Tricks that minimize epoxy runs/drips.

[rkcross]

Hopefully, this is not a dumb inquiry. Being a newbe in the use of epoxy I need some advise. I am in the process of epoxying the hull of a rowboat but, spending alot of time smoothing out the uneven bottom. What tricks are there to minimize this kind of a problem?

Here is additional information as what I am trying to accomplish:

I have applied two coats of epoxy to the hull, sanding the runs between coats. It maybe I am simply trying to apply too thick a coat at one time,
however, it seems like sanding removes what I just put on( I am not sanding to the point of going as far as the wood there still epoxy covered wood). My goal in this project is three coats of epoxy then paint the hull. The requirement for final coat of epoxy may not be as critical as that for a bright finish. My thinking is that there must be a better technique to apply epoxy with minimal sanding. I tried using foam and cheap bristle bushes for application.

[mcdenny]

Assuming you are smoothing out ridges in the epoxy, not the wood:

Use a thinner (lower viscosity) epoxy - plus lays flat, minus requires more coats for a given total film thickness

Warm epoxy - plus becomes thin epoxy - see above for + and - and heat will cause it to cure faster, often before you want it to.

Get the epoxy out of the pot and onto the boat quickly, then work on spreading it evenly. The epoxy will start curing quickly in the pot, but somewhat slower as a thin film on the boat where it stays cooler. Your bumpy epoxy job may come from trying to use epoxy that has begun to thicken.

A newbie eror is to try to use all the epoxy he mixed even as it starts to thicken as the cure progresses. After all, you don't want to throw away that expensive glop. Bad idea, it becomes too thick to spread evenly and will create ridges and bumps. You will throw away that expoxy anyway - as laboriously won sanding dust. As soon as you note the epoxy getting harder to spread STOP. Throw the rest out and start over with a fresh smaller batch.

Epoxy seems like real thick paint that you could lay on in a heavy layer but it does not form a skin like paint to hold its surface in place. It stays a thick liquid that can respond to the pull of mother Earth until the cure progresses to harden it up. Thats why it can look good when you brush it on but 20 minutes later you can find runs. It needs to be spread surprisingly thin to stay flat on a vertical surface.

The major sellers of epoxy publish (mostly for free) application manuals. Check their web sites. Do what they say.

[Thorne]

More info please - what exactly is the issue?

Check out "peelply" - using plastic / fabric over epoxy to lessen the need for fairing = http://www.duckworksmagazine.com/05/projects/freestyle/index.htm

[Cuyahoga Chuck]

Dear Mr. Newbie,
Ya gotta' get more specific. We ain't mind readers.
Are you talking about doing filleting or applying epoxy in some other way? Remember there is Stitch & Glue, Ply-on-Frame and Glued Lap. Differnt techniques but all can be epoxy glued.
If you loosen up and tell us the design there might be someone else who is familiar with it.
Oh, and I forgot to say welcome. Welcome! I only get to contribute when we talk about bare-bones building styles.

[the_gr8t_waldo]

if your working with a flat surface, then the best is to orient the work to be as flat as possible. if you can't do that( or can't move it at all) i've found some luck in useing peel-ply( i think you can get by with thin dacron from a fabric store-same thingl) pressing into matrix while it's setting up. once hardened, the peel-ply is just riped off, to reviel a good texture for following layers. if it's a finish coat, i'd try plastic wrap over the works. best to experiment a bit before commiting to the main event.

[Ian McColgin]

Just focusing on the cured drips for a moment:

Most sanding, especially by machine, knocks more than the peaks off, it deepens the valleys as well. This is a problem.

First step is to level carefully with a well turned and sharp cabinet scraper. See a good woodworking site for how to handle this as it's not at all like a paint scraper. The nice thing about this is that you attack the drip along, not surrounding surfaces.

Next, you might hand sand with a hard block - again to attack the peaks and leave the valleys unscraped. There was a WB article about making a hard disc. I have been doing a variation on that for years - nice for stuff other than epoxy - and if you use slow speed or a random orbital unit and learn how not to dip an edge, this is the superbest thing since high carbon steel.

I like to go with the hard disc to the point where after tacking it feels pretty smooth but you can see clear unscratched places. Then you've definatly not taken too much off. Finish with a really light fine sanding with a conventional pad to scratch the valleys, tack, and spread the next coat. If you're done with epoxy and getting to paint, finish sand with hard pad if you want perfectly flat.

G'luck

[DuncanvdH]

I had the same problem. My solution was putting the epoxy on with a foam roller, and tipping it out with a large cheap brush to remove the bubbles.
The rolling it on definitely made the coat thinner and very even.

[Eddiebou]

You can cut drips down with a flat metal cabinet scraper before the epoxy fully cures. This is really the way to go. It's 10 times faster than sanding and does a better job, + no dust.

[JimD]

Apply with a squeegee, several very thin coats, a few hours apart, in a warm workshop. No drips, no sanding between coats.

[RodB]

The following application tips from another thread may help.. This is a method offering maximum control when applying epoxy, rolling and tipping with a foam brush and allows you to apply the least epoxy to minimize drips, runs, etc. You cannot mess around with mixed epoxy very long if your goal is to get a nice, flat, smooth finish. Get it on as fresh mixed as possible and let it level itself. IF the application area is not horozontal, the coat needs to be thin to avoid runs. This is difficult sometimes. Note: no matter how smooth you sand the wood, the first coat ends up with bumps and wood strands making the epoxy bumpy. After the first coat is hardened .... dry to the touch but still green, use a sharp paint scraper to remove all the high points. This will allow for a smoother final finish. Note, you will still get a chemical bond with the application of the second coat no matter if its several hours later... so don't worry about the time. A sharp paint scraper smooths green epoxy very well.

