Epoxied Mat over Polyester Hull

[Benz]

Originally Posted by expozen

CSM. I suppose mat could be confused with bi-axial mat (which shouldn’t contain binders because it’s stitched together?). Sorry for the confusion. But elsewhere in this thread I mentioned that I did the same work but used two layers of 5.6 oz cloth instead and had the same result. The CSM was most certainly wetted out throughly. So unless the binders effect the chemical reaction of the epoxy I’m unsure if it would effect the bonding. This isn’t a curing issue. The epoxy has cured hard in the time it’s rated for at the specified temp. The issue is the bonding. I guess the best would be to clean the area again, and then sand with a courser grit (36?). Is there a grit that is too rough? I’m hesitant to get too crazy with the sanding because half of the area is exposed roving, and sanding it means possibly sanding into the glass fibers of the roving. Which seems like a bad idea.

Do not be afraid to grind into the roving. 24 or 36 grit--the rougher the better. Lazyness in grinding is one of the biggest pitfalls of glasswork. Then wipe with acetone. This will clean the area and also remove moisture. Be sure to hotcoat the surface with epoxy before putting glass on it. Get your glass good and wet. Make sure the peel ply gets thoroughly soaked and pushed down tight. A squeegee helps. Good luck.
Sometimes my pumps malfunction, and I find I do better with a scale I got at Harbor Waste. Weigh the amount of resin you think you want, multiply times 1.2 (for West) and add hardener until it weighs that much. Way more reliable than pumps.

[Spot]

Originally Posted by Cadence

I went back and read your original post. I'd give you dollars to donuts that that 50 degree hull temp. is the cause of the bonding problem.

Yes, try a couple laminations at room/lab temp and low humidity.
If those turn out solid then the epoxy and reinforcements can be tested as good and the focus can shift to the conditions inside the hull. I would let them sit overnight before doing a peel test just in case gelling to full cure is going slower than anticipated.

If they don't turn out...you'll have other things to check.

[KP44]

Epoxy does not meld into vinyl ester hull but bonds to the hull. The only reason to not bond is a surface that was not clean. It is possible the hull is saturated with water and no amount of sanding will give a clean surface. Sanding is the normal way to prep for epoxy and a small amount of dust left after vacuuming should just wet-out and become part of the epoxy / mat layer.
I have pulled apart epoxy "repairs" that stayed in place for years but were nothing but epoxy bonded to paint. Grabbing an edge, the epoxy patch and paint came off in one piece.

[Island Time O25]

Originally Posted by Happydrv

Another example of bad forum advice. This from West System:

I don't know where you got that quote from but hardener will last for years. If left open a long time, it could absorb some moister that could affect the cure. I have added a link to our webpage about shelf life.

https://nam04.safelinks.protection.o...amp;reserved=0

Terry Monville |
Gougeon Brothers, Inc.

My buddy explained the chemistry of the stuff to me. Some of the components in the hardener are highly volatile and will evaporate quickly if left not tightly closed. Perhaps those here with chemical degrees will chime in.

Possibly West uses different type of hardener then my friend was using for 45 years of his boat building career (300+ boats built and about a dozen models of his own design). But I stand by what he said as I can attest to actually noticing the difference when one of my hardener containers was not closed tightly and that one was trash. But that was not a West hardener or resin.

[jimbunyard]

Originally Posted by expozen

I epoxied some mat over the inside of my hull in a small 1’ x 2’ area. When I was cleaning up the masking, I inadvertently caught the edge of my knife underneath the new mat (between mat and hull) and it started to delaminate from the hull. I used west with fast hardener, 1.5 oz mat, and peel ply over the top. The area is below the waterline and is probably a consistent 50 degrees. It’s been curing for about two days now. The hull surface was preped by removing paint with a wire brush on a drill, than cleaned with acetone, then brushed with a hand wire brush, then cleaned with acetone, then lightly hand sanded with 80 grid, then vacuumed. I have very little experience performing fiberglass work, but I would think that I wouldn’t be able to pull the newly epoxied mat off the hull by just wedging a knife in there. Boats are hard.

Where in the boat is the repair being carried out?

Originally Posted by expozen

The epoxy was measured with the pumps 1:1. I ensured the pumps dispensed the full amount. Both the risen and hardener were preheated in the sun before dispensing. The epoxy was mixed in a paper cup with a west plastic stir stick. It was mixed for at least two minutes. I brushed epoxy into the surface, then laid down the mat, then, wetted out the mat over the top, then laid down a layer of peel ply, then wetted out over the top of peel ply. I used a fin roller throughout the processes. I used a space heater to heat the work for several hours after completed.

This all seems relatively kosher, as long as the epoxy wasn't in the process of catalyzing (or whatever the proper term for epoxy is; crosslinking?) when you applied it.

