Building and Adirondack Guideboat-Varnishing-Ugh!

The inside of the hull is finally ready for varnishing.  This is an onerous task for several reasons.  There is much prep work to be done before the first drop of varnish can be applied.  Application of varnish is tricky.  It has to go on just right or it will not justify all the work you put into it.

The prep work involves scraping and sanding the planks to smooth them and bring the laps down to a true feather edge.  I use a scraper with a curved blade and 100 grit sand paper stuck onto a large dowel.  The work goes slowly because of the hindrance caused by the ribs.  The ribs form “bays” about 6″ wide.  They cramp and slow the operation.

Tools used to prepare the inner hull for varnishing.

Tools used to prepare the inner hull for varnishing.

There is a tradition amongst guideboat builders that before applying varnish the wood should receive a mixture of linseed oil and mineral spirits.  Being something of a doubting Thomas I never subscribed to this practice.  It wasn’t clear to me just what this would accomplish.  Hasn’t one hundred years of varnish research eliminated the need for this practice and whatever benefit it might provide?  I asked a friend of mine, Doc Hank about it.  Hank worked for 30 years for DuPont in research on paint technology.  He said it wasn’t obvious to him how linseed oil could be of benefit here.  He also added that linseed oil is not a stable organic compound and degrades rather quickly.

I remove all the dust and shavings using a shop vac and go over the hull with tack cloth to get the wood as free of dust as possible.  It is recommended by the manufacturer that the first coat of varnish be diluted by about 10 percent.  I apply the first two coats of Epifanes wood finish gloss varnish without sanding between coats.  I can do this with Epifanes as long as the second coat is applied within 72 hours.

The bottom board gets varnished first while the hull is upright and the bottom board is  horizontal.  This prevents runs.  Then I tilt the hull and varnish the tilted side so that I can keep as much of it as possible on a horizontal plane.  Again, I am looking to prevent runs.  Then I tilt the hull the opposite way and do the other side.

As I move along to the third and fourth coats it becomes clear why varnishing is such a vexing job.  Varnishing is very unlike painting where you can see a run or a skip (or holiday).  Varnishing is pretty much flying blind. I helps to bring lots of light to bear on the subject.  I use a 500 watt halogen lamp and look at the coated surface from various angles to try to pick up skips and runs.

Here I am applying the third coat of varnish to the hull.

Applying varnish to previously sanded hull.

Applying varnish to previously sanded hull.

I had hoped to get away with four coats of varnish on the inner hull.  But after the fouth coat I just wasn’t happy with the appearance.  It was OK but I couldn’t live with just OK.

So I sanded the hull yet again.  Epifanes recommends 320 grit paper.  It turns out that 3M makes a marvelous grade of 320 grit paper.  They claim it lasts 10 times longer than other sand papers.  I believe them.  It just doesn’t clog or wear out like the others.

3M's new sandpaper.

3M’s new sandpaper.

So here I am using tack cloth after sanding the fourth coat of varnish.

Using tack cloth after the fourth coat of varnish.

Using tack cloth after the fourth coat of varnish.

So the final coat of vanish is applied.  I am happy with the result and glad I put in the extra effort.

Hull after fifth coat of varnish.

Hull after fifth coat of varnish.

The next big hurdle is installing the decks.  This will be a major challenge because things have to fit just so.  Stay tuned.

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One Response to Building and Adirondack Guideboat-Varnishing-Ugh!

  1. beautiful work, Gordon.

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