With plain epoxy application (not glassing, glassing is just as easy though) Its fairly straight forward to achieve very smooth results with two coats but three coats is a better mil thickness.

I have coated panels in varying temps from 55 to 98 degrees or so and have had no problems getting a smooth finish with System III using all three of the hardeners they offer mixed together or separately. You can use a heat gun to lower the viscosity and surface tension to help the epoxy self-level better in cooler temps or dropping temps, but I prefer a steady even temperature (better if dropping a little) application say 65-95 degrees. The cooler temps (approx 65 degrees and under) keep the epoxy thicker (more viscous) so coats tend to be thicker and won't spread as easy. Warmer temps make it a walk in the park because each application layer is thinner and easier to smooth out ie., self leveling is better. Really warm temps make for thin coats of epoxy and you just don't get to apply as much epoxy with each coat because of this.

The basic procedure is to use a 12 X 12 inch platten (small platform mounted on a light stand or stool ) and mix 3 ounces of epoxy dumping all of it on this small square work surface (using this in lieu of a roller pan). Leave the mixing cup upsidedown at one corner so that all the epoxy will drain from the cup and can be utilized.

Apply the epoxy with a 3 1/2" foam roller (cut the standard System III 7" foam roller pads in half with a hack saw) covering approx 10 square inches at a time with each roller full of epoxy. This the where you control how much epoxy to lay down. Next use a foam brush to knock down the bubbles, etc and move on to the next area maintaining a wet edge. When the epoxy gets mostly used up, use a plastic squeege to scrape off all of the mixed epoxy on the platten and wipe it onto the mixing cup, and make another batch of fresh epoxy in the cup.

I have used this technique on panels as large as 24" X 20 foot and achieved great results. The trick is to keep moving, apply the epoxy evenly with the small roller, and tip it very lightly with a foam brush (only let the weight of the brush rest on the surface when tipping)... THEN move on to the next area. The tipping bush is always moving from the just applied epoxy towards the previous epoxy... maintaining a "wet edge" as in painting. The only time I have ever gotten ripples is when "tipping" with a foam brush bearing down too hard or tipping a 2nd time, ie., going over an area that I wanted to smooth better. I know you can use very slow hardener to allow lots of working time but I have found very freshly mixed epoxy flows on the best and is most easy to spread evenly. Just mix, apply, and move on, and leave it alone... When the aforementioned techniques are used I have found it very easy to use an RAO with 80 grit disks to get a very nice smooth satin finish with not much sanding at all. This method offer max control because you are only mixing three ounces at a time which is easier to deal with. Its a bit slower than just pouring 4-6 ounces out all over a panel but its does result in a more uniform finish.

See post #43 in the following thread...

http://forum.woodenboat.com/showthread.php?110517-John-Henry...-Easy-scarfing-and-glueup&highlight=John+Henry

Hope this helps,

RodB

[Canoeyawl]

One little trick that for prolonging the "kick" time with a large batch is to immediately pour it out of the mixing container onto a flat surface covered with a sheet of plastic.
Then work from that with a roller/putty knife etc.

[kc8pql]

I had the same problem. My solution was putting the epoxy on with a foam roller, and tipping it out with a large cheap brush to remove the bubbles.
The rolling it on definitely made the coat thinner and very even.
+1 You are probably just putting on too heavy a coat. I roll on thin coats and tip with a foam brush.

[Bill Huson]

As several forumites said - ROLL IT ON! Foam roller, slow speed, then trash the roller and have a cup of coffee, or a brew, during a 15 minute or so break, and lightly tip off the finish - foam brush works for that, although I use a soft china bristle brush. Done.

[Todd Bradshaw]

I roll it on using a thin Gougeon foam roller and tip it immediately with a "brush" made from a chunk of a roller hot-glued into a slotted stick. Thin coats -usually 5-6, no sanding between coats, fast hardener on painted boats or WEST 105/207 on clear finishes, applied in one long day that's mostly a matter of watching epoxy harden. Then I give it 3-4 days to cure (sanding green epoxy is bad for you). Epoxy resin, applied with any method aside from a mold, doesn't flatten out into a smooth surface that I consider "presentable". How much wavy, lumpy stuff you're willing to tolerate is up to you, but personally, I won't tolerate it. Once the resin has cured properly, a couple hours with a random orbit sander and 80-120 grit will quickly generate a surface that is flat, smooth and ready to paint or varnish on boats in the rowboat size range. I don't believe it took me more than a couple hours to sand the epoxy-coated topsodes of my 22' Starboat using this technique.

http://webpages.charter.net/tbradshaw/star.jpg

[dngoodchild]

Hopefully, this is not a dumb inquiry. Being a newbe in the use of epoxy I need some advise. I am in the process of epoxying the hull of a rowboat but, spending alot of time smoothing out the uneven bottom. What tricks are there to minimize this kind of a problem?

I read somewhere once, that a slightly thickned epoxy (with Cabosil), could be prevented from running by adding a few drops of Glycol to the mix. The only readily available Glycol is Ethylene Glycol (Antifreeze), and I tried that only once. It seemed to work, but I would advise testing it in a small batch on a vertical surface and see if it works.

[Todd Bradshaw]

I think I'd stick with refining my application techniques and understanding that a truly nice epoxy surface generally gets that way by sanding it, before I started adding unknowns to perfectly good resin. Resin drips and runs because it has been applied unevenly or too thick. You're not likely to ever completely eliminate that, but learning the best application methods will keep it to a minimum, making the final clean-up pretty simple and straightforward. At the same time, you avoid the possibility of adding some sort of chemical contaminination that all too often causes more problems than it fixes. If all the epoxy manufacturers had to do to make resin that doesn't drip is add a little anti-freeze and cabosil, they would be doing it and charging extra for it.