Thickned epoxy and filling the weave

[cs]

I've used thickned epoxy for a fairing compound before. I've thickned with wood flour and with "Q" cells. After I put on a layer of glass on my weekender I plan on thickning some epoxy with talc and fair the surface.

My question is this. When using thickned epoxy on Horz. surface there is no problem, but when it becomes non-horz. (don't even have to go vertical) the epoxy wants to run downhill (you know that gravity thing). It don't matter how thick I get (this side of to thick to work) it still runs. What do you do to combat this situation?

Chad

[NormMessinger]

Well, lessee...

Wood flour does not make epoxy thrixotropic so the epoxy can run right out of it. But it is too hard to sand in any case to use as a fairing medium.

I don't know if talc makes goop thrixotropic or not but it makes it much to hard to sand easily.

Q-cells should be okay. Microballons are my dust of choice. Mix as much in as you can stir. Make it almost dry. Squeegy on a little epoxy just to wet the surface and form a tack for the dry mix. Putty it on. Let it cure and sand. Once you have your surface fair apply a light coat of epoxy to fill the cell or ballons that were broken open by sanding. Sand and finish.

Some have used a toothed spreader to lay on the first coat of micro. Long board that. You'll have less to sand and when you get everything on the same plane all you need to do is fill in a few valleys.

Micro should not be more than about 1/8" thick anywhere.

If you are just filling weave don't make the micro quit as thick and use an unknotched squeege.

Etc.

--Norm

[capt jake]

I'm with Norm. Microballloons and I use just a little bit of fumed silica to make the mixture 'smoother'. Not too much as it is very hard to sand.
G'luck! smile.gif
jake

[cs]

I think I see my problem. I've been trying to put in on to thin and use a squeege. You're saying thicken till real thick and trowel on.

BTW talc should be easier than wood flour but stronger than Micro ballons right? Would that make a tougher surface?

Chad

[Todd Bradshaw]

If all I was doing is filling the cloth weave, I wouldn't thicken the resin with anything. Why add something that is going to make parts of the surface either harder or softer than other parts when you do the final sanding and fairing? It also makes the surface different colors and that makes the surface smoothness difficult to see until you finally paint it - at which time, it's too late to smooth-out the humps. People have been filling cloth with plain resin on strippers for better than 30 years. It works, it sands evenly and allows you to keep track of the cloth and the thickness of the filler coats on top of it better. Talc is a mistake that you don't want to make.

[capt jake]

I filled the weave on my kayak with un-thickened epoxy. I was after a bright finish, so I had no options. It took 8-9 coats because of the sagging (and that was tilting the boat to minimize the sag!).
This boat will be painted and the thickened is going much faster! :D

[NormMessinger]

Good point, Todd. For a boat. I got reamed pretty thoroughly on a forum I never go to any more (sensitive soal that I am) for suggesting airplane methods for a boat. I can't see much difference (yeah yeah on has wings and one is a hole in the water, the other in the sky but, both holes soak up money, so...)except we are not so concerned with weight on a boat. So use raw epoxy to fill the weave on your boat but use my method for your airplane. And do the filling early so you don't have to sand off the tops of the weave to get a good chemical bond.

--Norm

[capt jake]

So use raw epoxy to fill the weave on your boat but use my method for your airplane But Norm, this is the method that System Three describes for fairing boats (notched trowel, etc)! Now I'm getting cornfused. :D

[NormMessinger]

Fairing, not filling weave, maybe? But ya know, the boat should be pretty dang fair before the glass is applied thus obviating the discussion. (Like I could practice what I preach._

--Norm

[Todd Bradshaw]

That's the difference right there. There should be very little, if any, reason to do heavy fairing on most of the surfaces of a glassed plywood hull. In this case, he just wants to fill the weave of the cloth. The method with the notched spreader is used for removing humps, ridges, etc. It's been used on a lot of hulls from welded aluminum 12-Meters to high tech, strip planked trimarans built into female station molds. On boats like those made from Duracore, where you don't want to cut into the thin surface veneers on either side of the balsa-cored strips, the strips are glued-up, the glue bumps are knocked off and the hull is glassed. The ridges between the strips are still there and the entire outside hull surface is then faired using the notched spreader and a fairly thick layer of microballoon goo. I've used the technique and it works pretty well, once you really nail down the proportions of your mix (too thick is hard to spread, too thin and the ridges flatten out into blobs).

