Tips in sanding polyester resin/ paper gumming up

[Scott]

I have put two layers of matt and polyester resin on the topsides of my Triton and now am having a hard time getting it sanded as my 24 grit paper keeps getting gummed up with the wax. Any tips on how I can avoid this would be appreciated. Never use it again, will definitely be doing the deck with epoxy.
Scott Triton 3227

[Tallystick]

It's not cured completely. Assuming enough hardener was used, it probably got dew on it before it fully cured. It will eventually cure, but it needs time and heat will speed it up. You might try putting a black trash bag over it to absorb the heat on a sunny day.

[Scott]

It has to be cured completely, I put it on last summer. it's the wax that's gumming me up. The layer of wax that comes to the surface to allow the resin to cure. There has to be a better sanding technique than I am using. I wonder if going over it with a wire wheel on my drill first might take the wax off??

[Tallystick]

I've used wire wheels on a drill or angle grinder to remove paint from fiberglass and it doesn't damage the glass as long as you aren't to aggressive. Angle grinder with a fine wire cup brush works best for that. Might work for the wax, or may just spread it around. What about removing the wax with a solvent like naptha or mineral spirits?

[Scott]

I wonder if anyone might respond to the suggestion on using naptha or mineral spiris? has anybody tried this method?
Scott

[CharlieJ]

How about giving TSP, a brush and water a try? It's a wax- Tsp will cut the wax.

Like amine blush with epoxy- pretty simple to get rid of- soap and water.

[danielguiod]

A product called "Bottom Prep" is used to remove the wax from finishing resin. Sanding just spreads it around and interferes with the topcoat bond.

[Zach]

Gumming from polyester is normally from not enough wax, or using laminating resin instead of finishing resin. Laminating resin does not have the wax.

Depending on how old the resin was you were using, the wax could have floated out of the container leaving you with laminating resin, particularly if some places are easy to grind and others clog the paper.

Also if you used old MEKP hardener, the ratio's could have been off as its strength diminishes with age and UV exposure.

I would try three things... Wash it first with TSP, or ammonia/water.

If that works, cool...

If not, spray or brush a coat of PVA Mold Release agent on the surface, which will inhibit air from getting to the surface. Leave it to sit for a day or two and try again. PVA is water soluable. I normally spray PVA over gelcoat repairs and polyester projects instead of using finishing resin. A gallon runs around 20 bucks, a pint is almost the same price from the bondo brand at west marine and paint stores. If you can't find it locally give me a shout...

If that works, your resin was laminating resin.

If that doesn't work... You can get a spray bottle, and put MEKP hardener in it and mist over the surface of the work. To say this is flammable, is an understatement so no smoking, bare bulbs or electric fans and motors. Polyester will accept hardener while it is gummy, and kick start the chemical reaction through the laminate. Gelcoat is classic for doing this as most of them take nearly twice the % but it works on laminating resin too.

If the last one works, cool!

If you want it painted and have it look decent, but not perfect... rather than gelcoated:

I wouldn't switch over to epoxy primers or fillers, unless I ground off all the polyester that is questionable. No sense putting that much expense into something that may continue to cure and move around or leach solvent. I'd stick with polyester. Duratech makes some excellent, relatively inexpensive polyester primers that are very easy to work with. Their surfacing primer will let you build wet on wet to 15 mils, which is sprayed is more than 2 quarts on a 4x8ft surface. You can roll it, not much fun as it gels up so fast. You can go from 40 grit, spray to cover it... Sand out with 220/320 grit, hand block with 800 grit... and polish with a machine buffer. Duratech also has a sprayable fairing compound that looks like ground up smurfs with a strange crust you mix back in after you open the can. You can spray wet on wet to 5mm thick. It sands like whipped cream.

There are some good car auto body fillers out there, but the marine plug making ones put them to shame when it comes to shrinkage... Look at some of the stuff Adtech makes, some of their fillers are backwards and forwards compatible with epoxy. Not sure exactly how or why, but I have a friend who is a commercial fishing guy. Built him an engine hatch with the above products directly below his net reel, and everything is still intact a year later. I put West Systems 410 on one corner, Duratech's sprayable fairing compound on another. Adtechs P-75 quick fair on the other two. The West systems 410 got mushed... all the others are still intact. (All that applied over West systems epoxy and a layer of biax...)

