Doing the Black Bottom

[Kayak Jack]

(There's a dance from the Roarin' 20's called the Black Bottom.)

I am a confirmed believer in using graphite enriched epoxy on the outside bottom of boats. But, lately, I've begun to wonder - does it really need to be three coats thick?

If one coat presents a graphite enriched surface to the water (and to underwater obstacles), why do I need more? If it didn't fully cover in one coat, and it never seems to, wouldn't only two coats do as well as three for slipperiness?

What do you guys think?

 

[jdupre']

Good point. Also, could you just include a graphite coat as one of your fill coats instead of completely sealing up the bottom and then applying the graphite coat? Might cut out a bit o' weight and a bit o' epoxy.

 

[hairymick]

Builder's choice Jack.

I prefer AT LEAST 3 coats cause my boats need all the help they can get.

 

[Kayak Jack]

I agree, Mick. When I drag my boats over sharp edges of broken granite, gneiss, feldspar, quartz, flint, etc. I want a lot of protection. But, I'm beginning to think that two layers may well suffice overall, with extra down the keel line.

Just starting to question, and ponder, and listen. Thanks for your input, Mick & Joey.

 

[JEM]

Just starting to question, and ponder, and listen.

oh oh... next Jack will build a flat bottom hull with laun door skins.

 

[oldsparkey]

I use three thin coats , by rolling them on.
The 1st one you can see some of the wood threw it. The 2nd coat most of the wood has dissapeared and the 3rd coat , it is all black.

Chuck.

 

[Kayak Jack]

I followed the same protocol, Chuck. And am wondering if the third coat is really necessary? I will likely sand and add another coat in a year or two anyway.

 

[oldsparkey]

Two good coats might do the trick , I just like the three lighter ones and , who knows , two might be just as good.

I'll give it a shot on the canoe I'm building and see if two is plenty.

I did try it on a piece of wood with two coats on it , that was a long time ago ( when I was doing the symposiums about building wood boats and outdoor activities , camping , paddling here in Florida ) to show how it helps to protect the bottom over just plain epoxy , a key scraped across it ( same force as in keying a vehicle) could not damage it. Even had some of the audience try it to prove I was not taking it easy with it.

Grant you , that key was nothing like paddling up on a rock , cement or limestone or even Oysters in a loaded canoe.

Chuck.
PS. No I have never keyed a vehicle , wanted to but restrained myself.

 

[Kayak Jack]

I'm thinking that the third coat or second coat is a 'Degree of protection"? Needs vary with circumstances?

I follow your key demo. Rocks scratch the graphited eopoxy, and dig into the regular stuff.

 

[stickbow]

I've only used graphite on one of the 'poxy boats I built, so have a low sample rate. It significantly improved the scrape factor on rocks and oyster shells, but in the places I only put two coats (above the second chine) it was more prone to damage than below the chine, where there were three.

Question though:

What's the best place (meaning cheapest I reckon) to get graphite powder? The reason I only used two coats on the upper part is 'cause I ran out, and I am cheap.

 

[aub77]

http://www.duckworksbbs.com/supplies/ad ... /index.htm has it for $7 per pound. Raka.com has it for about 8.95 per pound. Don't know about shipping costs but I have bought things from both of them and both were decent on shipping costs.

 

[Wannabe]

Re:

Good point. Also, could you just include a graphite coat as one of your fill coats instead of completely sealing up the bottom and then applying the graphite coat? Might cut out a bit o' weight and a bit o' epoxy.

How much weight and expoxy cost would you save by not putting on the third coat? And you guys that paddle on gravel and rocks. How much is the extra protection the third coat
gives your boat worth?
Bob