Thread: What to coat in epoxy?

Thanks PAR this is really helpful!

With the ribs they have temporary spreaders attached. Obvioulsy I need to epoxy under that as it comes off later so does that mean I should epoxy that bit before assembly?

I am just not sure what happens if I epoxy one bit now and another later. Does it effect the quality of the seal? Will it look bad?

Ideally, you want chemical bonds on everything, but this isn't practical for the average person, without careful planning.

It does no harm to coat, say the inside of a joint, then come back later and coat the rest of the part. In fact, it's often the only way to really handle things.

Staging and planning is part of the fundamental skills in boat building, which is problem solving. The first few times you use epoxy, you're going to get it all over everything, you're not going to be ready for the goo to hit the fan, so to speak and hopefully you'll manage to get the task done, before the pot smokes. After a few attempts, you'll realize that you need all your clamps and tools handy, not scattered on a work bench and that you might want to think about protecting these clamps or tools from the goo that's surely going to be on your hands when you grab it. Eventually, depending on how hard headed you are (ask your wife, she'll give you an honest acessment) you'll learn to line up your tools near the place you'll be using epoxy, have the cordless drill in a plastic sack to prevent you from having to chip off a half a gallon of dried goo, just so you can pull the trigger again, etc. This is fore thought and planning, a clear indication of problem solving.

In short, you'll have to glue things, so glue them. If the piece is precoated, then scuff up the area that will contact the joint and apply your goo. If the piece isn't precoated, then apply the goo to the joint and worry about finishing the rest of it later, when you have time., Besides, you'll probably have to clean up drips and ooze out, from this gluing session anyway right.

Haha, sounds like we are going to have some fun with this epoxy!

Good tip on covering the drill by the way. I wouldn't have even thought of getting epoxy on the drill.

So in terms of gluing two surfaces together what is the best way to spread the epoxy?
Should I just use a brush? If so is it a one use thing or can i wash out the brush and use it next time?

Or should I use the zip lock bag method as Mik has described elsewhere. If so how the hell do you get the epoxy into the ziplock bag?

So many questions, as you can see I am coming from a long way back here but I can tell already that you guys have saved me from a number of errors (though I know there are many left for me to make).

The good news is, there's no right way & there's no wrong way. Do what works for you.

Spreading epoxy in short joints - I just use the ice-cream stick I stirred it with.
Especially if it is a thickened goop. Bigger joints I up-scale to a slightly larger stick.
I only mix relatively small quantities - small yoghurt & margarine tubs.

If there's end-grain in the joint, likely to suck up much liquid epoxy from the goop, I'll
give it a wee drink of neat pox first by brush or by ice-cream stick, depending on area
to be wetted. Not flood it - just enough so it isn't 'thirsty' when the goop goes on.

Only mix what you can spread in 45mins or so in this weather.
Come summer, only mix what you can use in 10-15mins.

Long joints edge to edge, I like a syringe. Suck up neat epoxy out of the yoghurt tub,
or spoon goop into the back with the ice-cream stick. Can't push really, really stiff
pox out of a syringe, but ok up to the consistency of soft peanut paste. Syringe is
best for long joints in thin ply, and for filling nail & screw holes.

Thicker joints, or panel to stringer where more goop is needed, go for the zip-lok.
Never tried it myself, so won't offer advice on how-to.

hope this helps.
cheers

Originally Posted by hereselmo1

Haha, sounds like we are going to have some fun with this epoxy!

Good tip on covering the drill by the way. I wouldn't have even thought of getting epoxy on the drill.

if i were you think about getting epoxy every where, it has a habit of turning up where you least expect it so just be careful and use the right protective gear when using the stuff and always clean up after use, i used white vinegar for cleaning up.

Well, I usually don't go outside the Storer forum, but the debate over secondary vs. primary bonds was a big question for me.

From the above discussion it seems to me the best approach FOR ME (I emphasize the FOR ME) is to cut the panels/planks/bulkheads, precoat the plywood parts with epoxy (actually what I do is even better, I'll get to that), then after precoating is done, assemble the parts.