I wouldn't give somebody a tube of 3M Acryl-White spot putty, nor would I let a tube of red nitro spot putty anywhere on my property...

If you want it gelcoated: Spray it on. Duratech and a few others have gloss additives for gelcoat that makes it much thinner and easier to spray. Normal gelcoat has no properties that make it lay down and wet out together. Some people cut it with a sizeable portion of acetone, but that dramatically increases the likelyhood it will fade out or crack due to shrinakge. If you have any runs or puddles, block them out with 600-800 grit. It takes a minute... but sand just the drip as best as you can. Then you can sand with 1000,1500,2000 and polish with 3M finesse it 2. I like a product called Aquabuff, where you can go from 800 grit to shiny, but it comes in a big bucket that costs a bunch.

If you want perfection, grind it off and go with awlgrip or another LPU...

For gummy stuff I use a 7 inch grinder with 16 grit grinding discs stood up on its edge to dig in to the underlying substrate and spray the gooey stuff elsewhere. Laying the grinder flat on the surface, does pretty work... but gooey stuff just heats up and clogs up.

You can stretch the discs a bit by grinding a piece of wood until the goo gets cleared out of the grit. Also you can get a gum rubber abrasive cleaning stick: http://www.amazon.com/Rockler-Abrasive- ... B001DT5JHG I use these when I get to the 220-320 grit stage of sanding finish primer too, with 3M Gold sandpaper the paper stays sharp through two or three rubs on the rubber stick. 6 bucks saves about a half a box per day.

If it really doesn't cure or get any easier to work with, you can try using a heat gun to soften it up and scrape off the old stuff. Polyester doesn't let loose in the same way epoxy does with heat, but if it never fully cures it does let go of the fiberglass with heat and make it much easier to work with. I've had success using heat guns and propane torches to scorch polyester repairs, letting them cool and then grinding off crispy chunks instead of goo that just spreads around. You can also lay a shop rag on the area and wet it with acetone and let the solvent work in a bit. Sometimes the goo-factor is reduced... Don't mix fire/heat and solvent...

Good luck

Zach

[Scott]

Thanks for all the replys. TSP seems to have done the trick. Did some sanding yesterday with a 7" pad on a mini-grinder until the pad started to come apart. Couldn't stand up to the RPMs. Kept going with a 3000 RPM sander/polisher with the same pad and 24 grit. No question the polyester is cured. Had been thinking of fairing with epoxy fairing compound, but now have more food for thought re the Duritech product. This is all new to me, biggest project I've taken on! Determined to do the best I can do though, the old girl deserves it! I guess I'm just a "Bottom Sanding Grunt" by nature. Anyway looking for pros and cons on Epoxy fairing as opposed to going with the polyester fairing then Gelcoat etc. I will take a couple of pics and see if I can't post them tonight. Zack you look like you are at a similiar stage to myself with the Triton! Have a good one! Scott

[Zach]

Epoxy is much more expensive, and has a longer working time... but also a longer time between sanding. Its very much, sand the whole boat... putty the whole boat. Tomorrow, sand the whole boat... putty the whole boat. Its a bit of a time drag, as some point you have to simply decide it is time to move to the next stage.

Epoxy is much easier to use, but much more expensive to do the same tasks... Polyester shrinks more when wet, and continues to shrink with time. In 5 years both will move a bit, but the polyester will move more.

For cost constrained projects I like Duratech and Adtech... But if it has to look perfect, epoxy is the way to go.

I use Adtech's Epoxy Proseal to provide a base for the epoxy fillers. It is bright white. I sand the surface with 40 grit on an orbital sander, all of it... Then I use denatured alcohol and green food coloring to dye it after it is cured. Sand it off, and your low spots are green.. I try to sand the proseal until 80% or so is white, or just barely showing fiberglass through a white haze. Take a pencil and mark around the green spots, sand the spots till they aren't green. Use a trowel wider than the spot. I try to putty decks from port to starboard not bow to stern unless the low spot is long and narrow.