There is no question that plain resin-filled glass is more abrasion resistant than microballoon/resin filled glass and it really doesn't take much more work. Yes it will take more filler coats, but what is the big deal with that? They're fast and easy to do. For just filling glass on a hull that will be painted, this is what I do:

Glass the hull.
If I need to wrap the stems with bias-cut strips of cloth, I wait until the main part has solidified just enough that it won't be disturbed and then add the strips. As soon as this gets solid enough, I roll on a coat of epoxy (I use WEST 105/205, but whatever)with one of those yellow, Gougeon rollers (some people prefer a squeegee). The object is to put a fairly thin layer on to avoid drips. As soon as that is solid, I'll add another coat. This continues until I've got five or six coats on. Each coat takes about a half-hour to apply and requires almost no skill at all. I'll roll on coats until the weave disappears and then add one more as a cushion for sanding. Generally, on a boat that size, with fast resin, you can glass the hull and apply six filler coats in one long day, most of which is spent watching TV, waiting for resin to harden.

If I intend to break the job up into a couple days, I like to get at least two coats on before I stop so that there is no chance of having to wash amine blush from the deep, unfilled glass weave. Before adding any coats after an overnight break, the hull gets a fifteen minute "bath" with water and a Scotchbrite pad to remove any amine blush and you're ready to roll-on the next coat.

After the last coat, the hull is allowed to harden-up for a couple days, washed down with water and the Scotchbrite again and then sanded smooth with a random orbit and 80 grit, followed by 100 grit if the paint calls for it. You can sand out a hull that size in an afternoon, easy. In comparison to something like hanging a plank or fitting a breasthook, filling glass is a snap. Trying to devise some quicky fill mixture to save having to put on a few filler coats seems nuts to me.

[capt jake]

Hey Todd! Maybe a silly question :D but..
When I built the kayak the designer recommended washing the cured epoxy with laquer thinner to rid it of blush. Now mind you, I don't think I even know what amine blush is, as I have never encountered a waxy film on my epoxy after it has cured (West and Raka, both).

The laquer thinner seemed to work great. But I am still (blushing :D ) wondering, as I have the inside of the cockpit that would be rather hard to 'wash'.
thanks,
Jake

[Todd Bradshaw]

I've seen all types of solvents recommended for blush removal. I've just always followed the advice from Gougeon Brothers to use water. It's cheap, won't burn, poison you or explode, doesn't stink and washes off your hands with er...uh....water. At first, they suggested plain water, then for a while they suggested adding a shot of houshold ammonia and as far as I know, the final solution was plain water and a Scotchbrite pad. It's also important to lift the blush off the hull as you wash and dry it, rather than just move it around, so you don't want to skimp on water. I would imagine that inside the cockpit, I'd try a fairly stiff brush and water to get down into the weave (if it wasn't filled while the cloth layer was still pretty green) followed by clean rags and decent time to dry out before putting any resin on it.

With filler coats, I would imagine the result of amine blush contamination might be layers flaking off during sanding or from abrasion in use, etc. So far, I've never had a problem and the hulls sand evenly (all the way down to the wood if you go that far - back in the old days, we used to do our finish sanding with a big, heavy B&D Wildcat disk sander that we called "the hog").

I've seen plenty of posts on other boards by people who act like amine blush is something to fear like the plague and morons spouting that nobody should ever use a resin that blushes. I figure it this way - some of the most vulnerable, highly-stressed parts of my my iceboat are built using WEST epoxy, as are those on about 90% of the iceboats in the world. If it fails, my ass is likely to be spread in a thin layer all over a frozen bay. I take blush seriously and whether it's there or not, automatically assume that it is and would with any brand of resin, regardless of what the manufacturer's hype claims when they're trying to get you to buy their product. It only takes minutes to be sure that there really isn't any present.