Originally Posted by expozen

West epoxy.

I already tried the test with two layers of cloth. I was also able to pull the cloth off. I was also able to pull the two layers of cloth apart.

This seems to indicate a materials issue. You're not using old surfboard-construction materials are you?

Originally Posted by expozen

That’s a good idea. I always feel hesitant to do that because I feel like it’s not the responsibility of a vendor to teach me how to fix my boat, especially whenever they have such a breadth of literature available to teach yourself. But I’m feeling pretty stumped on this one.

There is a Gougeon Brothers rep active in this thread (see following). I'm sure he'll be happy to advise.

Originally Posted by Happydrv

Another example of bad forum advice. This from West System:

I don't know where you got that quote from but hardener will last for years. If left open a long time, it could absorb some moister that could affect the cure. I have added a link to our webpage about shelf life.

https://nam04.safelinks.protection.o...amp;reserved=0

Terry Monville |
Gougeon Brothers, Inc.

This certainly agrees with my experience; I've used West hardener that was so old it was black with no noticeable change in cure time or strength.

However, seems like resins from all manufacturers, to one degree or another, have definite shelf lives...

Originally Posted by expozen

CSM. I suppose mat could be confused with bi-axial mat (which shouldn’t contain binders because it’s stitched together?). Sorry for the confusion. But elsewhere in this thread I mentioned that I did the same work but used two layers of 5.6 oz cloth instead and had the same result. The CSM was most certainly wetted out throughly. So unless the binders effect the chemical reaction of the epoxy I’m unsure if it would effect the bonding. This isn’t a curing issue. The epoxy has cured hard in the time it’s rated for at the specified temp. The issue is the bonding. I guess the best would be to clean the area again, and then sand with a courser grit (36?). Is there a grit that is too rough? I’m hesitant to get too crazy with the sanding because half of the area is exposed roving, and sanding it means possibly sanding into the glass fibers of the roving. Which seems like a bad idea.

Which did you use? Chopped strand mat or biaxial? Don't know for sure, but I assume the binders interfere with the effective saturation of the resin into the glass fiber. Been many years, but it seems I remember that certain glass cloths also have, or used to have, the same binders (hence the previous surfboard question), which would present the same problem.

After reviewing the whole tale, seems like the problem may indeed just be preparation, though the reinforcements issue seems equally likely at this point.

If you're glassing over exposed roving, and haven't ground it so the surface is smooth, it is pretty likely that you're just spreading whatever contaminant that is interfering with the bonding around.

Since you've already coated the area with epoxy, future attempts to de-contaminate the area are probably futile, so removal by coarse grinding is likely your most efficient next step.

Don't be afraid to grind enough off the roving to smooth the weave pattern, but don't remove any more than necessary, as this reduces strength and makes the ground area a relative 'soft' spot. Three layers of 6 oz cloth is not the same as one layer of 18 oz roving.

If you're new to using a grinder, 36 grit might be a little coarse; either practice first a little on a pretty hard piece of wood or an old boat, or use a bit less-coarse disc in the beginning.

It may be advantageous to use a two or three step grinding schedule if the surface is/was heavily contaminated (just had this thought; the contamination could be the paint itself); step one, grind off epoxy (50-60 grit), wipe with solvent, step two, grind half way (first half-layer of roving, leaving a pattern of little divots filled with paint [36-40 grit]) wash with solvent, step three grind away little divots (if you're brave, 16-36 grit) vacuum, wash with solvent.

By the way, the coarseness of the disc is only relevant to the speed of material removal. The mechanical bond of the epoxy is virtually the same whether one uses 16 or 80 grit discs. (Though the finish provided by the less-coarse discs may [because it has more bonding surface-area] provide a marginally stronger bond/unit area)

Let dry. If the substrate moisture content is low, the reinforcement materials are compatible with the epoxy resin you're using, and the epoxy is hardening in the appropriate time frame, adhesion should no longer be a problem.

[boatnerd]

Yes, old epoxy exposed to moisture or stored with other reactive chemicals goes bad, west included. Ive found it best to take off the pumps when storing for long periods and start with new when they get funky. .Using mat w/ epoxy resin is a common diy error. .When in doubt, alway do test batches/layups before working with unfamiliar or old materials. Not much fun cleaning up an uncured mess. Ask me how i know. . Also, not all fiberglass cloth is the same. What looks exactly alike can actually wet out and work quite differently. In the end it pays to not cheap out on materials. Ask what the local fiberglass pros recommend (take forum advice with a grain of salt). .Many diy sailers are often too frugal when it comes to spending on the proper materials for a job. Fiberglass work is much like cooking, always good to start with the best ingredients and follow the recipe before getting creative.

