Dutchman repair sequence

Repairing a damaged area on a spar on my CLC boat has required a Dutchman.  I have cut out the damaged area and glued a new piece of wood in the gap with thickened epoxy.  Now I need to apply several coats of unthickened epoxy to the new wood before sanding and varnishing the repaired area (and the rest of the spar at the same time).

My question involves managing the evolving "epoxy-varnish interface."  I am hoping to avoid sanding off the varnish from the entire rest of the spar - and I don't know how I would be certain to remove only varnish while preserved the underying multiple epoxy coats on the otherwise-finished spar if I did so.  Similarly, applying several coats of unthickened epoxy to the new wood of the Dutchman will inevitably involve some epoxy bleeding over onto varnished surfaces.

How careful must I be to keep epoxy and varnish separate and does it make a difference at the Dutchman border?  I know I want all new wood to be effectively sealed with epoxy, and I know I must then sand the epoxy and protect it with multiple coats of varnish.  And I will apply at least the last 1-2 coats of varnish to the entire spar, not just the Dutchman repair.

Thanks for your thoughts and advice.  Stay well.

Mark Nunlist

2 replies:

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RE: Dutchman repair sequence

Epoxy over varnish is bound to disappoint in time, bet avoided whenever possible.

Were I in your shop, having made the repair (dutchman's in place, faired in but not yet coated with unthickened epoxy) I'd remove any and all varnish on the areas adjacent to the repair site by mechanical means (scraping, sanding) until the epoxy underneath's exposed for an inch, maybe two.

(Had I thought about a proper repair sequence before beginning the repair effort I'd have done the varnish removal first - chemical strippers maybe, scraping and sanding certainly - so as to avoid any possible contamination of the fresh wood of the dutchman I'd be soon installing.)

Once dutchman is in place and faired in, coating that with epoxy should be easy enough. Apply the fresh mix to the entire piece right up to and overlapping a little onto that epoxy exposed after your varnish removal efforts to the surrounding area. You'll get a solid mechanical bond to the underlying cured epoxy, vastly better than what you'd have gotten putting epoxy over varnish!

Once your satisfied with epoxifying your repair, lightly sand and varnish the whole spar as you'd already planned. 

RE: Dutchman repair sequence

  Make your repair. Leave space for good epoxy coating around dutchman. Put one "ring" of tape on varnish around the repair area. Put that tape over varnish. Put a second ring of tape inside the first to the epoxy area but still on epoxy/old. Put new epoxy in middle. Remove inside ring, sandedge smooth. Then remove outside and varnish all. 

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