First-Time Fiberglasser - Couple of Questions

[AndrewT]

I'm on a break from mandatory training class, so this is going to be real short and sweet.

1. Any reason to prefer "wet" application method over "dry" method for an upside-down hull? I tried the wet method last night, and, as I'm working alone, it was difficult. Couldn't get the cloth in-place without a few wrinkles because it wanted to stick to everything it touched. Seems like dry would be easier on the bottom of the hull, since I could tack it in place in advance.

2. I have a few areas where the weave is still noticeable (i.e. not completely filled); should I just lightly sand those areas and apply more epoxy?

3. I have a couple of spots that have a "bubble" - mainly the areas where wrinkles developed as I was trying to get the fabric in place. Do I just sand them down and re-apply epoxy? Sand them down and patch with a new piece of 'glass? I assume a repair is possible, just not sure how to go about it.

Thanks in advance for your help, and I'll check back next time they cut us loose for a few minutes.

[CundysHarbor]

1 I have always used the dry method.
2)If the first bit of epoxy has cured, you need to sand before applying more resin. I prefer to mount dry, add a second coat when the first is a little tacky and follow with a third when the second is almost cured. I have had no luck using rollers for the first coat but use them for the second and third coats.
3)For the bubbles, I would sand those areas fair, apply more glass to the divots, sand smooth after the epoxy cures and then recoat the whole boat twice.
Don't forget to cover up before sanding the itchiest stuff there is.
Dave

[Oldad]

Dry

[Bill Huson]

dry - less mess.

[AndrewT]

Okay, I'll try the dry method for the next go-round.

In the meantime, what does the exposed weave in the fiberglass mean? (I.e. there are some areas where I can clearly see the woven pattern, and some areas where the pattern is invisible). Does that indicate not enough epoxy was applied in that area?

[Dusty Yevsky]

Okay, I'll try the dry method for the next go-round.

In the meantime, what does the exposed weave in the fiberglass mean? (I.e. there are some areas where I can clearly see the woven pattern, and some areas where the pattern is invisible). Does that indicate not enough epoxy was applied in that area?

yes, that is correct. You want to fill the weave with enough epoxy so that when you sand out you will be sanding epoxy not glass. Glass is what provides the strength in a FG/epoxy matrix. It's OK see the weave when you sand but definitely do not sand INTO the glass. A couple or three coats of epoxy should do the trick.

[John Meachen]

There is almost no task I like less than sanding epoxy/glass sheathing.It can be made almost bearable by using peel-ply to eliminate the amine blush that gums up abrasives and it helps with filling the weave.The durability of the finished job is the sole justification for the effort and expense and if you can avoid the temptation of a bright finish the minor cosmetic blemishes disappear when the paint is applied.

[Todd Bradshaw]

My rule of thumb is always to apply enough filler coats over the weave that the woven pattern completely disappears - and then add one more. I never sand green resin. It takes epoxy about a week to fully cure and during that week, you are just asking for health/ epoxy-sensitivity problems by sanding it. If you get that stuff due to poor work practices, you're done working with epoxy for good. You can still get a good bond between layers the next day without sanding if you will simply wash the boat down with water and a Scotchbrite pad before applying the new resin coats. No sanding is needed. You will likely find the dry method much more controllable. Start in the middle and work outward in all directions. The smartest thing you can do is find somebody else to mix the resin in small batches while you apply it. Your chances of success will go up and your chances of mixing a bad batch of resin because you're rushing will go down dramatically.

Wrinkles that are ground or cut out should usually get patches of new fiberglass to maintain strength over the repaired area. Resin by itself doesn't have much strength at all. Once the epoxy has had several days (minimum) to cure, wash off any amine blush with water and a Scotchbrite pad before sanding. Then your sandpaper will be much less prone to clogging. You also need to watch your speed with sanders. Most epoxy softens at about 140 degrees and high-speed sanders can often generate that sort of heat and more on the surface pretty quickly. At that point the epoxy can actually start to smear, which makes sanding a chore and really plugs up disks in a hurry.

[Oldad]

Just to be clear... you need to use a plastic squeegee to spread the epoxy into the dry glass. As soon as the glass goes clear you have enough epoxy for that first coat, squeegee any excess onto the dry glass. Too much epoxy and the glass will float, you don't want that. You do want to fill the weave but not on the first coat unless you wait till it is nearly set. Then fill the weave with however many successive coats it takes. Heavier weight glass takes more coats to fill the weave.

