Epoxy/graphite mix

[arcadiainc]

Have a boat that I want to epoxy/graphite the bottom. I have heard of various mixes. Some by weight, others by volume. I would like a nice smooth finish. How should I go about this? Thanks in advance.:confused:

[Todd D]

Mixing the graphite is best done by weight. Graphite powder can be compact or fluffy. In other words, a given volume can vary a lot in weight. You will need a pretty good scale to mix it by weight though. Unless you are kixing pretty big batches, you need a scale that reads to =/- 0.1 gram.

Once you have the stuff well mixed, I would suggest rolling it on. I also suggest using the slow hardener or you will find the epoxy getting pretty sticky before you can finish rolling a batch out, which will give a rougher surface. Ideally, you want to coat the entire bottom in one application to avoid edges between batches. One way to slow your epoxy down further is to pour the batch into a metal roller pan that you set on ice. unfortunately, while that will slow the cure down, it will also increase the viscosity of the epoxy which will make it harder to roll out smoothly. It is a trade off. Finally, make sure you have several roller covers on hand so that you can change covers at the first hint that the cover is getting "sticky" from curing epoxy.

Despite all the caveats above, it is actually pretty easy to get a smooth surface, particularly if you do the application on a cool day.

[arcadiainc]

Todd-Thank you for the information.

[RodB]

The following two threads will tell you all you want to know about graphite/epoxy on a boat hull.

The mixture ratio is:

10 to 15% by weight or volume would be fine...remember, you need for the mixture to be opaque to protect the epoxy from UV...

proper ratio is 1 level teaspoon per each fluid ounce of epoxy.


http://www.woodenboat.com/forum/showthread.php?t=1958&highlight=graphite+epoxy

http://www.woodenboat.com/forum/showthread.php?t=77424&highlight=graphite+epoxy


http://i40.photobucket.com/albums/e239/Prestoboat/Txskiffgraphitebottom-72.jpg

http://pic15.picturetrail.com:80/VOL595/4284825/9007612/130381566.jpg


http://i40.photobucket.com/albums/e239/Prestoboat/Headon72.jpg

On application, graphite/epoxy did not change how I applied epoxy in general... just roll and tip, keeping a wet line like with paint... use medium hardener... plenty of time for all to settle to a nice smooth, uniform finish. I rolled and tipped the above hull with a 3.5 inch roller pad (cut the standard System III foam pad in half), covering approx a 10 X 10" area with each full roller of epoxy, then immediately tipping it with a foam brush. The epoxy is mixed and poured on a small platform 12" X 12" (called a platen) so that you can pick up the epoxy on a roller and as you use it all up, you can use a squeege to get every last drop off of the platen. Usually it is better to mix no more that 3 ounces so that it will not drip off of your platen.

This procedure is very efficient in not wasting epoxy and allows a straightforward method of getting a nice uniform smooth finish over a large area. I must admit on large horizontal areas, it is quicker to pour epoxy over an area in a zig/zag pattern and begin evening out the epoxy with a roller ( I do this alot of the time) , but you tend to use much more epoxy this way then the method described above. When applying the graphite/epoxy I was more interested in applying a uniform, very even, smooth coat... so I used the tried and true method of rolling and tipping. Once cured, the gloss was removed via a 1/2 sheet sander fitted with a piece of scotchbright followed by a wiped on coat of teak oil, which makes all look very uniform.

Note: as the graphite/epoxy oxidizes over time, you just lightly sand it...and reapply another coat.

Good luck.

RodB

[arcadiainc]

Thank you!