I put a relatively thin coat on, less than a 1/8th of an inch is helpful not to sand for days. Proseal is much easier to sand the first day or two, and much much harder after a week.

Awlgrip's Hull Guard Extra has similar working characteristics, but doesn't have as high a build thickness.

On small stuff I will mix up a creamy filler of straight cabosil, I've used all the brands and the best I've found is made by the Cabot Corporation, which I believe West System rebrands. Aerosil, and the rest that are not fumed/treated do not mix in to a smooth creamy consistency and have chunks... I use a 2-4 inch chip brush to apply both of these, and a plastic squeedgee to remove the majority to fill the weave. Some large shops use cabosil exclusively, but I like the bright white color of proseal as a guide not to go any farther.

I use three sanding methods... first, I always sand new putty with a random orbital until the low spot I over filled, turns into a high spot I can barely feel. From there I wrap a batten around the surface and verify it is still a high spot. Mark the surface with a pencil everywhere the batten touches. Each time you sand off a pencil line put the batten back on it and mark it again.

I use a 16 inch 3M sanding board with 3M 40 grit and 80 grit production paper to finish taking off the high spot.

I use a 3M marine hookit sanding board with 40 and 80 grit Mirka sand paper to find big holes in flat surfaces. (Battens and straight edges that are not stiff enough for flat surfaces won't show big holes....)

On hull sides only sand with an orbital sander in vertical passes. Never follow the waterline. Go up from the waterline to the toe rail, move over an inch overlapping almost the same path sand back down until the sprayed stipple, roller stipple, or texture from the putty is gone. When it is evenly the same texture, move to the next stripe over. You can do 2x2 foot squares if you are working on an area of the boat larger than you can reach from top to bottom in one pass. Throw away the sandpaper after each 2x2 foot square. Overlap the bottom and top of each pass into unsanded territory to keep from putting a low band around the boat from stopping at the same spot every time. Count out to yourself how many seconds it takes to go from the bottom of the 2 foot square to the top of the two foot square. Don't stop at the top or bottom, just make an arc and go back down an inch over...

Your body can sand with a long board across in a 45 degree pattern... It doesn't do very well sanding straight up and down forcing a board flat to the boat. What you are doing with a 45 degree pattern, is averaging out the high spots left from your vertical random orbiting. This involves holding the board flat to the surface. If the front of the board is at 3:00 hand of a clock, and the other at 9:00, that is cool... but the boats shape will determine what position the board needs to be held. 2:00-8:00, 1:00-7:00... Try to keep it flat to the surface where the board doesn't rock from corner to corner. Go from the top of your reach on the right side, down to the bottom of your reach on your left side. Sand the same track until you have a scratch pattern you can see covering roughly the whole width... If you make 10 passes and move your feet over an inch, do the same thing the whole boat over so that the surface becomes more even. When you get to the end... Turn around and go the other direction, from the top left, to the bottom right. If you have a fair hull the whole thing will have X marks. Anywhere there are not X marks from your sandpaper scratches you have a hole or a high spot ahead/behind it.

I use red rustoleum primer and dust the hull so that dry flecs of primer land on the surface on areas I have questions. Sanding takes the red specs off, but leaves them in the low spots. SEM makes a product called Guide Coat, that you can get from an auto supply house, it is better than cheap primer.

The big marine hookit boards verify what the shorter boards say on small boats and flatten big flat areas, like the bow... cabin top, or under the counter of the stern. Anywhere with a tight outside curve they aren't much good, but they are very handy on big flats to find holes.

Back to epoxy fillers:

Ideally the Proseal will have filled the weave of the fiberglass cloth and fills the 24 grit scratches without having to sand the raw glass smooth. For one it takes away thickness of the substrate and takes away strength. I make certain that the surface is fair before applying it, as stuff stuck in the fiberglass mat or a high bump in the surface needs to be addressed before you start fairing with putty. (before glassing it ideally...)

2 part epoxy fillers: I have tried all of West Systems line of fillers, along with some other brands. For a few years I blended my own out of 25lb bags of microballoons and cabosil with west system. I've used System Three's 2:1 (stinks, short working life... itchy dust) Adtech's 2 part filler (I threw it away...), Proset (sags on vertical fillets) Interlux, Red Hand (Both of these are harder to get, and almost as expensive as the two below... Etc. The only two I use today, are Alexseal's Grey 2 part and Awlgrips pink 2 part.