Oldad says as hot as it was today in the northeast the batches better be real small

[Todd Bradshaw]

My favorite squeegee is a slab of ethafoam packing foam about 1/2" thick and maybe 4"x6" or so (the flexible plastic foam that they use for those pool-noodle things for kids). I save the stuff when something comes packed with it and cut slices off the blocks with the band saw or a bread knife. It's firm enough that you can move resin around and get your cloth down tight to the surface, yet soft enough that you can easily "comb" the surface down to a very uniform weave texture, free of puddles, wrinkles, etc. - and not at all bad looking for areas where you might not want the additional weight of filling the weave. I also like the way their corners resist catching and pulling the cloth as you saturate and work it, which some sharp-cornered plastic blades can tend to do. They're free, work great and are disposable. We started using them back in the early 70s when we were building kayaks and broke, but I haven't ever seen a reason to change.

[Oldad]

And you might want to try poor man's peel ply (6 mil poly film) laid over the wet epoxy after you squeegee which will help reduce the amount of weave filling, at least that has been my experience. If you do try the poly you need to smooth it carefully lest you leave wrinkle lines.

[AndrewT]

What is peel-ply? Not familiar with that term...

[Oldad]

6 mil poly film, used in home construction as a vapor barrier, available at any home center is the peel ply (poor man's) of choice for me. It is heavy, can be squeegeed right over your wetted out fiberglass and when all set (next morning) it rips right off and leaves a pretty smooth surface. Avoid the sharp creases in the poly where it has been folded, does not do so well on tight curves because it wants to wrinkle. Not a cure all by any means but a big help in general. Give 'er a try, can be reused many times. I have even used grocery bags (plastic) in desperation but the heavier stuff works best. Real peel ply is another story but does a similar job only better.

[Todd Bradshaw]

Real Peel-Ply is a light, tightly-woven polyester or nylon-like fabric. You lay it over the wet laminate, squeegee it down tight to the surface and let the resin harden. Later, you peel it off and pitch it, leaving a smooth texture like the finely woven cloth had. They say that any amine blush will pass through the weave and form only on the outer surface of the Peel-Ply, and will then be removed when you remove the Peel-Ply, leaving a surface that's ready to laminate to or filler coat without further prep. I haven't tried that, so I can't say how well it works. I kind of like to be able to see, inspect and if needed, fix the freshly applied fiberglass surface in detail and without anything hiding under other layers of stuff, so I don't seem to have much use for Peel-Ply if I'm just glassing a boat. Once the glass is down tight and set up enough that further work won't disturb it, filler coats are fast and easy to apply and I just do however many it happens to take to completely fill the weave and give me a little cushion for sanding.

One of the dumbest things that I think a builder can do it to try to predetermine how many filler coats the job will take. Different resins, different tools, different working temperatures, different application pressure or techniques, different amounts of resin left in the cloth from the layup process and different stages of your filler resin hardening in the pan will all affect the thickness of the coats you are putting down. If you think you can accurately decide how many coats the job will take before you even start it, you're most likely dreaming unless you've done the same job multiple times in similar conditions and can bank on past experience. Even then, you won't be 100% sure, so it's far better to give it what it needs, rather than what you think it might or should need. Personally, I tend to roll filler coats on pretty thinly, and I usually roll and tip them. It's not unusual for it to take five or six coats over 6 oz. cloth. If that's what it takes when I get to that point, then that's what it gets.

[JimConlin]

Peel ply costs about $.18/ft^2 and 6 mil poly about $.10., so there is a saving.
For comparison, 6 oz. glass and epoxy cost about a buck per ft^2.
When used to cover wet epoxy, poly leaves a shiny surface that needs sanding. It often leaves ridges that require aggressive sanding.
Peelply is quite pliable, so it lies flat, with fewer ridges and waves. It leaves a finish that's ready for the next bonding or coating step.

My squeegee of choice is the 6" plastic bondo spreader. About $.60

[Oldad]

I use that same squeegee, works great and yes, if you are not careful you can get ridges with the poly and that is why I said to avoid the creases where the poly was folded. I often use it on broad surfaces without too much twist or turn, if you re coat before the first application has cured you don't need to sand but it wouldnt hurt to sand lightly. I always use slow hardener so have no worries as to blush. The epoxy I have been using is marinepoxy, fairly reasonable.

