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 Post subject: Graphite & Epoxy mix for the boat bottom
PostPosted: Thu Jun 16, 2005 9:38 am 
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Summary of an article posted by Chuck at www.southernpaddler.com and used with Chuck's permission. Slightly edited and added to.

When the boat is done and you want to protect the bottom there is a trick that I do for my boats and it does offer a lot of protection.

Use some epoxy and graphite powder to coat the bottom and a couple of inches up each side of the boat.

Tape off the sides where you want it and then mix up some epoxy and add the graphite powder then roll it out on the bottom.

Three coats, one coat per day over three days, will do the job very nicely. Make the coats light and they will build up. Much more so than just applying coats of epoxy.

To get a nice tapered edge to the graphite that transitions smoothly to the rest of your hull, move the tape about 1/8" further up the sides with each coat. That way the 3 layers won't build up a step or ridge.

The 1st coat you will still see some of the wood, the 2nd coat should cover it so very little or no wood shows thru then the 3rd coat is the final one. Let it cure two weeks and it will protect the bottom from scratches and a hidden benefit is it also makes the bottom of the boat slippery and easier to paddle thru weeds or over logs.

To mix this you need to use a container that this can be mixed in. It is VERY messy so wear gloves and don't plan on using that container again.

Mix some resin and hardener into the cup, now add about three or 4 spoons of the graphite powder and stir it really well so no lumps are there. Stir it again just to make sure it is mixed. General guideline if about 20-30% by volume.

At this stage I pour it in a paint tray and get the roller and roll it out on the boat. Let it dry overnight and then repeat the process.

Just make sure this is the LAST thing you do to the boat because nothing will stick to this mix.

If you decide to sand it to make it ultra-smooth, that's EXTREMELY messy process.

But the end result is a tough bottom that resists scratching.



Image

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Last edited by jem on Thu Feb 15, 2007 11:49 am, edited 1 time in total.

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PostPosted: Fri Jun 17, 2005 2:24 pm 
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I left out the name of the roller that I like to use.........

If you want to roll the mix out then make sure the roller you use is for epoxy.
The ones I get are 9 inches and I cut them in half (with a razor knife, box opener) to 4 1/2 inches so they fit the smaller attachment for the roller I use.
This gives me two rollers for each one I purchase.

The ones I like to use are the One Coat Paints by Linzer they are for Urethanes, Epoxies & Enamels with a 3/16 nap. A black label with a blue border and the roller is white. The bold print on the wrapper say's .... For ALL PAINTS, smooth surfaces, urethanes, epoxies & enamels.

Chuck.

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PostPosted: Thu Feb 16, 2006 10:24 am 
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If you were painting the hull and wanted to make the keel area more tolerable to abuse....could you paint the hull and them tape off your keel area, sand with some 150 then apply the graphite/epoxy coating per the directions above???

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 Post subject:
PostPosted: Thu Feb 16, 2006 10:36 am 
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I'd mask off the area you want the graphite to go and not paint it.

More of a sure bond.

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PostPosted: Sun Jan 28, 2007 9:15 am 
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Getting closer to doing this to my project....I was looking around and found this article, he added silica to harden the mixture...also read he was sanding between coats with steel wool :? He had a smooth looking finish with the graphite

http://tomangelakis.tripod.com/graphite_bottom.htm

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PostPosted: Sun Jan 28, 2007 9:51 am 
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I have done all but one of my boats with this mix , They all came out smooth and slick just by using the graphite mixed in the epoxy.

lightly sand the bottom and clean it from any dust before starting , then apply the mix and if you do it each day for three days there is no necessity to sand between coats , if more then 72 hours lapses between applications then lightly sand before proceeding.

The reason I said three days is because I roll on three (thin) coats of the mix to the bottom of the boat

Chuck.

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 Post subject:
PostPosted: Sun Jan 28, 2007 2:45 pm 
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Chalk,

Chuck told me about this, and I have it on all of my boats except the canoe. Will do it before spring.

I hadn't used silica, only 20% by volume of graphite. I move the masking tape out an 1/8" for coat# 2, then again for # 3. This staggers the edge and prevents a sharp edge. Interesting thought to vary the ratio of graphite as the layers extend outwards.

I paddle the Canadian Shield country too. Lots of broken granite with many sharp edges. Quartz, flint, gneiss, etc. The bottom slips through weeds and lilly pads much better now. Also, the epoxy is maybe two to three times harder. Some scratches that originate on the graphite, travel up onto the normal epoxy. They start as a mere scrub or light scratch, and turn into a gouge as soon as they enter the normal epoxy.

I'm not sure why Gilpatrick ever varnished below the waterline. Kind of a waste of time and varnish, I think.

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Last edited by Kayak Jack on Tue Jun 12, 2007 11:28 am, edited 1 time in total.

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 Post subject:
PostPosted: Sun Jan 28, 2007 5:50 pm 
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Quote:
I'm not sure why Gilpatrick ever varnished below the waterline. Kind of a waste of time and varnish, I think


As I understand it, he stores his boats outside, upside down.

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JEMWATERCRAFT Swampgirl; Wadefish;Touring Pirogue;South Wind; P5 ;
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 Post subject:
PostPosted: Sun Jan 28, 2007 7:14 pm 
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Not a good practice, that. Better to let a roof take the beating than a good boat. I never put to sea in a roof. They can be repaired on dry land. But if a boat comes apart when in use, that can get a might sticky.

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 Post subject:
PostPosted: Mon Jun 11, 2007 5:18 pm 
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Location: co.durham U.K
About how much graphite powder will I need for a 13 foot bottom?

Cant get any from my epoxy man,what sorta place sells it?can only find 250gram for a fiver on ebay,doesnt sound enough.

All I want is to have a real slick bottom :shock:

In the mean time Im just gonna have to scratch it :roll:


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