-3 hours before hand buffing).....this stuff is cool...but be warned....it makes putting stickers or paint on boat very hard because it is so slick.....but is is awesome....dirt or mud just falls off boat.....again it is not a polish really, as it binds to surface and creates a mirror smooth surface

Here is a link to product....auto zone stocks this product too...not cheap but worth it $25 can)

http://www.amazon.com/Liquid-Glass-Ultimate-Auto-Polish/dp/B0007ZFTJA

Hope that helps Smiley

Bryan
 

river is as river does
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Reply #7 - 11/09/11 at 22:26:23

yankeeclipper   Offline
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So if the auto polish forms a layer or skin over the hull why bother with
the graphite?
 
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Reply #8 - 11/10/11 at 08:53:07

Manitou Paddler   Offline
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The liquid glass is for a mud shedding coating

The graphite only comes into play when you hit something..and start to gouge or scratch the boat....then the graphite allows boat to skid past
Obstical with significantly reduced trama

Bryan
 

river is as river does
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Reply #9 - 11/10/11 at 09:28:41

yankeeclipper   Offline
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You have not made me a believer. Once you mix graphite with epoxy you are sliding over epoxy. It makes more sense to paint graphite with a mild bonding agent over the hull as a final coat also use more than 1/8 graphite in the mix. Mixing and matching different coats lends itself to an unstable finish. I think Ryan Slebos needs to weigh in on this. He works with auto finishes.
 
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Reply #10 - 11/10/11 at 10:08:21

awaller   Offline
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I've never build a boat, or even refinished a hull, but I know that Hardwood floor manufacturers use Aluminum Oxide powder in their finishes.  This not only drastically increases scratch resistance but also provides increased protection against UV fading and Oxidation.

I think we could assume it would have the same effect on a boat hull.

 
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Reply #11 - 11/10/11 at 11:03:01

Manitou Paddler   Offline
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Yanke dude.........I know it works.....I have real world experience with the benifits, which are dramatic if you hit a rock...as you tend to slide over it with the graphite powder in final coat or two of epoxy.  and lots of others have done this...google it.

do not recomend using more than 1/8 graphite powder to epoxy mix....as the epoxy gets too thick (hard to apply) and it weakens the expoxy coat some (can flake off in high flex areas).

the real set back, is the black hull...which can get very hot during transport (upside down) on top of car.

non of this is theory brother...it works..........try it on a chunk of plywood...and then scrape a rock accross it....epoxy with graphite powder and just plain epoxy coat....I promise you will see the effect.

as for paint or even gel coat...those are very easy to scratch or gouge.....have done both of those too......each has its place...depends on boat and its application.

it was just helpful advice on refinishing a beat hull bottom......I would not do this on a boat with just a few minor scuffs...but a boat that has been beat and needs gouges filled in and a surface refinsh...the epoxy/graphite is a viable option.


Bryan
 

river is as river does
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Reply #12 - 11/10/11 at 12:38:55

awaller   Offline
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Quote:
I've never build a boat, or even refinished a hull, but I know that Hardwood floor manufacturers use Aluminum Oxide powder in their finishes.  This not only drastically increases scratch resistance but also provides increased protection against UV fading and Oxidation.

I think we could assume it would have the same effect on a boat hull.


I should probably clarify - I wouldn't recommend using hardwood floor finish on a boat hull.  Huh Wink

But rather, blend Aluminum Oxide powder with the epoxy for the final coat of a build / hull repair just like Bryan has described doing with graphite (Or in addition to the Graphite).  

Same principal really.  

Charlie,

Not to put words in Bryan's mouth, but I think what he is saying is that with standard epoxy, when your boat hits a sharp obstruction and it penetrates into the resin slightly, friction prevents the obstruction from sliding down the hull.  As a result the epoxy is chipped away a millimeter at a time because the amount of force necessary to overcome the friction is more than the amount necessary to break the resin.  AKA a gouge.