I will have already dryfit everything to make sure things don't need recutting or shaving. On my planking bench, I lay the parts out. If painted, I mix up a fairing compound (I usually use West 407) to a thick mayonaisse consistency. Using a drywaller's putty knife (a wide one!) and a "hock board" (6mm scrap ply cut up about 8"x8") like the drywallers use, I 'scrape' the thick compound into the surface and grain of the whole plank. The plank needs to be well cleaned prior to this step. The thickened epoxy fills the grain.
I'll do a short 100 grit power sanding, then hot coat two coats of thin epoxy resin onto the plank, roll and tipping it. I've done only one coat of epoxy and it is very glossy already. The second coat brings it home. Then I am done with precoating. I'll not bother with taping off where the bulkheads go, and just scuff up with 80 grit those places, which will be well marked in pencil during the dry fit. I'll be careful not to coat the end grain of the bulkheads and the rest of the faying surface until I am glueing in the bulkheads. So we'll have a really good 'secondary' bond to the plywood from the sounds of what PAR is saying.

Even better, would be to get the side planks and bulkheads glued up while the last coat of epoxy is still "green" which my epoxy says is true until 72 hours after coating at room temperature.

That is pretty good. In this case we'll still get the primary bond, but the epoxy is sandable even though it is still "open" for primary bonding. Like PAR says, this all takes good planning and that isn't always possible to execute in reality. In addition, I would add that it takes a really good knowledge of the product you are using. Mine is System Three; I know it well and can time things right with my schedule. I also like their use-specific approach to their epoxies. I don't use fillers much except for the "scrape filling" I mentioned and even then I often use the Quick Fair System Three makes. Great stuff.

Cheers,
Clint

Clint, when "filling" the grain, you should precoat the panels first with hot goo. The reason is thickened epoxy is less "wet" the neat epoxy and a raw plank can literally suck the epoxy out of the filler. Other wise you seem to have things well in hand.

The hot goo trick works very well on the first coat, but really isn't necessary on subsequent coats. Being hot, the viscosity is much lower, so it penetrates deeply, which is good. After you've sealed with a hot coat, you're not gaining anything with more hot coats, because the wood pores are already sealed.

There are two types of epoxy application folks, those that prefer hard applicators and the weirdo's like me that like the soft ones. The hard types use sticks, bits of scrap lumber, tongue depressors, etc. The softies use squeegees, plastic spreaders, etc. Of course, then there's the type that kind of go both ways (you've read about this group), they'll use things like putty knives and other not hard, but not soft devices to do the deed. What ever works is okay. Develop a set of procedures and stick to them, so you have repeatable results.

Originally Posted by hereselmo1

Should I just use a brush?

As soon as you use a brush, you're wasting epoxy in a BIG way Sadly, that's often the only tool or the best tool for the job at hand but be warned, they lay on far too much goop. Foam rollers are brilliant and have you measuring out the goop in miniscule quantities (well, not quite but they really are the Scotsman's choice ).

What you use depends on the job though. Playing cards make a cheap and effective squeegee. I've tried using the dog's tail and it's not to be recommended. Haunt the 2 dollar shops for cheap brushes and rollers. Don't muck about cleaning things, use and toss the thing out - trying to clean and reuse just has your psychiatrist reaching for the latest BMW brochure.

Epoxy is almost as bad as grease ... only almost because it's easier to get off but be warned, everything you wear (including your undies) WILL have epoxy on it after the job. Hell, I got epoxy on a shirt I'd worn the day before mixing the goop - the stuff slides through worm holes in space and time.

Always keep a bottle of the cheapest vinegar you can buy on hand - it does a ripper job of cleaning things.

Regarding the drill, I simply change gloves before handling it with the result that mine's in pretty good nick. However, my clamps are covered with both epoxy and scars from where I've chipped previous layers off.

Now all we need to do is start telling war stories about the pot of poxy that went feral and you'll be thoroughly terrified (seriously, you ain't a muggins boat builder until you've had a pot of poxy start smoking on you)

Richard

I agree, PAR, best practice should be to precoat the wood. In Boat school, they had us scrape filling (with out a precoat) on all plywood surface to be painted as well as scrape filling fiberglass to fill the weave. One thing I find that happens when I scrape is that the "smoodge" dries out (I think the ply and dust in the ply is doing that), so the way to go is precoat to solve that!