[s/v Jedi]

So here are the possibilities:

- surface was not dry enough
- surface was contaminated
- condensation formed
- a propane or diesel heater was used

With the two pieces of cloth delaminating, while the epoxy cures hard, I would guess it was the heater but if that was an electric heater, it must have been moisture.

Yes I think you prep should have been grinding and sanding with 60-80 grit maximum instead of wire wheeling but two layers of cloth should not come apart.

[Spot]

Originally Posted by jimbunyard

This seems to indicate a materials issue. You're not using old surfboard-construction materials are you?...

JB, In regular plain weave 4 and 6 oz cloths I have seen no issues with 'surfboard' cloth or epoxy, regardless of the brand of epoxy or the cloth's treatment, be it silane or volan. The cloth that vexes me is the coarser stuff 7-8oz gotten online without a pedigree. Some of that has struggles wetting out under normal conditions, even with polyester resin. I call it 'boat cloth'...

[Boatyarddog]

Originally Posted by expozen

I epoxied some mat over the inside of my hull in a small 1’ x 2’ area. When I was cleaning up the masking, I inadvertently caught the edge of my knife underneath the new mat (between mat and hull) and it started to delaminate from the hull. I used west with fast hardener, 1.5 oz mat, and peel ply over the top. The area is below the waterline and is probably a consistent 50 degrees. It’s been curing for about two days now. The hull surface was preped by removing paint with a wire brush on a drill, than cleaned with acetone, then brushed with a hand wire brush, then cleaned with acetone, then lightly hand sanded with 80 grid, then vacuumed. I have very little experience performing fiberglass work, but I would think that I wouldn’t be able to pull the newly epoxied mat off the hull by just wedging a knife in there. Boats are hard.

If it's green epoxy you'd be able to wedge it easily.
Epoxies needs cure time and heat to accelerate its hardening.
If you give time to cure and do a good Prep it's fine and VERY strong.
Clean the area well, then grind with 60 or less grit. Wash and wipe down with acetone and clean rags. Give it a week or so and keep it warm.
SV Cloud Duster

[Disailor]

Free grinding pads at floor refinishing shops. Their 24/36 pads get gummed at the edges & get thrown out. I used metal shears to trim away the gummed areas. Good to go!

[s/v Jedi]

Originally Posted by Disailor

Free grinding pads at floor refinishing shops. Their 24/36 pads get gummed at the edges & get thrown out. I used metal shears to trim away the gummed areas. Good to go!

[svtrio]

s/v Jedi has provided a good list of potential causes for your bonding problems.

I am puzzled that your actions thus far haven’t resolved what seems a contamination problem.

I’m going to add another one to Jedi’s list and I’ve included the details from West’s user manual, which might be very helpful to you especially if you reapply epoxy to previous epoxies.

Water - not acetone - is used to remove a wax like blush created during the epoxy curing process. After curing, this blush will prevent new applications of epoxy (and paint too) from bonding.

Depending on environmental conditions, this blush can be tenacious. If water beads on the cured epoxy surface, that signals blush. When the water sheets off, the blush is absent.

I’ve been using West System Epoxy for more than 35 years, and in the interest of full disclosure, I’ve been selling it as a West Marine associate for 11 years.

I know firsthand of several debonding incidents (including my own)with West System Epoxy. All of them were the result of various user error errors.

I’ve relied on the excellent advice of the staff at their headquarters. They are very helpful and have plenty of experience in helping DIYs to experts. Give them a telephone call: 866-937-8797 M-F. 9-5 ET.
They also provide all their manuals for free online.

I believe the mystery will be resolved because you haven’t given up.

Roger

Cured epoxy

Unless you’re using WEST SYSTEM’s blush-free 207 Special Clear Hardener, amine blush may appear as a wax-like film on cured epoxy surfaces. It is a by-product of the curing process and may be more noticeable in cool, moist conditions. Amine blush can clog sandpaper and inhibit subsequent bonding, but this inert substance can easily be removed.

To remove the blush, wash the surface with clean water (not solvent) and an abrasive pad, such as Scotch-brite(TM) 7447 General Purpose Hand Pads. Dry the surface with paper towels to remove the dissolved blush before it dries on the surface. Sand any remaining glossy areas with 80-grit sandpaper. Wet-sanding the epoxy will also remove the amine blush. If a release fabric is applied over the surface of fresh epoxy, amine blush will be removed when the release fabric is peeled from the cured epoxy and no additional sanding is required.

Epoxy surfaces that have not fully cured may be bonded to or coated with epoxy without washing or sanding. Before applying coatings other than epoxy (paints, bottom paints, varnishes, gelcoats, etc.), allow epoxy surfaces to cure fully, then wash and sand.