Monday, January 20, 2014

Stripping and Fairing

I’ve made good progress on the canoe over the past few weeks.  After the strong back and stations are set up it’s time to start stripping the hull.  The first strip is the most important and will eventually become the sheer line.  The strip is stapled to the center station and allowed to curve, down, naturally at the ends and is then stapled in place at the ends.  The sheer strip is then stapled in place on the other side of the canoe using a four foot level to match its location with the first strip.  Again these are the two most important strips, if they do not describe a smooth curve, any abrupt angles will be transferred to the rest of the strips that come next and the canoe will not have smooth, graceful, lines.  So after spending a good deal of time looking at the sheer strips from every angle possible, and even having my girl friend (Zoe) look at them I was satisfied with their placement.  Now the fun part can begins.

Up to this point the process of building the canoe has just been setting up.  Now with each strip added the boat truly begins to take shape.  The process of stripping a hull is quite simple, just run a bead of glue in the cove of the previous strip, set the next strip in place, making sure it’s fully seated in the cove of the previous strip and staple in place.  Always work from amidships toward the ends of the boat.  In an effort to somewhat book match the strips on each side of the hull I would glue two strips in place, trim the overhang on the ends then move to the other side and add two strips there.  Moving back and forth from side to side keeps any tensions that may build due to the twisting, gluing, and stapling of the wooden strips distributed evenly throughout the hull. 

Progress slows once the bilge is reached; at this point the cedar strips are forced into compound curves as well as twisted vertical to align with the inner stems.  It can be tough to get each strip to sit flush against the station.  Also, once the bilge is reached, one side of the bottom is stripped past the center line.  After the glue is allowed to dry a line is drawn along the center and the excess strips are trimmed off. This center line is then planed flush and true.  To fill in the other half of the bottom I had some help from Zoe.
Next I turned my attention to the stems, the outer stems have to be fitted and glued in place using epoxy thickened with wood flour.  Originally I wasn’t planning to use screws to attach the outer stems but I was concerned about durability and decided that screws hidden under wooden plugs would be much more durable.

Once the glue was dry I removed all the staples and planed the entire hull to take down the high spots in preparation for rough sanding and fairing the hull.  The entire hull was first rough sanded using 80 grit paper then sanded again using 120 grit.  The hull was wetted to raise the grain and sanded again with 120 then 220.

Making sure the sheer strip describes a smooth arc.  Any weird angles here will be transferred to all the strips that follow.

This photos shows the two by two stripping process I used.

Here I'm approaching the bilge where the strip at the center of station begins to turn to create the flat bottom of the hull.  At the stem the strip must be twisted vertical to match the inner stem.

Another view of the sheer line.

The above sequence shows the process of stripping the bottom.


The outer stem is held on with ratchet straps while the thickened epoxy cures.

The outer stem is then shaped.

I used a hand plane to shave down the high spots.

Wooden plugs hide the screw heads.

I wetted the hull to raise the grain and sanded with 220 grit sand paper three times.

Next step, fibreglass.

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