Epoxy Tricks

[Howard]

Gabe:

 

There would be a lot of people on this list qualified to write a book, but I'm not one of them. My vote for #1 would be Graham himself. But assuming he does not have the time or inclination to take on such a project, my vote for #2 would be Alan Stewart, who could ghost write it for Graham. In addition to having worked in Graham's shop for the past few years (so knows a thing or two about slapping plywood together), Alan is an accomplished sailor and has seen first hand what happens when these boats hit the water. What matters and where. Aside from all that, he is young enough to still be banging away at the keyboard at 2 AM not realizing what time it is. That is how those things get done.

 

And with luck, all the book sales royalties flowing to Alan might pay for a free breakfast now and then down at the diner.

 

Seriously, I do think they could do it and a book even pamphlet like that would be a great thing to include with the plans, along with the photo CD's they offer.

[PAR]

I have to admit that I use to do butt joints one side at a time, but now nearly always do both. I also do stack them up, with 3 or 4 joints over each other and a couple of concrete block supplying the pressure. This takes some planing and layout, spacers, alignment arrangements, etc., but you can knock down a bunch of joints in one operation. I have a 4' x 16' layout table that usually has stacks of plywood scarfs or butt joints covered during the course of any build.

 

With some practice, you can estimate pretty accurately how much goo and fabric to put on the down side, so ooze out is minimized. Most epoxy work is setup and "chase" related. Setup is obvious, but after the goo run, there's a few hours of chasing drips, ooze out, etc., so you don't have nearly as much work "dressing" the joint after things get unstacked.

 

If you click on my "Tips & Tricks" link, you'll see what I include with plan sets. This is aside building instructions and serves as a good primer, though a book from Graham would be very welcome.

[Tgabe]

Paul, your tips and tricks page is excellent- very helpful.   I am still in the learning phase so I glue one joint then see how it turns out. Then I determine what I should do differently, and go from there. I have now done four and each one is better, cleaner, smoother than the last. Once I get good at it, i may try stacking.

[Howard]

Was visiting with Paul (PAR) the other day, and among other things, we got to talking about using xynole polyester cloth on centerboards and rudders (vs. glass, which I was thinking of using). That quickly moved on to the topic of using xynole and a vacuum bagging system to help with the layup.

 

So I got the bright idea of giving it a test, and this is what happened.

 

 

The panel on the far left is xynole cloth, that was simply wet out and left to cure. I've never been too happy with that and after visiting with Paul, now understand why. While it sucks up epoxy like nothing else (one foot square patch took about 100 ml epoxy to fully wet out), the end result is way too much epoxy in relation to the cloth. Worse, apparently it will "float", so you get a resin rich layup, which is not so good. Beyond that, while it seems mild mannered and harmless enough in the dry state, once it wets out, something in the fibers "explodes" into a gelatinous looking goo that cures rough, and never recovers. The panel on the far right is the same as on the far left, except it has about 3 or 4 "fill" coats of epoxy and still has a rough, pebble finish. Done this way, a single finished layer comes out at almost a full 1/16th inch. Under vacuum, the same layer is half that, and while not smooth as glass, certainly is far and away smoother than it would be if you spent all day trying to fair it the other way.

 

So if this is the outcome one can expect, I'm all in for vacuum bagging my CB, rudders and perhaps even the inside of the CB case.

 

My process for this test was easy. I simply used one of those garment vacuum bags. I got mine from Walmart and used our household vacuum to suck the air out.

 

Process is to put down the cloth, wet it out, then a layer of Peel Ply, then a thin layer of breather/absorbent fabric (I used some 3/16th inch polyester batting I found at local JoAnn fabric store). Put all that in the bag, close it up and hit it with the vacuum. The bag applies even pressure, while the vacuum sucks excess epoxy through the peel ply, where it is absorbed by the breather fabric. The other benefit is any air bubbles left in the epoxy will likely pop, leaving a very clean, clear finish coat with none of the pin holes you sometimes find in glass laminate and especially xnyole, which likes to trap air pockets in the mix.

 

 

There appears to be a learning curve associated with this, but one that may be worth the effort. Once you get the hang of it, the setup time to do this is a fraction of what it would take to fair the xynole down to this degree of finish.

