Randy's Boat Shop

The next step in building the Candlefish 13 is to fair the hull.  So we need a definition of what fair is: A fair curve  — A smooth curve in the body of a ship.  Boat are about curves and not straight lines.  Looking at the hull in three dimensions the curves need to flow smoothly.  One part of making the boat fair is how it was designed; the second is fairing the chimes so there are no discontinuities.  To aid in this the chimes and keel have been coated with lightweight fairing compound mixed with epoxy.  The upper chimes were previously taped so the fairing smooths out the the transition from plywood to the fiberglass.

Green epoxy is very nasty stuff so I will have to wait several days for the epoxy to cure before I can sand the hull.  To speed it up I may put the space heater under the hull.  There are tools that are used to fair the hull, namely long boards.  These are flexible and not-so-flexible boards that are about 18 long by 2-3/4 wide.  Sandpaper is attached to the board and the the hull is sanded first with the non-flexible one on all the mostly flat surfaces and then with the flexible on on the curves like at the bow.  When I am all done sanding I will wet the hull to see area that I missed and start over again adding more fairing compound, letting it cure and then sand it off again until the hull is fair or I give up.

I taped the upper chime yesterday and it looks very good even though the epoxy is still curing.  I used masking tape to mark off where I would apply epoxy and to limit runs.  My friend Darryl helped me make and roll the 4 inch wide fiberglass tape from the 50 inch wide roll of 6 oz. fiberglass cloth.  We also made 6 inch wide peel ply tape.  The first step was to prime 2 inches above and below the chime (the chime is where two strakes meet).  I also filled some small holes that I had missed earlier.  Then starting from the bow I unrolled the 4 inch fiberglass tape and pressed it into the neat epoxy in the primed area.  There was a little bit of fussing to the bow overlap correct and a minor crisis when I ended up short one fiberglass tape.  I changed out my latex gloves and cut another 4 inch tape so I could keep going.  Next, using an epoxy paint roller, I wetted out the fiberglass cloth with neat epoxy.  I was forced to use a 7 inch roller frame since I could not find my 2 or 3 inch frames.  A trip to Home Depot is in my future; a 3 inch frame would have been the perfect size for this job.   Once all the fiberglass cloth was wetted out I removed the masking tape and applied the 6 inch wide peel ply tape over the fiberglass cloth.  Starting from the bow and stern so I could meet in the middle I applied the peel ply and worked out any bubbles with a paper towel.  There is one section where the fiberglass cloth looks like it is epoxy starved so I will look into that before I cover the bottom with fiberglass cloth.

About half the hull has been tabbed. To tab the hull the area between the stiches is wetted with neat epoxy and allowed to soak in. The fillet material is mixed with epoxy to a very thick consistency so the fillet won’t run. A quart zip lock bag is filled with about 6 to 8 oz of the epoxy-fillet material, squeezed into a corner and the corner of the bag is snipped off. Similar to a cake decorator frosting bag, the epoxy-fillet material can be quickly applied to the seams without making a mess. The fillet material is then smoothed with a tongue depressor which make a nice 3/4 inch fillet tool. If you are wondering why I don’t have any photos of the epoxy process, it is because when I am using epoxy I have a Tyvek suit, gloves and a respirator on. Also epoxy is very sticky and I don’t want to get it on my camera.

Tab With Peel Ply Still Attached

The next step is to apply 2 inch square pieces of fiberglass cloth over the fillet. More neat epoxy is used to wet out the fiberglass until it is transparent. Finally a 3 inch square piece of peel ply is put over the fiberglass cloth, smoothed out with a dry chipping brush and blotted with a paper towel to soak up any excess epoxy. A chipping brush is cheapest paint brush available. They are known to lose their bristles with regular frequency. To prevent the bristles from coming out I put a bead of superglue at the ferrule.

Tab With Peel Ply Removed

I had left one of the tabs without peel ply to see if the peel ply actually worked. The peel ply leaves a smooth finish to the epoxy that will save me hours of sanding. Also I won’t have to remove the fiberglass tab when I tape the seams when I turn the board over to do the insides. I will now be using peel ply on all my seams.

Tab Without Using Peel Ply

Now that the stitching is finished and as I tab the hull, I am inspecting my work more closely.  The first photo shows the bow where there are several bad stitches that were not pulled tight against the plywood.  The two stitches closest to the bow are two good stitches which are pulled tight against the plywood.  There is a slight gap cause by not cutting the panels perfectly; fortunately the filleting material will easily fill it.  I found through practice that when I bend the wire into a large staple I need to make sure the width matches the holes drilled in the plywood.  The second photo shows the stitches from the outside of the hull.  A hole is drilled in each of the plywood panels about a 1/4 inch from the edge.  The wire staple is pushed though and working from the bow to the stern the wires are tightened by twisting to bring the hull in to shape.  

I have started to tab the hull which means that I am adding fillets between the wire stitches and applying a 2 inch square pieces of fiberglass cloth over the joint of the panel edges. The third photo shows completed tabs with peel ply which is added to smooth out the epoxy so there is a smooth finish.  The peel ply is easily pulled off taking the excess hardened epoxy with it.  By removing the excess epoxy this way I have greatly reduced the amount of sanding that I need to do.  Sanding epoxy is the bane of stitch and glue boat building.

Last Saturday I gave a plywood scarfing demonstration at RiversWest Small Craft Center (www.riverswest.org).

Plywood normally comes in 4’x8′ sheets or the metric equivalent of 1220mm x 2440mm.  In boat building, we often need longer sheets of plywood to work with and the most cost effective way to make plywood longer is to cut a scarf joint, usually in a 1 to 8 ratio.  For a 6mm (~1/4inch) thick plywood the scarf would be 48mm long or just under 2 inches.  To cut the scarfs for the Candlefish 13 I used the John Henry Scarfer which is a jig that bolts to a power planer; in this case a Makita 1902 3 1/4 inch wide planer.  The scarfer runs on long the edge of the support piece and a the work bench top and by adjusting the number of shims the angle of the cut is controlled.

I set the planner to cut only 1/32 inch so it took 5 passes to cut the scarf.  It takes longer to setup than to cut the plywood. 

Once all the scarfs are cut I then cleaned them up with my #6 joiner hand plane.  The next step is to epoxy the plywood sheets together.  When done properly the joint is just as strong and almost as flexible as the plywood.