1) clean and precoat ply with thin epoxy
2) scrape fill with microballoons
3) let cure and power sand
4) one more coat of epoxy to seal everything

That could do it, the above would be like three coats of epoxy. I've been thinking of tinting the final coat of epoxy gray and using it as a primer, albeit a wicked hard-to-sand primer, but if every surface before it is smooth sanding the coats should not be too aweful. Anyway, it is all happening on the bench, that is the beauty of this approach.

Cheers,
Clint

If you get the surface really fair before you seal it, then tinting the epoxy is a good idea. I use heavily tinted epoxy in areas where repainting will be very difficult. This places would include inside cabinets, lockers, fore peaks, air chambers, etc. Use pigment designed for epoxy. Most require you mix it with the resin first, then bring the hardener to it. I know very few that can go without a good block sanding of the primer before paint so you may be just wasting time.

I wouldn't thin epoxy with anything else but heat (no solvents) on your first coat.

Yap, WEST tests showed thinned epoxy coats didn't provide any more protection if used in conjunction with full coats.

Just count the full coats and ignore the thinned ones.

Means that thinned coats are a waste of money.

I was never trained to thin and never considered either which is why System Three has worked great for us: the "Clear Coat" product mixes up like sugar water from Maple Trees around New England (not as yummy, but sugar water is what eventally gives maple syrup; as it is boiled down the viscosity changes). So what Sys 3 has done is produced different resins, Clear Coat, Laminating Resin, and General Purpose Resin then all their pre mixed products like quick fair, Gel Magic, T88. I am pretty well be re-trained in this sytem, but it took awhile to let go of West.

Why I like system three is the flexibility it offers: the resins (Laminating and Clear Coat) have no blush. Clear coat is fun to put on because it rolls and tips so smoothly. Both coatings can be bonded to within 72 hours at 77 degrees (who builds when it is that warm! In Maine, that means more time because it usually isn't that warm even in the morning in summer). What is cool, is that both seem to be sandable within a day at favorable temps and within two days at cooler temps. So, there will be a chemical bond for up to 72 hours and with clear coat it is probably longer in actuality because Clear Coat reaches 100% cure in 7 days! So, for prefinishing parts and still maintaining the primary bond, I am a full supporter of this brand of epoxy.

So it is up to the builder whether to prefinish the inside and outside of planks, etc. I too like doing a gray, heavy coating on insides of tanks, cabinets, etc. This is where I'd use the Laminating Resin, for instance, a little higher viscosity.

Clint

I have never applied epoxy with a roller.
Have been less than impressed with rollers as being anything other than a
quick way to cover large areas. Economy of product ... skeptical.
Besides which, on my kayaks, there isn't enough area to make the extra fiddling
with a roller worth-while.

Today I changed my mind. On all fronts.

Sanded & final pox-coated the coaming. Then thought, with an hour or so up
my sleeve, to coat the hull, one last time to fill the sworls & swirls that 80G
paper on the ROS left behind.

14x resin/7x hardener is about what the 2 deck chines take for full coverage.
So I figure trying the roller will probably cover the next chine down. Which it
did. With about 1/3 of my mixture still to go !! Lifted the boat onto narrow
supports & coated all of the next chine and more than half of the bottom
chine. There's enough left to finish the bottom, but I can't get at it to coat
it.

Tipping afterwards with a varnish brush left a finish not as smoothe as MIK's
pics, but a quantum leap better than brush alone.

By my calculations, the 3" roller has saved me 2 hrs painting, 6 hrs sanding
irregularities in film thickness, and made my pox go 2.5 times the distance.
With a corresponding weight saving in the boat.

Thanks blokes !!

As with a lot of these things....a good deal of thinking time will save you on "buggering up and redoing time".

So you need to sit down and build the boat in your mind and think how you will achieve the best result.......the good thing about this is you can rebuild the boat as many times as you like and it only cost you the time to thinks about it.

If you havn't played with epoxy much.... prehaps you should do something small as a skill builder such as a model or an icebox ( esky for us, chuuly bun for the K1W1's)... then you will know more about the processes....and you wont risk buggering up your prize project.

cheers