Tuesday, August 23, 2011

Week 3 - Bottoms up, Gunwales and Foil blanks

Week 3 started with ripping lengths of cedar, douglas fir, and sapele for parts I would need to get the bottom on the boat, and parts I would need soon thereafter.

I hadn't anticipated starting on the gunwales until week 4, but upon closer review of the instructions, the gunwales should be in place before the bottom is bonded on to help ensure the side panels remain fair while the bottom panels are bonded to the sides.  So I ripped lengths of douglas fir for the gunwales, built a scarfing jig for use with the table saw, and tried a new process for bonding the scarf joints.
In the picture above is the scarfing jig that I put together from scrap parts.  This worked better than how I scarfed the chine logs (roughed out with a circular saw and finished with a bench plane).
Here is the improved process for gluing up the gunwale scarfs.  With the chine scarfs, I just used weights to apply pressure on the joint.  For the gunwale scarfs, I used packing tape covered scrap pieces to support the bottom of the gunwale staves, then drove drywall screws through the gunwale scarf joint and into the scrap blocks underneath.  I used alignment marks while dryfitting to make sure everything stayed aligned in the final glue-up. 

While the gunwale scarf joints were curing, I took some time to rip staves of cedar to glue up for the centerboard and rudder foil blanks.  I also needed hardwood staves for the leading and trailing edges of the foils, so my gorgeous board of sapele had to be cut up.
Here is the board, chalked up for the parts to be made from it.

And what's left after cutting up the sapele.

Here are the rudder and centerboard foil blanks cut to size and dryfitted.  The sapele staves are on the outside, with cedar in the interior.  I also snuck in a stave of douglas fir near the middle for some additional stiffness.
Above is the rudder foil blank being lamenated.  The staves are aligned on a piece of OSB with some straight edges attached.  After applying the epoxy to the staves, the pipe clamps were just snugged up, the weights were applied and then the clamps were tightened up.  Notice the glue-up is set up on some saw horses and not on the floor.  This becomes important later, but I will hold that thought for the proper time.
Here is the centerboard after the epoxy had cured, it still needs to be cleaned up and planed flat before carving into a foil shape.
Speaking of the foil shape, I differed a bit from the plans again and used a pattern that I found on the jwbuilders yahoo group that is dedicated to John Welsford small boat designs.  http://groups.yahoo.com/group/jwbuilders/  I am a big fan of John's designs, and have plans for his patherfinder cruising dinghy.  But I decided to build the Goat first because it will do most of what I expect the pathfinder to do, cost half as much, and could be built in less than a third of the time.  But I digress.
Above is the foil template I used which calculates a foil outline based on a NACA shape using the basic dimensions provided.  It also provides an offset dimension that can be used to create a jig to carve the foil using a router.  The plywood pieces below the template are the beginning parts of the jig.
While the foil laminations and gunwales were curing, I also bonded the bottom panels together using plywood butt blocks.
With the the bottom panels bonded together, I turned my attention to dry attaching the gunwale staves to the boat side panels, turning the boat bottom-side up and beveled the chines and frames to accept the bottom.

Next, the bottom was dryfitted and screwed into place.
And once again, after dryfitting, everything was taken apart, epoxy added back to the joints, and everything screwed back down.
Here is the bottom after bonding, screws removed, and all the edges trimmed flush with the sides.  After filling all the screw holes and fairing and rounding off the edges, it was time to apply fiberglass to the bottom.
Bottom with dry cloth laid out.
And after wetting out with epoxy.
After filling the fiberglass weave, more fairing and sanding, the boat was turned right-side up again.
Wha-la!  we have a boat....sort of.

Assessment at the end of week 3:  I had originally planned to complete the gunwales, knees and foils by the end of week 3.  I've dryfitted the gunwales to the boat, but have yet to build the in-wales, in-wale spacers and knees.  I've laminated up the centerboard and rudder foil blanks, but have not carved them to shape, faired and fiber-glassed them yet.  So I'm about four days behind my original schedule.  I have to think about taking some additional vacation to hold schedule.

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