Both are tough stuff that you can trowel over a heavily abraded surface. I much prefer this over mixing in filler to west system. No blush, always sandable the next day and each layer applied is approximately the same hardness as the next. Dust fillers in epoxy take more time to mix, and if you are not inside a shop wind takes a fair bit of each scoop. You end up mixing to a consistency you know by feel... on a hot day the viscocity of the resin is different and you get a dryer mix to get to the same point. When the resin starts to kick the bottom of the pot gets runny. Runny filler is harder than the dry stuff at the top of the same batch. Etc. Not to say that a lot of boats aren't built with it, and beautiful work isn't done with those type fillers, I just don't use them in my shop because after labor costs they cost more.

I use an array of squeedgees and sheet rock taping knives out to about 18 inches, aluminum bars to around 5 feet, aluminum angle iron as long as needed and 1x1 box tube in lengths up to 21 feet... to spread putty. Basically you have two ways to fill a low spot. One is to use a 6 inch plastic squeedgee and float it out, much higher than it needs to be. Then sand it all off until you don't have a "Shiny spot" that doesn't have scratches from your sandpaper. If you have a lot of low spots, you use a lot of putty just making everything higher than it needs to be.

If you don't sand one spot all the way back down to where it needs to be... the next time you putty you add more around that high spot. The only way to get a perfect surface at that point is to putty the entire surface out to the same height as that high spot. I know folks that don't like sanding, and eventually that is the result. Either that or they spray primer and continually hit the same spots.

The initial glass work makes the putty work go smoothly. The first day of puttying makes or breaks the rest of the paint job. On one hand don't oversand, until you are back to the fiberglass on every coat... But on the other, always make sure that you have sanded your puttied spots until they are smooth to the area around them. Just like with drawing... don't paint outside the lines.

To use a batten (curved surface) or straight edge (Flat surface) you apply the fairing compound to the surface the same way as above... more than needs to go there. Wrap your batten around the surface, and hold even pressure and scrape off the excess. Let that cure. Epoxy shrinks. The thickest spot of the low will be the lowest spot tomorrow. Sand it off with 40-60 grit lightly to remove the shiny smooth-ish texture.

I use a pencil to mark the surface where my batten contacts the surface, rather than marking the low spot at this stage of the game. If I take off my pencil line sanding, I put the batten back against the surface. If it touches everywhere that wasn't a low spot by enough to have needed putty. When I feel the surface with my hand and I'm starting to be pleased, I'll either take my pencil and make 1 inch vertical lines over the whole surface, or mist on a coat of guide coat. You can also use 3M's graphite dust, or West Systems Graphite powder.

I use graphite powder on finish primer before the topcoat goes on to verify the entire surface is sanded, its expensive and dusty to use for the grunt fairing.

If there are air pockets, use a drill and a wire brush to scoop out the air pocket. I cut plastic squeedgees down to an inch or two wide for these, as using a wider trowel on a curve takes more material you have to sand off. You'll learn how to mix and apply putty without working air in to it.... basically don't fold it together trapping air while mixing it. Use a putty knife through the two parts and pull it back and forth. Spread it out on a piece of plywood in a thin layer so it doesn't kick off... Scoop up what you need, and apply it to the surface slow enough that the air gets out of the way. You can loosen up and remove air pockets while the putty is wet by working the putty knife back and forth in the putty, not lifting it out, or moving it through from one side to the other. Just a 1/2 or 3/4 of an inch motion to each side moving a 1/4 or so inch through the pile for each motion.

