Fiberglass tips and Adtech Proseal.

[Zach]

http://www.adtechplastics.com/p-88-pros ... eries.aspx

I've used a few 5 gallon pails of this stuff, this year and I have had enough success with it to feel it worth recommending as it is expensive, particularly where west and other epoxy resins can be made to do similar things.

In previous posts, I've talked about hot coating raw fiberglass with epoxy mixed with microballoons or west systems 407 while everything is still wet. I don't do it that way on large jobs anymore, as proseal always sands the same rate no matter who mixed the batch, as microballoons sand differently depending on how much made it into the batch. To get the same consistency through a few different batches is tougher to do, and the same pot of stuff if mixed in a big batch gets runnier with higher resin content the longer it sits.

Proseal is easier to get an even coverage, without making high spots to have to sand out later, as you can apply it with a paint roller or brush. It doesn't lay out smooth at all, nothing like paint... but you don't have to use a squeedgee and try to spread evenly microballoons or 407, that gravity doesn't really help lay out.

It hardens up like you wouldn't believe, and gives you a barrier to prevent grinding in to the fiberglass... and prevents the fiberglass from printing through the painted surface. Hard stuff is actually good when doing fairing work if you are smart about the glass work and leave it deliberately a bit low to the surroundings. If it is hard, when you hit it, you can't make a low spot a real hole...

The resin is very thick, and the hardener is like water so you need to take the time to put each resin batch into a mixing cup before you start your job, and measure out the hardener in another container, then combine as you need each pot stirring very well. I have not used the slow hardener, so I cannot comment... (my supplier doesn't stock slow) the fast is stupid fast, requiring quart or so max batch sizes, 4 inch paint brushes and wide paint rollers of the cheapest variety as the roller and roller frame are destroyed after use.

Pouring the hardener atop the resin does not give an accurate measure, and resulted in a few gummy batches. Whatever hardener they use is strong stuff, as two days later everything was rock hard... but two days waiting on a job is a pain.

It stinks, noxious fumes come off when you open the containers but it really does work as advertised and does a better job than anything else I've found to hide print through short of grinding all the weave of the glass off and then fairing on top of it... which isn't a fun, nor fast way to do things, and actually yields a weaker substrate.

The other thing I have found to be a great benefit, is deliberately leaving the repaired area significantly (just shy of an 1/8th or so) lower than the surrounding substrate. IE, the glass is sitting in a low spot, and not proud of the surface requiring it be ground down to fair it in. Then troweling a thin layer (1/8th inch) of putty over the entire repair to bury it, leaving it high across the entire repair. Epoxy shrinks when it cures, so leave things high. The only glass to grind is the slight overlap of the edge if you are working along a taper. I always lap a bit past the edge of the taper on to the surrounding good material, as it is easier to work the air out of the cloth, and water wash and sand off the shine of a high spot than it is to get in to the edge of the glass. After the glass is ground at the overlap, lay a batten across, and use 36-40 grit on a long board to work the surface down. When the batten reads close at the edges, finish off the sanding with 80 grit. Spray with red or gray primer as a guide coat to double check what your batten says. A ring of paint around the repair means the middle is high still... Unless the batten says you've made a flat spot. Grin.

Half lifes battles, is learning when you are sanding a low spot on a curve thinking its high, and puttying the "low" making a big flat spot instead of that sweet curve you've got in mind. Stiffer battens are better battens.

Fill any air pockets in the putty by grinding them out with a grinding burr on a dremel or air grinder, rather than trying to dish them out with 40 grit on the tip of your finger, or scoop them out with a sander stood on edge. It is faster to use a grinding burr. You have to grind the holes a bit oblong, to pull putty in them. Leave the putty high above the holes, in a blob so you can sand it down once and have it right. When you hit 80 grit, prime it or roll it in resin (depending on if you are awlgrip/alexsealing or going back to west and their fillers...) and buzz it out to the grit of your choice.

On plywood you can grind in two or three veneers (okume/meranti... two-three layers of fir you'd be through it!) or a paint stirrers depth, so that where your seams overlap in a low trough. Works well on foam and other core materials too. Sand down smooth proseal smooth and fair, and then sand out the trough and warp a batten across the gap to give the putty the same shape as the rest of the surface.

Easiest way to get the trench on flat surfaces is a router set to depth. On rounded stuff, is a 4.5 inch mini grinder with an adapter to work with 3m Rolocs. 3m Makes 3 inch roloc grinding discs that are handy, as they are the perfect size to make a trench.

A trough is nice on a rounded surface, as it is faster to use the surrounding area as a guide for troweling putty, than it is to grind down the high spot of an overlapped glass and try to feather it to nothing and not put in a flat spot. A flexible batten that sands with the curve gets the curve in shape, and a stiff straight board sanding up and down, moving over a half a boards with each pass following the curve gets a flat mirror finish... even if you can only move the board up and down 5-6 inches before hitting something.

Zach

[boatsnh]

Hi Zach,
Interesting stuff....A comment you made re: "no print thru" caught my eye.

