New Tool Eliminates Noxious Epoxy Sanding Dust


LOVES Wooden Canoes
think the worst job in building a cedarstrip canoe is dry sanding the epoxy coating on the hull exterior to get a smooth, fair, ripple-free surface in preparation for brushing on spar varnish or spraying 2-part polyurethane clearcoat. So I've switched to wet sanding the epoxy on my hull exteriors and found the process safer, faster, and cleaner. Now a new tool speeds up that process and produces a perfectly fair, ripple-free hull.

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Auto parts stores have a 1/3 sheet flexible sander used in body shops that's perfect for wet sanding epoxy on canoes. The sanders cost about five bucks.

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By pushing on the handles, the sander conforms perfectly to all of the various curves of a hull. You can use up-and-down strokes, diagonal strokes, longitudinal strokes and if you keep pushing, it always conforms to the hull. For the final pass, I hold the sander diagonally to the curve of the hull and move the sander the same direction as the strips.

I start with 120 grit wet/dry 3M Sandblaster paper and only use 2-3 of the 1/3 strip pieces on one half of the hull. I can't explain why wet sanding makes sandpaper last so long, but it does. I keep an ice cream pail of water with a few drops of dishwater detergent on the hull so it's always handy to wet sections of the hull and to sponge off the wet slurry once a section is sanded.

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If your starting surface is particularly rough with runs and drips because you didn't use the brushing techniquesTed Moores details in Canoecraft with warmed epoxy in small batches so it flows out well, you may have to begin with 80 grit and switch to 120 when the worst of the boogles are gone.

Expect to have a couple gallons of liquid on the shop floor when done, so plan for a way to handle that.

Depending on which auto parts store you buy from, the commercial sander you get may be too stiff to comfortably curve it enough so the sandpaper contacts the hull along the entire sander. If you can't find a store with a more flexible one, you can make your own from a piece of 9" x 2-3/4" thin plywood cut from an old hollow-core door, two 1x1s and two handles made from 3/4" dowels. Cut the plywood piece so the 9" dimension is cross grain so it will bend the best. If you cut the piece with the grain, some plywoods, particularly luan bend poorly and may break when you try to conform it to a tight curve. I've found oak door-skin plywood the most flexible. Run a long screw through each 2 3/4" 1x1 and into the dowel to hold the handles solidly. You can then glue the 1/1–dowel assembly onto the ends of the plywood with waterproof glue, or you can use screws with the heads countersunk. The sandpaper is held on the sander with duct tape on the ends of the strip and the blocks.

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In practice, you can't use too much water and if the slurry on a section you're sanding starts to get dry and "growls", splash on more water or wipe off the slurry, dribble on more water, and keep sanding. Periodically, dip your sander in the water to clean the paper, and change the water 2-3 times to do one half of a hull.

If all the runs and fisheyes are gone when you finish with the 120 grit, and you've made your final passes inline with the strips so sanding scratches are inline with the strips, congratulations, you'e done. Varnish or clearcoat will fill the scratches and give a perfect surface. I'll sometimes go over the hull lightly a second time with 150 or 220 grit wet/dry paper to eliminate the tiniest of ripples with the "flexible longboard" but that's rarely necessary to get a ripple-free hull.

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Not only does wet sanding with a flexible sander yield a perfectly fair hull with no dips or unfair ripples, it's faster than dry sanding and kinder on the lungs. We don't know the long-term lung hazards of epoxy dust because we've only been sanding epoxy on cedarstrips for a few decades.
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. We don't know the long-term lung hazards of epoxy dust because we've only been sanding epoxy on cedarstrips for a few decades. A few decades down the road, will we see sleazy lawyers–who now seek patients with asbestosis and mesothelioma for tort actions–seeking patients with epoxyosis?

Your post describing your sanding techniques, including the steps you take to control fiberglass and epoxy dust, is of great interest.

However, I am puzzled, and indeed offended, by your characterization as sleazy those tort lawyers who seek redress for those suffering from asbestosis and mesothelioma, and by implication, any lawyers who seek redress for other similar harms.

It is well-established fact that asbestos causes the two conditions you mention. It is well-established that the industrial producers and users of asbestos knew the hazards related to their products, and it is well-established that they did nothing to ameliorate the hazards, and indeed, took steps to hide this knowledge.

If the word sleaze is appropriate, it is better applied to those who, while knowing full well of the dangers of asbestos, hid that knowledge and profited hugely for decades, without taking any steps to provide protection for their employees or those who used their products.

If it were not for lawyers -- government regulatory lawyers and private tort lawyers -- the harm from asbestos would be continuing to this day.

Epoxy is a useful product, as is fiberglass, but they are not completely benign, as you seem to recognize. Anyone who has spent time in these forums or those of WoodenBoat Magazine has certainly read of people who have had allergic reactions to epoxy and have developed apparently chronic allergies (sometimes severe) from using epoxy. I don't know if there are any other health issues related to epoxy, and I don't know if the epoxy industry is aware of any. But I would hazard a guess that the allergy warnings now printed on epoxy packaging are the result of a law suit brought by a tort lawyer -- or at least the fear of such a suit.

Industry generally does not regulate itself with respect to health and safety -- consider the tobacco industry, the pesticide industry, the petroleum industry, and the chemical industries, for a few examples. Consider the need for OSHA regulations, and the state of industrial workplaces before such regulations.

If you were to live next to a service station with leaking gas tanks, or a fabric dying plant emitting foul vapors, or in a house that had chlordane pumped under you basement concrete, you well might consider retaining a lawyer experience in seeking relief for such situations. You are not likely to get any relief from the polluters/poisoners without one. There are lots of good, reputable lawyers out there; there is no need to hire a sleazy one. And if in future decades a harmful condition known as "epoxyosis" is identified and you came to bve suffering from it, and if it is established that the epoxy industry had known about the condition for decades and had taken no steps to protect against it or to warn about it, you might rethink whether the lawyer who might get you some redress should be called sleazy.

(Disclosure -- I am a retired lawyer who spent most of his career in public service, and a significant part of my work involved taking steps against those who violated regulations intended to minimize or eliminate the harms from improper handing of hazardous and toxic materials. As a lawyer working for state agencies, I did not, and could not, bring private tort actions; I did get hazardous situations corrected, compelled installation of proper control measures, and in some matters, obtained significant financial penalties.)
Andy, I agree that my reference to a select group of tort lawyers as sleazy was offensive and I apologize. Apparently, I've read too many John Grisham novels and seen too many offensive solicitations for client-victims on TV. It seems like with the introduction of every new drug or medical device, within a couple years there's a class action tort by lawyers advertising for supposed "victims" of the drug or device in the most brazen and offensive way.

That shouldn't reflect poorly for attorneys working as watchdogs in the public sector, sometimes pro bono. There are gross evils in society that can only be righted by courageous attorneys in courts. The world would be a different place today if not for Thurgood Marshall, Bobby Kennedy, Ralph Nader, etc.

That being said, as canoebuilders, can we get back to discussing the advantages of wet-sanding....?