Eric's C21

[Eric1]

Ok, Test board set up at an angle to match (close) the hull. This is to evaluate leveling and runs.



Here are the rollers I will be testing. The cheap brush is to test tipping.



I appreciate all the advice on this but I have to see for myself.
See y'all in the morning.

[Jeff]

I look forward to your test!! Jeff

[Jaysen]

Eric, I used the 4" foam rollers. I had no issues with the foam, but they are too narrow. You wind up with overlap ridges if you apply to thick. Also, with the quick kick of hot epoxy, you go through them a lot faster than a wide roller. Ideally I'd use a 12" foam roller presoaked in 6oz cold slow, then use that to apply 12oz batches of hot medium/fast. I'd do the "pour it in the hull" trick with the pour lines running bow to transom at the keel. I'd then roll from keel to side spreading the graphite out.

I'll still suggest many, very thin coats. That will reduce the roller overlap thickness, increase overall thickness of the coating and I believe it will result in a smoother finish (no sanding till third coat which is when it will really start to cover).

I'm also anxious to see how your testing turns out.

[Eric1]

Eric, I used the 4" foam rollers. I had no issues with the foam, but they are too narrow. You wind up with overlap ridges if you apply to thick. Also, with the quick kick of hot epoxy, you go through them a lot faster than a wide roller. Ideally I'd use a 12" foam roller presoaked in 6oz cold slow, then use that to apply 12oz batches of hot medium/fast. I'd do the "pour it in the hull" trick with the pour lines running bow to transom at the keel. I'd then roll from keel to side spreading the graphite out.

I'll still suggest many, very thin coats. That will reduce the roller overlap thickness, increase overall thickness of the coating and I believe it will result in a smoother finish (no sanding till third coat which is when it will really start to cover).

I'm also anxious to see how your testing turns out.

I agree with the thin coat execution. I was thinking transom forward, keel to chine. Not sure about the hardener though. If temps stay like this I would go with medium. Once we get back to normal I would say slow.

[Jaysen]

I tried slow. It was just as fast to kick as fast once you heated it up to make it runny. But it took for ever to get from "unable to be spread' to "ready for next coat". I think the temp was in the mid 80s when I did it. The magic formula I finally hit was preloading the foam roller with slow to make it last longer and helping reduce the impact of the quick kick.

Just remember ... WET SAND ... you don't want to dry sand that stuff.

I bet you you can't "not sand" it. I dare you to try.

[MrPaul]

I bet you you can't "not sand" it. I dare you to try.

Eric might get the jitters if there's no opportunity to sand

Either way the boat is looking good and I'm sure the graphite will come out great. Looks like all the hard work and attention to detail is paying off nicely.

[Eric1]

I bet you you can't "not sand" it. I dare you to try.

Eric might get the jitters if there's no opportunity to sand

Either way the boat is looking good and I'm sure the graphite will come out great. Looks like all the hard work and attention to detail is paying off nicely.

You guys crack me up!

[topwater]

I am with Jaysen on this, it will be all you can do to walk away from the boat after you finish the graphite .
I bet you end up wet sanding it Remember put the sanding block down and slowly back away from the boat

[Eric1]

I just finished the roller test with the epoxy graphite.
In an effort to eliminate any lumps I prepped the graphite in a coffee mill first.
Then I filtered it through a sieve. I used an 80 mesh (180 micron/.007" inch) to insure there was no foreign crap in my graphite.
The kitchen strainer Cracker Larry use is not fine enough in my opinion. If you wish to use what I did they can be purchased here:

https://www.mcmaster.com/#sieves/=18vo9dk

Next I made a stainless steel stir mixer to incorporate the powder into the epoxy. I really don't intend to heat up the epoxy to get the graphite to blend.
This does induce a tiny amount of air but the design keeps that to a minimum.



I proceeded to mix two 6 ounce batches of Marine epoxy and slow hardener. Shop temp was 70 degrees.
I used the first batch to pre-load the rollers with out any graphite. Jaysen suggested it and I agree with the logic.
The second batch was hand stirred for one minute to blend the epoxy. then the graphite was added and hand mixed until it was wet.
Then I drill mixed it for another minute or so. It was emulsified perfectly. I poured straight from the cup from top to bottom and side to side.

Each surface was done one at a time.
I started with the 3/8" nap Purdy roller from Lowes. It loaded well and it covered quickly and evenly with minimum fiber release.

Next was the 4" 1/4" red Corona nap roller from Boat Builder Central. This roller is designed for applying epoxy over fiberglass cloth. It rolled well with firm pressure but it tended to apply the epoxy to thin for my liking. I believe it will be great for pushing epoxy into fiberglass cloth but the nap is to short to perform in this.

Next up was the 7" 3/8" nap Corona roller from BBC. It perform very similar to the 9" Purdy roller. The nap seems a bit thicker than the Purdy and thus it soaked up more epoxy. It seemed to leave a tiny bit more fiber in the epoxy but I would not hesitate to use these.

Last was the 4" epoxy foam roller from BBC. It did as expected. At first it tends not to roll and just pushes the epoxy until you have moved the epoxy around enough to thin it on the work surface. If you use these you must apply a very small amount of epoxy if you expect it to actually roll. Now, that said, it seemed to produce the best surface finish at the time of rolling. The key is to very lightly roll with it. Think of it as almost tipping with a roller.

Last, I tipped the lower half of all the test panel with a cheap brush. In my opinion it is a waste of time. Though it did induce light streaks they quickly leveled out. As always when tipping an incline you must tip horizontally. If you tip vertically those streaks will not lay down and will tend to produce runs. The only place I will tip is on the strakes and bottom of the spray rail. When I applied primer with the foam roller on those surfaces it induced air bubbles.

Here are the resulting panels. This was on bare wood. It sucked epoxy into the grain so keep that in mind when seeing the unevenness of the results.



Final thoughts, I will most likely go with Purdy rollers because of the quick coverage. Followed up with a foam roller. I think a finely notched
spreader would be ideal to spread this out and then roll with foam. I would have to make one and I'm not going to invest the time to tune the spreader for this. I hope this has helped any one who had the same questions I did.

[Jaysen]

Eric, warming the epoxy is not to mix it but to thin it for easier spreading. I experienced the same "no roll in the roller" until I heated the resin. Once hot it was very thin and a poured line did not hold firm (ran down slope) making it very easy to spread.

I know you've completed your test, but consider making a test batch with wanted resin and use the foam roller to apply. That was the magic solution for me.