Oldad thinks there are lots of ways to skin a cat and as you go along you will discover what works best for you. Got my plans today for Atkin's sailing dinghy Finkledink, a 9 foot pram. Yea!!!

[Mike Vogdes]

I have used a dress lining from a fabric store that is very similar to Peel Ply, I believe it was called Tapan or Tappan or something like that, was very reasonable and performed nearly as well.

[the_gr8t_waldo]

do not "tack" the cloth to the hull, it will only create more work, just when you are trying your darnest to get "it right". a good move would to lay the cloth on the hull, in it's final position. smooth it out by hand and leave it for at least two days to allow gravity to work out the wrinkles and to allow the cloth to take on the hulls shape. start mixing epoxy, only when you are ready!i would add that if the boat has alot of shape built into it, try reorienting the cloth so that the yarns are running at 45degrees to any sharp changes in shape.

[Nicholas Carey]

yes, that is correct. You want to fill the weave with enough epoxy so that when you sand out you will be sanding epoxy not glass. Glass is what provides the strength in a FG/epoxy matrix. It's OK see the weave when you sand but definitely do not sand INTO the glass. A couple or three coats of epoxy should do the trick.

Fully saturated (wetted out) cloth is [should be] transparent. A visible weave — the cloth isn't transparent — is an indication your cloth didn't get fully saturated/wetted out. Transparent cloth and a visible texture is OK: that just means you haven't filled the weave completely yet...in which case, add another coat of epoxy.

[AndrewT]

How long do I need to wait to start sanding/fairing? I feel like I've probably got enough epoxy on the boat now. Weave has disappeared although the fill coats aren't as smooth as I expected. Never could get the foam roller to work. It left little dimples all over the hull. Ended up using about a 6" plastic putty knife. Seemed to work okay.

For what it's worth this is all getting covered by paint. I really don't care what it looks like. Whole point was to waterproof the bottom of the hull which I feel like I've accomplished. I'm wondering if I need to mix up fairing compound and spread it over the last fill coat, or just start sanding the fill coat.

[woodpile]

I think I'd have to rate the technical/logistical requirements and preperation for using epoxy above wether or not it goes on dry or wet. Temperature, humidity, selecting the right hardener, how much to do in one session, working alone or having extra hands, how much to mix at once, preperation for the next batch, timing for trimming edges before it completely sets. I'm far from a master at it but these are some of the things I found important in the beginning.

[AndrewT]

Having just completed my first fiberglassing job, I'm going to have to disagree with you on "logistics" over "wet vs. dry." The logistics part was, for me, fairly simple. I kept the epoxy components inside, in the air conditioning, so they'd be a little slower to cook off (it was 101 here today). In the morning, I pre-measured one cup portions of resin and hardener into Solo cups, and then just mixed up what I needed as I went along. Really wasn't anything to it.

The wet vs. dry thing, however, was a big deal. The first section was done "wet," and I like to never got the fabric in-place and wrinkle-free over the wet hull. Subsequent sections were done "dry," and it was a much smoother deal. Aside from a minor bit of trouble working out a few wrinkles, the whole process was simpler from start to finish using the dry method.

All of the things you mentioned - temperature, humidity, hardener, quantity, etc. - were issues during installation, but they turned out to be - in my case at least - more of a "fear of the unknown" than actual problems to be solved. The temperature and humidity are what they are; nothing I could do about them. Hardener selection was easy - I used the manufacturer's tech support department to determine the appropriate resin/hardener/cloth/application method for my project. I was working alone, and without the option for adding hands, so that, again, was what it was. The other stuff - how much to use and timing - was worked out on the fly and without any significant hiccups. Yes, you have to work quickly (although not "fast"), but it's not like the stuff suddenly becomes unworkable and you're screwed if you're in the middle of something. I started with a small batch, observed how much coverage it provided and how much time it took to apply, and altered my mixing schedule based on the results.

ALL OF WHICH GOES TO SAY, for any first-timers looking at their first fiberglassing project, don't fret too much about most of this stuff. (Caveat - the hull I'm fiberglassing is getting painted, so I really didn't care what it looked like.) Start small and work your way up, and you'll be fine. It's certainly not fun, but it wasn't miserable, either. Mostly monotonous, in fact (although I'm sure sanding won't be a walk in the park).