Epoxy over graphite

[Djeffrey]

Any issue with doing extra faring over graphite epoxy on the bottom if I see spots that aren’t smooth?

[Todd j]

Does the graphite impregnated epoxy cover whatever is underneath?   If it hides the previous coat I can’t see what difference it makes,  but I’m not sure.  I probably would have just done it if it were me.  Maybe suffer the consequences too

[Brian.Dixon]

I worried about doing that too, wondering if the graphite may affect bonding of the new coat etc.  But I did it on a skiff of mine and all I did was wash the hull real well with ammonia (takes off critters - protein) then laundry detergent (takes off oils and everything else) ... then hand sanded with 80-grit and coated with epoxy - a repair coat in this case.  No problem.  New epoxy bonds well on clean sanded graphite-impregnated epoxy.

Brian

[Djeffrey]

Thank you I was worried about how well it would stick.

[Brian.Dixon]

Thank you I was worried about how well it would stick.

I also found that barrier coat type primers stick just fine as well.  It kinda made me wonder why we put graphite in the epoxy if it had no surface effects... but whether it does or doesn't, it's still a great easy-to-repair bottom coat that blocks most UV from making it past the surface.  And it's free.  You had to put those last couple of coats of epoxy on the boat anyway, right?    Paint and primer costs moolah....

Brian

[json]

I thought that that was the whole point of graphite - that it keeps UV penetration to the very surface keeping the epoxy underneath from getting damaged. Is there some other benefit? Perhaps it's slippery so if you beach you will 'slide' off of rocks?

[First Draft]

I thought that that was the whole point of graphite - that it keeps UV penetration to the very surface keeping the epoxy underneath from getting damaged.

That's my understanding as well.

[Brian.Dixon]

I thought that that was the whole point of graphite - that it keeps UV penetration to the very surface keeping the epoxy underneath from getting damaged. Is there some other benefit? Perhaps it's slippery so if you beach you will 'slide' off of rocks?

There used to be a lot of talk about graphite making the epoxy self-lubricated ... easier beaching and trailering etc.  There were even some experiments where people tried to make sleeve bearings out of epoxy with graphite in it - the experiment failed.  The amount of graphite required to make epoxy 'lubricated' is enough to wreck the epoxy and it loses strength.  Regardless, there are some out there that still claim it's self-lubricating (one particular drift boat plans seller in Oregon I believe).  Sorta like copper powder added to epoxy ... same results, but failed at making the epoxy into an anti-fouling coating instead.  I think there's still a company out there that markets a copper epoxy additive for this, but as far as I know, it doesn't work.  Realistic expectations are that additives don't change the epoxy significantly, but black graphite does block UV well and repairs very easily.  I'd rather repair a black graphite bottom than have to get out the paint ... which means 'fix the epoxy first, THEN paint'.  Why not just stop at the 'fix the epoxy' step and git fishin'!?

Brian

[Todd j]

What seems to be the “time in the salt” Cutoff point  before your hull turns into a Reef?   I don’t like the idea of scraping or cleaning the bottom.  I have heard rumors of “hot” marinas and don’t think it a good idea to enter the water while moored for cleaning.  Graphite seems like it last longer and is way less maintenance. 
   I will be required to make this decision in the next few weeks. 

[Brian.Dixon]

What seems to be the “time in the salt” Cutoff point  before your hull turns into a Reef?   I don’t like the idea of scraping or cleaning the bottom.  I have heard rumors of “hot” marinas and don’t think it a good idea to enter the water while moored for cleaning.  Graphite seems like it last longer and is way less maintenance. 
   I will be required to make this decision in the next few weeks.

The time for growth to appear varies depending on the location and weather/water temperature etc.  In Alaska, it's a little slower ... in the Pacific Northwest, it's faster (weeks to a couple of months).  To clean, pull the boat from the water and use a pump sprayer to hose down the bottom with strong ammonia/water mix and let soak, then wash and hose off with your hose sprayer set to a 'jet' stream.  Repeat.  There should be very little growth left on the boat to manually scrub off.  The ammonia releases protein and plant / animal stuff from the hull.  Works great for cleaning bugs off your windshield too, BTW.  Some people soak with ammonia then pressure wash ... just be careful if you do and only pressure wash the black graphite epoxy coating - it's tougher.

Brian

[Todd j]

That does t sound so bad.  Thx

[Brian.Dixon]

That does t sound so bad.  Thx

Yeah .. barnacles and sea plants are pesky to get off your boat, and methods such as scraping or powerful pressure washing can damage the boat.  Ammonia was a great discovery once we found out about it.  Just pull the boat out when you can (at the dock) look down and see stuff starting to grow below the waterline.  Get it before it's been growing too long and it's a lot easier to clean off.  If docking is going to be your standard yearly procedure, then switch to an anti-fouling coating instead of graphite and it'll be even easier to maintain the boat.

Brian

[json]

I got to thinking about all of this, and was wondering if there is something similar to graphite that is white and can mix in resin and block uv that I can coat the whole topside in. Roll and tip looks like a royal pain, and it seems like the whole opaque to block uv damage should work right? Anyone know of any filler for doing this or have any knowledge about trying something like this?

[Brian.Dixon]

I got to thinking about all of this, and was wondering if there is something similar to graphite that is white and can mix in resin and block uv that I can coat the whole topside in. Roll and tip looks like a royal pain, and it seems like the whole opaque to block uv damage should work right? Anyone know of any filler for doing this or have any knowledge about trying something like this?

There is a product called 'White Graphite' (actually Hexagonal Boron Nitride) that probably works much the same as black graphite, but nobody's tried it that I know of.  If you wanted to go the 'no paint' route and have UV-blocking stuff in the epoxy coats, I'd probably lean towards Titanium Dioxide powder .... it's what they put in paint to block UV and to hide the color of the paint underneath .. it's the "high hide" component that some paints advertise on the label.  But PERSONALLY, I think roll & tip coats are easy to do and inescapable ... when you put the high-hide epoxy coats on, you'll have to roll and tip anyway.  If you want to reduce labor in painting the boat, invest in a high-flow (15 cu ft per minute) air compressor with at least a 20-gal tank and an HVLP paint sprayer system ... then spray the whole boat.  Buy a detail HVLP gun and you can paint the most amazingly small and complex items inside the boat's superstructure as well.  Money fixes everything

White Graphite (Hex Boron Nitride)

Titanium Dioxide Powder

Brian

[json]

Cool, I am going to order some of that titanium dioxide powder and play with it I think... Thanks Brian.