GT23

[fallguy1000]

Sand it all with 40 grit, no grinding, then neat coat within the window until the pocks are down; might need a few coats. If you mixed to much graphite; the bond strength of the epoxy would be reduced to some unknown.

Grinding it all off is extreme, but you'll need to decide based on how easily it comes off.

Again, no graphite experience, but I have a good knowledge about epoxy. What makes it so good is up to 2000 psi bond strength,

A simple, but good test is duct tape. Stick the tape down hard for an hour and see if your finish comes up. If it does; that means weak bonding.

So, sand it, test it. If the tape comes up clean, 2-3 or more neat coats. 2 ounces per yard, plus the roller takes some.

If the tape comes up dirty; you'll need to decide if you want to sand more or hope the neat coats hold the finish on.

[drbobopp@gmail.com]

I followed these instructions... and a coupla neat coats did help a lot....got some beautiful slick epoxy out of it, but still has a fine prickly feel.....My plan is to sand it, then put on a coat of ablative anti-fouling paint.

Now, please help me with this momentous question: Runners.

I was going to use fallguys method, and some 1" white oak. But I had a friend over, who once captained the "Florida Girl", a 40foot offshore fishing boat. He was to help me cut the runners, but began to question whether these are even needed.

Are runners necessary, or even advisable?

This boat will rarely be beached, and on the fine soft quartz sand of the northern Gulf Coast when it is. These oak runners are gonna add 30 lbs to the boat. My draft will go up (or down?) an inch. There will be slightly more drag, I assume. They are gonna be difficult to put on, and require holes through my hull!!... Jacques commented before he passed that the 'runners' you see on commercial boats are there to reinforce the fiberglass, not for performance or protection. But he does show runners on the GT-23. Others on the internet claim that runners are of little benefit.

To runner, or not to runner, that is the question. What say ye?

[Jaysen]

Run it without. If you find you need them, add them later.

You built it, you can modify it.

[TomW1]

I agree with Jaysen. The GT23 shows a keel so don't know how much runners will add in straight line steering.

Tom

[fallguy1000]

White oak weighs 47 pounds per cuft.

Water weighs 62 or so, so yeah white oak floats. And the runners are below DWL or design waterline, so they are adding displacement at less than their weight unless you glass them with chop strand or something silly,

So, if they weigh 30 pounds; they are about 30/47, call them 0.63 cubic feet. They will contribute flotation to the boat of about 0.63 • 15 pounds or 9.45 pounds of extra displacement to cover fastenings.

So, there is no weight or displacement penalty, but a gain of 9.45 pounds net of fastenings.

The reason I'd add them is only for bottom protection for beachings.

[jbo_c]

On my shanty, I glassed the bottom first, then added the runners. I epoxied my runners in place so there would be no fasteners. I did run a couple of temporary screws in to hold them to the hull while they cured. Then the holes were drilled and filled with epoxy. Then I glassed over the runners with simple woven cloth to give them a little more resistance to wear.

Overkill in several places, but it suited me. These runners also serve in a way as external stringers, so that’s part of it. I also liked the idea of glassing prior to installing as it should isolate the runners from the hull if they are compromised and rot sneaks in.

Not saying I did it right or wrong, just what I did.

Jbo

[drbobopp@gmail.com]

Thank you all so much. Very helpful.

I'm gonna forego the runners.

[drbobopp@gmail.com]

I have an epoxy question. But first, for anyone listening: Heed peewee's previous post of cracker larry's method. I read it, started out following it, then got sloppy. Mistake. The graphite seemed to mix just fine! Bad lumpy. More sanding and epoxy layers and troubles. Follow peewee's instructions, and save time, money, effort.

So, I have sanded down the lumpy graphite. Put on two layers of epoxy neat. Sanded that, and put on two more. It looks pretty flat and glassy, the low spots and irregularities mostly eliminated, but it still has innumerable tiny rough pimples. These can be easily seen and felt... 1-2 per sq inch or more. I believe them to be the remnants of tiny bubbles that form as the epoxy is laid and begins to set.

So my question:
Am I best off to just sand down the rough pimples, and proceed to bottom/ablative paint? (this is my preference).
Or, would it produce a slicker, better bottom if I sanded again and re-applied a layer of neat epoxy, and then went over it with a brush, before it cures, to break up the bubbles?
Would this produce a slicker, glassier bottom surface?

[pee wee]

The credit for the graphite/epoxy recipe goes to Cracker Larry, I was just pointing to it.

If a boat is going to spend lengthy stretches in the water you want bottom paint, if it lives on a trailer or a hoist then it's wasted money. Graphite/epoxy adds some toughness for abrasion resistance but does nothing to fight algae or barnacles.

[fallguy1000]

Could be two possible reasons for your troubles.

Obviously too damn much graphite.

But, if you continue to neatcoat; it is the best build coat bang for the buck.

You do it in layup window. So, like 3-4 layers without sanding. Then let it cure and touch it off with 80 grit ros.

Or, if the epoxy itself is making bubbles; that can be caused by outgassing of the substrate. Really only can deal with that the same way.

After a bunch of build coats, sand with 80 grit and lay on a final neat coat. If it is bubbling; use a hair dryer or heat gun carefully and see if the bubbles pop when warmed.

I'm guessing it is prickly because your surface is too rough is all. You may need to continue to do build coats. I think a mil is 0.025mm and 40 mil is 1mm. I'd say you are building about 3 mils per coat of epoxy, so it'd take like 6 coats to get to 18mils which is only 0.5mm to cover flaws on bottom from xs graphite.

I'd plan for 6-8 coats and a final single if it were me.