Dingy Building, Part 1

This is the dingy I decided to build for the Lady J.  It is a 10 foot Nuthatch Pram, designed by Warren Messer.  I chose this design from others that I found at duckworksmagazine.com, an online boating magazine that specializes in amateur built small craft.  Warren provides for free a scale model of this boat that prints on a regular sheet of paper.  After glueing it to card stock, you can cut out the panels and tape them together.  This is essentially how the real boat is built, using a technique called "stitch & glue".

I ordered the plans, which came on line and downloaded them to my computer.  The first step was to make a building platform.  Three sets of saw horses with 10' 2x6s screwed down made a sturdy and level platform.

Building a 10 foot boat from 8 foot plywood requires some extra work.  I had sold my panel stretcher along with my former tools, so I had to lengthen the panels the old fashioned way.  How to add 2 feet to a panel?  For maximum strength and style points, scarfing is the recommended way.  The scarf has to be a 12 to 1 ratio, so for a 1/4 inch panel, I needed 3 inches of scarf.  I placed two full size sheets and two 27 inch panels together, matching good and bad sides, with a 3 inch overlap between each piece.  Everything was held in place with a few drywall screws.  The narrow strip at the top was a guide piece to keep the proper angle.  After sharpening the blade of the plane, I proceeded to shave away the excess wood.

Three hours later, the job was complete.  The lines from the various plies helped keep things in line and even.  I felt like some old world master craftsman.

I think Norm Abrams would be proud of me.  The scarfs were then properly aligned, then glued and clamped together with West System epoxy and allowed to set for two days.  The panels were atop one another, separated by wax paper to keep things from sticking together.

The scarfed panels were then placed on the work table, good side to good side. With marine grade plywood, "bad" is a relative term.  My wood was A/B grade, meaning one side was clean, and the other had a few patches in it.  You can see a patch just below the plans in this picture.  With the panels aligned, it was time to transfer the measurements from the plans to the panels.  Grid marks were made on the sides every 12 inches, then "tick" marks were made down from the edge.

I clamped a 4 foot rule for accuracy, and double checked each mark.  I placed drywall screws outside the lines of the panels into the work platform to keep everything aligned.

All the "tick" marks represent curves.  I drove small finishing nails into each mark, then clamped a long batten to them.  The batten will conform to a smooth curve. There are always small errors in measuring the marks from the plans.  So some nails are adjusted to match the curve of the batten, and then the line is drawn.

When I was satisfied with the lines, it was time to cut the parts out.  I bought a new blade for the saw, set the depth to just below the wood, and carefully cut the outside of the line.  The 2x6s below the panels allow for this.  After cutting, I finished up with the plane and sander to true up the cuts.

Here is where the "stitch" comes to  play.  I am working on the bottom panels, still atop one another.  Holes are drilled every foot or so along the edge that will become the centerline of the boat. Wire is place through the holes, and tightened.  The screwdriver allows a gap and prevents over-tightening. 

With a small fanfare, the panels are opened up and spread apart.  The curve at the front force the pieces up as it spreads out.  I placed short 1/4 inch bolts and washers here and there to maintain the gap between the panels, as the curves wanted to overlap each other.  

The side and end panels were stitched in place the same way.  The cross beam was screwed in place to maintain the proper shape through out construction.  I spent some time adjusting the bow piece after  this was taken to make a better fit.  Grandson Miles said "Papa, it looks like a boat!"  I guess I'm on the right track.

When I got the panels aligned to my satisfaction, I leveled and stabilized the boat with bracing from the platform.  Now came the Glue part of construction.  Clear packing tape was placed along the outside of each seam.  Epoxy is thickened to a peanut butter consistency and spread in the gaps between the wires and bolts.  Then it is spread to make a smooth radius.  Excess epoxy is cleaned up right away since it is easier to scrape up now before it sets.  After this batch has set, the wires and screws are removed, and the remaining gaps filled and smoothed.  The next step will be sanding, then covering the seams with fiberglass tape.