[capt jake]

OK, thanks Todd. I appreciate your feedback! smile.gif

[cs]

So don't use any fillers just un-thickned epoxy. What do you do when it is not horizontal? I've had problems when appling to just plain plywood with it running. Is the answer the weave on the fabric and thin coats?

Chad

[capt jake]

Hope Todd isn't looking.... my vote is for the thickened mixture of microballoons and pox /w a dab of silica. shshhhhhh don't tell Todd...
Mix it like Norm said...... shhhhhhh

[Todd Bradshaw]

I suppose that when you guys paint the bathroom walls you remove the drywall and lay it flat on the floor to prevent any drips in the paint???

[cs]

Originally posted by Todd Bradshaw:
I suppose that when you guys paint the bathroom walls you remove the drywall and lay it flat on the floor to prevent any drips in the paint???That may be the reason the wife don't let me paint.

I guess what you're saying is put it on thin.

Chad

[cs]

Todd I just re-read one of your post up there and I see where you say thin coats. Must have missed it the first time.

Thanks

Chad

[Charlie J]

Ah Todd - thanks! Another voice in the wilderness, crying out - "Blush is no big deal- just wash it off!"

I been hearing so many horrors tales about "don't use this epoxy or that epoxy cause it may blush" to which I reply "SO WHAT? Just wash it off."

Glad to see one more voice of reason.

[Ross Faneuf]

Another voice for 'just wash it off'. I use a little common cleaning ammonia in water - about as much as my Mother used to clean windows before window cleaner came in a bottle.

I fill weave with epoxy thickened about to mayonnaise or a little more with straight sillica. This doesn't move or sag at all, and gives you a very clean, fair surface which also sands well. This is for painting, of course - the finish is opaque. I prime with Interlux epoxy primer, which goes over it very well. I have no experience with filling cloth and trying for a bright finish.

[Memphis Mike]

"So don't use any fillers just un-thickned epoxy. What do you do when it is not horizontal? I've had problems when appling to just plain plywood with it running. Is the answer the weave on the fabric and thin coats?

Chad

You work thats what you do. Wet out the
surface first. Lay on your glass and apply
another coat. Let that sit until a little
tacky and then put on another. Sand and then
apply your final coat and then sand again.
Double up on the hardner. These people
don't understand the humidity we are
dealing with here in the Mid South.

[Memphis Mike]

Its a whole different animal here. You
need to use more hardner and work fast.
Double the hardner and try it on a test
surface. You'll see what I mean.

[ 07-04-2002, 08:52 PM: Message edited by: Memphis Mike ]

[Memphis Mike]

BTW, don't use any filler, three coats
is plenty. Problem solved.

[capt jake]

Frankly MM, with the 8-9 coats of unthickend epoxy it took to completly fair out and fill the weave in the bright kayak I built, I can't see why NOT to use filler to fair a surface that will be painted.

I can see 3 coats that are thickened would fill 'er up, but not 3 un-thinckened coats, unless I am missing something here? smile.gif

[NormMessinger]

Double the hardner and work fast, you say. NO WAY JOSE. Not if you are using epoxy. Polyester, okay but NOT EPOXY! If you can't mix epoxy the correct proportion better slightly rich with resin which may eventurally cure but not rich with hardner.

Where'd you go to school, boy?

--Norm

[capt jake]

Aye, I can't mix a batch of fast hardener epoxy and spred it fast enough to keep it from burning through the container at times (of course mass enters in, but I find this in even smalll batches).
Hey, to each their own.....
Have a great day......

[Todd Bradshaw]

Norm's right on the hardener. Doubling it will ruin epoxy and even on polyester you're asking for a big, sticky mess and maybe even a fire in the pot. I used polyester back when I started building strippers in the mid 70's in Central Illinois, which is plenty humid and never had a need to double the catalyst. If anything, in hot weather, we reduced it. There are charts available which tell you how much catalyst to add to polyester for different ambient temperatures. Ignoring them is just asking for trouble.