 

For those now wondering if it is this much trouble, why xynole? According to Paul and other sources, it has about 5x the abrasion resistance of glass. It is incredibly tough stuff, which is what you want down below where it will be banging into stuff.

[Mike Vacanti]

I wonder if the abrasion resistance of the vacuum bagged xynole will be as good as non-vacuum bagged xynole? I wonder if the greater abrasion resistance of xynole is at least partly as a result of the thick layer of epoxy that is required to fill it.

[Howard]

Mike:

 

As I understand it, the higher the ratio of glass to epoxy we can achieve (assuming full saturation of the cloth), the better. Too little and the glass is starved and weak. Too much epoxy is just as bad. I suspect that in most of our wet layups, we err to the side of too much epoxy.

 

My guess is if a builder wanted to maintain a full 1/16th thickness of xynole, he would be better off with two layers of cloth, vs. one layer, saturated and floating.

 

Hopefully, someone with better understanding of this than me will chime in.

 

Will also be curious what results can be obtained just with peel ply over the cloth and not vacuum bagged, as would be the case on bottom panels and topsides. Vacuum bagging those would likely be beyond the ability of most home builders, including me.

[PAR]

Xynole get much of it's abrasion resistance from the high resin to fiber ratio (my assumption). The polyester or polyacrylic fabrics that make up these types of materials (Dynel and Xynole) are weaker then 'glass fabrics, but when combined into the epoxy matrix dramatically improve abrasion resistance. How much resin to fiber, well I just don't know frankly, but bagging does help laminate density, thickness and finish. Yes, it does take some practice Howard, but it's good to see you're taking on my challenge. Blades and boards live in a tough environment, so anything you can do to improve their way of life, has to be good. Bagging blades and boards, particularly with inert materials is the real ticket. No rot, no moisture absorption, no weight gain, etc.

 

Peel ply without bagging will just control the surface environment (bugs, blush, dust, etc.), but the laminate will still be thick, resin rich, etc. You can force out some resin with a squeegee or other tool, but a faux bag attempt will be less than a real bagging. Bagging need not be intimidating, though you do need some new equipment and practice, before you try hull panels. I watched a guy crush a dinghy once, when he tried to bag a sheathing to it's outside once. You'll have to learn this and other lessons first, before risking your pride and joy. There's a fair bit of information about bagging online, so start your research and practice on small stuff first. Once you get a feel for it, you'll bag more stuff.

[Howard]

With curiosity running high, I laid up another panel with xynole cloth, this time just peel ply over the cloth......nothing more.. No clue what the resin cloth ratio would be, but the finish was just as good as with bagging, with none of the pebbles or rough finish as before.

 

The cloth was saturated to the same level, and when the peel ply was laid down, it wet out, but nothing came up through it. In fact, I had some extra epoxy, so simply poured it onto the peel ply to see what would happen. It wicked through the peel ply into the cloth side vs. out of it. So I assume the resin to cloth ratio remained high vs. the bagged process where the breather cloth was well saturated with excess epoxy that expressed out through the peel ply.

 

As near as I can tell, thickness using this method returned to the 1/16th proximity. If someone told me I could have a xynole covered boat with that level if finish, with none of the filler coats and tedious fairing, I'd sign up in a heartbeat.

 

Not sure about the foils, which I might still vacuum bag with perhaps two layers of cloth, but this looks promising for the hull bottom, topsides and decks.

[Navegar]

this reply  is in line with post 136 relating to epoxy amine blush and its impact on gelcoat.  I agree with Howard  (post 137) that in one off plywood construction, paint ( either polyurethane or epoxy based) rather than gelcoat is the preferred solution to protect the epoxy structural bonds  from the ravages of the sun.

 

That said some of us need to repair our polyester/gel coated plastic boats.  I prefer epoxy to polyester resin for any structural repair.  

 

I have found if I water wash off the blush after the repair has cured, I can achieve reliable gel coat adhesion to the faired and washed epoxy repair.  My experience is limited to West epoxy, and Evercoat gelcoat.    Wet sand the gelcoat nothing heavier than 400 grit,  less is  better 1000 if you can get it, and then a 2000 grit rubbing compound on a soft rag, all wet.  if repairing white gel coat, only tell will be in the slightly grayer shade of the old white gelcoat.  the danger will be cutting into and through the preexisting adjacent gelcoat. If that happens you have expanded the gelcoat fairing task.   masking can help reduce this risk.

