Exterior glassed plywood + fairing compound

[Paulus]

The sides of my cabin are glass covered plywood and the PO, or his yard, used fairing compound to smoothen the sides before applying topsides paint...

The paint + fairing compound is now "shattering" and there are major cracks - compound is lifting all over the place - without any clear cause, i.e. stress points or flex points...

Is there something I should know (not to do) in order to fix it right? I chipped away all the loose stuff on one side down to what looks like glass clotch and am filling the failed areas back in with fairing compound, then sanding it smooth I must say, I am getting really nice results, but it seems to me that I may be making the same mistake the PO did...

Unless... he did not use fairing compund, of course...

The stuff cracking and lifting has a yellowish tint to it - what I am putting on is two-part marine fairing compound - bright white...

Any and all comments/suggestions welcome....

[Rachel]

A couple of possibilities I can think of in regards to the previous job:

1) Some sort of polyester/Bondo type fairing compound was used. As I understand it, this can absorb moisture and then fail. Also, I would imagine that the poorer secondary bonding capability of polyester resin would also apply to polyester fairing compounds.

2) If the cabin glassing job was done with epoxy resin, it's possible the amine blush was not properly removed between the glassing and the fairing.

If I had to guess, I would go with #1

If I were fairing the cabinsides now, and presuming that all the glasswork is sound (no de-bonding, etc.), I would be sanding and prepping for a good secondary bond and then using thickened epoxy fairing compound. (You mention using "two-part marine fairing compound" but I can't tell what kind you are using from that description.)

One other note is that vinylester does also have good secondary bonding characteristics, I think, perhaps similar to epoxy. I have somewhat lost track of that as I just happen to despise the smell, so I don't use it anymore.

Rachel

[Paulus]

Thanks Rachel... now I have to go check what kind of fairing compound I bought.... Since I bought it at the Marine store at the yard, one would hope it's the "right stuff"...

About the moisture - would polyester/Bondo type compound still "see" moisture when covered with topsides paint?

[Rachel]

About the moisture - would polyester/Bondo type compound still "see" moisture when covered with topsides paint?

I would think so, because most paints that people would use on a cabin top aren't water/vapor proof, I don't believe.

I hope someone else will chime in here, as I have not used polyester/Bondo type fairing compounds myself, but I have often heard that they will tend to absorb moisture and fail. It's possible that is a sort of "wives' tale" though, and the failure(s) might be more related to the relatively poor secondary bonding characteristics of polyester in general.

It will be interesting to see what you've got. Maybe 3M Premium Marine Filler? If I remember correctly, that is vinylester based, which should be much better than a polyester-based product (presuming the underlying surface is sound and properly prepped).

Rachel

[ILikeRust]

I agree with Rachel - sounds like somebody probably used Bondo or something similar.

[Paulus]

Okay - update: The filler I bought is made by Evercoat and is Polyester based.



According to the PO it should not matter because the parts of the cabin that are covered with glass mat also was soaked with polyester resin.

So in a nutshell, I have (mostly) marine plywood, (mostly) covered with glass cloth, soaked with polyester resin, then faired with (likely) ployester based filler... Apparently this was all done between 10 and 15 years ago and perhaps it is not all that unusual to have it need some re-touching and re-painting.

Since the new fairing is already on there and rough sanded,



I know... the teak eyebrow is next...

I am planning on finishing it up with a few coats of primer/filler paint, followed by two coats of Interlux Topsides... Hopefully this too will last 10 to 15 years before it need to be re-done.

Thoughts?

[Vark]

I believe Formula 27 is basically Bondo which is talc mixed with polyester resin. I've used Bondo on a work boat of mine which was used daily for many years without any problems of water absorption. I think Formula 27 will be fine on a vertical surface but I would avoid using it where water stands for any length of time. 3M makes a filler / fairing product that is made from vinyl-ester resin mixed with micro-balloons which is superior to Formula 27 but more costly but less likely to absorb water on a horizontal surface. Then again there is always epoxy resin with micro-balloons which is also an excellent filler / fairing compound that is highly resistant to water absorption.
You may get another 10 - 15 years of service out of these products if you keep them painted but I don't think you'll get more than 3 years of service out of Topside paint on a horizontal surface so keep an eye on it and don't let the paint deteriorate to the point where the filler is exposed to the elements.

[Paulus]

I believe Formula 27 is basically Bondo which is talc mixed with polyester resin. I've used Bondo on a work boat of mine which was used daily for many years without any problems of water absorption. I think Formula 27 will be fine on a vertical surface but I would avoid using it where water stands for any length of time. 3M makes a filler / fairing product that is made from vinyl-ester resin mixed with micro-balloons which is superior to Formula 27 but more costly but less likely to absorb water on a horizontal surface. Then again there is always epoxy resin with micro-balloons which is also an excellent filler / fairing compound that is highly resistant to water absorption.
You may get another 10 - 15 years of service out of these products if you keep them painted but I don't think you'll get more than 3 years of service out of Topside paint on a horizontal surface so keep an eye on it and don't let the paint deteriorate to the point where the filler is exposed to the elements.