The way you prevent drips on vertical surfaces is to use thin layers and control thickness. Whether your putting on resin, primer or paint, the more uniform it is in thickness, the less it runs. I still get some resin drips when I fill but they aren't a problem since the whole hull will eventually get sanded and all the filler will be plain resin, so it all sands the same.

It's also absolutely nuts to try to predetermine how many filler coats it's going to take. It will vary too much with temperature, resin brand, application tool and the way that particular builder applies the stuff. The idea is not to apply two filler coats, or three, or six, or even nine, it's to fill the cloth with however many coats it takes and to leave yourself a little extra thickness for sanding without cutting up the glass cloth. The strip building forums are full of posts by people who followed somebody's advice, put on a prescribed number of coats and then proceded to sand deeply into the cloth and are now wondering how they're supposed to patch the bad spots.

Since this boat won't be finished bright, all manner of stuff could be troweled into the weave to do the job quicker (the idea of boatbuilding is to build the thing as fast as is humanly possible and cut any corner that can be cut with some sort of techno-stuff, isn't it?) I don't use plain resin because I'm a purist or because I like putting on lots of filler coats - I use it because I think it's easier, probably less time consuming and it gives me a tough, uniform surface that sands evenly enough that you can apply glossy paint or varnish, sight down the side of it and not be embarassed by the bumps, dips and rough spots.

In the time it takes you just to mix your filler and get the consistency right, I can roll a quick coat on and be inside polishing my toenails, waiting for it to cure to the touch. I'll have to put on more coats than you, but they only take about 20 minutes each to apply and I just do them until the thickness is right. Then I let it cure, wash it down with water and sand it smooth.

After you've carefully scraped your mix into the weave and maybe applied another layer of something to give you enough cushion for sanding without cutting the glass, you are ready to wash it and sand it smooth. If your mix contained microballoons or some of the other fillers, you now have a surface covered with tiny, cut-open spheres, which are all full of air and which make a lousy surface for painting over. So, you need to seal them with a coat of plain resin. It won't displace all the air, but it's thick enough to overcoat the surface. Next, you wash it down again and you are ready to sand, but your entire cushion for sanding is one layer. A little too deep and you expose the microballoons again and should re-coat that spot, then re-wash and re-sand it.

In my book, that's too much work and too tedious. With plain resin filler, I only sand once and I can easily see little peaks of the glass threads if I start to sand a spot too deep. I've never found that primer over epoxy does anything to improve the quality, adhesion or durability of the paint job, so I don't use it. The sanded hull is plenty smooth, so the surface doesn't need another layer of stuff to be applied and re-sanded.

I have modified filler coats at times with a few compounds, but to change the material, not it's coverage. Graphite powder can make the surface a little slicker if you plan on sliding over rocks. It's messy to sand-out though and can cause heat problems on boats that are car-topped upside-down and left in the sun. Aluminum powder is what's in most of the barrier-coat fillers. It makes the resin harder to sand and can slightly improve abrasion resistance, but as far as I can tell, needs a plain resin overcoat to get a good paint job. The sanded aluminum powder specks on the surface start oxidizing immediately and don't hold paint well, so without the overcoat, tiny pits appear in the paint job.

A little colodial silica probably wouldn't hurt, if you really need to reduce the number of filler coats, but it sands harder than the resin that holds the cloth on, so you don't want to go through it and hit the softer layer underneath. How about this one - do what Grand Canyon Dories sometimes do on their runners - mix in some Carborundum grit and essentially make the bottom of your boat a giant sanding block. You can just pull it up on the ramp and if anything gets damaged, it'll be the ramp!

[cs]

Todd you have won me over. I think my problem in the past has been that I'm a little heavy handed.

Thanks for all the advice.

Chad

[Wiley Baggins]

I've had some success in maintaining the working life of epoxy when working in hot weather by setting the container of epoxy in a container of ice or ice and water.

[Ross Faneuf]

These replies are a good example of an old engineering aphorism - that a problem either has no solution, or many solutions. I read through Todd's method, and think that it sounds like a LOT more work than mine; he reads through my description and thinks the same thing (that is, that the way I do things sounds like WAY too much work for him). And we probably get much the same results - I don't have drips, sags, or unfair spots either. And I like the way sillica filled epoxy sands, too.