 

West offers the following guidance on this subject:

http://www.westsystem.com/ss/polyester-over-epoxy/

[Navegar]

The Shinto Rasps are absolutely fantastic. They are also sold through Duckworks online. Chuck and Sandra began carrying them because of my suggestion Good prices too.

 

http://www.duckworksbbs.com/tools/shinto/index.htm

I had not seen these before, very interesting

here is a woodworkers review and quite positive:  http://www.popularwoodworking.com/woodworking-blogs/chris-schwarz-blog/the-venerable-and-inscrutable-shinto-rasp

[Howard]

Not sure if I ever mentioned this, but if not.........

 

This is what I use to stir epoxy batches larger than a pump or two. Nothing more than a piece of stirring stick glued to a 1/4" or 5/16" dowel rod. Chuck that into a cordless drill and give it a whirl. Cheap and effective.

 

Advantage is it mixes fast (20 to 30 seconds max) and does not bring in all the air bubbles that I normally get with just a stirring stick. No need to clean it up. I just let the epoxy drip off. Once it gets gunked up too bad, I make a new one. I have 4 or 5 of these laying around most of the time.

 

To make the thing, I have the dowel rod ready and when I use a stick to stir up some epoxy, I just lay it flat and the dowel on top of it. The piece of stirring stick 90 degree square to the dowel rod works, as does a slight angle. Piece of stick is about 1.5 inches.

[Hirilonde]

I wear my epoxy just fine without mechanized help 

[Howard]

That would be variable speed cordless drill. I eventually figured out you need to run it pretty slow at first.

[Howard]

Am cross posting this with a thread on the main forum.

 

Have done a lot of head scratching on finding a good way to cut the synthetic fabrics like xynole and dynel. For normal glass work, and with the stuff that I now realize is dynel, these cut ok with either scissors or a hand held rotary cutter. My rotary cutter is a Dritz I got from JoAnn fabrics. It will not cut the stuff I now know to be xynole. About all I have found that would cut it is a pair of heavy duty serrated scissors. While they will cut the stuff, it's not pretty. With bunching, etc, I normally get a ragged, jagged, saw toothed edge, so if you are trying to cut it neat, good luck.

 

What I have found works well is electric scissors. Places like Jamestown Distributors offer some good cordless options, but cost around $100 shipped. Decided to try a cheaper option and found lots of older Dritz corded electrics on ebay for about $15 shipped. They go through it like a razor through plastic sheeting. With those, you can follow a straight edge or a graceful curve and do a good job of making a smooth neat cut. (Margin threads will pull, but no way I can see to avoid that).  Cordless would be handier, but for now, this is what I'm using. These were made back in the 1960's. Mine were made in Switzerland and appear to be well made, at least compared to what I would expect to come from China if made today. Quality could be an issue, as all of these are used to some degree, but the ones I found look almost new, with no visible wear at all.

 

While this is the ticket for cutting it dry, this still doesn't help when cutting it wet (it will bunch up and slide around, but won't cut), but if you wait until it has kicked to the point the epoxy is gelling up and will barely move, you can cut it with a razor sharp utility knife, then lift off your waste piece. That will leave you a neat edge.

[Don Silsbe]

Does anyone have any experience using microballoons as a fairing compound?

[Chick Ludwig]

Yep. Got some.

[makenmend]

I have some and it works pretty good, sands easily, but can leave very small indentions after sanding. I recently tried the Quick Fair from Duckworks, a lot more convienient, dries much faster and sands great

here's the fairing at the bow where 2 layers of glass needes to blend in,and the edge of the sheathing.

the same from different angle

then primed, looks good even up close.

 

 

MM

[Chick Ludwig]

Since micro balloons are hollow, you will get those tiny indentations. They never bothered me. I always finish with a primer or coat of resin which seems to fill them. My experience was with polyester rein as I used the micro balloons when I built fiberglass boats. I don't think epoxy would be any different.

[Don Silsbe]

So , you use only microballoons and epoxy? I bought a small tub from Jamestown. I'd lile to use it to fair the tape's edge, among other things.

[Don Silsbe]

Makenmend,

Lease tell me about the deck in these photos. How did you do it? Will you glass the under side? I want to have a strip-built deck (black walnut) on my BRS15. I'd welcome any tips you might have for me.