That's What I am hoping for - good point about the vertical suface...

Regarding th Topsides Paint - since I didn't apply any yet, should I go for two part epoxy paint ?

[Vark]

--Paulus,

I have yet to see a 2 part epoxy paint that flows and flattens well, usually primers are 2 part epoxy which have to be sanded smooth regardless of whether they're sprayed ,brushed or rolled on. I've had good luck with Epifanes 2 part paint but you can't apply it over most 1 part paint . There are ways of determining what type of paint is already on the boat and if it's compatible with the particular 2 part paint you're considering, info can be found online. Two part paint can be applied over good, un-crazed gel coat but it has to cleaned well with a solvent to remove any wax present . DON"T just sand a surface without cleaning it first because you'll only push contaminates deeper into that surface.
I suggest you research the subject further to avoid the many pitfalls.

--Vark

[Paulus]

One more question - since most all glass boats have shiny hulls (sides) but eggshell topsides (decks) would one not want to duplicate this with plywood decks and cabin?

I just primed the cabin sides and have taken a liking to the eggshell look....

Any opinions on why the preferred topsides paints seem to be high gloss?

[Vark]

Most fiberglass boats start their lives with shinny gel-coated topsides which are waxed to get that shine, if left un-waxed it soon oxidizes, deteriorates and shows scum and rust marks so it's wise to keep gel-coat waxed. Shinny paint has it's advantages as well.
Deck are painted or gel-coated light colors to reflect sun light thus keeping the deck cool. A dark deck is hot to walk on and heats the interior making it unbearable on hot days.

[Rachel]

One more question - since most all glass boats have shiny hulls (sides) but eggshell topsides (decks) would one not want to duplicate this with plywood decks and cabin?

In my experience, most fiberglass boats do originally have deck gelcoat that is just as shiny as the topsides* gelcoat, but it's just that the decks oxidize much more/sooner due to being horizontal, so they seem more "velvet" textured. When they are buffed/compounded they get just as shiny as when they were new. Of course this is more obvious in the deck smooth areas than in the non-skid areas.

I kind of like the more old-fashioned all-over non-skid look, aesthetically. I have not had a fiberglass boat that was that way though (only wood/canvas), so I don't know if I would miss the smooth waterways (very well might do).

Shiny might be easier to keep clean, but if you prefer semi-gloss or satin they are valid options, I think.

Any opinions on why the preferred topsides paints seem to be high gloss?

I have often thought about this, since a wooden boat can have obvious (albeit tidy and minimal) brush stroke lines in the topsides and still look great, whereas on a fiberglass boat... not so much. I think it might be because of a desire to have each material look its "best" and be true to itself, so to speak. So with wood, knowing there is grain underneath is okay (to a certain extent obviously not taken to extremes) and being able to tell it's wood, looks good even if it is not super shiny and mirror like. With fiberglass, the "true to itself best" seems to be very glossy. After all, it's "glass." Maybe it's kind of how broken in leather looks as good or better than new leather, but "broken in" plastic things just look... broken. I don't know; I'm just thinking out loud on a subject I've mused to myself about in the past.

CJ and Laura did paint their classic plastic Meridian with a two-part LPU that they purposely made less glossy (more of a semi-gloss), and it does look great, but I suspect most people would still prefer the very shiny "Awlgrip look" as a first choice.

Rachel

*sides of hull above water line.

[Hirilondë]

.............Any opinions on why the preferred topsides paints seem to be high gloss?

It seems that almost everyone is infatuated with glare in your face shiny boats. Next boat I build or the next time I paint my Renegade I am going to use System 3 LPU with a semi-gloss finish. Semi-gloss is much more forgiving of abuse over the long haul and I think it looks just great. Horizontal surfaces are much more pleasant if egg-shell or even flat because of the resistance to glare.

Use what pleases you, don't let that others insist on high gloss affect your choice.

[Rachel]

1- The "Gloss" or let's just say "Bling in a can" is only for those around us so they can tell us how great our boat looks? Pump up our egos...
-or-
2- It helps justify the gazillion dollars we put out for a new paint job?
-or-
3- It will visually give your boat an additional 1.786 knots on race day?

I don't know, Northstar - that sounds a bit negative. I think some people really like glossy fiberglass, and why shouldn't they? I'm not saying everyone should have an Awlgrip-type paint job their boat, but on the other hand, it's a long-lasting relatively durable coating, so for those who like shine it seems like a reasonable path to take. I don't think everyone who makes that choice is shallow or uninformed (although sure, some may be).