I suspect that once you experiment and find a method that works for you - well, then it will work for you. Take comfort in the fact that there is clearly more than one way to do this successfully, and go with the technique that sounds best to you. Consider that there are maybe a dozen ways to trim miter joints for a perfect fit.

Setting expoxy in icy water works very well (as does learning to work fast smile.gif ). Also note that it kicks much slower after it's spread out, as the spread-out later dissipates the accelerative heat generated by the curing action. For bedding cloth on upside-down work, I usually have the cloth positioned, then pour an entire batch of epoxy right on the hull immediately, rather than spread with with a roller or something like that, then distribute it with a squeegee. That gives me the fastest job, I don't have to worry about lifting the cloth with a roller, and I get very even coverage.

Here in Maine, we often have the opposite problem - we have to set the epoxy in warm water to keep it from getting too thick to work with.

[thechemist]

Some fillers will create thixotropy, and about half-way through the curing cycle the "thickened" epoxy sags. This is caused by the polar amines getting used up in the curing reaction, and no longer providing the resin-filler interaction that creates thixotropy.

What that means is that the common fillers/thixotropes that create thixotropy without premature sagging, for polyester resins, don't work for epoxy products.

Thixotropes that are more effective in epoxy systems are those that are not so sensitive to the state of cure of the resin system. Mixtures of clay and fumed silica are among the more effective non-proprietary sytems, and you should be able to find those among the various packaged powdered fillers offered by Evercoat, West, and others. Bentonite is another name for a particular clay...it might be called that. Also, potter's supply houses, and artsy-craftsy ceramics hobbyist outlets sell clays of various sorts...almost any works. Figure roughly one pound of FUMED silica [not precipitated silica, that's a different animal, as is ground silica.] and a few pounds of clay...the particular kind of clay will determine the best ratio, as clays are microscopic platelets of different sizes, and the microscopic mechanical interactions that create thixotropy are rather dependent on clay properties.

These materials, unlike sawdust or cornstarch, are completely waterproof and will give high-quality results with anyone's epoxy, provided only A and B are thoroughly mixed, then transferred to a second container and remixed before adding the powders. The reason for the second mixing is that even a small amount of unmixed A or B, when mixed in with fillers, can create screwed-up properties and excessive water absorption all out of proportion, especially with really fine fillers such as clay and fumed silica.

If you want to add microbaloons to THAT, fine. It will make the mix easier to sand, and will fill the weave just as well. Microbaloons, by themselves, are microscopic ball bearings and will raise viscosity but not create any thixotropy.

It is a lot easier to fill the weave with some filler, either homemade or premanufactured, than paint on many layers of liquid. It's just not always so easy to find a suitable commercially available product on your local store shelf, nor to make your own.

The phenomenon known as Squeegee Drag will make it apparently difficult to fill any depressed areas, as the squeegee tends to drag out material as it passes over. A brush similarly drags liquid out of the weave as the bristles drag the liquid across the surface, thus producing a coating that still telegraphs the old surface to the top of the new coating.

A layer of polyethylene over the surface, and squeegee -work over that, leaves a surface evenly filled when the polyethylene releases after the resin cures. Also, holding the squeegee at a very shallow angle greatly reduces squeegee drag and gives a better fill in one pass with fillers.

[Todd Bradshaw]

"It is a lot easier to fill the weave with some filler, either homemade or premanufactured, than paint on many layers of liquid."

Depending on your perspective (total cure time, number of trips to the garage, possibility of drips, etc.) this may be true, but keep in mind that the actual filling, no matter what you use to do it, is only a portion of the job of getting a fair, smooth surface that's ready to paint - and it's the easy part, the part that takes almost no skill at all. Whichever method you choose, the real test will be learning how to efficiently generate something that paint looks good on. As Ross said, different strokes for different folks. I've pretty well beaten my horse to death on this one, so I'll shut up - at least until you build your strip canoe and then you won't have a choice. [Maniacal laughter fades off into the distance.]