I don't pull the fillets until both walls are prefect down to the inside of the radius. Big fillets (2 inch+ PVC pipe) are much easier to sand and get straight. Small fillets the wall and deck have to come to a perfect sharp corner that is fair on its own rite... That is the reason most custom and new boats have such large fillets, you can't pick out a straight line through that large a radius. Don't sand the fillets to try to true them up... I use West systems and Cabosil to pull them. Some guys use West Systems 410, so they are very soft and easy to sand. Just sand them enough to take the shine off, fill any lows and sand down any humps and lumps so they are a 2-3 inch wide low. Use a 3-4 inch wide squeedgee to pull through the fillet from one wall to the next. Intersecting corners are impossible to pull all sides at the same time. Pull the two most difficult ones first, let them kick. The next day use a dremel or similar tool to make the actual corner low, and repull the corner from both sides... then pull up the easy fillet.

Outside corners on small stuff... don't sand them either while fairing... Putty them out straight to a sharp square corner and when the two surfaces are close cut them with a router sand enough t scuff them and spray with primer. Example: Toe rails, door openings, and molded in details...

I normally will get the grunt fairing straight with 40 grit, verify with 80 grit on boards. Guide coat and sand the guide coat off with 80 grit on an orbital, then spray a sprayable fairing compound or super high build primer on the surface to make it all one color, sand that with 120-180-220, and either recoat to fill any thin places or switch to a finish primer and top coat.

If you need any materials shoot me a PM and I'll see if I can ship them at a lower cost than you can source locally...

Zach

[Scott]

Thanks for all the input Zach, lots of food for thought on the fairing once i get this polyester/matt sanded off! Here are a couple of pics to show what I am up against.

Here is the starbound side that was pretty well all sanded at the time.

Here is a pic of the starboard side towards the stern where it had yet to be sanded.
On another vein, I have serious chest congestion after having breathed in fiberglass dust and particles all weekend. Apparently my new respirator is not the best. I would like some input as to what others are using for respirators. It's a little scary feeling congested with fiberglass dust/fibers.

[Zach]

Hi Scott,

I use a 3M 7500 Silicone (blue) half mask a lot of the time, when seeing what you are doing is important, long board sanding and general paint work. Heavy grinding, and things I need better eye protection than safety glass can offer... I have a full face mask that is a 3M FF-400, that has a silicone seal, and 6 straps instead of most others with 4.

I wore out two full face 3M 6800's over a few years of daily use, but found out spraying paint that they don't fit tight enough to my face not to leak if I turn my head. 3M makes grey rubber half masks too that are the 6000 series, and they don't do very well day after day, as they don't conform quite well enough not to leak if you turn your head a bit.

I use 3M P100 filters for most grinding, which are pink circles. They are good for 40 hours of use, or when every they clog up... If you start getting dizzy, and your vision starts going in and out on a full face, it is because you are pulling a vacuum breathing and its moving your eyeballs. Keep going, and you start losing steam and getting tired. Suddenly cured, when you take the mask off. Weird, eh!

For paint spraying and anything that I believe is still active, or if I am grinding in a confined space a whole lot of polyster... I use 3M 6001 charcoal cartridges, with the 3M 501 plastic filter retainers, and 3M 5N11 N95 pre-filters. These are good for 24-36 hours of use, with the exception of spraying Awlgrip and other polyurethane paints that contain isocyanate. With those, you only get 6 hours or so. If you smell any solvent fumes, or anything sweet the cartridges have absorbed all they can hold, and you are sucking fumes. Take the cartridges off and put them in a ziplock bag to make your 24-36 hours, working hours... not a countdown from when you open the package.

I don't like spraying anything in confined space without huge air volumes moving by... Ideally you would have an air supplied respirator, but a lot of shops don't. Solvents still effect you, as they displace air... So you still have to be aware, and have fresh air moving by.

To figure out what fits, you need to cover the inlets with your hands. Sometimes this helps to wear gloves. Inhale, does the mask suck up to your face? Stop inhaling, but don't exhale... does it stay where it is or leak down? If it leaks down slowly, you have a small leak but probably are the right size...

Now cover the exhalation port, and exhale normally. Does the mask bulge off your face? If it does, and still leaks down, try tightening or repositioning the straps until it doesn't. I find it is easier to get a good seal with a larger size, a bit tighter, than a smaller size with the silicone masks.

Beards and facial hair don't work, so you have to be clean shaven. Your glasses need to ride high enough on your nose not to interfere, sunglasses or not...

Some folks do pull off a beard by greasing down with vaseline... it does make lunch break interesting...

Zach