To each their own, of course. There is a wide range of options that *aren't* super glossy and those are also completely viable, in my opinion. I find that I like many different looks on boats, as long as they are somewhat ship-shape and tidy (whether that be a flat-grey industrial workboat look, a super shiny sleek look, a boat with neatly painted "brightwork," or something in between).

Rachel

[Rachel]

Glenn,

Guess that dry wit went :whoooosh:

You Awlgripped inside too? Wow, nice shiny easy to clean surfaces.

I had read at one point that it's best to use base cleaners (as opposed to acidic ones, like the vinegar that is often used) to keep mildew at bay*, and the same article said that two-part paints were necessary to stand up to base cleaners. I have not checked any further on that, but still, hard/smooth/shiny alone gives you a good head start.

I had some inside lockers that were nicely sanded, smoothed, and painted with Brightsides (one part alkyd) and even they were such a dream to keep clean compared to any rougher/matter surfaces (especially in hot/humid locales).

Rachel

*of course adequate ventilation is also key

[Zach]

Chisel up some of the filler and see if you can lay eyes on sanding scratches on the original layer of polyester glass.

For some reason a lot of polyester glass jobs go together without hardly any sanding.

Also before you spend hundreds of dollars on your fairing filler/primer/top coat try to chisel up some of the polyester mat off the plywood. I've ripped a 50 foot by 7 foot tall piece of polyester cloth off the side of a cabin with just my hands... If it was resin coated, and then glassed the next day without a lot of sanding, your glass may not be well adhered.

Personally if I was going to go through the trouble of fairing a shiny "I can see myself" paint job, I would grind off the glass down to the plywood and glass it with epoxy just so my "15 year" paint job, doesn't have a substrate failure in 5...

I would think long and hard about fairing anything to that level. A flat, or semi-gloss paint is much more forgiving. A high gloss awlgrip job, requires things to be flat and also all the same level. That requires lots of time on new construction, which is what you are doing after you've ground off all the putty on the glass you have now.

How to do it:

Grind off all the existing putty.
Take an aluminum straight edge/6 foot yard stick from the hardware store and warp it wide side, to the cabin side. Hold each end and sight along the top to see if it is a fair curve. If it is fair, mark your low spots. If it isn't fair, tap along the length of the straight edge and anything that doesn't sound back is a high spot. If it is less than an 1/8th of air space on each side of the hollow you'll be ok... Slide your batten fore and aft a few inches at a time and check the length of the cabin.

Mark with a pencil like an elevation map. Mark your high spots, mark your low spots with rings around each at 1/16 or 1/8th inch thicknesses. Sharpies bleed through primer.

Roll on a layer or two of Neat epoxy, meaning with no thickeners just resin and hardener. You can accelerate fast West systems by inducting G5 5 minute epoxy in a pot, and mixing 105/205 in a separate pot and mixing each and combining. (Thanks Tom... West systems tech line guy...)
Mix up a batch of west systems 410, or glass microballoons and use a notched trowel to pull vertically a bunch of ridges. Use the smallest ridges.
Take a piece of 1/2 inch plywood ripped to the width of a piece of sticky backed inline paper. I like to use a piece 3 sheets long, use 36-40 grit E or F weight paper. Do not use production paper, as the grit separates from the paper on the ends before the grit is gone. Cant the board 10-40 degrees and push forward. Longboard fore and aft... DA or Random Orbit sand up and down. On a boat most curves are much harder or tighter radius going fore and aft than they are up and down. It is easier to longboard out a groove that is vertical, as thats the direction your arms are designed to push distances.

Leave no blobs of extra stuff to sand off if you can help it. Try to use the notched spreader to fill in low spots until you are in primer, as it cuts your sanding time in half. You have half the material to remove...
You can use a cheese grater, stanley surform plane, or 18 tpi hack saw blade glued between two pieces of wood pulled perpendicular its length... up and down the grooves you made with the notched trowel.

Use SEM guide coat (its a brand autobody supply shops carry) and spray the surface. When all the ridges are either sanded off, or are flat and even pull more microballoons or 410 vertically with a stiff west systems yellow plastic spreader. Or use a stainless steel sheet rock taping knife... Keep everything pulled tight, or just a hair over full as epoxy does shrink while it cures. If it is going to be a dark color, use glass microballoons or 407, as 410 will sag if it is under a dark blue, black, or red.


Now spray your guide coat again, and sand off with 80 grit. Low spots will show as pancakes of leftover black specks. Mark where the low spot is with a circle in pencil, and sand out each of them Mark the direction that it needs pulling. On compound curves if you pull left to right, you can still have a low spot if the low is a vertical. groove.. sand the low spot with 60 or 80 grit by hand and pull it with 410 or microballoons.