[ 07-05-2002, 04:08 PM: Message edited by: Todd Bradshaw ]

[Ross Faneuf]

My horse, like Todd's has joined the Choir Invisible. But I should mention one last thing; I use silica for fairing because you get a really smooth surface off the squeegee/trowel/whatever - as clean as the edge on your tool. Many of the other fillers leave much poorer surface - possibly because of the actual physical size of the particles, possibly because of clumping.

[Memphis Mike]

Sorry CS, I was considering polyester
when I made my comment. I had to double
the hardner to get it to kick in this
heat and humidity.

[cs]

Lots of great info found here.

I'm still a couple of weeks away from actually doing this, but I have decided that I will defintly use Todd's techinique, because as he hints I've got a stripper waiting in the wings to be built. This will give me plenty of practice.

Now to throw another wrinkle in.

Cloth is flat and boats are curved. Now anytime you lay flat on curved you get wrinkles. What is the best way to combat this? Do you cut the cloth at the wrinkle and overlap?

Chad

[Memphis Mike]

http://www.diabloboat.homestead.com/glassing.html

Check out this glass job and it was done
by a complete beginner.

[Memphis Mike]

CS, the best way to avoid a lot of wrinkles
is to not let them develope in the first place.
When I bought my cloth it came on a roll and
I kept it that way until use. If you fold
glass cloth it will wrinkle. The wrinkles can
be smoothed out with the squeegee and roller.

[Todd Bradshaw]

Some people lay cloth into wet resin, some lay it out dry, some saturation-coat the hull first, some don't. With fast hardener, you don't have much time to chase down wrinkles, so you need to stretch out the cloth dry and smooth out the bulk of the wrinkles with a gloved hand, dry roller or squeegee before adding resin. With slow hardeners, you have more time to work them out and it's possible to lay the cloth into wet resin if desired. In either case, unless you're trying to wrap the glass around a sharp bend (like a stem) you seldom need to cut it. The weave is loose enough that it will conform to a pretty irregular shape with a bit of coaxing and the excess fabric forming the wrinkles gets absorbed and disappears.

Right after laying the cloth on the hull (either wet or dry), if you and an assistant will grab the piece at either end and give it a tug (lengthwise and downward) much of it will start to take the shape of the hull and you can then concentrate on any small problem areas, smoothing them out. I usually cut off the factory woven selvedge edge on the fabric if I'm using full-width cloth. It loosens-up the edges and seems to make it easier to get the cloth to conform to curved shapes.

[Memphis Mike]

I found that on the smaller verticle areas
such as the transom, it was easier to wet
out the surface first. On the hull, for me,
it was easier to put the cloth down dry and
then apply the glass.

[On Vacation]

Nice album, Mike. Never knew it existed. Great inside detail. Some beginners should follow this album in a first attempt of building. I like the neatness of your materials and working areas that shows in the shots. Patience for this type of a job will also make for nice finish product.

[Memphis Mike]

Not my album Oyster. It belongs to a
friend that I consulted when I built
mine. I have a simular album but not
online. There are pics of my boat
there though. Click on Other Diablos.

[Memphis Mike]

Also, if you can come up with the
ideal temp. and humdity, its Ok to
wet out large areas first and then
put on the glass. Its easier to
draw the glue up through the cloth
with a roller than to force it down
onto the hull surface.

[JimJ]

Just finished applying glass to the edges of a rudder stock (6 x 9mm ply laminated).

I stood the rudder stock vertical so I had one horizontal, one vertical and one inclined face onto which to apply the glass and epoxy.

I used HT9000 with standard hardner.

Method was

1. Apply a coat of epoxy to the ply edge.
2. Laid the fiberglass on in a strip that I cut from woven glass fabric so the fibers ran at an angle of 45 across the strip.
3. Wet out the fabric until it was completly transparent.
4. Applied two extra coats of the above epoxy.

I finished at 2 am (I did this while watching Leyton win Wimbleton) so it was subject to low temperatures for here ) about 6 deg C. Epoxy was thicker than normal due to the low temperature.

Awoke this morning to find a nice smooth surface on all three surfaces.