Friday, August 12

Back to the garboards which require  a rebate to be cut at each end (upper outside edges). This rebate reduces the plank to ½ thickness at the bow and stern; a corresponding rebate is cut on underside of the upper edge of the next plank, so at the stems, there is only one plank thickness, half being contributed by each plank. The rebate width is the same as the plank overlap, that is, 3/4”; it goes 15” back from the stems. The thickness tapers from full dimension at 15” to half thickness at the stem. The work is done with a rabbet plane of sufficient width to cover the 3/4” wide rebate. This is done so only a single plank thickness intersects with the stems and can be faired into them.  Photos of cutting the rebates begin here.

Once the garboard was prepared, we created a pattern for the next plank. Three 8' sections of luan plywood are presented to the hull. The width has to be sufficient to cover the overlap and the mark on the molds indicating the bottom of the next plank. The three sections are maneuvered around to accomplish this on the full length of the boat. The sections were then hot glued, forming a single long pattern with an odd looking shape. The clamped panel was then marked. The garboard line was traced, the station marks for the plank bottom transferred, as was the plank bottom from the stems. The stems were also traced (outside). The #4 face was also indicated. The pattern was removed. The top edge was extended 3/4” to account for the overlap on the garboard plank (this is necessary since we traced the edge of the garboard, and the next plank must overlap by 3/4”. A spiling batten (about 3/4” square and longer than the pattern) is fitted. Nails were placed at the various marks, working from station 4 outward. We then stepped back to see if the curve was “fair”, that is, a graceful curve with no unsightly bulges. Small adjustments were made to the batten placement until the fit was good. It was then traced and the batten removed. Second plank photos can be seen here.

The pattern was then placed on top of a piece of a doubled up 4x8 x3/8” mercanti plywood; we cut both port and starboard planks together, insuring symmetry. . The pattern had to be transferred in three sections to this double piece of plywood. Thought had to be given to most efficiently fit the three sections of the pattern to the single piece of plywood.

One section was traced and a scarfing batten (3” wide strip of luan) was placed perpendicular to the section; this was marked “Under” or “Cut”. As you move from bow to stern, the forward part of the scarf is on top and the aft section underneath. The forward section is marked “Under”, meaning it has to be planed on the bottom, and the corresponding scarf on the next section is marked “Cut” since it will have wood removed to create the 8:1 sloping scarf. The marking of the scarfs was done on each of the three pieces. Each was marked as to which side of the boat it would be placed and an arrow pointing towards the bow was also drawn. Next, a 3/4” line was drawn around each of the sections to allow for some leeway in the final fitting of the plank to the mold. The three sections were then cut using the 6” circular saw. The two layers were separated and layed out. Care has to be taken to mark the parts cut from the bottom layer of plywood, and indicating their proper orientation. The scarf areas are drawn in and Under and Over noted on each scarf. This is a step that an error can easily be made and a scarf cut incorrectly.

Next we took the three pieces representing the plank on one side of the boat. Each piece was place on the workbench with the edge to be scarf aligned with the bench. A combination of power planers and hand planes were used used to cut the scarfs. Brian cut a very nice scarf using only his hand plane. The plank is then offered up to the boat. The spiling process was then repeated, again transferring marks from the stems, including their outline (lower edge), plank marks on the molds, station #4 and the edge of the garboard.

We then removed the plank a faired it using the batten. Again, the 3/4” overlap on the upper edge of the plank (note: upper refers to the orientation as we're looking at the boat, which is upside down, so the “upper” edge eventually becomes the bottom edge when the boat is righted). The rebate is created on the inner, upper edge of the plank ends so it will fit into the rebate cut earlier on the garboard plank.

The bevelled edge of the garboard is wetted with un-thickened epoxy. Then thickened epoxy is applied along the edges. The plank is then positioned (from #4 outward), and clamped and screwed where necessary (temporary screws).  The process is then repeated with the blanks for the other side of the boat. The rebates on the lower outside edge of the planks are cut after it is on the boat.

Using the same process, we created blanks for the third planks. The only difference was that when we scarfed them, instead of screwing them to the bench (with plastic protective sheets), we used a 2x3 piece of stock across the joint and clamped to both sides of the work bench.

We finished the first week by assembling starting assembly of the rudder, centerboard, centerboard box etc. as shown here.

End of Day, and Week Progress!

Week one was informative and fun. We have a great instructor and a diverse team with good chemistry.

All photos of the Ness Yawl 2011 class may be viewed at: http://www.flickr.com/photos/21597525@N00/collections/72157627358772597/