4 years ago I glassed the cabin sides on my ketch. 1 1/4 mahoghany with 6 oz cloth set in MAS. Finished with WEST 410 microlight/epoxy & used PrimeKote epoxy 2 part primer...Sanded to a nice smooth finish....final coating was a 2 part PU paint, rolled & tipped on which looks nice. Boy....seems like all the glass pattern just "shows thru"on most of the cabin sides....not my best fiberglass project outcome. My thinking is that the epoxy was not allowed to "set" long enough prior to paint (a week or so) or the 410 is not the best stuff to use in this application...sanded easily enough....

I'm going to fix it as part of my "larger" cabin roof/deck project in progress now, since I've got to paint the margins on the deck & cabin top as part of that repair....wondering if I grind the urethane paint down a bit to get "bite" if this is a good fairing compound to fix the print thru...my other thoughts are just to use the classic microballons (glass or phenolic) and epoxy, which in subsequent repairs has worked pretty well....not a huge fan of the 410 anymore.....

Is this stuff available in gallon cans??
Thoughts?
Thanx!
Mike

[Zach]

Proseal is available in gallon cans, direct from the manufacturer. I like glass bubbles more than phenolic ones, for price as well as the sag resistance.

As far as print through goes, 410 actually has a warning about using it on hot/deck surfaces as it will move around. What color is the cabin? Finish cloth works, but the key is not to sand it. In other words, to build out whatever putty you wish to use, or resin coat it while it is green until there is a sufficient thickness above it you never hit it. A smooth surface, of sanded finish cloth prints all to well.

To build out an even coat of putty, you can take a 1/8th inch notched trowel and spread it over the surface, then cone back with a long sheet rock blade and roll the peaks over so you have a smooth "floated out" surface. Or, a small concrete float stood up on its side works well too.

I experimented for a few months using west systems technique of leaving the notches, having half of the putty to sand off. Getting it straight, and then filling the grooves between it. The two different batches, and different age mixes cure differently and leave stripes. I didn't find that an acceptable solution, for fairing, or for greatly speeding up the process... as its better to build something with closer tolerances than an 1/8th inch with battens and string, eyeballed around the curve than it is to trust a longboard to not be sanding a long flat spot into something!

The gist is that epoxy that cures at room temperature, continues to cure with temperature. A post cure. It gets plenty strong at room temperature, but its almost a misnomer to say that it is fully cured as the strength properties continue to improve with post curing.

A perfectly smooth fairing job, in white primer is going to look different the next year after it sits out in the sun and reaches 120-130 degrees for a summer. A black paint job or flag blue, the same holds true except the surface temp is upwards of 160 in the peak, which means it takes some studying not to build something that will delaminate, or sag (410) The worst offenders, are the black painted sections around the front of sport fishing boats. Particularly old boats that never had such a paint job from the start. White gelcoat, going under a black surface that gets sun as it is laid back at an angle... It'll cook whatever leftover solvent is in the polyester laminate right through the fairing job and paint work!

Back to your question... To a certain extent, print through happens because the different products cure at a different rate, and shrink as they post cure with temperature cycles, at different percentages. Ideally, in fairing you are working under direct sunshine on the hottest days the boat will experience, and you can give it time to sit up for a few weeks, and come back later before putting the final effort (220 on to 320 sanding) as the thickest places of putty or primer still move as they are curing.

To fix what you have, you would be well served to paint it a dark color and build a bank of heat lamps to hold the surface to 150 or 160 degrees for 12-18 hours. Then scuff the LPU paint, if it is compatible and well adhered and apply a primer right over it rather than get overly aggressive sanding it off and lose the slick/fair surface you already have... even if you can see the ripple... don't sand off the high spots, till the low spots are filled and everything will stay straight.

Hopefully that helped you with your materials choice...

Zach

[boatsnh]

Thanks Zach!

I had read the disclaimer RE: west system & spoke with the supplier, their thoughts were that "final fairing" was what the 410 was made for....Live & learn. I think I'll only use "harder" fillers that have less issues with the environment/sun, ect in the future. I've always had decent results with Phenolic fillers, cabosil & glass microbaloons...I was looking to save some sanding effort....Bad idea. Now I use longboards, & Festool sanders...Better results, same amount of time, perhaps.

The cabin sides are Oyster White....I had not thought to use a high build primer.....The epoxy/glass is holding on and looks 100%. The paint is also 100%....So your idea of "scuffing" over the paint and using an epoxy primer to fill the weave ought to do the trick - and save me a ton of filling/shaping/sanding. I'll have to see what hi-build primer likes to roll on, since I have yet to get the air set up to spray.

I sort of suspected that the "print-thru" was some post cure thing....I Did the repair in a fairly small time window 4 years ago -- so, the epoxies are well cured now since the Boat sits under a white tarp on conduit frames. On a hot summer's day it's warm up there.

The cabin top area I've repaired is fair & has sat since the end of July, 2011. I'm hoping to get the final prime/fair done early in the spring on a warm day & let it sit for 6 weeks prior to final paint.

I'll do the same on the deck repairs come spring - I suspect that the weather will not cooperate for any epoxy work now that winter is on the way here in Central New Hampshire.

I'll chase down the link you provided & grab a gallon kit to try....Non-sag is a good thing since I've got to do much of the cockpit vertical areas to blend into all the other stuff I've got apart.

I'm pretty much going to have every horizontal surface on the boat re-done with glass/epoxy when this "little" project is over...Amazing how a "little" project seems to get bigger & bigger!

Easier & faster with predictable results is a good thing!
Thanks for your insight.
Mike