By blending the epoxy with friction reducing additives such as Graphite and Aluminum Oxide you allow such obstructions to overcome the friction with less force, and do so before the epoxy reaches it's breaking point (even if it penetrates slightly).  Presto... no gouge.


And Bryan,

This is just speculation, but i'm thinking that aluminum oxide (being bright white) might resolve the "black hull" issue and in fact would add considerable UV protection and extend the life (and Looks) of the hull considerably.  

Might be worth some research, maybe even a "plywood vs. rock" comparison.  Smiley

-Aaron
 
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Reply #13 - 11/10/11 at 13:30:35

Los Humungos   Offline
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Ah, now I remember the thread, I think.  If I remember correctly, it was jimmythejet restoring a Newman Grasse River C1.  I will see if I can find it.

Thanks for the input everyone.  Great chatter.  Awesome thread.

Hut,
Wally

Edit:  Here is the grasse river thread:  http://rivermiles.com/forum/YaBB.pl?num=1289157691/7#7  lots of talk about hull refinishing, but this is not the one I was thinking of.  I think that there was a long time ago thread where the topic was mainly on graphite powder fnishes.
 

Sometimes when you are man, you wear stretchy pants...its for fun... -Nacho   
You do not get guns like these from riding a bike. -Matt Strieb
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Reply #14 - 11/17/11 at 21:13:27

slebos   Offline
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I have sprayed almost everything out there.. from gel coat to clear coat to epoxy ( yes boat epoxy)..  here is my two cents and FACTS are at the end..

everything has it's place and a lot of things are case by case..  100mph boats in the ocean use PPG DCC Concept urethane paint..  AWESOME stuff but expensive.  about $125 for a sprayable quart.  It's what I put on soggy bottom boys huki..


  gel coat is cheap and works well for most boats.. It has good scratch resistance for what you pay for.. 

  something to remember.. epoxy does not have any UV protection. Additive's kind of help.    There was a test done with  6 different epoxys and additives and the additives did a small amount of help..

as for redoing a boat..  remember this..  you are making a mechanical bond  when you recoat!!!   not a chemical bond.. a chemical bond is stronger..  so no matter what you put on a boat make sure you prep it correct...  That is THE most important part..  all your work on whatever you are doing is a waste if you don't prep it great...  nothing will stick to shiny paint/epoxy or whatever..  That is a good rule of thumb.. 

some say you can reopen the pores and get a chemical bond again, but that is another topic..

  remember that epoxy is plastic. So yes, adding carbon/graphite powder will help it slide over stuff..


               BELOW IS STRAIGHT OFF THE WEST SYSTEM WEB SITE..


Resin/Hardener mixture with an Additive      


420 Aluminum powder
Abrasion Resistance – Apply undercoats of epoxy modified for abrasion resistance or temporary UV resistance.
     

422 Barrier coat additives
Moisture Resistance – Apply undercoats of epoxy modified for maximum moisture protection.
     
423 Graphite powder
Low-Friction – Apply as a tough, low-friction coating, or as a bearing surface when thickened with fillers.
     

501 white pigment
Painting Base – Apply an opaque, colored epoxy undercoating as a base for painting.

503
Gray Pigment

Another thing to remember..   They say gel coat does not stick to epoxy resin.. So charlie is right.

  "Mixing and matching different coats lends itself to an unstable finish"


   BELOW IS FROM WIKIPEDIA AND OTHER SITES WILL SAY THE SAME..

Normal gelcoat formulated for use with polyester resins and vinylester resins does not adhere to epoxy surfaces, though epoxy adheres very well if applied to polyester resin surfaces. "Flocoat" that is normally used to coat the interior of polyester fibreglass yachts is also compatible with epoxies.

  And  Hopkins is right about the graphite..    It's great when we are all right..


 
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Reply #15 - 11/17/11 at 21:17:06

slebos   Offline
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oh yeah and wally is right..
 
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