Roll 3 or 4 coats of neat epoxy on everything to fill the sanding scratches. Add a white tint to the epoxy till it is bright white...

Now take some green food coloring and some acetone, or denatured alcohol and swab the cabin side. Block it out with 100 or 120 or 150 grit on a long board. I like a durablock long board... easy to hold, and cheap. Use good sandpaper. 3M red or 3M gold. You should be able to board out around 6 square feet to perfection before tossing the paper, don't be stingy... there is nothing as labor intensive as worn out sandpaper.

Your low spots will be green. Mark them, and sand the green... take a paint brush or acid brush with neat epoxy, and paint on the lows. This is where G5 or accelerated 105/205 is handy.

I personally like to use Awlgrip products, if you are going with a light color your first primer would be a white 545 primer. Interlux Pre-kote is lumpy when rolled, so be warned. Thin it, thin it... thin it. I haven't seen a noticeable difference or improvement between 216 thinner and 333 thinner for rolling use. Use a glasskoter 1/8th nap or candy stripe roller or a hotdog weenie. Stay away from thick nap stuff...

If you put roller stipple on the hull you'll have to sand it out, so don't try to put a lot of thickness with each coat unless you like to sand. Your recoat time depends on how quickly the solvent evaporates. Try to get the stuff thin enough that it runs off the mixing stick without thinking about it. You should be able to roll another coat in 20 minutes at 80, 40 at 70... an hour or so at 60. It is ready, when you can leave a thumb print in the primer, and the ridges of your print stay put. Don't try to cover in one coat, or it'll roll off the sides of the cabin...

Start out with 220 grit if you only have light roller stipple. Buzz everything out. The sanding method is to do a 2x2 foot square, vertical with overlapping passes and then left and right with overlapping passes until it is flat and true. Then move over, and overlap into your last area in randomly... and keep on trucking. You should be able to get around 6 square feet out of a sheet of sandpaper. Don't apply any more pressure than it takes to hold the sander to the hull without it skittering around. Start and stop your sander on the panel. Don't set it on the panel with it running, and don't pick it up until it has stopped.

Hand sand around any and all hardware before you machine sand. I like a small durablock, but a cheapo rubber hand block is 3 bucks instead of 8.

The easy way to get out roller stipple is a black guide coat, and 150-180 grit on a Random Orbital, DA, or Vibrating palm sander. Sand until the black is almost out of the last of the pits, and then switch over to 220/320 and buzz the last till it is perfectly flat.

Make sure there is plenty of air movement around the hull, it needs moving air to let the solvent out of the paint while it is curing... if you are having slow curing, particularly with high humidity paint and add a box fan or 5 to blow along side the hull to move some air.

If you have any pin holes or leftover spots you can mix up some thick primer, in this case it'd be awlquick if doing awlgrip, or prekote with less thinner doing interlux. Roll it over the pin holes, and spread it with a plastic spreader to work it into the pinholes. When that tacks up, roll another thin coat on top. You can also apply evercoat Ultrasmooth (Which is white...) and catalyze it with white hardener and use a razor blade to spread it into the scratches. If there is 1 spot that you missed, use the evercoat... if there are 80 places roll and squeedgee out another coat.

I can't tell you how much faster it is to fair everything smooth and get through the stages of primer if you can spray it... Each coat can be 15 minutes apart, and you can put on a lot of thickness fast. Though, if you are fair you don't need much thickness... just enough to give an even coat of primer to cover the underlying colors and even them out. The recipe above, will yield a white base, before you prime... with a white primer, and topcoat with white paint. It will be hard for you to sand through the primer and hit a red spot of putty, if there isn't any to hit.

Cheers,

Zach

[Paulus]

Wow, Zach - I can feel you passion for doing things "right".

While I agree with everything you say, I have elected to pick the easier method and buy myself some time before the inevitable strip-down and re-do as you suggest. The cracks and flakes have been ground out and re-filled with polyester based fairing compound, sanded smooth and primed... then sanded smooth again and primed again - right now it looks very "acceptable" - at least to me, but I realize it won't cut muster for many folks roaming these halls.

This also relates to my other question about eggshell type paints - with the final coat of primer put on late yesterday - which has an eggshell finish to it - it actually looks really, really good...

This pic was taken Wednesday after the first coat of primer, which was sanded down yesterday and then re-primed (no pic)



As regards imperfections, I use a large wet/honing stone (covered with 3M sandpaper) as a sanding block, which helps to get and keep the surface flat. I fill voids and sand down bumps.

[Zach]

Looks great! You are a smart to go sailing instead of dust making.

Zach

[Paulus]

And now, for you perfectionists out there, the ultimate topside gloss...



Drool away...