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Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 11:53 am
by VT_Jeff
I'm at the point where I need to put something on my bottom. I'm planning on using an epoxy/graphite coating(or 3) without paint on top of it. Am wondering if there is any need/benefit to putting primer on before the epoxy. I know that people use high-build primer to handle the final fairing but I'm not too concerned about that, it's as fair as I care for it to be. Just not sure if there are other reasons I need to/should add primer before the epoxy.

As always, any/all opinions welcome.

Jeff

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 12:02 pm
by Reid
VT_Jeff

IMHO there is no need prime before the epoxy/graphite coating. Primer is meant as a final coat/sealer before paint.

Make sure, if you haven't already done so, to read Cracker Larry's graphite application method.

Good Luck,
Reid

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 12:49 pm
by Capt UB
My mix as follows: 8 oz of resin and 4 oz. slow hardener, then 1/2 cup of graphite power.

What I used;

BBC's Graphite, MarinEpoxy with slow hardener

What I did;

Shifted graphite a few times.
Mixed epoxy and hardener.
Added graphite slowly as I mixed.
Rolled on slowly.
Wet on wet, 1/2 to 1 hour between coats.
Total 3 coats, maybe 4?
Did not sand at all.

I guess we shall see if this holds up. So far, I dropped the boat on it's transom (no skig), hard!
Nothing cracked or chipped off! Also, it's very slippery!

Update, I hit a big log on the river at full speed with two of us in the FS14 (SandPiper). We came out of the water, I very slowly turned around and went back to the ramp to pull the boat out.... Checked bottom and inside, no problems!!!

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Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 1:11 pm
by terrulian
Agree with the above. I put primer on but not sure why.
It isn't bulletproof and unlike the good Captain, I've scraped it but I drag my boat across rocks and gravel sometimes. Easy to patch, though.

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 2:12 pm
by VT_Jeff
Reid wrote:
Thu Feb 13, 2020 12:02 pm
IMHO there is no need prime before the epoxy/graphite coating. Primer is meant as a final coat/sealer before paint.

Make sure, if you haven't already done so, to read Cracker Larry's graphite application method.
Perfect, will do, thanks!

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 2:14 pm
by VT_Jeff
Capt UB wrote:
Thu Feb 13, 2020 12:49 pm
Rolled on slowly.
Appreciate the input, Capt. I suspect I will avoid the roller, apply with squeegee and then tip/smooth with a foam brush, 3 coats wet-on-wet. I have never had any luck with a roller and epoxy, have had decent success with a squeegee. Let know if you think that's insane.

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 2:37 pm
by VT_Jeff
terrulian wrote:
Thu Feb 13, 2020 1:11 pm
Agree with the above. I put primer on but not sure why.
More support for skipping the primer, awesome, appreciate it!

terrulian wrote:
Thu Feb 13, 2020 1:11 pm
Easy to patch, though.
Interesting side topic: Do you carry an emergency patch kit? I'd be interested to know how people do field repairs on these cored-composite boats, and what they carry in the boat for emergency "get back to port" repairs.

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 3:11 pm
by BrianC
VT_Jeff wrote:
Thu Feb 13, 2020 2:37 pm
Interesting side topic: Do you carry an emergency patch kit? I'd be interested to know how people do field repairs on these cored-composite boats, and what they carry in the boat for emergency "get back to port" repairs.
When sea kayaking, we always carry some Denso tape - basically a strong fiber tape with a thick bitumen layer that sticks to the hull, even when wet. It comes in 6" wide rolls and has a plastic film covering the sticky side. Just cut off a piece, peal the covering, and slap over the hole.

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 3:21 pm
by Jaysen
I think Tony was talking about "patch" in the context of top to mid layer. Not a hole in the hull. To fix the graphite finish, just sand a bit, mix a bit and apply a bit. Simple.

When it comes to holing the hull, the better option is positive floatation for boats of "size". Even if you know you holed it, how do you get under it to apply the patch? Capt UB is a highly experienced captain and you'll notice he just slowed and got to shore. With positive floatation you know you can get to shore even if you are a little wet. for us small boat guys... we still need to get to shore but we are able to roll it over and slap some tape on it.

Re: Bottom epoxy/graphite

Posted: Thu Feb 13, 2020 3:58 pm
by VT_Jeff
Jaysen wrote:
Thu Feb 13, 2020 3:21 pm
Even if you know you holed it, how do you get under it to apply the patch?
That's a good point: not much of the hull below the waterline is accessible from inside the boat on some/many of these designs where flotation is sealed in.